(navigation image)
Home American Libraries | Canadian Libraries | Universal Library | Community Texts | Project Gutenberg | Children's Library | Biodiversity Heritage Library | Additional Collections
Search: Advanced Search
Anonymous User (login or join us)
Upload
See other formats

Full text of "USGS PP177 The Gold Hill Mining District, Utah (1935)"

UNITED STATES DEPARTMENT OF THE INTERIOR 
Harold h. Ickes, Secretary 

GEOLOGICAL SURVEY 
W. C. Mcndtmhall, Director 



Professional Paper 177 



THE GOLD HILL MINING DISTRICT 

UTAH 



BY 

T. B. NOLAN 




UNWED STATES 

GOVERNMENT PRINTING OFFICE 

WASHINGTON ; 19S5 



For sale by the Superintendent of Documents, Washington, D.C. --------- -------•-------_.--_ Prict $1.23 



CONTENTS 



Page 

Abstract vn 

Introduction 1 

Location and accessibility 1 

Geography 1 

Physical features 1 

Climate and vegetation 2 

Field work and acknowledgments 3 

Previous work 3 

Present work 4 

Geologic formations 4 

Cambrian system 4 

Prospect Mountain quartzite _ _ 4 

Cabin shale 6 

Busby quartzite 7 

Abercrombie formation 8 

Young Peak dolomite 10 

Trippe limestone 11 

Lamb dolomite 12 

Hicks formation 14 

Unconformity at top of Upper Cambrian 14 

Ordovician system - 15 

Chokecherry dolomite 15 

Unconformity at base of Upper Ordovician 16 

Fish Haven dolomite 16 

Unconformity at top of Upper Ordovician 17 

Silurian system 17 

Laketown dolomite 17 

Unconformity between Silurian and Devonian. 18 

Devonian system 18 

Sevy dolomite . 18 

Simonson dolomite 19 

Guilmette formation 20 

Unconformity at base of Carboniferous 21 

Origin of the pre-Carboniferous dolomitic formations. 22 

Correlation of pre-Carboniferous sedimentary rocks 

in eastern Nevada and western Utah 23 

Carboniferous system 23 

Madison limestone.. 24 

Woodman formation 27 

Ochre Mountain limestone 29 

Manning Canyon formation 31 

Mississippian-Pennsylvanian contact 33 

Oquirrh formation 33 

Gerster formation 39 

Correlation of the Carboniferous formations.. 41 

Lower Triassic limestones.. 42 

Unconformity at the base of the Eocene (?) 42 

Tertiary system 42 

WhiteSage formation 42 

Unconformity above White Sage formation 43 

Older igneous rocks 43 

General features 43 

Quartz monzonite 43 



Page 

Geologic formations — Continued. 
Tertiary system — Continued. 

Older igneous rocks — Continued. 

Porphyry dikes 46 

Aplite dikes 48 

Age of the older igneous rocks 48 

Pliocene(?) sediments 48 

Younger igneous rocks 49 

Distribution and relations — 49 

Petrography 49 

Biotite and hornblende andesites or 

latites 50 

Hypersthene-augite latite 50 

Trachyte 51 

Rhyolites 51 

Alkali basalt 52 

Pyroclastic rocks 52 

Alteration of the volcanic rocks 53 

Age of the volcanic rocks 53 

Gravel and clay 53 

Older gravel and clay 54 

Younger gravel and clay 54 

Lake Bonneville beds 54 

Geologic structure 55 

Structural cycles 55 

First cycle 55 

Second cycle 55 

Third cycle 56 

Fourth cycle 58 

Fifth cycle and faults related to the quartz 

monzonite intrusion 60 

Progressive variation in the character of defor- 
mation 60 

Late normal faulting and its relation to the present 

topography 61 

Age of the structural features 63 

Local descriptions 64 

Deep Creek Mountain block ,.„ 66 

Uiyabi Canyon block 69 

Ochre Mountain block 72 

Dutch Mountain block 78 

Northwestern block . 85 

Quartz monzonite block 88 

Igneous metamorphism 91 

Alteration of the sedimentary rocks 91 

Beery stallization 91 

Alteration to silicate minerals. . 92 

Alteration to jasperoids 93 

Dolomitization 94 

Alteration of the quartz monzonite 94 

Diopside-orthoclase alteration 94 

Sericitization and chloritization 95 

Silicification 95 

m 



CONTENTS 



Page 
Igneous metamorphism — Continued. 

Comparison of the alteration of the sedimentary 

rocks and the quartz monzonite 96 

Ore deposits 97 

Classification 97 

Pipelike deposits-. _ - 97 

Veins with silieate minerals in the gangue 99 

Veins containing chiefly quartz and metallic sul- 
phides 101 

Veins with carbonate or sulphate minerals in the 

gangue 101 

Arsenic replacement bodies 102 

Copper-lead-silver replacement bodies 103 

Superficial alteration of the ores -.._-..__ 104 

Relation of the water table to superficial 

alteration 104 

Relation of the physical and chemical char- 
acter of the ores to superficial alteration 105 

Areal relations of the ore deposits - 107 

Influence of zoning on the distribution of the 

ore deposits 107 

Influence of the Ochre Mountain thrust on the 

distribution of the ore deposits . _ _ _ ___ 108 

Genesis of the ore deposits 108 

Future of the district 109 

Tungsten-bearing pipes and veins 109 

Veins with silicate minerals in the gangue 109 

Quartz-sulphide veins 110 

Carbonate-sulphate veins 110 

Arsenic replacement bodies 110 

, Copper-lead-silver replacement bodies 110 

Summary 110 

Minerals of the metamorphosed rocks and the ore 

deposits 110 

Native elements 110 

Sulphides, selenides, tellurides, arsenides, and anti- 

monides 111 

Sulphosalts 111 

Haloids 112 

Oxides - 112 

Carbonates 112 

Silicates 113 

Titanosilicates 116 

Phosphates, arsenates, vanadates, and antimonates . 116 

Sulphates, chromates, and tellurates 117 

Tungstates and molybdates 117 

Mines and prospects 118 

Clifton district - - 118 

History of mining and production 118 

Mines and prospects 119 

Pipelike deposits 119 

Reaper 119 

Yellow Hammer 122 

Doctor 122 

Centennial and Enterprise 122 

Veins with silicate minerals in the gangue- 123 

Frankie 123 

Calaveras 124 

Pole Star Copper Co 124 

Copperopolis (Ida Lull) 125 

Napoleon Mining Co 125 

Gold Bond 125 

Copper Bloom 127 

Victory No. 1 127 

Minnehaha 127 

Ozark. ... 128 

Copper Hill._ 128 

Alvarado 128 



1 
Mines and prospects — Continued. 
Clifton district — Continued. 

Mines and prospects — Continued. 

Veins with silicate minerals in the gangue— 
Continued. 

Cane Springs.... ._ 1 

Midas 1 

Bonnemort ., 1- 

■ Rube I! 

Wilson Consolidated 15 

Veins containing chiefly quarts; and metal- 
lic sulphides 14 

Lucy L 14' 

Boston _ . 14; 

New York 145 

Silver & Gold Mining Co 14S 

Mascot 143 

Monte del Rey 144 

Fortuna 144 

Bonanza 344 

Cyclone 144 

Success 145 

Spotted Fawn............. 145 

Western Utah Extension Copper Co— 146 

Climax 147 

Southern Confederate.. 147 

Red Jacket 148 

Copper Queen Midland Mining Co — 148 

Cash Boy (Mammoth) 148 

New Baltimore 149 

Bird -. --.- 140 

Shay 149 

Gold Hill Standard Mining Co 149 

Gold Belt 149 

Pay Rock 150 

Undine 150 

Rea - 180 

Christmas Mining Co 151 

Veins with carbonate or sulphate minerals 

in the gangue 151 

Troy 161 

Immense 151 

Arsenic replacement bodies 151 

Gold Hill mine of Western Utah 

Copper Co 151 

Gold Hill mine of United States Smelt- 
ing, Refining & Mining Co 156 

Oregon , 162 

Herat 162 

Copper-lead-silver replacement bodies 162 

Monocco 162 

Silver King.. 163 

Mohawk 163 

Walla Walla 164 

Garrison Monster Mining Co 164 

Consolidated claim 164 

New Year claim 166 

Uncle Sam claim 166 

Evans 166 

Willow Springs district 167 

History and production. 167 

Prospects. 167 

Dewey 167 

Sunday 167 

Lead-Carbonate 167 

Silver 168 

Other prospects 168 

Index 169 



ILLUSTRATIONS 



Fane 

Plate 1. Geologic map and sections of the Gold Hill 

quadrangle, Utah In pocket 

2. Geologic map and sections of Gold Hill and 

vicinity In pocket 

3. Fault map of the Gold Hill quadrangle-- In pocket 

4. A, Bonneville beach and spit, southeast of 

Dutch Mountain; B, Dutch Mountain from 
the southeast; C, Clifton Flat from the 
sout hwest 8 

5. A, Mottled Young Peak dolomite; B, Lam- 

inated Trippe limestone; C, Pisolitic dol- 
omite from the Hicks formation; D, " Mar- 
ble cake" dolomite near the base of the 
Laketown dolomite; E, Laminated Simon- 
son dolomite; P, Chert-pebble conglom- 
erate with oolitic matrix from Oquirrh 
formation 8 

6. A, East slope of Ochre Mountain; B, Dissec- 

tion on west slope of Ochre Mountain; C, 

D, Dissected postmature erosion surface-.- 64 

7. A, Crumpling beneath nearly fiat fault on the 

west side of Ochre Mountain; B, Plunging 
minor anticline in the Manning Canyon 
formation; C, Variable dip of fault between 
the Madison limestone and the Woodman 
formation iu Accident Canyon; D, Minor 
thrust in the Woodman formation north of 
the Garrison Monster new camp - 64 

8. A, Wollastonite replacing garnet in metamor- 

phosed Ochre Mountain limestone; B, 
Jasperoid from the U.S. mine, with inclu- 
sions of opal in quartz; C, Wollastonite 
replaced by spadaite; D, Preservation of 
calcite cleavage lines in jasperoid 96 

9. A, Elongated quartz grains in silicified quartz 

monzonite; B, Successive replacements in 
a specimen from the tungsten-bearing pipe 
on the Reaper claim; C, Apatite and molyb- 
denite in amphibole 96 

10. A, Replacement of specularite by danburite 

and fluorite, Gold Bond claim; B, Replace- 
ment of tourmaline by specularite, Gold 
Bond claim; C, Quartz carbonate vein, 7,000 
feet east of Clifton; D, Quartz and ortho- 
clase replacing calcite, Wilson Consolidated 
mine; E, Polished section showing arseno- 
pyrite fragments cemented by other sul- 
phides and quartz, Cyclone mine 104 

11. A, Bladed arsenopyrite, Tunnel level, U.S. 

mine; B, Polished section showing brec- 
cia ted arsenopyrite veined by pyrite, quartz, 
sphalerite, and galena, U.S. mine; C, Pol- 
ished section showing replacement of arsen- 
opyrite fragments by quarts and sericite, 
Western Utah mine; D, Thin section show- 
ing barite replacing sulphides, Garrison 
Monster mine „ ,--,. 104 



Page 

Plate 12. A, Dense white scorodite with associated 
crystalline green scorodite, Western Utah 
mine; B, Brown scorodite, Western Utah 
mine; C, Crystalline scorodite forming 
from metacolloid 104 

13. Plan of workings, Lucy L mine 140 

14. Block diagram of Gold Hill mine of Western 

Utah Copper Co 152 

15. Level map of Gold Hill mine of Western Utah 

Copper Co 152 

Fiotjbb 1. Index map of Utah showing location of 

Gold Hill quadrangle 1 

2. Sections of the Young Peak dolomite, show- 

ing the interfingering northward of lime- 
stone 10 

3. Correlation of pre-Carboniferous rocks in 

eastern Nevada and western Utah from 

west to east 24 

4. Correlation of pre-Carboniferous rocks in 

eastern Nevada and western Utah from 
north to south 25 

5. Relations between the three facies of the Car- 

boniferous rocks 26 

6. Correlation of Carboniferous formation in an 

east-west belt from Eureka, Nev., to the 
Cottonwood-Park City area, Utah 40 

7. Correlation of Carboniferous formations in 

a northeast-southwest belt from Pioche, 
Nev., to the Randolph quadrangle, Utah. 41 

8. Block diagram showing the generalized struc- 

ture along the Garrison Monster trans- 
verse fault 60 

9. Crumpling of Guilmette formation north of 

Lincoln Highway 70 

10. Sketch map showing folding of a bed in the 

Oquirrh formation on the northwest side 

of Dutch Mountain 85 

11. Generalized section showing supposed orig- 

inal relations between the Twin Peaks re- 
etunbent anticline and the Dutch Moun- 
tain thrust 86 

12. Strikes and dips of various types of fractures 

in the quartz monzonite 90 

13. Flan of main workings, Reaper claim 120 

14. Prospect pits and mineralization adjacent to 

Reaper open cut 121 

15. Plan of adit tunnel, Copperopolis group 126 

1 6. Plan of Alvarado mine workings 129 

17. Geologic cross section through Alvarado 

shaft - 129 

18. Stope projection on plane through shaft, Al- 

varado mine 130 

19. Plan of Cane Springs mine workings 132 

20. Composite section through Cane Springs 

mine 133 

21. Stope projection, Cane Springs mine 133 

22. Plan of tunnel level, Midas mine 134 

23. Plan of mine workings, Rube mine 137 

V 



VI 



ILLUSTBATIONS 



Page 

Figube 24. Longitudinal section through Rube mine 137 

25. Sketch plan and section of W lson Consoli- 

dated mine 139 

26. Cross section of Lucy L mine 141 

27. Plan of tunnel and surface workings on north 

side of guloh, Spotted Fawn mine 145 



Pago 
Figvrb28. Plan of tunnel level, Western Utah Exten- 
sion Copper Co 146 

29. Plan of workings, U.S. mine 157 

30. Section through adit tunnel, U.S. mine 159 

31. Mine workings on Consolidated claim, Gar- 

rison Monster mine 165 



ABSTEACT 



Introduction. — The Gold Hill quadrangle is in west central 
Utah and is limited by parallels 40° and 40°15'^and meridians 
113°45' and 114°. This area includes the north end of the 
Deep Creek Mountains, one of the ranges in the Great Basin. 
The climate of the region, like that of the major province, is 
relatively arid, the average annual rainfall being about 13 
inches. 

Geologic formations. — The following stratigraphic sequence is 
described: 



System 


Series 


Formation 


Thickness 
(feet) 


Quaternary and 
Tertiary. 


f Recent to Pliocene? 

Unconformity. 


Gravel and clay 

Gravel and marl 

White Sage formation. _. 


^uoo 


Unconformity. 
(Eocene (?) 


^R» 


Triassio 


Unconformity. 

Lower Triassic 

("Permian 

Permian and Pennsyl- 

vanian. 
1 Pennsyl vanian (Potts- 

ville) and Mississip- 

pian (?). 


50 


Carboniferous 


Gerster formation 

Oquirrh formation 

Manning Canyon for- 
mation. 

(Ochre Mountain lime- 
J stone. 

(Woodman formation 

(Madison limestone . -- 

(Guilmette formation 

<Simonson dolomite 


600 
±8,000 

±500 
±4,600 


Devonian 


Unconformity. 
Middle Devonian. ... 
Unconformity. 


±1,500 
0-400 

900-1,200 

1,000 

450 




Laketown dolomite 

Fish Haven dolomite 

Chokecherry dolomite. . 


±1,000 


Ordovician . _. 


[Upper Ordovician 

^Unconformity. 

(Lower Ordovician. 

Unconformity. • 
fUpper Cambrian.. 

\Middle Cambrian 

Lower Cambrian 


280 
600-1, 200 






1,050 


Cambrian 


(Trippe limestone— 

I Young Peak dolomite. -- 
(Abercrombie formation . 
(Busby quartzite 


725 

0-600 

3,700 

450 

510 




i Prospect Mountain 
( quartzite. 


±3,000-4,750 



The considerable thickneis of dolomites found in the pre- 
Carboniferous sequence is noted, and it is suggested that much 
of the dolomite in the area has been formed by the alteration 
of an original limestone shortly after its deposition in shallow 
waters in which little or no additional deposition was possible. 

Three facies of Carboniferous rocks were recognized, which 
are separated from each other by two major thrust faults. The 
three facies differ from one another in lithology and in the 
thickness of certain of the formations. 

An intrusive stock of quartz monzonite is of early Tertiary 
age. Variations in composition ranging from that of granite to 
one approaching diorite can be recognized, but no sharp 
boundary was found between these different phases. The 
boundaries of the stock in several places show a dependence 
upon preexistent faults, but the intrusion itself appears to 
have caused essentially no deformation in the invaded rocks. 
The limitation of the stock to the region between two major 
transverse faults that also limit one of the major overthrusts may 
be due to the more thorough shattering of the area thus enclosed 
and the consequent greater ease in the emplacement of the 
magma. 



Numerous porphyry dikes associated with the intrusion show 
an almost complete . gradation between granite porphyries in 
which the groundmass has an allotriomorphie texture to basalt 
dikes in which the groundmass is characterized by an inter- 
granular texture. Aplite dikes in the quartz monzonite are 
younger than the porphyry dikes. 

A younger series of igneous rocks is composed almost entirely, 
of flows and pyroclastic rocks. The bulk of the material is 
andesitic in appearance, but chemical analysis of typical 
specimens proved them to be of latitic or trachytic composition. 
One flow, partly glassy, contained 8.90 percent of KjO, although 
no potash-bearing feldspar was recognized under the micro- 
scope. Small outcrops of basaltic-appearing rocks also proved 
to be notably high in potash. These rocks are thought to be of 
late Pliocene age. 

Geologic structure. — The structural history of the quadrangle 
is characterized by at least four and possibly five cycles of 
folding and faulting, each cycle composed of an initial stage in 
which compressive, forces were active and a final stage in which 
normal faulting was dominant. 

The structural features of the first cycle are naturally obscure, 
but there appears to have been an early stage of relatively 
minor thrusting, succeeded by rather intense normal faulting. 
During the first stage of the second cycle numerous folds, of 
which at least one was recumbent, and minor thrusts were 
formed, apparently under a moderately thick cover. The 
second stage of the second cycle is represented by a small number 
of normal faults, the throws along which are generally several 
thousands of feet. The third cycle was initiated, after a pro- 
longed period of erosion, by a long phase of thrusting and 
transverse faulting, which must have, occurred under a very 
light load. One of the two major thrusts of this stage was 
originally limited between two transverse faults, and associated 
with both of the thrusts are relatively narrow thrust sheets. 
Considerable evidence is available that these thrusts, in the 
regions now exposed, moved over the then existing surface. 
The normal faulting at the end of this cycle was relatively 
slight, and much of It appears to have taken place along pre- 
existent faults. The early stage of the fourth cycle was charac- 
terized by numerous transverse faults with an almost complete 
lack of folding and thrust faulting. Unusually complex minor 
structural features are associated with some of the larger trans- 
verse faults. Normal faults that should belong to the final 
stage of this cycle appear to be almost completely lacking. 
These four cycles antedate the intrusion of the quartz monzo- 
nite, and a possible fifth cycle is indicated by minor thrust 
faults that cut the intrusive. 

It is suggested that the successive dominance of folding, 
thrusting, and transverse faulting in the initial stages of 
progressively younger cycles is genetically connected with the 
fact that these structural processes occurred under a constantly 
decreasing load. If it may be assumed that normal faults are 
the result of relaxational movements after excess compression, 
the apparent decrease in the importance of normal faulting 
throughout the period of deformation may be attributed to the 
progressively greater resistance of the rocks within the quad- 
rangle as a result of the successive periods of compression. 

TO 



vm 



ABSTRACT 



Recent normal faults displace an old postmature erosion 
surface that bevels all the older structural features. Evidence 
is presented that these faults are not all strictly contempora- 
neous, that the faulting tended to utilize older fault lines, and 
that both walla of individual faults have been active. 

The structural features of the third cycle appear to be more 
or less contemporaneous with the deposition of the Eocene 
White Sage formation. The two previous cycles are consider- 
ably older, because a period of erosion must have intervened 
between them and the third cycle, and a Cretaceous age is 
therefore suggested for them. The relatively recent normal 
faults are probably of late Pliocene age. 

Igneous metamorphism. — The sedimentary rocks near the 
quartz monzonite have been more or less affected by the 
intrusion. Four kinds of alteration were recognized — one 
involving reerystallization, one in which silicate minerals were 
introduced, one in which silicification occurred, and one in which 
limestones were dolomitized. These represent successive stages 
in the alteration. Similarly, three major stages of alteration 
were recognized as having occurred in the quartz monzonite, 
after its consolidation — a diopside-orthoclase alteration, seri- 
citization and chloritization, and silicification — each succes- 
sively younger. The obvious similarities between the meta- 
morphism of the sedimentary and intrusive rocks point to a 
common origin, at a stage that must have followed the consoli- 
dation of the portions of the intrusive now exposed. Differ- 
ences in the metamorphism are explained chiefly by the 
different physical and chemical conditions existing in the two 
kinds of rock at the time of the alteration. 

Ore deposits. — The ore deposits show a very considerable 
range in character. For purposes of description the vemlike 
deposits have been divided into pipes, characterized by tungsten 
minerals in a pegmatitic gangue of hornblende, orthoclase, and 
other silicates; veins with silicate minerals in the gangue, in 
which copper and gold are the valuable constituents and in 
which the content of the silicate minerals in the gangue may 
range from almost 100 percent to nearly lero; veins containing 
chiefly quartz and metallic sulphides, in which arsenic, lead, 
and silver are the chief metals found; and veins with carbonate 
or sulphate minerals in the gangue, which are at present of 
little or no economic importance. There are no very sharp 
boundaries between the successive members of this series of 
deposits, and veins that show gradations between two members 



of the series are abundant. In regions underlain by limestone, 
replacement bodies of arsenic ore and copper-lead-silver ore 
are found; and two of the arsenic ore bodies are ■ unusually 
large. Surficial alteration of the ore bodies has been relatively 
slight in the ore bodies with silicate minerals in the gangue, 
but is widespread in the other deposits. The arsenic replace- 
ment ore bodies have been particularly affected, the process 
resulting in the conversion of the primary arsenopyrite to 
scorodite. The bottom of the zone of complete alteration is 
considerably above the present water table, corroborating the 
other evidence t)f relatively recent faulting. 

It is suggested that the lack of zonal distribution of the ore 
bodies is chiefly the result of recurrent fracturing in the intru- 
sive throughout the period of ore deposition. A further factor 
that has inhibited the development of a zonal pattern in the 
ore deposits is the presence of one of the major overthrusts 
within the mineralized area. The rocks above the thrust are 
essentially barren, and it is thought that this is due to the 
inability of the ore-bearing fractures to penetrate the wide 
crushed zone that marks the fault. 

The several kinds of altered rock and of ore deposits and the 
relations that are exhibited between them lead to the suggestion 
that the fluids that cause igneous metamorphism and ore depo- 
sitfgb pass through a long series of changes that are comparable 
in Hegree to the changes produced by differentiation in many 
large intrusive masses. In this district many of these steps 
have been preserved by the recurrent fracturing to which the 
quartz monzonite has been subjected, and to this factor is 
ascribed the disappointingly small size of so many of the ore 
bodies. Only the gold lodes and arsenic replacement bodies 
are thought to have any great future Importance. 

Brief notes are given on the 100 minerals recognized in the 
metamorphosed rocks and in the ore bodies. 

Mines and prospects. — The Clifton mining district, which lies 
within the quadrangle, is one of the oldest mining districts of 
Utah, having been organized in 1869. The value of its output 
of gold, silver, copper, lead, and zinc from 1901 to 1927, is more 
than $2,000,000, and in addition it' is estimated that about 
9,000 tons of metallic arsenic was contained in the ores shipped 
from the district during the period from 1920 to 1925. The 
northern part of the Willow Springs district is also included 
within the quadrangle, but the production from this source is 
almost negligible. 



THE GOLD HILL MINING DISTRICT, UTAH 



By T. B. Nolan 



INTBODUCTION 

LOCATION AND ACCESSIBILITY 

The Gold Hill quadrangle, in western Utah (fig. 1), 
is an area of 228 square miles enclosed between parallels 
40° and 40°15' and meridians 113°45' and 114°. The 
area has weekly train service over the Deep Creek 



em terminus of the branch line. The Lincoln High- 
way passes through both Gold Hill and Ibapah, a 
small agricultural community in the southwest cor- 
ner of the quadrangle. This highway, however, is 
relatively little used and in many places is in rather 
poor condition. About 40 miles of equally poor 
highway connects both towns with the Victory 
Highway at Wendover. 




GEOGRAPHY 



PHYSICAL FEATURES 



Figure 1.— Index map of Utah showing location of Gold Hill quadrangle and other areas covered by pub- 
lished Geological Survey or other reports, 1, Gold Hill quadrangle; 2, Fairfield and Stockton quad- 
rangles (Prof. Paper 173); 3, Bingham district (Prof. Paper 38); 4, Park City district (Prof. Paper 77); 
5, Cottonwood district (Bull. 6205; 6, Bandolph quadrangle (Am. Jour. Sci., 4th ser., vol. 36, 
pp. 406-416, 1913); 7, Tintie district (Prof. Paper 107); 8, San Francisco district (Prof. Paper 80); 9, 
Iron Springs district (Bull. 338). 

Railroad to Wendover, a division point on the West- 
ern Pacific Railroad. Gold Hill, the principal town in. 
the area, with a population of about 50, is the south- 



The quadrangle includes the north 
end of the Deep Creek Mountains, one 
of the nearly north-south ranges that are 
common in the Great Basin. On the 
east and north the mountain area is 
separated by gravel slopes from the flat 
plain of the Great Salt Lake Desert, 
and on the west it is bounded by Deep 
Creek Valley and groups of irregular 
low hills. 

South of the southern edge of the 
quadrangle the Deep Creek Mountains 
have remarkably straight escarpments 
both on the east and the west. These 
persist for about 3 miles north of the 
quadrangle boundary. The distance 
between the two escarpments in this 
region is about 4 miles, and the area thus 
enclosed will be referred to in this report 
as the Deep Creek Mountains. 

The eastern escarpment becomes less 
distinct to the north and in the latitude 
of Blood Mountain disappears entirely. 
The western escarpment is more per- 
sistent and forms the western limit of 
the mountain region for nearly 12 miles 
within the quadrangle. To the north 
tlris escarpment forms the western 
border of a nearly rectangular elevated 
block known as Ochre Mountain, which 
is separated from the Deep Creek 
Mountains on the south by a west- 
ward-draining open valley through 
which the Lincoln Highway passes and by the basin- 
like Clifton Flat, which drains to the southeast 
through Overland Canyon (pi. 4, C). 



GOLD HILL MINING DISTBICT, UTAH 



Overland Canyon may be taken as the boundary 
between the Deep Creek Mountains and the well- 
dissected country to the north, which has been called 
the Clifton Hills. This region,. whose highest summit 
is Montezuma Peak, lies east of Clifton Flat and is 
limited on the east by a poorly defined but distinctly 
linear escarpment that is less than a mile west of the 
eastern border of the quadrangle. East of the escarp- 
ment gravel-covered slopes lead down to the Great 
Salt Lake Desert. To the north the Clifton Hills 
merge westward with the Ochre Mountain mass and 
extend eastward beyond the escarpment in a series of 
low hills to the edge of the desert. 

At about the latitude of the town of Gold Hill the 
Clifton Hills by a gradual decrease in altitude pass 
northward into a wide belt of low-lying country which 
drains to the east. Farther north lies the rugged mass 
of Dutch Mountain (pi. 4, B), which rises abruptly 
from the Great Salt Lake Desert, in the northeast cor- 
ner of the quadrangle. In this region also are some of 
the best exposures of the shore phenomena of the 
ancient Lake Bonneville (pi. 4, A) . 

To the west Dutch Mountain decreases in altitude 
through a series of rude steps and merges with a hilly 
tract of country that lies north and northwest of Ochre 
Mountain. The escarpment that separates Ochre 
Mountain and the Deep Creek Mountains from Deep 
Creek Valley cannot be recognized in this region ,which 
therefore marks the northern limit of the open and 
locally flat-floored portion of Deep Creek Valley. 

The only perennial stream within the area is the 
southern part of Deep Creek, which rises in the high 
mountains south of the quadrangle and flows north- 
ward through Deep Creek Valley along a course that 
closely parallels the 114th meridian. Owing to the 
demands of irrigation the stream is intermittent north 
of the Sheridan ranch. The ranches north of the Sheri- 
dan obtain water either from dug wells or from artesian 
wells. Several good-sized springs along the east side 
of Deep Creek Yalley provide water for stock and for 
the irrigation of a small area. The remainder of the 
quadrangle is very poorly supplied with water, the 
small quantities available being obtained from a few 
shallow wells and numerous small springs. The largest 
springs are the Ochre Springs, about 2 miles southwest 
of the town of Gold Hill, which furnish water for both 
the town and the mining operations. The water from 
these springs, like that from the other springs and wells 
in the mineralized area, has a high percentage of 
dissolved salts and is rather unpalatable. 

CLIMATI AND VEGETATION 

The Gold Hill quadrangle lies well within the region 
of interior drainage that includes western Utah and 
most of Nevada, and, like the rest of that province, 



it has an arid climate. Pronounced differences in 
temperature between night and day are characteristic, 
but the dryness of the air mitigates the high tempera- 
tures that often prevail during the summer afternoons. 

The annual precipitation averages somewhat more 
than 12 inches, about half of which falls in the 4 
months from February to May. The rainfall of the 
summer and early fall is commonly in the form of 
severe thunderstorms or cloudbursts. Snowstorms 
may be expected from October to May. 

The following tables present climatic data for 
Ibapah, in the southwest corner of the quadrangle, 
furnished by the United States Weather Bureau. 
The conditions at the town of Gold Hill are similar, 
except that the extremes of temperature are somewhat 
less pronounced. 

Monthly and annual mean temperature at Ibapah, Utah (° F.) 



Year 



1903-18.. 

1919 

1920 

1921 

1922 

1923 

1924 

1925 

1926 

1927 

1928 

1929 



Jan. 



Feb. 



24 7 


27.9 


27.7 


30.6 


24. 2 


31.8 


29. 2 


33.2 


15.6 


25. 1 


31.0 


16.4 


19. 7 


36.8 


25.4 


36.3 


23.8 


34.4 


27.4 


32.8 


24.0 


30.0 


22.9 


25.9 



Mat. 


Apr. 


May 


35. 6 


44.7 


48.5 


36. 1 


45.8 


56.2 


33. 6 


38.6 


50.8 


40. 5 


40.3 


54. 1 


32.4 


38.6 


50.8 


31.8 


40.4 


51. 2 


31.6 


44.6 


50.4 


40.2 


45.8 


56. 3 


39.0 


49.7 


54.2 


38.4 


43. 3 


51.5 


42. 5 


44. 2 


56.9 


38.6 


46.0 


52.6 



June 



56.7 
61.2 
58.4 
61. 2 
63.8 
54.8 
62.4 
60.6 
64.6 
62.0 
60.4 
57.7 



Year 



July 



1903-18 

1919 

1920 

1921 

1922 

1923 

1924 

1925 

1926 

1927.. 

1928. 

1929 



65. 
70. 
68. 
68. 
68. 
70. 
68. 
71. 
68. 
70. 
69. 
71. 



Aug. 



65.9 
69.0 

65. 6 
66.3 
67.4 
64.9 
65.3 
C) 

68.0 
65.3 
67.2 
70.5 



Sept. 



56. 
59 

58. 
54. 
60. 
59. 
56. 
56, 
54. 
56. 
59. 
60, 



Oct, 



NO¥. 



Dec. : Annual 



44,7 
37. 7 
43.5 
51.0 
47.6 
43.4 
46.0 
46.4 
47.2 
48.6 
49.8 
53.0 



34. 5 
32.5 
33.2 
39.4 
31.0 
36.9 
34.9 
35.8 
41.4 
43.5 
37.0 
35.8 



24.4 
20.2 
24.6 
31.0 
29.0 
21.2 
20.9 
29.8 
24.6 
22.3 
18.9 
37.4 



44.2 
45.6 
44 2 
47.4 
44.2 
43.5 
44.8 



47.5 
46.8 
46.7 

47.7 



■ No record. 
Monthly and annual precipitation at Ibapah, Utah (inches) 



Year 



1903-18... 

1919 

1920 

1921 

1922 

1923 

1924. 

1925 

1926 

1927 

1928 

1929 



Jan. 



1.04 

.00 
.82 
.50 
1. 16 
1.03 
.09 
.28 
.89 
.56 
.65 
.59 



Feb. 



1.33 

1.91 

.58 

. 40 

1. 46 

.50 

. 12 

. 48 

1.24 

1.01 

1.52 

.77 



Mar. 


Apr. 


May 


1.31 


0.89 


1.98 


1.46 


1.07 


.26 


2. 66 


2.74 


3. 20 


.91 


3.51 


3.51 


1.01 


2.32 


.76 


.67 


1.86 


2. 12 


1.35 


1.68 


.29 


.95 


.96 


1.08 


.86 


.68 


.83 


1.61 


2. 19 


1.09 


3. 14 


1. 10 


1.40 


1. 10 


2.31 


.70 



0.97 
.00 
.40 

.24 
.23 

. 74 

Trace 

2.63 

.70 
1.02 
2.84 

.95 



GOLD HILL MINING DISTBICT, UTAH 



Monthly and annual precipalion at Ibapah, Utah (inches) — 
Continued. 



Year 



1903-18 

1919 

1920 

1921 

1922 

1923 

1924 

1925 

1926 

1927 

1928 

1929 



July 


Aug. 


Sept. 


Oct. 


Nov. 


Dec. 


0.91 


0.86 


0.69 


0.96 


0.67 


0.66 


. 14 


.66 


1.02 


1.21 


1.04 


.34 


1.79 


1. 37 


.88 


2.04 


.65 


. 74 


.78 


2.69 


.37 


.32 


.25 


1.50 


.93 


3.00 


. 00 


.67 


1.71 


.99 


.84 


.83 


1.83 


2.21 


.50 


1.40 


.34 


.69 


.52 


1.32 


.80 


1.24 


1. 45 


.72 


.94 


.66 


.67 


. 11 


2.03 


1.33 


. 14 


.33 


1.55 


1.45 


.36 


.67 


1. 14 


.40 


1.54 


.89 


.66 


.25 


.00 


1. 54 


.60 


1.38 


. 10 


2. 15 


1. 45 


.00 


.00 


.27 



12.27 
9. 11 
17.87 
14 98 
14. 24 
14.53 
8.44 
10. 93 
12.03 
12.48 
15.08 
10.39 



Miscellaneous climatic data for Ibapah, Utah, 1985—89 



Year 


Highest temperature 


lowest temperature 


°F. 


Date 


•r. 


Date 


1925 

1926 

1927 

1928 _ _ _ 


104 

99 

98 

100 

102 


July 14 
June 26 
July 19 
July 27 
July 25 


-2 
-16 
-20 
-19 

-20 


Jan. 7 

Dec. 27 
Jan, 22 
Dec. 22 


1929 


Jan, 24 





Snowfall 




Number of days 


Year 






1 With 0.01 






Clear 


Partly 
cloudy 


rinnrtv ■ Inch °f 
Cloud > ; p reci p ita . 












tion 


1925., 


24. 4 


178 


138 


49 


74 


1926 


51.2 


185 


128 


50 


59 


1927., 


54.2 


160 


155 


50 


59 


1928. 


70.0 


181 


147 


38 


60 


1929... 


35.5 


192 


128 


45 


46 



The higher portions of the Deep Creek Kange and 
small areas near the summits of Ochre Mountain and 
Dutch Mountain support a fairly heavy growth of 
yellow pine, small quantities of which are cut for local 
use. The lower slopes of these higher tracts have a 
sparse covering of juniper and piflon trees, few of 
which reach a height of 15 feet. On the lower hills 
and on the gravel slopes surrounding them these 
stunted trees give way to the group of shrubs char- 
acterized by the sagebrush, and the irregular and 
scattered distribution of these plants provides the 
"spotty" appearance that is so characteristic of the 
lower altitudes of this portion of the Great Basin. 

The floor of Deep Creek Valley is cultivated in 
several places where water for irrigation is available, 
and the green fields provide a striking contrast to 
the more somber coloring of the surrounding slopes. 
The floor of the Great Salt Lake Desert in the north- 
east corner of the quadrangle, on the other hand, is 
almost completely barren of vegetation. 



FIELD WOEK AND ACKNOWLEDGMENTS 
PREVIOUS WORE 

The first published record of exploration within the 
quadrangle is found in the report of Lt. E. G. Beck- 
with. 1 His party, after crossing the Great Salt Lake 
Desert, camped at what is now known as Bedding 
Springs, just beyond the southeast corner of the area. 
His report suggests that there had been no previous 
travel through this part of the country, for the presence 
of Overland Canyon, which was later in general use, 
was unknown either to him or to his Indian guides. 
He discovered the pass through the canyon, however 
by following the crest line of the range northward 
and noted the presence of "metamorphie [quartzite?] 
shale, and limestone," 

By 1866 much of the travel between San Francisco 
and Salt Lake City had become concentrated on the 
overland stage route that passed through Redding 
Springs, Overland Canyon (then known as Uiyabi 
Pass), and Deep Creek, where a settlement had been 
established. 2 Ruins of the old corrals may still be 
seen at Ibapah and south of Clifton. The first trans- 
continental telegraph line also followed this route. 

The geologists of the Wheeler and Fortieth Parallel 
Surveys followed the overland route, and reports of 
both contain notes on the general geology. 3 Neither 
recognized the intrusive character of the granitic rocks, 
considering them the Archean basement upon which 
the sediments were deposited. 

Gilbert visited the area again in the course of his 
field work on Lake Bonneville and recorded post- 
Bonneville disturbances on the east side of the range. 4 

In 1892 Blake 5 noted the intrusive character of the 
granitic rock and the attendant contact metamorphism. 
In the same year Kemp B described several rocks from 
the region, one of them an andalusite hornfels from a 
point near the Cane Springs mine. 

Kemp visited the region himself in 1908 and later 
published his observations in a joint paper with 
Billhigsley, 7 who had studied the ore deposits in 1913. 
In 1912 Butler 8 made a rapid reconnaissance through 
the district. 



i Beckwitb, B. O,, U.S. Pacific R.R, Kxpl. Kept.: 33d Cong., 1st sew., H.Ex.Doc. 
129, vol. 18, pt. 2, p. '24, 1855. 

'Browns, J. R., Mineral resources of the States and Territories west of the Rocky 
Mountains for 1866, p. 267, 1887. 

•Gilbert, G. K., U.S. Geog. and Qeol. Surveys W. 100th Mer. Rept., vol. 3, 
pp. 30, 123, 182, 1875. Hague, Arnold, and Emmons, S. T., U.S. Qeol. Expl. 40th 
Par. Rept., vol. 2, pp. 472-476. 1877. 

* Gilbert, G. K„ Lake Bonneville: U.S. Geo!. Survey Mon. 1, p. 353, 1890. 

1 Blake, W. P., Age of the limestone strata of Deep Creek, Utah, and the occur- 
rence of gold in the crystalline portions of- the formation: Am. Geologist, vol. 9, 
pp. 47-48, 1892; Eng. and Min. Jour., vol. 63, p. 253, 1882. 

• Kemp, J. F„ Notes on several rocks coUectei by E. E. Olcott, E, M„ near Gold 
Hill, Tooele County, Utah; New York Acad. Sei. Trans., vol. 11, pp. 127-128, 1802. 

» Kemp, J. 3\, and Billingstey, Paul, Notes on Gold Hill and vicinity, Tooele 
County, western Utah: Boon. Geology, vol. IS, pp. 247-274, 1918. 

» Butler, B. S., and others. The ore deposits of Utah: U.S. Geol. Survey Prof. 
Paper 111, pp. 469-485, 1920, 



GOLD HILL MINING DISTEICT, UTAH 



Since the completion of the railroad in 1917 several 
short articles have appeared, dealing mainly with the 
mines and prospects, 

PRESENT WORK 

The reconnaissance work of B. S. Butler in 1912 
showed that it was desirable to make a more detailed 
study of the Clifton district, but it was not until 1924 
that conditions permitted the initiation of the work by 
the Geological Survey. Topographic mapping was 
started in that year by a party under K. T. Evans and 
was completed the following year by W. J. Lloyd and 
E. S. Riekard. The general excellence of the topo- 
graphic map produced greatly facilitated the geologic 
field work, which was started by the writer July 12, 

1925. Work continued that season through September 
28 but was several times interrupted by another 
assignment. The field work was resumed April 26, 

1926, and continued until November 6. During most 
of this season Frank A. Melton also participated in 
the field work. Dr. Melton is responsible for the 
greater part of the mapping of the southern and 
western flanks of Ochre Mountain and also collaborated 
in the mapping of the southern third of the quadrangle. 
The geologic mapping was completed during the 
season of 1927, which extended from April 25 to 
August 7. During this period the writer was ably 
assisted by William D. Mark, who mapped in detail 
the numerous dikes southeast of Dutch Mountain. 

The writer is glad to acknowledge the whole-hearted 
cooperation and hospitality of the people of the dis- 
trict, all of whom assisted the work freely. Particular 
thanks are due to Messrs, Rowley, Greenwood, and 
Tiffany, of the Western Utah mine; Mr. Leffler Palmer, 
of the Rube mine; Mr. James Busby, of the U.S. 
mine; and Messrs. Gerster and Ollie Young, whose 
knowledge of the earlier history of the district was very 
helpful. Mr. V. C. Heikes, formerly of the Geological 
Survey and later of the Bureau of Mines, assisted the 
work in every way and provided considerable material 
that would not otherwise have been available. 

During the course of the field work Edwin Kirk 
and G. H. Girty made short visits to the quadrangle 
and were of the utmost assistance in the determination 
of the stratigraphy of the pre-Carboniferous forma- 
tions. The writer was also greatly benefited by the 
visits of G. F. Loughlin, made each season, during 
which his helpful criticisms and advice greatly facili- 
tated the geologic mapping. 

The preparation of the present report has been in- 
fluenced throughout by the discussions and criticisms 
of the writer's colleagues on the Geological Survey, 
especially James Gilluly, and he wishes to express his 
appreciation, particularly to H. G. Ferguson, D. F. 
Hewett, M. N. Short, and G. F. Loughlin, who have 
read and criticized the final manuscript. Many of the 
mineralogie determinations were made by W. T, 



Schaller, C. S. Ross, M. N. Short, and E. P. Henderson, 
and the chemical analyses of the volcanic rocks are 
the work of J. G. Fairchild. The photomicrographs 
are in large part the result of Mr. Short's unusual skill 
with the microscope and camera. 

GEOLOGIC FORMATIONS 

In the following sections are described in their proper 
chronologic order the 28 geologic formations that are 
distinguished on the geologic maps (pis, 1 and 2). 
Of these formations 24 are composed of sedimentary 
rocks and 4 of igneous rocks. 

Of the sedimentary formations 20 are of Paleozoic 
age — 8 in the Cambrian, 2 in the Ordovician, 1 in the 
Silurian, 3 in the Devonian, and 6 in the Carboniferous. 
Only 1 formation is assigned to the Mesozoic, a lime- 
stone of Lower Triassic age. The remaining 7 for- 
mations are thought to belong in the Tertiary. One 
of these is considered to be probably Eocene; an in- 
trusive stock of quartz monzonite and two kinds of 
allied dike rocks are placed in the late Eocene or early 
Oligocene; a series of gravel deposits are questionably 
assigned to the Pliocene; and a group of volcanic 
rocks are tentatively put in the late Pliocene. The 
youngest formation in the quadrangle, composed of 
gravel and lake beds, is of Pliocene (?) to Recent age. 

CAMBEIAN SYSTEM 
PROSPECT MOUNTAIN QUARTZITE (LOWER CAMBRIAN) 

Distribution. — The Prospect Mountain quartzite is 
the oldest formation exposed within the quadrangle. 
The two largest outcrops are bands of varying width 
on the east sides of Dutch Mountain and the Deep 
Creek Mountains. 

The exposure in the Deep Creek Mountains is nearly 
3 miles long and narrows from 4,000 feet in width at 
the 40th parallel to less than 500 feet at Bagley Gulch, 
where the formation ends against a transverse fault. 
The quartzite forms the east base of the mountains, 
its resistant beds rising abruptly from the gravel slopes 
to the east. 

The outcrop on the east side of Dutch Mountain is 
also about 3 miles long and is bounded on the east by 
recent gravel. It varies considerably in width, owing 
to encroachment of gravel on the east and to faulting 
on the west. The width ranges from a few hundred 
feet at the mouth of Tribune Gulch to more than 1 hi 
miles along the ridge 2 miles to the north. A trans- 
verse fault just south of the Garrison Monster mine 
marks the northern limit of the formation. 

In addition to these principal exposures there are 
several smaller outcrops north and east of the Gold 
Hill mine. These are either completely or partly sur- 
rounded by gravel and are in all probability continu- 
ous beneath the gravel. The largest of these areas of 
quartzite forms the prominent summit at an altitude 
of 5,556 feet east of the Rube mine. 



GEOLOGIC FOKMATIONS 



Another small outcrop of the Prospect Mountain 
quartzite surrounded by gravel is found near the edge 
of the Great Salt Lake Desert, 1 mile east of bench- 
mark 4552 on the Deep Creek Railroad. 

Litkology. — The Prospect Mountain quartzite is com- 
posed chiefly of light-gray to dark-brown quartzite, 
but near the base of the exposed section on Dutch 
Mountain there are one or more zones containing a 
large proportion of shaly material. These zones are 
distinguished on the geologic map as shale members. 

The apparent homogeneity of the quartzite portion 
of the formation is due largely to the general presence 
of a brownish stain of iron oxides on the weathered 
surfaces, but close examination shows several distinct 
varieties of rock. Of these the most widely distributed 
is a fine to medium grained quartzite which is pale 
pinkish on fresh fracture. The grains are partly 
rounded and closely packed, the quartz cement between 
grains forming a very small portion of the total rock. 
A second variety has similar grain but is rather dark 
purplish on fresh fracture, owing to the presence of 
iron oxides in the cementing material. This variety 
is usually found interlaminated with the lighter- 
colored variety, and the difference in color reveals 
cross lamination throughout. The laminae meet at 
low angles (generally 10° or less) and may be trun- 
cated by others both above and below. Where the 
rock consists of only one variety this cross lamination 
is not visible, even on weathered surfaces. At no 
place was the cross lamination found to depend on 
varying size of grain. On the contrary, it seemed to 
be confined to the finer-grained quartzites just 
described. 

In addition to the fine-grained quartzites, many 
beds are composed largely of quartz grains from 5 to 
10 millimeters in diameter. The larger grains are less 
rounded than the smaller ones and locally consist of 
altered feldspars instead of the usual quartz. The 
larger grains lie in a matrix of smaller quartz grains, 
and by an increase in the amount of these smaller 
grains the rock grades into typical fine-grained quartz- 
ite: In general these coarser-grained quartzites are 
light-colored on fresh fracture. Within both coarse- 
grained and fine-grained quartzites there are beds of 
conglomerate as much as 2 feet thick. The pebbles in 
these beds are predominantly of white vein quartz, 
with a minor proportion of rose quartz and a very few 
of red jasper. The maximum size of pebble observed 
was about 75 millimeters and the average size about 
25 millimeters. Such conglomerate beds are lenticular 
and cannot be traced for any great distance along the 
strike. They were found extremely useful, however, 
in proving the identity of the rocks in the scattered 
and metamorphosed exposures east of the Rube mine, 
where the Prospect Mountain quartzite has been 
faulted against the Oquirrh formation, which there 
consists largely of fine-grained sandstone without 
conglomerate layers. 



In many places the bedding is marked by thin shale 
zones, in others by the change from a dominantly 
colored bed to one almost colorless, and in still others 
by an abrupt change in grain size. Wherever areas of 
such bedding planes have been exposed by erosion any 
sedimentary structural features, such as ripple marks, 
that may have been present have been destroyed by 
later movements parallel to the bedding surface. 

The upper 75 to 100 feet of the quartzite differs 
from the beds beneath in several respects. The most 
noticeable difference is in the thickness of the indi- 
vidual beds, which ranges from 10 to 30 feet, in contrast 
to 1 to 5 feet in the remainder of the formation. The 
color ou fresh fracture is a medium gray, but weathered 
surfaces are of a uniform dark brownish red, which 
results from the leaching and subsequent deposition of 
iron from numerous pyrite cubes scattered throughout 
the rock. The size of grain (1 to 2 millimeters) is 
somewhat larger than in many of the lower beds, and 
cross lamination is apparently absent, 

A conglomerate occurs just beneath this upper part 
of the quartzite. It is best exposed south of Dry 
Canyon but may also be found for a mile or so to the 
north, usually as float. It is a dark rock that commonly 
forms a bench, with the result that its relations in most 
croppings are obscure. Its chief feature of interest is 
that its pebbles represent several different kinds of 
rock and thus differ markedly from those of the quartz- 
pebble conglomerates described above. The pebbles 
are angular to subangular and are as much as 6 inches 
in maximum diameter. Many are tabular or slaty. 
They include quartzite, schists, especially a quartz- 
biotite schist, slate, and various altered igneous rocks, 
one pebble of a granitic rock being noted. With these 
are smaller quartz grains, such as are found in the 
quartzites below. The matrix is in most places a 
slate, in which abundant specular hematite has been 
developed, but locally it is a fine-grained quartzite. 
Along the strike, to the north of Dry Canyon, the bed 
contains but few pebbles and is not unlike other shale 
beds in the formation, except for its greater thickness. 
Similar beds of shale are present at several other 
horizons in the formation. These are generally only a 
fraction of an inch thick but locally are as much as a 
foot. In the thicker beds slaty cleavage has been 
developed. 

In all exposures the Prospect Mountain quartzite is 
cut by numerous joints. As a rule, these are parallel 
in strike and dip to nearby major or minor faults. 
On Dutch Mountain the formation is so thoroughly 
jointed that it has weathered into angular blocks 
which conceal bedrock exposures over wide areas. 
Along the fault planes the quartzite, in addition to 
being brecciated, has been bleached to a dull white 
color. Discontinuous thin veinlets of white quartz are 
found everywhere. No general course for the veinlets 
was ascertained, other than that many follow the 
bedding planes. 



6 



GOLD HILL MINING DISTRICT, UTAH 



Shale members. — On the lower slopes of the east side 
of Dutch Mountain, there are several exposures of 
slaty shales and rather thin-bedded dark quartzites. 
These have been distinguished on the geologic maps 
(pis. 1 and 2) as shale members. Exposures on Basin 
Creek, in the Deep Creek Mountains south of the 
quadrangle, show that they are conformably inter- 
bedded with the normal light-colored Prospect Moun- 
tain quartzites at the bottom of the section exposed 
there. These beds are similar in lithology and position 
to the poorly exposed beds on Dutch Mountain. The 
shales are generally a dark grayish blue or greenish 
blue, though locally shades of khaki color are observed. 
Many beds are distinctly sandy, and in almost all of 
them a pronounced slaty cleavage, essentially parallel 
to the bedding, has been developed. The quartzite 
beds are mostly 6 inches or less in thicloiess. They 
are much darker than the quartzites that make up the 
greater part of the formation, owing to a larger content 
of impurities. 

Thickness. — No complete section of the Prospect 
Mountain quartzite was observed. In the southern 
part of the quadrangle a maximum thickness of about 
800 feet is exposed, and on Dutch Mountain the beds 
probably exceed 3,000 feet, although the exposures 
there are much too poor for measurement. A rapid 
and very rough measurement of the exposed portion of 
the formation was made on Basin Creek, about 7 
miles south of the 40th parallel. This amounted to 
4,750 feet and may be summarized as follows: 

Section of Prospect Mountain quartzite on Basin Creek 

Cabin shale. Feet 

Massive, dominantly light-colored quartzite 2, 500 

Slate and quartzite (shale member) _ - „ 300 

Light-colored quartzite 500 

Slate and quartzite (shale member) , . . 600 

Light-colored quartzite 200 

Shale and quartzite (shale member) , 100 

Light-colored quartzite 500 

Shale 50 

Base not exposed. 

4,750 

Age and correlation. — No fossils have been found in 
the Prospect Mountain quartzite, but as there is no 
apparent break of importance between it and the over- 
lying Cabin shale, which contains Lower Cambrian 
fossils, the formation is considered to be of Lower 
Cambrian age. 

A quartzite series of varying thickness, occurring 
beneath the lowest fossiliferous Cambrian, which 
usually is a shale, is widespread over western Utah 
and eastern and southern Nevada. In the Nevada 
localities that have been described the formation is 
over 1,000 feet in thickness and is overlain by Lower 
Cambrian sediments. The name Prospect Mountain 9 

' Hague, Arnold, Abstract of the report on the geology of the Eureka district, 
Nevada: TJ.S. Geol. Survey Third Ann. Bept., p. 254, 1883. 



quartzite has been generally applied to the formation. 
For Utah Butler 10 suggested the name Tintic quartz- 
ite, from the Tintic Mountains, for this formation. 
However, as the overlying shale has been determined 
to be Middle Cambrian at some localities in Utah 
(as at Tintic u and Blacksmith Fork 1Z ), thus suggesting 
that the top of the quartzite may here be Middle 
Cambrian, and to be Lower Cambrian at others 
(Oquirrh Range 13 ), and also as the Nevada name has 
priority, the formation is here called Prospect Mouns 
tain quartzite rather than Tintic quartzite. 

Several investigators in the Wasatch Range in 
recent years have shown the presence of an uncon- 
formity in the thick nonfossiliferous and predominantly 
siliceous sediments below the fossiliferous Cambrian 
and have considered it to mark the boundary between 
the Cambrian and the Algonkian. u This unconformity 
is marked by a thin conglomerate, containing pebbles 
of the underlying rocks. Because of this discovery it 
was at first thought that the conglomerate near the 
top of the formation in the Gold Hill region might 
mark the Cambrian-Algonkian contact, as it contains 
boulders of different kinds of rock, and in some ex- 
posures its lower contact is discordant. But further 
field work and comparisons with the published descrip- 
tions of the unconformity in the Wasatch Range have 
led to the conclusion that the conglomerate in the 
Gold Hill region is of only local significance. This 
conclusion is based chiefly on its slight extent, its 
gradation northward into shale similar in appearance 
to other shale beds both above and below, and the 
dissimilarity of the quartzites below it to any of the 
known Algonkian beds in the Wasatch Range, 

CABIN SHALE (LOWER CAMBRIAN) 

Distribution. — The Cabin shale, named from Cabin 
Gulch, between North Pass and Sheep Canyons, crops 
out as a narrow band above the Prospect Mountain 
quartzite on the east side of both the Deep Creek 
Mountains and Dutch Mountain. On the southeast 
flank of Dutch Mountain the shale is concealed by 
faulting, and the Prospect Mountain quartzite is in 
contact with higher beds. The formation is much 
less resistant to erosion than the quartzites above and 
below and in most localities forms a narrow brush- 
covered bench, 

IMhohgy. — The formation is dominantly shaly, the 
typical rock being a dark-green to khaki-colored shale, 



. » Butler, B. S., Ore deposits of Utah: U.S. Oeol. Survey Prof. Paper 111, p. 78, 
1920. 

u Loughlin, O. F., Geology and ore deposits of the Tintic mining district, Utah: 
U.S. Oeol. Survey Prof. Paper 107, p. 25, 1919. 

J« Walcott, C. C, Cambrian sections of the CordlUeran area: Smithsonian Misc. 
Coll., vol. 63, no. 5, p. 171, 16(8. 

» Emmons, 8. F., in Spurr, J. E„ Economic geology of the Mercur mining dis- 
trict, Utah; U.S. Oeol. Survey Eighteenth Ann. Bept., pt. 2, p. 362, 1895, 

» Blaekwelder, Eliot, New light on the geology of the Wasatch Mountains, Utah: 
Qeol. Soc. America Bull., vol. 20, pp. 520-523, 1910. Hintze, P. P., A contribution 
to the geology of the Wasatch Mountains, Utah: New York Acad. Sci. Annals, 
vol. 23, p. 103, 1913. Calkins, P. C, Ore deposits of Utah: U.S. Oeol. Survey Prof. 
Paper 111, p. 235, 1920. 



GEOLOGIC FORMATIONS 



with little sandy material and almost no calcium car- 
bonate. Weathered surfaces are lighter in color and 
in most places are shades of brownish red. Slaty cleav- 
age is developed in much of the formation, as a rule 
nearly parallel to the bedding, though in several places 
it cuts the bedding at a small angle. The slaty cleav- 
ages are generally marked by the <J eve l°P men t °f 
flakes of white or golden-colored mica. In many beds, 
especially those near the base of the formation, cubes 
of limonite pseudomorphous after pyrite are present. 

There are several variants from the typical rock 
just described. One of these is a light-gray finely lam- 
inated shale, generally 2 feet or less thick, found at the 
base of the formation, both in the Deep Creek Moun- 
tains and on Dutch Mountain. Near the middle of 
the section the shale locally contains small amounts of 
calcite, as shown by a weak effervescence with dilute 
hydrochloric acid. This Mmy variety is of a lighter 
color than the rest of the rock. On fresh fractures it 
is a light greenish gray, and on weathered surfaces 
brownish or reddish yellow. Both near the base and 
near the top of the section thin lenticular laminae of 
sandstone are found. These are 1 millimeter or so 
thick and are of lighter shades than the thicker inter- 
bedded shale. 

Just beneath the top of the formation there is a per- 
sistent and, for this formation, unique concretionary 
bed. The numerous concretions are about the size 
of a silver dollar and lie parallel to the bedding planes. 
They differ from the remainder of the rock in having 
a slightly darker color, a somewhat finer grain of the 
mica, and a larger proportion of sand. 

The lower contact of the shale is notably sharp. 
The light-gray shale mentioned above rests upon thick- 
bedded Prospect Mountain quartzite with no observ- 
able transition. There is, however, no indication of 
anything other than a purely lithologic break. The 
upper contact is not so well defined. The line has been 
drawn at the top of a 15-foot zone of interbedded 
sandy shale and shaly quartzite. Many of the quartz- 
ite beds are flecked with iron oxides. Above the 15- 
foot interval are the basal thicker-bedded Busby 
quartzites. 

Thickness, — Two measurements of the thickness of 
the Cabin shale gave 493 and 530 feet. The first was 
made on the ridge south of Sheep Canyon and the 
second on the north side of Cabin Gulch. A third 
section, measured on the south side of Dry Canyon, was 
only 114 feet thick; and a fourth, half-way between the 
Spotted Fawn mine and the Garrison Monster mine, 
381 feet. The first two figures are thought to approx- 
imate the true thickness. The diminution in thick- 
ness indicated by the other measurements was prob- 
ably effected by local overriding within the shale 
along strike faults, but exposures are generally too 
poor to permit exact proof. Such variations in thick- 
ness are numerous on Dutch Mountain, and some are 
also found in the Deep Creek Mountains. 



Age and correlation. — A single fragmentary trilobite 
was found by Edwin Kirk in the Cabin shale at a hori- 
zon somewhat above the middle of the formation. It 
was submitted for identification to Dr. C. E. Eesser, 
of the Smithsonian Institution, who reported as fol- 
lows: "The thoracic segment from Sheep Canyon, 
because of the sharp angle on its anterior side, seems 
pretty definitely to belong to a mesonacid, which would 
make it Lower Cambrian in the present usage of that 
term in the West." 

It is rather difficult to determine the exact correla- 
tion of the Cabin shale in the published sections from 
areas in Utah and Nevada. The sequence quartzite, 
shale, and limestone is common to most of these sec- 
tions, but fossil collections from the shale zones in 
areas in Utah and Nevada indicate a lack of contempo- 
raneity in deposition. For this reason, the loeal name 
Cabin shale has been applied to the shale found at Gold 
Hill, rather than Pioche shale or Ophir shale, which 
have been widely used in Nevada and Utah, respec- 
tively. 

It is probable that the formation closest in age to 
the Cabin shale is the lowest shale belt in the House 
Range, which was called Pioche by Walcott. 16 The 
Pioche shale, in its type locality, 16 differs from the 
Cabin shale in being over twice as thick and in con- 
taining several limestone beds. It probably includes 
in the lower part beds older than those present in the 
shale at Gold Hill. 

The shale zones in the Tintic, 17 Ophir, 18 and Cotton- 
wood-American Fork 19 areas, however, are, on the 
whole, younger. These shales, known generally as the 
Ophir shale, contain Middle Cambrian fossils through 
the greater part of their extent, but in the Ophir and 
Cottonwood districts Lower Cambrian fossils have been 
reported from the basal portions. The Cabin shale is 
perhaps equivalent in age to the lower portion of the 
shale and the upper beds of the underlying quartzite 
at these localities. 

BU8BT QUARTZITE (MIDDLE CAMBRIAN) 

Distribution, — In the Deep Creek Mountains the 
Busby quartzite is terminated on the south side of 
North Pass Canyon by the same transverse fault that 
cuts off the outcrops of the Cabin shale and Prospect 
Mountain quartzite. The quartzitic beds of the Busby 
are fairly resistant to erosion and form a series of low 
cliffs above the weak shale beds beneath. The for- 
mation is exposed also on Dutch Mountain in a band 
of extremely irregular width from a point half a mile 
south of the Spotted Fawn mine to the transverse 

'« Walcott, C. D., Cambrian sections of the Cordilleran area: Smithsonian Misc. 
Coll., vol. 53, no. 8, p. 184. 1908. 

» Westgate, L. O., Geology and ore deposits of the Pioche district, Nev,: tJ.S. 
Oeol. Survey Prof. Paper 171, pp. 8-10, 1932. 

" Loughlin, Q. F., Geology and ore deposits of the Tintic mining district, Utah; 
U.S. Geol. Survey Prof. Paper 107, p. 29, 1919. 

'I Gilluly, James, Geology and ore deposits of the Stockton and Fairfield quadran- 
gles, Utah: U.S. Geol. Survey Prof. Paper 173, pp. 9-12, 1932. 

'» Calkins, F. 0., The ore deposits of Utah: U.S. Geol. Survey Prof. Paper 111, 
p. 237, 1920. 



8 



GOLD HILL MINING DISTKICT, UTAH 



fault south of the Garrison Monster mine. Another 
small outcrop is found in the foothills west of Garrison 
siding on the Deep Creek Railroad, The formation 
is poorly exposed on Dutch Mountain, because of the 
numerous faults which cut it and cause either duplica- 
tion or elimination of individual beds. The name is 
taken from Busby Canyon, on the east slope of Dutch 
Mountain, in which the formation is exposed. 

Lithology. — The basal portion of the Busby quartzite, 
50 to 75 feet thick, is a fairly coarse grained rock, gray- 
brown on fresh fracture and weathering to shades of 
reddish brown. Many of the grains are more than 1 
millimeter in diameter and a few are as much as 5 mil- 
limeters. Most of the grains are of quartz, and the 
remainder are of rock fragments, so that this rock 
locally resembles a graywacke. Shale partings are 
present and in places show mud cracks, which are 
filled by the coarser sands that make up the main 
portion of the rock. Iron oxide flecks are abundant. 

A rather distinctive variety is found near the base 
of the formation in the Dutch Mountain exposures. 
This is a white quartzite containing irregular dark- 
brown patches. Thin sections of it show that the 
brown portions of the rock differ from the white por- 
tions only in the presence of abundant interstitial iron 
oxide. The quartz in this as well as in other quartzitic 
parts of the formation is crowded with microscopic 
fluid inclusions, in many of which gas bubbles are 
present. 

Above the basal, coarse-grained quartzite there is 
little uniformity or continuity in the strata. Fine- 
grained sandy and shaly material are the principal 
components and are present in varying proportions in 
the individual beds. The most abundant varieties 
are thin-bedded pink to purplish fine-grained quartz- 
ites and thin-bedded gray quartzitic sandstones which 
are in many places micaceous. Green sandy shales 
are less abundant than the quartzite and sandstone 
except near the top of the formation, where they 
predominate. 

The top of the formation has been placed at the base 
of the lowest limestone bed. The contact is not sharp, 
as there are a few thin quartzite beds above the bound- 
ary as thus drawn. It is also rather certain that the 
lowest limestone is not a continuous bed. But the zone 
including the lowest limestone and highest quartzite, 
which probably does not exceed 25 feet in thickness, 
makes a distinct lithologic break from beds of dis- 
tinctly sandy and shaly character to beds character- 
istically calcareous. 

Thickness. — Sections of the Busby quartzite meas- 
ured on the south and north sides of Dry Canyon and 
the north side of Sheep Canyon gave thicknesses of 
519, 433, and 452 feet, respectively. A fourth meas- 
urement about halfway between the Spotted Fawn and 
Garrison Monster mines showed 314 feet. The first 
figure possibly includes some duplication caused by 



undetected normal faulting; and the fourth is probably 
much too small for the same reason. The second and 
third figures are believed to be fairly close to the true 
thickness. 

Age and correlation.— -In addition to numerous an- 
nelid (?) trails a single fragmentary trilobite was found 
in the Busby quartzite, but unfortunately it was lost 
before being identified. The overlying Abercrombie 
formation contains abundant remains of a Middle 
Cambrian fauna, whereas the shale beneath the Busby 
is of Lower Cambrian age. Because of the presence 
of coarser material at the base of the formation, the 
lack of a sharp contact between the Busby and the 
Abercrombie, and the evidence of shallow-water con- 
ditions indicated by mud cracks, the Busby quartzite 
is thought to be best considered the initial deposit of 
the Middle Cambrian rather than the final deposit of 
the Lower Cambrian. No evidence of an angular 
unconformity at the base was seen, however, and it is 
indeed negatived by the continuity of the concretionary 
bed of the Cabin shale, which lies immediately beneath 
the base of the quartzite, and the presence of 15 feet 
of gradational beds. 

In stratigraphic position the Busby is probably equiv- 
alent to the Langston (?) formation in the House 
Range 20 , which lies above a sandy shale and is further- 
more described as being almost a sandstone at the 
base. The correlation of the formation with other 
Utah sections is not certain except that it may repre- 
sent that part of the Ophir shale, as exposed in Cotton- 
wood Canyon 21 and the Oquirrh Mountains, 22 lying 
above the Lower Cambrian portion. 

ABERCROMBIE FORMATION (MIDDLE OAMBRIAJf) 

Distribution. — The Abercrombie formation, named 
from Abercrombie Peak, on the ridge south of Dry 
Canyon, is completely exposed only in the southern 
third of the quadrangle, where it crops out as a wide 
band along the eastern part of the Deep Creek Moun- 
tains. This band is terminated on the north side of 
North Pass Canyon, in part by the overriding of 
younger formations adjacent to a transverse fault, but 
chiefly by burial beneath gravel. Incomplete and bad- 
ly faulted sections are found on the east and northeast 
sides of Dutch Mountain from a point south of the 
Spotted Fawn mine northward nearly to the northern 
limit of the quadrangle. 

Lithology. — The Abercrombie formation is composed 
dominantly of thin-bedded argillaceous limestone, 
interbedded with which are a few beds of more massive 
limestone and considerable amounts of shale. Except 
for the more massive limestone beds the formation is 
in general poorly exposed. The shale in particular 

>» Walcott, C. D., Cambrian sections of the Cordffleran area: Smithsonian Misc. 
Coll., vol. 53, no. 5, p. 183, 1908. 

>' Calkins, F. C, Ore deposits of Utah: U.S. Geol. Survey Prof. Paper 111, pp. 
23&-236, 1919. 

» Gilluly, James, Geology and ore deposits of the Stockton and Pairield quad- 
rangles, Utah: U.S. Geol. Surrey Prof. Paper 173, pp. 11-12, 1B32. 



U.S. GEOLOGICAL SURVEY 



PROFESSIONAL PAPEK 177 PLATE 4 



-^*5&> '' ■■■■■■■ 












.1. BONNEVILLE BEACH AND SPIT, EAST OF DUTCH MOUNTAIN. 




B. DUTCH MOUNTAIN FROM THE SOUTHEAST. 





■■■■ ■ ^■■■■vfissB&te& 







C. CLIFTON FLAT FROM THE SOUTHWEST. 



U.S. GEOLOGICAL SURVEY 



PROFESSIONAL PAPER 177 PLATE 




v.3?r ». v 



ie»A"a: 







HOCKS UK GOLD HILL QUADRANGLE. 

A, Mottled Young Peak dolomite; B, laminated Trippt* limestone; C, pisoliUc dolomite from the Hicks Formation; D, ' 'marble cake" dolomite near the base of the 
Laketownt dolomite; E, laminated Simonson dolomite; F, chert-pebble conglomerate with oolitic matrix from Oquirrh formation. 



GEOLOGIC FORMATIONS 



9 



crops out in but few places, usually forming a bench 
between steeper slopes underlain by more resistant 
limestone. 

The rock most characteristic of the series is a blue- 
gray dense limestone whose thin bedding is caused by 
thin partings of shale, most of which are yellow or 
buff, though locally pink or light-gray colors are found. 
The limestone portions are from a quarter to half an 
inch thick and leave a large residue of clay when dis- 
solved in hydrochloric acid. The shale partings con- 
tain minor amounts of calcite and quartz but are dom- 
inantly made up of a clay mineral of low birefringence. 
The thickness of the shale partings averages about 1 
millimeter but is extremely variable. Along many of 
the bedding planes the shaly material is present only 
locally, resulting in a mottling by splotches of yellow 
or reddish shale. Less commonly splotches that are 
not parallel to the bedding may be found within the 
limestone. This variety is best developed near the 
top of the section in North Pass Canyon, where the 
shaly splotches are light gray. 

With increase in the amount of clay the rock passes 
into a khaki-colored or light-greenish shale contain- 
ing but little calcite. On weathered surfaces the shale 
shows the reddish or yellowish tints found in the shaly 
partings in limestone. Fossils are much more abun- 
dant in the shale than in any other portion of the forma- 
tion, and nearly every bed contains at least a few phos- 
phatic brachiopods of the genus Obolus. 

Boundaries between the thin-bedded limestone and 
the more massive limestone are also gradational. The 
shaly partings and splotches become fewer, and the 
resultant rock is a resistant fine-grained to dense blue- 
gray limestone with local small inclusions of shale. 
The more massive beds contain very little material 
that is insoluble in dilute acid. Included in the more 
massively bedded limestone are beds of darker-colored 
limestone containing abundant oval algal or concre- 
tionary growths. These beds are in some places finely 
oolitic and in others contain thin intraformational con- 
glomerates with small fossil fragments, but such beds 
are neither abundant nor persistent. 

As might be expected from such gradations between 
the different lithologie varieties included in the forma- 
tion, there is but little persistence of individual beds 
along the strike. Three sections about a mile apart 
showed only a very generalized agreement in the suc- 
cession of beds. This variation is especially true of the 
upper boundary of the formation. South of North Pass 
Canyon the base of the lowest massive dolomite in the 
overlying Young Peak dolomite has been considered to 
mark the upper limit. But the dolomite beds pinch 
out to the north, and on the north side of North Pass 
Canyon the top of the formation has been considered to 
be the base of thick-bedded limestones resembling in 
texture the dolomite beds of the Young Peak dolomite. 



The following section, measured on the south side 
of Dry Canyon, is similar to the other sections meas- 
ured, but it should be understood that the individual 
beds are not persistent. 

Section of Abercrombie formation on south side of Dry Canyon 

Young Peak dolomite. 

Abercrombie formation: f e a 

Thin-bedded limestone, gray mottled 188 

Shale .. 46 

Thin-bedded limestone; thin shale beds at 96 and 

126 feet from top 626 

Shale, calcareous at top 180 

Laminated gray limestone 154 

Shate, calcareous at top 180 

Thin-bedded limestone 61 

Massive limestone, concretionary, oolitic, and with 

local conglomerates 13 

Thin-bedded limestone 88 

Massive limestone, concretionary and oolitic 39 

Thin-bedded limestone 17 

Shale.— .... 90 

Thin-bedded limestone. _ , - . 30 

Calcareous shale 90 

Thin-bedded limestone 21 

Massive limestone, dolomitized 14 

Thin-bedded limestone 93 

Massive limestone, dolomitized 1 48 

Shale, calcareous at base 173 

Thin-bedded limestone 71 

Shale, calcareous at base 119 

Massive limestone, dolomitized 62 

Thin-bedded limestone 148 

Shale, calcareous at top; a few thin beds of quartzite 

at base 147 

Limestone, dolomitized 10 

Sandy shale (top of Busby quartzite) . 

2,708 

Most of the massive limestone beds, as indicated in 
the section, have been partly dolomitized. The 
altered rock weathers to a light-brown color that 
sharply distinguishes it from the unaltered blue-gray 
limestone. The dolomite is coarser-grained and more 
resistant to weathering than the limestone. The 
dolomitized portions show no relations to bedding 
planes or to any depositional features but are localized 
along joints or minor faults, which strike in a general 
east-west direction and are in places accompanied by 
minor deposits of lead and silver. The alteration is 
clearly much later than the original formation of the 
sediments. 

Thickness. — Three measurements of the formation 
on the south and north sides of Dry Canyon and the 
north side of Sheep Canyon gave thicknesses, respec- 
tively, of 2,708, 2,080, and 2,680 feet. The first and 
third figures probably correspond closely with the 
true thickness of the formation. The second figure is 
much too low and is the result of overriding along a 
strike fault, which, on the ridge line, cuts the formation 
about 850 feet above the base. 



35311— W 2 



10 



GOLD HILL MISTING DISTRICT, UTAH 



Age and correlation. — Fossils collected from several 
of the shale zones show that the Abercrombie forma- 
tion is of Middle Cambrian age. Dr. C. E. Resser, of 
the Smithsonian Institution, reports as follows upon 
the collections: 

12. At fork in Dry Canyon, 1 mile west of spring: 
Bathyuriscus productus (Hall and Whitfield). 
Obolus sp. 
Hyolithes sp. 

16. Ridge line on south side of Dry Canyon at altitude of 
about 7,900 feet: 

Zaeanthoides sp. 
Bathyuriscus productus. 
Lingulella sp. 
This seems to represent the lowest horizon among the 
collections. The fauna corresponds with the Chisholm 
and Ophir. 

18. Just east of the 7,300-foot closed contour on the north 
side of Sheep Canyon: 

Paterina cf. P. utahensis. 
Elrathia sp. 

19. Just west of the 8,200-foot closed contour 
on the south side of Dry Canyon: 

Micromitra sp. 

17. Saddle west of peak 8182, on south side of 
Dry Canyon: 

Obolus sp. 

Fucoids. 

Elrathia sp. 
All these are Middle Cambrian and appar- 
ently about the same horizon somewhere in the 
lower part. 



The formation is possibly equivalent to 
the Chisholm shale and the lower portions 
of the Highland Peak limestone at Pioche, 23 
the Teutonic, Dagmar, and Herkimer lime- 
stones at Tintic, 24 and the Hartmann and 
Bowman limestones at Ophir. 26 These cor- 
relations are based almost solely on posi- 
tion in the stratigraphic column, as variations in lith- 
ology are characteristic of the Middle Cambrian in this 
portion of Utah. 



mile to the east it reappears from beneath the plate 
and continues eastward for half a mile before being 
covered by later gravel. 

Lithology.- ^The Young Peak dolomite changes 

almost completely in lithologic character in the 4 
miles along which it is exposed. At the southern 
boundary it is composed almost entirely of dolomite, 
but in North Pass Canyon the same horizon is marked 
by limestone beds with only a few thin interbedded 
dolomite layers. This variation does not occur 
abruptly but is caused by a gradual itfterfmgering 
northward of limestone at both the top and the bottom 
of the formation, until finally on the north side of 
North Pass Canyon only one dolomite bed about 5 
feet thick is exposed. 

The base of the formation as mapped is neither 
synchronous nor continuous. As far north as the 
head of Bagley Gulch it is mapped at the lowest 
locally exposed bed of massive gray dolomite. Owing 




.^ 

1.3 mi. = <ff 







^:~^ 



V777- --- 



•-f 



5 

zzzzi 



7ZZLZ.~~ 



-0.6 mi." — -+ — 0.5 mi. - 



Limestone 



YOUNG PEAK DOLOMITE (MIDDLE CAMBRIAN) 

Distribution. — The Young Peak dolomite is named 
from Young Peak, on the north side of Dry Canyon, 
the summit of which is underlain by the formation. 
It crops out only in the southern part of the quadrangle 
in the Deep Creek Mountains. It forms a north-south 
band, somewhat interrupted by faulting, extending 
from the southern boundary to the north side of 
North Pass Canyon, where it curves to the east before 
disappearing beneath an overthrust plate. Half a 



» Westgate, L. O., Geology and ore deposits of the Pioche district, Nev.: "U.S. 
Oeol. Survey Prof. Paper 171, pp. 11-13, 1932. 

» Loughlin, Q. F., Geology and ore deposits of the Tintic mining district, Utah: 
U.S. Qeol. Survey Prof. Paper 107, pp. 27-28, 1919. 

» ! Qilluly, James, Geology and ore deposits of the Stockton and Fairfield quad- 
rangles, Utah: U.S. Geol. Survey Prof. Paper 173, pp. 12-15, 1932. 



Dolomite 
Figure 2. — Sections of the Young Peak dolomite, showing the interfingering northward of limestone, 
1, South side of Dry Canyon; 2, north side of Dry Canyon; 3, north side of Sheep Canyon; 4, ridge 
between Bagley and Trippe Gulches; 5, ridge between Trippe Gulch and North Pass Canyon. 

to the successive lensing out of the lower beds north- 
ward, however, as indicated in the preceding para- 
graph and in figure 2, the base is represented not by 
one continuous bed but rather by higher and higher 
beds. Northward from Bagley Gulch, the dolomite 
beds thin out so rapidly that it was thought best to 
continue the boundary at the base of a series of mas- 
sive limestones containing rodlike markings similar to 
those in the typical dolomite to the south. Although 
this is admittedly a compromise between lithologic 
mapping and synchronous mapping, it seemed to be 
the best course available. Mapping the continuation 
of the lowest dolomite bed northward would be im- 
possible, because the interfingering limestone beds are 
indistinguishable, and poor exposures and numerous 
displacements by both major and minor faults pre- 
clude continuous tracing. To continue the mapping 
of the lowest dolomite bed as the base in the vicinity 
of North Pass Canyon would not only be difficult on 



GEOLOGIC FORMATIONS 



11 



the scale of this map but would give a false suggestion 
of an overlap. The mapping adopted shows the 
horizon continuing conformably, as it does, and 
facilitates the delineation of the somewhat complex 
structure on the north side of North Pass Canyon. 

The upper contact of the formation, on the other 
hand, is sharp. It has been taken as the base of a 
dark-gray dolomite containing abundant nodules of 
black chert, which are as much as a meter in maximum 
diameter. This bed is overlain by a cream-colored, 
finely laminated dolomite. This sequence persists 
throughout the outcrop of the formation, and there 
are no beds containing such chert nodules lower in 
the section and none above until the upper portion of 
the Chokecherry dolomite is reached, about 3,000 feet 
higher, and here the characteristic laminated dolomite 
is missing. The beds above the upper boundary are 
essentially all limestones, many of them similar to 
beds in the Abercrombie formation. 

No section for the north side of North Pass Canyon 
is available because extreme crushing and minor 
faulting prohibit accurate measurement, but the base 
of the formation there is the same as that shown in 
section 5 of figure 2. The dolomite present in such a 
section would be limited to a 5-foot bed somewhat 
above the middle of the thickness shown. 

The typical rock of the dolomitic portion of the 
formation is a dark-gray to black dolomite spangled 
with short white rods of dolomite. The rods have an 
average length of about 10 millimeters and an average 
diameter of about 1 millimeter. They contain a little 
calcite, as shown by slight effervescence .with dilute 
hydrochloric acid. The dolomite matrix in which the 
rods occur is finely crystalline, the grains being 0.5 
millimeter or less in diameter. The rods are composed 
of grains of slightly larger size. The grains of both 
rods and matrix are readily distinguished by the 
naked eye, the rock thus differing from the dense 
limestones found beneath in the Abercrombie forma- 
tion. Locally the spangled rock shows a mottling 
caused by irregular splotches of darker and lighter 
dolomite (pi. 5, A). The rods in such varieties are 
generally localized in the darker splotches. The 
mottled rock is generally found near the, top of the 
formation and is thinner-bedded than the rock below. 
Much of the thinner-bedded rock contains but few of 
the rods, and in many beds they may be entirely 
lacking. The lighter-colored portions of the mottled 
dolomite generally effervesce weakly with dilute 
hydrochloric acid, showing that they contain some 
calcite. 

The limestone of the formation includes several 
varieties. A gray mottled limestone similar to that 
found in the Abercrombie formation makes up the 
greater part of the limestones interbedded with 
dolomite at the top and bottom of the formation. It 
is particularly abundant north of the road in North 



Pass Canyon. The massive limestone that takes the 
place of the dolomite in the middle of the formation 
is medium gray and extremely dense. Many of the 
beds contain white rods similar to those in the dolomite 
but composed of calcite. This fact is of some interest 
in that the rods have been thought to be fossil rem- 
nants, whose structure has been destroyed by sub- 
sequent dolomitization; but the structure of the rods 
where both they and the matrix are of calcite is as 
obscure as where both are of dolomite. If they repre- 
sent organic remains of some sort, it is apparent that 
the lack of structure observed is due to some other 
factor than dolomitization. A few of the beds show 
bedding surfaces covered by a network of what appear 
to be fossil worm tracks. In many places these now 
consist of dolomite and are of lighter color than the 
rest of the rock. 

Age and correlation. — No determinable fossils have 
been found in the Young Peak dolomite. Because of 
its gradation into the underlying Abercrombie for- 
mation, whose age is known, it is thought to be Middle 
Cambrian. Similar lithology has been found in the 
Bluebird dolomite, of Middle Cambrian age, in the 
Tintic district, 26 but a positive correlation with that 
formation is not made, because of the known lack of 
continuity in the lithology in the Gold Hill quadrangle. 
Correlation with formations in other districts in which 
this texture has not been noted must be limited to the 
suggestion that the Young Peak dolomite is equiva- 
lent to the beds in the upper part of the Middle 
Cambrian sequence. 

TRIPPE LIMESTONE CMIDULE CAMBBULN) 

Distribution. — The Trippe limestone, named from 
Trippe Gulch on the south side of North Pass Canyon, 
crops out as a north ward- trending band about 1,000 
feet wide, at an average distance of a mile east of the 
main divide of the Deep Creek Mountains. The out- 
crop extends northward from the southern border of 
the quadrangle to North Pass Canyon, on the north 
side of which the strike changes to northeast. About 
a quarter of a mile farther along the strike the forma- 
tion disappears beneath a plate of overthrust rocks, 
and three-quarters of a mile east-northeast of this 
point it reappears with a strike of nearly due east, 
which changes to southeast before the beds are covered 
beneath the gravel that flanks the range. The forma- 
tion has not been recognized on Dutch Mountain. 

Lithology. — The Trippe limestone is composed largely 
of thin-bedded limestones but includes also more mas- 
sive limestones, a few dolomite beds, and one thin shale. 

Three sections were measured which show consid- 
erable variation in the lithologic succession, indicating 
that individual beds are generally lenticular. The 



» Loughlin, Q. F., Geology and ore deposits of the Tintic mining district, Utah: 
U.S. Qml Survey Prof. Paper 107, p. 28, 1919. 



12 



GOI£> HILL MINING DISTRICT, TJTAB 



following section was measured on the ridge line on 
the south side of Dry Canyon. 

Section of Trippe limestone on ridge south of Dry Canyon 

Light-gray oolitic, cross-bedded dolomite (base of Lamb 

dolomite) . 
Trippe limestone: Feet 

1. Thin-bedded limestone with gray mottlings 43 

2. Dark dolomite 19 

3. Thin-bedded limestone with pink and yellow mot- 

tUngs 98 

4. Oolitic limestone with local intraformational con- 

glomerates and cross-bedding 13 

5. Thin-bedded limestone like no. 3. Thin shale near 

base 75 

6. Cream-colored, finely laminated dolomite 1 

7. Thin-bedded limestone like no. 3 with local mas- 

sive limestone 46 

8. Coarsely crystalline massive light-gray limestone-.- 19 

9. Laminated medium gray limestone 65 

10. Thin-bedded limestone like no. 3 133 

11. Gray dolomite 17 

12. Thin-bedded limestone like no. 1, massive dark- 

gray dolomite 20 feet above base 79 

13. Finely laminated light-gray dolomite 22 

14. Thin-bedded limestone like no. 1 30 

15. Thin-bedded gray dolomitic limestone 40 

1 6. Thin-bedded limestone like no . 1 . 22 

17. Gray dolomitic limestone 10 

18. Laminated cream-colored dolomite 5 

19. Dark-gray dolomite with black chert nodules 8 

Young Peak dolomite". 

Division 8 of this section is one of the few persistent 
beds and crops out as a low cliff throughout the ex- 
posure of the formation. Its presence is of assistance 
in determining the presence or absence of faults on the 
brush-covered side slopes of the canyons. 

Mottled limestone makes up the hulk of the forma- 
tion and is similar in character to the mottled lime- 
stone of the two lower formations. The dolomite beds 
are dark gray, massive, and without the texture and 
markings characterizing those of the Young Peak 
dolomite. 

The most striking parts of the formation are the 
finely laminated white or cream-colored beds. These 
may be composed of either limestone or dolomite, 
although in no place was a single bed found to grade 
from limestone to dolomite. Locally these beds show 
phenomena that probably have resulted from the 
generation of gas in the carbonate mud prior to consoli- 
dation. In the specimen illustrated in plate 5, B, 
rupture was linear rather than through a vent of small 
cross section. The essential contemporaneity of such 
disturbances is proved by other specimens that show 
bedding continuing undistorted over the jumbled zone. 
One specimen was collected in which such a zone is seen 
to originate in a thin layer composed of tiny dolomite 
fragments in a limestone matrix. 

The base of the formation is taken at the base of a 
dark dolomite containing large lenses and nodules of 



black chert. This bed, though unusually continuous, 
apparently does not indicate any significant time 
break, for the limestone beds above are similar to 
those which are found interbedded with the dolomite 
beds of the Young Peak dolomite, below. 

The upper boundary of the formation has been 
placed at the base of a series of massive light-gray 
dolomites, many of which are oolitic and cross-bedded. 
The lithologic change is abrupt, but no other evidence 
of unconformity was determined. 

Thickness. — A section measured on the ridge line 
south of Dry Canyon gave a thickness of 745 feet, 
and one on the ridge south of Sheep Canyon 765 feet. 
On the ridge south of North Pass Canyon, however, 
the thickness measured was only 680 feet. 

Age and correlation. — No fossils have been found in 
the Trippe limestone, but it is thought to be of Middle 
Cambrian age. This opinion is based on the lithologic 
resemblance of the mottled limestone members to 
those in the two underlying formations and on the 
lithologic break between it and the overlying Lamb 
dolomite which is believed to be of Upper Cambrian 
age. Whether the variations in thickness shown by 
the measured sections indicate an unconformity at the 
top of the formation or are due simply to minor fault- 
ing or concealed changes in dip is not known. An 
unconformity between the Middle and Upper Cam- 
brian has not been previously reported in Utah, and 
the evidence in this area is not sufficient to consider 
that one exists. Walcott w believed that sedimentary 
barriers and local warpings are sufficient to explain 
the faunal change. 

The Cole Canyon dolomite in the Tintic district m 
is possibly equivalent to the Trippe limestone. Each 
overlies a dolomite formation of similar texture, and 
the Cole Canyon contains laminated cream-colored 
dolomite beds resembling those found in the Gold 
Hill quadrangle. Any further correlation is not 
warranted, owing to the lack of fossils and the known 
lithologic variations. 

LAMB DOLOMITE (UPPER CAMBRIAN) 

Distribution. — The Lamb dolomite is exposed as a 
faulted band, about a quarter of a mile wide, at 
various distances east of the divide in the Deep Creek 
Mountains. It extends in a general northerly direction 
from the southern boundary of the quadrangle to 
North Pass Canyon. North of this canyon the trend 
of the outcrop changes to northeast and then to east, 
and the width of the exposure ranges from a hundred 
yards to over half a mile. The formation in this area 
is highly shattered, owing to the fact that it overrides 
three of the lower formations and is itself overridden 



17 Waloott, O. D., The Cambrian and its problems, in Problems of American 
Geology, p. 191, Tale University Press, 1915. 

» Loughlin, O. P., Geology and ore deposits of the Tintic district, Utah: U.S. 
Qeol. Survey Prof. Paper 107, p. 28, 1919. 



GEOLOGIC FORMATIONS 



13 



by a higher formation. To the north a fault separates 
the formation from the Pennsylvanian Oquirrh forma- 
tion. Beds included in the Lamb dolomite are found 
at several places on Dutch Mountain, but as it was not- 
practicable to separate them from similar beds in the 
overlying Hicks formation, the two formations were 
mapped together as Upper Cambrian. 

The name is taken from Lamb Gulch, on the north 
side of Dry Canyon, which is underlain by the formation. 

Lithology. — The base of the Lamb dolomite is 
marked by massive beds of light-gray dolomite. These 
are commonly composed of small rounded grains of 
darker dolomite in a matrix of much lighter colored 
dolomite. The size of the grains ranges between 0.5 
and 1 millimeter, and they are thought to have been 
originally oolites, although no concentric structure is 
now discernible. Local concentrations of the darker 
grains in rude lenses essentially parallel to the bedding 
give a characteristically streaked appearance to many 
of the beds. Cross-bedding is commonly shown by 
the supposed oolitic beds. 

Interbedded are layers of pisolitic dolomite. The 
pisolites are rarely circular but usually elliptical in 
section and range in size from 1 to 10 millimeters. 
The larger ones show a poorly defined concentric 
structure, which, with the apparent gradation in size, 
makes it appear probable that the oolitic rocks de- 
scribed in the previous paragraph are really of that 
origin. Locally the pisolites show asymmetric out- 
growths, which, according to W. H. Bradley, 29 of the 
Geological Survey, are similar in size and shape to 
algal growths found by him in pisolitic rocks occurring 
in the Green River formation in Wyoming. The 
matrix is a light-colored dolomite that is, in many 
places, recrystallized and shows shining cleavage faces. 
The pisolites are usually oriented with the longer axis 
parallel to the bedding. The pisolitic and oolitic rocks 
make up the basal 500 feet or so of the, formation and 
recur as thinner zones throughout it. 

The bulk of the formation, however, is composed of 
a light to medium gray dolomite mottled by patches 
of darker dolomite containing white rods, resembling 
closely parts of the Young Peak dolomite. In many 
places the darker dolomite appears to occur as boulders 
in the lighter-colored matrix, but in others the contact 
between the two varieties is indefinite and apparently 
the result of a replacement of the darker variety by the 
lighter. That this is the probable explanation is sup- 
ported by the presence in several places of continuous 
beds of the dark, rod-speckled dolomite. 

Throughout the exposure in the Deep Creek Moun- 
tains the greater part of the formation has been 
recrystallized and bleached to a white resistant dolo- 
mite containing numerous vugs lined with dolomite 



'• Personal communication. 



crystals. Locally, the old texture may be faintly 
discerned on the weathered surfaces, but in most 
places no traces of it remain. 

The top 150 feet of the formation is quite different 
in character from the lower part. Thin-bedded dolo- 
mite with partings of yellow or red sandy shale, to- 
gether with a few massive dolomite beds, compose the 
lower 100 feet or so of this zone. The change from the 
more massive beds is not abrupt. Locally, the thin- 
bedded rocks are dolomitic limestones, and in a few 
places they are essentially limestones. The limestone 
beds resemble somewhat the thin-bedded mottled 
limestones of the Middle Cambrian, except that the 
partings are rather more sandy than shaly. The top 
25 to 50 feet of this zone is made up of a reddish- 
weathering fine-grained sandstone, which is yellowish 
on fresh fracture. It is rather impure, containing 
moderate amounts of mica and dolomite, and is not 
sharply set off from the dolomites below. The sandy 
partings increase in thickness until they form the bulk 
of the rock. The top of this sandstone has been taken 
as the top of the formation. The sandstone is probably 
continuous from the south boundary of the quadrangle 
as far north as the ridge on the north side of Sheep 
Canyon. On the north slope of this ridge, however, 
the bed apparently lenses out and is replaced by 
another sandstone about 100 feet higher stratigraph- 
ically. This higher bed has been mapped as the top 
of the formation for the remainder of the exposure of 
the formation in the Deep Creek Mountains. 

Thickness. — Three measurements of the Lamb dolo- 
mite in the Deep Creek Mountains gave thicknesses of 
1,080, 1,035, and 1,020 feet. These variations may be 
easily explained by changes in strike and dip that are 
concealed owing to poor exposures and by minor 
faulting. The true thickness is probably not far from 
1,050 feet. 

Age and correlation. — As no fossils have been found 
in the formation, its age is not definitely known. It is, 
however, similar in lithology to the overlying forma- 
tion, and the sandstone beds used to delimit the two 
are probably lenticular. This, combined with the 
sharp change in lithology at the base of the formation, 
makes it probable that the age of the Lamb dolomite 
is the same as that of the overlying Hicks formation — 
Upper Cambrian. Because of the lack of fossils the 
Lamb is difficult to correlate with any degree of cer- 
tainty, but it is probably equivalent in age to the 
lower 800 feet of the Mendha formation at Pioche 30 
and the Opex dolomite at Tintic. 31 Beds of similar 
lithology are lacking at the base of the Upper Cambrian 
in both the Eureka and the House Range sections. 



» Westgate, L. Q., Geology and ore deposits of the Pioche district, Nev,: U.S. 
Geo]. Survey Prof. Paper 171, pp. 13-14, 1932. 

»i Loughlin, G, F., Geology and ore deposits of the Tintic mining district, Utah; 
U.S. Geoi. Survey Prof. Paper 107, p. 29, 1919. 



14 



GOLD HILL MINING DISTRICT, UTAH 



HICKS FORMATION (UPPER CAMBRIAN) 

DiMrihution. — The Hicks formation takes its name 
from Hicks Gulch, in North Pass Canyon. This 
locality is near the northern limit of the chief exposure 
of the formation, which extends as a band, made 
discontinuous by transverse faults, east of the divide 
of the Deep Creek Mountains. A small wedge of the 
formation is exposed on the north side of North Pass 
Canyon, north of the fault that limits northward the 
main outcrop. Beds belonging to the formation are 
also found at several places on Dutch Mountain, 
but these beds have been included with the under- 
lying Lamb dolomite and mapped as undifferentiated 
Upper Cambrian. 

Lithology. — The lithology of the Hicks formation is 
in part similar to that of the Lamb dolomite. Oolitic, 
streaked, pisolitic, and mottled dolomites make up a 
large portion of the formation. A specimen of the 
pisolitic type, obtained near the base of the formation, 
is illustrated in plate 5, (7. Some of these beds contain 
tiny nodules of white chert, which are neither abundant 
nor conspicuous. 

In addition to the dolomites, there are several lentic- 
ular beds of sandstone and of limestone, and in one 
place a thin bed of shale was noted. The presence of 
the several rock types and the fact that the limestones 
are abundantly fossiliferous were the main factors in 
separating the formation from the one below. 

The following section, measured on the ridge on the 
north side of Sheep Canyon, is fairly characteristic of 
the formation: 

Section of Hicks formation an north side of Sheep Canyon 

Base of Chokecherry dolomite: Mottled dolomite with 
nodules of black chert, local conglomerates, and cross- 
bedding. 

Hicks formation: j? M ( 

1. Mottled dolomite, locally calcareous 90 

2. Bleached and rccrystallized massive dolomite 33 

3. Sandy shale 38 

4. Bleached and recrystallized massive dolomite 73 

5. Massive oolitic gray dolomite 129 

6. Thin-bedded sandy limestone and calcareous sand- 

stone 79 

7. Thin-bedded sandy dolomite 34 

8. Massive oolitic, pisolitic, and rod-speckled dolo- 

mite 38 

9. Thin-bedded oolitic sandy dolomite 24 

10. Massive oolitic gray dolomite 14 

11. Thin-bedded oolitic sandy dolomite; weathers to 

shades of tan 28 

12. Medium to dark gray cross-bedded streaked oolitic 

dolomite; many pisolitic layers at base; near the 
top are a number of beds of dark dolomite with 

numerous small white rods 173 

Sandstone at .top of Lamb dolomite. 

753 

* Three other sections were measured in the Deep 
Creek Mountains. They are of the same general char- 
acter as the one given above but show that the individ- 



ual beds are extremely lenticular. For example, the 
limestone zone (no. 6 of the section) on the north side 
of Sheep Canyon is 311 feet above the base of the 
formation and 79 feet thick, whereas half a mile to the 
north it is 171 feet thick and starts 215 feet above 
the base, and a little more than a mile to the south it 
was not found at all. 

No sections of the formation were found that were 
free from recrystallized and bleached members such as 
nos. 2 and 4 in the section given above. These occur 
at very different horizons and in varying amounts. 
On the south side of Sheep Canyon, for example, the 
upper 315 feet has been thus altered. Like similar 
beds in the Lamb dolomite, these show throughout 
indistinct remnants of the original texture. 

The upper limit of the formation has been taken as 
the base of the lowest dolomites containing nodules and 
bands of black chert. This zone usually includes local 
dolomite conglomerates and cross-bedded layers. The 
exact contact is difficult to find because of poor expos- 
ures and rather general recrystallization. 

Thickness. — The thicknesses measured were variable, 
ranging from 1,200 foet on the south side of Dry Can- 
yon through 890 and 750 feet on the south and north 
sides of Sheep Canyon, respectively, to 590 feet at the 
head of North Pass Canyon. 

Age and correlation, — Fossils found in one of the 
limestone members at the head of North Pass Canyon 
have been reported upon by Dr. C. E. Eesser, of the 
Smithsonian Institution, as follows: 

M-3. Half a mile east of peak 8135, in North Pass Canyon: 
Pseudagnostus sp. 
Dunderbergia sp. 
Obolus sp. 
20. Ridge line on north side of Dry Canyon: 

Acrotreta sp. 
These suggest a possible correlation with the Secret Canyon 
shale. It represents a lower Upper Cambrian horizon, at any 
rate. 

This horizon is probably unrepresented in the Tintic 
district, where there are less than 400 feet of Upper 
Cambrian beds. The upper part of the Mendha for- 
mation at Pioche 32 is probably of equivalent age. 

UNCONFORMITY AT TOP OF UPPER CAMBRIAN 

The progressive northward thinning of the Hicks 
formation from 1,200 feet to less than 600 feet in a 
distance of Z% miles indicates a pronounced uncon- 
formity at its top. The basal Ordovician beds show 
local dolomite conglomerates and abundant shallow- 
water phenomena, such as cross-bedding. No sand- 
stone, however, has been recognized as being at the 
contact. The only criterion that was found of assist- 
ance in the mapping is the universal occurrence of 
dark chert in the Ordovician sediments. 



>» Westgate, L. O., Geology and ore deposits of the Pioche district, Not.: C8. 
Qeol. Survey Prof. Paper 171, pp. 13-14, 1932, 



ORDOVICIAN SYSTEM 



15 



The presence of an erosional unconformity at the 
base of the Ordovician has not been generally recog- 
nized in the Great Basin region. In the Tintic 
district 33 one was recognized but considered to be of 
only local significance. Earlier Kiehardson 34 had 
described an unconformity at this horizon in the 
Randolph quadrangle, in northern Utah, resulting in 
the removal of over 800 feet of Upper Cambrian beds. 
In the House Eange and at Eureka, Nev,, however, 
Waleott has considered the Ordovician to overlie the 
Upper Cambrian conformably, and in a general 
review of the subject 35 he notes that the Upper Cam- 
brian formations in the Cordilleran region pass into 
the overlying beds without apparent stratigraphic 
break. 

The proof of a definite erosional unconformity at 
the top of the Upper Cambrian in three localities so 
widely separated as the Tintic district, northern Utah, 
and Gold Hill, however, seems to indicate that it is 
more than a local occurrence, and it is probable that 
future work, with carefully measured sections, will 
show that the unconformity is of wider extent than is 
now recognized. 

ORDOVICIAN SYSTEM 
CHOKBCHIREY DOLOMITE (LOWER ORDOVICIAN) 

Distribution. — The Chokecherry dolomite, named 
after Chokecherry Canyon, just beyond the south edge 
of the quadrangle, crops out in the Deep Creek 
Mountains, where it is exposed as a discontinuous 
band, of variable width, as far north as North Pass 
Canyon. South of the pass at the head of Dry 
Canyon, where the base of the formation is just east of 
the crest of the range, its width is about three-quarters 
of a mile, owing to the fact that the surface slope is 
nearly equal to the dip of the beds. The wide outcrop, 
most of which lies west of the crest, is terminated by a 
transverse fault in Dry Canyon. North of the fault 
the outcrop lies east of the crest and is much narrower, 
a quarter of a mile being the maximum width, A few 
transverse faults offset its northerly course, and it is 
finally terminated by a large transverse fault in North 
Pass Canyon. The formation is absent on Dutch 
Mountain, where Upper Ordovician dolomite rests 
upon beds of Upper Cambrian age. 

Lithology. — The Chokecherry dolomite is charac- 
terized by the presence of considerable silica, found 
both as nodules and as layers of chert, usually dark- 
gray to black, and as sandy laminae between thin beds 
of dolomite. The lower beds are, as a rule, rather 
massive dark mottled dolomite, locally oolitic and 



» Loughlin, Q. F., Geology and ore deposits of the Tintic raining district, Utah: 
U.S. Oeol. Survey Prof. Paper 107, p. 80, 1919. 

« Richardson, O. B,, The Paleozoic section in northern Utah: Am. Jour. Soi., 
4th aer., vol. 36, p. 408, 1913. 

"Waleott, C. D., The Cambrian and its problems, in Problems of American 
geology, p, 191, Yale University Press, 1915. 



cross-bedded and containing thin lenses of dolomite 
conglomerate. Small black chert nodules are found 
throughout. These beds are supplanted higher in the 
formation by thinner-bedded dolomite with sandy 
laminae, or locally by bands of dark chert. In a few 
places the laminae become sufficiently thick to form 
lenses of sandstone. One bed, near the top of the 
formation, that has been found to be continuous in the 
southern part of the exposure in the Deep Creek 
Mountains is a light-gray dolomite filled with siliceous 
concretions about the size and shape of a gooseberry. 

The formation has been particularly susceptible to 
the bleaching and recrystallization that has affected 
the two lower formations, described above. In most 
of the sections examined between a third and a half of 
the formation has been thus altered. 

This alteration, combined with poor exposures of the 
thin-bedded dolomites at the top of the formation, 
makes the determination of the upper boundary un- 
certain. Where best exposed the basal beds of the 
overlying Fish Haven dolomite are seen to be medium 
thick bedded dolomites, free from the sandy laminae of 
the lower dolomites and containing but little chert. In 
mapping, therefore, the boundary was placed at the top 
of the highest sandy or cherty float. 

Thickness. — The formation shows a rather notable 
variation in thickness from the southern part of the 
quadrangle northward. On the south side of Dry 
Canyon at least 1 ,000 feet is exposed ; on the north side 
of Sheep Canyon, 890 feet; and at the head of North 
Pass Canyon, 850 feet. On Dutch Mountain the 
Chokecherry dolomite is absent, and dolomite of Upper 
Ordovician age rests upon Upper Cambrian dolomite. 

Age and correlation. — Scanty fossil collections made 
by Edwin Kirk, of the Geological Survey, have been 
determined by him as follows: 

TN-26 37. East of saddle on ridge between peaks 85150 and 
8350, on north side of Dry Canyon, and also on ridge line of 
peak 8491, at head of Dry Canyon. Scaevogyra? sp. 

The few gastropods in this lot do not permit exact age 
determination, and as yet we know of no other horizon with 
which it may be correlated. It may safely be considered 
early Lower Ordovician, however. 

Rocks of Lower Ordovician age are found in many 

places in the Great Basin. In each area, however, the 
lithology is, as a rule, markedly different from that of 
neighboring areas, and the only reliable method of 
correlation is by means of the contained fossils. The 
fossil evidence indicates that the Chokecherry dolo- 
mite represents only a portion of Lower Ordovician 
time. As in other districts higher beds may be present, 
exact equivalents are difficult to determine, but in 
general the Chokecherry dolomite may be considered 
of about the same age as the Ajax and Opohonga lime- 
stones at Tintic, 36 the Garden City limestone in the 

'» Loughlin, Q. P., Geology and ore deposits of the Tintic mining district, Utah: 
U.S. Oeol. Survey Prof. Paper 107, pp. 31-33, 1919. 



16 



GOLD HILL MINING DISTEICT, UTAH 



Randolph quadrangle," the Yellow Hill limestone at 
Pioehe, 38 part of the Grampian limestone in the San 
Francisco region, 39 and the basal part of the Pogonip 
limestone of the Eureka district.* 

UNCONFORMITY AT BASE OF UPPER ORDOVICIAN 

The variable thickness of the Chokeeherry dolomite 
in the Deep Creek Mountains and its apparent absence 
on Dutch Mountain indicate an unconformity between 
it and the overlying Fish Haven dolomite, of Upper 
Ordovician age. Further evidence of an unconformity 
is indicated by the presence in the southern part of 
the range of a Lower Ordovician fauna that resembles 
that of a higher formation than the beds found within 
the quadrangle ; 41 and on the reported presence to the 
south of a quartzite that is apparently equivalent to 
the Eureka quartzite found in the Middle (?) Ordo- 
vician of Nevada. 42 

This unconformity has been reported from three 
other localities — Eureka, Nev., 43 northern Utah, 4 * and 
southeastern Idaho. 45 In all three the unconformity is 
shown by the varying thickness of an underlying 
quartzite, which is, in the Utah and Idaho localities, 
of Chazy (?) age. The quartzite in Nevada, is probably 
of about the same age. The hiatus represented by the 
unconformity is thus much greater at Gold Hill than 
it is to the north or south, but whether the absence of 
the high Lower Ordovician beds is due to erosion or to 
nondeposition is not clear. The latter hypothesis is 
perhaps more probable, in view of the lack of conglom- 
erate or other clastic rocks at the base of the Upper 
Ordovician sediments. 

At Eureka and in the northern Utah area the uncon- 
formity is shown by the varying thickness of an under- 
lying quartzite which is of Chazy (?) age in the Utah 
locality but is unfossiliferous at Eureka. In south- 
eastern Idaho the quartzite of Chazy (?) age appears 
to lie conformably beneath the Fish Haven, but a 
considerable time break is required by the absence of 
beds containing faunas that in other localities intervene 
between the rocks of Chazy age and those of Fish 
Haven age. 



" Richardson, G. B„ The Paleozoic section in northern Utah: Am. Jour. Sci. 
4th ser., vol. 36, p. 408, 1913. 

«» Westgate, L. Q., Geology and ore deposits of the Pioehe district, Nev.: U.S 
Geol. Survey Prof. Paper 171, p. 14, 1932. 

«» Butler, B. S., Geology and ore deposits of the San Francisco region, Utah; 
U.S. Geol. Survey Prof. Paper 80, p. 30, 1913, 

«« Hague, Arnold, Geology of the Eureka district, Nev.: U.S, Geol. Survey Mod. 
20, p. 13, 1882. 

" Butler, B. S., Ore deposits of Utah: U.S. Geol. Survey Prof. Paper 111, p. 471, 
1920. 

<> Reagan, A. B., Geology of the Deep Creek region, Utah: Salt Lake Min. Rev., 
vol. 19, June 30, 1917, p. 25. 

« Hague, Arnold, Geology of the Eureka district, Nev.: U.S. Geol. Survey Mon, 
20, p. m, 1892. 

" Richardson, G. B., The Paleozoic section in northern Utah: Am. Jour. Sei. 
4th ser., vol. 36, p. 40S, 1913. 

*' Mansfield, G. E., Geology and geography of southeastern Idaho: U.S. Geol. 
Survey Prof. Paper 152, p. 58, 1927. 



ETSII HAVEN DOlDOMrrB (UPPER ORDOVICIAN) 

Distribution. — The Fish Haven dolomite crops out 
as a narrow band underlying the massive Laketown 
dolomite in the Deep Creek Mountains as far north 
as North Pass Canyon. In this region it is in general 
poorly exposed, being covered by the debris from the 
resistant formation above. Outcrops of the formation 
also occur at three places on Dutch Mountain — on the 
southeast flank, from Pool Canyon to the south side 
of the canyon in which the Spotted Fawn mine is 
located; on the north flank, in Royal Gulch; and on 
the northwest flank, in the lower foothills. In these 
three localities the formation, although cut by num- 
erous faults, is much better exposed than in the 
southern part of the quadrangle. 

The name "Fish Haven" is that given by Richard- 
son 46 to rocks of similar age and lithology in northern 
Utah. 

Lithology. — The Fish Haven dolomite is composed of 
moderately thick to thick-bedded dolomite, usually 
dark gray, with but little chert. On Dutch Mountain 
lighter-colored beds are found in the middle part of the 
formation, but the color is, in part at least, due to 
bleaching. In general the mottling and other textural 
features so abundant in the formations above and 
below are lacking, but several beds show lighter gray 
splotches in a matrix of dark gray. Some beds also, 
near the top of the formation, contain vugs filled with 
white crystalline dolomite. On Dutch Mountain the 
basal bed is characterized by numerous small silicified 
brachiopods (Bhynchotrema argenturbica) , which great- 
ly simplify the mapping of the boundary. This bed 
was not found in the Deep Creek Mountains, 

The lower contact is well exposed on Dutch Moun- 
tain and at a few places in the Deep Creek Mountains. 
This contact is irregular in detail, but nowhere could 
it be shown that any notable amount of the Hicks for- 
mation had been removed before the deposition of the 
Fish Haven. Locally the basal beds of the overlying 
Laketown dolomite are dolomite conglomerates, but in 
most places they are dolomite sands, with wavy bed- 
ding planes and numerous fragments of Silurian corals 
and brachiopods. 

Thickness. — The thickness of the formation is sur- 
prisingly constant over the whole area. On Dutch 
Mountain 278 feet was found, on the ridge between Dry 
Canyon and Sheep Canyon 253 feet, and at two other 
poorly exposed localities in the Deep Creek Mountains 
about 250 feet. 

Age and correlation. — Fossil collections were made 
both on Dutch Mountain and in the Deep Creek 
Mountains. They have been identified by Edwin 



« Klehardson, G. B., The Paleozoic section in northern Utah: Am, Jour. Sci., 
4th ser., vol. 36, pp. 409-410, 1913. 



SILTJBIAN SYSTEM 



17 



Kirk, who assigns them to the Upper Ordovician, 
His report is as follows: 

TN-26 33. 1 mile south of peak 7800 of Dutch Mountain, 
about 3 miles north of Gold Hill: 

Halysites gracilis (Hall), 
Streptelasma trilobatum Whiteaves. 
Calapoecia of. C. antieostiensis Billings. 
Rhynchotrema capax Conrad. 
Rhynehotrema argenturbica (White) . 
Dinorthis eubquadrata Hall. 
Zygospira recurvirostriss (Hall). 

TN-26 36. Just west of saddle between peaks 8550 and 
8359 on ridge on north side of Dry Canyon near head: 

Streptelasma trilobatum Whiteaves. 
Streptelasma sp. 
Columnaria sp. 

This horizon is correlative with the upper portion of the 
Montoya limestone of Texas and New Mexico, the Fish Haven 
limestone of northern Utah, and the upper portion of the Big- 
horn dolomite of Wyoming. Rocks of equivalent age occur in 
the lower part of the Lone Mountain limestone of the Eureka 
district. 

The upper part of the Bluebell dolomite at Tintie 4J 
is also of this age, as is the Ely Springs formation at 
Pioche, Nev. 4S 

DNCONPOBMrry at top of upper okdoviciak 

In the Gold Hill quadrangle there is little physical 
evidence of an unconformity between the Fish Haven 
dolomite and the overlying Laketown dolomite. 
The Fish Haven is remarkably constant in thickness 
throughout the area, and the dolomite conglomerate 
and wavy contact found at the base of the Laketown 
dolomite are no better defined than similar features 
within many of the lower Paleozoic formations. Fur- 
ther, the regional variation in thickness of Upper 
Ordovician sections that are overlain by Silurian beds 
is relatively slight. For example, the thickness at 
Pioche, Nev., is 525 feet; at Gold Hill, 260 feet; 
and in the Bandolph quandrangle, Utah, 500 feet. In 
no one of these localities, moreover, does there seem 
to have been any notable amount of erosion before 
middle Silurian time. The absence of late Upper 
Ordovician and early Silurian faunas at all these locali- 
ties, however, implies that there has been a consid- 
erable hiatus in sedimentation throughout this region. 

SIIUEIAH SYSTEM 

LAKETOWN BOLOMITB 

Distribution. — The Laketown dolomite crops out 
prominently in the Deep Creek Mountains, forming 
the crest of the range from Dry Canyon north to North 
Pass Canyon, The width of this outcrop varies 
greatly, owing in part to the approximate coincidence 
of the dip of the beds and the slope of the surface west 



« Loughlin, O. F., Geology and ore deposits of the Tintie mining district, Utah: 
TJ.S. Owl. Surrey Prof. Paper 107, p. 35, 1919. 

'i Westgate, L. O., Geology and ore deposits of the Pioche district, Nev.: TJ.S. 
Geol. Survey Prof. Paper 171, p. 16, 1B32. 



of the crest. South of Dry Canyon the formation 
is found entirely on the western flank of the range, 
where it forms the 7,662-foot hill between the forks 
of Simonson Canyon. A narrow band is present on 
the north side of North Pass Canyon. It is terminated 
both to the north and south by faults. Two small 
outcrops partly surrounded by gravel are also exposed 
on the southern flanks of Blood Mountain. 

On Dutch Mountain the formation is exposed over- 
lying the Fish Haven dolomite from Pool Canyon 
on the south to Spotted Fawn Canyon on the north. 
It is also present in Royal Gulch and in the foothills 
of the northwestern slope of Dutch Mountain. 

The name of the formation is the same as that used 
by Richardson 4 * for rocks of similar age in north- 
eastern Utah. 

Lithology. — The lower half of the Laketown dolomite 
is dark gray, rather massively bedded, and notably 
fossiliferous. Much of the rock is mottled or lam- 
inated, and such beds contain intraformational con- 
glomerates. The appearance of these conglomerates 
was so striking that in the field they were distinguished 
by the name "marble cake" dolomite (pi. 5, D). 
Sections of a pentameroid brachiopod (Virgiana sp.) 
may be found throughout this zone, and one persist- 
ent bed, about 100 feet above the base, is largely made 
up of this fossil. 

Above this dark dolomite is 350 to 400 feet of 
medium-gray massive dolomite. This zone is almost 
lacking in fossils and has none of the textural features 
so abundant in the lower beds. Most of the beds are 
rather coarsely crystalline, and a few contain vugs 
filled with white, well-crystallized dolomite. 

This zone is overlain by another of massively bedded 
dark-gray to black dolomite, which also shows no un- 
usual texfural features except local thin chert stringers. 
It contains abundant fossil corals, which are locally 
silieified. This zone is about 150 to 200 feet thick. 
Above it from Sheep Canyon southward is a medium 
to light gray coarsely crystalline dolomite, which 
locally contains a bed crowded with large brachiopods 
of the genus TrimereUa. This dolomite is not found 
to the north. 

The upper contact of the formation is unconform- 
able, the basal beds of the overlying Sevy dolomite 
clearly occupying depressions in the Laketown dolo- 
mite and resting upon successively lower beds of the 
Silurian northward. The top light-gray member, as 
noted above, is not present in the northern exposures 
of the formation in the Deep Creek Mountains. 

Thickness. — A section of the formation measured on 
the ridge between Dry Canyon and Sheep Canyon was 
970 feet thick. No other satisfactory measurements 
of the thickness were made, because of the presence of 
strike faults or because of poor exposure; but it is 



" Richardson, O. B., Paleozoic section in northern Utah: Am. Jour. Sol., 4th ser., 
vol. 38, p. 410, 1913. 



18 



GOLD HILL MINING DISTRICT, UTAH 



thought that the limits for the thickness in the Deep 
Creek Mountains within the quadrangle are 1,200 and 
850 feet. No estimate of thickness on Dutch Mountain 
can be made, for the top is nowhere exposed, a fault 
contact with the Mississippian being found at all 
points. 

Age and correlation. — The Laketown dolomite is 
abundantly fossiliferous throughout. Collections were 
made at various horizons, and these have been reported 
upon by Edwin Kirk as follows: 

M4. About 100 yards due east of peak 8135, on south side of 
North Pass Canyon. 544 feet above base of formation: 
Halysites oatenularia (Lin- I Zaphrentis sp. 

naeus). | Favosites sp. 

M13. Near head of Sheep Canyon, on north side, about 150 
feet below top of formation: 

Sections of brachiopod, probably Trimerella sp. 

TN-26 22. Three-quarters of a mile north of peak 8550, 
Sheep Canyon, near base of formation: 
Virgiana? sp. 

TN-26 32. Crest of peak 8135, at head of North Pass 
Canyon: 



oatenularia (Lin- 



Syringopora, 2 sp. 
Zaphrentis sp. 
Favosites sp. 



Halysites 

naeus) . 
Halysites, 2 sp. 
Coenites sp. 

TN-26 34. Slope half a mile south of peak 8291, on north 
side of Sheep Canyon: 
Halysites oatenularia (Lin- Trimerella sp. 

naeus) . 

TN-26 35. South slope of peak 8550 on north side of Dry 
Canyon, near head: 
Halysites oatenularia (Lin- Zaphrentis, 2 sp, 

naeus). Favosites sp. 

Halysites sp. Virgiana? sp. 

Syringopora, 2 sp. 

TN-26 39. 1 mile south-southeast of peak 7800, Dutch 
Mountain: 



Favosites sp. (digitate form). 
Zaphrentis sp. 



Amplexus sp. 
Heliolites sp. 



TN-26 40. 4,500 feet east-northeast of peak 8135, North 
Pass Canyon: 

Favosites sp. (digitate form). I Heliolites sp. 
Zaphrentis sp. | 

Gray dolomite above typical Silurian on ridge at head of 
south branch of Sheep Canyon, half a mile northwest of peak 
8550: 

Huronia sp. 

This formation may be considered of Niagaran age. It is 
correlative in part with the Fusselman limestone of Texas and 
New Mexico, the Laketown dolomite of northern Utah, and 
probably the upper portion of the Lone Mountain limestone of 
the Eureka district. 

UNCONFORMITY BETWEEN SILURIAN AND DEVONIAN 

The truncation of beds at the top of the Laketown 
dolomite, as shown by the disappearance northward of 
the upper light-gray, coarsely crystalline member, and 
the local presence, in the basal Devonian formation, of 
conglomerate containing pebbles of the underlying 
Silurian formation, leave little doubt that there is a 



pronounced unconformity between the Laketown dolo- 
mite and the Sevy dolomite. An unconformity at this 
point has not previously been reported from the Great 
Basin or adjacent regions, chiefly because sediments of 
either Silurian or Devonian age or both are commonly 
lacking. Both series have been reported from three 
localities in Utah and Nevada — the Randolph quad- 
rangle, Utah, 80 Pioche, Nev.," and Eureka, Nev. 62 
In the Randolph quadrangle the succession is said to 
be apparently conformable; at Pioche the two are not 
in contact; and at Eureka the contact is gradational. 
It would thus appear that the unconformity in the 
Gold Hill quadrangle is local in extent, but it is perhaps 
significant that no late Silurian faunas have been 
reported from either Eureka or the Randolph 

quadrangle. 

DEVONIAN SYSTEM 

SEVY DOLOMITE (MIDDIjE DEVONIAN) 

Distribution. — The Sevy dolomite, named from 
Sevy Canyon, is exposed only in the Deep Creek 
Mountains, generally being found on the west flank of 
the range. The most southerly exposure is in the south 
branch of Simonson Canyon, on the southern boundary 
of the quadrangle. This is of small extent and is sepa- 
rated on the north from the Laketown dolomite by a 
northwestward-striking fault. Outcrops occur also in 
the north branch of Simonson Canyon, on the north 
side of the Dry Canyon transverse fault. From this 
place the formation extends, with only minor inter- 
ruption by faulting, in a direction a little east of north. 

Lithology. — The Sevy dolomite is remarkably homo- 
geneous throughout the area of outcrop. The typical 
rock is a well-bedded mouse-gray dolomite in layers 6 
to 12 inches thick and weathers to a very light gray. 
It is of extremely dense texture and has a conchoidal 
fracture. In most of the beds a faint lamination 
parallel to the bedding is visible, in part at least, 
because of slight differences in color in adjoining 
laminae. A few beds of darker dolomite occur near 
the top of the formation, and locally there are present 
beds containing tiny nodules of light-colored chert. 

The basal beds show the only notable variations in 
character from the main mass of the formation. The 
lower 30 feet includes in most places lenticular beds 
from 1 to 5 feet thick of medium gray, rather coarse 
grained dolomite sand, which is similar in color and 
texture to the top member of the Laketown dolomite. 
Some of these lenses contain numerous pebbles or 
boulders of dolomite. Some of the boulders are sub- 
angular in outline and consist of dark dolomite similar 
in lithology to various beds of the Laketown dolomite. 
The greater number, however, are sharply angular 



M Richardson, O. B., Paleozoic section in northern Utah: Am, Jour. Set, 4th ser., 
vol. 36, p, 411, 1913. 

« Westgate, L. O,, Geology and ore deposits of the Pioche district, Nev.: U.S. 
Oeol. Survey Pro!. Paper 171, pp. 16-19, 1932. 

5 » Hague, Arnold, Geology ol the Eureka district, Nev.: U.S. Oeol. Survey Mori, 
20, p. 63, 1802. 



DEVONIAN SYSTEM 



19 



thin wedges or blocks of a light-gray dolomite identical 
with the enclosing beds. The lamination of the pebbles 
shows that they have been considerably rotated. The 
apparent anomaly of a conglomerate containing 
boulders of the younger rock in a matrix of material 
from the older rock may perhaps be explained as 
follows: The waters in which the Sevy dolomite was 
deposited were part of an advancing shallow sea, 
which was, at the locality and time represented by 
these sediments, just beginning to spread over the older 
rocks. Occasional severe storms broke up the partly 
consolidated sediments just deposited and at the same 
time swept in abundant fine-grained debris and a few 
larger boulders from the nearby shore composed of 
Silurian rocks. On the cessation of the storm, the 
material was deposited, and the resulting rock was 
similar to the material here described. 

Thickness. — On the north side of Sevy Canyon the 
formation is 450 feet thick. The rocks here are well 
exposed and apparently not faulted. On the north 
side of Simonson Canyon 800 feet of beds were meas- 
ured. The formation at this place is poorly exposed, 
however, and there may be some repetition of beds by 
faulting. Some variations in thickness are to be 
expected in an overlapping formation such as the Sevy 
dolomite, and the difference of 150 feet between the 
two measurements may be a difference in original 
deposition. 

Age and correlation. — The only fossils found in the 
Sevy dolomite wore small crinoid stems at a few 
horizons and several poorly preserved gastropods near 
the base. None of these, according to Edwin Kirk, 
w r ho examined the formation in the field, are suffi- 
ciently diagnostic for determination of age. The for- 
mation grades into the overlying Simonson dolomite, 
which contains a Middle Devonian fauna. The Sevy 
dolomite is therefore considered to be Devonian and 
probably Middle Devonian. 

SIMONSON DOLOMITE (MIDDLE DEVONIAN) 

Distribution. — The Simonson dolomite, named from 
Simonson Canyon, on the west side of the Deep Creek 
Mountains near the southern boundary of the quad- 
rangle, is exposed chiefly in these mountains. The 
only complete sections are found on the west side of the 
range, where the formation overlies the Sevy dolomite 
and is of similar extent. Smaller outcrops composed of 
portions of the formation occur at three other places. 
The largest of these is on the north side of North Pass 
Canyon, where, south of a large fault separating lower 
Paleozoic from Pennsylvanian rocks, a few hundred 
feet of the Simonson dolomite rests, with fault contact, 
upon beds of the Laketown dolomite. A smaller area 
of the formation is located in North Pass Canyon a 
quarter of a mile west of the branch road leading up 
Bagley Gulch. This is surrounded by gravel. A 
small exposure is also found on the north side of Dutch 
Mountain. 



Lithology. — The base of the formation was placed at 
a dark crystalline dolomite, on the weathered surfaces 
of which may be seen thin discontinuous laminae of 
brown sandy material. The bed is strikingly lami- 
nated, a feature which is characteristic of the whole 
formation. Below this horizon there are a few dark- 
gray dolomites, and above it there are a few light-gray 
dolomites similar to those characteristic of the Sevy 
dolomite. The contact between the two formations is 
merely a change in the proportions of light and dark 
gray dolomites and does not indicate any time break. 

The typical rock of the Simonson is a dark to medium 
gray dolomite in which the individual grains are large 
enough to be distinguished by the unaided eye. Indi- 
vidual beds are from 1 to 2 feet thick. The most 
striking feature is the very general presence of a fine 
lamination, caused chiefly by variations in the amount 
of darker pigment present in the laminae and to a much 
less degree by variations in the grain size. The laminae 
are in general extremely irregular in detail, much of 
this irregularity being clearly the result of original 
variations in deposition. Locally the irregularities are 
even more pronounced (pi. 5, E), and these are thought 
to have been caused by subsurface solution and sub- 
sequent slumping during the time the formation was 
being deposited. 

The following section of the formation was measured 
on the north side of Sevy Canyon and is typical of the 
formation in the area. 

Section of Simonson dolomite on north side of Sevy Canyon 

Dolomite conglomerate (base of Guilmette formation) . 
Simonson dolomite: *■«' 

Medium- and dark-gray laminated dolomite, in beds 

1 to 2 feet thick, locally coarsely crystalline 329 

Light-gray sandy laminated dolomite; includes two 
thin layers of dark -gray dolomite and a 3-foot bed 
of dolomite conglomerate 75 feet above the base. 96 

Dark-gray laminated dolomite 56 

Medium- and light-gray sandy dolomite 52 

Dolomite conglomerate 6 

Covered; probably largely laminated dolomite 170 

Medium- and dark-gray laminated dolomite with a 
few thin light-gray beds near base; at base dark 
dolomite 3 feet thick containing thin laminae of 

brown sandstone 254 

Light-gray dolomite of Sevy dolomite. 

963 

The two dolomite conglomerates in the above section 
apparently have little significance, as they cannot be 
found everywhere in the area. A similar conglomerate 
which is continuous, however, has been used to desig- 
nate the base of the next higher formation. Its con- 
tinuity is proved by the fact that it is found at the same 
distance below a distinctive fossiliferous bed through- 
out the area. Above this conglomerate the lithology is 
distinctly different from that of the Simonson dolomite, 
although the fossil evidence indicates that but little 
time difference is represented. 



20 



GOLD HILL MINING DISTRICT, UTAH 



Thickness. — In addition to the measurement ob- 
tained in Sevy Canyon, a second measurement was 
made on the north side of Kelly Canyon, where the 
thickness was found to be 1,030 feet. The difference 
of 70 feet between the two probably represents errors in 
measurement due to poor exposures and minor fault- 
ing rather than to original variations of deposition. 

Age and correlation. — Fossils are not abundant in the 
Simonson dolomite, except for small spherical Stro- 
matopora-like corals. These are usually not more than 
an inch in diameter and are found in large numbers in 
certain bads. Three small lots were collected, upon 
wiiieh Mr. Kirk reports as follows: 

Three-quarters mile north-northwest of South Peak, on north 
side of Sevy Canyon: 

Pavosites (digitate form). 
Bellerophon sp. 

Stringoeephalus burtoni Defrance. 
Martinia cf. M. meristoides Meek. 
Atrypa reticularis Linnaeus. 

M4C. North side of Simonson Canyon near mouth: 
Atrypa reticularis Linnaeus. 

TN-26 21. Half a mile north of Dewey prospect, on north 
side of Sevy Canyon: 

Pavosites (digitate form). 

The formation is probably correlative with the Nevada lime- 
stone of the Eureka district in part. The horizon, by virtue of 
the Stringoeephalus, may accurately be placed as high as 
Middle Devonian. 

CiUILMETTE FORMATION (MI1WJLM DEVONIAN) 

Distribution. — The Guilmette formation, named 
after Guilmette Gulch, on the west side of the Deep 
Creek Mountains, forms the westernmost exposures of 
the range from Simonson Canyon northward to Sheri- 
dan Gulch, except for a few small areas occupied by the 
younger Woodman formation. The best exposure of 
the formation is on the north side of Sevy Canyon. 
The area covered by the formation is not continuous, 
being interrupted by three large transverse faults; and 
in the north it is further affected by warping and minor 
folding. In addition several small areas along the 
Lincoln Highway in the pass between the Deep Creek 
Mountains and Ochre Mountain are underlain by 
crumpled and crushed beds similar to those of the 
Guilmette. Another exposure that is thought to 
belong to this formation occurs on the north side of 
North Pass Canyon about half a mile east of the 
junction of the road from Bagley Gulch with the main 
road up the canyon. On the east edge of the quad- 
rangle near the southern boundary there are outcrops 
of highly brecciated rock similar to this formation in 
lithology and, in some places, in fossil content. Some 
scattered outcrops on the north side of Dutch 
Mountain are also believed to belong in the Guilmette 
formation. 

Lithology. — The Guilmette formation is composed 
chiefly of dolomite but contains also some thick lime- 



stone beds and several lenticular sandstones. The 
dolomites for the most part differ in character from 
those found in the Simonson dolomite, although a few 
laminated beds are present near the bottom of the 
formation. The most abundant variety is a fine- 
grained dolomite, dark to medium gray on fresh 
fracture and weathering to lighter shades of gray, that 
contains numerous vugs almost completely filled with 
white coarsely crystalline dolomite. Less abundant 
but far more striking in character is a dark dolomite 
filled with fragments of tubular corals. Most of these 
beds contain a coral of small diameter {Cladopora sp.), 
but some are filled with a larger, branching variety 
(Siriaiopora sp.). So far as known these coralline beds 
are limited to this formation. 

The limestones are different from any found lower 
in the section. They are massively bedded, dense 
rocks that are light brownish gray on fresh fracture 
but weather to shades of bluish gray. The weathered 
surface is characteristically splotched with a tan dis- 
coloration. Fossils have not been found in such beds. 
The sandstone beds form a comparatively small por- 
tion of the formation, but the brownish color they 
assume on weathering makes them conspicuous. They 
are fine-grained and are thoroughly cemented by dol- 
omite or calcite. 

The following section, measured on the north side 
of Sevy Canyon, illustrates the interbedding of the 
various lithologic types: 

Section of Guilmette formation on the north side of Sevy Canyon 

Sandstone and limestone of Woodman formation. 

Guilmette formation: Feet 

1. Limestone, massively bedded; weathers to a light 

bluish gray splotched with tan 20 

2. Dolomite, dark gray, coralline „ 2 

3. Limestone, like no. 1 10 

4. Sandstone, light gray on fresh fracture; weathers 

brown 15 

5. Limestone, like no. 1 30 

6. Dolomite, dark and medium gray, fine-grained; 

contains numerous vugs almost completely filled 
with white coarsely crystalline dolomite 31 

7. Sandstone, like no. 4 6 

8. Dolomite, like no. 6; includes a few thin layers like 

no. 2 46 

9. Dolomite, dark gray, filled with Siriaiopora 3 

10. Dolomite, like no. 6 25 

11. Dolomite, like no. 9 6 

12. Dolomite, like no. 6 28 

13. Sandstone, like no. 4 6 

14. Dolomite, like no. 6 14 

15. Sandstone; weathers brown, dolomitic 3 

16. Sandy dolomite, medium gray; poorly exposed 29 

17. Dolomite, dark and medium gray, mottled; a few 

vugs filled with white coarsely crystalline dolo- 
mite; poorly exposed 34 

18. Limestone, like no. 1 10 

19. Limestone, thinner-bedded, including a few thin lay- 

ers of dark-gray dolomite 26 

20. Limestone, light gray, mottled with dark-gray dol- 

omite splotches ~.„ 27 



DEVONIAN SYSTEM 



21 



Section of Guilmette formation on the north side of Sevy Canyon — ■ 
Continued 

Fat 

21. Dolomite, dark gray; includes lighter-gray dolo- 

mite conglomerate 21 

22. Dolomite, medium gray, finely laminated 26 

23. Dolomite, like no. 17 6 

24. Limestone, like no. 1 10 

25. Dolomite, like no. 17 63 

26. Dolomite, bleached and brecciated — 60 

27. Limestone, like no. 1, poorly exposed 78 

28. Dolomite, like no. 17 32 

29. Limestone, like no. 1 9 

30. Limestone, dolomitic; poorly exposed 22 

31. Dolomite, like no. 22 3 

32. Limestone, like no. 1; poorly exposed 9 

33. Sandstone, like no. 4 14 

34. Dolomite, like no. 22 58 

35. Dolomite, medium gray, full of sections of Stringo- 

cephalus burtoni 4 

36. Dolomite, like no. 17, with thin zone like no. 9, 30 

feet above base 78 

37. Dolomite conglomerate 24 

Laminated dolomite of Simonson dolomite. 

888 

The upper contact of the formation is well exposed 
on the north side of Sevy Canyon, where a thin bed of 
bluish-gray limestone containing abundant Carbonifer- 
ous fossils overlies massive unfossiliferous limestone 
similar to those found throughout the Guilmette for- 
mation. No angular discordance or clastic beds were 
distinguished at the contact. 

Thickness, — Three measurements of the thickness of 
the formation were made. One on the north side of 
Simonson Canyon showed 1,400 feet and did not in- 
clude the uppermost beds. A second, on the south 
side of Sevy Canyon, showed 1,200 feet; and a third, 
given in detail in the preceding section, 888 feet. All 
three of the sections measured are cut by numerous 
small faults. Allowance was made for the displace- 
ments caused by many of these faults, but it is not 
improbable that some escaped detection. The greater 
part of the variation in thickness, however, is due to 
an unconformity at the top of the formation. 

Age and correlation. — Fossil collections were made 
at different horizons in the formation. Edwin Kirk, 
who participated in the collecting, reports on them as 
follows: 

TN-26 25. One mile east of southeast corner of sec. 13, T* 
9 S., E. 19 W.: 

Stringocephalus burtoni Defrance. 
TN-26 38. Three-fourths of a mile north-northwest of South 
Peak: 

Stringocephalus burtoni Defrance. 
Atrypa reticularis Linnaeus. 
M"-5.- South side of Sevy Canyon: 

Stringocephalus burtoni Defrance. 

These three lots came from beds equivalent to no. 
35 in the section above. The two following lots are 
somewhat higher. 



M-4B. North side of Simonson Canyon, about 2 miles south- 
east of Simonson ranch: 

Favosites (digitate form). 

Syringopora sp. 

Atrypa reticularis Linnaeus. 
M-6. South side of Sevy Canyon: 

Atrypa reticularis Linnaeus. 

Martinia meristoides Meek. 

The next two lots were obtained from limestone 
beds near the top of the formation, 

TN-26 31. About 1 mile southwest of hill 6634, on west side 
of Ochre Mountain: 

Pycinodesma? sp. 
North side of Sevy Canyon: 

Flatysehisma? cf. P. mccoyi Walcott. 
Cyelonema? sp. 
Pycinodesma? sp. 

Mr. Kirk further reports: 

In the formation occur large numbers of Cladopora sp., which 
has a very widespread distribution throughout the Western 
States, being found in the Jefferson limestone of Montana and 
ranging south into Nevada. It is readily recognized by its 
small size, seldom being over 2 millimeters in diameter. Asso- 
ciated with this is a branching coral probably referable to 
Striatopora, which often forms a network on some of the sur- 
faces. Occasional heads of " Stromatopora", ranging in size 
up to 3 or 4 inches in diameter, are found. 

The formation is probably correlative with the Nevada lime- 
stone of the Eureka district in part. The horizon by virtue 
of the Stringocephalus may accurately be placed as high as 
Middle Devonian. 

TJKCONFOKMITT AT BASE OF CABBONIFEROtJS 

The only exposures of the contact between the 
Mississippian and the Devonian that are not com- 
plicated by faulting are north and south of Sevy 
Canyon. There is little physical evidence in either of 
these places for the presence of an unconformity. 
Three bits of indirect evidence, however, indicate that 
there is a marked unconformity at this horizon. The 
first is the variation in thickness of the Devonian 
Guilmette formation from 1,400 feet to 890 feet within 
a distance of about 3 miles. Second, in the Deep 
Creek Mountains upper Mississippian rocks belonging 
to the Woodman formation overlie the Devonian 
directly, but on Dutch Mountain several hundred feet 
of the lower Mississippian Madison limestone is found 
beneath beds of the Woodman formation that are 
equivalent to those immediately above the Devonian 
to the south. The third bit of evidence is the absence 
of upper Devonian sediments at Gold Hill. Beds of 
this age are found at Pioche, Nev., 53 and in the San 
Francisco district, Utah," to the south; in the Eureka 
district, Nev., 55 to the west; in the Tintic district, 



» Westgate, L. G., Geology and ore deposits ol the Pioehe district, Nev.: TJ.S. 
Oeol. Survey Prof. Paper in, pp. 16-19, 1932. 

"Butler, B. S., Geology and ore deposits of the San Francisco district, Utah: 
U.S. Geol. Survey Prof. Paper 80, pp. 34-35, 1913. 

« Hague, Arnold, Geology of the Bnrefca district, Nev.: U.S. Geol. Survey Mon. 
20, pp. 81-84, 1892. 



22 



GOLD HILL MINING DISTRICT, UTAH 



Utah, 56 to the east; and in the Bandolph quadrangle, 
Utah, 67 to the northeast. 

Loughlin f * has summarized evidence for an uncon- 
formity between the Devonian and Mississippian for 
several places in central Utah. Since Loughlin wrote 
his report Calkins ** has noted a break at this horizon 
in the Cottonwood district, and Gilluly 60 found one 
in the Oquirrh Range. At the last-named locality 
Madison limestone overlies Devonian (?). This, com- 
bined with the several unconformities found at Gold 
Hill, suggests that the unconformity is somewhat less 
significant than was thought by Loughlin, and that 
the break he observed at various places in central 
Utah is a summation of several periods of erosion, 
of which the pre-Mississippian period was perhaps the 
longest. 

OBIGIN OF THE PEE-CAEBOWIPBEOUS DOIOMITIC 
FOKMATIONS 

The method of formation of dolomite and dolomitic 
limestones has been a matter of debate for a number 
of years. The evidence afforded by the thick dolomite 
formations in the Gold Hill quadrangle is thought to 
be of sufficient scientific interest to warrant presenta- 
tion at this place. 

The theories of origin that have been advanced are 
numerous, but the causes assigned may be classed 
under three general headings — (1) primary deposition, 
the dolomite having been laid down either as a chemical 
or organic precipitate, or as a clastic deposit; (2) altera- 
tion, an original limestone deposit having been altered 
to dolomite either before or after its elevation above 
sea level; (3) leaching, magnesium carbonate having 
been concentrated in a deposit that originally contained 
only a small amount of it by the removal of calcium 
carbonate in solution, either abovcor below sea level. 61 
At the present time the view most generally held is 
that dolomite is formed by the alteration of an original 
limestone deposit before it is elevated above the sea. 

Dolomites formed by two different methods have 
been described in the sections on the Abercrombie 
formation and the Sevy dolomite — those in the Aber- 
crombie formation, as a result of alteration along 
fractures after elevation above sea level; and the dolo- 
mite matrix in the conglomerates near the base of the 
Sevy dolomite, as a result of clastic deposition. The 
remainder and great bulk of the dolomite in the Gold 
Hill quadrangle is thought to have been formed by the 



*• Loughlin, O. F., Geology and ore deposits of the Tintic mining district, Utah: 
U.S. Qeol. Survey Prof. Paper 107, p. 36, 1919. 

»' Richardson, G. B., The Paleozoic section in northern Utah: Am. Jour. Sci., 
4th ser., vol. 36, pp. 411-412, 1913. 

« Loughlin, G. F., op. cit., pp. 36-38. 

» Calkins, F. C, Ore deposits of Utah: U.S. Geo]. Survey Prof. Paper 111, pp. 
237-238, 1919. 

*> Gilluly, James, Geology and ore deposits of the Stockton and Fairfield quadran- 
gles, Utah: U.S. Geol. Survey Prof. Paper 173, p. 22, 1932. 

•i The evidence in favor of and opposed to the various theories, together with a 
historical summary, may be found in either Steidtmann, Edward, The evolution of 
limestone and dolomite: Jour. Geology, vol. 19, pp. 323-348, 392-428, 1911; or Van 
Tuyl, F. M., The origin of dolomite: Iowa Geol. Survey, vol. 25, pp. 251-421, 1916. 



alteration of an original limestone deposit before the 
rock was elevated above sea level. Furthermore, it is 
thought that most, if not all, of the alteration occurred 
very shortly after the deposition of the limestone, 
for the most part in shallow water, and probably at 
times of little or no deposition. Raymond m and 
Twenhofel M have recently noted briefly the possible 
importance of the last-named factor. The writer con- 
siders it to have been probably the most important 
one in the formation of the dolomites exposed at 
Gold Hill. 

The evidence indicating that dolomitization was 
accomplished by the alteration of an original limestone 
before it was elevated above sea level is similar to that 
which has been advanced by many investigators and 
need not be repeated here. The coincidence of dolomi- 
tization with texture and structure characteristic of 
shallow water has been pointed out by several writers M 
in recent years. Such features occur throughout the 
dolomitic formations at Gold Hill and are illustrated 
in plate 5, C, D, E. They include cross-bedding, oolites 
and pisolites, intraformational conglomerates, local un- 
conformities, and lenticular beds. It is perhaps signif- 
icant that many of the beds not possessing these 
features are mottled dolomites, in which the mottling 
is due to areas of less complete dolomitization. Near 
many of these mottled dolomites beds of relatively 
pure limestone are found. 

The evidence for the theory that dolomitization is 
related to periods of nondeposition on the sea bottom 
is less direct. It is based largely on the following 
reasoning: A thick section of sediments that shows 
shallow-water phenomena throughout implies con- 
tinual sinking of the sea floor. This sinking must have 
progressed at the same rate as the deposition of sedi- 
ment, or more slowly ; otherwise the higher beds would 
show characteristics of deeper water. Sinking at the 
same rate as deposition would almost certainly imply 
a dependence of sinking upon sedimentation, which 
Barrell 8S has shown is not warranted by the evidence 
afforded by the deltas of the Nile and other great 
rivers. But if the rate of sinking is slower than the 
rate of deposition, there must, of necessity, be many 
periods during which there is no deposition of sediment, 
and any material deposited will be above the baselevel 
of wave or current action and will be swept away to 
regions that are below wave base. Calcareous muds 
will thus be subject to reworking and alteration by 
the sea water for some time, and it is thought that in 
this fact is the chief explanation of dolomitization. 
The analyses assembled by Steidtmann show that 

« ! Haymond, P. E., A possible factor in the formation of dolomite: Geol. SocJ 
America Bull., vol. 36, p. 168, 1925. 

'» Twenhofel, W. H., A treatise on sedimentation, p. 262, Baltimore, 1928. 

« Skeats, E. W„ The formation of dolomite: Am. Jour. Sei., 4th ser., vol. 45, pp. 
194-199, 1918. Van Tuyl, F. M., The depth of dolomitization: Science, new ser., 
vol. 48, pp. 350-852, 1918. Tarr, W. A., A possible factor in the origin of dolomite: 
Science, new ser., vol. 81, p. 521, 1920, 

» Barrell, Joseph, Tha strength of the earth's crust: Jour. Geology, vol. 22, 
pp. 36-48, 1914. 



CARBONIFEROUS SYSTEM 



23 



almost all limestones contain a small amount of mag- 
nesium carbonate, which might be interpreted as a 
measure of the amount of replacement or alteration 
that occurs during continuous sedimentation. A pro- 
longed exposure of the same calcareous mud to wave 
and current action would also permit selective leaching 
of calcium carbonate by sea water, a phenomenon 
which is known to occur in nature. 66 

The hypothesis outlined in the preceding paragraph 
seems to explain most of the characteristics of the 
dolomitic formations in the Gold Hill quadrangle. 
Beds showing shallow-water texture, wherever more 
than a few feet thick, are very thoroughly dolomitized, 
yielding no effervescence whatever with dilute acid. 
Dolomitic beds without this texture are mottled by 
patches higher in calcium carbonate and are in many 
places interbedded with limestone. It is thought that 
these represent periods when sedimentation was slight- 
ly slower than down warping, or in which downwarping 
was somewhat spasmodic, allowing rather thick beds 
to be deposited before baselevel was reached, and then 
sinking was again initiated before dolomitization was 
complete. 

Similar dolomitic rocks at Tintic have been explained 
by Loughlin 67 as the result of alteration of porous 
sediment in shallow water continuing for long periods 
after deposition but inhibited at certain times and 
places by the deposition of impervious argillaceous 
sediment or limestone mud. This explanation implies 
conditions similar to those inferred by the writer but 
is too restricted to be applicable at Gold Hill, because 
of the many places in which coarsely crystalline lime- 
stone and dolomite are in contact without intervening 
shaly material or dense limestone, as in the Trippe 
limestone and the Guilmette formation. Shaly mate- 
rial is, however, far more- abundant in limestone zones 
than elsewhere, but it is thought that this is due 
rather to more rapid sedimentation in areas that had 
not yet reached the baselevel of deposition. Black- 
welder M has considered the formation of the Bighorn 
dolomite in Wyoming the result of an abundance of 
magnesia-rich algae. There is no evidence at Gold 
Hill that algae have exerted any influence in the for- 
mation of dolomite. Daly " has suggested that many 
of the pre-Cambrian and early Paleozoic dolomites 
in the Rocky Mountain region at the international 
boundary are the result of direct precipitation. The 
evidence that has been presented in the foregoing 
descriptions is opposed to such an origin at Gold Hill, 
and it is not believed to be of any quantitative im- 
portance there. 

» Clarke, F. W., The data of geochemistry, 5th ed.: U.S. Oeol. Survey Bull. 770, 
p. 574, 1924. 

» ! Loughlin, O. F., Geology and ore deposits of the Tintic mining district, Utah: 
U.S. Oeol. Survey Prof. Paper 107, pp. 91-93, 1919. 

« Blackwelder, Bitot, Origin of the Bighorn dolomite of Wyoming: Oeol. Soc, 
America Bull., vol. 24, pp. 607, 824, 1913. 

•• Daly, E. A., First calcareous fossils and the evolution of the limestones: Oeol. 
Soc. America Bull., vol. 20, pp. 163-170, 1909. 



It is not at all probable that the theory that has been 
outlined here will be everywhere applicable, for the 
many diverse hypotheses that have been put forward 
indicate that the conditions of dolomitization differ 
in different places. Furthermore, it may be that the 
basic cause of dolomitization has not yet been deter- 
mined and that the many theories of origin simply 
reflect the various environmental conditions in which 
this unknown cause is effective. 

CORRELATION OF PRE-CARBONIFEROUS SEDIMENTARY 
ROCKS IN EASTERN NEVADA AND WESTERN UTAH 

The correlations made for the pre-Carboniferous 
formations are given in tabular form in figures 3 and 4. 
Many of the correlations are extremely tentative, be- 
cause of the common paucity of fossils and the notable 
variations in lithology in nearby areas. These figures 
bring out rather clearly the several unconformities 
present and, to a less extent, the variations in the kind 
of sediment deposited. The latter feature is somewhat 
masked by the failure of some of the earlier reports 
to differentiate dolomite and limestone. 

Of chief interest, however, are the striking differ- 
ences between the north-south and east-west sections. 
In the former the thicknesses of formations of the same 
age are roughly equivalent, and except for the absence 
of Middle Ordovician and Upper Devonian at Gold 
Hill, the time and extent of intersystemic and intra- 
systemic erosion are shown to have been nearly the 
same in all sections. In the east-west sections, how- 
ever, there is an abrupt thickening of all formations 
from east to west and also a different succession. 70 

CARBONIFEROUS SYSTEM 

Rocks of Carboniferous age are by far the most 
widespread of the Paleozoic sedimentary rocks in the 
quadrangle. They have been divided into 6 forma- 
tions — 3 Mississippian, 2 Pennsylvanian, and 1 
Permian. Three facies of the Carboniferous have been 
distinguished and designated the eastern, central, and 
western facies. They have been brought into more or 
less close contact with one another by two large thrust 
faults, although originally they were probably several 
miles apart. The eastern facies is represented by 
rather scanty outcrops of only one formation, the 
Woodman, which overlies the older Paleozoic rocks 
with slight unconformity and is overridden by the 
lower of the two thrusts. The central facies, which 
includes the Ochre Mountain limestone and the 
Manning Canyon and Oquirrh formations, lies between 
the two thrusts. The western facies, which contains 
representatives of all six formations, lies above the 
upper thrust. The lithologic differences between the 
Manning Canyon and Oquirrh formations in both the 



'» Nolan, T. B., A late Paleozoic positive area in Nevada: Am. Jour. Sci. , 5th ser., 
vol. IB, pp. 164-161, 1928. 



— : .-- - - -ffTiiwr iiif 



24 



GOLD Httli MINING DISTRICT, UTAH 



western and central facies are striking. The relations 
between the three facies are summarized by figure 5. 

MADISON LIMESTONE (JQOWBR MISSISSIFMAN) 

Distribution. — The Madison limestone is found only 
on Dutch Mountain, Outcrops occur on all sides of 
the mountain at altitudes between 6,000 and 7,000 
feet. On the south and east sides this limestone forms 



Eureka district, 
Nevada (Hague) 



and two smaller ones are in Accident Canyon and near 
the head of Trail Gulch. There are two small out- 
crops on the north side of Dutch Mountain, one 
near the mouth of Accident Canyon and one near 
the summit of the HE above the Garrison Monster 
mine. 

The small area of limestone near the town of Clifton 
contains a few poorly preserved fossils, which, accord- 



Middle . Cottonwood quadrangle, 
(Devonian Utah (Calkins) 

/-Mggiggiggan 




4)000 Faet. 



Figtoe 3.— Correlation of pro-Carboniferous rocks in eastern Nevada and western Utah from west to east 



a fairly continuous belt, broken by two large faults, 
one in Tribune Gulch and one south of the Spotted 
Fawn mine. On the northwest and west sides the 
formation is found only in the bottoms of valleys, 
where it is exposed in inliers, eroded through younger 
rocks. The largest of these outcrops is in Royal Gulch, 



ing to G. H. Girty, somewhat resemble those found in 
the Madison limestone. lithologically, however, the 
beds resemble the Ochre Mountain limestone, and this 
apparent relationship is heightened by the presence of 
an interbedded belt of black shale, apparently the 
Herat shale member of the Ochre Mountain. The 



CARBONIFBBOUS SYSTEM 



25 



outcrop has therefore been mapped as the Oehre 
Mountain limestone. 

All the outcrops of the Madison belong to the 
western facies of the Carboniferous. No beds of this 
age are found in the eastern facies, in which upper 
Mississippian rocks rest directly upon the Devonian. 
It is not known whether the formation is present in the 
central facies, as the oldest beds of this group exposed 
within the quadrangle belong to the Ochre Mountain 
limestone, of upper Mississippian age. 



stone is a dull dark-gray on fresh fracture and weathers 
to a distinctly lighter-gray. It is normally very dense 
but includes a great number of crinoid stems made up 
of coarsely crystalline calcite. 

In the greater part of the formation as exposed the 
beds are moderately thin, ranging from 3 inches to 
1 foot in thickness. The bedding is marked in many 
places by a concentration of pink or less commonly 
yellowish clay. Small amounts of similarly colored 
clay are also found within individual beds in some 



Pioche district, 
N evada (Westgate) 



Yellow Hill 
limestone 



Mend ha 
limestone 



Highland Peak 
limestone 



Lynd o n limestone 



Pioche 
formation 



Prospect 
Mountain 
quartz ite 



lississip p(an 



Gold Hill quadrangle, 
Utah (Nolan) 



Dolomite — — — —__ 

Upper Ordovician 

Middle and ^"^"^f" 
Lower Ordovician Utah(Walcott) 

"LrtrnestcTtg 



Upper 
Cambrian 



Middle 
Cambrian 

-Chisholm 
shale 



Notch Peak 
limestone 



Orr formation 



Weeks 
limestone 



Swasey formation 



Lower 
Cambrian 



Marjum 
limestone 



Wheeler 
formation 



Dome Canyon Is. 



Howell formation 



— Picfche form,— 



Prospect 

Mountain 

quartzite 



Lower 
Ordovician 



Upper 
Cambrian 



Chokecherry 
dolomite 



Hicks 
formation 



Randolph quadrangle, 
Utah (Richardson) 




_ anc ' 

Lower Lower 

Ordovician Ordovician 



Upper 
Cambrian 




Middle 
Cambrian 



Abercrombie 
formation 




Lower 
Cambrian 



2,000 



Vertical scale 




4,000 Feet 



Busby qu artzite 



Prospect 
Mountain 
quartzite 



Midd le 
Cambrian 



Lower 
Cambrian 



"3warTPeak 
q uartzit 

Garden City 

limestone 



St.Charles 
limestone 



Blacksmith 
limestone 



Ute limestone 



Langston limestone 



Brigham 
quartzite 



Figure 4 — Correlation of pre-Carboniferous rooks in eastern Nevada and western Utah Irom north to south. 



The name is taken from the Madison Eange, in 
south-central Montana, where rocks of this age were 
described by Peale. 

Lithology. — The Madison limestone is best exposed 
on the north side of Pool Canyon, where, in places 
distant from the quartz monzonite, it forms cliffy 
slopes beneath less resistant sandstones. The lime- 



places, and the weathered surfaces of such beds have 
a faint pinkish mottling. 

Many beds are crowded with crinoid stems and 
small cup corals. In a few places these fossils are 
partly silieified and weather out in relief from the 
usual smooth surface. Fossils other than the two kinds 
mentioned are not easily found. This is probably due 



26 



GOLD HILL MINING DISTBICT, UTAH 



to the rather general fracturing to which the forma- 
tion has been subjected and which has resulted in 
an abundance of veinlets and splotches of white 
calcite. 

At the top of the formation there are about 10 or 
15 feet of more massively bedded limestone, which 
contains numerous nodules of dark chert, some as 
much as a foot in largest diameter. Above these beds, 
apparently conformable, are sandstones of the Wood- 
man formation. 



The faunas are not very extensive, and the specimens are very 
poorly preserved, but there can be little doubt of the geologic age 
as lower Carboniferous and the correlation as with the Madison 
limestone. 

6052 and 6329. North side of Tribune Gulch on ridge line; 



Zaphrentis sp. 
Amplexus aff. A. fragilis. 
Syringopora sureularia. 
Triplophyllum excavatum. 
Lithostrotion sp. 
Chonetes loganensis. 



Spirifer centronatus. 
Straparollus ophirensis. 
Euomphalus utahensis. 
Euomphalus luxus? 
Nautilus? sp. 
Phillipsia peroceidens. 



NAfestern facies 

Triassic 
Ger ster 
■fbrmatiori 



Oquirrh . 
formation* 








Manning Canyon 
formation 



Ochre 
Mountain- 
Jimestone 



Woodman 
formation 

Madison" 
limestone 



rV 




T3^& 




Horizon of black chert 



Central facies 



.Jaaaffi 



Limestone 
member 



variable thickness" 
jn both facies _ 



Same thickness in 
both facies assumed 



EEf; 



- Herat shale member— I 



Top of exposure; 
probably limited 
above by thrust 
fault 



Bottom of exposure; 
probably limited below E aste rn 
by thrust fault facies 



Woodman 
formation 




Devonian 



Top of exposure ; 
probably limited 
above by thrust fault 

UNCONFORMITY 



1,000 O 

Mill 



Vertical scale 



_u 



5,000 Feet 



Fiqtjbe 6.— Eolations between the three facies of the Carboniferous rocks. 



Thickness. — The maximum thickness of the Madison 
limestone was found in Pool Canyon, where it is about 
400 feet. Here, however, as elsewhere on Dutch 
Mountain, the lower contact is a thrust fault, and as 
a result the observed thickness varies considerably. 
In the Deep Creek Mountains the formation was not 
found, the next higher (Woodman) formation resting 
directly upon the Guilmette formation. 

Age awl correlation. — Fossils from the Madison lime- 
stone were examined by G. H. Girty, who says: 



6323. 

cabin: 



North side of Royal Gulch 2,000 feet southeast of 



Triplophyllum sp. 
Syringopora sureularia? 
Spirifer centronatus? 



Composita sp. 
Euomphalus utahensis? 
Platyceras sp. 



Two collections from this formation were made by 
L. D. Burling during a reconnaissance trip through 
Utah and Nevada in August 1905. Lists of these 
have not previously been published and are therefore 
included here. 



CABBONIFEROTJS SYSTEM 



27 



98, North side of Pool Canyon, southeast side of Dutch 
Mountain, about l}i miles up the canyon and 200 to 300 feet 
above the canyon bottom: 

Syringopora? sp. 1 Euomphalus sp. 

Triplophyllum sp. | Platyceras sp. 

This collection was made about ISO feet below the top of the 
formation. 

99. North side of Pool Canyon, southeast side of Dutch 
Mountain [label incomplete]: 

Productus galeanus? 
Dielasnaa? sp. 
Spirifer aff. S. grimesi. 
Spirifer aff, S. vernonensis. 



Spiriferina subelliptica? 
Spiriferina solidirostris? 
Retleularia cooperensis. 
Cleiothyridina sp. 



Cladochonus sp. 

Triplophyllum sp, 
Crinoid columnals. 
Spirorbis sp. 
Penestella, several sp. 
Pinnatopora sp. 
Cystodietya sp. 
Schizophoria? sp. 
Pustula sp. 

This collection was made at the top of the formation near the 
eontaet with the Woodman formation, 

Mr. Girty states that "both lots appear to be 
Madison." 

The Madison limestone in the Oquirrh Range 71 is 
of lower Mississippian age, as are the Victoria quartz- 
ite, the Gardner dolomite, and the lower portion of the 
Pine Canyon limestone in the Tintic district. 72 

WOODMAN FORMATION CUPPER MISSISSIPPIAN) 

Distribution. — The Woodman formation, named 
from Woodman Peak, on the south side of Dutch 
Mountain, is exposed at several places within the 
quadrangle. In the Deep Creek Mountains there are 
four outcrops north and south of Sevy Canyon. 
These belong to the eastern facies; the remaining 
areas belong to the western facies. Beds higher in 
the formation are present on the west and south sides 
of Ochre Mountain, The most extensive exposures of 
the formation, however, are found on Dutch Moun- 
tain, particularly on the higher parts of the western 
slope. Smaller exposures occur in several places along 
the north side of Dutch Mountain. 

There are two other areas in which the Woodman 
formation may be present. One of these is the large 
block of sedimentary rocks surrounded by quartz 
monzonite north of Clifton. A small collection of 
poorly preserved fossils from this locality was regarded 
by Mr. Girty as resembling the Woodman fauna more 
closely than any other. Lithologically, however, the 
beds resemble those of the overlying Ochre Mountain 
limestone, and because of their association with a 
black shale, thought to be the Herat shale member, 
they have been mapped as the higher formation. The 
other region for which some doubt exists is at the 
6,267-foot hill on the south side of North Pass Canyon. 
Two poor fossil collections were made here. The 



" Gilluly, Jamas, Geology and ore deposits of the Stockton and Fairfield quad- 
raagles, Utah: U.S. Qeol. Survey Prof. Paper 173, pp. 23-28, 1932. 

n Loughlin, G. J"., Geology and ore deposits of the Tintie mining district, Utah: 
U.S. Geol. Survey Prof. Paper 107, pp. 38-41, 1919. 



lower one was referred somewhat doubtfully to the 
Woodman formation, and the upper one with similar 
reservations to the Ochre Mountain limestone. How- 
ever, on the north side of the canyon similar beds 
that are apparently continuous with these are defi- 
nitely of Pennsylvanian age, and the beds in question 
have therefore been mapped as a part of the Oquirrh 
formation, 

Lithology. — The Woodman formation consists of a 
lower division of dominant calcareous sandstone and 
an upper division consisting chiefly of sandy limestone. 
These two units are found in both the eastern facies 
and the western facies. 

The sandstone portion at the base is roughly 200 
feet thick. The beds are purplish or reddish brown, 
are fine-grained, and contain a variable though small 
proportion of calcium carbonate as cement. Locally 
nodules of black chert, an inch or so in maximum 
diameter, are found in the sandstone. Several thin 
beds of sandy limestone, which are probably lenticular, 
and a minor amount of shale are usually present. 
This part of the formation is everywhere poorly ex- 
posed, as the sandstone breaks down into small rec- 
tangular blocks, which not only cover the surface 
underlain by the formation but form extensive areas 
of talus that conceal the adjoining formations. 

The upper and thicker calcareous division com- 
prises rocks of several varieties. The most abundant 
is a sandy limestone which is dark gray to almost 
black on fresh fracture but which weathers light brown 
to pinkish. It leaves a large residue of sandy material 
when dissolved in hydrochloric acid. Most beds of 
this character contain nodules of dark-gray or black 
chert. These nodules are generally 6 inches or so in 
diameter but may be as much as a foot. They include 
casts of fossils in many places. There is, as a rule, no 
sharp boundary between the chert and the limestone, 
the contact being formed by alternate irregular lami- 
nations of dark chert and tan-weathering sandy lime- 
stone. Interbedded with the sandy limestones are 
calcareous sandstones. The boundary between the 
two kinds of rock is not sharp, and one passes into the 
other with increase or decrease in the amount of sand. 
The sandy limestones are much more abundant. 

Two other varieties of limestones may be noted. 
One is a platy fine-grained limestone which is dark-gray 
on fresh fracture and a very light gray on weathered 
surfaces. It contains only a small amount of insoluble 
material. The other variety is found locally in thin 
beds. It is a coarsely crystalline medium-gray lime- 
stone, crowded witli fossils, chiefly large crinoid stems. 
The fossils are silicified in many outcrops of these beds. 

The following section of the formation was measured 
on the south side of Sevy Canyon, in the Deep Creek 
Mountains. It is incomplete, as the top of the forma- 
tion is not exposed, but is the thickest of all the out- 
crops of the formation examined. 



28 



GOLD HILL MINING DISTRICT, TJTAH 



Incomplete section of Woodman formation on south side of Sevy 

Canyon 

Fed 

TMn-bedded sandy and oherty limestone 77 

Calcareous sandstone 59 

Thin-bedded blue-gray oherty limestone 76 

Thin-bedded sandy limestone 30 

Calcareous sandstone 46 

Thin-bedded sandy limestone L 63 

Blue-gray massively bedded oherty limestone 15 

TMn-bedded sandy and eherty limestone ,. 166 

Thin-bedded sandy limestone with some calcareous 

sandstone 137 

Thin-bedded sandy and eherty limestone 62 

TMn-bedded sandy limestone 86 

Calcareous sandstone with a few beds of sandy limestone^ 209 

Limestone 1 

Limestone of Guilmette formation. 

1,027 

Thickness. — The total thickness of the formation is 
unknown, as nowhere in the quadrangle is a complete 
section exposed. The lower 1,000 feet is exposed on 
the Deep Creek Mountains, and the upper 700 or 800 
feet on Ochre Mountain. A varying thickness of the 
formation is shown on Dutch Mountain, but at every 
exposure there the upper beds have been eliminated by 
faulting at the contact with the overlying Ochre 
Mountain limestone. Although no satisfactory corre- 
lation could be made between the lower beds on Ochre 
Mountain and the upper beds in the Deep Creek 
Mountains, they are thought to indicate a total thick- 
ness for the formation of about 1,500 feet. There is 
no evidence to indicate any striking difference in 
thickness between the various facies. 

Age and correlation. — The Woodman formation is of 
upper Mississippian age. The overlying Ochre Moun- 
tain limestone is also of this age, and Mr. Girty reports 
that "the Woodman and Ochre Mountain faunas are 
not sharply distinguished in my mind; or better, many 
of the collections are too small, or too poorly preserved, 
or too nondescript in character to be amenable to the 
distinctions that I do make." The formation may be 
correlated directly with the Deseret limestone and 
Humbug formation of the Oquirrh Kange, n the Hum- 
bug formation of the Tintic district, 74 and the lower 
portion of the widespread Brazer limestone, 75 to the 
northeast. 

The fossil collections from the formation have been 
studied by Mr. Girty, whose determinations are as 
follows: 

Collections from the eastern facies 

6046, 2,200 feet east-southeast of southeast corner of sec. 
13, T. 9 S„ R. 19 W.: 



Pustula aff. P. alternata, 
Rhynchopora? sp. 
Coelonautilus? sp. 



!s Gilluly, James, Geology and ore deposits of the Stockton and Fairfield quad- 
rangles, Utah: U.S. Deal. Survey Prof. Paper 173, pp. 25-29, 1932. 

» Loughlln, Q. F„ Geology and ore deposits of the Tintic mining district, Utah: 
U.S. Geol, Survey Prof. Paper 107, pp. 41-42, 1919. 

" Mansfield, G. B., Geography, geology, and mineral resources of part of south- 
eastern Idaho: U.S. Geol. Survey Prof. Paper 152, pp. 63-71, 1927. 



Fenestella sp. 

Productus aff. P. burlington- 

ensis. 
Productus ovatus. 

6053 and 6324. North side of Sevy Canyon, 2,300 feet west- 
southwest of point at 7,164 feet: 

Triplophyllum sp. 



Productus aff. P. burlington- 

ensis. 
Pustula aff, P. alternata. 
Pugnax n. sp. 
Spirifer aff. S, grimesi. 
Spirifer sp. 

Brachythyris suborbieularis, 
Spiriferella? sp, 

6069. 1.7 miles north of east from Simonson ranch: 

Pustula aff. P. conoentrica? 



Cladochonus sp, 

Crinoid? indet. 

Fenestella, several sp. 

Pinnatopora sp. 

Cystodictya sp. 

Orbieuloidea sp, 

Chonetes aff, C. oklahomensis. 



Brachythyris suborbieularis. 
Cleiothyridina sublamellosa? 
Proetus n. sp. 



Productus aff. P. burlington- 

enais. 
Spirifer aff. S. imbrex. 

The preceding three collections were taken from the base 
of the formation, 

6051 and 6382. Near southeast corner of sec. 13, T. 9 S., 
R. 19 W.: 

Pustula? sp. 

Rhynchopora? aff. R. coop- 

erensis. 
Rhynchopora sp. 
Cranaena aff. C. globosa. 
Spirifer aff. S. rostellatus. 
Spirifer sp. 

Brachythyris suborbieularis. 
Reticularia aff. R. pseudo- 

lineata. 
Spiriferina aff. S. solidirostris. 
Syringothyris sp. 
Composita sp. 
Eumetria verneuiliana. 
Hustedia aff. H. mormoni. 
Solenomya? sp. 
Streblopteria? sp, 
Deltopecten sp, 
Worthenia? sp. 
Pleurotomaria sp. 
Platyceras aff. P. capax. 

horizon about 1,050 feet above 



Amplexus aff. A. fragilis. 
Triplophyllum sp. 
Fenestella sp. 
Orbieuloidea sp, 
Rhipidomella sp. 
Schizophoria aff. S. swallowi. 
Chonetes aff. C. ornatus. 
Chonetes aff.'C. platynotus. 
Productus ovatus. 
Productus semireticulatus. 
Productus aff. P. parvus. 
Productus aff. P. setiger. 
Productus aff. P. keokuk. 
Productus aff. P. gallatinensis. 
Pustula aff. P. alternata. 
Pustula aff. P. subsulcata. 
Pustula aff. P. oklahomensis. 
Pustula aff. P. patula. 
Puetula aff, P. millespinosa. 
Pustula aff. P. biseriata? 
Pustula n. sp. 

This collection came from a 
the base of the formation. 



Collections from, the western facies 

6274. Accident Canyon, east of cabin: 
Productella hirsutiformis. 
Leiorhynchus carboniferum var. polypleuram. 
This lot came from the sandstone at the base of the formation 
and seems to contain the fauna of the Herat shale member. 
It is quite possible that this occurs at several horizons. 

6366. South side of Oehre Mountain, 2,500 feet east of 
6,886-foot hill: 



Triplophyllum aff. T. centrale. 
Stenopora aff. S. ramosa. 
Rhipidomella? sp. 
Productus aff. P. burlington- 

ensis. 
Productus aff. P. setiger. 



Productus sp. 

Pustula aff. P, alternata. 

Pustula aff. P. subsulcata. 

Pustula? sp. 

Spirifer aff, S. rostellatus. 

Brachythyris suborbieularis. 



CARBONIFEBOTJS SYSTEM 



29 



6367. 250 feet north of 6366: 

Triplophyllum ep. Pustula aff, 

Chonetes aff. C, platynotus. Pustula aff. 

Froductus ovatus. Pustula aff. 

Productus ovatus var. latior? Pustula aff. 

Productus aff. P. mesialis. Spirifer aff. 

Productus sp. Reticularia 

Productus aff. P. setiger. lineata. 

Pustula alternata. Spirifer aff. 

Pustula aff. P. bieeriata, Spiriferella s 

6368. 250 feet north of 6367: 

Pavosites sp. 
Triplophyllum sp. 
Echinocriims sp. 
Productus ovatus. 
Productus aff. P. mesialis. 
Brachythyris aff. B. suborbi- 
cularis. 

6369. 100 feet north of 6368: 

Echinocrinus sp. 
Chonetes aff. C. oklahomensis. 
Productus aff. P. mesialis. 
Productus sp. 



P, concentrica. 
P. eubsulcata. 
P. moorefleldana. 

P. oklahomensis. 
S. increbescens. 

aff. R. pseudo- 

S. rostellatus. 
:p. 



Spiriferina aff. S. subelliptica- 
Composita sp. 
Cleiothyridina sublamellosa 

var. 
Hustedia aff. H. multicostata. 



Cranaena aff. C. subglobosa. 
Composita sp. 
Cleiothyridina sublamellosa. 
Leptodesma sp. 

6065. 2,100 feet south-southeast of hill 7150, south side of 
Ochre Mountain: 



Triplophyllum aff. T. centrale. 
Schizophoria aff. S. swallowi. 
Chonetes aff. C. oklahomensis. 
Productus ovatus. 
Productus aff. P. mesialis. 



Pustula aff. P. subsulcata. 
Spirifer aff. S. increbescens. 
Spirifer aff. S. grimesi. 
Spiriferella? sp. 



This lot was taken near the top of the formation. 

6319. 1,000 feet west of 6,964-foot point on southwest side 
of Dutch Mountain: 

Zaphrentis aff. Z. excentrica. I Fenestella sp. 
Crinoidal fragments. | Productus ovatus? 

6322. 1,000 feet north of cabin in Royal Gulch: 



Productus aff. P. inflatus. 
Productus aff. P. semireticu- 

latus. 
Spirifer sp. 
Orthoceras? sp. 



Michelinia aff. M. meekana. 
Triplophyllum aff. T. centrale. 
Zaphrentis aff. Z. excentrica. 
Stenopora? sp. 
Fenestella sp. 

These two collections were taken from beds rather high in 
the formation. They present an aspect rather different from 
the other collections and one that resembles some of the col- 
lections from the Oquirrh formation. 

OCHRE MOUNTAIN LIMESTONE (UPPER MIS8IHSIPPIAN) 

Distribution. — The Ochre Mountain limestone is ex- 
posed in several places within the quadrangle. The 
largest exposure is on Ochre Mountain, which is in 
large part underlain by the formation and from which 
it takes its name. Dutch Mountain is also capped 
by this limestone, and there are other outcrops along 
the northern border of the quadrangle and in a belt 
along Trail Gulch. Smaller areas of the formation 
are found at the borders of the quartz monzonite stock 
and as roof pendants within it from Pool Canyon and 
the Rube mine south to Clifton. Still another locality 
is north and south of Overland Canyon from the Midas 
mine westward into Blood Canyon. 



Although the association of these outcrops with dis- 
tinctive areas of the Manning Canyon and Oquirrh 
formations shows that some of them must represent 
a central and some a western fades, no lithologic dis- 
tinction can be drawn between exposures definitely 
belonging to the one or the other. Isolated outcrops 
or those in fault contact with the surrounding sedimen- 
tary rocks therefore cannot readily be placed in their 
proper fades, except by reason of their relations to 
nearby outcrops or to structural features such as the 
thrusts. The outcrops in the vicinity of Overland 
Canyon, together with those in which the Western 
Utah, United States, and Cane Springs mines are lo- 
cated, have been referred to the central fades, and the 
remainder to the western facies. 

The area of limestone near Clifton may possibly be 
Madison limestone, and the portion of the roof pend- 
ant north of Clifton mapped as Ochre Mountain lime- 
stone may belong rather to the Woodman formation, 
but for the reasons previously given they are regarded 
as belonging to the Ochre Mountain limestone. On 
the other hand, a fossil collection from hill 6267, on 
the south side of North Pass Canyon, was doubtfully 
referred by Mr. Girty to the Ochre Mountain limestone 
but for the reasons given in the description of the 
Woodman formation, to which another collection from 
this locality was referred, it seems more probable that 
these beds are part of the Oquirrh formation. 

Lithology. — The Ochre Mountain limestone is com- 
posed chiefly of rather thick bedded limestone. Near 
the base the limestone contains a considerable amount 
of chert, and near the top a smaller amount. About 
1,700 feet above the base of the western facies is a 
thin bed of black shale, which has been mapped sep- 
arately as the Herat shale member. This is also 
present in the central facies. 

The contact of the formation with the underlying 
Woodman formation was seen only on the south and 
west sides of Oehre Mountain. Here laminae of sandy 
limestone, similar to that in the Woodman, are found 
several hundred feet above the lowest bed of massive 
limestone, which was chosen as the base of the Ochre 
Mountain limestone. 

The limestone beds are similar in appearance 
throughout the formation. They are commonly 
brownish gray on freshly broken surfaces and weather 
to light bluish gray. They are usually fine-grained, 
but coarser-grained beds occur locally. Individual 
beds may be as much as 10 feet in thickness, and almost 
all are more than 1 foot thick. In a few places thinner- 
bedded limestones are found. These contain a much 
larger proportion of insoluble material than the normal 
pure limestones and weather to hues of yellow and 
pink. 

The basal few hundred feet of the formation includes 
beds that contain large amounts of chert, in some beds 
considerably more than half. The chert is generally 



30 



GOLD HILL MINING DISTKICT, UTAH 



light gray but weathers to a characteristic tan. The 
chert lenses and masses are everywhere highly shat- 
tered. In the upper cherty zone, which is less pro- 
nounced, the chert is present in the form of small 
nodules and stringers. The limestone beds included 
in the upper zone contain more sand than is generally 
present elsewhere. 

Near the intrusive rock the formation has been 
bleached and recrystallized, and in some beds silicate 
minerals have replaced the calcium carbonate in vary- 
ing amounts. In other places not visibly related to 
areas of intrusive rocks the limestone has been changed 
to dolomite, the alteration causing a change in the 
color of the weathered surface to a dull gray. These 
alterations are described in more detail on pages 91-94. 

Herat shale member. — The Herat shale member has 
been mapped at several places on the south side of 
Ochre Mountain, in Blood Canyon, and north and 
west of Clifton. The name is taken from the Herat 
mine near Clifton. Outcrops of the shale are rare, 
and it may be present at several places not shown on 
the map. The member is made up of black shale 
with thin lenses of sandstone. In most outcrops it 
has been the site of movements parallel to the bedding, 
with the result that its thickness is extremely variable, 
ranging from almost nothing to about 50 feet. In 
two of the exposures on Ochre Mountain the limestone 
beneath the shale, which is normally only slightly 
sandy, has been rather thoroughly silicified. In many 
respects the Herat shale member is similar to the 
stratigraphicaily higher Manning Canyon formation, 
and in the absence of fossils it is often difficult to dis- 
tinguish the two. 

Thickness. — A complete section of the Ochre Moun- 
tain limestone was not found within the quadrangle. 
An approximation to the true thickness may be ob- 
tained by assuming that the central and western facies 
have the same thickness and that the Herat shale mem- 
ber has the same position in both facies. Both assump- 
tions are probably open to question, and the result 
must be regarded merely as indicating the order of 
magnitude of the thickness. It is based upon an esti- 
mate of the thickness from the base of the western 
facies of the formation up to the Herat shale member, 
made at two places on the south side of Ochre Moun- 
tain; and an estimate of the thickness from the shale 
to the top of the central facies of the formation, made 
along Overland Canyon. These estimates were, re- 
spectively, 1,700 feet and 2,800 feet, indicating a total 
thickness of 4,500 feet. The figures were obtained by 
scaling the thickness from the geologic cross sections 
and are therefore only rough approximations, but more 
refined measurements did not seem justified in view 
of the assumptions made. 

Age and correlation. — The Ochre Mountain lime- 
stone, like the Woodman formation, is of upper 



Mississippian age. Mr. Girty's notes on the difficulties 
in distinguishing between the faunas of the two forma- 
tions were quoted under the Woodman formation 
(p. 2-8) and need not be repeated here. The formation 
most nearly equivalent to the Ochre Mountain lime- 
stone is the "Great Blue" limestone in the Oquirrh 
Range. 711 The formation is probably also more or less 
equivalent to the upper portions of the Brazer lime- 
stone of northeastern Utah n and southeastern Idaho. 78 
Mr, Girty's determinations of the fossils in the 
collections are as follows: 

Collection from the central fades 
6325. Blood Canyon, north of spring: 

Triplophyllum sp. j Girtyella indianensis? 

Campophyllum sp. Composita sp. 

Fenestella sp. Cleiothyridina sublamellosa? 

Schizophoria aft". S. swallowi? | Cleiothyridina? n, sp. 
Orthotetes sp. j Bellerophon sp. 

Productue aft". P. parvus. I 

This is the only collection from the central facies. Meta- 
morphism by the quartz monzonite stock appears to have 
destroyed most of the fossils originally present in it. 

Collections from the western facies 

Because of the difficulties in determining the throws of the 
numerous faults that cut the Ochre Mountain limestone, no 
attempt is made to list the collections in their proper strati- 
graphic order. The collections from the Herat shale, which is 
distinctive lithologically, are listed separately. 

5865. 3,300 feet N. 60° W. from summit above Garrison 
Monster mine: 

Crinoid columnals. ] Beilerophon? sp. 

Levidentalium? sp. I 

5866. West side of Ochre Mountain at base of ridge on south 
side of northernmost canyon: 



Produetus ovatus. 
Productus aff. P. parvus. 
Diaphragmus elegans? 
Spirifer aff. S. pellensis. 
Cleiothyridina sublamellosa. 



Crinoid columnals. 
Stenopora sp. 
Rhombopora? sp. 
Fenestella, several sp, 
Schizophoria sp. 

5866a. Same canyon as 5866, halfway up ridge: 

Productus brazerianus. 
5886b. Same canyon as 5866, just below summit: 

Campophyllum? sp. 
5866c. Same canyon as 5866, at head of canyon: 

Eupheinus aff. E. randolphen- j Holopea? sp. 
sis. I Orthoceras aff. O. choctawense, 

5866d. Same canyon as 5866, divide at head of north branch: 

kSyringopora sp. 
5866e. Same canyon as 5866, 400 feet above gravel on north- 
ern ridge: 

Spiriferella? sp. 



* s Gilluly, James, Geology and ore deposits of the Stockton and Fairfield quad 
rangles, Utah: U.S. deol. Survey Prot. Paper 173, pp. 28-31, 1932. 

"Eichardson, a. B., The Paleozoic section in northern Utah: Am. Jour. Soi 
4th ser., vol. 36, p. 413, 1913. 

13 Mansfield, O. E., Geography, geology, and mineral resources of part of souf 
eastern Idaho: U.S. Owl. Survey Pro! Paper 152, pp. 63-71, 1927. 



CABBONIFEROUS SYSTEM 



31 



6044. 1,000 feet southwest of hill 6634, on southwest side of 
Ochre Mountain: 



Stenopora aff. S. mutabilis. 
Stenopora sp. 
Meekopora? sp. 
Chonetes sp. 

Produetus semireticulatus. 
Produetus ovatus? 



Produetus inflatus? 
Spirifer aff. S. pellensis. 
Spirifer aff. S. brazerianus. 
Spiriferella? n. sp. 
Hustedia multicostata? 
Griffithides sp. 

This collection was obtained near the base of the formation. 

6045. Due south of peak 6886, on south side of Ochre 
Mountain, at an altitude of 6,750 feet: 



Spirifer aff. S. pellensis. 
Composita sulcata? 



Produetus aff. P. parvus. 
Dielasma sp. 

6059. 1,500 feet east-southeast of 6,975-foot closed contour 
on south side of Ochre Mountain: 



Produetus inflatus. 

Pustula aff. P. moorefieldana. 



Spirifer aff. S. pellensis. 
Spiriferella? n. sp. 



6060. Just west of hill 6634, on southwest side of Ochre 
Mountain: 



Produetus gallatinensis? 
Pustula aff. P. genevievensis. 



Composita sulcata? 
Cleiothyridina sublamellosa. 



6062. 1,200 feet north of peak 7182, on ridge line of Ochre 
Mountain: 

Produetus ovatus. I Dielasma n. sp. 

Diaphragmus elegans? | 

6063. 1,500 feet west of 7,150-foot peak on south side of 
Ochre Mountain: 

Deltopeeten aff. D. batesvill- 

ensis. 
Brachymetopus sp. 



Productella hirsutiformis. 
Pustula aff. P. subsulcata. 



This collection came from the limestone immediatelj 
the Herat shale. 



beneath 



6067. West of mouth of Accident Canyon, on north side of 
Dutch Mountain: 

Lithostrotionella sp, 

6072. 1,000 feet south -southeast of peak 7150, on south side 
of Ochre Mountain: 



Amplexus sp. 
Eohinocrinus sp. 



Fenestella, several sp. 



This collection was obtained near the base of the formation . 
6075. 200 yards southeast of spring at Clifton: 



Syringopora surcularia, 
Cladochonus sp. 
Campophyllum sp. 
Triplophyllum sp. 
Lithostrotionella sp. 



Amplexus sp. 
Fenestella sp. 
Cystodictya sp. 
Sehizophoria aff. S. swallow! 
Euomphalus utahensis? 



[Mr. Girty regards this as possibly of Madison age, but, for 
the reason given above, the exposure has been mapped as 
Ochre Mountain limestone.] 



6277. 1,000 feet north of Clifton: 

Spirifer aff. S. pellensis. 
Spiriferina transversa. 
Reticularia sp. 
Cleiothyridina sublamellosa. 



Fistulipora sp. 
Fenestella sp. 
Produetus ovatus. 
Produetus aff. P. setiger. 
Pustula aff. P. concentric*. 
Pustula aff. P. biseriata. 
Productella hirsutiformis? 



Aviculipecten aff. A. spinulifer. 
Platyeeras sp. 
Griffithides sp. 

[Mr. Girty states that this collection would suit him better as 
Woodman, but for the reasons noted above it is here included 
in the Ochre Mountain limestone.] 



6373. 6,475-foot hill on southeast side of Ochre Mountain: 



Produetus ovatus. 
Diaphragmus elegans? 



Camarotoechia aff. C. mutata. 
Camarotoechia sp. 



[Mr. Girty notes that this lot "is in its very meager way sui 
generis. It does not look like Ochre Mountain, but then I do 
not know what it does look like."] 

6391. Southwest of highest summit of Ochre Mountain: 

Spiriferina spinosa. 
Ambocoelia fayettevillensis? 
Composita subquadrata var. 
lateralis. 



Fistulipora sp. 
Stenopora sp. 
Rhombopora sp. 
Chonetes oklahomensis. 
Produetus semireticulatus. 
Avonia arkansana? 
Girtyella indianensis. 
Spirifer arkansanus? 
Spirifer aff, S. tenuimarginatus. 
Reticularia sp. 
Spiriferina transversa. 

This collection came from a horizon above the Herat shale. 

6045 and 6365. Same locality as 6063: 

Leiorhynchus carboniferum. 



Composita n. sp. 
Cleiothyridina sublamellosa. 
Pectinopsis squamula? 
Pectinopsis jenneyi, 
Griffithides sp. 
Paraparehites sp. 



Lingula aff. L. halli. 
Orbiculoidea aff. O. bates- 

villensis. 
Crania? sp. 

Productella hirsutiformis. 
Pustula moorefieldana var. 

pusilla, 
Pustula subsulcata. 
Diaphragmus elegans. 



Cleiothyridina sublamellosa. 
Deltopeeten catactus, 
Deltopeeten n. sp. 
Pectinopsis squamula. 
Pleurotomaria? sp. 
Euomphalus? sp. 
Ostracoda. 



6370. About 50 feet up the slope to summit above bench at 
an altitude of about 7,000 feet on south side of Ochre Mountain: 



Deltopeeten catactus? 
Brachymetopus? sp. 
Ostracoda. 



Cladochonus sp. 
Triplophyllum sp. 
Pustula aff. P. subsulcata? 
Leiorhynchus carboniferum. 

The two preceding collections are from the Herat shale 
member. The fauna is clearly the fauna of the White Pine 
shale of the Eureka district, Nev. A similar fauna was found 
near the base of the Woodman formation. 

MANNING CANYON FOKMATION (UPPER MISSI8SIPPIAN? 
AND PENNSYLVANIA!*) 

Distribution. — The Manning Canyon formation, was 
named by Gilluly 79 in the Oquirrh Range, Utah, where 
rocks of similar lithology have essentially the same 
stratigraphic position as those so designated in the 
Gold Hill region. 

The chief group of exposures of the Manning Canyon 
formation are found in a belt 2 miles in maximum width 
that extends from the head of Gold Hill Wash north- 
ward to the south side of Dutch Mountain. Most of 
these exposures have been assigned, on the basis either 
of lithology or of relations to the overlying formation, 
to the central facies. Several of the more westerly 
outcrops, however, belong to the western facies. 
These include the exposures above the Ochre Mountain 
thrust in the vicinity of the Ochre Springs, the small 
areas beneath the two down-faulted blocks of the 
Oquirrh formation on Ochre Mountain, and the ex- 



r * Gilluly, James, Geology and ore deposits of the Stockton and Fairfleld quad- 
rangles, Utah: U.S. Geol. Survey Prof. Paper 173, pp. 31-34, K33. 



32 



GOLD HILL MINING DISTEICT, UTAH 



posure on the southwest flank of Dutch Mountain 
northwest of hill 6566. 

Smaller outcrops occur on the northwest side of 
Dutch Mountain; just east of the Western Utah 
Copper Co.'s mine on Gold Hill; and at several places 
in Blood Canyon, in Overland Canyon, and near the 
Midas mine. The outcrop on the northwest side of 
Dutch Mountain belongs to the western facies of the 
formation; the remainder to the central facies. 

Lithology. — The two facies of the Manning Canyon 
formation are composed almost entirely of quartzite, 
sandy shale, and black shale. The quartzite is dark 
gray to black on fresh fracture, fine-grained, and in 
many places finely laminated. These beds generally 
weather to rusty or brownish colore. Many of the 
beds appear to be lenticular. The black shale is 
similar to that in the Herat shale member of the Ochre 
Mountain limestone. In all the exposures of the for- 
mation seen there was either considerable alteration 
due to nearby intrusive masses or abundant crushing 
and slipping as a result of faulting. Beds of reddish- 
weathering dark limestone a foot or so thick are 
present sparingly. 

The central facies contains somewhat more quartz- 
ite than the western facies, but its chief distinction lies 
in the scarcity of limestone. In most outcrops of this 
facies limestone is entirely absent and the top of the 
formation has been drawn at the base of the lowest 
limestone. This line also approximately marks the 
upper limit of black-shale beds more than an inch or 
so in thickness. Some thin limestone beds, however, 
were observed in the exposures just west of the town 
of Gold Hill and on the east slope of Gold Hill, both of 
which are thought to belong in the central facies. In 
the western facies several thin beds of limestone occur 
in the upper part of the formation, and the upper 
boundary was placed at the top of the highest black 
shale. 

In both facies the thickness of the quartzite beds is 
variable. Locally, as in the exposures of the central 
facies east and north of the northern Ochre Spring, 
quartzite appears to make up the greater part of the 
formation, but in the much thinner section exposed on 
the south side of Pool Canyon, which is of the same 
facies, quartzite beds are comparatively rare. 

Thickness. — The thickness of the formation is 
variable, and nowhere was a section found that was 
thought to represent the true thickness. South of 
Pool Canyon on Dutch Mountain the apparent thick- 
ness in places is 50 feet or less, but to the south of the 
Ferber Road about 2 miles west of Gold Hill it is 
nearer 1,000 feet. Near the Midas mine, where the 
beds are considerably metamorphosed but seem to 
have suffered only minor faulting, the thickness is 
about 450 feet. The figures given are all for the 
central facies. The western facies appears to show 
less variation, but this is probably because there are 
fewer exposures. 



Age and correlation— Two faunas were obtained from 
the Manning Canyon formation. One of these is rep- 
resented by the three following collections, identified 

by G. H. Girty: 

6327. 4,500 feet northwest of spring in Blood Canyon: 

Solenomya? n. sp. aff. S. 
anodontoides. 

Nucula? sp. 

6348. 2,000 feet southeast of benchmark 5885 on Ferber 
Road: 

Naiadites? sp. 

6381. Dump from northern Ochre Spring: 



Yoldia aff. Y. levistriata. 
Goniatites? sp. 



Phanerotrema? sp. 



Nucula aff. N. anodontoides. 
Leda sp. 

The first two lots represent the central facies of the 
formation. The third lot is from a locality where 
outcrops of the two facies are brought into contact 
by the Ochre Mountain thrust, and its proper assign- 
ment is somewhat doubtful. An assignment to the 
western facies, however, seems more probable. Mr. 
Girty has prepared the following note on these collec- 
tions: 

Insofar as faunas limited to so few species can be said to have 
a faunal facies each of these collections is almost unique. Lot 
6381 might not be exceptional if the usual quota of brachiopods 
and bryozoans were present and if the extremely ill-preserved 
fossils did not prove to belong to alien species. All the ordinary 
Pottsville brachiopods are missing also from lot 6327, and in 
addition we have the large and striking form listed as Solenomyaf 
and the large coiled shell that probably belongs in one of the 
goniatite genera. Lot 6348 is still different. Aside from the 
pinnule of a fern, this collection contains only a small pelecypod 
together with fragments of a somewhat larger one. The larger 
fragments suggest the form so common in the nonmarine Potts- 
ville of the Applachian region, which is usually cited as Naiadites 
elongaius. The smaller but also ill-preserved specimens can 
scarcely be N. elongatus unless they are immature as well as 
somewhat distorted, which is quite possible. On the other hand, 
it is possible that none of the specimens belongs to N. elongatus 
or even to the genus Naiadites. Other genera, such as Myalina, 
give us species very similar in appearance, and specimens rarely 
afford any evidence as to their true generic position. These 
facts are important, inasmuch as Naiadites is supposed to be a 
fresh-water or at least a nonmarine genus, whereas Myalina is 
distinctly marine. Instead of themselves affording evidence of 
the marine or nonmarine origin of deposits by their generic 
characters, these forms often have to be given a generic assign- 
ment on the strength of the marine or nonmarine origin of the 
deposits as determined on other evidence. When we were 
making this collection (lot 6348} I remember suggesting that 
it might be of nonmarine origin because of a certain parallel 
with the nonmarine Pottsville of the East. In the East, how- 
ever, the evidence of one collection is corroborated by hundreds 
of others, indicating nonmarine conditions that extended over 
wide areas and persisted through long periods of time. Here, 
on the other hand, the evidence of one collection is contradicted 
by that of others, for lot 6327 can scarcely be nonmarine and 
still less lot 6381. The peculiarities of these three lots are prob- 
ably to be attributed rather to the character of the bottom and 
to distance from shore than to the fresh or brackish condition 
of the waters. 

The second fauna is found both in the upper portion 
of the Manning Canyon formation and in the basal 



CAEBONIPEBOUS SYSTEM 



33 



portion of the overlying Oquirrh formation. It is 
considered by Mr. Girty to indicate a lower Pennsyl- 
vanian age and to be approximately equivalent to the 
Pottsville formation of the eastern United States. 
With one exception, collections of this fauna from the 
Manning Canyon formation were found in the western 
facies of the formation. Mr. Girty has made the fol- 
lowing identifications: 

6281. 600 feet northwest of old smelter west of Gold Hill: 



Orbiouloidea sp. 
Crania modesta. 
Schizophoria texana. 
Derbya robusta. 
Productus ovatus? 
Productus ovatus var. minor. 
Productus aff. P. gallatinensis. 

This collection is from the central facies. 



Composita ozarkana? 
Leda bellistriata? 
Myalina pemiformis, 
Astartella aff. A. compacts. 
Pleurophorus tropidophorus. 
Bacanopsis aff. B. meekana. 
Griffithides morrowensis? 



6276. 1,000 feet west of hill 6337, northeast side of Ochre 
Mountain: 



Streblotrypa sp. 
Lingula carbonaria? 
Productus n. sp. 
Productus ovatus var. minor. 
Pugnoides oeagensis? 
Dielasma? sp. 

Spirifer opimus var. oceiden- 
talis. 



Spiriferina spinosa. 
Composita subquadrata var. 

lateralis. 
Edmondia aff. E. mortonensis. 
Deltopecten occidentalis. 
Pectinopsis n. sp. 
Pectinopsis n. sp. 
Griffithides morrowensis? 



6374. 1,000 feet north of hill 6256, at head of Gold Hill Wash; 



Triplophyllum sp. 

Leioclema sp. b. 

Lingula carbonaria? 

Orbiculoides meekana? 

Rhipidomella aff. R. penniana. 

Derbya robusta. 

Productus cora. 

Productus ovatus var. minor. 

Productus n. sp. 

Pustula? sp. 

Avonia aff. A. arkansana. 

Pugnoides n. ep. 

Pugnoides osagensis var. per- 

costata? 
Spirifer opimus. 



Spirifer opimus var. occiden- 
talis. 
Spiriferina transversa. 
Composita ozarkana. 
Cleiothyridina peeosi. 
Myalina pemiformis. 
Myalina aff. M. arkansana. 
Modiola subelliptica. 
Deltopecten occidentalis. 
Pterinopeeten? sp. 
Pectinopsis n. sp. 
Pectinopsis n. sp. 
Pleurophorus aff. P. oblongus. 
Platyceras n. sp. 
Griffithides morrowensis? 



6377. 1,000 feet northeast of benchmark 5723 on Lincoln 
Highway south of Gold Hill: 



Triplophyllum sp. 
Polypora sp. b. 
Cystodictya sp. b. 

Productus ovatus var. minor. 
Avonia aff. A. arkansana? 
Spirifer opimus var. occiden- 
talis. 
Spiriferina transversa, 
Composita ozarkana. 
Cleiothyridina peeosi? 

6378. 1,000 feet west-northwest of benchmark 5723 on 
Lincoln Highway south of Gold Hill: 



Parallelodon aff. P. pergib- 

bosum. 
Avieulipecten sp. 
Astartella aff. A. compacta. 
Pleurophorus? sp. 
Phanerotrema? sp. 
Bulimorpha aff. B. chrysalis. 
Eotrochus? sp. 
Griffithides morrowensis? 



Rhipidomella aff. R. penniana. 

Derbya robusta. 

Productus cora? 

Productus ovatus var. minor. 

Productus n. sp. 

Productus sp. b. 

Avonia aff. A. arkansana. 



Spirifer opimus. 
Composita ozarkana. 
Cleiothyridina peeosi. 
Deltopecten occidentalis. 
Modiola subelliptica? 
Bellerophon aff. B. sublevis. 



6380. From dump 
Echinocrinus sp. 
Fistulipora sp. b. 
Stenopora sp. a. 
Batostomella sp. 
Fenestella sp. 
Polypora sp. a. 
Ptilopora? sp. 
Cystodictya sp. a. 
Rhipidomella aff. R. 

The preceding five 



of southern Ochre Spring: 

Chonetes arkansanus. 

Pustula globosa var. 

Spirifer opimus. 

Spirifer sp. 

Composita sp. 

Cleiothyridina peeosi. 

Deltopecten occidentalis? 

Griffithides morrowensis? 
penniana. Ostracoda indet. 
collections are from the western facies. 



MISSISSIPPIAlSr-PEasmSYLVANlJLN CONTACT 

The contact between the Mississippian and Penn- 
sylvanian in several places in Utah and Idaho has 
been described as unconformable. 80 In the Gold Hill 
quadrangle the presence of Pennsylvanian fossils in 
the Manning Canyon formation and Mississippian 
fossils in the underlying Ochre Mountain limestone, 
the variations in thickness of the Manning Canyon, 
and the peculiar character of the faunas found in three 
of the Manning Canyon collections would seem, in the 
absence of other evidence, to indicate that such an 
unconformity exists here at the base of the Manning 
Canyon. The contact between the Ochre Mountain 
and the Manning Canyon is well erposed only on the 
bottom level of the Cane Springs mine, but here the 
contact seems clearly to be gradational rather than 
unconformable. The explanation of this somewhat 
conflicting evidence may perhaps be furnished by the 
type locality of the Manning Canyon in the Oquirrh 
Mountains, 81 which contains late Mississippian fossils 
at its base and Pennsylvanian fossils near the top, the 
break occurring within the formation. 

OQCXRRH FORMATION (PENNSYLVANIA!* AND PERMIAN) 

The Oquirrh formation was named by Gilluly 82 for 
the Oquirrh Range, in Utah, where there is an un- 
usually thick series of Pennsylvanian rocks, similar 
stratigraphically to the rocks in Gold Hill. 

Distribution. — The Oquirrh formation has a wider 
distribution within the quadrangle than any other of 
the Paleozoic formations. Two large areas and several 
smaller ones are underlain chiefly by it. The southern 
of the two large areas extends from North Pass and 
Christiansen Canyons northward to the south side of 
Ochre Mountain and to Clifton. The northern area 
extends from Trail Gulch on Dutch Mountain to the 
western border of the quadrangle. Smaller areas are 
found near the eastern border of the quadrangle south 
of the continuation of Overland Canyon, immediately 
south and west of the town of Gold Hill; east of the 
Napoleon mine; and on the south side of Dutch 
Mountain. 



80 Blaekwelder, Eliot, New light on the geology of the Wasatch Mountains, Utah: 
Oeol. Soc. America Bull., vol. 21, pp. 530-533, 1910. Biehardson, O. B., The Paleo- 
zoic section in northern. Utah: Am. Jour. Sci., 4th ser., vol. 36, p. 413, 1913. Mans- 
field, Q. B., Geography, geology, and mineral resources of part of southeastern 
Idaho: U.S. Geol. Survey Prof. Paper 152, p. 73, 1927. 

* Gilluly, James, Geology and ore deposits of the Stockton and Fairfield quad- 
rangles, Utah: U.S. Geol. Survey Prof. Paper 173, pp. 32-34, 1932. 

1 1dem, p. 34. 



34 



GOLD HILL MINING DISTRICT, UTAH 



Lithotogy. — The Oquirrh formation, like the Mann- 
ing Canyon, has two faeies, which, however, are much 
more distinct than those in the Manning Canyon 
formation. The southern of the two large areas under- 
lain by the formation and the areas around the town 
of Gold Hill are composed chiefly of the central fades ; 
the areas west of Dutch Mountain, of the western 
faeies. The exposures of the formation on the south 
side of Ochre Mountain, on the north and northeast 
borders of Clifton Flat, and in Rodenhouse Wash are 
also of the western faeies. 

The central faeies is made up of several different 
kinds of rocks, and each rock type represented is 
repeated over and over again throughout the section, 
although individual beds are generally lenticular. 
This makes it impossible to break up the formation 
into subdivisions, a course that would have made the 
study of the geologic structure much more simple. 

This faeies is prevailingly sandy. Sandstones form 
perhaps half of the section, and sandy limestones and 
shales a large part of the remainder. Interbedded with 
these are numerous beds of limestone and dolomite and 
a few lenses of conglomerate. 

The sandstones are generally fine-grained rocks, 
rather dark gray on fresh fracture and deep reddish 
brown on weathered surfaces. They are not at all 
resistant to erosion, and in places where they are abun- 
dant there are few outcrops, the surface being mostly 
covered by a sandy soil or by small blocks of rock. 
Many of these beds contain varying amounts of shaly 
material or of caleite. Near the base of the formation 
the sandstones in some places show a distinct lamina- 
tion, which is in part due to the presence of thin films 
of carbonaceous matter similar to that which is so 
abundant in the underlying Manning Canyon forma- 
tion. Near the quartz monzonite the sandstones are 
bleached to a dull white color and are notably harder. 

The limestone beds vary greatly in appearance- 
Many are fine-grained, dark bluish gray on fresh frac- 
ture and light bluish gray on the weathered surface. 
Such beds usually contain silica, either in the form of 
sandy laminae or as chert nodules or lenses. Locally, 
especially on the east side of Blood Canyon and in the 
low hills south and southeast of the Midas mine, there 
is a great deal of thin-bedded platy limestone which 
is nearly black on fresh fracture and purplish on 
weathering. Such beds are commonly very fossilif- 
erous, containing especially large numbers of the char- 
acteristic Pennsylvanian fossil Fiisvlina. In many 
places K-inch layers of this limestone alternate with 
equally thin layers of brown sandstone and black chert. 
Near the intrusions the limestones, like the sandstones, 
are thoroughly bleached; and many beds have been 
completely replaced by silicate minerals. 

Dolomite beds are also found in many places. Some 
of these are clearly the result of a much later alteration 
of limestone; but others are, without much doubt, 



primary, in the sense that dolomitization occurred as a 
result of sedimentary processes. One of the most wide- 
spread of such dolomites is fine-grained bluish-gray 
rock, filled with round or spindle-shaped white dots, 
which, in part at least, represent poorly preserved 
Fusulinas. Other dolomites are similar to the beds 
of cherty limestone mentioned in the preceding para- 
graph, except for a slightly duller appearance. 

Locally the limestones and dolomites are conglom- 
eratic and contain pebbles as much as 6 inches in 
diameter. The pebbles are in part limestone or dolo- 
mite, but the greater proportion are chert. A speci- 
men of such a rock in which the chert fragments are un- 
usually small is illustrated in plate 5, F. This specimen 
is rather unusual in having an oolitic matrix, whereas 
generally the matrix is either fine-grained limestone 
or dolomite. Individual beds when traced along the 
strike may show a limestone matrix in one place and 
dolomite in another. Many of the conglomerate beds 
were found to pass into normal limestone or dolomite 
within a short distance, but others were traced along 
the strike for as much as 3 miles. 

Because of the angularity of the chert pebbles and 
also because of the presence of pebbles of limestone 
and dolomite, it would seem almost certain that the 
chert pebbles were deposited as such. If so, there are 
two possible sources for the pebbles — either from older 
chert-bearing rocks that were undergoing erosion at 
the time the conglomerates were being deposited or 
from a silica-rich layer deposited in essentially the 
same locality as the conglomerates and broken up by 
storm waves or currents, or perhaps by subaerial 
agencies brought into play by a temporary emergence 
before being covered by younger beds. In spite of 
the fact that the presence of limestone and dolomite 
pebbles is more easily explained by the first hypothesis, 
the second hypothesis seems the more attractive, be- 
cause of the restriction of the pebbles to individual 
beds and because of the extremely slight extent of 
some of the beds. If this is the true explanation, it 
indicates that the siliceous ooze from which some cherts 
are thought to form M may harden rather soon after 
deposition. 

The western faeies shows very little resemblance to 
the central. The amount of sandy material present 
is much smaller, and the chert-pebble and other con- 
glomerates are lacking. 

At the base of this faeies is a moderate thickness of 
light-colored sandstone, similar to that in the eastern 
faeies. This appears to thin toward the north, as the 
amount present in the northwestern part of Dutch 
Mountain is less than that found south of the 7,262- 
foot peak at the head of Pool Canyon. 

Above the sandstone is a succession of thick-bedded 
limestones, nearly 3,000 feet thick. These limestones 
are similar to those in the Ochre Mountain limestone. 



' Tarr, W. A., in TwenhoM, W. H., A treatise on sedimentation, p. 384, 1926. 



CAKBONIFEKOTJS SYSTEM 



35 



Thin beds of sandstone are usually associated with 
them and help to distinquish the two formations, as 
does the abundance of Fusulina in the Pennsylvanian 
limestone. Locally these small fossils are so numerous 
as to make up an entire bed. The distribution of chert 
throughout the limestone series is erratic rather than 
limited to two rather distinct horizons, as in the Ochre 
Mountain limestone. In some places the limestones 
have been dolomitized. The dolomitization shows no 
relation to the bedding or other features of sedimentary 
structure but rather has occurred near faults or minor 
folds. It has given the rock a duller and grayer 
aspect than normal. 

Above the massively bedded limestone is about 
4,500 feet of dolomite and sandstone, with only minor 
amounts of limestone. The dolomite is rather light 
gray and medium-grained. Many beds contain dark- 
gray chert nodules and stringers. Unlike the dolo- 
mites mentioned in the preceding paragraph, these beds 
are thought to be formed by sedimentary processes, 
as their distribution shows no relation to structural 
features and as the interbedded limestones where 
dolomitized have an altogether different appearance. 

The sandstones are for the most part medium- 
grained gray rocks which weather to tints of light 
reddish-brown. Almost all have a moderately large 
content of calcite as a cement. In one specimen of 
cross-bedded sandstone obtained near the base of this 
portion of the formation the quartz grains, together 
with a very few of plagioclase, were surprisingly 
angular, especially when it is considered that the 
nearest shore of the Pennsylvanian sea is supposed to 
have been at least 100 miles away. In the upper 
1,500 feet of the formation as exposed on each side of 
Deep Creek sandstones are much more abundant. 
These beds weather to vivid hues of red and yellow, 
but a large part of the coloring material is thought to be 
derived from the weathering of nearby volcanic rocks. 

The limestones that are found in the upper division 
are similar to those making up the lower division. 

One characteristic zone is found about 3,800 feet 
above the base of the upper division. This was one 
of the two distinctive horizon markers on the western 
facies, the upper contact of the limestone series being 
the other. It is a poorly exposed zone of extremely 
cherty and sandy limestone and usually appears at 
the surface as a bench covered with fragments of 
black chert. This bed occurs at several places in the 
area westward from the low-lying hills west of Dutch 
Mountain. 

Thickness, — No accurate measurement of the thick- 
ness of the Oquirrh formation was made, because of 
the difficulty of correlating precisely the various short 
sections unaffected by folding or faulting. The total 
thickness of the central facies could not be determined 
even if this were done, because the contact of this 
facies with the Permian was nowhere seen. Estimates 
from cross sections indicate a minimum thickness for 



this facies of 5,300 feet. The bottom and top of the 
western facies are both exposed in the northwestern 
portion of the area. A result which was obtained by 
piecing together estimates of thickness of the two 
divisions and which is believed to allow for the greater 
part of the folding and faulting points to a figure 
between 7,500 and 8,000 feet for the total thickness 
of this facies. 

Age and correlation. — Mr. Girty has divided the 
fossil collections from the Oquirrh formation into three 
groups, representing three different ages. Near the 
base of the formation in both the central and western 
facies, the fossils indicate a Pottsville or lower Penn- 
sylvanian age. The remainder of the central facies 
and the greater part of the western facies contain 
fossils characteristic of the higher Pennsylvanian. 
Finally, near the top of the western facies, the fossils 
are similar to those found in the overlying formation, 
which is of Permian age. Mr. Girty has kindly 
provided the following notes: 

A sharp demarcation exists between the higher Pennsylvanian 
faunas and the Permian faunas of the Gold Hill district. It is 
true that specific distinctions among the Compositas do not 
amount to much, so that C. mira closely resembles C. subliUta, 
and that Pustula subhorrida resembles, more or less closely, the 
species cited in these lists as Pustula aff . P. wallaciana, but either 
fauna, given a collection of reasonable size, can be recognized 
with ease and certainty. 

Naturally enough, this is less true of the faunas that occur in 
the higher Pennsylvanian and in the Pottsville. The fossils in 
the much disturbed strata of the Gold Hill district are not as a 
rule in a good state of preservation, so that specific differences, 
if not lost entirely, may have been overlooked. With a better 
understanding of individual species and a more complete 
knowledge of their range in the section, a more accurate dis- 
tinction between the Pottsville and post-Pottsville faunas could 
probably be drawn. As it is, small collections of poorly pre- 
served shells cannot be referred with any confidence. Consid- 
ered in a broad way, with the stratigraphic data and the paleon- 
tologic data supplementing each other, one rather well marked 
distinction appears to exist between these two faunas. Most of 
the collections from the higher Pennsylvanian contain Fusulina 
in more or less abundance, whereas not one of the Pottsville 
collections contains any of these shells. Of course there are 
other differences between the faunas, but this is the most 
obvious one and so far as facts are available the most practical 
one. The distinction thus suggested works only one way, how- 
ever. All the collections that contain Fusulina can be classed 
as higher Pennsylvanian, but not all the collections that fail to 
contain Fusulina can be classed as Pottsville, and of these, as 
already noted, certain small and nondescript collections must be 
assigned largely on the basis of their stratigraphic occurrence 
rather than upon the fossils which they contain. 

You are, I believe, recognizing a central and a western facies 
in the rock characters of the Pennsylvanian of the Gold Hill 
district. I am unable to make a like distinction in the faunas, 
though here again a nicer discrimination of species and closer 
attention to forms like the Bryozoa, to which I have been able 
to give only a summary treatment, might show differences that 
1 have failed to recognize. It is true that in checking up the 
faunas that represent the two lithologic phases a number of 
species occur in one list and not in the other and especially a 
large number of species have been found in the central facies, 
that appear to be absent from the western facies, but on the 
other hand the central collections outnumber the western 



36 



GOLD HILL MINING DISTBICT, TJTAH 



collections almost 2 to 1. Besides this, several of the western 
faunae possess striking and individual peculiarities which 
distinguish them as much from other western faunas as from 
any of the central faunas. In comparisons of this sort a species 
to be significant should occur repeatedly in one fauna and not 
at all in the other. In the present series of collections a single 
occurrence, let us say, in the central fauna might stand against 
about 22 nonoccurrences in the same fauna and about 15 non- 
occurrences in the western fauna, so that it would not mean very 
much. The only striking instance of such a difference that 
would seem to be significant is invested in the form listed as 
Rhynchopora sp., which has been found only in the central 
fauna and which has been noted in five collections. In the 
present state of our knowledge, then, the central and western 
faunas do not differ recognizably, though differences that are 
now obscure may actually exist. 

Collections of Pottsville age 



6079. About one-third mile 
side of Blood Canyon: 
Derbya robusta. 
Productus n. sp. 
Productus ovatus var. minor. 
Spirifer opimus var. oceiden- 

talis. 
Spiriferina spinosa. 

6326. Blood Canyon, 2,500 
Echinocrinus sp. 
Fistulipora sp. 
Derbya robusta? 
Productus semireticulatus. 
Avonia aff. A. arkansana. 



southeast of hill 6837, on west 

Composita ozarkana. 
Cleiothyridina peeoei. 
Aviculipecten? sp. 
Lima? sp. 
Griffithides morrowensis? 

feet north-northwest of spring: 
Spirifer opimus. 
Composita ozarkana. 
Cleiothyridina pecosi. 
Conoeardium sp. 



6328. Blood Canyon, 5,000 feet west-northwest of spring: 



Derbya robusta? 
Productus n. sp. 
Spirifer Opimus var. 
talis. 



occiden- 



Spirifer sp. 
Spiriferina spinosa. 
Composita ozarkana. 
Cleiothyridina pecosi. 



The 



The preceding three lots came from the central facies. 
following lots represent the western facies. 

6064, 6070, 6372. 3,100 feet southeast of benchmark 6163, at 
north end of Clifton Flat: 



Sponge spicules. 

Fistulipora sp. b.? 

Stenopora sp. c. 

Rhombopora lepidodendroides. 

Leioclema sp. b. 

Fenestella aff, F. tenax. 

Orbiculoidea meekana? 

Derbya robusta. 

Chonetes choteauensis. 

Productus n. sp. 

Productus ovatus var. minor. 

Productus cora. 

Avonia aff. A. arkansana? 

Pustula sp. 

Dielasma sp. 



Spirifer opimus. 
Spirifer opimus var. occiden- 
tals? 
Spiriferina transversa. 
Composita ozarkana. 
Cleiothyridina pecosi. 
Hustedia sp. 
Sehizodus? sp. 
Deltopecten occidentalis. 
Deltopecten occidentalis var. 
Deltopecten n. sp. 
Streblopteria n. sp. 
Pterinopecten? sp. 
Pectinopsis jennyi? 
Pectinopsis n. sp. 



6333. Just west of saddle west of 7,262-foot summit on south 



side of Dutch Mountain: 
Cryptozoon? 
Favosites n. sp. 
Fistulipora sp. b.? 
Stenopora sp. b. 
Anisotrypa sp. 
Leioclema sp. b. 



Schizophoria texana. 
Derbya robusta. 
Productus n. sp. 
Productus sp. a, 
Productus ovatus var. minor. 
Avonia aff. A. arkansana. 



Pustula semipunctata. 
Pugnoides n, sp, 
Dielasma aff. D. bovidens. 
Spirifer opimus. 
Spirifer opimus var. occiden- 
talis. 
Spiriferina spinosa. 



Composita ozarkana. 
Composita subquadrata var. 

lateralis? 
Cleiothyridina pecosi. 
Hustedia sp. 
Edmondia? sp. 
Pleurophorus? sp. 



6334. South of 6333, near sill of quartz monzonite porphyry: 



Orbiculoidea meekana? 
Spirifer opimus var. occiden- 
talis. 
Spiriferina spinosa, 
Composita ozarkana. 



Acanthopecten carboniferus. 
Pectinopsis n. sp. 
Deltopecten occidentalis. 
Myalina perniformis. 
Griffithides morrowensis? 



6335. About same horizon as 6334 and a few hundred feet 
west of it: 



Leioclema sp. a. 

Schizophoria texana. 

Derbya robusta. 

Productus ovatus var. minor. 

Avonia aff. A. arkansana. 

Spirifer opimus var. occiden- 
talis. 
6336. About 100 feet st-ratigraphically above 6335: 



Composita ozarkana. 
Cleiothyridina pecosi. 
Acanthopecten carboniferus. 
Pinna aff. P. peracuta. 
Griffithides morrowensis? 



Orbiculoidea meekana ? 

Crania modesta. 

Derbya robusta. 

Productus n. sp. 

Productus aff. P. gallatinensis. 

Pugnoides osagensis var. per- 

costata. 
Dielasma sp. 



Spirifer opimus var.occiden talis. 
Spiriferina spinosa. 
Composita ozarkana. 
Composita subquadrata var. 

lateralis. 
Cleiothyridina pecosi. 
Myalina perniformis. 
Griffithides morrowensis? 



6337. About 50 feet strati graphically above 6336: 



Echinocrinus sp. 
Derbya robusta. 
Productus n. sp. 
Productus cora. 
Productus ovatus var. minor. 
Productus aff. P. gallatinensis. 
Avonia aff. A. arkansana. 
Pugnoides n. sp. 
Spirifer opimus var. occiden- 
talis. 
Spiriferina spinosa. 



Composita subquadrata var. 

lateralis? 
Cleiothyridina pecosi. 
Hustedia mormoni? 
Parallelodon? sp. 
Aviculipecten sp. 
Pterinopecten sp. 
Deltopecten occidentalis. 
Euomphalus? sp. 
Griffithides morrowensis? 
Fish tooth. 



Composita ozarkana. 
6338. About 50 feet stratigraphically above 6337: 



Syringopora sp. 
Spirorbis carbonaria. 
Ortonia sp. 
Hederella sp. 
Stenopora sp. b. 
Rhombopora lepidodendroides. 
Derbya robusta. 
Chonetes platynotus? 
Productus cora. 



Productus nolani. 
Productus sp. a. 
Avonia aff. A. arkansana. 
Dielasma aff. D. bovidens. 
Spirifer opimus var. occiden- 
talis. 
Composita ozarkana. 
Cleiothyridina pecosi. 
Griffithides morrowensis? 



6349. West side of Dutch Mountain near base, 3,500 feet 
east-southeast of benchmark 5369 on Ferber Road: 



Productus n. sp. 
Spirifer opimus var. occiden- 
talis. 
Spirifer sp. 
Spiriferina spinosa. 
Composita ozarkana. 
Cleiothyridina pecosi? 
Myalina perniformis. 
Modiola? sp. 



Bucanopsis n. sp. 
Naticopsis n. sp. 
Pleurotomaria aff. P. beck- 

withana. 
Schizostoma catilloides? 
Platyceras sp. 
Griffithides morrowensis? 
Paraparchites sp. 



CABBONIFEBOTJS SYSTEM 



37 



8078. South side of Ochre Mountain, 4,250 feet north- 
northwest of benchmark 6149 on Lincoln Highway: 



Schizophoria texana. 
Productus ovatus var. minor. 
Avonia aff. A, arkansana. 



Pustula globosa var. 
Spiriferina spinosa. 
Composita ozarkana. 



6273. 1,000 feet north of hill 5688, at northwest tip of Dutch 
Mountain: 



Schizophoria texana. 
Productus nolani var. 
Productus ovatus var. minor. 
Spirifer opimus. 
Spiriferina spinosa. 

6316. About half a mile east-northeast of New York claim, 

on southwest side of Dutch Mountain: 



Spiriferina transversa. 
Composita ozarkana. 
Cleiothyridina pecosi? 
Pleurophorus sp. 



Llngula carbonaria? 
Orbieuloidea meekana? 
Productus n. sp. 
Productus cora. 
Spirifer opimus. 
Spiriferina spinosa. 



Composita ozarkana. 
Cleiothyridina pecosi. 
Myalina perniformis. 
Deltopecten occidentalis. 
Platyceras sp. 
Griffithides morrowensis? 



6350. About 500 feet east of 6316: 



Productus semiretieulatus. 



Spirifer opimus var. occiden- 
talis. 



6353. West side of Dutch Mountain, 2,000 feet northeast of 
hill 6518: 



Productus n. sp. 
Spirifer opimus var. occiden- 
talis. 

6375. Same locality as 6374 

but just above road: 

Lingula carbonaria? 

Derbya robusta. 

Productus n. sp. 

Productus ovatus var. minor. 

Productus sp. b. 

Avonia aff. A. arkansana. 

Avonia aff. A. arkansana var. 

Spirifer opimus. 

Spirifer opimus var. occiden- 
talis? 

Spiriferina transversa. 



Spirifer sp. 
Composita ozarkana. 

(Manning Canyon formation) 

Spiriferina spinosa. 
Composita ozarkana. 
Cleiothyridina pecosi. 
Hustedia sp. 

Edmondia aff. E. mortonensis. 
Edmondia aff. E. circularis. 
Deltopecten occidentalis. 
Pectinopsis n. sp. 
Bellerophon aff. B. sublevis. 
Griffithides morrowensis? 



6376. About 75 feet higher than 6375: 



Fistulipora sp. a. 
Derbya robusta. 
Chonetes choteauensis? 
Productus n. sp. 
Productus cora. 



Productus ovatus var. minor. 
Avonia aff. A. arkansana. 
Spirifer opimus var. occiden- 
talis. 



Collections of higher Pennsylvanian species 

The following 24 lots came from the central fades. 

6047. One-fourth mile northwest of peak 7660, in saddle on 
divide between Overland Canyon and North Pass Canyon: 



Campophyllum torquium? 
Rhombopora sp. 
Chonetes aff. C. granulifer. 



Marginifera? sp. 
Composita? sp. 

Griffithides? sp. 



6048. East-west spur west of 7,300-foot closed contour on 
main ridge line of Deep Creek Mountains, about 200 feet 
stratigraphically below westernmost outcrops: 



Stenopora sp. 
Derbya? sp. 
Spirifer opimus. 



Spiriferina spinosa. 
Composita subtUita. 



6049. Same as 6048, about 100 feet stratigraphically below 

6058: 



Fusulina sp. 

Sponge? 

Campophyllum torquium. 

Polypora sp. 



Rhombopora 1 e p i d o d e n - 
droides. 

Marginifera splendens? 
Hustedia mormoni. 



6050. 1,000 feet north of 6058: 



Spiriferina kentuckyensis. 
Composita subtilita. 



Fenestella sp. 
Rhombopora sp. 
Spirifer rockymoritanus. 

6055. Same spur as 6048 but about 400 feet stratigraphically 
lower: 



Polypora sp. 
Composita subtilita. 

Griffithides major? 



Fusulina sp, 

Campophyllum kansasense? 
Echinocrinus sp. 
Stenopora sp. 

6056. 800 feet west-southwest of peak 7472, on main ridge 
line of Deep Creek Mountains: 

Fusulina sp. | Rhombopora sp. 

6057. Same spur as 6056 but about 200 feet stratigraphically 
lower: 

Syringopora n. sp. 

6058. Same spur as 6056 but about 500 feet stratigraphically 
lower: 

Syringopora sp. Plagioglypta? sp. 

Campophyllum torquium. 

6066. 3,100 feet southeast of benchmark 6163 on Lincoln 
Highway: 



Echinocrinus sp. 
Spirifer opimus. 



Spiriferina kentuckyensis. 
Composita subtUita. 



6071. 700 feet north-northwest of benchmark 5855 on Lincoln 
Highway: 
Campophyllum sp. | Crinoid stems. 

6073 and 6077. Near southeast corner of sec. 17, T. ft S., R. 
19 W. (unsurveyed) : 



Triplophyllum sp. 
Michelinia sp. 
Echinocrinus sp. 
Fenestella aff. F. tenax. 
Productus cora. 
Pustula aff. P. biseriata. 
Girtyella? sp. 



Spirifer opimus. 
Cleiothyridina pecosi. 
Aviculipecten aff. A. colorado- 

ensis. 
Pinna? peracuta. 
Paraparchites sp. 
Kirkbya sp. 



6074. About three-quarters of a mile west-southwest of Mon- 
tezuma Peak: 



Rhombopora sp. 

Marginifera splendens? 



Rhynehopora sp. 
Spiriferina? sp. 



6076. Summit of peak 5800, half a mile southwest of U.S. 
Mineral Monument no. 7: 



Fusulina sp. 
Syringopora sp. 
Syringopora? (n. gen.?) sp. 
Campophyllum? sp. 

6290. South of mouth of Uiyabi Canyon: 



Echinocrinus sp. 
Productus cora. 
Pleurotomaria? sp. 



Productus cora. 
Productus semiretieulatus. 



Fusulina sp. 
Syringopora sp. 
Zaphrentis sp. 

6330. Southeast flank of Montezuma Peak, near mouth of 
gulch in which road leads westward to Midas mine: 
Fusulina sp. | Schwagerina? sp. 

6357. Lower slopes of center spur in Sheridan Canyon: 



Stenopora sp. 
Derbya robusta? 



Spirifer opimus var. occiden- 
talis. 
Composita subtilita. 



38 



GOLD HILL MINING DISTEIGT, UTAH 



6358, About 200 feet stratigraphically lower than 6357: 



Syringopora multattenuata. 
Campophyllum kansasense? 
Stenopora aff. S. ramosa. 
Rhombopora sp. 



Produotus semireticulatus. 
Spirifer sp. 
Composita subtilita. 



6359. Abaut 100 feet stratigraphically lower than 6358: 



Lophophyllum profundum? 
Produetus semireticulatus. 
Pustula aff. P. semipunctata. 
Pustula n. sp. aff. P. wal- 
laoiana. 



Rhynchopora sp. 
Squamularia perplexa? 
Cleiothyridina peeosi. 



6360. About 100 feet stratigraphically lower than 6359: 



Fusulina sp. 
Syringopora sp. 
Campophyllum kansasense? 
Rhombopora sp. 
Produetus cora. 
Produetus semireticulatus. 



Marginifera splendens. 
Marginifera lasallensis? 
Rhynchopora sp, 
Spiriferina spinosa? 
Pleurotomaria sp. 
Omphalotrochus? sp, 

6361. About 300 feet stratigraphically lower than 6360: 



Produetus cora. 

Pustula semipunctata var. 



Syringopora aff. S. multat- 
tenuata. 
Rhombopora sp. 

6362. Just west of intersection of the spur of 6357 with 
main ridge line: 



Fusulina sp. 

Syringopora aff. S. multat- 
tenuata. 
Campophyllum torquium. 
Fenestella sp. 
Polypora sp. 
Rhombopora sp. 

6363. About a quarter of a mile south of 6362: 



Rhipidomella aff. R. carho- 

naria. 
Chonetes sp. 
Rhynchopora sp. 
Spiriferina spinosa. 
Omphalotrochus sp. 



Syringopora? sp. 
Echinocrinus sp. 
Enteletes? n. sp. 
Derbya aff. D. multistriata. 
Produetus? sp. 



Spirifer n. sp.? 
Spiriferina spinosa. 
Ambocoelia planieonvexa var. 
Composita subtilita. 
Pleurotomaria sp. 



6364. North of road leading to cabin just northeast of 
benchmark 5855, at southeast corner of Clifton Flat: 



Schizophoria n. sp. 
Meekella? sp. 

Chonetes aff. C. geinitzianue. 
Produetus cora. 
Produetus n. sp. 
Produetus semireticulatus. 
Pustula aff. P. semipunctata. 
Rhynchopora sp. 
Dielasma bovidens? 
Spiriferina spinosa var. 



Fusulina sp. 

Syringopora aff. S. multat- 
tenuata. 

Campophyllum torquium? 

Cyathophyllum subeaespito- 
sum? 

Echinocrinus sp. 

Polypora sp. 

AcanthoclaHia sp. 

Rhombopora lepidodendroides. 

Rhombopora sp. 

Cyetodictya aff. C. inaequi- 
marginata. 

The next 15 lots came from the western facies of the formation. 

6317. 3,000 feet south of benchmark 5963 on Ferber Road: 
Produetus semireticulatus. I Avonia? sp. 

63 18. 4,250 feet southwest of benchmark 5963 on Ferber Road : 

Produetus sp. | Spirifer aff. S. triplicate. 

6320. Southwest side of Dutch Mountain, 1,250 feet west of 
5,964-foot point: 



Schizophoria? sp. - 
Produetus cora. 
Produetus semireticulatus. 
Avonia? sp. 



Spirifer opimus var, oeeiden- 

talis. 
Composita subtilita. 



6321. West side of Dutch Mountain 4,000 feet due west of 
6320: 



Stenopora sp. 
Rhombopora sp. 
Rhipidomella aff. R. carbo- 
naria. 



Produetus sp. 
Spirifer sp. 



6331. A quarter of a mile north-northeast of A B claim, west 
side of Dutch Mountain: 



Fusulina sp. 
Favosites? sp. 
Triplophyllum sp. 



Rhombopora sp. 
Produetus cora. 



6332. A quarter of a mile east of 6331: 



Fusulina sp. 
Syringopora sp. 
Campophyllum torquium. 
Fistulipora sp. 
Stenopora aff. S. carbonaria. 
Rhombopora sp. 
Derbya? sp. 

6344. 1 mile southwest of hill 6060 (southern one of Twin 
Peaks) west of Dutch Mountain: 



Produetus semireticulatus. 
Produetus n. sp.? 
Dielasma aff. D. bovidens. 
Spirifer triplicatus. 
Composita subtilita. 
Omphalotrochus sp. 



Fusulina sp. 



Cyathophyllum 
sum? 



subcaespito- 



6345. About 250 feet stratigraphically below 6344: 

Cladochonus sp. Marginifera splendens? 

Rhombopora sp. Spiriferina spinosa? 

Derbya? sp. 

6346. In gulch north of 6344 and 6345 and stratigraphically 
between them: 

Syringopora sp. | Campophyllum sp. 

6351. Near hill 6360, on west side of Dutch Mountain: 



Marginifera splendens. 
Spiriferina spinosa? 



Streblotrypa sp. 
Rhombopora sp. 
Polypora sp. 

6352. 2,000 feet north-northeast of hill 6518, on west side of 
Dutch Mountain: 



Fistulipora sp. 
Stenopora sp. 
Rhombopora sp. 
Produetus semireticulatus. 
Produetus cora. 



Pustula n. sp. aff. P. walla- 

ciana. 
Spirifer opimus var. oeciden- 

talis. 



6354 and 6354a. 1,000 feet west of hill 6518, on west side of 
Dutch Mountain: 

Crinoid columnals. Astartella n. sp. 

Echinocrinus sp. Goniospira? sp. 

Lingula carbonaria. Zygopleura? sp. 
Tegulifera? sp. 

6379. Same locality as 6378, of Pottsville age, but about 75 
feet stratigraphically higher: 



Fistulipora sp. 
Rhombopora sp. 
Derbya robusta? 
Produetus cora, 
Produetus semireticulatus. 
Produetus sp. 



Avonia sp 

Pustula n. sp. aff. P. walla- 

ciana. 
Spirifer aff. S. triplicatus. 
Squamularia perplexa. 
Composita subtilita. 



6583. North side of gulch from 6346: 

Fusulina sp. I Produetus semireticulatus. 

Produetus cora. j 

In addition to these lots two others were collected 
on the south side of North Pass Canyon in rocks 



CARBONIFEEOUS SYSTEM 



39 



thought to be of this age, for the reasons given in the 
section on the Ochre Mountain limestone. It is 
entirely possible that these rocks are of Mississippian 
rather than Pennsylvanian age, but in the absence of 
the further field investigations that would be necessary 
to prove their correct assignment the two lots are 
listed here. 

6383. Lower eastern slopes of hill 6267, on south side of 
North Pass Canyon: 



Trip lophy Hum sp. 
Productus ovatus. 
Produotus semireticulatus. 



Productus aff. P. arcuatus. 
Spirifer aff. S. increbescens. 
Composita? sp. 

6384. Same as 6383 hut just below summit: 

Pustula aff. P. biseriata. 
Pugnoides, several sp. indet. 
Cranaena aff. C. globosa. 
Spirifer aff. S. grimesi. 



Composita? sp. 
Griffith ides n. sp. 



Eehinocrinus sp. 

Fenestella sp. 

Chonetes aff. C. oklahomensis. 

Productus ovatus. 

Pustula aff. P. millespinosa. 

Pustula aff. P. concentriea, 

Pustula n. sp. 

Mr. Girty writes as follows regarding these two 
collections : 

The fauna of lot 6383, which was included among the Ochre 
Mountain collections, is noncommittal. It might be Peimsyl- 
vanian; the faunal evidence is concessive but not confirmatory. 
The same question was raised with reference to lot 6384. 
Though the fauna comprised in this lot is peculiar, it fits in 
reasonably well with the Woodman fauna and very badly with 
the Pottsville or post-Pottsville as those faunas are at present 
known in the Gold Hill district. 

Collections of Permian age 
These lots all came from the western facies. 

6339. Half a mile south-southeast of benchmark 5544, in 
Tank Wash: 



Derbya sp. 

Pustula aff. P. signata. 
Pustula subhorrida. 
Pustula subhorrida var. ruga- 
tula. 



Camarotoechia? sp, 
Heterelasma? sp. 
Spiriferina pulchra? 
Composita sp. 
Cleiothyridina n. sp. 

6340. Just west of benchmark 5544 on Ferber Road: 



Leioclema? sp. 

Derbya aff. D. multistriata. 

Pustula nevadensis. 

Pustula aff. P. montpelierensis. 



Pustula subhorrida. 
Strophalosia? n. sp. 
Dielasma? sp. 
Cleiothyridina n. sp. 



6341. A quarter of a mile west of 6340, about 50 feet strati- 
graphically lower: 



Derbya aff. D. robusta. 
Pustula nevadensis? 
Pustula subhorrida. 



Pustula subhorrida var. ruga- 
tula? 



6342. Near peak 5850, west of 6341: 



Pustula subhorrida var. ruga- 
tula? 
Spiriferina pulchra. 



Leioclema? sp. 
Pustula nevadensis. 
Pustula subhorrida. 

6343. 1,000 feet west of 6342: 

Pustula subhorrida? | Composita subtilita. 

6356. 1,000 feet west of benchmark 5097 on Deep Creek, on 
north side of gulch: 



Pustula subhorrida? 
Productus sp. 



Composita subtilita? 



The collections here referred to the Permian are cited with 
varying degrees of confidence. Some of the collections are 
small or poorly preserved or both. Some also fail to contain 
the most characteristic species of the Spiriferina pulchra fauna 
and present a facies that is appreciably different though related. 
However, all the collections that possess individual or distinctive 
characters show a closer relationship to the Permian than to the 
Pennsylvania!! faunas of the region. 

The formation as a whole is difficult to correlate 
with formations found in other districts. It is most 
closely comparable to the Oquirrh formation in the 
Stockton and Fairfield quadrangles u but appears to 
contain older beds at the base and younger ones at 
the top. It is less confidently correlated with the 
Weber quartzite 85 in the Wasatch Range and with the 
Ely limestone 86 of Nevada. 

OEBSTEE FORMATION (PERMIAN) 

Distribution. — The Gerster formation crops out 
within the Gold Hill quadrangle only in the narrow 
area west of Deep Creek. There is a small exposure 
on the south end of the hill west of benchmark 4984, 
but the largest outcrop occurs on the south side of 
Gerster Gulch, from which the formation is named. 
Another small area partly covered by volcanic rocks 
was found west of benchmark 5097, about a quarter 
of a mile beyond the western border of the quadrangle. 
All these outcrops are placed without hesitation in the 
western facies of the Carboniferous. 

Lithology. — The Gerster formation is made up largely 
of thin-bedded sandy and shaly limestones, which are 
brownish gray on fresh surfaces and weather to yellow- 
ish brown or pink. The beds are from 2 inches to 1 
foot thick and generally have a concentration of sandy 
or shaly material along the bedding planes. These 
beds are richly fossiliferous in all the exposures seen. 
Locally thin beds of sandstone may be found, and in 
most exposures moderately thick beds of cherty lime- 
stone are also present. 

These beds are sharply set off from the underlying 
sandstones and dolomites of the Oquirrh formation by 
their lithology and especially by their abundant fossil 
content, which was the basis for mapping the contact 
between the two. In most places there is a thin bed 
of sandstone at this contact, but no other evidence of 
discordance was found, and Mr. Girty's determination 
of a Permian age for some of the fossil collections in the 
upper portion of the Oquirrh formation suggests that 
the lithologic break is of minor importance. 

Thickness. — East of Deep Creek the Gerster forma- 
tion has been removed by pre-Eocene (?) erosion, and 
to the west all but one of the outcrops are overlain 
by the Eocene (?) or by volcanic rocks. In the gulch 
south of that leading to Ferber, however, a eloser meas- 
ure of the original thickness may be obtained, as here 

'• Gillaly, James, Geology and ore deposits of the Stockton and Fairfield 
quadrangles, Utah: U.S. Qeol. Survey Prof. Paper 173, pp. 34-38, 1932. 

» Boutwell, J. M., Geology and ore deposits of the Park City district, Utah: 
U.S. Qeol. Survey Prof. Paper 77, pp. 45-49, 1912. 

» Spencer, A. C„ Geology and ore deposits of Ely, Nev.: U.S. Geol. Survey Prof 
Paper 98, pp. 27-28, 1917. 



40 



GOLD HILL MINING DISTRICT, UTAH 



a small remnant of Lower Triassie limestone is found 
above the Gerster formation. In this place the thick- 
ness is about 600 feet. 

Age and correlation. — Four fossil collections from the 
Gerster formation have been referred by Mr. Girty to 
the Spiriferina pulchra zone of the Permian. His 
identifications are as follows: 

6061 and 6355. Half a mile west-northwest of benchmark 
5097 on Ibapah-Wendover road; 



Sponge. 
Clionolithus? sp. 



Pistulipora n. sp. 
Leioclema sp. 



Polypora sp. 

Derbya aff. D. multistriata. 

Chonetes n. sp. aff. C. geinitz- 
ianus. 

Productus longus. 

Pustula subhorrida var. ruga- 
tula? 

Strophalosia? sp. 

Strophalosia? n. sp. 

Spirifer pseudocameratus. 

Spiriferina pulehra. 

Spiriferina aff. S. kentuckyensis. 



Productus multistriatus. 
Pustula nevadensis? 
Pustula nevadensis var. 
Pustula subhorrida, 
Pustula subhorrida var. 
Composita mira. 
Hustedia mormorn? 
Deltopeeten n. sp. 
Deltopeeten sp. 
Deltopeeten sp. 
Pteria? sp. 



Oquirrh Range, 
Utah (Gilluly) 



Eureka, Nevada 
(Hague) 



Upper Coal Meas- 
ures limestone 



Weber 
conglomerate 



Lower Coal 

Measures 

limestone 



Diamond 

Peak 
quartzite 




Permian 



White Pine 
shate 



Devonian 



Pennsylvanian 



BASE 



Upper 
Mississippian 



Ely 
limestone 



Criainman shate 



Pennsylvanian 



OF 



Joana limestone 

prr 




Pennsylvanian 



WM^r-' 



"Madison 

" stone 



PENNSYL- 



VANIAN 

Upper 
Mississippian 



Oquirrh 
formation 



Mannmgqanyon 
formation 



Great Blue 
limestone 




Devonian 



Permian - 



Pennsylvanian 



Cottonwood- 
i Park City, Utah 
k \( Calkins- Boutwell) 

Triassie 



Upper 
Mississippian 



Park City 
formation 



Webar 
quaftzite 



Limestone 



Cambrian 



Devonian 
Fhhjke 6. — Correlation of Carboniferous formations in an east-west belt from Eureka, Nev., to the Cottonwood-Park City area, Utah. 



CARBONIFEROUS SYSTEM 



41 



6278. 3,000 feet west-northwest of benchmark 4984 on Ibapah- 
Wendover road: 



Derbya aff. D, multistriata. 
Pustula subhorrida? 

Spiriferina pulchra. 
Spiriferina aff. S. kentueky- 
ensLs. 



Hustedia? sp. 
Deltopecten n. sp. 
Bellerophon? sp. 
Euphemus? sp. 



6279. 1,500 feet south of 6278: 



Leioclema sp. 

Domopora? sp, 

Chonetes n. sp. aff. C. geinitz- 

ianus. 
Productus multistriatus. 
Pustula nevadensis. 



var. ruga- 



Pustula subhorrida. 
Pustula subhorrida 

tula. 
Spiriferina pulchra. 
Composita mira. 
Acanthopeeten? coloradoensls? 



of the Ely district, Nev. 89 Bocks of this age appear 
to have been rather generally removed by erosion in 
the region west of the Wasatch Mountains. 

CORRELATION OF THE CARBONIFEROUS FORMATIONS 

Figures 6 and 7 summarize the correlations that have 
been made for the Carboniferous formations in the 
Gold Hill area. Figure 6 includes districts in an east- 
west belt through Gold Hill, and figure 7 districts 
in a northeasterly belt, but the variations shown by 
the Carboniferous formations are quite unlike those 
shown by the pre-Carbonif erous formations in the same 
belt (figs. 3 and 4), In the east-west belt, for example, 

Gold Hill quadrangle, 
Utah (Nolan) 



Pioche district, 
NevadafWestgate) 



Frisco district, 
Utah(Butler) 




Pennsylvania!! 



Pennsylvanian 




Talisman quartzite 



Elephant 
limestone 



Topache 
limestone 



Devonian 



Devonian 



Lower 
Missfssippian 
Bristol Pass 
imestone 



2,000 



i i i i i i i 



Vertical scale 




Lower - 
Misslssippian \ 



4,000 Feet 



Gerster 
formation 



Oquirrh 
formation 



Madison limestone 
Devonian 




Randolph quad- 
rangle, Utah 
(Richardson) 



Pennsylvanian 




J"mote 7. — Correlation of Carboniferous formations in a northeast-southwest belt from Pioche, Nev., to the Eandolph quadrangle, Utah, 



The Spiriferina pulchra fauna- is found in the Park 
City formation of the Wasatch Mountains 87 and the 
Phosphoria formation of southeastern Idaho. 88 A 
similar fauna was also found in the Arcturus limestone 



«» Boutwell, J. M., Geology and ore deposits of the Park City district, Utah: U.S. 
Goal. Survey Prof. Paper 77, pp. 49-52, 1912. 

" Mansfield, O. E., Geography, geology, and mineral resources of part of south- 
eastern Idaho: U.S. Qeol. Surrey Prof. Paper 152, pp. 78-81, 1927. 

35311—35 i 



the thickness of the pre-Carboniferous formations in- 
creases rather regularly from east to west, whereas 
the Carboniferous formations show a pronounced thick- 
ening from the Cottonwood-Park City area to the 
Oquirrh Range, a thinning thence westward to Ely, 
and another thickening at Eureka. This change is 

" Spencer, A, C, Geology and ore deposits of the Ely district, Nev.: U.S. Gebl. 
Survey Prof. Paper 96, p. 28, 1917. 



42 



GOLD HILL MINING DISTRICT, UTAH 



thought to be the result of the formation of a land area 
in western Nevada in late Paleozoic time about on the 
site of maximum sedimentation in pre-Carboniferous 
time, which resulted in the shifting of this area of 
maximum sedimentation eastward into Utah. 90 

The figure for the northeast belt of Carboniferous 
formations is also quite different from the correspond- 
ing figure for the pre-Carboniferous, owing in part to 
the substitution of the relatively easterly Frisco 
section for that of the House Range, which contains 
no Carboniferous beds, and in part to the incomplete- 
ness of the Pioehe section. The thinness of the section 
in the Randolph quadrangle, however, suggests that 
if more complete data were available the regularity 
shown by the pre-Carboniferous formations in this 
zone would not be found. 

IOWEE TRIASSIC HMESTONES 

About 3,000 feet west of benchmark 4984 on Deep 
Creek, on the south side of the gulch, there is a small 
outcrop of brown-weathering limestone that contains 
numerous specimens of an ammonite related to 
Meekoceras. This outcrop is just west of the Gold 
Hill quadrangle. Its thickness is less than 50 feet. 
The contact of these limestones with the Gerster 
formation is concealed by gravel in the gulch, but the 
two are essentially conformable in strike and dip. In 
the report on the Park City district, 91 to the east, the 
Triassic is stated to overlie the Permian conformably, 
although one of the cross sections given by Boutwell 
(B-B', pi. 27) shows an unconformity at this horizon. 
In the Frisco district no unconformity was recognized 
in the field, although it is suggested that one may be 
present. 92 Mr. Girty has provided the following notes 
upon the fossils coEected: 

This collection contains fossils of two types — small gastropods 
and large ammonites. Specimens are abundant but badly 
preserved. Very few of the gastropods show even the most 
general features of configuration. Some of them are apparently 
naticoid shells and suggest Naiica lelia, but nothing more 
definite can be said of them. Of the ammonites also but little 
can be said save what is very general in character. Most if 
not all of them are discoidal in shape and more or less strongly 
evolute. Some have plicated sides; others are plain. Some have 
a narrowly rounded venter; others a venter truncated by a 
groove. The suture is shown by but few specimens and not 
completely and in detail by any of them. One shows the suture 
in detail but only in small part. The saddles are simple and 
rounded; the lobes fimbriated — evidently the suture is of the 
Meekoceras type. Inasmuch as a fairly complete knowledge of 
the suture is required for a close generic identification, even 
the best of these specimens cannot be classified generically, and 
it has seemed futile to attempt specific identifications. Of 
these specimens, however, it may fairly be said that most if 
not all of them are probably ammonites of the Meekoceras 

» Nolan, T. B., A late Paleozoic positive area in Nevada: Am. Jour. Sci., 8th ser., 
vol, 18, pp. 153-161, 1928. 

» Boutwell, J. M., Geology and ore deposits ot the Park City district, Utah: 
U.S. deal. Survey Prof. Paper 77, pp. Jl-52, 1912. 

» Butler, B. S., Geology and ore deposits of the San Francisco aod adjacent 
districts, Utah: U.S. Geol, Survey Prol. Paper 80, p. 37, 1913. 



group and that they probably represent several related genera 
or subgenera and an equal or larger number of species. This 
conclusion is closely connected with the stratigraphic occurrence 
of the fauna, with its utter unlikeness to the Permian fauna of 
the underlying beds, and with its close resemblance in type and 
preservation to the Lower Triassic faunas of this general region, 
which abound in shells of the Meekoceras group, many of them 
closely resembling in configuration the shells in this collection. 

OTCQNFOBMITY AT THE BASE OF THE EOCENE (?) 

Sedimentary rocks belonging to the Jurassic and 
Cretaceous periods were not found in the quadrangle, 
and the area was presumably being eroded during at 
least part of the time between the Triassic and the 
Tertiary. This erosion is shown by the unconformity 
between the Eocene (?) and older rocks. A conglom- 
erate containing boulders of the older rocks is found 
at the base of the Eocene (?), and the conglomerate 
itself in various places rests upon the Triassic lime- 
stones, the Gerster formation, and the Oquirrh 
formation. 

TERTIARY SYSTEM 

WHITE SAGE FORMATION (EOCENE?) 

Distribution. — The deposit to which the name White 
Sage formation is herein applied is found only in the 
northwestern part of the quadrangle. Most of the 
outcrops are on one or the other side of Deep Creek 
between benchmarks 5120 and 4984. The two most 
extensive are those east of benchmarks 5045 and 5062. 
Another area underlain by the formation is found 
about a mile north of peak 6266 ; and still farther east 
there are two additional areas, both of them, however, 
being west of the road between Gold Hill and Ferber. 

The name is taken from White Sage Flat, which is 
just west of the most southerly outcrop. 

Lithology— -The White Sage formation consists of a 
basal conglomerate of variable thickness overlain by 
fresh-water, rather impure limestones. The conglom- 
erate ranges in thickness from 1 foot to more than 50 
feet. The included pebbles are mostly less than 6 inches 
in diameter. They are derived from Pennsylvanian and 
Permian sediments and are considerably less altered 
in appearance than the bedded rocks of those forma- 
tions now in place. Sand lenses are abundant in the 
conglomerate. Most of the exposures weather to a 
deep red and contrast strongly with the lighter-colored 
rocks beneath them. In some places thin layers of 
similar conglomerate are interbedded with the over- 
lying limestone. 

The limestones are very fine grained rocks which are 
generally brownish on fresh fracture but weather to a 
dead white or chalk color. Individual beds are a foot 
or more in thickness, and a few are as much as 6 feet 
thick. All the beds examined contain a rather large 
amount of extremely fine clay and varying amounts of 
quartz. In some beds grains of quartz or chert 1 mil- 
limeter or more in diameter are scattered throughout. 



TERTIARY SYSTEM 



43 



A few beds contain thin brown-weathering chert string- 
ers, and some beds show a characteristic wavy or 
concentric banding on weathered surfaces, not unlike 
some banding that has been attributed to algal action. 

About a mile west of benchmark 4984 on Deep 
Creek, beyond the limits of the quadrangle, beds of 
limestone belonging to the White Sage formation show 
noteworthy discordances in dip among themselves and 
with the conglomerate of the formation. It is thought 
that these may be the result of earth movements that 
were active during the time the beds were deposited. 

Thickness. — The original thickness of the White Sage 
formation is not known, for it is everywhere uncon- 
formably overlain by lava or by recent gravel. The 
maximum thickness observed was in the isolated hill 
east of benchmark 5045 on Deep Creek, where about 
600 feet is present. 

Age and correlation. — Two collections of fossils were 
made from the White Sage formation. These were 
reported upon by J. B, Reeside, Jr., as follows: 

TN-27 125. About 4,000 feet east-southeast of benchmark 
5045, Deep Creek: I have been unable, by chemical or mechani- 
cal means, to get anything but cross sections of the abundant 
gastropods in this lot. The genus Physa is represented by 
species Yery similar in form to those known in the Eocene of the 
region; and a high-spired species that probably belongs in the 
genus Goniobasis is also abundant and might well belong to one 
of several Eocene forms. These alone would not be sufficient 
for an age assignment, but the widespread occurrence of an 
identical fresh-water limestone in the Wasatch and Green River 
formations of central Utah, coupled with the fossils, makes it 
highly probable that the present material is also Eocene. 

TN-27 124. About 2,500 feet southeast of benchmark 5097 
on Deep Creek: This lot is smaller than the first, but it appears 
to contain the same fauna, and the same remarks apply to it. 

Eocene beds have been found in western or central 
Utah in only a few places, almost all some distance to 
the south and southeast of Gold Hill. About 125 miles 
to the east-southeast are rather extensive exposures 
of limestone underlain by conglomerate, which are re- 
ferred to the Wasatch epoch of the Eocene by Richard- 
son •* and Loughlin. 94 These rest upon different Paleo- 
zoic and Mesozoic formations. A thick series of lime- 
stones with some conglomerate and sandstone beds in 
the Iron Springs district, 175 miles to the south, was 
mapped by Leith and Harder 95 as the Claron limestone, 
of Eocene age. It rests unconformably upon Creta- 
ceous rocks with little discordance of dip. The near- 
est area in which rocks of supposed Eocene age have 
been recognized is near the north end of the Pilot 
Range, 75 miles north of Gold Hill. Hague 96 has 
correlated these rocks with the Green River Eocene. 
These dip 45° E., but their relations to the underlying 
rocks are not described. 



»> Richardson, Q. B., Underground water in San Pete and central Sevier Valleys, 
Utah; U.S. Oeol. Survey Water-Supply Paper 199, p. 10, 1807. 

" LougWin, Q. F„ Ore deposits of Utah: U.S. Oeol. Survey Prof. Paper 111, 
pp. 326, 421, 1920. 

••Leith, C. K., and Harder, E. 0., The Iron ores of the Iron Springs district, 
southern Utah: U.S. Oeol. Survey Bull. 338, pp. 41-44, pi. 2, 1908. 

» Hague, Arnold, U.S. Oeol. Expl. 40th Par. Kept., vol. 2, p. 498, 1877. 



There is no trustworthy evidence to indicate which 
if any of these three areas of Eocene rocks is equivalent 
to the White Sage formation. 

UNCONFORMITY ABOVE "WHITE SAGE FORMATION 

The unconformity separating the White Sage for- 
mation from younger rocks, either volcanic rocks or 
gravel, is a pronounced stratigraphic break. The 
younger rocks are either horizontal or have low depo- 
sitional dips, in contrast to dips as high as 55° in the 
White Sage formation. The volcanic rocks are the 
next younger of the rocks found in contact with the 
Eocene (?) beds, and the surface of contact is approx- 
imately as rough as that of the present topography. 
The significance of the unconformity is touched upon 
in the consideration of the age of the intrusions and of 
the major structural features (pp. 63-64). 

OUDER IGNEOUS ROCKS (EOCENE OR OIJGOCENE) 
QENKSAL FEATURES 

About one-tenth of the quadrangle is underlain by 
a group of intrusive igneous rocks. By far the most 
extensive member of this group is a stock of quartz 
monzonite. Locally the stock has quartz dioritic or 
granitic facies, but these cannot be sharply differ- 
entiated from the quartz monzonite. 

Two groups of somewhat younger dike rocks, shown 
as porphyry dikes and aplites on plates 1 and 2, are 
associated with the stock. The porphyry dikes are 
generally dark gray and commonly contain con- 
spicuous phenocrysts in a dense groundmass, but there 
are some varieties that are only slightly porphyritic. 
They show an almost complete gradation in com- 
position from granite porphyries to basalts. The 
aplites are characterized by a pale-pink or white color, 
due to the almost complete absence of dark minerals, 
and an equigranular texture. Two varieties of aplites 
were recognized. 

QUABTZ MONZONITE 

Areal extent.- — The quartz monzonite crops out as a 
stock in the east-central part of the quadrangle. The 
main body extends about 8 miles from north to south 
and about 4% miles from west to east within the quad- 
rangle. Beyond the eastern border it is exposed at 
intervals for an additional 1% miles before disappearing 
beneath Lake Bonneville beds. The town of Gold 
Hill is near the northwest corner of this main body. 
Extending westward from the town and underlying 
most of the valley through which the Ferber Road 
passes is a wedge-shaped outcrop of the quartz mon- 
zonite about 3 miles long and about 1% miles wide at 
its junction with the main body. Projections of the 
sedimentary rocks into the stock are numerous. 
South of Clifton, on Montezuma Peak, two such 
projections nearly divide the quartz monzonite into 
two separate bodies, and the outcrop of quartz mon- 
zonite on the ridge at the summit is only 300 feet wide. 



44 



GOLD HILL MINING DISTKICT, UTAH 



There are also several areas of sediments, or "roof pend- 
ants", entirely enclosed within the quartz monzo- 
nite which further reduce its area of outcrop. Several 
small exposures of the intrusive that are without sur- 
face connection with the main body occur in the 
adjacent sedimentary rocks. The largest of these is 
at the head of Overland Canyon and has an area of 
about a quarter of a square mile. Smaller ones 
appear in Barney Keevey Gulch, in Hopkins Gulch 
below the Midas mine, and near the Ozark prospect. 
Many other smaller bodies have been mapped within 
the roof pendants or the projecting areas of sedimen- 
tary rocks. Outcrops of the quartz monzonite cover 
an aggregate area within the quadrangle of over 24 
square miles. 

In Dry and Sheep Canyons, in the Deep Creek 
Mountains, there are exposures of highly sheared and 
altered igneous rock that are probably to be correlated 
with the quartz monzonite. In both places the 
amount of such rock exposed is small. 

Petrographic and chemical character, — The unaltered 
quartz monzonite, though it all has the same general 
appearance, varies rather widely in both composition 
and texture from place to place. The greater part of 
the stock falls within the limits assigned to quartz 
monzonite by Lindgren, 87 but locally specimens are 
found that have the composition of granite, grano- 
diorite, or even quartz diorite. In a few places quartz 
is sufficiently scarce to permit the rock to be classified 
as a monzonite. Similarly, the bulk of the stock is 
nonporphyritic, but porphyritic facies are not uncom- 
mon. No sharp contact was found between any of 
these varieties, and the transition, whenever observed, 
was gradual in respect to either the proportion of the 
feldspars to each other or the number of phenocrysts 
present. 

The variety that is perhaps the most abundant and 
is also medial in character between various extremes 
may be considered typical .of the stock as a whole. 
This is a medium-grained rock, which assumes on 
weathered surfaces a purple-gray or brownish-gray 
color. Scattered through it are a few crystals of 
reddish orthoclase as much as 2 inches long. Smaller 
crystals of orthoclase are also present but are not as 
abundant as those of white plagioclase, which show 
fine twinning striae on. their cleavage faces. The 
crystals of the two feldspars are generally larger than 
those of the other constituents. Dark minerals make 
up about a quarter of the rock. Both hornblende and 
biotite are present, the former as greenish-black 
prisms with a good cleavage and the latter as small 
black hexagonal plates. Quartz is not readily apparent 
but on close examination may be recognized as small 
interstitial grains. 

Thin sections studied with the microscope show 
these minerals and in addition minor amounts of mag- 



's Lindgren, Waldemar, Granodlorite and other Intermediate rooks: Am. Jour. 
Sci., 4th ser., vol. A, p, 279, 1900. 



netite, titanite, apatite, and zircon. Plagioclase is the 
most abundant of the major constituents. In most 
specimens it is more or less strikingly zoned. The 
zoning is not progressive, although there is a general 
tendency for the more calcic zones to form the central 
portion of the crystal. The zones determined range 
in composition from a sodic oligoclase to a calcic 
labradorite. By far the bulk of the plagioclase is 
andesine, for the most part rather sodic. The potash 
feldspar is orthoclase and in most sections is perthitic. 
Quartz is interstitial to the other minerals. Horn- 
blende in most specimens of this variety of rock 
is more abundant than biotite. It is notably pleo- 
chroic, ranging from a pale yellow-green to green. 
The biotite is also pleochroic from yellow-brown or 
greenish brown to deep brownish black. Locally it 
replaces hornblende but in most places it has euhedral 
Outlines. Apatite is particularly abundant. The 
larger crystals show a faint purplish-gray pleochroism. 
The amount of titanite present is variable. Most of 
the crystals are irregular in outline and are associated 
with hornblende that has been altered to actinolite. 
It is probable that such titanite is secondary,. Much 
of the magnetite is also probably secondary, as it is 
largely localized in partly or wholly altered crystals of 
biotite and hornblende. In a few sections zircon 
crystals are included in biotite and are surrounded by , 
pleochroic haloes. 

The following chemical analysis, quoted from 
Butler, 98 represents a specimen of this variety of quartz 
monzonite obtained west of the Western Utah Copper 
Co.'s Gold Hill mine: 

Analysis of quartz monzonite west of Gold Hill mine of Western 
Utah Copper Co. 



IB. O. Weils, analyst] 



Si0 2 62.84 

Al 2 O s _ 14,21 

Pe 2 3 .91 

PeO 3.75 

MgO 3.04 

CaO 4.72 

Na 2 2.85 

K a O 4.60 

H 2 0- .26 

H 2 0+ 1.23 

The mineral composition calculated from the above 

analysis is as follows: 



Ti0 2 

ZrO 

COj 

P 2 O s 

s 

MnO 

BaO 



0.42 
Trace 
.38 
.41 
.01 
.06 
.03 

99. 72 



Quartz 17.46 

Orthoclase 23. 35 

Albite molecule 23. 06 

Anorthite molecule 8. 90 

Hornblende 19.21 



Biotite 5. 58 

Apatite 1. 01 

Calotte.. . 30 



98.87 



In the calculation the relative proportions of horn- 
blende and biotite were arbitrarily assumed, and an 
average of analyses of these minerals from similar 
rocks was assumed to represent their composition. 
After apportioning the oxides to the different minerals, 

•» Butler, B. S., Ore deposits of Utah: U.S. Qeol. Survey Prof. Paper HI, p. 98, 
1919. 



TEKTIABY SYSTEM 



45 



there remained a small excess of FeO and a rather 
large one of H 2 0+, which probably indicate that the 
specimen analyzed was partly sericitized. Specimens 
collected by the writer near the Gold Hill mine all 
showed this alteration more or less advanced. It is of 
some interest to note that both Fe 2 O s and Ti0 2 are 
completely used up in the calculation of hornblende 
and biotite, leaving none for magnetite and titanite. 
This is in accord with the observation that the mag- 
netite and titanite, as observed in the sections, are 
more or less restricted to large crystals of hornblende 
and biotite and in some places at least have been 
formed at their expense. 

An examination of specimens taken from the wedge- 
shaped area of the intrusive south of Dutch Mountain 
indicates that they are close to the dividing line 
between granite and quartz monzonite. Biotite is 
more abundant than hornblende, and the plagioclase 
is slightly more sodic and is apparently a calcic oligo- 
clase, although rather thorough sericitization in the 
slides examined prevented accurate measurement. 
There are no other differences from the more common 
variety. 

At the other extreme is a specimen taken from the 
nyiin body of the intrusive near the east border of the 
quadrangle, in which the content of orthoclase has 
decreased to 10 or 15 percent. This rock is without 
the large phenocrysts of orthoclase and has a larger 
proportion of darker minerals. The ratio of the 
feldspars places the rock in the group of granodiorites. 
A similar rock is found as a dike cutting the Ochre 
Mountain limestone a few hundred feet north of the 
Overland Eoad half a mile southeast of the junction 
of roads from Ibapah and Gold Hill. The quartz 
content of this rock is rather less than normal but is 
large enough for the rock to be classed as a granodiorite. 

The quartz monzonite is porphyritic in places, 
particularly at its contacts, with phenocrysts of both 
orthoclase and plagioclase. In this variety there are 
all gradations in size between the phenocrysts and the 
crystals of the same minerals in the groundmass. 
The smaller grains are of about the same size as that 
in the nonporphyritic rock. Such a fades may be 
classed as porphyritic quartz monzonite. 

The porphyritic habit is particularly pronounced in * 
the exposures of the intrusive south and southwest of 
Dutch Mountain and west of Gold Hill. Thin sections 
of specimens from this region show that there is 
apparently a gradation between the porphyritic quartz 
monzonite and rock that is more properly termed 
quartz monzonite porphyry. In the latter variety 
the phenocrysts of quartz, feldspars, and the dark 
minerals may be several millimeters long, but the 
crystals in the groundmass are only a fraction of a 
millimeter in diameter and are for the most part of 
quartz and feldspar, chiefly orthoclase. In texture 
and composition these rocks are not unlike some of 



the lighter-colored porphyry dikes that cut the main 
mass of the intrusive to the east. 

Darker nodules or basic segregations are found scat- 
tered throughout the normal quartz monzonite. 
They range from an inch to a foot in diameter and may 
be much more abundant in one place than another. 
The nodules are characterized by a concentration of 
hornblende, a diminution of feldspars, and an absence 
of quartz and biotite. A thin section of one of them 
shows a large amount of euhedral magnetite, some 
titanite, apatite, and much green hornblende, similar 
to that of the quartz monzonites. Andesine and 
orthoclase are present in about equal amounts and 
are later than the hornblende, which is frayed and 
embayed by them. 

Another kind of inclusion, usually of dark color, 
which is found near the contacts of the quartz monzo- 
nite, is metamorphosed sedimentary rock. These are 
fine-grained to dense and are commonly less than 2 or 3 
inches in maximum diameter. They are not so uni- 
form in texture and appearance as the basic segrega- 
tions and furthermore show a border of different color 
and texture at the contact with the normal quartz 
monzonite. Thin sections show a mineral composition 
quite unlike that of the segregations, and different 
specimens differ from one another. One specimen 
obtained near Gold Hill, for example, showed a fine- 
grained aggregate of quartz, plagioclase, biotite, mag- 
netite, and a green isotropic mineral that is probably 
pleonaste, the magnesia-iron spinel. The inclusion is 
separated from the normal igneous rock by a border of 
sericite. The restriction of such inclusions to the 
contact, their mineral composition, and the presence 
of borders or "reaction rims" of different composition 
indicate that they are highly altered fragments from 
the Oquirrh formation that have been engulfed in the 
igneous rock during its intrusion. 

Factors influencing the localization of the quartz 
monzonite. — Preexistent faults appear to have played 
an important part in determining the location of the 
quartz monzonite stock. The influence in a minor 
way of such older faults is extremely well shown in 
several places on the south side of Montezuma Peak, 
where the quartz monzonite contact follows faults that 
must have existed prior to the intrusion. In these 
places the quartz monzonite apparently utilized the 
old fracture lines as a means of ingress but caused no 
additional deformation. 

A more definite relation between old faults and the 
intrusion is suggested by the essentially complete 
restriction of the intrusion between two large trans- 
verse faults, the Blood Canyon fault on the south and 
the Pool Canyon fault on the north. These two faults 
are thought to limit also an extensive thrust fault. 
In view of the dependence of the intrusion upon 
preexistent faults noted in the preceding paragraph, it 
seems probable that there may be a similar relation 



46 



GOLD HILL MINING DISTRICT, UTAH 



between these major faults and the intrusive body. 
The thrust fault limited bj the transverse faults must 
have caused a high degree of fracturing in the affected 
rocks, and this in turn provided the necessary lines of 
weakness that were apparently required for the em- 
placement of the stock. 

This suggestion implies that the intrusion came into 
place without causing any great deformation of the 
invaded rocks, and the implication is confirmed by 
the absence of any discernible doming in the sedimen- 
tary rocks bordering the stock. The only evidence 
that there were any pronounced ^arth movements 
during the intrusion of the quartz monzonite is found 
along the western border of the main mass of the 
intrusive, where there are several faults of large throw. 
For several reasons (see p. 89) these faults are con- 
sidered to have been caused by the intrusion and to 
mark the location of the primary channel through 
which the quartz monzonite was intruded. 

POEPHYEY DIKES 

Distribution and size. — Porphyry dikes are rather 
widely distributed throughout the quartz monzonite 
area and also over much of Dutch Mountain. They 
are most abundant in the region about 2 miles east of 
Clifton, where an area of nearly a square mile is more 
than half underlain by porphyries. 

The ratio between the length and breadth of the 
dikes is rather variable. The quartz monzonite por- 
phyry dike cutting through the claims of the Western 
Utah Copper Co. at Gold Hill, for example, may be 
traced for nearly 2 miles and for the greater part of 
this distance is less than 20 feet wide. Some other 
dikes that were 10 feet or less in width were followed 
for distances close to half a mile. On the other hand, 
several of the dikes in the locality east of Clifton are 
250 feet or more wide and are less than half a mile 
long. A similar rather thick lens occurs on the north 
side of Dutch Mountain half a mile south of the Gar- 
rison Monster mine, and another just north of the town 
of Gold Hill. In several places dikes less than a foot 
wide could not be traced beyond the rock outcrop in 
which they were found. 

Appearance. — As these dikes have a considerable 
range in composition, it is not surprising that there 
is a corresponding variation in their appearance. Two 
general varieties may be distinguished. One is a highly 
porphyritic rock, whose prevailing color is a greenish 
or pinkish gray, or even white in places where altera- 
tion has been especially intense. The phenocrysts con- 
sist chiefly of rounded quartz crystals and dull feld- 
spars, with locally some of ferromagnesian minerals, 
particularly biotite. The groundmass is invariably too 
fine-grained for any of its constituent minerals to be 
recognized. 

The other variety has characteristically a dark 
greenish-gray color, that contrasts strongly with the 
lighter color of the quartz monzonite. Its pheno- 



crysts are commonly neither abundant nor conspicuous 
and are for the most part of the ferromagnesian min- 
erals, but in several specimens they are similar in 
numbers and in character to those in the lighter- 
colored rocks. Locally also, particularly east of Clif- 
ton, scattered phenocrysts as much as an inch in length 
may be found. In some of the rocks rounded quartz 
phenocrysts about an eighth of an inch in diameter 
are present in small quantities and are conspicuous 
because of the dark color of the rest of the rock. The 
matrix in this variety also is much too fine-grained to 
be determinable megascopically. 

Only one equigranular dike was noted during the 
field work. This was the thick dike south of the Gar- 
rison Monster mine. It has a pepper-and-salt appear- 
ance due to the presence in nearly equal quantities 
of dark-greenish hornblende and other dark minerals 
and white feldspathic minerals. Some of the horn- 
blende is in the form of needles or poorly defined platy 
aggregates nearly a quarter of an inch long, but they 
are not sufficiently distinct to give the rock a porphy- 
ritic aspect. 

Microscopic features. — Two varieties of the por- 
phyry dikes may be distinguished on the basis of their 
composition and texture as disclosed by microscopic 
examination. These two varieties correspond roughly 
with the two megascopic divisions, in that the lighter- 
colored dikes contain a higher proportion of quartz 
and feldspars and their groundmass has an allotrio- 
morphic texture, whereas the darker dikes contain a 
higher proportion of dark minerals and their ground- 
mass includes laths of plagioclase, whose relations to 
the other minerals in the groundmass are character- 
istic of what has been named an "intergranular" tex- 
ture. Several specimens, however, appear to bridge 
the gap between the two extremes of composition and 
texture, and the distinction between them is chieffy 
valuable for purposes of description. 

The dikes characterized by predominance of the 
light-colored minerals and allotriomorphic texture of 
the groundmass contain phenocrysts of quartz, ortho- 
clase, plagioclase, biotite, and rarely hornblende, in a 
groundmass of the same minerals. The quartz phe- 
nocrysts are strikingly corroded and embayed by the 
* groundmass. In many places the tabular feldspars 
are too altered for satisfactory determination, even 
where those in the surrounding quartz monzonite are 
relatively fresh. Where they can be identified, how- 
ever, it is generally possible to prove that both ortho- 
clase and plagioclase are present; the composition of 
the plagioclase ranges in different dikes from albite to 
andesine. Biotite in small quantities is a common 
constituent and occurs as hexagonal prisms that are 
about a sixteenth of an inch across, from a half to a 
quarter of the diameter of the phenocrysts of quartz 
and feldspar. Hornblende is an uncommon pheno- 
cryst in the more siliceous rocks. The groundmass is 
composed of a very fine grained aggregate of quartz, 



TBETIABY SYSTBM 



47 



feldspar, and, locally, shreds of biotite, although in 
many specimens it is so thoroughly altered that the 
original composition is uncertain. The minerals in the 
groundmass, unlike the phenocrysts, do not show crys- 
tal outlines, and the resultant xenomorphie texture is 
markedly different from that shown by the groundmass 
of many of the darker dike rocks. 

In this variety the proportions of quartz and the 
two kinds of feldspars vary greatly in different dikes. 
The dike that forms the footwall of the Cyclone vein, 
for example, is a granite porphyry. On the other 
hand, a dike in Tribune Guleh, on the southeast side 
of Dutch Mountain, is close to a diorite porphyry. 
Between these two extremes are dikes that contain 
more or less quartz and both orthoclase and plagioelase 
and are classified as quartz monzonite porphyries, of 
which the prominent dike that cuts through Gold Hill 
is an example. 

The porphyry dikes of the second variety contain 
phenocrysts of augite, hornblende, biotite, plagioelase, 
and quartz. Augite is abundant in a few of the dikes 
but in several is partly altered to green hornblende. 
The hornblende, generally accompanied by biotite, 
also occurs in some of the dikes that contain no augite. 
The phenocrysts of these dark minerals are generally 
from a sixteenth to an eighth of an inch in diameter, 
but in a few places phenocrysts of augite as much as 
an inch in length have been noted. The plagioelase 
phenocrysts may be as much as half an inch in diameter 
but are generally a quarter of an inch or less and have 
a composition ranging from sodic andesine to sodic 
labradorite. Corroded and embayed quartz pheno- 
crysts are found sparingly in almost all the dikes. The 
most abundant mineral in the groundmass is micro- 
scopic plagioelase, which, where determinable, is some- 
what more sodic than that of the phenocrysts. It has 
a striking tabular habit. The laths, however, do not 
show r a uniform orientation but are haphazard or, 
locally, in the form of rosettes. Between the laths are 
tiny grains of augite (in dikes that contain augite 
phenocrysts), hornblende, biotite, and locally quartz 
and orthoclase. This texture is similar to that called 
intergranular in basalts and andesites, and many of 
these dikes may be accurately termed augite or horn- 
blende andesite or basalt. 

There is a considerable variation in composition in 
the rocks of this variety, as in the lighter-colored dikes. 
All the dikes in this group, however, show the inter- 
granular texture of the groundmass. Some of them 
contain sufficient quartz to be called daeites, and others 
are clearly basaltic. 

Several dikes were found that have in part the 
characteristics of the first variety and in part those of 
the second variety. These rocks commonly contain 
phenocrysts of quartz, orthoclase, plagioelase (oligo- 
clase or andesine), and locally biotite, but phenocrysts 
of hornblende or augite are either scarce or completely 



absent, the rocks thus resembling the more siliceous, 
light-colored dikes. The groundmass of such rocks is 
largely made up of laths of plagioelase, and the inter- 
granular texture thus formed is similar to that of the 
darker-colored dikes. A dike of this class that crops 
out just east of the old Garrison Monster camp has a 
groundmass in part xenomorphie and in part composed 
of radiating laths of plagioelase, similar in appearance 
to those found in rocks whose groundmass is wholly 
intergranular. 

Several of the porphyry dike rocks show a local 
development of granophyric texture in the groundmass. 
This microscopic intergrowth of quartz and feldspar 
was found chiefly in the lighter-colored siliceous dikes, 
but it is also present in the nearly equigranular thick 
dike south of the Garrison Monster mine. Its signifi- 
cance in these dikes is not understood, but the condi- 
tions favoring its development were evidently nearly 
independent of the composition of the dike. 

All the dikes are more or less altered, and almost 
invariably the degree of alteration in the dikes intru- 
sive into the stock is greater than that of the surround- 
ing quartz monzonite. Sericite, calcite, chlorite, and 
quartz are the chief secondary minerals, as they are in 
most of the altered quartz monzonite. 

Relations to other rocks. — The porphyry dikes intrude 
both the quartz monzonite and the sedimentary rocks 
and are in many places localized along minor faults. 
At least two of the dikes in the quartz monzonite 
differ from those in the sediments in that they are 
discontinuous. One of these dikes is on the east side 
of the northward-draining gulch east of the summit of 
Gold Hill, and the other is about a quarter of a mile 
east of the Success mine. The exposures of the second 
dike show clearly that the discontinuity is not the 
result of later faulting but is an original feature. 
Preexistent joint planes or fractures in the quartz 
monzonite appear to have played an important part in 
the determination of the course of the dike, and where 
they were not sufficiently well developed, the dike did 
not enter. 

In several places on the southeast side of Dutch 
Mountain aplite dikes are in contact with the porphyry 
dikes, and in all such occurrences the aplites are found 
to be younger. Quartz-sulphide veins are also younger 
than the dikes, as is shown by the developments at 
the Cyclone mine and elsewhere. In the locality east 
of Clifton the dikes are cut by several carbonate veins, 
which are thought to represent the latest of the series 
of events initiated by the intrusion of the quartz 
monzonite. 

Relations of the porphyry dikes to one another,- — In 
a few places different varieties of the porphyry dikes 
are in contact with each other, by reason of the forma- 
tion of compound dikes. Examples of such dikes are 
found about 2,000 feet west of the Western Utah mine 
and also in the area of dike concentration east of 



48 



GOLD HILL MINING DISTRICT, UTAH 



Clifton. At both localities the lighter-colored, more 
siliceous dikes are younger than the darker ones. On 
the eastern slope of hill 5675, near the mouth of 
Rodenhouse Wash, however, a light-colored quartz 
monzonite porphyry is clearly cut by a more basic 
dike, which strikes nearly at right angles to it. It 
appears, therefore, that although the lighter-colored 
dikes are in general younger, there are local exceptions 
to the rule. 

APUTE DIKES 

Distribution and character. — Two varieties of aplite 
dikes may be distinguished. One of these is a pale- 
pinkish to white rock that occurs as small lenticular 
or cylindrical masses in the quartz monzonite. Its 
boundaries with the main intrusive are gradational, 
there being a zone between the two in which a coarsen- 
ing of the grain and an increase in dark minerals from 
the aplite to the quartz monzonite may be discerned. 
Almost all the occurrences of aplite of this kind may 
be measured in inches or feet; a few extend for 10 feet 
or so; and exceptionally some of the cylindrical masses 
may have a diameter of 30 or 40 feet. This variety 
of aplite is widely distributed throughout the main 
outcrop of the quartz monzonite stock, but because 
of the small size of the individual bodies they are not 
shown on the geologic map. 

The second variety of aplite is limited to the quartz 
monzonite area on the southeast side of Dutch Moun- 
tain north and northwest of the town of Gold Hill. 
These dikes are shown on the geologic map, They 
are light-colored rocks that are generally more resis- 
tant to erosion than the surrounding rocks and can be 
readily traced by reason of their color and superior 
relief. Most of the exposures are relatively narrow 
dikes that are only exceptionally wider than 20 feet 
and are generally only 10 feet or less. Several of them 
have been traced for at least 2,000 feet. A few of the 
outcrops, notably one about three-quarters of a mile 
northwest of the town of Gold Hill, have a bulbous 
outline, from which thin dikes extend for some distance. 

Quartz and feldspar make up almost all of this 
variety of aplite, and many of the feldspar crystals 
have a tabular habit. Crystals of biotite can be dis- 
tinguished in several of the dikes but are absent in 
others. Tiny irregular splotches of blue tourmaline 
are also present in some specimens. 

Microscopic features. — The minerals found in the 
first variety of aplite are quartz, calcic oligoclase, 
perthitic orthoclase, rare biotite, and the accessories 
apatite, titanite, zircon, and iron ores. They do not 
differ in any respect from the same minerals found in 
the quartz monzonite — in fact, the only differences 
from the main intrusive shown by this variety of aplite 
are the slightly smaller grain size and the nearly com- 
plete absence of the dark minerals. 

The second variety of aplite is much finer grained 
than the first, individual crystals having an average 



diameter of 1 to 2 millimeters. Nearly equal quan- 
tities of quartz, perthitic orthoclase, and calcic oligo- 
clase make up almost the entire rock. Zircon is pres- 
ent as an accessory mineral, but apatite, titanite, and 
iron ores are almost completely absent. In some speci- 
mens biotite is present in smal crystals. The texture 
of the rock is panidiomorphic in that many of the 
feldspar grains are euhedral, with quartz filling the 
interstices. Where tourmaline is present it replaces 
the other constituents in irregular splotches. Its ple- 
ochroism in thin section is « = deep greenish blue, 
* = pale yellow-green. 

Relations to other rocks. — The aplite dikes were not 
recognized as cutting sedimentary rocks and are appar- 
ently restricted to the quartz monzonite. Those of the 
second variety are clearly younger than the porphyry 
dikes exposed in that area, and the aplites of the first 
variety have been noted in the wall rocks of some of 
the quartz sulphide veins. If the two varieties are of 
the same age, the combined evidence would make 
them later than the period of porphyry dike intrusion 
and earlier than much of the ore deposition. The 
difference in habit and occurrence of the two varieties, 
however, makes any assumption of contemporaneity 
between them rather doubtful. 

AGE OF TIE OtDIR TOHEOTO ROCKS 

Although the White Sage formation, of Eocene (?) 
age, is not itself intruded by either the quartz mon- 
zonite or the dike rocks within the quadrangle, it is 
locally metamorphosed and is therefore believed to be 
older than the intrusive. This conclusion is checked 
by the structural history of the quadrangle. (See 
p. 64.) On the other hand, volcanic rocks thought 
to be of late Pliocene age overlie the quartz monzonite 
unconformably. The emplacement of the stock must 
therefore have occurred at some time between these 
two epochs. As a long period of erosion must have 
been required to expose the quartz monzonite before 
the volcanic rocks could be deposited upon it, it would 
appear that the intrusion probably took place between 
the late Eocene and early Oligocene. 

In other parts of Utah similar igneous rocks have 
been reported to be either of late Cretaceous or early 
Eocene age M or of late Eocene or post-Eocene age. 1 
The Gold Hill intrusion must be of the latter age. 

PLIOCENE (?) SEDIMENTS 

About a mile west-southwest of Ibapah, on the west 
edge of the quadrangle, a small area is covered by a 
series of marl, sandstone, and gravel. These materials 
are exposed much more extensively to the west. 

The beds have a white or light brownish-gray color 
that contrasts with the darker color of the younger 

» Oilluly, James, Basin Range faulting along the Oqutah Range, Utah: Geol. 
Soe. America Bull., vol. 39, pp. 1117-1118, 1928. 

i Loughlin, Q. r., Geology and ore deposits of the Tintio minim district, Utah: 
U.S. Geol, Survey Pro!. Paper 107, p. 104, 1919. 



TERTIARY SYSTEM 



49 



gravel nearby. The most common rock is a coarse 
grit or sandstone, fairly well cemented by calcium 
carbonate. Locally these pass into beds containing 
pebbles that must have come from the west or south, 
as shown by bedrock exposures in those directions. 
The grits are composed chiefly of quartz grains, but 
there are also numerous flakes of biotite. Some of 
the grits are perceptibly cross-bedded. 

A few beds of marl are included. These are 2 or 3 
feet thick and are more resistant to weathering than 
the other members of the series. They are filled with 
casts of tiny tubes, which may represent plant rootlets 
or stems. A few grains of quartz 1 or 2 millimeters in 
maximum diameter can usually be found within the 
marl. 

About 100 feet of these beds is exposed within the 
quadrangle, but the total thickness exposed to the 
west is much larger. 

No diagnostic fossils were found in these rocks. A 
few fragments of bones were found and submitted to 
Dr. J. W. Gidley, of the United States National 
Museum, but the material was too poor to be iden- 
tified even generically. The beds are essentially flat- 
lying but are well dissected and overlain in some 
places by gravel containing pebbles of volcanic rocks. 
They are therefore thought to be of prevolcanic age, 
and, as they are not disturbed, of post-Eocene age. 
It is thought that they were deposited shortly before 
the volcanic rocks were erupted, and because of this 
belief they have been assigned tentatively to the 
Pliocene. 

YOUNGER IGNBOTJS ROCKS fl^ATB PXXOCENB?) 

At several places in the quadrangle there are small 
areas covered by igneous rocks whose relations make 
them easily recognized as being much younger than 
the Gold Hill stock and its associated dikes. The 
greater number of these outcrops are either lavas or 
pyroclastic rocks but in several places small intrusive 
bodies were found. The composition ranges from 
rhyolite to basalt, with rocks of intermediate composi- 
tion and rich in potassium greatly predominating. 

Because of the small size of most of the outcrops of 
these rocks, and because of the impossibility of estab- 
lishing the correct chronologic sequence between such 
isolated occurrences, the whole group is shown on the 
map under the same symbol. 

DISTRIBUTION AND 1I1ATIONS 

The bulk of the volcanic rocks are found in the 
northwestern part of the quadrangle, particularly on 
both sides of Deep Creek. In the canyon of Deep 
Creek itself from benchmark 5045 south there are five 
small necks, and to the east and west flows and pyro- 
clastic rocks occur. The largest area covered by the 
volcanic rocks within the quadrangle is that about 2 
miles east of Deep Creek on the western and southern 



slopes of peak 6147. There are also some fair-sized 
exposures in the area of low relief between the Ferber 
Road and the wagon road between the Erickson ranch 
and Gold Hill. These are chiefly lavas but include 
some tuffaceous rocks. 

These volcanic rocks were erupted before the cut- 
ting of the present Deep Creek Valley, as is shown by 
the lack of outcrops other than necks in the flat- 
bottomed portion of the valley, and by the restriction 
of the flows to mature valleys in the higher land on 
each side. The recent cutting of the lateral gulches 
east and west of benchmark 5062 on Deep Creek has 
exhibited small hanging valleys filled by the lavas. 
The pyroclastic rocks appear to have been erupted 
first, for they are overlain by lavas or cut by necks 
wherever observed. Erosion was active during the 
extrusion of the lavas in this region, for a widespread 
flow of hypersthene-augite latite rests uneonformably 
upon the other lavas and locally lies directly upon the 
filling of the necks through which these older flows 
were erupted. 

Small exposures are found at a number of places in 
the south-central and southeastern parts of the area. 
There are several patches on the Lincoln Highway 
south of Gold Hill and similar occurrences on the 
northern and northeastern parts of Clifton Hat. 
These are chiefly lavas. In Eodenhouse Wash about 
1)1 miles north of Clifton a small area is covered by 
both lavas and pyroclastic rocks. An exposure of 
moderate size was found in Blood Canyon, and smaller 
residual patches are present here and there along the 
lower part of Overland Canyon and among the Lake 
Bonneville deposits through which the stream has cut. 

The volcanic rocks in these more easterly localities 
commonly occur in valleys cut in the quartz monzonite 
or m the sedimentary rocks intruded by it. Their 
eruption appears to have been more or less contem- 
poraneous with the deposition of the gravel that fills 
some of the valleys in this region. At the mouth of 
North Pass Canyon, for example, a dike of alkali 
basalt is exposed within the gravel and is thought to 
be younger, for otherwise it would be necessary to 
believe that the dike must have stood as a narrow wall 
over 20 feet high while coarse gravel was being de- 
posited around it — a view that is difficult to accept, 
because the dike is much less resistant to weathering 
than the Pennsylvanian rocks that would have origi- 
nally formed its walls. Some of the outcrops of lava 
in Blood Canyon also appear to be younger than the 
gravel. On the other hand, many of the exposures of 
volcanic rocks in this region are overlain by gravel, 
which is now being eroded. 

P1TEOOEAPHY 

The younger volcanic rocks have a considerable 
diversity in composition, the silica in the five specimens 
analyzed ranging from 47.36 to 70.30 percent. Rocks 



50 



GOLD HILL MINING DISTRICT, UTAH 



containing about 60 percent of silica are by far the most 
abundant. In the field, and even in the microscopic 
study of the lavas, the rocks appear to represent a nor- 
mal series of basalts, andesites, and rhyolites. The 
chemical analyses, however, show that they are all rich 
in potassium and that the series includes alkali basalts, 
latites, trachytes, and rhyolites. 

The abundance of such potassium-rich volcanic rocks 
in Utah and New Mexico has been noted and com- 
mented upon by Butler 2 and by Lindgren, Graton, 
and Gordon. 3 

Biotite and hornblende andesites or latites.— -By far 
the most abundant volcanic rocks in the quadrangle 
are biotite and hornblende andesites or latites. Most 
of the flows and necks found on both sides of Deep 
Creek are of this composition, as are those in Blood 
Canyon and in Clifton Flat. These are all porphyritic 
rocks that commonly weather to shades of brownish 
gray but are greenish to purplish gray on fresh fracture. 

Plagioclase, biotite, hornblende, and augite are the 
only abundant phenocrysts and are embedded in a 
groundmass that may be almost entirely glassy in 
many of the flows or nearly holocrystalline in some 
specimens from the necks. All the rocks show some 
alteration, but this is most marked in the necks, which 
are in places so affected that only traces of the original 
minerals remain. 

The zoned plagioclase phenocrysts range in com- 
position from sodic andesines to calcic labradorite. 
The more calcic varieties particularly contain numer- 
ous glass inclusions. In most of the specimens either 
hornblende or biotite is the dominant dark mineral, 
but in one specimen from Blood Canyon the two are 
present in nearly equal amounts. They are commonly 
bordered by thick rims of magnetite. Both green and 
brown hornblende were recognized, but the former 
appears to be limited to varieties in which biotite is 
abundant. Sparse phenocrysts of augite are present 
in both the hiotite-rich and hornblende-rich lavas and 
sporadic crystals of quartz are even less common. 
Apatite and, in one specimen, titanite are accessories. 

The groundmass of these rocks is commonly com- 
posed of glass in which are embedded tiny laths of 
plagioclase and dots of magnetite. The plagioclase 
laths appear to be somewhat less calcic than the 
phenocrysts, most of those determined being sodic to 
medium andesines, Trichites and globulites were 
found in the glass in some specimens, and perlitic 
cracks are also present. Both the color of the glass 
and its index of refraction are different in different 
rocks, the index ranging from less than 1.50 to slightly 
less than that of balsam. In many specimens, partic- 
ularly those from the necks, the glass has been devit- 
rified, and poorly defined areas of quartz and feldspar 
replace it. In several of the glassy flows oriented 

» Butler, B. S., Ore deposits of Utah: U.S. Geo]. Survey Prof. Paper 111, p, 89, 1920. 
' Lindgren, Waldemar, Graton, L. C, and Gordon, C. H., Ore deposits of New- 
Mexico; U.S. Geol. Survey Prof. Paper 68, pp. 4S-44, 1910. 



plagioclase laths are distributed in wavy bands that 
are locally interrupted by and in part flow around 
nodules containing much glass. 

An analysis of a specimen of this group of lavas 
collected west of benchmark 5030 on Deep Creek gave 
the following result: 

Analysis of Motite-augite lalite 
[ 1. G. Fairehild, analyst] 



SiOs 


57.94 


KjO— - 


8.90 


A1 2 3 


16.66 


Ti0 2 —- 


1.00 


Fe 2 3 


2. 73 


P 2 5 


.- -. - . 11 


FeO 


.57 


H.O+ 


. ., 1, 66 


MgO 


.60 


H 2 0- 


3.82 


CaO 


4.91 




. 


Na 2 . 


1.29 




100. 19 



I(II)."6.2."2, vulsinose. 

The high content of K 2 was totally unexpected, for 
the microscopic examination had indicated no potash- 
bearing mineral except a relatively minor amount of 
biotite. A comparison of the norm of the rock with 
the mode makes it evident that the glassy groundmass 
must consist almost entirely of potash feldspar with a 
small amount of quartz. The propriety of terming 
this rock a latite may perhaps be questioned, but the 
relatively low silica and alumina and relatively high 
lime made it seem preferable to use this name rather 
than trachyte, in spite of the preponderance of potash 
over soda. The rock is somewhat similar in chemical 
composition to a trachyte from the Iron Springs district 
described by Leith and Harder 4 but is higher in lime 
and lower in silica. 

No other analyses were made of members of this 
group of rocks, and their reference to "andesites or 
latites" reflects the uncertainty as to their true nature 
that results from the lack of additional analyses. 

Hypersthene-augite latite. — Rocks of the composition 
of hypersthene-augite latite are exposed in many 
localities in the northwestern part of the area from the 
western slopes of Dutch Mountain to the western 
border of the quadrangle. All these exposures appear 
to be a part of the same flow or of closely related flows, 
as they all have the same relations to the other volcanic 
rocks. Only one vent through which these rocks 
could have reached the surface was found. This is 
a small elliptical neck about 2,500 feet north-northwest 
of benchmark 5062 on Deep Creek. 

In hand specimens the rock is dark gray to grayish 
black. Phenocrysts of yellowish or white plagioclase 
and greenish-black pyroxene are abundant and make 
up one- third to one-half of the rock. The groundmass 
is dense black and in some places has a conchoidal 
fracture. Locally there are tiny vesicles, which may 
be filled with a chloritic mineral, but these are not 
abundant. 

Thin sections show that the abundant plagioclase 
phenocrysts have an average composition of Ab^Amse- 

* Leith, C. K., and Harder, E, C, The iron ores of the Iron Springs district^ 
southern Utah: U.S. Qeol. Survey Bull. 338, p. 68, 1908. 



TEBTIABY SYSTEM 



51 



They commonly show an oscillatory zoning, however, 
and portions may. be as sodic as Ab 60 An 40 or as calcic 
as Ab 2s An 75 . Glass inclusions are present locally, 
Hypersthene and augite phenocrysts are found in 
about equal amount. The hypersthene is pleochroie 
in shades of light reddish brown and greenish gray. 
Sparse phenocrysts *of brown hornblende were recog- 
nized in a few specimens. Magnetite and apatite are 
accessory minerals. In several of the specimens the 
groundmass is composed entirely of brown glass, 
which locally showed perlitic cracks, trichites, and 
globulites. Other specimens show numerous labrado- 
rite laths in the groundmass and, with increasing 
crystallinity, small pyroxene crystals. In the latter 
specimens the texture is typically byalopilitic. 

A specimen of this rock taken a quarter of a mile 
west of benchmark 5045 on Deep Creek was analyzed 
with the following results: 

Analysis of hypersthene-augile latite 
[J. O. Fairehild, analyst] 



S1O2 61.52 

AljOj 15. 25 



FejOj- 
FeO-. 

MgO. 
CaO._ 
NasO. 



2. 20 

3. 97 
2.59 
5.72 
2. 31 



K a O 3.02 

Ti0 2 1.00 

P 2 O a .16 

H 2 0-h 2.23 

H 3 0- .36 

100. 33 



"II.4.3.3, liarzose. 

The analysis shows that the rock falls into the latite 
group. It is rather similar to a latite from the Tintic 
district described by Loughlin, 5 which also is hyper- 
sthene-bearing. In the Rosenbusch classification a 
volcanic rock of this composition would be termed a 
trachyandesite. A rock of this name from Col d'Orec- 
cia, Corsica, is chemically similar. 9 

The norm was calculated from the analysis and 
compared with a mode roughly estimated by the 
Rosiwal method. The result indicated that the glassy 
base, if it were crystalline, would be composed of 
about 2 parts of quartz, 2 of orthoelase, and 1 of sodic 
andesine. 

Trachyte. — Just east of the small knob in the gulch 
east of benchmark 5120 on Deep Creek there is a 
small area of rock which is notably different in appear- 
ance from the latite lavas. This is a light-pink rock, 
locally splotched by pale-green areas. Small laths of 
feldspar are scattered through the rock, and there are 
a very few crystals of black hornblende. A thin section 
shows that about a third of the rock is composed of 
phenocrysts, chiefly albite-oligoclase, with much less 
abundant sanidine. Green hornblende and augite are 
of minor importance. Apatite needles, magnetite, and 
zircon were identified as accessory minerals. The 

' Loughlin, O. F., Geology and ore deposits of the Tintie mining district, Utah: 
U.S. Oeol. Surrey -Prof. Paper 107, p. 62, 1919. 

» Eosenbuseh, Hany, Elemente der Gesteinslehre,- 4th ed., by A. Osann, p. 416, 
Stuttgart, 1923. 



remaining two-thirds of the rock was originally of 
glass, but much of it, together with almost all of the 
augite crystals, has been replaced by calcite. In a 
few places there are areas of a colorless, almost iso- 
tropic chloritic mineral fringed with calcite. A partial 
analysis of this rock gave the following result: 

Partial analysis of trachyte 



[J. G. Fairehild, analyst] 



SiOj 65.00 

A1A 14.28 



Na 2 0^ 
K 2 0__ 



2.23 
5. 19 



The rock is over 4 percent higher in silica than the 
average trachyte listed by Daly 7 and lower in alumina 
and soda. It is even more discordant with the average 
rhyolite, however, and the fact that no quartz was 
recognized in the thin section, while sanidine, which 
as a rule crystallizes later than quartz, is present, 
makes the assignment to the trachyte group fairly 
certain. 

Rhyolites. — Two occurrences of rhyolite were found, 
one about a mile southwest of benchmark 5045 on 
Deep Creek and the other in the northern part of 
Rodenhouse Wash. The Deep Creek exposure is part 
of an old neck, and to the south there are lavas that 
are related to it. The rock is greenish gray and con- 
tains a few phenocrysts of biotite and a sodic andesine 
that is almost completely altered to thompsonite. 
Small laths of plagioclase are enclosed in a glassy 
matrix, which has an index of refraction slightly less 
than 1.50 where unaltered. In most places the glass 
has been devitrified and consists of quartz, oligoclase, 
and orthoclase. A partial analysis shows clearly that 
this rock is most closely related to rhyolite: 

Partial analysis of rhyolite 
[J. G. Fairehild, analyst] 



Si0 2 70.30 

A1 2 3 14.92 



NajO 2. 66 

K 2 4.37 



The Swansea rhyolite of the Tintic district 8 has a 
similar chemical composition but is quite different in 
mineralogic habit, being an intrusive rock. 

The rhyolite in Rodenhouse Wash is very different 
in appearance and texture from the rock described 
above. It is a poorly banded fine-grained purple rock 
that originally consisted of sparse plagioclase pheno- 
crysts in a spherulitic matrix. It has undergone a 
rather complete recrystallization, however, and the 
phenocrysts are now composed of a finely crystalline 
aggregate that is probably oligoclase, in a matrix 
consisting of irregular and poorly defined areas of 
quartz and oligoclase. The boundaries of these two 
minerals show no relation to the outlines of the old 
spherulites. Megascopic crystals of a red garnet and 
microscopic laths of tourmaline are also present. 

' Daly, B. A., Igneous rocks and their origin, p. 21, New York, 1914. 
> Loughlin, O. F„ Geology and ore deposits of the Tintic mining district, Utah; 
U.S. Geol. Survey Prof. Paper 107, p. 52, 1919. 



52 



GOLD HILL MINING DISTBICT, UTAH 



Alkali basalt. — Small outcrops of alkali basalt are 
exposed on both sides of Overland Canyon from about 
the mouth of Blood Canyon to the eastern border of 
the quadrangle. The rock is also found near the 
mouth of North Pass Canyon and in Rodenhouse 
Wash. The North Pass Canyon exposure appears to 
be a dike, but the others are Hows. -The small size 
and wide distribution of the present outcrops indicate 
that the rock formerly had a much greater extent. 

The rock is dark gray in all exposures and is charac- 
terized by the presence of numerous small reddish- 
brown grains of iddingsite. All but the dike are 
vesicular, and the vesicles locally have a calcite filling, 
Phenocrysts of glassy pyroxene and of feldspar as 
much as an inch in length are found in the dike and in 
the more easterly outcrops. 

The sections show that the chief constituents are 
olivine, largely altered to iddingsite, augite, and plagio- 
clase. Magnetite, apatite, and amygdular calcite are 
present in minor amounts. Most of the iddingsite 
is deep reddish brown, but a little is distinctly yellow- 
ish. Its optical properties are similar to those of an 
iddingsite from Gatos Creek, Colorado, described by 
Ross and Shannon. 9 Augite is present in notable 
quantities. In a specimen taken from the outcrop 
south of the Midas mine one large group of augite 
crystals has a spherulitic habit. Both andesine and 
oligoclase are present in the rock. Andesine occurs 
as larger lath-shaped crystals, and the sodic oligoclase 
as small anhedrons. Olivine, iddingsite, augite, and 
andesine make up the bulk of the rock, with only a 
small amount of interstitial material. This, however, 
instead of being glassy, as in the typical intersertal 
texture, is holocrystalline and is composed of small 
crystals of iddmgsite, augite, and oligoclase. In this 
material most of the apatite is concentrated as long, 
slender needles. 

The strikingly porphyritic varieties from the east- 
ern border of the quadrangle contain in addition to 
these minerals phenocrysts an inch or less in length 
of augite, andesine, quartz, and a potash-soda feldspar. 
The quartz phenocrysts are not abundant, and all show 
rather extreme resorption. The potash-soda feldspar 
is biaxial negative and has an optic angle (2V) esti- 
mated by C. S, Ross to be about 20°. Its indices of 
refraction are those of sanidine, a being 1.518 ±0.003. 
The extinction angle on cleavage plates parallel to 
010 are 4°-5° and on plates parallel to 001 up to 9°, 
indicating that the mineral must be triclinic. It shows 
no twinning. These properties are similar to those 
found by Iddings for a feldspar occurring in litho- 
physae in Yellowstone National Park, which analysis 
proved to contain 5.08 percent of Na 2 and 8.36 per- 
cent of K 2 0. 10 

•Boss, C. S., and Shannon, E. V., The origin, occurrence, composition, and 
physical properties of the mineral Iddingsite; TJ.S. Nat. Mus. Proe., vol. 67, p. 
14, 1925. 

"Iddings, J. P., Obsidian Cliff, Yellowstone National Park: U.S. Oeol. Survey 
Seventh Ann. Bept., p. 268, 1888. 



The presence of phenocrysts of this highly alkaline 
feldspar and quartz in certain of the lavas and its 
absence in others is thought to be the result of the 
rapidity with which the porphyries apparently con- 
solidated. The lava on the eastern border of the 
quadrangle is much finer grained than the nonpor- 
phyritic varieties, and, although it is filled with vesicles, 
these are much smaller than normal, suggesting a cool- 
ing so rapid that the expelled volatile matter had no 
opportunity to collect. The result of so rapid a cool- 
ing would be the preservation of such phenocrysts as 
would otherwise be resorbed were the solidification 
more gradual. 

These rocks closely resemble in mineralogic composi- 
tion those grouped by Rosenbuseh under the name 
alkali basalt, in his family of trachydolerites. 11 The 
texture is that of basaltic rocks, and the abundance 
of soda-rich plagioclase feldspar is indicative of their 
alkaline affinities. 

A partial analysis of the rock indicates that the 
silica percentage is somewhat higher and the soda per- 
centage somewhat lower than in the typical analyses 
of alkali basalts quoted by Rosenbuseh, but the potash 
content is much higher than in the normal basalt. 
The specimen analyzed was obtained 1,200 feet north- 
east of benchmark 5509 in Overland Canyon. The 
rock here does not contain any of the large phenocrysts 
of potash-soda feldspar, and no potash mineral was 
recognized in the thin section, although the rock is 
holocrystalline. It is possible that the potash found 
by the analysis is present as a potassium-aluminum 
silicate in isomorphous combination with the plagio- 
clase, but there is no evidence for this view other than 
the apparent absence of a potassium-bearing mineral 
in the mode. 

Partial analysis of alkali basalt 



[J. Q. FaireMId, analyst] 



2.86 



SiO,.. — 47.36 K 8 

Na 2 0_- 2.80 

Pyroclastic rocks. — Tuffs and breccias are exposed in 
the vicinity of Deep Creek, in Rodenhouse Wash, and 
in Blood Canyon. 

The tuffaceous rocks west of Deep Creek and in 
Rodenhouse Wash are dark-purplish or reddish well- 
bedded rocks that contain larger fragments of andesine 
or labradorite, hornblende, and locally augite set in a 
matrix of glass fragments, which are locally devitrified, 
particularly near bedding planes. Most of the speci- 
mens examined are considerably altered. Another 
variety of tuff, which is poorly cemented, was found on 
the southwest slope of Twin Peaks. Except for a few 
small crystals of quartz, it is composed entirely of 
glass fragments, whose index of refraction is 1.495. 

The breccias in the Deep Creek region are of small 
extent and, in part at least, fill old volcanic necks. 

» Rosenbuseh, Harry, Elemente der Gestetaslehre, 1th ed., by A. Osann, pp. 454- 
458, Stuttgart, 1923. 



TEETIAEY SYSTEM 



53 



The rock fragments contained are entirely of the sur- 
rounding andesites or latites. The breccias in Roden- 
house Wash and Blood Canyon differ from those in the 
Deep Creek region in containing numerous fragments 
both of sedimentary rocks and of the quartz mon- 
zonite. The Rodenhouse Wash exposures are mostly 
well bedded and probably represent surface accumu- 
lations, but those in Blood Canyon are thoroughly 
altered and are thought to mark centers of eruption, 

ALTERATION OF THE VOLCAHIC ROCKS 

Three kinds of alteration of the volcanic rocks have 
been recognized. One of these is thought to have been 
the result of reactions occurring before the complete 
consolidation of the lava. The other two, which af- 
fected the minerals in the groundmass as well as the 
phenocrysts, were considerably later. Of these an 
alteration characterized by a series of silica minerals 
with calcite was restricted to volcanic necks or their 
vicinity, but the other, in which zeolites were abun- 
dantly developed, had no apparent relation to the 
necks. 

Some of the hornblende and magnetite and all of 
the iddingsite found in these lavas are clearly reaction 
products of the earlier-crystallized minerals with the 
still molten lava, A variety of chlorite with the opti- 
cal properties of delessite seems to furnish a connecting 
link between these minerals and those produced by 
the other kinds of alteration, as it replaces augite, 
hornblende, biotite, and plagioclase phenocrysts and 
cuts the groundmass of various rocks in veinlets and 
in more irregular areas. In some places it has appar- 
ently been developed with magnetite in the alteration 
of biotite or hornblende, and in others it is associated 
with calcite, which as a rule is found with the later 
minerals. The conditions under which delessite forms 
seemingly have a wide range. A colorless chlorite 
whose index of refraction is much less than that of 
delessite has essentially the same habit as delessite 
but is not nearly as abundant. A mineral thought to 
be leverrierite was found with delessite in Blood Can- 
yon, where it is locally abundant. 

Evidence of the alteration characterized by silica 
minerals was found only in specimens from volcanic 
necks or in rocks adjacent to the necks. The silica 
minerals are locally associated with calcite and occur 
as veinlets ranging from those of microscopic size to 
some that are nearly a foot in width. In places the 
veinlets show enlargements with rather irregular out- 
lines. Tridymite, opal, chalcedony, quartz, and cal- 
cite are found in the veinlets, and where the age rela- 
tions can be determined the order of formation is that 
given, with tridymite earliest and calcite last. 

The zeolitic alteration was rather widespread and af- 
fected both flows and pyroclastic rocks with no appar- 
ent relation to the sites of extrusion, although there are 
important exceptions in that two necks east of Deep 



Creek show a nearly complete replacement of plagio- 
clase by thompsonite. The zeolites have replaced the 
feldspar phenocrysts and form irregular areas in the 
groundmass, Veinlets of the minerals are of minor 
extent. The minerals recognized are stilbite, analcite, 
thompsonite, and calcite. Locally these minerals are 
enclosed in veinlets of the silica minerals. 

The differences in habit and occurrence of the miner- 
als of the two groups prompt the suggestion that the 
silica series represents a concentration from a larger 
body of cooling rock than the zeolite series. The 
wide-spread occurrence of the zeolitic minerals indi- 
cates that the solutions which caused their formation 
were obtained from adjacent portions of the lava. 

A6E OF THE 70LCANIC BOCKS 

The volcanic rocks cannot be directly dated. So 
far as their relations to other rocks go, they are clearly 
younger than the Eocene (?) White Sage formation and 
the quartz monzonite, on both of which they rest 
unconformably. They are also thought to be younger 
than the Pliocene (?) sediments, which contain no 
pebbles of volcanic rock, although overlain by gravel 
which contains such pebbles. On the other hand, 
they are older than the Lake Bonneville sediments, 
from which they are separated by a period of consid- 
erable erosion. The Pliocene age of the prevolcanic 
sediments, however, is based (see p. 49) on their rela- 
tions to the volcanic rocks. As far as stratigraphic 
evidence goes, therefore, the volcanic rocks are later 
than Eocene (?) and earlier than the Lake Bonneville 
Pleistocene. Geomorphic evidence, however, permits 
a somewhat closer dating. The volcanic rocks rest 
upon a surface which is very similar to the present one 
and which is clearly later than the normal faulting of 
the Basin Range type. The position of lavas and brec- 
cias in Rodenhouse Wash and Blood Canyon shows 
indisputably that they were erupted in valleys cut in 
an old topographic surface, the dissection of which 
was initiated by Basin Range faulting. The large area 
east of Deep Creek, moreover, apparently lies along 
the course of one of the Basin Range faults. Finally, 
the dike of alkali basalt in North Pass Canyon is 
thought to cut the gravel developed as a result of the 
faulting. The age of the Basin Range faulting is dis- 
cussed on page 64, where it is shown that a Pliocene 
date is probable. With allowance for the prevolcanic 
erosion that has been noted, the date of eruption prob- 
ably was in the later part of the Pliocene. 

GRAVEL AND CLAY (FUOCENE (?) TO RECENT) 

About one-third of the area of the quadrangle is 
underlain by partly or completely unconsolidated sedi- 
ments derived from the older rocks by weathering and 
erosion. They include gravel and clay deposited in 
the Pleistocene Lake Bonneville u in addition to 



« Gilbert, O. K„ Lake Bonneville: U.S. Geol. Survey Mon. 1, 1890. 



54 



GOLD HILL MINING DISTRICT, UTAH 



terrestrial gravel and clay that are both older and 
younger than the lake beds. Locally these deposits 
may be readily distinguished from one another, but 
in many places the assignment of an exposure to a 
definite chronologic position is impossible, either 
because it is isolated or because there is no sharp line 
of division between beds which in one place were 
clearly deposited at one time and in a second place at 
another. For the purposes of this report the beds will 
be arbitrarily grouped into three divisions— (1) older 
gravel and clay, (2) younger gravel and clay, (3) Lake 
Bonneville beds. 

OIDEB GBAVEI AND CIAT 

At several places in the quadrangle there are ex- 
posures of gravel and clay which are clearly out of 
adjustment with regard to the present topography. 
These are thought to be remnants of deposits that were 
formed before the most recent faulting in the area. 
One area in which such gravel is displayed extends 
from North Pass Canyon north and east to the Midas 
mine. One almost continuous exposure of gravel in 
this area extends from the low ridge west of hill 6267, 
near the mouth of North Pass Canyon, northward to 
the divide between North Pass and Blood Canyons. 
Between these two places outcrops of bedrock are 
found at several points in the bottoms of gulches. The 
gravel lies as much as 450 feet above the present drain- 
age channels. Here there appears to be almost no 
cementation of the beds. Pebbles and boulders as 
much as several feet in diameter lie in a matrix of 
smaller rock fragments and sand. The pebbles and 
boulders consist of rocks derived from formations 
exposed some distance to the west and north of the 
gravel outcrops, the formations adjacent to the gravel 
being almost entirely unrepresented. In Blood Canyon 
there are also gravel deposits on the higher slopes 
which are thought to be contemporaneous with those 
to the south. Still another area is south and south- 
west of the Midas mine, where the gravel is well 
cemented by calcium carbonate and contains almost 
no boulders of quartz monzonite, although there are 
extensive exposures of that rock immediately to the 
north. In all these localities there is some evidence to 
indicate that the gravel had been deposited before the 
volcanic rocks were erupted. (See p. 49.) 

Clifton Flat is also underlain by material now being 
actively dissected. The beds consist chiefly of clay, 
with only a minor amount of coarser material. Near 
the road leading to Clifton they overlie volcanic rocks 
and may therefore be in part younger than the gravel 
near North Pass Canyon. 

Another area in which old gravel is exposed is on the 
west side of Dutch Mountain in a belt that roughly 
parallels Trail Gulch. This gravel is apparently un- 
consolidated and in places, as in the isolated patch 
east of hill 6518, contains a great deal of clay. The 
rocks represented by the boulders are those exposed to 



the east. The gravel was clearly deposited under 
conditions differing from those of the present time. 
The isolated patch mentioned above, for example, is 
found at the head of a canyon that drops 400 feet in 
a horizontal distance of 3,000 feet. In Woodman 
Canyon ridges made up of gravel rise over 200 feet 
above the canyon bottom, which, in many places, is 
cut in solid rock. 

These are the only areas in which the early age of 
the gravel or clay is definitely indicated. There are 
probably others, particularly north and northwest of 
Ochre Mountain and on the southeast side of Dutch 
Mountain, but in these the evidence is not clear. 

YOUNGER GRAVEL AND CLAY 

Several different kinds of sediment are included in 
the group of younger gravel and clay. The most 
extensive are the gravel deposits that flank all the 
highlands. These are poorly sorted, poorly stratified, 
and uncemented and do not differ materially from the 
gravel found throughout the Great Basin region. At 
least three stages of fairly recent deposition of the 
gravel was recognized. Less extensive are the sand 
and clay deposits in Deep Creek Valley, which lie 
above the level of Lake Bonneville. These occur not 
only along the present course of Deep Creek but also 
in a linear zone in the eastern parts of sees. 3, 10, 15, 
and 22, T. 9 S., E. 19 W. The younger gravel also 
includes the areas of talus mapped on the higher part 
of Dutch Mountain. These are limited to places in 
which the basal part of the Woodman formation is 
exposed. The sandstones which are so numerous at 
that horizon break up on weathering into small frag- 
ments and form talus slopes that conceal not only the 
beds of the Woodman but of the formation beneath. 

LAKE BONNEVILLE BEDS 

At the time of maximum extent of Lake Bonneville 
nearly one-fifth of the quadrangle was under water. 
For the most part the flooding by the lake waters 
resulted only in a reworking of previously deposited 
gravel. In two areas, however, lacustrine clay was 
deposited. These were in the Deep Creek Valley and 
in the northeast corner of the quadrangle. 

In many places the reworking of the older gravel 
was slight and is expressed chiefly in distinct beach 
lines. Locally, however, especially where outcrops of 
hard rock influenced the shore currents, impressive 
shore features were developed. One of the most strik- 
ing of these is the large hooked spit on the east side of 
Dutch Mountain. This is over a mile long and for 
much of this distance rises 600 feet above the gravel 
slope to the east. There is a smaller similar spit to 
the south on the north side of Tribune Gulch, and 
another on the south side of the prominent quartzite 
hill east of the Eube mine. All three of these were 
built up to the highest level of the lake, an altitude of 
about 5,200 feet. 



GEOLOGIC STBUCTTJBE 



55 



Another prominent feature resulting from the re- 
working of older gravel by the Lake Bonneville waters 
is the bar half a mile south of the dry lake in Bar Creek. 
This narrow, even-topped ridge approaches the regu- 
larity of a railroad grade. 

The clay deposits in the localities mentioned above 
are light-colored and calcareous and are similar to those 
found throughout the area formerly covered by the 
lake. 13 

GEOLOGIC STKUCTUBE 

The accompanying geologic maps (pis. 1 and 2) show 
a notable lack of continuity in the older sedimentary 
formations that is in large part the result of a pro- 
tracted period of crustal unrest, during which these 
older rocks were warped and complexly faulted. By 
means of the mutual relations of the faults and, to a 
less extent, the folds, a structural history of the quad- 
rangle was deciphered that appears to be unique for 
this portion of the Great Basin. 

The determined sequence of events indicates that 
the deformation was cyclic in character, in that an 
initial stage in which compressive forces were active 
was followed by one in which normal faulting took 
place. (See p. 65.) Five cycles of this character 
were distinguished; the first two are thought to have 
been of Cretaceous or early Eocene age, the third was 
contemporaneous with the Eocene (?) White Sage for- 
mation, and the fourth and fifth are considered to have 
been of about the same age as the quartz monzonite 
intrusion. 

There is a progressive variation in the character of 
the structural features developed during the successive 
cycles. Folding appears to have been dominant in the 
compressive stage of early cycles, low-angle thrust 
faults of large throw characterize this stage of the third 
cycle, and transverse or tear faults are particularly 
abundant in the later cycles. It is suggested that the 
change in character through the five cycles is the 
reflection of a progressively lighter load and that 
transverse faults have optimum conditions for their 
formation at or near the surface. 

The normal faults that were formed in the second 
stage of each of the five cycles show a decrease in both 
number and intensity in the successive cycles. A 
possible explanation for this decrease is considered to 
be that the additional strength or rigidity imparted 
by the successive periods of compression made relax- 
ational movements, as typified by the normal faults, 
less and less necessary. 

A later period of normal faulting followed the 
development of a post-mature erosion surface over the 
older structural features. This later faulting is 
thought to have begun in late Pliocene time. The 
faults are not all strictly contemporaneous, and many 
of them utilized earlier fault planes. 

» Gilbert, O. K., Lake Bonneville: U.S. Cteol. Survey Mori. 1, p. ISO, 1890. 
Nolan, T. B., Potash brines in the Oreat Salt Lake Desert, Utah: U.S. Qeol. 
Survey Bull. 795, pp. 32-34, 1927, 



STBUCTTTRAX CYCIES 

In a region that is structurally as complex as the 
Gold Hill quadrangle, a detailed geographic descrip- 
tion of folds and faults tends to conceal the succession 
of events and to becloud the correlation of related 
features that are widely separated areally. The 
following section gives a chronologic account of the 
major structural features and outlines their relations 
to one another. The detailed observations upon which 
this section is based are given on pages 66-91, where 
the structural features in each of the six structural 
blocks into which the quadrangle is divided are de- 
scribed geographically. The fault map of the quad- 
rangle (pi. 3) and the geologic structure sections on 
plates 1 and 2 will be found useful in the reading of 
both discussions. 

FIRST CYCLE 

First stage. — Structural features assignable to the 
first stage of the first cycle were not widely recognized. 
This may be due in part to the impossibility of making 
age assignments for isolated features and in part to 
the probability of renewed movement along faults 
that first became active at this time. Two rather 
minor low-angle faults, thought to be thrusts, and local 
folds are found on the southwest flank of Ochre 
Mountain, and as they are cut by normal faults that 
definitely belong to the second stage of this cycle, they 
are considered to record an initial stage of compression. 

The meager evidence available provides scant infor- 
mation as to the, character of the compressive forces. 
Transverse faults appear to be absent, but the folds 
and reverse faults are so few and small that their rela- 
tive importance is not known. 

Second stage. — Several normal faults with relatively 
small throw on Ochre Mountain are clearly older than 
the minor thrusts that belong to the second cycle. 
There is also a group of small normal faults on Dutch 
Mountain of similar strike that are cut by faults of 
the second cycle. Both of these groups are therefore 
believed to represent a period of rather wide-spread 
normal faulting that followed the minor thrusting and 
folding of the first stage. 

SECONB CYCLE 

First stage. — Folds, thrusts, and transverse faults 
were formed during the first stage of the second cycle, 
but folding was far more intense than faulting. The 
continuity of the folds has been largely destroyed by 
the disturbances of later cycles, but the portions that 
can be examined leave no doubt that they were of con- 
siderable magnitude. 

The Deep Creek Mountains south of North Pass 
Canyon appear to represent the western half of a major 
anticline whose axis coincides approximately with the 
eastern border of the mountains, as easterly dips are 
found in the Prospect Mountain quartzite south of 
Dry Canyon. In North Pass Canyon itself the Cam- 
brian formations that crop out near the mouth of the 



56 



GOLD HILL MINING DISTRICT, UTAH 



canyon show an anticlinal structure that is thought 
to be a continuation of that found farther south. 

North of this anticline an equally large but unrelated 
anticline in Mississippian and Pennsylvanian rocks is 
exposed around the borders of the south half of Clifton 
Flat. A much-faulted core of Ochre Mountain lime- 
stone is overlain on each side by a large thickness of 
the Oquirrh formation. The beds of the Oquirrh on 
the west flank show some minor superposed folds that 
were probably formed during a later cycle. 

A third large fold, a recumbent anticline, is best 
exposed on the southern flank of Twin Peaks in the 
northwestern part of the quadrangle, and its axis may 
be traced for some distance. The axial plane of the 
fold strikes about N. 15° E. over this area, but in 
detail it varies considerably because of later warping. 

All three of these major folds are cut by normal 
faults that are older than the thrust faults formed 
during the succeeding cycle, and it is believed that they 
are therefore essentially contemporaneous. Their 
present close association is fortuitous, as each now lies 
in a separate thrust plate. 

The thrusts that are contemporaneous with these 
folds are for the most part of minor importance. The 
only recognized large thrust of this age is found on 
Dutch Mountain. This has been called the Dutch 
Mountain thrust, as it has a nearly continuous out- 
crop around the crest of the mountain. Stratigraph- 
ically the thrust is not striking, because it has Ochre 
Mountain limestone above and the Woodman forma- 
tion below — the normal sequence. 'The bedding of 
both formations is discordant to the contact, however, 
and the thickness of the underlying Woodman forma- 
tion varies notably from place to place. 

Continuations of the thrust are found to the south 
on peak 7011, on the south side of Pool Canyon, and, 
at a much lower altitude, on the west side of Accident 
Canyon. At both localities the relations are the same, 
the Ochre Mountain limestone resting upon the Wood- 
man formations, but in these exposures the Woodman 
is considerably crumpled. 

The segment near the mouth of Accident Canyon 
has a rather low dip, comparable to that shown by the 
thrust below the summit of Dutch Mountain. As the 
fault is traced south along Accident Canyon, however, 
the dip steepens and is as high as 60° at the point where 
it is cut off by a later normal fault. This zone of 
steeper dip between two portions with relatively flat 
dip must be an original feature of the thrust, as its 
origin by a later warping is precluded by the lack of 
similar warping in the adjacent beds. The absence of 
such warping is shown rather conclusively by the inliers 
of Madison limestone near the south end of the steeply 
dipping portion of the fault. 

Some transverse faulting also occurred during this 
stage. The west-northwest fault in North Pass Can- 
yon and the parallel Pool Canyon fault on Dutch 



Mountain appear to have been formed at this time. 
Other faults with similar strike became active in the 
third cycle, however, and locally it is difficult to dis- 
tinguish between the two ages. 

The dominant structural features of this stage of 
the second cycle are folds of considerable magnitude. 
Thrust faults are rather numerous but have relatively 
small displacements; and transverse faulting appears 
to have been of even less magnitude. The thrust 
faults appear to have been formed by the sliding of 
more resistant stratigraphic units over less resistant 
underlying beds, which yielded to the compression 
by crumpling. Their character, as well as the size 
of the folds, suggests that the deformation took place 
under a relatively heavy load. The strike of the trans- 
verse faults and the strike of the axis of the recumbent 
fold indicates that the compressive forces were directed 
from the west-northwest. 

Second stage. — Normal faults that were formed dur- 
ing the second stage of the second cycle are found 
throughout the quadrangle. They do not appear to 
be quite as numerous as the faults of this character 
developed in the preceding cycle, but many of them 
have unusually large throws. Several of them are 
also characterized by the fact that they mark lines of 
weakness that persisted throughout several cycles. 

The fault along the east base of the Deep Creek 
Mountains, for example, has a throw of 6,000 feet, of 
which 4,000 feet may be assigned to this cycle, as a 
thrust formed in the next cycle is displaced only 2,000 
feet. Similarly the Spotted Fawn fault, on the east 
side of Dutch Mountain, has a throw of 2,000 feet, of 
which 1,500 feet, as shown by its relations to a thrust 
of the next cycle, can be assigned to this stage. The 
Trail Gulch fault, on the west side of Dutch Mountain, 
has had a comparable history. The Tank Wash and 
Bar Creek faults, in the northwestern part of the 
quadrangle, are also of this class, with total throws of 
about 4,000 and 5,000 feet respectively, of which the 
greater part took place during this stage. 

THIKB CYCUDE 

First stage. — In the first stage of the third cycle 
large-scale overthrusting was accompanied by rela- 
tively minor transverse faulting and slight folding. 
Two large overthrusts were formed during this stage — 
an earlier one, which appears to have been limited 
between two transverse faults, and a later one, which 
has overridden the earlier structure. A long period of 
erosion is thought to have separated the beginning of 
this cycle from the last stage of the preceding one. 
Although the total movement along either of the 
thrusts cannot be determined from the evidence pro- 
vided within the quadrangle, it must have been rather 
large, because distinctive facies of the Carboniferous 
formations are found above each of the thrusts (p. 23 
and fig. 5). . 



GEOLOGIC STETJCTTJRE 



57 



The earlier or North Pass thrust is exposed in only 
a few places, but the distribution of the central facies 
of the Carboniferous rocks makes it fairly certain that 
the thrust extends as far north as the Pool Canyon 
transverse fault, on the south side of Dutch Mountain. 

In North Pass Canyon the thrust is exposed in only 
one small outcrop. Minor structural features accom- 
panying the thrust are locally well exposed, however, 
and by piecing these together a fairly adequate picture 
of the structural conditions may be obtained. The 
most striking of these minor features are found on the 
west flank of the anticline and north of the transverse 
fault along the floor of the valley, both of which were 
formed in the preceding cycle. They consist of thrust 
plates of the more resistant pre-Carboniferous forma- 
tions that have overridden the axis of the anticline. 
The plates decrease in number and in thickness east- 
ward, and at the mouth of the canyon, north of hill 
6267, only one 100-foot plate, which is composed of 
Laketown dolomite, remains. This plate is overlain 
by beds of the Oquirrh formation that are essentially 
continuous with the large outcrop that" nearly sur- 
rounds Clifton Flat. The contact between the shat- 
tered Laketown dolomite and the Oquirrh formation 
is the plane of the North Pass thrust. 

The minor thrusts very clearly are limited south- 
ward by the older transverse fault, and it seems rather 
certain that the main North Pass thrust was also so 
limited, as it is nowhere exposed to the south, although 
many places along the ridge lines reach sufficiently 
high altitudes to have been cut by the thrust if it had 
originally extended that far. 

The relations of the thrust plates beneath the main 
thrust to the older anticline are those that would 
result had the anticline been deeply eroded and then 
subjected to compression from the west, the more 
competent beds on the western limb of the fold riding 
forward over the eroded core and extending for short 
distances farther east. This in turn implies that the 
main thrust at this locality was also moving over a 
surface of erosion. A measure of the amount of erosion 
is given by the normal fault along the eastern front of 
the Deep Creek Mountains, which had a pre-thrust 
throw of 4,000 feet. By the time of the thrusting, 
however, erosion must have completely beveled across 
the fault, for the thin plate of Laketown dolomite 
crossed it without interruption. 

The North Pass thrust may also be located rather 
closely at two other localities — along the Lincoln 
Highway south of Ochre Mountain and in the south- 
east corner of the quadrangle. These provide a meas- 
ure of the minimum movement along the thrust, for 
they are about 9 miles apart in a direction approxi- 
mately at right angles to the strike of the thrust. 

The North Pass thrust appears to be limited north- 
ward by the Pool Canyon transverse fault, as the 
Carboniferous formations of the central facies that 

35311-35 6 



overlie the thrust are cut off by the transverse fault; 
north of the fault lower Paleozoic formations are ex- 
posed that are thought to be the continuation of those 
exposed south of the parallel transverse fault in North 
Pass Canyon. The North Pass thrust cannot be 
recognized north of the Pool Canyon fault, and evi- 
dence is provided by a nearly contemporaneous thrust 
that it was never present in that region. 

The limitation of the North Pass thrust between 
two transverse faults that are, in part at least, older 
than the thrust is thought to be the result of the erosion 
that took place between the second and third cycles, 
which appears to have exposed the resistant Prospect 
Mountain quartzite both to the north and south of the 
transverse faults and thus prevented the overriding 
that is found between the faults, where the quartzite 
was deeply buried. 

The second major thrust, the Ochre Mountain 
thrust, has a wider extent and is well exposed on both 
Ochre Mountain and Dutch Mountain. On the 
south side of Ochre Mountain this thrust abuts against 
a younger transverse fault, beyond which it has been 
almost entirely removed by erosion, and on the north 
it disappears beneath the gravel flanking Dutch 
Mountain. 

The Ochre Mountain thrust, like the North Pass 
thrust, is thought to be an "erosion thrust" in the 
sense that the overriding block moved over the then 
existent surface. The chief evidence for this belief is 
found in the behavior of the overriding block where 
the thrust crosses the Pool Canyon transverse fault. 
Although there has been an intrusion of quartz mon- 
zonite along the transverse fault, the major relations 
between the two faults are readily seen. The thrust 
is clearly the younger, as there is no sign of the trans- 
verse fault in the beds above the thrust. North of 
the transverse fault a gently dipping sequence of beds 
with Madison limestone at the base lies above the 
thrust. South of the transverse fault, however, the 
beds are considerably disturbed and are even locally 
overturned, and beds high in the Woodman formation 
lie immediately above the thrust. South of the trans- 
verse fault, also, the thrust is about 300 feet higher 
than it is to the north. The relations outlined indicate 
that the overriding thrust plate was considerably 
hindered in its forward movement at this place, and it 
seems probable that the structural features in the 
overridden beds would prove to be an obstacle only if 
they were exposed at the surface at the time of thrust- 
ing. The occurrence of thin thrust plates of a single 
formation below the main thrust on both Dutch 
Mountain and the north slope of Ochre Mountain also 
imply, as in the North Pass thrust, that the Ochre 
Mountain thrust reached the surface. 

In addition to the nearly continuous outcrops of the 
Ochre Mountain thrust on Ochre Mountain and Dutch 
Mountain, the thrust is exposed in several places in- 



GEOLOGIC STRTJCTOTE 



57 



The earlier or North Pass thrust is exposed in only 
a few places, but the distribution of the central facies 
of the Carboniferous rocks makes it fairly certain that 
the thrust extends as far north as the Pool Canyon 
transverse fault, on the south side of Dutch Mountain. 

In North Pass Canyon the thrust is exposed in only 
one small outcrop. Minor structural features accom- 
panying the thrust are locally well exposed, however, 
and by piecing these together a fairly adequate picture 
of the structural conditions may be obtained. The 
most striking of these minor features are found on the 
west flank of the anticline and north of the transverse 
fault along the floor of the valley, both of which were 
formed in the preceding cycle. They consist of thrust 
plates of the more resistant pre-Carboniferous forma- 
tions that have overridden the axis of the anticline. 
The plates decrease in number and in thickness east- 
ward, and at the mouth of the canyon, north of hill 
6267, only one 100-foot plate, which is composed of 
Laketown dolomite, remains. This plate is overlain 
by beds of the Oquirrh formation that are essentially 
continuous with the large outcrop that* nearly sur- 
rounds Clifton Flat. The contact between the shat- 
tered Laketown dolomite and the Oquirrh formation 
is the plane of the North Pass thrust. 

The minor thrusts very clearly are limited south- 
ward by the older transverse fault, and it seems rather 
certain that the main North Pass thrust was also so 
limited, as it is nowhere exposed to the south, although 
many places along the ridge lines reach sufficiently 
high altitudes to have been cut by the thrust if it had 
originally extended that far. 

The relations of the thrust plates beneath the main 
thrust to the older anticline are those that would 
result had the anticline been deeply eroded and then 
subjected to compression from the west, the more 
competent beds on the western limb of the fold riding 
forward over the eroded core and extending for short 
distances farther east. This in turn implies that the 
main thrust at this locality was also moving over a 
surface of erosion. A measure of the amount of erosion 
is given by the normal fault along the eastern front of 
the Deep Creek Mountains, which had a pre-thrust 
throw of 4,000 feet. By the time of the thrusting, 
however, erosion must have completely beveled across 
the fault, for the thin plate of Laketown dolomite 
crossed it without interruption. 

The North Pass thrust may also be located rather 
closely at two other localities — along the Lincoln 
Highway south of Ochre Mountain and in the south- 
east corner of the quadrangle. These provide a meas- 
ure of the minimum movement along the thrust, for 
they are about 9 miles apart in a direction approxi- 
mately at right angles to the strike of the thrust. 

The North Pass thrust appears to be limited north- 
ward by the Pool Canyon transverse fault, as the 
Carboniferous formations of the central facies that 

35311-38 B 



overlie the thrust are cut off by the transverse fault; 
north of the fault lower Paleozoic formations are ex- 
posed that are thought to be the continuation of those 
exposed south of the parallel transverse fault in North 
Pass Canyon. The North Pass thrust cannot be 
recognized north of the Pool Canyon fault, and evi- 
dence is provided by a nearly contemporaneous thrust 
that it was never present in that region. 

The limitation of the North Pass thrust between 
two transverse faults that are, in part at least, older 
than the thrust is thought to be the result of the erosion 
that took place between the second and third cycles, 
which appears to have exposed the resistant Prospect 
Mountain quartzite both to the north and south of the 
transverse faults and thus prevented the overriding 
that is found between the faults, where the quartzite 
was deeply buried. 

The second major thrust, the Ochre Mountain 
thrust, has a wider extent and is well exposed on both 
Ochre Mountain and Dutch Mountain. On the 
south side of Ochre Mountain this thrust abuts against 
a younger transverse fault, beyond which it has been 
almost entirely removed by erosion, and on the north 
it disappears beneath the gravel flanking Dutch 
Mountain. 

The Ochre Mountain thrust, like the North Pass 
thrust, is thought to be an "erosion thrust" in the 
sense that the overriding block moved over the then 
existent surface. The chief evidence for this belief is 
found in the behavior of the overriding block where 
the thrust crosses the Pool Canyon transverse fault. 
Although there has been an intrusion of quartz mon- 
zonite along the transverse fault, the major relations 
between the two faults are readily seen. The thrust 
is clearly the younger, as there is no sign of the trans- 
verse fault in the beds above the thrust. North of 
the transverse fault a gently dipping sequence of beds 
with Madison limestone at the base lies above the 
thrust. South of the transverse fault, however, the 
beds are considerably disturbed and are even locally 
overturned, and beds high in the Woodman formation 
lie immediately above the thrust. South of the trans- 
verse fault, also, the thrust is about 300 feet higher 
than it is to the north. The relations outlined indicate 
that the overriding thrust plate was considerably 
hindered in its forward movement at this place, and it 
seems probable that the structural features in the 
overridden beds would prove to be an obstacle only if 
they were exposed at the surface at the time of thrust- 
ing. The occurrence of thin thrust plates of a single 
formation below the main thrust on both Dutch 
Mountain and the north slope of Ochre Mountain also 
imply, as in the North Pass thrust, that the Ochre 
Mountain thrust reached the surface. 

In addition to the nearly continuous outcrops of the 
Ochre Mountain thrust on Ochre Mountain and Dutch 
Mountain, the thrust is exposed in several places in- 



58 



GOLD HILL MINING DISTBICT, UTAH 



roof pendants within the quartz monzonite stock and 
also in "windows" on the northwest slope of Dutch 
Mountain and within Ochre Mountain, The mini- 
mum movement along the thrust as indicated by these 
exposures may be placed at 4 miles, but obviously the 
total amount is much more, as the lithologic differences 
between the two facies of the Carboniferous formations 
persist throughout this distance. 

The Ochre Mountain thrust and the North Pass 
thrust have been placed in the same structural cycle, 
because each of them has the same relations to the 
faults and folds of other cycles. In Pool Canyon the 
Ochre Mountain thrust is clearly shown to be the 
younger of the two, although there is some evidence 
at that place to indicate that the age difference is not 
great. The thin-bedded limestones and sandstones of 
the Oquirrh formation beneath the thrust south of the 
Pool Canyon transverse fault are much less resistant 
to erosion than the massive lower Paleozoic dolomites 
north of it. The weaker beds now stand at a higher 
altitude, however, and as the Ochre Mountain thrust 
appears to have moved over the surface at this point, 
it follows that they must also have been at a higher 
altitude at the time that thrust was active. This in 
turn implies that but little time could have elapsed 
between the Ochre Mountain thrust and the North 
Pass thrust, which brought the weaker beds into the 
position they now have. 

The slight difference in age between the two thrusts 
provides additional evidence that the North Pass 
thrust was limited northward by the Pool Canyon 
transverse fault, for north of that fault the Ochre 
Mountain thrust plate rests upon lower Paleozoic for- 
mations without the intervening mass of Carboniferous 
rocks that forms the North Pass thrust plate. As the 
two thrusts were almost contemporaneous there was 
obviously no time for the North Pass thrust plate to 
be eroded north of the Pool Canyon fault before the 
Ochre Mountain thrust was formed, and it must 
therefore never have extended that far. 

The two major thrust faults were accompanied by 
many small thrusts, and in addition there appears to 
have been a reversal of movement along at least one of 
the older normal faults during this stage. On the west- 
ern or hanging-wall side of the Trail Gulch fault, for 
example, the Oquirrh formation shows several small 
folds that in places are overturned; similar folds are 
absent in the footwall. Furthermore, neither this 
fault nor the beds on its hanging wall have been 
affected by the deformation shown by the Ochre 
Mountain thrust and the Mississippian beds above 
the thrust in the region where the thrust crosses the 
Pool Canyon transverse fault. Both of these features 
are most readily explained by the assumption of re- 
newed movement along the Trail Gulch fault, by 
which beds on one side of the fault could be deformed 
independently of those on the other side. 



Folding during tins stage was confined to the 
relatively small drag folds that are associated with the 
thrusts and with the renewed movement along the 
Trail Gulch fault. Some gentle broad warping may 
have taken place, such as the warping of the axial 
plane of the recumbent anticline of the second cycle, 
but it appears to have been of minor intensity. 

Several west-northwest transverse faults also ap- 
pear to be of this age, as they have the same 
relations as the major thrusts to other faults. Some 
transverse faults of this strike became active during 
the second cycle, however, and others, such as the 
Pool Canyon fault, must have been active during 
both cycles. 

This stage of the third cycle appears to have been 
initiated, after a protracted period of erosion that 
followed the second cycle, by a long period of thrusting. 
The two most extensive overthrust masses in this 
region both moved over the then existing surface. 
Transverse faults were formed in moderate abundance, 
but only minor folds. All these features are thought 
to indicate fliat the deformation took place under a 
relatively light load. As the transverse faults corre- 
spond in strike to those of the preceding cycle, it is 
thought that the compression came from the west- 
northwest. 

Second stage. — The normal faults of the second stage 
are neither abundant nor of large throw. On Dutch 
Mountain and Ochre Mountain much of the normal 
faulting of this stage took place along older faults. 
In both areas most of the faults of this age cut the 
Ochre Mountain thrust, and the difference in throw 
of the thrust and of the rocks below the thrust provides 
a measure of the later movement, which in all the 
examples known has been relatively small. 

FOURTH CYCUB 

First stage. — The principal structural features of the 
first stage of the fourth cycle are four nearly east-west 
transverse faults, along which the horizontal move- 
ment may have been a mile or more. Minor steep 
thrusting and a small amount of gentle warping accom- 
panied the transverse faulting, and two series of faults 
that are thought to have conjugate relations are 
associated with the most northerly transverse fault 
(pp. 83-84). 

These transverse faults cut both the major over- 
thrusts of the preceding cycle and the normal faults 
that followed the overthrusting. For this reason as 
well as the change in the strike of the transverse 
faulting, they are considered to represent a new struc- 
tural cycle. 

The most southerly of the transverse faults is the 
Dry Canyon fault. It appears to have a nearly ver- 
tical dip throughout its exposed extent of 4 miles. The 
beds on the north side of the fault have been shifted 
about 1,000 feet to the east. 



GEOLOGIC STRUCTURE 



59 



The other three faults have somewhat more complex 
relations. The Blood Canyon transverse fault may 
be traced for nearly 8 miles and over much of this 
distance has a steep dip similar to that of the Dry 
Canyon fault. To the east, however, its dip is notably 
flatter, and the thin-bedded members of the Oquirrh 
formation adjacent to it show complex crumplings 
that are absent away from the fault. A measurement 
of the movement along this fault is difficult, because 
for a considerable distance it separates the overriding 
block of the North Pass thrust from the overridden 
block. However, on the basis of the correlation of 
two older west-northwest transverse faults that. are 
found on the two sides of the Blood Canyon fault, the 
south side is thought to have moved about a mile 
to the east. 

The transverse fault on the south slope of Ochre 
Mountain also flattens notably eastward. The change 
in dip here appears to coincide with the presence of the 
Ochre Mountain thrust in the block south of the fault. 
The throw along the transverse fault cannot be exactly 
determined but must be large, because the Oquirrh 
formation overlies the Ochre Mountain thrust south 
of the fault, whereas to the north the Ochre Mountain 
limestone is above the thrust. If the block south of 
the transverse fault has moved to the east,, as would 
seem probable from the fact that the thrust is at a 
higher altitude on this side, a minimum movement 
of 3 miles appears necessary. The thrust has been 
considerably warped adjacent to the transverse fault, 
however, and the north side may therefore have moved 
to the east; in that case the movement may be nearer 
to 1 mile. 

The remaining major transverse fault of this stage, 
the Garrison Monster fault, is the most complex of 
the group. Its exposures are for the most part at or 
near the altitudes at which the Ochre Mountain thrust 
crops out, and the structural complexities observed 
appear to be the result of this coincidence, for to the 
east, at altitudes well below the thrust, the transverse 
fault is a simple steep fracture. To the west, near 
the thrust, the simple fault is replaced by a zone of 
moderately northward-dipping faults, which effect the 
same displacement as the single fault to the east. 
The strike of some of the faults in this zone changes 
to northeast and east-northeast as they extend west- 
ward and southward. Such continuations may show 
either normal or reverse faulting, but because of their 
relations to the faults in the transverse fault zone 
itself it seems certain that the dominant movement 
along them has been horizontal. 

The amount of horizontal movement along the trans- 
verse fault in the vicinity of the Garrison Monster 
mine must have been about 1% miles, the rocks north 
of the fault moving to the east. Westward in the 
fault zone, however, both the number of faults in the 
zone and the amount of displacement decrease, and 



in the low hills that end the northwesterly spur of 
Dutch Mountain the fault zone can no longer be 
recognized. 

The behavior of the Ochre Mountain thrust on both 
sides of the transverse fault appears to throw some 
light on the mechanics of faults of this type. North 
of the transverse fault exposures are few but are suffi- 
cient to show that the thrust surface cannot be greatly 
deformed but must rise with a relatively gentle slope 
to the east. South of the transverse fault, however, 
the numerous outcrops indicate that the thrust plane 
has been folded into a shallow syncline whose axis 
roughly parallels Accident Canyon and a marked anti- 
cline that coincides more or less closely with the crest 
of Dutch Mountain. The anticlinal axis appears to 
die out southwestward. 

The block north of the transverse fault, which has 
apparently undergone no folding, has moved eastward 
relative to the folded block to the south, suggesting 
that the true movement may have been westward by 
the southern block. There are several objections to 
this supposition, however — one being that in the pre- 
vious cycles the true direction of movement, wherever 
determinable, has been eastward. A more weighty 
objection lies in the fact that the Garrison Monster 
fault must curve to the north beyond its present most 
easterly outcrop, as it is clearly absent in the exposures 
of Prospect Mountain quartzite east and south of its 
projected continuation. The change in strike to the 
northeast is difficult to reconcile with a westward 
movement of the southern block. 

An eastward movement of the block north of the 
transverse fault, combined with the lack of contem- 
poraneous folding in the block, suggests that the 
crustal shortening required by the movement was 
accomplished by thrusting, and the change in strike of 
the transverse fault eastward may be interpreted as 
marking the line of overriding. The folding and minor 
reverse faulting in the block south of the transverse 
fault is of sufficient magnitude to account for the 
shortening required on that side, and the fact that the 
folding dies out southward appears to confirm the 
conclusion that the northern block was the active one. 

The general relations of the Garrison Monster trans- 
verse fault are shown diagrammatically in figure 8. It 
is not known how widely applicable these relations are 
to the other transverse faults in the quadrangle, but 
the lack of outcrops east of the similar transverse 
fault on the south side of Ochre Mountain suggest 
strongly that it also passes into a thrust. The flatten- 
ing of the Blood Canyon fault eastward may also 
indicate that the same relations hold for it. 

The compressive forces of this stage seem to have 
been relieved by movements that were accomplished 
under a very light load, for the dominance of faulting 
over folding is extreme, faults on the north aide of 
Dutch Mountain even appearing to replace some of 



60 



GOLD HILL MINING DISTKICT, UTAH 



the drag effects that would normally be expected to 
accompany transverse faults of this magnitude. 

Second stage, — There appears to have been essen- 
tially no normal faulting in the fourth cycle. In the 
Ochre Mountain and Dutch Mountain blocks there 
are a few faults that may belong to the second stage 
of this cycle, but it is difficult to distinguish them from 
the conjugate faults of the first stage. 



FIFTH CYCLE AND FAULTS BELATED TO THE 
MONZONITE INTRUSION 



QUARTZ 



The structural features developed in the first four 
cycles are all earlier than the quartz monzonite intru- 
sion, for at different places features of each cycle are 

terminated by the intrusive contact. In some places, 
however, the intrusive rocks are affected by small 
thrust faults, notably east of hill 5675, on the north 




Figcbe 8.— Block diagram showing the generalized structure along the Garrison Monster 

transverse fault. 



side of Rodenhouse Wash, and in a tunnel on the north- 
east side of Ochre Mountain, and these are thought to 
indicate a relatively minor recurrence of the compres- 
sive forces that were so active in the preceding cycles. 

In addition to these faults, there are several other 
faults in or adjacent to the quartz monzonite stock 
that are thought to have a causal relation to it. One 
group of these faults is localized along and is parallel 
to the western border of the intrusion and has caused 
very large displacements in the Ochre Mountain thrust 
plane. Partly because faults of this magnitude do not 
cut the thrust at other localities and partly because 
the zone coincides with a belt of ore deposits that are 
characterized by high-temperature minerals, the fault 
zone is thought to mark the location of the primary 
channel through which the stock was intruded. 

A much larger group of faults is distributed 
throughout the intrusive area. These faults have 
everywhere a small throw, but have very diverse orien- 
tation as well as time relations. They are thought to 



have resulted from the stresses set up at intervals 
during the slow cooling of the stock. 

PROQBBSSrVE VARIATION IN THE CHARACTER 
OF DEFORMATION 

In the summary account of the five cycles in the 
preceding pages, mention was made of an apparent 
dominance in each cycle of certain types of structure. 
Thus the first cycle was characterized by an abun- 
dance of normal faults ; the second by folds, with only 
a minor amount of thrusting and transverse faulting, 
followed by a few normal faults of large throw; the 
third, by predominant thrusting succeeded by minor 
normal faulting; and the fourth, by transverse faults 
accompanied by faults along which the chief movement 
appears to have been horizontal. The fourth cycle 
also appears to have had but little normal faulting. 

Because of the dominance of folding and 
the character of the thrusting in the second 
cycle, it was deduced that the deformation 
proceeded under a moderately heavy load. 
The absence of folding and the abundance 
and character of the thrusts and transverse 
faults in the third and fourth cycles prompt- 
ed the suggestion that the load was con- 
siderably lighter during these times. 

The fact that the load appears to have 
been less in the more recent cycles of def- 
ormation is not in itself surprising, for it 
would appear to be the natural result of a 
progressively greater sum total of erosion 
during a long-continued period of dias- 
trophism. The interesting feature, how- 
ever, is the implication that transverse 
faults, which overshadow in importance 
other structural forms in the fourth cycle, 
have optimum conditions for their forma- 
tion at a time when the overlying cover is 
at a minimum. 
This relation cannot of course be regarded as proved 
from the evidence in the Gold Hill quadrangle. It 
might be considered, for example, that as transverse 
faults were formed in both the second and the third 
cycles their apparent dominance in the fourth cycle is 
not real and is a result of incomplete exposures. 
Furthermore, the change in strike of the transverse 
faults of the fourth cycle, which indicates a change in 
the direction of the causative force, might be taken to 
mean that the conditions accompanying the compres- 
sion also changed in a way to favor transverse faulting 
rather than folding or thrusting. Although neither of 
these objections can be successfully refuted from the evi- 
dence at hand, the relations displayed by some of these 
faults, particularly the Garrison Monster transverse 
fault, suggest strongly that there is a causal relation 
between transverse faulting and a relatively light load. 
The apparent decrease in the amount and intensity 
of normal faulting in the successive cycles cannot be 
readily explained by a progressive decrease in load. A 



GEOLOGIC STBUCTUKE 



61 



widely accepted theory to explain the sequence of fold- 
ing or thrusting followed by normal faulting assumes 
that the normal faults are in the nature of relaxational 
movements to restore equilibrium after excess eom- 
pressional movements that originated through a lack 
of immediate resistance in the earth's crust. Although 
there are some objections to this theory, it appears to 
provide an explanation for the progressive variation in 
the normal faulting. It would appear that during the 
initial period of compression, in the first cycle, the 
crust in this area was notably deficient in its resistance 
to compressive movements in excess of those necessary 
to relieve the stress; on the relief of the compression, 
therefore, a large amount of normal faulting occurred. 
When the compressive forces of the second cycle be- 
came effective, however, the local crust may have 
become sufficiently strengthened or rigid during the 
preceding compression, perhaps by reduction of pore 
space or by recrystallization or some similar process, 
to resist the compressive forces much more effectively, 
and therefore it underwent much less subsequent nor- 
mal faulting. Each successive period of compression 
would thus strengthen the crust, so that in the fourth 
cycle relatively little excess movement occurred during 
compression, and, as a result, practically no normal 
faulting was necessary at the end of the cycle. 

IATI NOBMAI FATXITING AND ITS BEIATION TO THE 
PRESENT TOFOGBAPHY 

In addition to the folds and faults developed during 
the five structural cycles and during the intrusion of the 
quartz monzonite, there are several normal faults that 
are considered to be of relatively recent age, because 
of their topographic relations. In the present section 
these faults, which are shown on plate 3, will be con- 
sidered as a group and their supposed influence on the 
development of the present topography described. 

A feature whose recognition leads to a considerably 
increased knowledge of these late faults is a dissected 
erosion surface that has been partly preserved in 
certain areas in the quadrangle. The surface, judged 
from these remnants, must have been well past matu- 
rity and have approached the condition of a peneplain. 
It is best exposed southeast and southwest of the town 
of Gold Hill (pi. 6, O, D), where it is represented by a 
group of closely spaced hills and ridges, all of which 
have an altitude close to 6,000 feet. The drainage 
pattern of this area is also that of postmaturity, con- 
trasting strongly with the youthful drainage found on 
the west side of Ochre Mountain and in the Deep 
Creek Mountains. 

It seems improbable that a surface such as this 
could have been originally limited to an area as small 
as the present one. Therefore, when remnants of a 
postmature surface in other parts of the quadrangle 
were recognized, they were correlated with this one, 
and the differences in altitude were considered to give 



a measure of the movement along the late normal 
faults that separate these remnants. 

The fault most directly connected with the old 
erosion surface is that along the west sides of Ochre 
Mountain and the Deep Creek Mountains. Although 
there is no direct stratigraphic evidence for it, the con- 
vergence of several kinds of reasoning leaves little 
doubt as to its presence. First of all, the remarkably 
linear boundary between the mountains and the gravel- 
filled vaiey is extremely suggestive of faulting, as it 
transgresses the geologic structure to a notable degree. 
The rock-floored pass on the south side of Ochre 
Mountain through which the Lincoln Highway enters 
the Deep Creek Valley, together with the youthful 
character of the drainage all along the mountain front, 
also implies recent uplift. Additional evidence is pro- 
vided by the fact that the eastern slope of Ochre 
Mountain is a tilted continuation of the old erosion 
surface southeast of the town of Gold Hill. The close 
relationship between the two surfaces is shown by the 
absence of any distinct topographic break between 
them, by the presence on the eastern slope of the 
mountain of a partly entrenched drainage system that 
is approximately equivalent in maturity to that in the 
region near the town, and by the presence of a mod- 
erately deep soil on the ridges of this portion of the 
mountain. This tilted surface on the eastern slope of 
Ochre Mountain (pi. 6, A) contrasts strongly with the 
abrupt western front, with its excellent exposures and 
youthful drainage pattern (pi. 6, B). 

The fault must terminate rather abruptly northward 
about at its intersection with the trail from Gold Hill 
to the Erickson ranch, because to the north the old 
surface continues across the line of the fault unaffected. 
Southward the fault continues for several miles beyond 
the southern border of the quadrangle. The throw 
along the fault cannot be definitely determined. From 
the evidence of tilting on Ochre Mountain it is apparent 
that the block east of the fault must have moved 
upward about 1,500 feet. The block west of the fault 
is covered by gravel, but it must have been depressed 
at least 1,000 feet, as shown by the altitude of the 
gravel. It is rather strongly indicated, therefore, that 
the movement along the fault has been accomplished 
by a combination of elevation in the footwall block and 
depression in the hanging-wall block. 

The fault just described is matched on the east side 
of the mountain area by two major and probably sev- 
eral minor faults of relatively recent age. The more 
southerly of the two major faults is indicated by 
stratigraphic as well as physiographic evidenced This 
is the fault along the eastern front of the Deep Creek 
Mountains south of Overland Canyon. There has 
been a 2,000-foot throw along this fault subsequent to 
the North Pass thrust (seep. 68), which is thought to 
be of relatively recent date. This figure corresponds 
with the difference in altitude between the low hills 



62 



GOLD HILL MINING DISTRICT, UTAH 



east of the fault and the long east-west ridges on each 
side of North Pass Canyon, both of which are consid- 
ered to be remnants of the old erosion surface. 

The surface represented by the low hills east of the 
fault may be continued through Blood Canyon to 
Clifton Flat and thence north to the type area south 
of Gold Hill. The correlation of the east-west ridges 
is less evident. In the first place, the ridge lines on 
both sides of Dry, Sheep, and North Pass Canyons 
reach altitudes on their east ends that are about the 
same as those found throughout the ridge. This, com- 
bined with the youthful, essentially unforked drainage, 
seems to require an original relatively flat surface that 
has been recently uplifted and has undergone relatively 
little erosion except along the master streams. This 
view appears to be confirmed by several areas charac- 
terized by poor exposures, owing to deep weathering 
and slight relief along the ridge lines, as at the head of 
the south fork of Dry Canyon and at the head of Sheep 
Canyon. 

The ridge lines have progressively lower altitudes 
from south to north. The higher areas surrounding 
Uiyabi Canyon continue the trend still farther north- 
ward. The region about the canyon, however, is top- 
ographically the continuation of the east side of Ochre 
Mountain and therefore provides the connecting link 
between the nearly flat but elevated portion of the 
surface to the south with the tilted portion on Ochre 
Mountain. This rather devious attempt to establish 
the topographic throw along the fault would not be 
particularly convincing were it not for the coincidence 
of the topographic displacement with the stratigraphic 
throw at the mouth of the North Pass Canyon. 

The fault has been traced northward to the south 
edge of Clifton Flat. Both the topographic and the 
stratigraphic throws decrease in this direction, but the 
latter cannot be quantitatively evaluated here. The 
fault cannot be recognized on the north side of the flat 
and presumably dies out beneath it. South of the 
quadrangle the fault must continue for many miles 
along the eastern front of the Deep Creek Mountains. 

The southern part of the Deep Creek Mountains as 
included within the quadrangle is thus composed of 
an uplifted block bounded on each side by a depressed 
block. Northward this structure passes into a tilted 
block by the dying out of the eastern boundary fault. 
The uplifted block to the south is, in one sense, a horst. 
Strictly considered, however, it is not, for the two 
faults on its sides are very probably of different ages, 
the eastern fault being the older. This conclusion is 
reached by a consideration of the position of the divide, 
which is more than 3 miles from the eastern fault and 
less than 2 miles from the western fault. On the east 
side, moreover, the range is fronted by the resistant 
Prospect Mountain quartzite. It is therefore rather 
certain that the eastern fault was the earlier, because 
there must have been time for the consequent drainage 



along it to cut back through harder rocks, nearly twice 
the distance that the streams have cut across the 
western fault. 

The second of the two major faults on the east side 
of the mountain area that balance the fault on the 
west side must follow the eastern boundary of the 
quadrangle closely. There is no stratigraphic evidence 
for this fault, but there are two physiographic features 
that seem to require it. One is the linear character 
of the mountain front south of benchmark 4767 on 
the Lincoln Highway, which is continued, south of the 
hilly region, by the line of outcrops in the southeast 
corner of the quadrangle and beyond. The other is a 
deformation of the old erosion surface west of the 
supposed fault. As this is traced southward from 
its exposures around Gold Hill, it is seen to be gradually 
tilted to the west. The tilting must have been accom- 
plished by an elevation of the east side while the west 
side, as represented by the surfaces bordering Clifton 
Flat, remained stationary. The maximum tilt appears 
to have been in the latitude of Montezuma Peak, 
which rises more than 1,000 feet above the undeformed 
surface. The course of Rodenhouse Wash offers strong 
confirmatory evidence for such a tilting. The decrease 
in tilting to the south corresponds to the approximate 
point of termination of the fault south of Overland 
Canyon, which therefore is en echelon with the one 
now being discussed. 

The basinlike depression of Clifton Flat appears to 
have resulted from the movements along the three 
faults just described. The flat is bordered on the east, 
south, and west by high lands ; on the north, however, 
it is continuous with the much dissected old erosion 
surface. Apparently the border faults east of Mon- 
tezuma Peak and west of Ochre Mountain were so far 
apart that the tilting of the surface which accompanied 
the faulting affected only slightly or not at all the 
region now occupied by the depression. 

The old surface to the south was uplifted by means 
of the southern of the two eastern border faults. The 
present outlines of the basin are apparently due to the 
difference in age between the eastern and western 
border faults. The southern of the two eastern faults 
is clearly older than the western one, and, as the north- 
ern fault has en echelon relations with the southern, 
it too is presumably older than the western fault. As 
a result of this earlier faulting, a drainage channel 
appears to have formed extending westward from 
Montezuma Peak. 

With the initiation of movement along the western 
border fault, this drainage channel kept pace with the 
gradual elevation of the block east of the fault by an 
equally rapid excavation of its bed, before the process 
was terminated by the headward erosion of Overland 
Canyon. Before this event happened, however, about 
1,000 feet of rock must have been removed at the site 
of the present pass through which the Lincoln Highway 



GEOLOGIC STBTJCTTJBB 



63 



descends into the valley of Deep Creek. The net re- 
sult was to give the depression its present roughly 
triangular shape rather than the linear shape with 
northward drainage that it would have possessed if 
the three faults had been exactly contemporaneous. 

The recent normal faulting in the northern third 
of the quadrangle is entirely distinct from that just 
described. This is indicated by the presence in the 
latitude of the Gold Hill town site of remnants of the 
old surface at accordant altitudes from the eastern 
border of the quadrangle almost to the western bor- 
der. North of this zone several of these faults have 
been recognized. 

Movement along the most easterly fault of the 
northern group shown on plate 3 is thought to be the 
cause of the present altitude of Dutch Mountain. 
This fault is wholly concealed by alluvium, and the 
chief evidence of its presence, aside from the drainage 
pattern along the east side of the mountain, is the dif- 
ference of nearly 2,000 feet in altitude that separates 
the old erosion surface around the town of Gold Hill 
from the summit of Dutch Mountain. The consid- 
erable dissection of the east side of Dutch Mountain 
suggests that the fault must be somewhat older than 
that on the east side of the Deep Creek Mountains, 
which also has the Prospect Mountain quartzite on 
the uplifted side. 

The two faults on the west side of Dutch Mountain 
can be shown with more certainty. The more west- 
erly, along the western base of the mountain, bends 
from a southeasterly to an easterly course and appears 
to coincide with an older transverse fault. Remnants 
of the old erosion surface are preserved on the ridges 
east of the fault, and their altitude as compared with 
the altitude of similar remnants on the hanging-wall 
side of the fault near its south end indicate that the east 
side has been elevated about 500 feet. 

The eastern fault represents renewed movement 
along a portion of the Trail Gulch fault. Several 
bits of evidence testify to its presence — the topographic 
discordance, its influence upon the drainage pattern, 
and the high-level gravel immediately west of the 
fault. The displacement along the fault cannot be 
exactly determined, because the position of the old 
erosion surface in the uplifted block cannot be deter- 
mined, but the throw must be at least 800 feet. 

The fault in the northwestern part of the quadrangle 
is also thought to follow a line of older faulting. The 
total throw of tMs fault as determined stratigraphically 
is much too great to account for the present distribu- 
tion of the White Sage formation, and it is suggested 
that there has been renewed movement whose magni- 
tude may be estimated from the topography on each 
side as from 600 to 800 feet. This suggestion is based 
on the presence, west of the fault, of a postmature 
erosion surface at an altitude of about 5,600 feet, in 



which Deep Creek and its tributaries are entrenched. 
East of the fault the country is considerably dissected, 
but there appears to be no topographic break between 
it and the type area of the old surface around Gold 
Hill. Several of the summits near the fault reach an 
altitude of 6,200 feet, however, and it is thought that, 
in addition to the required depression of about 400 
feet west of the fault, there must have been an eleva- 
tion of at least 200 feet in the block east of it. The 
sum of these two agrees fairly well with the figures 
indicated by the observed distribution of the White 
Sage formation, 

Gilbert u has described even more recent normal 
faulting in the Lake Bonneville beds on the east side 
of the range. This locality was not examined by the 
writer, and the extent of the faulting of this age is not 
known. 

The relatively recent normal faulting shown in the 
Gold Hill quadrangle is not as spectacular as that in 
many other regions in the Great Basin, but the me- 
chanics of the process is seemingly well illustrated. 
The characteristics of the faulting in this quadrangle 
may be summarized as follows: 

1. The faults are by no means contemporaneous. 

2. They exhibit a strong tendency to utilize earlier fault lines. 

3. Displacements along them were accomplished by move- 
ments of both the hanging-wall and footwall blocks. 

4. Both elevation and depression appear to have been accom- 
plished by tilting of the affected blocks. At relatively short 
distances away from the fault the tilt is no longer discernible. 

5. They were initiated after a long period of stability, during 
which the surface was reduced to a state of postmaturity. 

6. The faults may terminate abruptly. 

7. En Echelon relations among the faults are found. 

8. Both curving and straight faults were formed. 

9. Apparent horsts, and presumably also graben, may result 
from two faults of somewhat different ages. 

10. The faults have no obvious relation to the igneous rocks 
exposed within the quadrangle, being much younger than the 
intrusive quartz monzonite and older than the volcanic rocks. 

During the field work scant attention was given to 
the minor topographic changes that followed the 
normal faulting of this age. Casual observations indi- 
cated, however, that the quadrangle contains a wealth 
of material bearing upon the postfault history, and 
that detailed work would produce a great deal of 
information concerning the climatic changes that have 
occurred not only since Lake Bonneville time but also 
in the earlier stages of the lake. 

AOE OF THE STBTJCTTJIAI FEATURES 

The age of the faults and folds formed. during the 
five structural cycles can best be determined by their 
relations to the Lower Triassic limestone, the Eocene 
(?) White Sage formation, and the quartz monzonite 
stock, which was probably intruded in late Eocene or 



» Gilbert, O. K., Lake Bonneville: U.S. Oeol. Survey Mob. 1, p. 383, 1890. 



64 



GOIJD HILL MINING DISTRICT, UTAH 



early Oligocene time (p. 48). All the cycles are younger 
than the Triassic, as the Triassic limestone is a unit of 
the nearly conformable stratigraphic column affected 
by the structural disturbances. 

The first and second cycles are older than the White 
Sage formation, as the beds of this formation uncon- 
formably overlie both the recumbent anticline that was 
formed in the first stage of the second cycle and the 
normal faults that were active in the second stage. As 
there are no recorded periods of orogeny during early 
Mesozoie time in the eastern Great Basin, the struc- 
tural features of the first and second cycles may be 
tentatively classed as of Cretaceous or early Eocene age. 

Normal faults that are considered to belong in the 
second stage of the third cycle cut the White Sage 
formation at several places in the northwestern part 
of the quadrangle, and in at least one locality (p. 43) 
there are considerable discordances in dip between beds 
within the formation. These features are thought to 
indicate that the formation was deposited during the 
final stages of the compression that caused the first 
stage of the third cycle, and the faults and fo'ds of 
this cycle are considered to be of Eocene age. 

The structural features of the fourth cycle are 
younger than the White Sage formation but are cut 
off by the quartz monzonite intrusion and must there- 
fore date from late Eocene or early Oligocene time. 
The similarity in strike of the transverse faults of this 
cycle to the minor transverse faults of the fifth cycle, 
which cut the intrusive, suggests that the time interval 
between these two cycles was small. 

In a recent review of the thrust faults previously 
described in the northern Rocky Mountains, Mans- 
field IS notes that "these faults were in all probability 
not synchronous but some occurred later than others. 
This fact indicates that the compressive stresses that 
produced the overthrusts were maintained over a con- 
siderable period and that they found relief at more or 
» less distinct successive intervals — a conclusion that 
should naturally be expected in view of the greatness 
of the region affected and of the tremendous stresses 
involved." 

The Gold Hill quadrangle appears to be unique 
among those so far mapped in that it exhibits several 
of the successive thrusts. The reason for such a local- 
ization of thrusts of different ages in one area instead 
of the ideal sequence of successively younger thrusts 
from west to east postulated by Thorn, 16 is not clear. 
In contrast to other regions of thrusting, Gold Hill is 
not at or particularly near the limits of earlier sedi- 
mentation, and therefore the localization of thrusts 

'» ManBfleld, Q. H., Geography, geology, and mineral resources of part of south- 
eastern Idaho; U.S. Qeol. Survey Prof. Paper 182, p. 388, 1927. 

'• Thorn, W. T., Jr., The relation of deep-seated faults to the surface structural 
features of central Montana: Am. Assoc. Petroleum Geologists Ball., vol, 7, pp. 1-13, 
1923. 



within the quadrangle cannot be ascribed to the influ- 
ence of "initial dip," as has been done in other 
areas. A possible explanation of this sort might be 
considered to lie in the presence immediately to the 
east of Schuchert's positive area, "Utah." 17 

The writer, however, is more inclined to regard the 
thick Pennsylvania^ sedimentary prism in the Oquirrh 
Mountains 1S as the most important factor. Bocks of 
this age are so much thinner within short distances 
both to the east and west that there must have been 
a marked original depositional syncline. Initiation of 
compression from the west would tend to increase the 
synclinal fold and permit overriding by the thinner 
sedimentary column to the west. Successive periods 
of compression would only accentuate the syncline, 
and thrusting would thus be localized in the zone 
immediately to the west. 

The age of the relatively recent normal faulting can- 
not be definitely fixed. Gilluly 19 has recently sum- 
marized the evidence at hand regarding the age of 
faulting of this type in the Great Basin region. He 
notes that the initiation of faulting appears to differ 
in different regions. He concludes that in the Oquirrh 
Bange the faults now expressed by the present topog- 
raphy probably became active at some time between 
the Oligocene and the upper Pliocene. In the Gold 
Hill quadrangle the direct evidence consists in the 
observations that the faulting is younger than a mature 
erosion surface developed upon both the sedimentary 
rocks and the quartz monzonite and is older than the 
volcanic rocks and is also probably older than the 
Pliocene (?) sediments. As the age of the Pliocene (?) 
formation is purely speculative, it has no immediate 
bearing upon the age of the faulting. The writer pre- 
fers the younger of the two ages set by Gilluly for the 
inception of the Gold Hill faulting, because of the fact 
that time must be allowed for the exposure of the late 
Eocene or post-Eocene quartz monzonite by erosion 
and the development upon it of a mature erosion 
surface. 

IOCAI DESCRIPTIONS 

To facilitate the description of individual features, 
the quadrangle has been divided into six structural 
blocks. The extent of these blocks is indicated on 
plate 3, where it may be seen that the dividing lines 
between blocks, except those outlining the quartz 
monzonite, are major structural features. The ac- 
companying correlation table summarizes the struc- 
tural history of each of the blocks and indicates the 
contemporaneous features. 

« Sehuchert, Charles, Paleogeography of North America: Qeol. Soc. America 
Bull., vol. 20, p. 474, 1910. 

" Gilluly, James, Geology and ore deposits of the Stockton and Fairfield quad- 
rangles, Utah: U.S. Geol, Survey Prof. Paper 178, pp. 34-38, 1932. 

"Gilluly, James, Basin Kange faulting along the Oquirrh Range, Utah: Qeol. 
Soc. America Bull., vol. 89, pp. 1118-1120, 1828. 



U.S. GEOLOGICAL SURVEY 



PROFESSIONAL PAPEIl 177 PLATE 6 





A. EAST SLOPE OF OCHRE MOUNTAIN. 



B. DISSECTION ON WKST SLOPE OF OCHRE MOUNTAIN. 




C. DISSECTED POSTMATURE EROSION SURFACE. 
Looking southeast from a point near U.S. locating monument H. 




D. DISSECTED POSTMATURE EROSION SURFACE. 

Looking east from a point near tbe Yellow Hammer mine. 



All photographs by F. A. Melton. 



U.S. GEOLOGICAL 8UKVEY 



PROFESSIONAL PAFEK 177 PLATE 7 




A. CRUMPLING BENEATH NEARLY FLAT FAULT ON WEST SIDE OF OCHRE MOUNTAIN. 



B. PLUNGING MINOR ANTICLINE IN THE MANNING CANYON FORMATION. 





C. VARIABLE DIP OF FAULT BETWEEN THE MADISON LIMESTONE AND THE WOODMAN 

FORMATION IN ACCIDENT CANYON. 



0. MINOR THRUST IN THE WOODMAN FORMATION NORTH OF THE GARRISON 
MONSTER NEW CAMP. 









Correlation of at 


ntctural features in Gold Hill quadrangle 






Cyele and stage 


Deep Creek Mountain block 


TJlyabi Canyon block 


Ochre Mountain block 


Dutch Mountain block 


Northwestern block 


Quartz monzonite block 


First. 


First stage. 


Not represented? 


Not represented? 


Minor thrusts and 
folds. 


Not represented? 


Not represented? 




Second stage. 


Not represented? 


Tilted fault in 

Uiyabi Canyon? 


Normal faulting. 
Abundant. 


North-south normal 
faults. 


Not represented? 




Second. 


First stage. 


Major anticline. 

West-northwest 
transverse faulting. 


Major anticline. 

West-northwest 
transverse fault- 
ing. 


Major folding? 
Transverse faulting. 


Major folding. 

Dutch Mountain 
thrust and minor 
thrusts. 


Recumbent anticline 
and other folds. 




Second stage. 


Normal faulting. 
Early movement on 
eastern border fault. 


Normal faulting. 


Normal faulting. 


Normal faulting. 
Trail Gulch fault and 
northwest faults. 


Trail Gulch and Bar 
Creek normal faults. 




Third. 


First stage. 


North Pass thrust 
and subsidiary 
thrusts. 

West-northwest trans- 
verse faulting. 


North Pass thrust. 


Transverse faulting. 

Ochre Mountain 
thrust and sub- 
sidiary thrusts. 


Pool Canyon trans- 
verse fault. 

Ochre Mountain thrust 
and subsidiary 
thrusts. 

Reversal of movement 
on Trail Gulch fault. 


Minor thrusts? 

Warping of axial plane 
of recumbent anti- 
cline? 




Second stage. 


Normal faulting. 

Northeasterly fault 
on Blood Moun- 
tain. 


Normal faulting east 
of benchmark 
5868. 


Normal faulting, es- 
pecially along old- 
er faults. .■ 


Normal faulting rare. 


Normal faulting of 
northerly strike? 




Fourth. 


First stage. 


East- west Blood Can- 
yon and Dry Can- 
yon faults. 

Mmor thrusts and 
reverse faults. 


Blood Canyon trans- 
verse fault. 

Minor reserve faults. 
Warping of North 
Pass thrust. 


East-west transverse 
faults. 

East northeast faults. 


Garrison Monster trans- 
verse fault and re- 
lated conjugate fault- 
ing. 


Conjugate faults. 


, 


Second stage. 


Not represented? 


Not represented? 


Not represented? 


Small normal faults? 


Not represented? 




Fifth cycle and faulting 
related to the quartz 
monzonite. 


Not represented? 


Not represented? 


Faults related to the 
quartz monzonite. 


Not represented? 


Not represented? 


Normal faults re- 
lated to intrusion. 

East-west transverse 
faults and minor 
thrusts. 

Small faults related 
to cooling of intru- 
sive. 


Late normal faulting. 


East and west border 
faults. 


East and west border 
faults. 


West border fault. 


Normal faulting in part 
along older faults. 


Renewed movement 
along north-south 
fault. 





o 
m 

g 

o 



O 






M 



Oft 
Of 



66 



GOLD HIM, MINING DISTRICT, UTAH 



Evidence for the separation of the* structural history 
into five epochs is given in the following pages. It is 
far from being as conclusive as might be desired, and 
future more detailed study may result either in the 
elimination of some of the five epochs or in the addition 
of others. Some of the structural features could not be 
definitely assigned to specific epochs, because their 
relations to features of known age could not be deter- 
mined, and on plate 3 it was necessary to correlate 
them on the basis of their similarities to features for 
which more definite information was available. The 
difficulty of correlation is increased by the evidence of 
recurrent movements along some of the faults and by 
the impression that such movements may have been 
widespread; however, in spite of the uncertainties 
regarding individual features and the exact correlation 
of structural epochs, it is clear that deformation in this 
region has taken place in recurrent cycles and has 
continued over a long period of time. 

DBBP CBBEK MOTOSTTAIN BLOCK 

The Deep Creek Mountain block includes that portion of the 
quadrangle south of the Blood Canyon transverse fault and thus 
includes the southern extension of the Clifton Hills as well as 
the Deep Creek Mountains. 

The structure in this block is simpler than in any other part 
of the quadrangle. The pre-Carboniferous beds make up the 
westward-dipping limb of an anticline formed during the second 
structural cycle and bounded both on the east and west by* recent 
normal faults. The continuity of the beds is broken by three 
rather large transverse faults of different ages, in addition to 
the one that limits the block on the north. Several minor 
normal and transverse faults and several small thrust faults 
have been recognized. Section P-P' on plate 1 illustrates the 
monoclinal character and shows two of the minor thrust faults. 
Near the northern boundary fault simplicity of structure is 
replaced by complexity, and several thrust plates that underlie 
the North Pass thrust may be recognized. These features are 
illustrated in the eastern part of section J-J'-J". Overturning 
along low-angle transverse faults is found in the Carboniferous 
area to the northeast (sec. H-H'). 

Dry Canyon tramverse fault. — The southernmost transverse 
fault follows more or less closely the course of Dry Canyon on 
the east side of the mountains and Siraonson Canyon on the 
west side. Its dip was not measured directly, but subsidiary 
parallel fractures dip 80°-85° N. The fault is poorly exposed 
throughout its extent. Where it cuts through shale and thin- 
bedded limestone the fault plane is covered by talus, and in 
its course through the more resistant dolomite and quartzite 
these rocks are so shattered, bleached, and reerystallized that 
in most places it is impossible to recognize the actual fault con- 
tact. The bleaching and recrystallization are probably in part, 
at least, the result of igneous metamorphism, for a small body 
of a sheared intrusive igneous rock was found along the fault 
just west of the spring near the mouth of Dry Canyon. The 
apparent displacement is somewhat variable, because of varia- 
tions in dip on the two sides of the fault. The presence of 
thrust faults on both sides and the character of the drag shown 
on the south side of the fault on the divide render it probable 
that the greater part of the displacement was horizontal, the 
north side moving toward the east. The amount of horizontal 
movement was close to 1,000 feet. Outcrops west of the ridge 
line are offset more than twice this distance, owing to the com- 
bination of west dips and the steep slope. 



Minor faults south of Dry Canyon transverse fault. — In the 
prospect tunnel south of the mouth of Dry Canyon a fault zone 
is exposed that strikes nearly north and dips 65°-90° W. Pros- 
pect Mountain quartzite forms both walls, but on the east the 
quartzite dip3 to the east at moderately high angles, and on the 
west it is slightly inclined to the west. The fault has normal 
relations, aa the thickness of the eastward-dipping quartzite 
is in excess of that exposed to the west. There is a parallel 
shear zone about 100 yards to the west. 

Half a mile west of these normal faults there are two rather 
similar faults that strike west of north and dip to the east. The 
eastern one strikes N. 16° W, and dips 50° E. It drops the upper 
contact of the Prospect Mountain quartzite about 75 feet. The 
throw decreases northward along the two branches of the fault 
in the gulch south of Willow Spring. The Dry Canyon fault 
is offset by both branches. The western fault has about the 
same strike and dip, but its displacement is considerably greater, 
probably being more than 400 feet where it crosses the ridge. 
This fault also offsets the Dry Canyon fault, but north of the in- 
tersection the normal fault can be recognized for only a short dis- 
tance, beyond which the beds of the Busby quartzite are sharply 
warped, the more easterly outcrops being thus relatively depressed. 

There must be additional faulting on the Cabin shale in this 
region, for exposures of the formation not affected by either of 
the two normal faults are only 100 feet or less in thickness. 
Locally also the bedding strikes at right angles to the underlying 
quartzite. These features are thought to indicate the presence 
within the shale of a low-angle fault, which is probably related 
to the transverse fault. 

A minor fault in the southern branch of North Pass Canyon 
is indicated by a displacement of 200 to 300 feet of the outcrops 
of the resistant Lamb and Hicks dolomites. It was probably 
formed at the same time as the large transverse fault in Dry 
Canyon, but it could not be traced into that fault through the 
poorly exposed beds of the Abercrombie formation. Subsidiary 
fractures parallel to it strike N. 70° E. and dip 75° S. This is 
probably the strike and dip of the fault itself, but the fault 
plane was not exposed. 

Two other faults were found south of the main transverse 
fault. These are on the west side of the range, in the southern 
branch of Simonson Canyon. The easterly fault strikes about 
N. 45° W. and dips steeply to the southwest. It brings various 
beds of the Laketown dolomite into contact with the Fish Haven 
dolomite and the Chokecherry dolomite. The western fault 
brings the Sevy dolomite into contact with the Laketown dolo- 
mite. The two faults are exposed for only a short distance 
within the quadrangle. Their continuation to the north is cov- 
ered by the gravel in the canyon bottom, but they must be cut 
off by the Dry Canyon fault. 

Sevy Canyon transverse fault. — The transverse fault in Sevy 
Canyon has a west-northwesterly strike, in distinction to the 
nearly east-west strike of the Dry Canyon fault to the south. 
As a result the two are only a mile apart on the east side of the 
range and over 2 miles apart on the west side. The Sevy 
Canyon fault has a pronounced northerly dip over much of its 
course, as may be seen on the steep slopes on the south side of 
North Pass Canyon. Parallel fractures dip 60° NNE. The 
drag shown by thinner-bedded formations cut by the fault, 
especially the Cabin shale, and the distribution of fragments in 
shatter zones indicate that the movement was chiefly horizon- 
tal, the south side moving relatively to the east. The offset- 
ting of formations along the fault increases rather regularly 
westward. Thus outcrops of the Cabin shale are shifted about 
600 feet, the Young Peak dolomite about 1,200 feet, the Fish 
Haven dolomite about 2,000 feet, and the Guilmettu formation 
about 4,000 feet. This variation is in part the result of sub- 
sidiary thrust faults and in part the result of a steepening in 
the westward dip of the bedding on the south side of the fault 









Correlation of structural features in Gold Hill quadrangle 






Cycle and stage 


Deep Creek Mountain Mock 


tiiynbl Canyon block 


Ochre Mountain block 


Dutch Mountain block 


Northwestern block 


Quartz monzonite block 


First. 


First stage. 


Not represented? 


Not represented? 


Minor thrusts and 
folds. 


Not represented? 


Not represented? 




Second stage. 


Not represented? 


Tilted fault in 
Uiyabi Canyon? 


Normal faulting. 
Abundant. 


North-south normal 
faults. 


Not represented? 




Second. 


First stage. 


Major anticline. 

West-northwest 
transverse faulting. 


Major anticline. 

West-northwest 
transverse fault- 
ing. 


Major folding? 
Transverse faulting. 


Major folding. 

Dutch Mountain 
thrust and minor 
thrusts. 


Recumbent anticline 
and other folds. 




Second stage. 


Normal faulting. 
Early movement on 
eastern border fault. 


Normal faulting. 


Normal faulting. 


Normal faulting. 
Trail Gulch fault and 
northwest faults. 


Trail Gulch and Bar 
Creek normal faults. 




Third. 


First stage. 


North Pass thrust 
and subsidiary 

thrusts. 

West-northwest trans- 
verse faulting. 


North Pass thrust. 


Transverse faulting. 

Ochre Mountain 

thrust and sub- 
sidiary thrusts. 


Pool Canyon trans- 
verse fault. 

Ochre Mountain thrust 
and subsidiary 
thrusts. 

Reversal of movement 
on Trail Gulch fault. 


Minor thrusts? 

Warping of axial plane 
of recumbent anti- 
cline? 




Second stage. 
First stage. 


Normal faulting. 

Northeasterly fault 
on Blood Moun- 
tain. 


Normal faulting east 
of benchmark 

5868. 


Normal faulting, es- 
pecially along old- 
er faults. , 


Normal faulting rare. 


Normal faulting of 
northerly strike? 




Fourth. 


East-west Blood Can- 
yon and Dry Can- 
yon faults. 

Minor thrusts and 
reverse faults. 


Blood Canyon trans- 
verse fault. 

Minor reserve faults. 
Warping of North 

Pass thrust. 


East-west transverse 
faults. 

East northeast faults. 


Garrison Monster trans- 
verse fault and re- 
lated conjugate fault- 
ing. 


Conjugate faults. 


. 


Second stage. 


Not represented? 


Not represented? 


Not represented? 


Small normal faults? 


Not represented? 




Fifth cycle and faulting 
related to the quartz 
monzonite. 


Not represented? 


Not represented? 


Faults related to the 
quartz monzonite. 


Not represented? 


Not represented? 


Normal faults re- 
lated to intrusion. 

East-west transverse 
faults and minor 
thrusts. 

Small faults related 
to cooling of intru- 
sive. 


Late normal faulting. 


East and west border 
faults. 


East and west border 
faults. 


West border fault. 


Normal faulting in part 
along older faults. 


Renewed movement 
along north-south 

fault. 





© 

O 

r 1 
o 

s 

Q 



Q 

►3 



a 



OS 



66 



GOLD HILL MINING DISTRICT, UTAH 



Evidence for the separation of thff structural history 
into five epochs is given in the following pages. It is 
far from being as conclusive as might be desired, and 
future more detailed study may result either in the 
elimination of some of the five epochs or in the addition 
of others. Some of the structural features could not be 
definitely assigned to specific epochs, because their 
relations to features of known age could not be deter- 
mined, and on plate 3 it was necessary to correlate 
them on the basis of their similarities to features for 
which more definite information was available. The 
difficulty of correlation is increased by the evidence of 
recurrent movements along some of the faults and by 
the impression that such movements may have been 
widespread; however, in spite of the uncertainties 
regarding individual features and the exact correlation 
of structural epochs, it is clear that deformation in this 
region has taken place in recurrent cycles and has 
continued over a long period of time. 

DEEP CREEK MOUNTAIN BLOCK 

The Deep Creek Mountain block includes that portion of the 
quadrangle south of the Blood Canyon transverse fault and thus 
includes the southern extension of the Clifton Hills as well as 
the Deep Creek Mountains. 

The structure in this block is simpler than in any other part 
of the quadrangle. The pre-Carboniferous beds make up the 
westward-dipping limb of an anticline formed during the second 
structural cycle and bounded both on the east and west by recent 
normal faults. The continuity of the beds is broken by three 
rather large transverse faults of different ages, in addition to 
the one that limits the block on the north. Several minor 
normal and transverse faults and several small thrust faults 
have been recognized. Section P-P' on plate 1 illustrates the 
monoelinal character and shows two of the minor thrust faults. 
Near the northern boundary fault simplicity of structure is 
replaced by complexity, and several thrust plates that underlie 
the North Pass thrust may be recognized. These features are 
illustrated in the eastern part of section J-J'-J*. Overturning 
along low-angle transverse faults is found in the Carboniferous 
area to the northeast (sec. H-H'). 

Dry Canyon transverse fault. — The southernmost transverse 
fault follows more or less closely the course of Dry Canyon on 
the east side of the mountains and Simonson Canyon on the 
west side. Its dip was not measured directly, but subsidiary 
parallel fractures dip 80°-85° N. The fault is poorly exposed 
throughout its extent. Where it cuts through shale and thin- 
bedded limestone the fault plane is covered by talus, and in 
its course through the more resistant dolomite and quartzite 
these rocks are so shattered, bleached, and recrystallized that 
in most places it is impossible to recognize the actual fault con- 
tact. The bleaching and recrystallization are probably in part, 
at least, the result of igneous metamorphism, for a small body 
of a sheared intrusive igneous rock was found along the fault 
just west of the spring near the mouth of Dry Canyon. The 
apparent displacement is somewhat variable, because of varia- 
tions in dip on the two sides of the fault. The presence of 
thrust faults on both sides and the character of the drag shown 
on the south side of the fault on the divide render it probable 
that the greater part of the displacement was horizontal, the 
north side moving toward the east. The amount of horizontal 
movement was close to 1,000 feet. Outcrops west of the ridge 
line are offset more than twice this distance, owing to the com- 
bination of west dips and the steep slope. 



Minor faults south of Dry Canyon transverse fault.— In the 
prospect tunnel south of the mouth of Dry Canyon a fault zone 
is exposed that strikes nearly north and dips 65 -9u W. Pros- 
pect Mountain quartzite forms both walls, but on the east the 
quartzite dips to the east at moderately high angles, and on the 
west it is slightly inclined to the west. The fault has normal 
relations, as the thickness of the eastward-dipping quartzite 
is in excess of that exposed to the west. There is a parallel 
shear zone about 100 yards to the west. 

Half a mile west of these normal faults there are two rather 
similar faults that strike west of north and dip to the east. The 
eastern one strikes N. 16° W. and dips 50° B. It drops the upper 
contact of the Prospect Mountain quartzite about 75 feet. The 
throw decreases northward along the two branches of the fault 
in the gulch south of Willow Spring. The Dry Canyon fault 
is offset by both branches. The western fault has about the 
same strike and dip, but its displacement is considerably greater, 
probably being more than 400 feet where it crosses the ridge. 
This fault also offsets the Dry Canyon fault, but north of the in- 
tersection the normal fault can be recognized for only a short dis- 
tance, beyond which the beds of the Busby quartzite are sharply 
warped, the more easterly outcrops being thus relatively depressed. 

There must be additional faulting on the Cabin shale in this 
region, for exposures of the formation not affected by either of 
the two normal faults are only 100 feet or less in thickness. 
Locally also the bedding strikes at right angles to the underlying 
quartzite. These features are thought to indicate the presence 
within the shale of a low-angle fault, which is probably related 
to the transverse fault. 

A minor fault in the southern branch of North Pass Canyon 
is indicated by a displacement of 200 to 300 feet of the outcrops 
of the resistant Lamb and Hicks dolomites. It was probably 
formed at the same time as the large transverse fault in Dry 
Canyon, but it could not be traced into that fault through the 
poorly exposed beds of the Abercrombie formation.' Subsidiary 
fractures parallel to it strike N. 70° E. and dip 75° S. This is 
probably the strike and dip of the fault itself, but the fault 
plane was not exposed. 

Two other faults were found south of the main transverse 
fault. These are on the west side of the range, in the southern 
branch of Simonson Canyon. The easterly fault strikes about 
N. 45° W. and dips steeply to the southwest. It brings various 
beds of the Laketown dolomite into eon tact with the Fish Haven 
dolomite and the Chokecherry dolomite. The western fault 
brings the Sevy dolomite into contact with the Laketown dolo- 
mite. The two faults are exposed for only a short distance 
within the quadrangle. Their continuation to the north is cov- 
ered by the gravel in the canyon bottom, but they must be cut 
off by the Dry Canyon fault. 

Sevy Canyon transverse fault. — The transverse fault in Sevy 
Canyon has a west-northwesterly strike, in distinction to the 
nearly east-west strike of the Dry Canyon fault to the south. 
As a result the two are only a mile apart on the east side of the 
range and over 2 miles apart on the west side. The Sevy 
Canyon fault has a pronounced northerly dip over much of its 
course, as may be seen on the steep slopes on the south side of 
North Pass Canyon. Parallel fractures dip 60° NNB. The 
drag shown by thinner-bedded formations cut by the fault, 
especially the Cabin shale, and the distribution of fragments in 
shatter zones indicate that the movement was chiefly horizon- 
tal, the south side moving relatively to the east. The offset- 
ting of formations along the fault increases rather regularly 
westward. Thus outcrops of the Cabin shale are shifted about 
600 feet, the Young Peak dolomite about 1,200 feet, the Fish 
Haven dolomite about 2,000 feet, and the Guilmettu formation 
about 4,000 feet. This variation is in part the result of sub- 
sidiary thrust faults and in part the result of a steepening in 
the westward dip of the bedding on the south side of the fault 



GEOLOGIC STBTJCTOTE 



67 



but not on the north side. A minor fault of similar strike 
occurs a short distance to the north and was probably formed 
at the same time. 

Relation of Sevy Canyon fault to Dry Canyon fault,— The age 
of the Sevy Canyon fault relative to the Dry Canyon fault is 
not obvious. It is probable that the northwestward-striking 
Sevy Canyon fault is the older, for faults of similar strike 
apparently terminate against the east-west Dry Canyon fault 
and against the parallel Blood Canyon fault, to the north. 
Contemporaneity of the two faults cannot be disproved, how- 
ever, as the contact between them is not exposed, but, inasmuch 
as crumpling in the rocks between the two faults to the east 
might be expected if they were of the same age, the absence of 
crumpling suggests that the Sevy Canyon fault is of similar age 
to the other northwesterly transverse faults. 

Minor faults between the Dry Canyon and Sevy Canyon faults. — 
On the ridge between Dry Canyon and Sheep Canyon the 
Abercrpmbie formation is 700 feet thinner than on the ridges to 
the north or south. A zone of disturbed strikes and dips in the 
saddle west of peak 7423 on this ridge Is thought to be the site 
of the fault movement. The beds are thought to have been 
out out by overriding rather than by normal faulting, because 
the beds east of the pass dip more steeply (40°-5Q° W.) than 
normal, whereas those to the west dip less steeply (25°-30° W.) . 
Such drag effects are not characteristic of normal faulting but 
may be the result of thrust faulting. The fault was not traced 
to the north or south because of poor exposures on the hillsides, 
but it must die out to the north, for on the ridge north of Sheep 
Canyon the Abeicrombie formation has its normal thickness. 
It probably terminates southward against the Dry Canyon fault. 
This inferred thrust fault is shown on section P-P', plate 1. 

The northwesterly fault that is cut off by the Dry Canyon 
fault near the head of Dry Canyon is traceable with difficulty, 
because of shattering and reerystallization for some distance from 
the main fault. Its presence is required by an offset in the out- 
crop of a characteristic bed near the top of the Choke-cherry dolo- 
mite. It is apparently terminated on the west by a thrust fault 
exposed on the divide. The thrust fault strikes about north and 
dips rather steeply to the west. It has caused beds near the mid- 
dle of the Laketown dolomite to override the lower beds of the Sevy 
dolomite, involving a repetition of about 600 feet stratigraphieally. 
(See sec. P-P'.} Toward the north, the strike of the thrust changes 
to northwest, the dip steepens and inclines to the southwest, and 
the fault is indistinguishable from other minor transverse faults. 

A somewhat similar thrust fault is found about a mile to the 
north, on the south slope of peak 8291. Here, however, the 
thrust has not caused a duplication of strata but has eliminated 
more than half of the normal thickness of the Laketown dolo- 
mite. The line of the fault is marked by a zone of crushed 
dolomite and poor exposures near the base of the formation. 
The fault must die out to the south, for it was not recognized 
south of the head of the canyon, where the Laketown dolomite 
has its full thickness. To the north the strike swings to the 
northwest, the dip steepens, and the apparent displacement 
increases, as Sevy dolomite and Simonson dolomite south of 
the fault are successively brought, into contact with beds of 
Laketown dolomite north of the fault. At an altitude of about 
7,000 feet in Sevy Canyon this fault meets the Sevy Canyon 
fault. The increased apparent displacement is probably an 
actual increase, because overriding by massive beds in the 
Simonson dolomite may be observed in the region where the 
fault changes its strike to northwest. 

Blood Canyon transverse fault. — The transverse fault in Blood 
Canyon, which limits the Deep Creek Mountain block to the 
north, has a rather sinuous course, which averages close to east- 
west and thus makes an angle of about 25° with the older north- 
westerly transverse faults. Its dip is also variable. West of 
Blood Canyon it is steep either to the north or south, but to the 
east the fault has a moderately low south dip. East of Over- 



land Canyon the fault cuts through an area in which metamor- 
phism has partly or completely concealed many of the minor 
structural features connected with the fault. Adjacent to the 
more easterly mile of exposure of the fault the Oquirrh formation 
to the south is complexly folded on a small scale, although away 
from the fault the formation has a rather uniform eastward dip. 

Structure in Sevy Canyon south of the Blood Canyon fault. — 
The most striking structural feature in this region is the pro- 
nounced northeasterly strike of the formations near the Blood 
Canyon fault. Very little crumpling or folding is observed in 
the beds except on the extreme western flank of the range, 
where beds of the Guilmette formation are compressed into 
several small close folds. Beds on each side of the Blood Can- 
yon fault are badly shattered, and in most places the fault 
cannot be exactly located, but where it forms the northern 
boundary of the large outcrop of the Woodman formation a 
thick breccia zone is exposed, dipping almost vertically. 

North Pass transverse fault. — The North Pass transverse 
fault, striking northwest, terminates the linear outcrops of 
Prospect Mountain quartzite, Cabin shale, and Busby quartzite 
that extend to the south boundary of the quadrangle. North 
of the fault are exposed Middle and Upper Cambrian formations 
that are folded into a plunging anticline. Westward along the 
fault the Young Peak dolomite and Trippe limestone are but 
little offset. This portion of the fault, therefore, marks a rather 
local line of differential movement, the beds south of the fault 
showing a more or less uniform westward dip, and those to th e 
north being folded to form an anticline. The westward con- 
tinuation of the North Pass -fault again shows a considerable 
displacement, as the fault in this region marks the southern 
limit of a number of thin overthrust plates. The fault is cut 
off to the northwest by the Blood Canyon fault. It may be 
traced beneath gravel some distance to the east, however, by 
reason of the isolated outcrops east of the main range. 

Major anticline along east front of range. — The plunging anti- 
cline in North Pass Canyon that is terminated southward by 
the transverse fault is thought to be a continuation of a major 
anticline whose axis appears to be nearly coincident with the 
eastern front of the range. The axis is covered by gravel in 
most places, but eastward dips in the Prospect Mountain quartz- 
ite south of Dry Canyon and nearly horizontal bedding in a 
down-faulted exposure of higher Cambrian beds half a mile 
north of the mouth of Sheep Canyon allow it to be located 
with moderate accuracy. 

If the two anticlines are the same, their present positions 
imply that the south side of the eastern segment of the North 
Pass transverse fault has moved relatively eastward and upward. 

Thrust plates on the north side of North Past Canyon. — The 
anticline in North Pass Canyon has affected only the Middle 
Cambrian portion of the section. The Upper Cambrian Lamb 
dolomite is not folded but extends across the anticlinal axis 
without regard for the underlying structure. ' The lower contact 
of the dolomite is a thrust fault, whose plane is irregular and 
which shows a strong tendency to be at a higher altitude where 
the underlying strata are resistant and at a lower altitude 
where they are weak. The dolomite beds, although they retain 
their characteristic lithology, are thoroughly shattered in the 
whole overriding mass, but the underlying beds are compara- 
tively little affected. The map shows clearly the disappearance 
beneath the thrust plate on the west and the emergence on the 
east of the folded Young Peak dolomite and the Trippe lime- 
stone, and this feature is easily recognized in the field. The 
occurrence of a small patch of dolomite undoubtedly belonging 
to the Lamb dolomite above the Trippe limestone on the 
eastern flank of the anticline suggests that this overriding plate 
had only a small extent, and this is borne out by features 
farther east. 

There are several other thrust plates above that of the Lamb 
dolomite. The small patches of the Hicks formation and the 



68 



GOU> HILL MINING DISTRICT, UTAH 



Chokecherry dolomite extending northward from North Pass 
Canyon are not easily delimited but are certainly present 
because of their characteristic lithology and, in the Hicks, char- 
acteristic fossils. Their "boundaries to the east and west are 

thought to be thrust faults. To the west is a somewhat larger 
thrust plate of Laketown dolomite, which contains recognizable 
and characteristic fossils. This plate is offset by a transverse 
fault, which is fairly well exposed on the south slope of peak 
7660. North of the transverse fault the overthrust plate of 
Laketown dolomite extends nearly 2,500 feet farther east and 
rests upon the overriding plate of Lamb dolomite. It is in turn 
overlain by dolomites similar in lithology to those in the 
Simonson dolomite. 

North Pass thrust , and minor related thrusts east of North 
Pass Canyon. — The North Pass thrust crops out at only one 
locality in the block east of North Pass Canyon. At two other 
places it may be located rather closely, however, and a true 
measure of its extent may be obtained from the exposures of 
the central fades of the Carboniferous rocks that lie above it. 

The only exposure of the thrust is found half a mile north of 
hill 6267, southwest of Blood Mountain. Here thin-bedded 
strata of the Oquirrh formation rest Upon thoroughly brecciated 
fossiliferous Laketown dolomite. The contact between the two 
is a thrust dipping about 10° N., which is exposed for only a 
short distance before being terminated to the west by gravel 
and to the east by a younger normal fault. 

The Laketown dolomite beneath the thrust is only 100 feet 
thick and rests upon limestones lithologically identical with 
those of the Guilmette formation. The, fault contact between 
the two parallels the North Pass thrust above. This 100-foot 
slice of Laketown dolomite is considered to be the eastward 
continuation of the thrust plate of the same formation that was 
found in North Pass Canyon, where it rests upon a similar 
thrust plate of Lamb dolomite. 

The main thrust may also be located rather closely on the 
south side of Blood Mountain. Just south of the road fork at 
an altitude of 5,854 feet there is an outcrop of brecciated 
fossiliferous Laketown dolomite, identical with that underlying 
the thrust half a mile to the northwest. Outcrops of the 
Oquirrh formation are found to the east, north, and west; and 
the North Pass thrust almost certainly is concealed by the 
intervening gravel. 'The thrust may also be approximately 
located for nearly a mile south of this region, for the six small 
outcrops of the Oquirrh formation south of hill 6267, as well as 
the beds at the base of the hill, are shattered, brecciated, and 
in some places dolomitized, suggesting that the thrust is not 
far beneath. - 

The remaining region in which the thrust may be recognized 
is in the southeast corner of the quadrangle, where there are 
several outcrops entirely surrounded by gravel. The largest 
and most westerly of these outcrops is composed of brecciated 
beds of the Oquirrh formation, which have been extensively 
silicified and dolomitized. The three small eastern outcrops are 
equally brecciated but are made up of dark dolomites similar 
to those in the Guilmette formation and the Simonson dolomite. 
In the northern outcrop were found unbroken fragments that 
contained the large brachiopod Stringocephalus burtoni, which 
is characteristic of these formations. On the map the three 
exposures are shown under the symbol for the Guilmette forma- 
tion, but it is not improbable that beds belonging to the Simon- 
son dolomite are present. The contact between the Devonian 
and Pennsylvanian strata is concealed, but it seems certain, 
because of the extensive brecciation and the stratigraphic 
relations, that this contact is a continuation of the North Pass 
thrust. 

Eastern border fault. — There is evidence from several sources 
that a normal fault of considerable throw must parallel the 
east front of the Deep Creek Mountains. The physiographic 



evidence of faulting has been noted on pages 61-62 and indicates 
a throw of about 2,000 feet. The stratigraphic evidence is 
conflicting: in part it indicates a throw of 2,000 feet, checking 
the physiographic evidence, and in part it suggests a displace- 
ment of 6,000 feet. These contradictory results are explained 
by the fact that the 2,000-foot throw is based on beds above 
the North Pass thrust, and the 6,000-foot throw on beds beneath 
the thrust. There have therefore been two periods of activity 
along the fault, the first preceding the thrust and the second 
following the thrust. 

Two groups of outcrops provide a measure of the movement 
preceding the thrust. One of these is about half a mile north 
of the entrance to Sheep Canyon, where a crescent-shaped out- 
crop of thoroughly brecciated limestones and dolomites is found 
only 1,000 feet east of the mountain front. These beds have 
been mapped as the Abercrombie formation and the Young Peak 
dolomite, respectively, because their lithology is characteristic 
of those formations. The contact between the limestone and 
the dolomite has a very gentle dip and apparently is close to the 
axis of the major anticline. The stratigraphic interval between 
these beds and the Prospect Mountain quartzite immediately 
to the west is 6,000 feet. 

The second group of outcrops includes those in North Pass 
Canyon, northwest of hill 6267. These are composed of gray 
and black laminated dolomites that are identical with beds in 
the Simonson dolomite. The two northwesterly outcrops dip 
25°-90° E. and are less than a quarter of a mile from beds of 
the Abercrombie formation that have gentle eastward dips. 
The stratigraphic interval between the two formations is again 
6,000 feet, and the only fault that could reasonably come be- 
tween them is the eastern border fault. IncidentaEy, the differ- 
ence in stratigraphy on the east side .of the fault between this 
region and that to the south shows that the North Pass Canyon 
transverse fault continues east of the border fault. 

The best stratigraphic measure of the movement along the 
eastern border fault after the thrust is provided by the 100-r 
foot slice of Laketown dolomite lying beneath the North 
Pass thrust. This was correlated with the similar thrust 
plate west of the border fault, and by projecting both plates to 
the fault line, the throw is seen to be 2,000 feet (sec. J'- J"), 
thus checking the physiographic evidence. 

The fault plane itself is exposed only along the divide between 
North Pass Canyon and Blood Canyon. In this region the 
fault splits into two branches, both of which offset the Blood 
Canyon transverse fault. The throw along the westerly branch 
is comparatively small, amounting to about 300 feet; the easterly 
branch has a greater throw, but it cannot be directly measured 
in the vicinity of the outcrops, as the North Pass thrust under- 
lies the beds to the east but has been eroded west of the fault. 

Minor structural features on Blood Mountain. — A normal fault 
following the west side of Blood Mountain offsets the Blood 
Canyon transverse fault about 1,200 feet. The transverse fault 
has a considerably lower dip at this point than in the region to 
the west, and it is believed that the large offset reflects this low ' 
dip. The normal fault must die out southward if the inferred 
position of the North Pass thrust southeast of hill 6267 is correct. 

The northeasterly fault cutting through the crest of Blood 
Mountain has a throw of about 400 feet, measured by the posi- 
tion of a thick limestone bed on each side. This fault branches 
to the north, and the western branch is cut off by the Blood 
Canyon fault. A fault with similar strike to the southwest, 
which terminates the exposure of the North Pass thrust, must 
have a throw of about the same magnitude, to judge from the 
altitude of the thrust on each side of it. 

The Pennsylvanian sandstones and limestones that underlie 
Blood Mountain show numerous discontinuous folds. In sec-- 
tion /'-/" a syncline is shown just east of the fault, but this 
feature cannot be traced much beyond the line of the section, 



GEOLOGIC STBUCTTJKE 



69 



and In fact Jt is replaced by a minor anticline to the north. 
The irregular folding is probably due to the North Pass thrust, 
which underlies the mountain at no great depth. 

Faults east of Overland Canyon. — South of the eastern portion 
of the Blood Canyon transverse fault several faults have been 
recognized. Most of these are of minor importance, and only 
two seem to warrant special description. These are the two 
faults with west-northwesterly strike at the south end of the 
Clifton Hills. Both have low dips to the south — the northern 
one, less than 30°; the southern, about 45°. (See sec. H-H' .) 
In both faults the beds on the southern or hanging-wall side 
are bent into local overturned folds. They are thus similar 
to the eastern portion of the Blood Canyon fault and are con- 
sidered to represent older transverse faults. The northern of 
these two faults is both cut by and cuts off minor normal faults. 

Mutual relations of the structural features, — The first recorded 
structural event in the Deep Creek Mountain region was the 
initiation of compressive forces from the west-northwest. These 
forces resulted in the formation of the transverse faults striking 
in that direction and in the anticlinal fold along the east front 
of the range. Then came a period of relaxation, expressed by 
4,000 feet of the 6,000 feet total throw along the eastern border 
fault. These features are believed to belong to the second struc- 
tural cycle. Renewed compression from the same direction 
as before resulted in the formation of the North Pass thrust and 
the associated thrust plates exposed in North Pass Canyon. 
After the second compressive movement a second period of 
normal faulting ensued, as shown by the northeasterly fault on 
Blood Mountain, which cuts the thrust plates and is cut off 
by the Blood Canyon transverse fault. These thrusts and nor- 
mal faults are correlated with the third structural cycle. 

A third renewal of compression, considered to mark the fourth 
cycle, is indicated by the Blood Canyon and related east-west 
transverse faults. It seems probable that minor thrusting oc- 
curred in this period also, for minor thrust faults are apparently 
associated with the Dry Canyon fault, which belongs to this 
period. 

The final episode in the structural history of this block resulted 
in the late normal faulting that has largely produced the present 
topography. The eastern border fault is the most readily 
studied of these faults and shows that some of them at least have 
had a rather complex history, 

UIYABI CANYON BLOCK 

The southern boundary of the Uiyabi Canyon block is the 
Blood Canyon transverse fault, already described. The north- 
ern boundary, west of Clifton Flat, follows the parallel trans- 
verse fault on the south side of Ochre Mountain. East of 
Clifton Flat this fault continues for only a short distance, and 
the boundary in this region is marked by three large faults, as 
shown on plate 3. 

The block is underlain almost entirely by Carboniferous 
rocks, chiefly of the central facies of the Oquirrh formation. In 
the pass through which the Lincoln Highway descends to the 
Deep Creek Valley these rocks are thrust over contorted Devo- 
nian limestones and dolomites, and it is probable that this 
relation holds true for the whole block . The thrust is considered 
to be the North Pass thrust (sec. J- J"— J') . Along the western 
margin of the mountains, on the other hand, Devonian strata 
are locally thrust upon the Pennsylvanian along faults that 
are thought to be younger than the main thrust (sec. O-O'). 
The Carboniferous beds are folded into a broad anticline whose 
axis is probably close to the west side of Blood Canyon. * West 
of the anticlinal axis the Pennsylvanian beds have been bent 
into discontinuous folds, but east of the axis the beds have a 
uniform eastward dip averaging about 25°. Normal faults of 
several ages are found throughout the block. A transverse 
fault at the northern border of the block (sec. J-J") is accom- 



panied by warping, and a higher thrust plate is exposed in one 
of the downwarped portions (sees. L-L' and I-I') . 

Minor structural features between Christiansen and Sheridan 
Gulches. — On the north side of Christiansen Canyon a reverse 
fault striking nearly due north and dipping steeply to the west 
has thrust Devonian beds over the Oquirrh formation (sec, 
O-O'). West of the main thrust are two minor faults that 
strike northwest and are marked by wide breccia zones. The 
Devonian rocks are closely folded and are locally overturned, 
as is clearly shown by the contact between the Guilmette for- 
mation and the Simonson dolomite near the western extremity 
of the spur. 

A northwesterly transverse fault east of this area of folded 
and thrust Devonian rocks separates beds belonging to the 
central facies of the Oquirrh formation from gently folded beds 
of the -Guilmette formation, upon which rests a small patch of 
the Woodman formation that belongs to the eastern facies. 
The fault is terminated at the southeast by the Blood Canyon 
transverse fault, which, east of the intersection, forms the 
boundary between the two facies. As the central facies of the 
Carboniferous rocks are found in the plate above the North 
Pass thrust and the eastern facies in the overridden mass, 
this transverse fault in Christiansen Gulch marks the southern 
boundary of the North Pass thrust plate. The North Pass 
transverse fault (p. 67) has similar relations and a parallel 
strike, and it is therefore suggested that the two northwesterly 
transverse faults are segments of the same fault which have 
been offset by the Blood Canyon fault. 

Direction and amount of movement along the Blood Canyon 
fault. — The" correlation of the transverse fault in Christiansen 
Gulch with the North Pass transverse fault provides a measure 
of the amount of movement along the Blood Canyon fault. 
The two segments indicate that the rocks south of the Blood 
Canyon fault have moved about a mile eastward, relative to 
those on the north side. Several features appear to corroborate 
this conclusion. The direction of the movement appears to be 
confirmed by the drag effects along the Blood Canyon fault, 
particularly as shown by the fault east of hill 6526, north of 
Blood Canyon, and by the drag folds along the most easterly 
exposures of the Blood Canyon fault. 

The eastern limit of minor folding in the Oquirrh formation 
on both sides of the Blood Canyon fault is also offset in the same 
direction and in roughly the same amount. North of the fault 
the minor folding dies out east of hill 7511, at the head of Blood 
Canyon; to the south, it dies out on Blood Mountain. 

The fact that many of the other structural features found 
north of the fault cannot be recognized in the proper positions 
to the south appears to be a serious objection to the suggested 
displacement. This may be due, however, to either of two 
factors. One is that the late normal faults which cut the Blood 
Canyon fault are so placed that north of the transverse fault 
they duplicate the major earlier normal fault in Blood Canyon, 
and south of the transverse fault, according to the probable 
projections, they conceal it. The second factor is that to the 
north the normal faults are readily apparent by reason of their 
cutting distinctive formations, such as the Ochre Mountain 
limestone and the Manning Canyon formation, but to the south 
the poorly exposed beds are all of the Oquirrh formation, in 
which the detection of faults is difficult, and the evaluation of 
of their displacement, when found, almost impossible. 

Minor thrust east of benchmark 5684 on Lincoln Highway. — A 
second area of Devonian thrust over Pennsylvanian rocks is 
found about 2 miles north of the locality above described and 
just south of the Lincoln Highway. Here beds of massive 
limestone and dark dolomite containing Cladopora sp. clearly 
overlie the Oquirrh formation above a fault that dips about 
30° NW. The fault is thought to continue north of the high- 
way and to lie between the isolated hills of the Oquirrh forma- 



70 



GOLD HILL MINING DISTBICT, UTAH 



tion and the main southern spur of Ochre Mountain. The 
limestone is considerably deformed, as are also the thinner- 
bedded rooks in the spur to the east. The thrust apparently 
terminates against the transverse fault that forms the northern 
boundary of the block. The transgression of this thrust along 
its strike from the Guilmette formation into the Oquirrh for- 
mation is thought to indicate that the displacement along it is 
small, and that it, as well as the thrust to the south, represent 
minor thrusts that have cut through the underlying North Pass 
thrust and brought up rocks that normally lie beneath the 
major thrust. 

North Pass thrust, — The North Pass thrust, which must under- 
lie the whole Uiyabi Canyon block, crops out at two places in 
the northwestern portion of the block. In both exposures, 
which are along the Lincoln Highway west of benchmark 6149, 
brecciated dolomites and yellow, sandstones of the Oquirrh for- 
mation rest upon highly crumpled beds of the Guilmette forma- 
tion (fig. 9). These Devonian beds below the North Pass 
thrust are almost certainly the equivalents of the beds of the 
same age exposed by the minor thrusts described in the preced- 
ing paragraphs. 

The North Pass thrust plane must be considerably folded or 
warped, because at a number of places beds of the Oquirrh 
formation crop out at lower altitudes than those at which the 




a Feet 



Figure 9.— Crumpling of Guilmette formation 1 mile west of benchmark 6149, north of Lincoln 
Highway, a, Dolomite; 6, sandstone; c, limestone. 

fault is exposed along the Lincoln Highway. This later defor- 
mation is probably the result of the stresses that caused the 
east-west transverse fault that bounds the block on the north. 
Minor folds in Uiyabi Canyon. — Several rather discontinuous 
folds are found in the Oquirrh formation in the western portion 
of Uiyabi Canyon. Two anticlines and a syncline were dis- 
tinguished, but only one — the western anticline — can be traced 
for much more than a mile. The axis of this fold strikes west 
of north and follows a course that corresponds roughly with the 
ridge line between Uiyabi Canyon and the Deep Creek Valley. 
The western limb of the fold extends down to the valley gravel 
with increasingly steep dips, but the eastern limb has moderately 
low dips and is succeeded eastward by a shallow syncline. The 
syncline cannot be traced northward, and the structure there 
seems to be that of a single broad anticline which plunges to 
the north. The second anticlinal axis is about a quarter of a 
mile east of hill 7009 within Uiyabi Canyon. This fold also 
cannot be traced to the north, and its place is taken by the 
region of confused dips and minor faults near hill 6831. East 
of the second anticline, nearly east- west strikes and northerly 
dips are dominant for more than a mile and are succeeded east- 
ward gradually by the north-south strikes and easterly dips 
that characterize the remainder of the district. A generalized 



idea of the folding is given by section O-O' and the left-hand 
portion of section J' -J". 

Minor faults west and southwest of Clifton Flat. — Minor faults 
of several ages and characters are found in the belt of minor 
folding. In almost every one the throw is unknown, because of 
the poor exposures and the lenticular nature of the Oquirrh 
formation. Along the west side of the Deep Creek Mountains 
there is a rather distinctive contact between massively bedded 
limestone and dolomite and underlying thinner-bedded rocks. 
By means of this contact the presence of numerous faults can 
be proved. Only one of these faults, along which there is a shift 
of the contact amounting to several hundred feet, has a suffi- 
cient displacement to be shown on the geologic map. This is 
the eastward-striking fault that ends near hill 7472. The short 
north-northwesterly fault about half a mile southeast of this 
hill is a small reverse fault with a throw of less than 100 feet. 
The fault of low dip just east of hill 7194 along the northern 
boundary of Uiyabi Canyon is probably an old normal fault, 
tilted to its present position by later deformation, as it appears 
to have normal relations. It is cut off on the east by a younger 
normal fault, but the faulted segment may be. represented by 
an obscure fault near hill 6831. 

The younger normal fault is probably a continuation of a 
fault of similar strike that cuts the North Pass, thrust along the 
Lincoln Highway. The thnist'is about 100 feet 
lower west of this fault. 

Major anticline south of Clifton Flat. — -A major 
anticline affects all the Carboniferous rocks that 
lie in the block above the North Pass thrust, 
Its axis is difficult to trace because of younger 
structural features but appears to trend nearly 
north and to pass beneath the gravel of Clifton 
Flat just east of the entrance to Uiyabi Canyon. 
Several younger normal faults cut the anticline, 
and as a result the oldest formation involved in 
the fold, the Ochre Mountain limestone, is ex- 
posed on the eastern flank rather than at the 
core. East of the axis there is 'a rather constant 
eastward dip, but west of it the minor folds in 
Uiyabi Canyon are superposed on the older fold, 
although even here the more westerly beds are 
the higher stratigraphically (eec. 0-0'). 

Normal faulting in Blood Canyon. — On the 
western flank of the major anticline the Oquirrh 
formation has been brought into contact at 
two places with the Ochre Mountain limestone by faults 
dipping 30° W. These are believed to be parts of the 
same fault, as the. recent movement of 2,000 feet along the 
eastern border fault (p. 68), which is exposed between them, 
is of the correct amount to cause the repetition (sec. O-O'). 
In both of the exposures of the westward-dipping fault the 
normal eastward dip of the Ochre Mountain limestone is 
reversed for a distance of 100 feet or so from the fault. Along 
the eastern exposure a considerable thickness of the Manning 
Canyon formation is found beneath the Oquirrh, but along the 
western exposure these beds are missing over much of the 
distance. 

Transverse fault north of Overland Canyon. — The best exposure 
of the transverse fault north of Overland Canyon is about 1,600 
feet northeast of benchmark 5768, Here dark quartzites and 
black micaceous schists that are metamorphosed members of 
the Manning Canyon formation abut against massively bedded 
Ochre Mountain limestone. In most places, however, the beds 
northeast of the fault have been engulfed by the quartz mon- 
aonite, and the limestone beds to the south are almost un- 
touched. This is but one of several examples of the preference 
shown by the intrusive for following fault contacts during its 
emplacement. The eastward extension of the fault may be 



GEOLOGIC STRUCTTJBE 



71 



approximately located by a belt of jasperoid that almost 
certainly represents a siliciflcation of the fault breccia. The 
transverse fault appears to be cut off by a younger normal 
fault about at its intersection with the road to the Midas mine, 
but the presence in this vicinity of several small areas of 
monzonite makes the exact relations uncertain. The nor- 
mal fault is itself terminated by the Blood Canyon transverse 
fault. 

Normal faults north of Overland Canyon, — The normal faults 
north of Overland Canyon have exerted an even more striking 
influence upon the quartz monzonite intrusion than the north- 
westerly transverse fault. Four faults have been recog- 
nized, and all of them, in at least parts of their courses, 
form the contact between the intrusive and the sedimentary 
rocks. 

The most northwesterly of these faults forms the linear 
boundary of the isolated area of quartz monzonite east of 
benchmark 6855 at the head of Overland Canyon. Its course is 
east-northeast, and its dip is to the northwest. A quartz- 
carbonate vein follows the fault. A minimum estimate of the 
displacement is given by the upper contact of the Manning 
Canyon formation, which is cut off by the fault about 1,000 feet 
west of hill 6807. As the Manning Canyon is nowhere exposed 
on the hanging-wall side of the fault, the displacement must 
amount to at least 2,000 feet (sec, G-G') . The age of this fault 
with respect to the transverse fault is not known. 

The next fault to the southeast is perhaps open to question, 
because it is, throughout its exposure, bounded by quartz 
monzonite on the southeast. A quartz-carbonate vein is also 
found along this contact. There is little doubt that the mon- 
zonite was intruded along a fault, for, ae shown in section G-G', 
there is a displacement of about 2,500 feet between the outcrops 
of the Manning Canyon formation at the Midas mine and those 
northwest of the monzonite. The greater part of the throw 
must have taken place along this fault, but a small part may be 
represented by the third fault of this group. This is exposed 
on the west side of the ridge about a mile north of the Midas 
mine; its throw is probably comparatively small, so far as ean 
be determined by the members of the Oquirrh formation on 
its two sides. The age of the third fault relative to the north- 
westerly transverse fault is unknown; the second one is clearly 
older, as it cannot be recognized southwest of the transverse 
fault. 

The fourth fault is that at the Midas mine. The displacement 
here also is relatively small, amounting to about 350 feet. This 
fault must cut the northwesterly transverse fault, but the 
contact between the two has been destroyed by the intrusion. 

Just south of the Midae mine there is a fault of similar strike 
but with a low dip to the southeast. It is cut off by the Blood 
Canyon transverse fault, but beyond this its relations to the 
other faults are not known. 

Minor faults are abundant throughout this region, but the 
displacements rarely amount to more than 10 feet and on many 
are measured in inches. To the east the minor faulting is 
clearly shown by thin limestone beds. It was perhaps "more 
abundant here because of the probable closer approach at this 
point to the underlying North Pass thrust. 

Ochre Mountain thrust. — The exposures of the Oquirrh for- 
mation that underlie hill 6519, on the northwest side of Clifton 
Flat, and the low hills north of the road to the Monooca mine, 
on the northeast side of Clifton Flat, belong to the western 
facies of the formation and must therefore lie above the Ochre 
Mountain thrust (sees. /-/' and L-L') . ■■ The beds exposed are 
rather thick-bedded cherty and ehert-free limestones and 
dolomites, with only minor sandstones. Some of them are 
identical with beds in the northwest quarter of the quadrangle, 
which are definitely a part of the western facies. The thrust 
plane is everywhere concealed by gravel within this block and 
may be located closely only on the southwest side of hill 6519, 



where the two facies of the Oquirrh formation are only a few 
hundred feet apart. 

Warping of the North Pass and Ochre Mountain thrusts. — The 
two major thrusts have both been considerably deformed in 
this block. This is shown not only by the outcrops of the 
North Pass thrust at altitudes considerably higher than in 
regions where the Oquirrh formation above the thrust is ex- 
posed, and by the younger reverse faults that cut through the 
thrust, but also by the close proximity of the two major thrusts 
in Clifton Flat. The warping is most intense adjacent to. the 
east-west transvferse fault that bounds the block on the north. 
An anticlinal warping has brought the North Pass thrust to 
the surface in this region, and a syncline to the east has preserved 
a portion of the plate above the Ochre Mountain thrust. Similar 
warping is associated with the Garrison Monster transverse 
fault to the north (p. 83), where the two features are considered 
to be genetically related. 

The close proximity Of the two major thrusts in Clifton Flat 
permits a rough estimate of the thickness of the plate between 
them. The original eastward dip of the common limb between 
the anticline to the west and the syncline to the east has, 
however, been increased by two other factors. One of these is 
the eastward tilt imparted to the footwall block of the western 
border fault (p. 61); the other is that the northern continuation 
of the eastern border fault extends beneath this part of Clifton 
Flat, and although it cannot be recognized on the north side of 
the flat, it must be represented in the central part either by an 
actual fracture or by a pronounced downwarp to the east, as 
its throw on the south edge of the fiat is still 2,000 feet. Neither 
of these factors can be accurately determined, but rough esti- 
mates indicate that the North Pass thrust plate was probably 
about 2,000 to 2,500 feet thick at this point. 

Transverse fault on the south side of Ochre Mountain, — A trans- 
verse fault is continuously exposed for more than a mile about 
half a mile south of hill 6886, south of Ochre Mountain, and is 
marked by a zone of silicifled and crushed dolomite several 
hundred feet in width (sec. J- J'). In this portion of the fault 
the dip is steep, and the fault .separates the western facies of 
the Carboniferous to the north and the central facies of the 
Carboniferous to the south. These relations hold for the 
exposures of the fault in two gravel-surrounded outcrops to the 
east, but the breccia zone is considerably narrower. Still 
farther east the fault curves around the north end of hill 6519 
and the dip flattens notably. This pronounced change in the 
course of the fault corresponds with its intersection with the 
older Ochre Mountain thrust (sec. L-L') . The presence of the 
low-angle thrust fault at this point was probably the major 
factor in causing the change from steep to fiat dip in the trans- 
verse fault, as the related Garrison Monster transverse fault to 
the north (p. 83) behaves in a similar manner where it cuts 
through an older thrust. 

It is highly improbable that the gently dipping portion of the 
fault represents a later thrust that has concealed the steeply 
dipping transverse fault, for there are no other exposures of 
such a fault in the higher areas to the northeast. 

East of hill 6519 the transverse fault is concealed by the 
gravel of Clifton Flat. It is thought to be represented east of 
the gravel by a wide crushed zone south of hill 6266, half a mile 
east of the road intersection at an altitude of 6,089 feet. This 
fault separates Ochre Mountain limestone on the north from 
the western facies of the Oquirrh formation on the south — 
relations similar to those shown by the transverse fault on hill 
6519, on the northwest side of the flat. The exposure of the 
fault extends only a short distance to the east, however, where 
it is terminated by a large normal fault that forms a part of the 
boundary of this structural block. 

The amount of movement along the transverse fault is not 
known. If an analogy may be drawn from the similar Garrison 
Monster fault, the pronounced warping south of the fault implies 



72 



GOLD HILL MINING DISTRICT, UTAH 



that the rooks on the north side moved relatively eastward. 
If that assumption is correct, there must have been a minimum 
movement of a mile in this direction. If the south side moved 
relatively eastward, however, the amount of movement must 
have been much greater. Both of these estimates are based on 
exposures of the Oquirrh formation north of the fault. 

Normal faults bordering the block east of Clifton Flat. — The 
normal fault that terminates the transverse fault described in 
the preceding paragraphs brings the central facies of the Oquirrh 
formation on the east into contact with the western facies of 
the same formation. The throw must therefore be large, but 
it cannot be estimated in this region, for the altitude of the Ochre 
Mountain thrust separating the two facies cannot be determined 
on either side of the fault. The normal fault is considered 
related to the intrusion of the quartz monzonite, as shown by 
its relations in the block to the north (p. 76). 

The northeasterly fault three-quarters of a mile northwest 
of Montezuma Peak is poorly exposed throughout but is marked 
by a zone of shattering and erratic dips. The central facies 
of the Oquirrh formation forms both walls, and as no distinctive 
beds were recognized, its throw is unknown. The fault is per- 
haps related to the normal faults of similar strike on the southern 
slope of Montezuma Peak. 

Mutual relations of the structural features. — The Uiyabi Can- 
yon block presents a sequence of structural events similar to 
that found in the Deep Creek Mountain block, to the south. 
Tilted normal faults in Uiyabi Canyon are probably older than 
the major anticline on the south side of Clifton Flat. The anti- 
cline itself and some of the normal faults on the south side of 
Montezuma Peak in turn antedate the North Pass thrust and 
related features that were formed in the third structural cycle. 
Normal faults that cut these features are in turn cut off by the 
great transverse faults, or by their associated faults which char- 
acterize the fourth cycle. The transverse fault on the south 
side of Ochre Mountain is itself cut by a normal fault related to 
the intrusion. Finally, the late normal faults are found on the 
south side of Clifton Flat and along the western border of the 
block 

OCHRE MOUNTAIN BLOCK 

The Ochre Mountain block includes not only Ochre Moun- 
tain but also the low-lying Mils to the north. Its northern 
boundary is marked by the wedge-shaped tongue of quartz 
monzonite that extends westward from the town of Gold Hill 
along the south side of Dutch Mountain. To the west the block 
is limited for several miles by the western border fault, but this 
fault appears to die out at about the northwest point of Oehre 
Mountain, and from this point to the western tip of the quartz 
monzonite wedge the boundary of the block follows gravel-filled 
valleys that have no structural significance. The main body 
of quartz monzonite lies east of the block. It includes several 
roof pendants of sedimentary rocks, whose structure is consid- 
ered in this section. 

The Ochre Mountain thrust is the dominant structural feature 
in the block (sec. K-K', M-M'). A nearly continuous exposure 
of this fault extends in a north-northwesterly direction from 
the quartz monzonite stock to the northern boundary of the 
block. The thrust is also exposed in a "window" west of the 
thrust, and in several of the roof pendants. Several transverse 
faults with low north dips are exposed on Ochre Mountain that 
are thought to be contemporaneous with the major thrust (sec. 
J- J'). There are in addition several others, chiefly normal 
faults, whose relations both to one another and to the thrusts 
provide the most complete chronologic sequence found in the 
whole quadrangle (sec. K-K'). 

Over much of the block the rocks are poorly exposed, owing to 
the fact that the present surface closely parallels the old post- 
mature surface (p. 61) and faults are difficult to trace. The 
absence of distinctive beds in the Ochre Mountain limestone, 



which underlies much of the area, adds to the difficulty and pre- 
vents accurate measurement of fault throws in many places. 
On the western face of Ochre Mountain rock exposures are 
unusually good, and several distinctive beds are present. As a 
result, many faults were recognized, and their abundance in 
this region probably provides a measure of the amount of fault- 
ing in the remainder of the block. 

Main outcrop of the Ochre Mountain thrust. — The most south- 
easterly outcrop of the Ochre Mountain thrust is just west of 
the Lincoln Highway about a quarter of a mile north of bench- 
mark 5723. At this point, north of and below the thrust, are 
sandstones and black shales belonging to the central facies of 
the Manning Canyon formation. These beds are badly crum- 
pled and show marked variations in strike and dip. To the 
south and above the thrust are poorly exposed black shales with 
a few interbedded fossiliferous limestones that belong to the 
western facies of the same formation. They are overlain by 
cherty dolomites and limestones of the Oquirrh formation. The 
thrust is poorly exposed here, and were it not for the difference 
in lithology between the two facies of the Oquirrh formation 
overlying the two areas of the Manning Canyon, it might easily 
pass unrecognized. To the southeast the termination of the 
thrust by the quartz monzonite stock is concealed by gravel. 

To the west and north the thrust is also concealed by gravel 
for some distance. The beds at the base of the ridge above the 
northern Ochre Spring are the Ochre Mountain limestone and 
the western facies of both the Manning Canyon and Oquirrh 
formations. They show rather variable strikes and dips, and 
this variation is illustrated by the irregularity of the outcrops 
of the three formations. Hill 5919, between the two springs, 
is covered largely by quartzite float, but the tunnel at the north- 
ern spring indicates that the quartzite is present as thin beds in 
less resistant black shale. East of these beds and surrounded 
by gravel are several low hills composed of the central facies of 
the Manning Canyon formation. The thrust must be concealed 
by the gravel between the outcrops of the two facies. 

About a quarter of a mile west of the point at an altitude of 
5,658 feet shown on the map the concealed thrust is cut by an 
eastward-dipping normal fault. West of the normal fault, 
whose post-thrust throw is about 150 feet, the thrust is shown 
by eastward-dipping thick-bedded Ochre Mountain limestone 
resting upon the central facies of the Manning Canyon forma- 
tion. The stratigraphic displacement along the normal fault 
in the beds above the thrust amounts to several thousand feet. 
The normal fault has clearly been active at least twice, there- 
fore, the bulk of the movement being earlier than the thrust. 
The normal fault has also caused the exposure of the thrust 
southwest of hill 5919 between the two Ochre Springs. The re- 
lations here are similar to those west of the fault to the north. 

Northwest of this normal fault there are two lines of outcrop 
of the thrust, as a result of an east-west normal fault whose 
throw is about 50 feet. To the north another normal fault, of 
northwesterly strike, displaces the thrust 100 feet. A small 
"klippe" or thrust outlier occurs on peak 5959, northeast of 
this region, Ochre Mountain limestone above the thrust resting 
upon beds low in the Oquirrh formation. The salient of the 
thrust due west of the "klippe" conceals the Manning Canyon 
and Oquirrh contact in the overridden rocks for nearly half a 
mile. Locally the Ochre Mountain limestone above the thrust 
shows zones of disturbed dips parallel to the thrust that appear 
to represent minor sympathetic thrusts. These are commonly 
reflected in the topography by pronouneed benches. 

Just north of the intersection of the thrust with the trail 
from Gold Hill to the Erickson ranch, the western facies of the 
Oquirrh formation replaces the Ochre Mountain limestone as 
the formation above the thrust. This is the result of an east- 
northeast fault earlier than the thrusting. The east-northeast 
fault is exposed for only a short distance along the divide 



GEOLOGIC STRUCTURE 



73 



between the Gold Hill and Deep Creek drainage basins, but 
its persistence for nearly 3 miles westward is proved by the 
continued presence of the Oquirrh formation to the north of 
the trail and of the Oehre Mountain limestone to the south. 
The age relations of this fault seem to ally it with the north- 
northwest transverse faults, in epite of its divergent strike, 
which may be the result either of a low dip or of warping accom- 
panying the thrusting. 

North of its intersection with the transverse fault the over- 
thrust can be traced continuously for more than half a mile. 
Its outcrop is sinuous, owing chiefly to the effect of the topog- 
raphy, although variations in dip play some part. The western 
facies of the Oquirrh formation continues to overlie the thrust 
and beneath it are found Ochre Mountain limestone and the 
central facies of both the Manning Canyon and the Oquirrh. 
The appearance of the Ochre Mountain limestone immediately 
below the thrust coincides with an increase in complexity in 
the structure of the overridden rocks. Two minor thrusts in 
the rocks below the thrust were recognized in this region in 
addition to minor folds (sec. N-N'). The more southerly of 
the minor thrusts Is exposed just north of the road to the Brick- 
son ranch and east of the outcrop of the main thrust. It has 
resulted in the Ochre Mountain limestone overriding the Man- 
ning Canyon formation. The strike of the minor thrust is 
nearly at right angles to the strike of the bedding. Because of 
this it involves, in addition to the Ochre Mountain limestone, 
both the Manning Canyon and Oquirrh formations. The rela- 
tively small displacement suffered by the Manning Canyon and 
Oquirrh contact on the northeastern extension of the fault 
indicates that the fault dies out within a rather short distance 
in this direction. The changes in strike of this contact in the 
overridden beds are considered to have been developed as a 
result of the thrust. The behavior of the minor thrust described 
in the next paragraph indicates that the dip of this fault proba- 
bly steepens notably along its southwestern extension and that, 
coincident with the change in dip, the strike swings to nearly 
east-west. 

These two features are clearly shown by the second of the 
minor thrusts, which is found just beneath the Ochre Mountain 
thrust east of peak 612S. Here, in the east-west draw north of 
hill 5925 both the minor thrust and the major thrust are well 
exposed. The minor thrust strikes nearly due east and dips 
60° N. Ochre Mountain limestone is found above the fault, 
and the Manning Canyon formation below. Toward the east 
the strike of the thrust swings to the north and the dip flattens 
notably, as is shown by the trace of its outcrop. Only a small 
width of the thrust plate of Ochre Mountain limestone is 
exposed, owing to overlapping by the main thrust. 

The complexity in structure shown by the overridden rocks 
in this region contrasts with the simple structure to the south- 
east, where the contact between the Manning Canyon and 
Oquirrh formations shows that there has been little deformation 
of the rocks beneath the thrust. It seems probable that the 
change in structure is due to the presence of the resistant 
Ochre Mountain limestone immediately below the thrust in 
the northern area, in that the competent limestone is much 
more readily fractured and that a break in the limestone would 
involve breaking in the immediately adjacent nonresistant beds. 

The outcrop of the Ochre Mountain thrust is terminated 
less than a quarter of a mile north of the second of the minor 
thrusts by a northwesterly normal fault. This normal fault 
forms the contact between beds above the thrust to the west 
and beds below the thrust to the east, northward from the inter- 
section to the northern boundary of the block. The throw 
along the normal fault amounts to about 300 feet (p. 77). 

"Window" west of the main outcrop of the Ochre Mountain 
thrust. — Another isolated and poor outcrop of the thrust is in 
a "window" in the open valley about three-quarters of a mile 
SBU-M 6 



west of the Ochre Springs (sec. M-M'). The presence of the 
thrust here is shown by outcrops, in the floor of the valley and 
near its edges, of beds of the Ochre Mountain limestone and the 
Manning Canyon and Oquirrh formations, in striking uncon- 
formity with the eastward-dipping Ochre Mountain limestones 
on each side. This relation is most clearly shown in the south- 
east corner of the valley, where there are small outcrops of the 
Manning Canyon and Oquirrh formations. The beds of the 
Ochre Mountain limestone immediately above the fault have 
irregular strikes and dips, in striking contrast to the uniformity 
of their attitude higher on the ridge. The thrust has caused 
an erratic distribution of the three formations that are here 
beneath it, but the lack of an adequate number of outcrops 
prevents the determination of the character of this defor- 
mation. In the left-hand portion of section M-M' it is ex- 
tremely generalized. 

Ochre Mountain thrust east of the Lincoln Highway. — Although 
the main outcrop of the Ochre Mountain thrust is terminated 
on the southeast by the quartz monzonite, there is ample 
evidence that the thrust plate originally extended mueh farther 
eastward, over the region now underlain by the intrusive rock. 
This is shown by the occurrence of the western facies of the 
Carboniferous formations in roof pendants and locally by small 
exposures of the thrust itself. In this region, however, the 
thrust plane has been affected by faulting related to the 
intrusive. 

The exposures of the Oquirrh formation on the east side of 
the Lincoln Highway and south of the point where the thrust 
crosses the road belong to the western facies of the formation 
and are the continuation of beds west of the road that occur 
above the thrust. These beds are west of a north-south tongue 
of the quartz monzonite, which has apparently followed a pre- 
existent north-south fault, as to the east Ochre Mountain lime- 
stone is exposed. The limestone is now separated by rather 
narrow belts of quartz monzonite on the north, east, and south 
from other masses of Ochre Mountain limestone and was proba- 
bly continuous with them before the intrusion. The limestone 
masses are those in the vicinity of the Lucy L mine, the large 
roof pendant north-northeast of Clifton, which includes also 
beds of the western facies of the Oquirrh formation, and the 
block of limestone upon which Clifton itself is built. 

All these exposures are considered to be above the Ochre 
Mountain thrust, for at several places the limestone is in con- 
tact with either the Manning Canyon or the Oquirrh formation, 
In relations that can be explained only by thrusting. This is 
definitely proved at the Lucy L mine, where mine workings 
expose the thrust and also show that beds belonging to the 
central facies of the Oquirrh formation extend beneath a hill 
capped with Ochre Mountain limestone. (See p. 141 and 
fig. 26.) The localities at which the thrust was recognized 
in this region are shown on plate 3. 

The distribution of the small exposures of the thrust show 
that it has suffered deformation in this region as compared to 
its relatively undisturbed condition to the west and north. 
Two normal faults seem to have been the chief factors in the 
deformation. One of these is the northern continuation of a 
fault that displaced the thrust in the Uiyabi Canyon block 
(p. 72) and has dropped the beds to the west at least 1,000 feet. 
The second fault terminates on the west the exposures of the 
thrust and the rocks above it just west of the Lucy L mine. 
Its throw cannot be accurately measured but must be of the 
same magnitude as that of the parallel fault to the west, 
although in the opposite direction. 

The restriction of these large post-thrust disturbances to the 
jvicinity of the quartz monzonite suggests that the faulting is 
genetically connected with the intrusion, and this view seems 
to be somewhat confirmed by features of the ore deposits 
observed near the faults (pp. 88-89). 



74 



GOLD HILL MINING DISTRICT, UTAH 



Magnitude of the Ochre Mountain thrust. — The amount of 
movement along the thrust cannot be accurately determined. 
The force causing the thrust must have come from the west, 
and a minimum estimate may therefore be obtained from the 
distance between the easternmost and westernmost outcrops 
of the thrust, or of rocks known to overlie the thrust. This 
distance amounts to more than 5 miles. It must, however, be 
far short of the true figure, for the lithologie distinction between 
the westernmost outcrop of the central facies of the Oquirrh 
formation beneath the thrust and the easternmost outcrop of 
the western facies is everywhere evident. A figure approximat- 
ing 20 miles would seem to be nearer the true amount but has, 
of course, no basis in field observations. 

Northward-dipping transverse faults on Ochre Mountain. — 
Three faults with rather low north dips and east strikes occur 
on Ochre Mountain in the rocks above the Ochre Mountain 
thrust. They are in general poorly exposed and are therefore 
difficult to trace. All these faults art probably contemporane- 
ous with the main thrust, for their relations to normal faults 
appear to be the same as those shown by the thrust. The 
movement along two of the faults appears to have been dom- 
inantly horizontal, and, as the other is closely related to them, 
they are all considered to be rather flat portions of transverse 
faults. 

The southern of the three faults was recognized at several 
places south and east of the summit of Ochre Mountain but was 
not traced definitely between these points. The longest of 
these recognized outcrops was found at the head of Gold Hill 
Wash, where the fault crosses the Lincoln Highway 500 or 600 
feet southwest of benchmark 6972. In this region the Ochre 
Mountain limestone is north of the fault and the western facies 
of the Manning Canyon and Oquirrh formations to the south. 
The fault is cut off on the east by the same normal fault that 
cuts the Ochre Mountain fault near Ochre Springs (p. 72). 
East of the normal fault the continuation of the transverse 
fault is uncertain because of faulting related to the quartz 
monionite intrusion, but segments of faults that may represent 
portions of it are shown on plate 3. West of the highway the 
fault may be traced for nearly a mile because of discordant 
stratigraphic relations. Two small outcrops are readily found 
farther west by reason of the relations between the Ochre Moun- 
tain limestone and the Woodman formation. The most west- 
erly exposure occurs along the northeast side of the pronounced 
bench at an altitude of about 6,800 feet that lies between sum- 
mits 7233 and 6886, on the south side of Ochre Mountain. The 
Herat shale member of the Ochre Mountain limestone caps the 
bench and lies below (south of) the fault. The same member is 
also exposed above the fault just south of the summit of Ochre 
Mountain. The fault was not traced west of the bench, but 
it may continue along the west face of the mountain and join 
the second of the transverse faults, as no offsetting that can be 
attributed to it alone was recognised. The fault has its highest 
altitude and lowest dip at the 6,800 foot bench, and it decreases 
in altitude markedly to the east, where the dip appears to be 
considerably steeper. If it joins the other transverse fault at 
the west, it must decrease its altitude in that direction also. 
This variation in altitude is considered to be partly the result 
of original variations in dip and partly the result of later defor- 
mation, the eastward tilt caused by the western border fault 
(p. 61) being one of the most influential factors. 

The movement along the fault is estimated at about 2,500 
to 3,000 feet, the beds north of and above the fault moving east- 
ward. This measurement is based upon the correlation of 
structural features on the two sides of the fault. The large 
normal fault that forms the western boundary of the exposures 
of the Oquirrh formation along the Lincoln Highway east of 
Ochre Springs is correlated with a fault south of the fault with 
rather similar relations 1,000 feet west of benchmark 6163 at 



the north end of Clifton Flat; the' faults bounding the graben 
of Oquirrh formation composing hip 6439, north of the fault, 
are correlated with the faults that compose the graben of Ochre 
Mountain limestone north of hill 6519, south of the fault; and 
the fault 2,000 feet west of hill 7150, which limits the Woodman 
formation on the west, is correlated with the similar fault west 
of the bench at 6,800 feet. The stratigraphic throw shown by 
the Herat shale member of the Ochre Mountain limestone is 
also satisfied by a displacement of this magnitude. 

A second fault with low north dip crops out 1,500 feet south 
of the highest point on Ochre Mountain. It terminates on the 
west a band of Herat shale, and farther east in the amphitheater- 
like valley below the summit it is recognized by considerable 
crumpling in the massive beds of the Ochre Mountain limestone. 
On the western flank of the mountain it may be recognized at 
several places as a result of the relatively recent extensive erosion 
(pi. 7, A) and also by its termination of the belt of Woodman 
formation and the fault that bounds that formation. The 
amount of movement along this fault could not be determined, 
as the beds above it are all of the Ochre Mountain limestone. 
The altitude of the outcrops of the fault ranges from about 
6,650 to 7,250 feet. The highest point Is on the bench north of 
peak 7233. 

The last of the group of low-angle faults whose outcrops have 
a dominantly east-west trend is found on the north slope of 
Ochre Mountain. The chief outcrop of this fault is north of 
hill 6439, on the east side of the mountain. Here the fault 
strikes west-northwest and dips at a moderately low angle to the 
north. The footwal side is marked by extensive eiliciflcation. 
A down-faulted block of Pennsylvanian rocks is cut by the fault, 
and these beds south of the fault are shifted about 1,700 feet 
relatively east. A probable westward continuation of the fault 
was found about a mile to the west, just north of peak 7000. 
Other outcrops thought to represent this fault occur a mile still 
farther west, where, however, there are two faults with the same 
approximate strike as in the other outcrops but with a nearly 
vertical dip. Although these three outcrops were not traced 
into one another, it is thought that they are parts of the same 
fault, whose dip flattens eastward and upward. 

Southward-dipping transverse faults on Ochre Mountain. — A 
fault striking west-northwest and dipping at a moderate angle 
to the south is exposed on the south side of Ochre Mountain 
south of the bench at an altitude of 6,800 feet. To the north- 
west the fault abuts against a younger normal fault, and to the 
southeast it is covered by gravel, although it must be cut by 
the east-west transverse fault that bounds the block on the 
south. Several normal faults exposed north of the fault are 
clearly terminated by the transverse fault. 

An apparent measure of the throw along the fault is given 
by the positions of the Herat shale member of the Ochre Moun- 
tain limestone and the Woodman and Ochre Mountain contact 
on both sides of the fault. These show that the beds south of 
the fault have dropped vertically about 700 feet. A simple 
vertical movement, however, is impossible, because of the lack 
of correspondence of structure on the two sides of the fault, 
and particularly because of the absence, to the south, of any 
fault that might correspond with the normal fault east of the 
6,800-foot bench that forms the western boundary of the Wood- 
man formation. This, together with the erratic northeasterly 
strikes found at many places adjacent to the fault, suggest that 
it is a transverse fault. Its termination to the west by a normal 
fault that is in turn cut off by the northward-dipping transverse 
faults implies that it belongs to a different structural cycle from 
the other transverse faults on Ochre Mountain. :: ' 

A second parallel fault crops out 1,000 feet east of hill 6634, 
on the southwest spur of Ochre Mountain. The vertical com- 
ponent of its throw amounts to 250 feet, as shown by the Wood- 
man and Ochre Mountain contact on both sides of the fault, 



GEOLOGIC STBTJCTUBE 



75 



but a purely vertical movement is improbable because the 
displacements of two older normal faults require the movement 
along the fault to have been dominantly horizontal, the north 
side moving relatively eastward about 1,000 feet. 

Minor thrusts and fold on south side of Ochre Mountain. — Two 
minor thrusts and a small anticline are exposed on the south- 
western spur of Ochre Mountain that are thought to have been 
formed during the first structural cycle. The more westerly 
thrust crops out just east of the point at an altitude of 5,613 feet 
on the road along the west side of Ochre Mountain and is 
terminated eastward by a younger normal fault. The dis- 
placement of the thrust is unknown, as it is within the Ochre 
Mountain limestone. 

About half a mile to the southeast, another minor thrust is 
exposed. This fault separates beds high in the Guilmette 
formation, as shown by the lithology and by the presence of the 
large clam, Pycinodesma sp., from beds high in the Woodman 
formation. The stratigraghic throw thus amounts to nearly 
the thickness of the Woodman formation (about 1,500 feet), 
but the total movement along the fault is larger than this, as 
the low east dip of the fault nearly coincides with the dip of the 
bedding. The thrust is terminated at the northwest by a 
normal fault and at the southeast by the transverse fault that 
forms the southern boundary of the block. 

A minor anticlinal fold is exposed on the west side of hill 
6886, south of the summit of Ochre Mountain. It is terminated 
on the north by a transverse fault of the second cycle. 

Normal faults on Ochre Mountain. — By means of their rela- 
tions to the thrusts and transverse faults, the normal faults on 
Ochre Mountain are seen to belong to three different chrono- 
logic groups, corresponding to the first three structural cycles. 
Those of the first cycle are probably the most abundant. 

The two most westerly normal faults belong to the oldest 
group, as they are offset by a transverse fault of the second 
cycle. Both dip about 45° W. The throw along the western 
fault is unknown, but the eastern one drops the beds on its 
hanging-wall side about 2,000 feet. 

About 1;500 feet east of hill 6634, on the southwest spur of 
the mountain, another westward-dipping normal fault crops out. 
This belongs to the second structural cycle, however, as it cuts 
a transverse fault of the second cycle and is cut off by one of the 
third cycle. The throw along this fault amounts to about 2,000 
feet also, as is shown by the position of the upper contact of 
the Woodman formation on eaqh side. In the gulch that heads 
between peaks 7102 and 7182, on the ridge line of Ochre Moun- 
tain, the fault is cut by one of the northward-dipping transverse 
faults. Beneath the transverse fault, which has a very low dip 
at this point, the strike of the normal fault swings to east of 
north, its dip flattens and the beds on each side are crumpled. 
The compressive forces that caused the flat fault evidently were 
also partly relieved by some movement along the older fault. 
North of the intersection a north-south fault is exposed that 
appears to be a continuation of the normal fault to the south, 
but the known displacement along the transverse fault (about 
2,000 feet) makes a correlation impossible. At the north end of 
the mountain, along the continuation of this line of faulting, 
still another westward-dipping normal fault is found. The 
throw along the fault cannot be exactly determined but must 
be considerable, because the beds on the footwall side are hear 
the base of the Ochre Mountain limestone, and those on the 
hanging-wall side are rather high in the formation. This fault 
is terminated on the south by the northern of two northwest- 
ward-striking transverse faults. Adjacent to the transverse 
fault the strike of the normal fault swings to the southwest, and 
Its dip is notably latter — phenomena similar to those exhibited 
by the normal fault to the south at its intersection with a 
younger transverse fault. As the displacements along the 
branching transverse fault to the north and the flat transverse 



fault to the south are roughly compensatory, it is possible that 
the most northerly and southerly normal faults are segments of 
the same fault. 

Two north-south normal faults east of the 6,800-foot bench 
on the south side of the mountain are similar in the character 
of their displacement as well as in strike. Both are older than 
the transverse fault of the second cycle that is exposed in this 
region. The western of the two normal faults has a throw of 
nearly 2,000 feet; the eastern, about 500 feet. North of the 
third-cycle transverse fault that cuts these faults on the north 
only one north-south fault of large throw was recognized. This 
crops out about 2,000 feet east of the southward-trending ridge 
whose altitude is 7,150 feet. It is the continuation of the more 
westerly of the two normal faults south of the transverse fault, 
as it corresponds to that fault in stratigraphic relations. The 
more easterly of the two normal faults to the south is perhaps 
represented north of the transverse fault by a poorly exposed 
fault in the valley east of summit 7130. 

Three more normal faults are present north and northwest of 
hill 6516, on the southeast spur of Ochre Mountain. The 
westernmost one has a small downthrow to the east, as shown by 
the presence in the hanging wall of beds low in the Ochre 
Mountain limestone. The two more easterly faults are ex- 
posed on both sides of hill 6475, which is 2,000 feet north of hill 
6519. These two faults form the boundaries of a graben of beds 
high in the Ochre Mountain limestone, the Woodman formation 
being exposed east of the graben and basal beds of the Ochre 
Mountain limestone west of it. 

These two normal faults are cut by the most southerly of 
the northward-dipping transverse faults and north of the inter- 
section are shifted about 2,500 feet to the east. The depressed 
block between the faults (hill 6439) in the region to the north 
is made up of beds low in the Oquirrh formation, as shown by a 
small exposure of the Manning Canyon formation to the north. 
The graben is also cut by a second transverse fault farther 
north and shifted 1,750 feet westward. The beds in this seg- 
ment of the graben are also basal members of the Oquirrh for- 
mation and the upper portion of the Manning Canyon formation. 
The bounding faults of the graben converge northward in this 
region and are very nearly united where they are cut off by the 
Ochre Mountain thrust along the south side of the "window" 
described on page 73. They were not recognized on the north 
side of the "window." 

The faults that bound the graben are clearly older than 
the northward-dipping transverse faults and Ochre Mountain 
thrust of the third cycle. They appear to be unaffected, how- 
ever, by a minor transverse fault which is exposed 2,000 feet 
northwest of bench mark 6163 at the north end of Clifton Flat, 
and which was probably formed in the first stage of the second 
cycle. The two normal faults, therefore probably represent the 
normal faulting of the second cycle. 

Another normal fault of the second cycle with a northerly 
strike is exposed 1,000 feet west of bench mark 6163. This fault 
dips eastward and has a throw about equal to the thickness of 
the Ochre Mountain limestone, for beds of the Manning Canyon 
formation are found on the hanging wall and beds near the base 
of the Ochre Mountain limestone make up the footwall. The 
fault is not affected by the second-cycle transverse fault shown 
on the ridge to the west but is cut by the southern of the third- 
cycle transverse faults. The faulted segment is 3,000 feet to 
the east on the north side of the transverse fault, where it forms 
the western boundary of the mass of Oquirrh formation exposed 
along the Lincoln Highway. There has been renewed move- 
ment amounting to about 150 feet along this segment, as shown 
by the offsetting of the Oehre Mountain thrust (p. 72). 

Structural features east of the Lincoln Highway and south of the 
U.S. mine. — The most striking structural feature in the region 
east of the Lincoln Highway is a horst affecting the Ochre 



76 



GOLD HILL MINING DISTBICT, UTAH 



Mountain thrust, which is probably genetically related to the 
intrusion of the quartz monzonite stock. The fault that bounds 
the horst on the west extends northward from hill 6455, about 
1 Yz miles northwest of the town of Clifton and is a northern con- 
tinuation of the fault described on page 72. In this vicinity 
the fault appears to have at least three branches. A small mass 
of quartz monzonite has followed the fault zone for more than 
a mile, north of the branched portion, but a northern continu- 
ation appears to be represented by the fault 1,000 feet east of 
the highway in the region east of Ochre Springs. The beds on 
the footwall side of the block have been elevated relative to 
those on the hanging-wall side. Both to the north and to the 
south the beds of the central facies of the Oquirrh formation 
are exposed in the footwall and have been raised to altitudes 
several hundred feet higher than the Ochre Mountain thrust 
plane, which they normally underlie. North of hill 6455 beds 
above the thrust are found on the footwall side of the fault, but 
even here the thrust is considerably higher than west of the 
normal fault. 

This fault zone must also have been the site of movement 
before the Ochre Mountain thrust, for west of it the western 
facies of the Oquirrh' formation is above the thrust, but to the 
east the Ochre Mountain limestone has this position. The 
pre-thrust throw must have been large but cannot be closely 
estimated as the horizon in the Ochre Mountain limestone east 
of the fault is unknown. The post-thrust movement may have 
been somewhat smaller but certainly has amounted to at least 
several hundred feet and to the south may have been more than 
1,000 feet. The relations north of hill 6455 suggest that the 
post-thrust throw may have been variable along the strike. 

Several more or less east-west faults in the vicinity of hill 
6455 are cut by the normal fault zone, but their short extent 
and the considerable metamorphism of the adjacent beds make 
their true nature uncertain. They perhaps represent faulted 
segments of either the Ochre Mountain thrust or the north- 
ward-dipping transverse faults of the same age. 

The fault that bounds the horst on the east is exposed at two 
places. Near the Lucy L mine the central facies of the Oquirrh 
formation is brought into contact with Ochre Mountain lime- 
stone that lies above the Ochre Mountain thrust. The second 
exposure of the fault is west of the town of Clifton. Here the 
fault dips about 30° E. and has similar relations, except that 
the Ochre Mountain thrust is not exposed below the Ochre 
Mountain limestone in the hanging wall (sec. /-/') . The lime- 
stone, however, appears to have been originally continuous 
with the beds in the roof pendant northeast of the town, which 
definitely overlie the thrust. 

Two large faults cut the roof pendant northeast of Clifton. 
One of them strikes east of north and separates fossilif erous beds 
of the western facies of the Oquirrh formation on the east from 
Ochre Mountain limestone on the west. The fault is similar 
in relations to the normal faults of the second cycle on Ochre 
Mountain and is probably of that age. 

Both the normal fault and the outcrop of the Oquirrh for- 
mation are terminated on the south by a fault striking east- 
northeast and dipping, in its western portion, 60° N. This 
fault is difficult to trace toward the west in the Ochre Mountain 
limestone but seems to be marked by a zone of crumpling and 
minor overturned folds along the projected strike. These 
features suggest that the fault is one of the group of northward- 
dipping transverse faults that are exposed on Ochre Mountain. 

The Ochre Mountain limestone in the roof pendant has 
undergone minor folding. Section K-K' shows a shallow 
syncline that appears to be limited to the northwestern part of 
the pendant, but an asymmetric anticline to the east is more 
continuous. 

The exposures of the central facies of the Carboniferous for- 
mation immediately east of the Lincoln Highway and west of 
the westerly normal fault related to the intrusion lie immedi- 



ately beneath the Ochre Mountain thrust. Although meta- 
morphism and local gravel capping mask their structure con- 
siderably, it is clear that they are irregularly warped. The 
outcrop of Ochre Mountain limestone near the north end of the 
exposure of these rocks requires a local doming in the over- 
ridden rocks at that point. 

Minor faults are probably rather abundant in the beds near 
the quartz monzonite but are readily recognized only where 
prospect pits or mine workings provide suitable exposures. 
Thus several faults were recognized at the Lucy L mine (p. 141 
and pi. 13) and at the Wilson Consolidated mine (p. 139 and 
fig. 25). 

Faults near the U.S. mine. — Three faults are exposed in the 
vicinity of the U.S. mine. One of these, just south of the mine 
office, offsets the Ochre Mountain and Manning Canyon contact 
about 200 feet and is clearly earlier than the intrusion. The 
second fault, which strikes east-northeast and dips 60° 8., crops 
out 250 feet south of the portal of the main tunnel of the mine. 
It has beds low in the Oquirrh formation on its 'hanging wall 
and cuts across the Ochre Mountain and Manning Canyon 
contact in the footwall, indicating a throw of about 1,000 feet. 
The fault is rather poorly exposed at the surface and is seen 
underground only at the face of the most southerly working on 
the tunnel level. Beyond the fact that the fault is earlier than 
the intrusion its relative age is unknown. It is shown on plate 
3 as a normal fault of the first cycle but this is purely conjectural. 
As shown in section M-M' the fault appears to be nearly hori- 
zontal, but this is the result of the essential parallelism between 
the line of section and the strike of the fault. 

The third fault is northwest of the mine workings and forms 
the contact between the intrusive and sedimentary rocks. It 
cannot be recognized at the surface as the contact is covered by 
talus from the sediments above. Underground, however, the 
contact is exposed in the workings on the 234-foot level north- 
east of the shaft, where it is seen to be a fault striking about 
northwest and dipping 35° SW. On section M-M' the fault 
is shown as a normal fault, but the low dip perhaps makes this 
interpretation questionable. If the fault is considered to be 
normal, the throw may be about 200 to 300 feet; but if it is a 
reverse fault, the throw would necessarily be much greater. 
As no sign of the fault was observed along its projected course 
on the west side of Gold Hill Wash, it must die out in that 
direction; and therefore the smaller throw required by the 
normal fault makes that interpretation preferable. Several 
minor faults or shear planes were observed underground in the 
U.S. mine and are described on pages 158-160. 

Transverse fault north of Ochre Springs. — The structure in the 
flat west of the Lincoln Highway and northeast of Ochre Springs 
is obscure, as the outcrops of the Manning Canyon formation 
are low mounds covered by angular blocks of dark quartzite. 
The bedding is presumably nearly horizontal, as the exposures 
are found over a wide area. On the north side of the flat the 
low hills are composed of eastward-dipping beds of the Oquirrh 
formation. The discordance between the observed dip here 
and the inferred dip of the Manning Canyon outcrops in the 
flat suggests an east-west fault between them, and this sugges- 
tion is confirmed by the continuous exposures to the west, 
where a transverse fault forms the contact between the two 
formations. This fault is clearly older than the Ochre Mountain 
thrust, which is not affected by it. 

Northwesterly normal faults west of the Lincoln Highway and 
east of the main outcrop of the Ochre Mountain thrust. — There are 
probably several northwestward-striking normal faults in the 
region west of the Lincoln Highway that are not shown on 
plate 2, but the rather poor exposures and the lack of distinctive 
beds in the central facies of the Oquirrh formation prevent 
accurate mapping. 

The most westerly of the recognized faults of this group may 
be traced with minor interruptions from the north side of the 



GEOLOGIC STBUCTUEE 



77 



lat north of Ochre Springs to the northern boundary of the 
block. The fault dips to the west, one exposure of the fault 
plane showing a dip of 70°. Over much of its outcrop the 
Manning Canyon formation is exposed in the footwaE and beds 
low in the Oquirrh formation in the hanging wall. Farther north 
the relations are not so simple, as a result of intersections with 
other faults, and for the most northerly half mile of outcrop in 
this region, the fault forms the boundary between the over- 
riding and overridden rocks of the Ochre Mountain thrust. 
This portion of the fault is cut by younger northeasterly faults. 
The throw along the fault is about 300 feet. 

Two parallel faults to the northeast have both been traced 
for more than a mile by means of zones of disturbed strikes and 
dips. Both faults dip to the northeast, however. Their throw 
is between 200 and 300 feet, as nearly as can be estimated. 
Neither of these faults can be traced confidently much north 
of the road from Gold Hill to the Erickson ranch. 

Another fault with northwesterly strike may be traced from 
Gold Hill Wash Just south of the town of Gold Hill to the north- 
ern bdundary of the block. It dips to the southwest and appears 
to have its maximum throw of about 1,000 feet in the vicinity 
of the Cane Springs mine. The throw probably decreases to 
the north. 

Northeasterly faults west and northwest of Gold Hill. — Several 
northeastward-striking faults may be recognized in the region 
west of Gold Hill. Most of them are the youngest structural 
features in that region, as they cut the northwesterly normal 
faults, some of which in turn are younger than the Ochre 
Mountain thrust. The amount of displacement along these 
faults is small, but many of them are reverse faults. 

Locally the northeasterly faults appear to die out to the 
southwest. This feature is best shown about three-quarters of 
a mile west of Gold Hill. Here a northeasterly fault, which to 
the northeast clearly offsets a northwesterly fault, has merely 
warped a second northwesterly fault, and still farther to the 
southwest its influence cannot be recognized at all. 

Although the larger number of these faults are younger than 
the other structural features, some must represent an older 
generation- of faulting. This is shown about three-quarters of 
a mile south of bench mark 5885 on the Ferber Road, where one 
of these northeasterly faults is cut off sharply by a northwesterly 
fault. A parallel northeasterly fault a short distance to the 
north offsets the northwesterly fault, however. The north- 
easterly faults at this locality also show that there are two 
generations of northwesterly faults, as both of the northeasterly 
faults are younger than a northwesterly fault whose dip is 
45° SW. and whose throw is about 250 feet. 

Transverse fault at the northern border of the block. — Exposures 
immediately north and west of benchmark 5885 on the Ferber 
Road show that there must be a nearly east-west transverse 
fault in this region. The fault is now concealed through much 
of its course, however, by the tongue of quartz monzonite, or, 
locally, by gravel. In view of the known relation between the 
intrusion and preexistent faults in other parts of the quadrangle, 
it seems probable that this transverse fault may have controlled 
the intrusion of the tongue along the northern border of the 
block. 

The areal association of a nearly east- west transverse fault 
and northeasterly faults, both of which are relatively young, 
is similar to conditions near the Garrison Monster mine. 

Structural features in the vicinity of the Western Utah mine. — 
The most striking fault near the Western Utah mine is that 
marked by a linear outcrop of jasperoid replacement of fault 
breccia that passes through Gold Hill. Over most of its length 
the fault forms the contact between the Ochre Mountain lime- 
stone and the Manning Canyon formation. Its dip is about 
60° E. This is almost the same as the dip of the beds on each 
side of the fault in the vicinity of the mine, and it is only when 
beds of the Ochre Mountain limestone are traced to the north 



and found to change their strike to nearly east-west that the 
considerable throw of the fault is realized. The throw along 
the fault is unknown, but a minimum estimate, based on the 
thickness of Ochre Mountain beds terminated by the fault, is 
about 1,000 feet. 

On the eastern slope of the hill the relations of the Ochre* 
Mountain limestone and the Manning Canyon formation indi- 
cate the presence of a synclinal fold. Owing probably in large 
part to the fault described above, the dips on the western limb 
are much steeper than those on the eastern (sec. M-M'). The 
fold is cut by a fault striking N. 30° W. and dipping 65° W., 
whose throw is about 200 feet at its most southeasterly exposure 
but apparently increases to the northwest, as the displacement 
of the Ochre Mountain and Manning Canyon contact in that 
direction is obviously greater. The fault is cut by the east- 
ward-dipping fault that passes through Gold Hill, and it cannot 
be identified on the footwall side of that fault. A smaller fault 
to the north strikes N. 35° W. and dips 70° W. Its throw is 
roughly 150 feet. Both of these faults are older than the 
quartz monzonite intrusion. 

The remaining fault in this region is that which forms the 
contact between the sediments and the intrusive on the east 
side of the southern tip of the roof pendant. This fault cannot 
be recognized at the surface but was found in the tunnel 500 
feet south of the portal of the Copperopolis (Ida Lull) mine. 
In this tunnel the fault contact is exposed 75 feet from the por- 
tal and here strikes N. 12° W. and dips 60° W. The sediments 
on the hanging- wall side are. brecciated for 25 feet away from 
the fault, and the quartz monzonite is intensely crushed through- 
out most of its exposure in the tunnel. It ia uncertain how far 
north the fault forms the contact, because of the lack of expo- 
sures, and for this reason it is difficult to give even a minimum 
figure for the throw. 

Mutual relations of the structural features. — The Ochre Moun- 
tain block furnishes the most complete record of the structural 
history of the quadrangle. 

The first stage of the first cycle is represented by the minor 
thrusts and folds on the south side of Ochre Mountain and by 
the folds in the roof pendant north of Clifton. These localities 
are the only ones in which structural features of this age have 
been recognized. Normal faults belonging to the second stage 
are definitely present on the south side of Ochre Mountain, 
where they are cut by faults of the second cycle. The assign- 
ment of other normal faults in the block to this group is less 
certain. 

No major folds that were formed in the second cycle are 
shown in the block, but the prevailing easterly dip suggests 
that the region forms the western limb of a major anticline. 
Several minor transverse faults of this age were also recognized. 
The normal faults formed during the second stage of the cycle 
seem to be characterized by large throws. On the south side 
of Ochre Mountain two of them form a graben. 

The Ochre Mountain thrust is the major structural feature 
of the third cycle* The North Pass thrust of this age is not 
exposed in the block, but the beds of the central fades of the 
Carboniferous, which are above that thrust, are widely exposed, 
and the North Pass thrust must therefore underlie the region. 
Several low-angle transverse faults of this age are exposed on 
Ochre Mountain and offset some of the older faults. The nor- 
mal faults of the second stage of the third cycle are neither 
numerous nor of large throw. 

East-west transverse faults of the fourth cycle are found at 
both the north and south boundaries of the block. The north- 
ern transverse fault is coextensive with a number of north- 
eastward-striking faults, some of which are reverse faults, 
and the two kinds of faults are considered to be contempora- 
neous, on the basis of evidence from the vicinity of the Garri- 
son Monster mine, to the north. These faults cut off all the 
older ones. 



78 



GOLD HILL MINING DISTEICT, TJTAH 



Some large normal faults that affect the sedimentary rocks , 
of this block along the Lincoln Highway south of Gold Hill 
are younger than the structural features of the fourth cycle and 
are thought to be related to the quartz monzonite intrusion. 
They have no influence upon the present topography, however, 
and are therefore older than the western border fault along the 
west base of Ochre Mountain. 

DUTCH MOUNTAIN BLOCK 

The geographically more or less isolated mass of Dutch Moun- 
tain is bounded on the west by a gravel-filled valley that con- 
ceals a normal fault of large throw and on the south by a wedge 
of quartz monzonite that separates it from the Ochre Mountain 
block. 

The most pronouneed structural feature in the Dutch Moun- 
tain block is the northern continuation of the Ochre Mountain 
thrust, which can be traced, with only two interruptions, for 
the length of the block. North of Pool Canyon the thrust forms 
the contact between Carboniferous formations and earlier Paleo- 
zoic rocks (sees. C-C and D-D'), but south of the canyon 
the central facies of the Carboniferous lies beneath the fault 
(sec. E-E'). A transverse fault earlier than the thrust is the 
cause of the change in the overridden formations. Both the 
Carboniferous and the earlier Paleozoic rocks beneath the thrust 
are cut by numerous normal faults that are also earlier than the 
thrust. A few normal faults, however, are later, but some of 
these have utilized the lines of earlier faulting. At the north 
end of the block the thrust is also displaced by an east-west 
transverse fault. A group of faults striking east-northeast with 
either reverse or normal relations are associated with this trans- 
verse fault, and faults of similar strike are found to the south, 
where they also cut the thrust fault (sees. A- A' and B-B'). 
Relatively few notable faults have been found in the overriding 
block of Carboniferous rocks on the west slope of Dutch Moun- 
tain. Those that are present, however, give evidence of a com- 
plex history, in that the same fault has been the site of renewed 
movements of both reverse and normal character. The beds 
between the faults are generally folded on a small scale (sec. 
F-F'). 

Ochre Mountain thrust south of Pool Canyon, — The segment 
of the Ochre Mountain thrust east of the normal fault that 
terminated on the north the exposures of the thrust in the Ochre 
Mountain block (p. 73) must be concealed by the gravel west 
of the divide south of Dutch Mountain. The central facies of 
the Oquirrh formation crops out on hill 6286, north of the divide, 
and the western facies is exposed to the northwest and west. 
The exact position of the thrust in the intervening gravel- 
covered area is uncertain. The thrust outcrop is shifted at 
least a mile eastward by a northwesterly fault that crops out 
about 1,000 feet north of hill 6286. 

The offset segment north of the fault is the most southerly 
exposure of the thrust in the Dutch Mountain block. On the 
east side of hill 6566, three quarters of a mile northeast of bench- 
mark 5885 on the Ferber Road the thrust appears to be of 
minor throw, as Ochre Mountain limestone forms both walls. 
The only difference apparent between the limestones on the 
two sides of the fault is the noticeably greater metamorphism 
of the beds below the thrust. The magnitude of the fault is 
shown, however, by the fact that the Ochre Mountain limestone 
above the thrust is conformably overlain by the western facies 
of the Pennsylvanian formations, but below the fault it is asso- 
ciated with the central facies. Sandstone beds belonging to 
the basal portion of the central faeies of the Oquirrh formation 
occur beneath the thrust less than 1,000 feet north of the most 
southerly exposure of the thrust, and the Woodman formation 
takes the place of the Ochre Mountain limestone immediately 
above the thrust. These relations continue northward for about 
a third of a mile, to a point where the outcrop of the thrust is 



interrupted by the mass of quartz monzonite at the head of Pool 
Canyon. 

Ochre Mountain thrust in Pool Canyon.- — The thrust is also 
exposed northeast of the quartz monzonite mass in Pool Canyon, 
where the Madison limestone lies above the thrust, and meta- 
morphosed dolomites, thought to belong to the Laketown dol- 
omite, below it. The altitude of the thrust also differs on the 
two sides of the intrusive, being about 300 feet lower to the 
northeast. A transverse fault that follows Pool Canyon and 
may be called the Pool Canyon transverse fault appears to have 
produced these changes in the relations of the thrust. The 
contact between this transverse fault and the thrust is concealed 
by the quartz monzonite, but it seems certain that the transverse 
fault is older, for it cannot be found in the beds overlying the 
thrust northwest of the quartz monzonite area. 

The way by which a change in the formations above the thrust 
was accomplished is shown by the exposures of the Woodman 
formation that surround the quartz monzonite. Northeast of 
the intrusion the Woodman formation conformably overlies the 
Madison limestone and dips at low angles to the north and west. 
At the northwestern tip of the intrusion, which is in line with 
the prolongation of the transverse fault, the beds of the Wood- 
man show abundant minor faulting and shattering and have 
locally erratic dips. To the southeast, along the border of the 
intrusion, the bedding is concealed in most places but is clearly 
vertical at the summit of Woodman Peak. From this point 
southeastward the dip changes to steep southeast and the Ochre 
Mountain limestone is found above the Woodman. In the 
Ochre Mountain the dip continues to decrease to the southeast 
and passes through horizon tality to a low northwesterly dip 
where the contact of the Oehre Mountain and the Woodman is 
again exposed on the ridge south of Pool Canyon; There are 
thus a sharp anticline and a low syncline southwest of the intru- 
sive and a gentle monocline northeast of it. 

These relations indicate that the overriding thrust plate 
suffered a considerable disturbance where it crossed the older 
transverse fault. There must have been some rupturing in the 
thrust plate along the line of the older fault to account for the 
difference in structure shown on the two sides of Pool Canyon, 
but the absence of a major fracture in the Woodman formation 
along the prolongation of the transverse fault suggests strongly 
that the greater part of the variation was accomplished by 
warping. 

It seems improbable that the Pool Canyon transverse fault 
could have exerted so strong an influence upon the thrust unless 
the thrust plate were moving over a surface whose topography 
had been influenced by the transverse fault. This conclusion 
appears to be confirmed by the fact that the greater disturbance 
in the beds above the thrust is found southwest of the transverse 
fault, the side that is about 300 feet higher. As the sandstones 
and limestones making up the Oquirrh formation southwest of 
the transverse fault are much less resistant to erosion than the 
massively bedded dolomites to the northeast, it would appear 
that relatively little time could have elapsed between the forma- 
tion of the transverse fault and the Oehre Mountain thrust. 

Ochre Mountain thrust between Pool Canyon and the Garrison 
Monster mine.— North of Pool Canyon the thrust may be read- 
ily traced without serious interruption to the north aide of Dutch 
Mountain. The Madison limestone overlies the thrust in this 
series of exposures, but various formations of pre- Devonian age 
underlie it. From Pool Canyon to the south side of Tribune 
Gulch the outcrop of the thrust changes its trend from east to 
northeast, and in this distance it is cut by several faults whose 
throws are less than 100 feet and which are not shown on plate 
3, On the south side of Tribune Gulch the thrust is cut by two 
faults with northeasterly strikes. The more southeasterly of 
these has caused the repetition of the thrust outcrop on the 
ridge at an altitude of 6,555 feet. 



GEOLOGIC STRUCTTJBE 



79 



A northwesterly fault that follows Tribune Gulch offsets the 
thrust about 1,000 feet to the northwest. The vertical move- 
ment along this fault required to accomplish the observed offset 
of the thrust is only 300 feet, but the displacement shown by the 
beds beneath the thrust requires a vertical drop of more than 
600 feet. This discordance suggests that there were two stages 
of movement along the fault, but the observed relations might 
equally well be explained by a dominant horizontal movement. 
This explanation is probably the correct one, as exposures of the 
fault in Royal Gulch, to the north, exhibit pronounced horizon- 
tal striae (p. 82). 

Another large offset in the thrust outcrop is found in the 
vicinity of the Spotted Fawn mine. In this region several 
branches of the Spotted Fawn normal fault cut the thrust. 
The vertical displacements of the thrust along these faults are 
small, but some of them have throws of 2,000 feet or more in 
the overridden rocks. These faults are unlike the fault de- 
scribed in the preceding paragraph, however, in that the dis- 
cordances cannot be reconciled by postulating horizontal 
movement along the faults, and they must therefore have been 
active at more than one period. 

North of the Spotted Fawn mine the thrust is interrupted at 
only a few places by minor faults and may be readily traced to 
a point within a short distance west of the old camp of the 
Garrison Monster mine, where it is cut off by one of the faults 
in the Garrison Monster transverse fault zone. Throughout 
this distance Madison limestone lies above the thrust and Upper 
Cambrian dolomite below it. 

The Madison limestone above the thrust throughout this 
region dips at very nearly the same angle as the thrust. The 
progressive thinning of the limestone northward, however, shows 
that there is a slight discordance. The only place where a 
notable discordance was observed is near the north end of the 
main outcrop of the thrust, in the region between it and the 
exposures of the thrust in Royal Gulch. In this region, which 
is considerably faulted, there is a sharp asymmetric anticline 
in the Madison limestone that has resulted in a considerably 
greater thickness of the limestone than normal being present 
above the thrust. 

Ochre Mountain thrust near Garrison Monster mine, — North 
of the Garrison Monster transverse fault a thrust that is 
probably the continuation of the Ochre Mountain thrust is 
exposed a short distance west of the new Garrison Monster 
camp. In this region the Woodman formation lies above the 
thrust and Upper Cambrian dolomites beneath it. The thrust 
may be traced northward for more than a mile, beyond which 
it is concealed by gravel. 

" Window" in Royal Gulch. — The erosion of Royal Gulch on 
the north slope of Dutch Mountain has provided additional 
exposures of the Ochre Mountain thrust a short distance west 
of the main outcrop (sees, B-B' and C—C) . In this region the 
thrust is cut by northwesterly faults that appear to be continu- 
ations of the faults that cut the thrust in the vicinity of the 
Spotted Fawn mine. These faults cause offsets of the thrust 
outcrop of a few hundred feet, but like their probable continua- 
tions near the Spotted Fawn mine, have very different effects 
in the overridden formations. At least two northeasterly faults 
related to the Garrison Monster transverse fault also cut the 
thrust in this region. 

Either the Fish Haven dolomite or the Laketown dolomite 
underlies the thrust throughout a greater part of the "window." 
In several places the contact between these two formations is 
transgressed by the thrust. Madison limestone lies immediately 
above the thrust throughout the exposure. 

Ochre Mountain thrust along north edge of Dutch Mountain. — At 
several places west of the mouth of Accident Canyon, on the 
north side of Dutch Mountain, a low-angle fault is exposed 
separating lower Paleozoic formations, ranging from Cambrian 
to Devonian, from the overlying Woodman formation. The 



gravel that covers much of the area enclosing the exposures of 
the fault conceals its outcrop for considerable distances. The 
fault is thought to be a westward continuation of the Ochre 
Mountain thrust, as its stratigraphic relations are the same as 
those shown along the east side of Dutch Mountain, and just 
east of the mouth of Accident Canyon the probable continuation 
of the fault is less than half a mile from outcrops of the thrust 
in the "window" in Royal Gulch. The thrust has a pronounced 
northerly dip in this region, which is probably due to the close 
proximity of the westward extension of the Garrison Monster 
transverse fault, as the dip appears to be steepest in those out- 
crops nearest the transverse fault (sec. F-F'). Several normal 
faults cut the thrust to the northwest, and one of them ter- 
minates the series of exposures on the west. 

Thrust plates associated with Ochre Mountain thrust. — Locally 
relatively thin thrust plates are associated with the Ochre 
Mountain thrust. They ire in some respects similar to those 
found on Ochre Mountain (p. 73) and to those related to 
the North Pass thrust in North Pass Canyon (pp. 67-68). One 
of these plates, composed of Upper Cambrian dolomite, lies 
beneath the easternmost exposure of the main thrust north of 
the Spotted Fawn mine. Bedding planes are preserved in 
many places in the plate, and their discordance not only with 
the bedding in the Middle Cambrian beneath but also with 
both the upper and lower contacts of the plate shows conclu- 
sively that the block has a tectonic origin. The plate has a 
thickness of about 300 feet on the steep slope north of the 
7,333-foot point on the ridge line of Dutch Mountain and near 
the Garrison Monster mine, but elsewhere it Is much thinner. 
It appears to have a rather slight areal extent, as it was not 
recognized in the "window" of Royal Gulch, In Royal Gulch, 
however, the Upper Cambrian is beneath the thrust in its 
normal stratigraphic position on the west limb of a northeast- 
ward-trending anticline. It seems probable that the thrust 
plate of dolomite is a continuation of these beds which has 
overridden the less resistant underlying Middle Cambrian 
during the period of overthrusting. The relations are closely 
similar to those in North Pass Canyon, where the presence of 
plates of resistant rocks beneath the main North Pass thrust 
is considered to indicate that both the main thrust and the 
plates moved forward over an older erosion surface (p. 57). 

Several minor thrusts in the rocks above the Ochre Mountain 
thrust are exposed in the vicinity of the Garrison Monster mine. 
Some of these thrusts in the Woodman formation can be seen 
along the Lake Bonneville beach at 5,200 feet, west of the portal 
of the tunnel (altitude 4,894 feet) at the new camp. One of 
these thrusts (pi. 7, D) clearly reveals minor folds in the over- 
ridden beds. Another thrust, which encircles the summit 
between the old and the new Garrison Monster workings, 
brings Madison limestone over the Woodman formation. It 
may be a continuation of one of the minor thrusts exposed to 
the north. 

Appearance of Ochre Mountain thrust. — In almost all places 
it is difficult to determine the precise horizon of the thrust, and 
the location shown on the map represents a halfway point 
between beds that may be recognized as belonging to formations 
above and below it. The intervening rock, which in many 
places reaches a thickness of 20 feet and is rarely less than 10 
feet, is so thoroughly recrystallized that it is impossible either 
to "distinguish characteristic sedimentary structure or to choose 
a dividing plane. Angular fragments of any size, or a fault 
breccia, can be distinguished megascopically in only a few 
places, although there is, in many places, a slight streakiness 
parallel to the thrust. A typical specimen from Royal Gulch is 
a light grayish-brown rock in which thin bands and lenses of a 
white coarser-grained calcite alternate with thicker bands of 
grayish-brown fine-grained carbonate. The cleavage planes of 
the white calcite reach an eighth of an inch in diameter, and 
locally tiny remnants of a bluish calcite may be distinguished 



m 



GOLD HILL MINING DISTRICT, UTAH 



within them. Optical tests on crushed fragments of the finer- 
grained material indicate that it is in large part dolomite. 
Under the microscope the coarsely crystalline calcite is seen to 
be the older mineral. Individual crystals are rather turbid and 
are commonly twinned. Curving cleavage planes are strongly 
developed and are characteristic of this stage. The white cal- 
cite is embayed and veined by a clear, unstrained carbonate 
mineral, most of which, as noted above, is probably dolomite. 
This is the material that is grayish brown in the hand specimen, 
and the microscope shows that the color is due to the presence 
of a brown mineral, probably iron oxide, around the borders of 
jthe dolomite crystals. Similar brown material surrounds frag- 
ments of the older calcite where it is in contact with the younger 
crystals. A few laths of sericite are present in some places with 
the iron oxides. Small blebs and stringers of fine-grained 
quartz show intense shearing and undulose extinction. The 
relation of the quartz to the white calcite is not clear, but it is 
clearly veined by the dolomite. 

,. The features observed in this specimen are interpreted as 
follows: The white calcite crystals are thought to be sheared 
and enlarged crystals of the original limestone. Enlargement 
seems required, as they are of larger diameter than any seen in 
any of the unaltered limestones. The quartz stringers and 
lenses are considered to have formed as a result of the shearing 
of cherty and sandy portions of the limestone. Partial recrys- 
tallization of the quartz and enlargement of the white calcite 
crystals resulted in their having somewhat anomalous relations 
to each other. These two components of the rock mark the 
initial stages of the thrusting. As the movement continued, 
shearing became localized along planes parallel to the fault, and 
on these planes recrystallization accompanied by expulsion of 
the impurities in the original grains occurred, resulting in the 
formation of the clear unstrained crystals with their boundaries 
of iron oxides and sericite. The presence of so much dolomite 
apparently indicates that there must have been some transfer 
of material during recrystallization, the magnesium being 
derived from the overridden dolomites. Such a transfer was 
probably accomplished by circulating solutions, as the absence 
of extensive cataclastic structure argues against anhydrous 
conditions during the thrusting. 

Folding of Ochre Mountain thrust. — Variations in the altitude 
of the thrust outcrop that are independent of later faulting 
indicate that it has been warped into several minor folds. A 
well-defined anticline is shown by the thrust north of the 
Spotted Fawn mine, the altitude of the thrust outcrop increasing 
from 6,600 feet or less to about 7,200 feet on the divide between 
Spotted Fawn Gulch and Busby Gulch, and decreasing west of 
the divide, as shown by the "window" in Royal Gulch and the 
Madison limestone outcrops in the gulches to the south. The 
anticlinal axis must strike about northeast and be located 
approximately along the ridge line of Dutch Mountain. 

Beneath Accident Canyon the thrust must have an altitude 
of 4,500 feet or less, as shown by the absence of exposures of 
Madison limestone south of the east-west fault that extends 
along the north side of the mountain here. Farther west, how- 
ever, the thrust is again exposed at an altitude of about 5,100 
feet, showing that a synclinal fold must occur in the vicinity of 
Accident Canyon. 

The folds in the thrust are thought to be related to the Gar- 
rison Monster transverse fault (p. 59) . 

Magnitude of the thrust. — The distance between the eastern- 
most and westernmost exposures of the thrust is about 4 miles, 
slightly less than was found in the Ochre Mountain block (p. 74) . 
This is a minimum figure for the amount of movement along 
the thrust, however, and the total throw must be much larger. 

Pool Canyon transverse fault. — The existence of a large fault 
in Pool Canyon is shown by the occurrence of lower Paleozoic 
formations beneath the Ochre Mountain thrust on the north 



side of the canyon and of Carboniferous formations on the 
south side. Exposures of the fault, which has been called the 
Pool Canyon transverse fault, are poor and of small extent, 
most of its projected course being concealed either by gravel 
or by younger intrusive rocks. 

The fault does not cut the rocks above the thrust, but its 
intersection with the thrust in the northwestern part of Pool 
Canyon is concealed by a mass of quartz monzonite. The 
fault is exposed for a distance of about 2,000 feet in the central 
part of the canyon, but the extensive metamorphism of sedi- 
ments on each side makes it difficult to distinguish the fault 
plane. A small intrusion is present along the fault in this 
region, and its linear northern boundary is thought to coincide 
with the fault plane. A prospect pit at this locality shows 
that the contact dips steeply to the south. In the lower reaches 
of Pool Canyon another body of quartz monzonite has been 
intruded along the fault, but its continuation is shown by the 
beds exposed on each side of the canyon. 

Another group of outcrops is found in the vicinity of the 
Rube mine. The westernmost outcrop of the fault in this 
region is just north of hill 5057. Here the Prospect Mountain 
quartzite north of the fault is in contact with Ochre Mountain 
limestone. A prospect tunnel on the northwest side of the low 
ridge apparently parallels the fault immediately to the south. 
The tunnel shows thoroughly crushed rock but does not give 
any definite indication of the dip of the fault at this point. 

A small outcrop of Ochre Mountain limestone about* 1 ,200 
feet to the northwest, which is surrounded by. gravel, indicates 
that the transverse fault must be offset to the north at least 
700 feet. The fault causing the offset is shown on the map with 
a north-south strike, but there is no evidence to prove that it 
may not strike northeast. Another offset of about the same 
amount is required by exposures of the transverse fault west 
of the Rube mine. This offset is thought to be the result of a 
westward-dipping fault exposed in the Ochre Mountain lime- 
stone on the Ruby claim, to the south. If this fault really 
is the one causing the offset and the movement along it is of 
the normal type, the transverse fault must dip to the south, 
as it does In Pool Canyon. It is possible, however, that the 
offsetting fault may have a northeast strike; if so, it would crop 
out beneath the gravel of Gold Hill Wash. 

Another offsetting fault must be present in the gravel-covered 
slope west of hill 5556, east of the Rube mine. This fault must 
be older than the intrusion of quartz monzonite, as no trace 
of it was found to the south. East of the offset the transverse 
fault cannot be exactly located for some distance, but its 
approximate position is shown southeast of hill 5556 by an 
isolated outcrop of Pennsylvanian limestone in close proximity 
to one of Prospect Mountain quartzite. There are probably 
no further offsets concealed by the gravel in the area to the 
east. The easternmost exposure within the quadrangle is found 
about half a mile west of the Christmas mine. Here the trans- 
verse fault is cut off by a fault trending nearly due north, but 
the amount of displacement is not known. 

There is no evidence by which the amount of movement 
along the Pool Canyon transverse fault can be determined. 
; The stratigraphic throw ranges from 10,000 to 20,000 feet, as 
shown by the formations on each side. These figures, however, 
do not take into account the facts that the. Carboniferous rocks 
south of the fault belong to the central facies and lie above the 
North Pass thrust, and that the lower Paleozoic formations to 
the north appear to be a continuation of the similar beds south 
of North Pass Canyon that are below the North Pass thrust: 

Relation of Pool Canyon transverse fault to North Pass thrust. — 
The occurrence of the central facies of the Carboniferous for- 
mations on the south side of the Pool Canyon transverse fault 
shows that the North Pass thrust must have extended into this 
structural block, but the quartz monzonite intrusion and the 



GEOLOGIC STRTJCTUBE 



81 



gravel that occurs along the eastern portion of the block com- 
bine to conceal its outcrop. As the rocks north of the trans- 
verse fault are similar to those that were overridden by the 
North Pass thrust, the transverse fault marks the northern 
limit of the present exposures of the North Pass thrust plate. 

If the suggestions made on page 78 are correct' — that the 
Ochre Mountain thrust moved over the then existing surface 
and is only slightly younger than the Pool Canyon transverse 
fault— the transverse fault must have limited the thrust plate 
on the north at the time of thrusting, for otherwise the segment 
of the North Pass thrust plate north of the Pool Canyon fault 
would have been preserved beneath the Ochre Mountain thrust. 
This conclusion, together with the apparent limitation of the 
North Pass thrust on the south by a parallel transverse fault 
(p. 57), indicates that the North Pass thrust had a relatively 
slight extent along its strike in comparison with the amount 
of horizontal movement that took place along it. 

Folding in rocks beneath Ochre Mountain thrust. — The lower 
Paleozoic rocks along the eastern front of Dutch Mountain 
form the western limb of a major anticline. The axis of the 
fold probably roughly coincides with the eastern base of the 
mountain, to judge from the prevailing flat dips and local east 
dips found there. The scattered exposures of the rocks beneath 
the thrust along the northern base of the mountain suggest that 
a minor anticline and syncline are superposed on the major 
fold in this region. These folds appear to be independent of 
the warping shown by the Ochre Mountain thrust. 

Faulting below Ochre Mountain thrust iouth of Pool Canyon 
fault. — South of Pool Canyon the rocks underlying the Ochre 
Mountain thrust belong to the central facies of the Carbonifer- 
ous. The two most prominent faults in this region, which 
strike west-northwest, have acted to enclose a band of the 
Oquirrh formation between two bands of the Ochre Mountain 
limestone. Minor faults, striking west of north, are made 
apparent in the central belt by offsets of the lower contact of 
the Oquirrh formation and are, in part at least, younger than 
the west-northwest fault, which they displace. In the central 
belt the Oquirrh formation and the Ochre Mountain limestone 
are separated by less than 100 feet of black shale that has been 
referred to the Manning Canyon formation. Such a thickness 
is much less than that normally shown by the Manning Canyon, 
and it seems probable that here, as in some other places, it has 
been thinned by overriding during thrusting. The thinning at 
this place may perhaps be correlated with a marked thickening 
to the southwest, just south of the Ferber Road. The two 
west-northwest faults are parallel in strike to the large trans- 
verse fault in Pool Canyon and are probably subsidiary frac- 
tures developed at the same time as the main fault. The 
northern of the two faults has been the site of movement 
sufficient to give an apparent vertical throw of at least 4,000 
feet. 

Spotted Fawn normal-fault zone. — A branching normal fault, 
which separates Lower and Middle Cambrian beds on the 
northeast from younger formations on the southwest, extends 
in a southwesterly direction from the vicinity of the Spotted 
Fawn mine. It may be traced to the north side of Tribune 
Gulch, beyond which it is concealed by gravel. 

At the most southeasterly exposures, near the mouth of 
Tribune Gulch, the fault separates Prospect Mountain quartzite 
on the northeast from Upper Cambrian dolomite on the south- 
west. Though poorly exposed, it is, without much doubt, a 
single fracture. On the small 5,384-foot hill a 40-foot lenticular 
dike of quartz monzonite has been intruded along the fault, and 
a prospect pit on the southwest side shows the dip of the contact 
to be 58° SW. It is probable that this figure approximates the 
dip of the fault plane in this region. The fault continues as a 
single fracture without change in stratigraphic relations for 
more than 4,000 feet to the northwest. It is offset from 100 to 
400 feet by four northeastward-striking faults that dip to the 



northwest. In all four places the outcrop of the fault is shifted 
to the southwest in the hanging wall of the younger faults, 
indicating a reverse movement along them. 

North of the fourth offset, at a point where the fault is 
crossed by latitude 40 Q 12'30", it splits into two branches — a 
minor one separating the Prospect Mountain quartzite from 
the Cabin shale and the Busby quartzite and a main branch 
separating those two formations from the Upper Cambrian. 
The contact between the shale and the Busby quartzite in the 
block between the two branches is clearly the result of over- 
riding by the quartzite, as shown by the discordance in dip 
between the two formations and also by the absence of the 
characteristic concretionary bed that normally occurs at the top 
of the shale. 

About 800 feet north of the junction both branches are 
shifted about 100 feet to the west by the northeasterly reverse 
fault that causes a repetition of the outcrop of the Ochre Moun- 
tain thrust (p. 78). Two more branches are found north of the 
offsetting fault — one relatively small, within the Busby quartz- 
ite, and one that brings in a wedge of Middle Cambrian lime- 
stone between the Busby quartzite and the Upper Cambrian. 
The latter branch and the main branch are, a short distance 
father north, shifted about 300 feet to the east by still another 
northeasterly fault, along which, however, the displacement is 
apparently of the normal type. The two eastern branches can- 
not be confidently distinguished north of the intersecting fault, 
but there are two nearly parallel faults to the west, which are, 
in all probability, new branches. The throw on both of them 
is small, as is shown by the displacement of the Fish Haven 
dolomite. 

Several of the branches cut the Ochre Mountain thrust. 
Along three of them the displacement of the thrust is notably 
at variance with the displacement of the beds beneath the 
thrust, indicating that the Spotted Fawn fault zone has been 
active during more than one structural cycle. Thus the most 
southwesterly branch that cuts the thrust drops the thrust 
several hundred feet to the southwest and drops the beds 
beneath the thrust an approximately equal amount to the north- 
east. The main branch of the fault that crops out a few hundred 
feet west of the Spotted Fawn shaft at 6,543 feet has a throw of 
200 feet or less as measured by the thrust and at least 2,000 feet 
as measured beneath the thrust. The most easterly fault has 
similar relations. It offsets the thrust less than 100 feet, but 
in the beds beneath the thrust it separates Middle Cambrian 
limestone from Cabin shale and Busby quartzite — relations 
indicating a much larger throw. 

The total throw along the Spotted Fawn fault zone in the 
beds beneath the thrust amounts to about 4,000 feet. 

Faults in Royal Gulch "window." — The branches of the 
northwesterly Spotted Fawn fault are also exposed in Royal 
Guleh. Here, as on the east side of Dutch Mountain, they have 
been the sites of post-thrust as well as pre-thrust movement. 
There are in addition several northeastward-striking faults 
younger than the thrust. Some of these cut the post-thrust 
portions of the northwesterly faults, but others are cut by them. 

The northwesterly continuation of the main branch of the 
Spotted Fawn normal fault illustrates most of the complexities 
of the faulting. Near the head of Royal Gulch it cuts the Ochre 
Mountain thrust and drops the portion to the southwest several 
hundred feet. It also offsets the Madison limestone above the 
thrust in sueh a way as to exhibit the local flexure in that 
formation (p. 79). Near the prospects on the north side of 
Royal Gulch it is cut and offset by a northeasterly fault with a 
low northwestward dip. The faulted segment causes a repetition 
of the Ochre Mountain thrust outcrop, which is 100 to 200 feet 
lower on the southwest side. Beneath the thrust, however, 
the beds on the northeast side have been dropped; Upper 
Cambrian dolomite is exposed on the northeast immediately 
below the thrust, and Laketown dolomite on the southwest, 



82 



GOLD HILL MINING DISTRICT, UTAH 



showing a pre-thrust throw that amounts to 1,000 feet or more. 
Near the mouth of the gulch the fault shifts a northeasterly 
fault several hundred feet. The northeasterly fault is similar 
in strike and dip to the one that cuts the Spotted Fawn fault 
to the southwest. 

The probable continuation of the fault in Tribune Gulch 
whose movement is thought to have been dominantly horizontal 
(p. 79) is exposed in Eoyal Gulch. The tunnel at 5,593 feet 
cuts this fault and follows it for several feet. Throughout this 
distance the polished fault plane shows deep horizontal grooving. 

Minor faults between Spotted Fawn and Pool Canyon faults, — 
The triangular area of rocks ranging from Upper Cambrian to 
Silurian between the Spotted Fawn normal fault, the Pool Can- 
yon transverse fault, and the Ochre Mountain thrust show wide- 
spread minor faulting. Such faulting is apparently concen- 
trated in the regions in which the Fish Haven dolomite crops 
out (pi. 2), for this dolomite is one of the few reliable horizon 
markers by which faults may be distinguished from zones of 
shattering. It is probable that more intensive field work would 
show the presence of additional outcrops of the Fish Haven 
dolomite in this region, especially in the strip of country between 
the two northeasterly faults on the two sides of hill 6279, on 
the south side of Tribune Gulch. 

The faults in this triangular area strike in three general direc- 
tions. The northeasterly faults are the youngest and include 
both reverse and normal faults. The other faults strike either 
north or west of north. The relations between these two groups 
are not conclusive, but farther north those striking west of 
north appear to be the younger. They are for the most part 
older than the thrust, however, but along some of them there 
has been renewed movement after the thrusting. These faults 
are essentially parallel in strike to the large normal fault just 
described and may have been formed at the same time. The 
alternate hypothesis, however, that some of the faulting was the 
direct result of the overthrusting whereby original slight eleva- 
tions of the overridden surface were eliminated by being down- 
faulted, is suggested by the position of the outcrops of the Fish 
Haven dolomite on the south side of Tribune Gulch. 

Faults beneath the thrust north of the Spotted Fawn fault, — 
The rocks beneath the thrust on the footwall side of the Spotted 
Fawn fault are all of Cambrian age, chiefly Lower and Middle 
Cambrian. The Prospect Mountain quartzite forms a large 
part of these rocks, and its uniform character and poor exposures 
prevent any attempt to correlate the faults exposed at its upper 
contact with those along the east base of Dutch Mountain in 
the places where shale members crop out. The exposures of 
the shale are relatively few, and are all partly concealed by 
gravel, but they show the same kinds of faults as are found along 
the upper contact of the quartzite. One of the largest of the 
faults along the east base of Dutch Mountain terminates on the 
south the exposure of the shale member north of the road to the 
Spotted Fawn mine. The shale member was not recognized 
south of the road, and the throw along this fault must therefore 
be about 1,000 feet. 

In the interval between the upper boundary of the Prospeet 
Mountain quartzite and the Ochre ' Mountain thrust several 
faults have been recognized by means of the distribution of the 
Cabin shale and Busby quartzite. To the north, in the wide 
outcrop of undifferentiated Middle Cambrian rocks, exposures 
are poor and faults are difficult to trace. 

Several faults are exposed in the vicinity of the Spotted Fawn 
mine in addition to the Spotted Fawn normal faults. One of 
these is parallel to and on the north side of the canyon bottom 
southeast of- the mine workings. It is unusual 'in that it is one 
of the few faults on Dutch Mountain that dips to the northeast. 
The fault drops the thrust 150 feet on the east side and causes 
a somewhat smaller but similar displacement of the upper con- 
tact of the Prospect Mountain quartzite beneath the thrust. 
Between these two points, however, the Cabin shale forms the 



footwall of the fault, and in the hanging wall are found succes- 
sively Cabin shale, Busby quartzite, and a portion of the Aber- 
crombie formation, representing vertical displacements ranging 
from to about 1,000 feet. This, combined with the presence 
of Middle Cambrian limestones beneath the thrust on the foot- 
wall side of the fault, implies that there must have been some 
pre-thrust movement along this fault, in spite of the apparent 
concordance in throw at its intersections with the thrust and 
with the upper contact of the Prospect Mountain quartzite. 

The exposures in the main tunnel of the Spotted Fawn mine 
indicate the presence of a minor thrust that is not readily recog- 
nized on the surface. The rocks exposed are highly metamor- 
phosed beds of the Busby quartzite. The exposures on the 
surface and in two shallow shafts above the tunnel (see fig. 27), 
however, are Middle Cambrian limestones. The attitude of 
the two sets of exposures, together with the details of their 
distribution, show that they must be separated by a nearly 
horizontal fault. This fault is probably represented by 6 feet 
of breccia exposed at the top of the vertical raise in the northern 
branch of the tunnel, and its outcrop is probably just below the 
dump 100 feet north of the tunnel portal. The fiat fault appears 
to offset the most easterly branch of the Spotted Fawn normal 
fault about 100 feet. No such offset was found along the east- 
ward-dipping fault, and it is possible that the minor thrust is 
earlier. 

Other evidences of horizontal movement in this region are 
abundant. In the tunnel the individual beds of quartzite are 
truncated by minor fiat faults. Even more striking is the local 
overriding of the Cabin shale by the thin strip of Busby quartzite 
exposed in the footwall of the east branch of the Spotted Fawn 
fault. The best example of this feature was found about 1,400 
feet east of south from the cabin at the Spotted Fawn. 

There are undoubtedly many other nearly fiat faults in the 
overridden formations between the Spotted Fawn and Garrison 
Monster mines, but extremely detailed work would be necessary 
to recognize and trace them. The unusually small thickness 
of the Busby quartzite and Cabin shale in Busby Canyon 
(pp. 7-8) points to this conclusion, as does the difficulty that 
was met in attempting to reconcile contradictory evidence as to 
the amount of displacement along many of the minor faults. 

Only two other faults in the overridden block, south of the 
Garrison Monster mine, merit detailed description. One of 
these is the northwesterly normal fault about 1,000 feet south 
of the point at 6,785 feet and 2,500 feet northeast of the Spotted 
Fawn mine. This fault is relatively small, for the throw corre- 
sponds to a vertical drop of only 100 feet on the southwest side. 
Its chief interest lies in the fact that it cuts three nearly north- 
south normal faults, indicating that there is represented on 
Dutch Mountain a period of normal faulting deinitely earlier 
than that of the prevailing northwesterly faults. 

The second fault, or rather fault zone, strikes northwestward 
from peak 6264, on the north side of Busby Gulch. This zone 
is cut by several northeasterly faults, the largest of which is a 
reverse fault with a throw of about 100 feet. The fault zone 
has dropped the beds on the southwest side at least 500 feet and 
is the only one of this group comparable in size with the fault 
that terminates the shale member of the Prospect Mountain 
quartzite north of the road leading to the Spotted Fawn mine. 
If, as seems likely, the two faults are the same, they might serve 
as starting points to determine the fault pattern in the Prospect 
Mountain quartzite, should a more detailed study of the geology 
be undertaken. 

The eastern portions of sections C-C and D-D' show the 
more striking features of the overridden rocks. They are some- 
what diagrammatic, however, particularly in the almost com- 
plete omission of the nearly horizontal minor thrusts that are 
probably rather widespread. 

Garrison Monster transverse fault zone. — The fault zone near 
the Garrison Monster mine illustrates the mechanism of trans- 



GEOLOGIC STKUCTUEE 



83 



verse faulting better than any of the other faults of this type in 
the quadrangle. It appears to represent a line of differential 
movement, north of which shortening was accomplished by 
thrusting and to the south by folding (p. 59 and fig, 8). 
The fault zone varies in character from a single steep fracture 
to a group of faults with relatively low dip. 

The simple, steep portion of the fault is best seen south of the 
Garrison Monster inclined shaft, where it separates Prospect 
Mountain quartzite on the south from dolomitized Middle 
Cambrian limestones on the north (sec. A- A') . Eastward from 
this point the poor exposures indicate a swing in strike toward 
the northeast, and east of the tunnel at 4,834 feet, the strike, 
as shown by the scattered outcrops surrounded by gravel, must 
be very close to that direction. At the triple-peaked hill 2,000 
feet southwest of bench mark 4382 on the railroad, the east- 
ward continuation of the fault appears to be cut by a fault 
striking west-northwest. 

West of the Garrison Monster incline, on the south side of 
the fault, the Prospect Mountain quartzite is overlain by the 
Cabin shale and the Busby quartzite. The shale shows pro- 
nounced drag effects near the fault, its strike swinging to 
nearly east- west and its dip steepening to more than 40° N. 
The Busby quartzite, however, shows no notable drag but has 
overridden the shale along a low-angle westward-dipping fault, 
which is exposed only close to the transverse fault. On the 
north side of the transverse fault the outcrop of Middle Cam- 
brian beds wedges out westward, and the thrust plate of Upper 
Cambrian dolomite above it is adjacent to the fault. The thrust 
plate of dolomite in turn wedges out within a short distance, 
and at the bottom of the gulch leading to the Garrison Monster 
camp the Ochre Mountain limestone is next to the fault. The 
contact between the limestone and the dolomite must represent 
the Ochre Mountain thrust. Gravel flooring the gulch inter- 
rupts the outcrops for a few hundred feet. The dip of this 
section of the fault cannot be directly measured, but both the 
dips in the beds on each side and the effect of the topography 
upon its outcrop indicate that it must dip steeply to the north. 

On the west wall of the gulch the Ochre Mountain limestone 
is in fault contact with Middle Cambrian beds, but the fault 
dips at a moderately low angle (about 40°) to the north. This 
fault has several branches with somewhat lower dips, which 
bring in, with various relations, all the formations that intervene 
between the Ochre Mountain limestone and the Middle Cam- 
brian in the region to the south, where the thrust is essentially 
undeformed. The single steep fracture to the east has thus 
been replaced westward by a fault zone of low dip. The change 
in character coincides with the intersection of the transverse 
fault with the Ochre Mountain thrust. A similar coincidence 
was noted on the south side of Ochre Mountain (p. 71), and 
it was suggested that the low dip of the thrust had caused the 
change in dip of the transverse fault. 

About 1,000 feet east of the mouth of Royal Gulch the north- 
ernmost of the series of branch faults disappears beneath the 
piedmont gravel. West of this point the projected course of 
the transverse fault is covered by gravel until the west side 
of the gravel-filled area in Accident Canyon is reached. In 
this distance, however, east-west strikes in the Woodman for- 
mation to the south and local nearly east-west fracture zones, 
particularly in the two eastern isolated outcrops in Accident 
Canyon, suggest strongly that the fault is not far distant. On 
the west side of Accident Canyon the projected line of the fault 
corresponds with a fault separating Madison limestone on the 
north and the Woodman formation on the south. The Wood- 
man beds are poorly exposed but are thought to be rather 
closely folded, and the Madison limestone shows rather pro- 
nounced drag effects. 

West of another gravel-covered interval the fault is again 
exposed along the base of the linear steep slope west of Accident 
Canyon. Here the Ochre Mountain thrust appears on the 



north side, the Woodman formation resting upon the Laketown 
dolomite. At the point where the steep slope curves north- 
ward, however, the fault does not cross the spur, as is shown by 
the continuous exposure of the Ochre Mountain thrust. There 
must, however, be some warping along this general line still 
farther west, because the Ochre Mountain thrust as exposed in 
the isolated outcrops to the north is at a much lower altitude 
than to the south (sec. F-F'). 

Nature and amount of movement along Garrison Monster fault 
zone. — In the vicinity of the Garrison Monster mine the rocks 
north of the transverse fault are believed to have moved rela- 
tively eastward about \% miles. This belief is based upon the 
assumption that the westward-dipping fault separating the 
Woodman formation from the Ochre Mountain limestone ex- 
posed west of the Garrison Monster workings is the same as 
the steeply dipping portion of the Dutch Mountain fault (p. 84) , 
to the south. This figure is roughly checked by the position of 
the Ochre Mountain thrust on both sides of the transverse fault. 

It is probable that the transverse fault represents a line of 
differential movement, north of which crustal shortening took 
place along a thrust fault, and south of which shortening was 
accomplished by folding (fig. 8). The evidence for this belief 
is as follows: Thrusting of some sort seems required north of 
the thrust, for the Ochre Mountain thrust, which may be used 
as a horizon marker, is relatively undeformed north of the thrust 
except for a gentle westward dip. As the north side has appar- 
ently moved eastward, the crustal shortening must therefore 
have been effected by faulting. The northeastward curvature 
in strike shown by the transverse fault as it is followed eastward 
suggests that the transverse fault itself is passing into a thrust, 
but the absence of adequate exposures in that direction makes 
it impossible to prove the suggestion. 

The folding of the Ochre Mountain thrust south of the trans- 
verse fault (p. 80) appears to provide the required amount 
of shortening to the south. The scaled distance along the 
folded thrust in a section nearly 2 miles south of the transverse 
fault showed that there had been half a mile of shortening along 
this line. This amount is only a third of the probable move- 
ment along the transverse fault and suggests that the amount 
of compression decreased southward, a suggestion that appears 
to be confirmed by the absence of comparable folding of the 
thrust in Pool Canyon, where the thrust is exposed for some 
distance in an east-west direction, and by the northeast strike 
of the axis of the fold, rather than the northerly strike that 
would be expected if the compression were of equal magnitude 
to the south. 

Probable conjugate faulting related to Garrison Monster fault. — 
Two groups of faults that are younger than the Ochre Moun- 
tain thrust are present on Dutch Mountain, chiefly south of 
the Garrison Monster fault zone. The faults of one of these 
groups strike northeast and dip northwest. Many of them 
show an apparent reverse movement. The faults of the other 
group strike northwest and dip southwest. They commonly 
follow lines of pre-thrust faulting in the beds below the thrust. 
On some of them the movement has been largely horizontal. 
Although the northeasterly faults commonly cut the northwest- 
erly ones, locally, as in Royal Gulch, the reverse is true. These 
relations suggest that the two groups of faults are essentially 
contemporaneous and form a set of conjugate faults. As some 
of the northeasterly faults appear to change their strike to east 
as they approach the Garrison Monster fault zone and to become 
a part of that zone, it seems probable that the conjugate faulting 
was genetically related to the transverse faulting. 

Similar conjugate faults adjacent to the contemporaneous 
transverse faults to the south are apparently lacking. A pos- 
sible explanation for the difference in relations may lie in the 
fact that the Garrison Monster fault has a much smaller strike 
length than the other faults of this character, and that for this 
reason the necessary readjustments in the passive block south 



84 



GOLD HILL MINING DISTBICT, UTAH 



of the fault were accomplished by both folding and faulting, 
whereas in the longer transverse faults the necessary shortening 
in the passive block could be accomplished by folding alone. 

Because of their abundance, some of the conjugate faults are 
not shown on plate 3. Where the northwesterly faults of the 
system do not cut the Ochre Mountain thrust, it is uncertain 
whether or not the fault wasactive in pre-thrust or post-thrust time 
or in both. For this reason many of the faults shown on plate 3 
are marked with the symbol for two different structural cycles, 
although most of them were probably active at only one time. 

One of the most persistent of the northeasterly faults has a 
low northwestward dip throughout most of the exposures in 
Royal Gulch and Accident Canyon, but at the floor of Accident 
Canyon its dip is almost vertical (pi. 7, C). 

Dutch Mountain thrust. — The contact between the Ochre 
Mountain limestone and the Woodman formation throughout 
the block is a thrust fault. In most of the region the thrust has 
a low dip, and its presence is shown either by a minor discordance 
in dip between the two formations and rather considerable var- 
iations in the thickness of the underlying Woodman formation 
in the higher portion of Dutch Mountain, or by the close folding 
of the Woodman formation below the thrust on the west side of 
Accident Canyon. The thrust dips steeply westward, however, 
in the southern part of Accident Canyon. This steeply dipping 
portion almost certainly connects a flatter portion whose outcrop 
encircles the summit of the mountain and another flatter portion 
exposed west of Accident Canyon, for no other faults were rec- 
ognized that could bring about the observed relations. 

The steep portion of the thrust must be an original feature 
and not due to later folding. This is definitely proved by the 
absence of such folding in the beds beneath the thrust, as is 
shown particularly by small outcrops of Madison limestone 
close to the steep portion of the thrust at altitudes that closely 
approximate those obtained by projecting the outcrops on the 
east side of Dutch Mountain. 

In the exposures of the Dutch Mountain thrust along the 
northwestern edge of the mountain the interval between this 
thrust and the Ochre Mountain thrust is much smaller than to 
the southeast, beneath the higher parts of Dutch Mountain. 
This is due chiefly to the occurrence of the steeper part of the 
Dutch Mountain thrust between the two localities, but in 
addition there appears to have been some minor warping of the 
Dutch Mountain thrust that is not shown by the Ochre Moun- 
tain thrust. The Dutch Mountain thrust must therefore be 
the older of the two. This conclusion is confirmed by the re- 
lations of the two thrusts to the Trail Gulch fault, described 
below. The Dutch Mountain thrust is cut of by this fault, 
but the Ochre Mountain thrust is not affected by it. 

In addition to the two major exposures of the thrust, there 
are two smaller isolated outcrops that are considered to be 
continuations of it. One of these is on the south side of Pool 
Canyon southeast of peak 7262, where the Ochre Mountain 
limestone rests with fault contact upon the Woodman formation. 
The thrust here dips notably to the east as a result of the dis- 
turbance in the beds above the Ochre Mountain thrust by the 
Pool Canyon transverse fault. The second small outcrop is in 
the vicinity of the Garrison Monster mine. Here a westward- 
dipping fault that separates Ochre Mountain limestone from the 
Woodman formation is believed to be a continuation of the 
steeper part of the Dutch Mountain thrust offset eastward by 
the Garrison Monster transverse fault. 

Trail Quick fault. — The fault in Trail Gulch, on the west 
slope of Dutch Mountain, shows rather noteworthy variations 
in strike, ranging from nearly north in the south-eentral portion 
through northwest to nearly west in the northern portion. It 
has been traced for about 4 miles and through most of this 
distance forms the boundary between the Oquirrh formation on 
the west and Mississippian formations on the east. The dip is also 
somewhat variable but is in general steep to the west or south. 



The total throw along the fault cannot be measured with any 
confidence, because of the lack of definite horizon markers on 
either side, and also because to the south it includes the throw 
of the steep portion of the Dutch Mountain thrust. Imme- 
diately north of its intersection with the thrust, the throw must 
be equivalent to about 1,000 feet or more of the Pennsyl- 
vanian plus at least 1,500 feet of the Ochre Mountain limestone. 
The throw appears to be considerably less farther north, however. 
At the extreme south end the total throw is about equal to the 
thickness of the Ochre Mountain limestone, but here the throw 
along the Dutch Mountain thrust is included. 

The chief interest of this fault lies in the fact it has been 
active at least three times. The greater part of the movement 
clearly occurred before the formation of the Ochre Mountain 
thrust, because at its south end it is cut off by the thrust. This 
movement was normal. A second normal movement along the 
central portion of the fault appears to have occurred at a com- 
paratively recent time, to judge from the topographic dis- 
cordance at the fault, the notable influence of the fault upon the 
drainage pattern, and the presence of gravels resting upon the 
mature surface adjoining the fault east of knoll 6518. The 
amount of the later movement, as estimated from the topog- 
raphy, is thought to be about 800 feet (sec. D-D'). 

In addition to these two periods of activity, both of which 
resulted in normal faulting, the fault also appears to have been 
the site of reverse movement at the time the Ochre Mountain 
thrust was formed, but it was not possible to obtain a quanti- 
tative idea of the amount, as the evidence is indirect. One 
indication is the abundance of minor folds in the Oquirrh 
formation immediately west of the Trail Gulch fault and the 
absence of such features to the east (sec. D-D'). This appears 
to show that the fault acted as a plane of relief along which 
movement took place while the beds to the west were being 
folded, thus protecting the beds to the east from similar defor- 
mation. Another indication is that in the region west of Pool 
Canyon neither the fault itself nor the Oquirrh formation in its 
hanging wall have been affected by the notable deformation 
shown by the thrust and the overlying Mississippian beds at 
the point where the Pool Canyon transverse fault was over- 
ridden by the thrust. These relations strongly suggest renewed 
movement along the fault, either of a reverse or transverse 
character, by the beds on its hanging wall. 

In summary, the fault appears to have been first formed as 
a normal fault of large throw after the period of thrusting 
represented by the Dutch Mountain thrust but before the 
Ochre Mountain thrust. During the formation of the Ochre 
Mountain thrust it was again active, but the direction of move- 
ment was reversed. Finally, renewed normal faulting occurred 
at a relatively recent time. 

Minor structural features in the rocks above the Ochre Mountain 
thrust. — In addition to the minor faults that cut the rocks both 
above and below the Ochre Mountain thrust, there are a few 
minor faults that occur only in rocks above the thrust. One 
of these is a smaE reverse fault south-southwest of Woodman 
Peak and west of the Trail Gulch fault. This fault dips 45" W. 
and has caused the lower beds of the Oquirrh formation to 
override several hundred feet of the Manning Canyon formation. 
Its relation to the Trail Gulch fault could not be determined, 
and whether it is of the same age as the Ochre Mountain thrust 
or the Dutch Mountain thrust is therefore not known. It is 
terminated on the southwest by a younger fault. 

Folding in this area was largely confined to the beds west of 
the Trail Gulch fault. Gentle folds are also found east of the 
fault, as is shown in section D-D', but are of much less intensity. 
Two well-defined folds occur west of the fault — a syncline near 
the fault and an anticline farther west. The synclinal axis 
strikes a little east of north, passing about 500 feet east of 
summit 6518. Dips on the east limb are in general steeper than 
those on the limb common to both the syncline and the anticline . 



GEOLOGIC STRUCTURE 



85 



The anticlinal axis strikes nearly north, through a point 1,000 
feet east of summit 6230. On the north the axis appears to 
split into several minor folds, one of which is shown in plate 7, B. 
On this fold the steeper dips are on the west limb, where locally 
vertical beds are found. West of the anticline the folding 
apparently increased in intensity but decreased in regularity, 
and no continuous folds could be recognized in the low hills 
that form the northwest spur of Dutch Mountain (sec. F-F'). 
In the minor and discontinuous folds in this region overturned 
beds are locally found. Figure 10 shows the course of a cross- 
bedded dolomitic sandstone west of the anticlinal axis which 
illustrates these points. The position of three summits shown 
on the topographic map is added to aid in the location of the bed. 
It is probable that two stages of folding are represented west 
of the Trail Gulch fault. The two larger and more persistent 
folds are believed to have been formed before the Trail Gulch 
fault became active, as they do not affect the fault and there 
are no comparable folds east of the fault. The smaller, locally 
overturned folds to the north, however, are considered to have 



60' 



5688 



I 



30- 



> 



so* v ' 

// 

/sof 

\ 



,5552 



\ 60"$ 

,20° 

\ 
X 

IS' 



\ 



\ 



X£..™ / 



looo Feet 



4- 



Fig-ube 10.— Sketch map showing folding of a bed in the G<jrcirrh formation on 
the northwest side of Dutch Mountain. Elevations are summits shown on 
plate 2. 

been superposed on the older folds at the time of the reverse 
movement along the Trail Gulch fault. The steep dips on the 
east limb of the larger syncline may also have originated at 
this time, as in the rest of the folded belt the intensity of folding 
increases westward. 

Fault along west side of Dutch Mountain. — The notably 
straight west side of Dutch Mountain, which transgresses the 
structure at a considerable angle, suggests strongly that there 
has been relatively recent faulting here. Locally the tips of the 
spurs along this line exhibit slickensided surfaces. The throw 
along the supposed fault cannot be determined stratigraphi- 
cally, but there is a difference in altitude of about 500 feet 
between the linear flat ridges east of the fault and the flat- 
topped isolated outcrops to the west. To the south the fault 
line changes its strike from southeast to east-southeast. The 
topographic discordance persists into this region, but to a 
somewhat less degree. Rock exposures on both sides of the 
fault, however, show that the movement along this part of it 
has been more complex. The distribution of the central facies 
oi tiift Oqvrinh. formation on both sides of the fault and the 

.the northeast aide 
Tbk conflicting evi- 
dence is believed to Indicate that movement along the fault has 



occurred at two different times — an earlier one, in which the 
movement was probably transverse, resulting in the relative 
depression of the thrust northeast of the fault, and a recent one, 
in which the apparent movement was in the opposite direction 
but was not of sufficient magnitude to conceal the older move- 
ment. 

Mutual relations of the structural features. — The relations of 
the structural features exposed in the Dutch Mountain block 
to one another are not as clear as in the blocks to the south. 
A group of north-south normal faults on the east side of Dutch 
Mountain appear to be the oldest features that were recognized. 
They are cut by a series of northwesterly normal faults, the 
greater part of whose activity must have preceded the Ochre 
Mountain thrust, and for this reason they are considered 
to have been formed in the second stage of the first cycle. 
None of these faults were found in contact with structural 
features assigned to the first stage of the second cycle, however, 
and their age is therefore in some doubt. 

The initial stage of the second cycle is clearly represented by 
the Dutch Mountain thrust, whose age relative to the Ochre 
Mountain thrust is definitely shown by the intersections of the 
two thrusts with the Trail Gulch fault. This stage appears 
to have been characterized chiefly by folding, however, and at 
least five of the larger folds in the block were formed at this time. 
Normal faults of the second stage of the cycle are abundant. 
The bulk of the movement along the Trail Gulch and Spotted 
Fawn faults was accomplished before the development of the 
Ochre Mountain thrust, and several parallel faults of less 
magnitude are of the same age. 

The dominant structural feature of the block — the Ochre 
Mountain thrust — was formed in the first stage of the third 
cycle. The relatively thin thrust plates beneath it north of the 
Spotted Fawn mine are contemporaneous. A number of trans- 
verse faults, of which the Fool Canyon fault is the largest, appear 
to be only slightly older than the Ochre Mountain thrust and to 
be of the same age as the North Pass thrust. Renewed activity 
along the Trail Gulch fault and minor drag folding adjacent to 
the fault also occurred at this time. Normal faulting in the 
second stage of the third cycle appears to have been very slight 
in amount, only one fault being assigned to this stage. 

The fourth cycle was marked by the formation of the Garrison 
Monster transverse fault and its associated warping and con- 
jugate faulting. Several of the northwesterly conjugate faults 
appear to have followed normal faults that first became active 
in the second cycle. 

The youngest faults are the relatively recent normal faults 
to which the elevation of the block is largely due. The two 
faults of this age on the west have utilized older fault lines along 
at least parts of their courses. 

NOB.TITWBSTMRN' BLOCK 

The northwestern block is west of the Dutch Mountain block 
and northwest of the Ochre Mountain block. Its southern 
boundary is the northern limit of the wide part of the Deep 
Creek Valley. The boundary between this block and the Dutch 
Mountain block coincides with a normal fault of rather large 
throw. There is, however, no structural break between this 
block and the Ochre Mountain block. 

Geologically, the block is one of the. simplest so far considered. 
The dominant structural feature in its east half is a recumbent 
anticline, whose axis appears to lie roughly parallel to and 2,500 
to 3,000 feet higher than the Ochre Mountain thrust (sees. F"-F, 
D"~D, and N"-N). The fold is older than the White Sage 
formation, but both are cut by two groups of faults, one striking 
northeast and one northwest. 

The portion of the block west of Bar Creek is separated from 
the eastern portion by a nearly north-south zone, which is to 
the north a gravel-filled valley, and to the south a linear outcrop 
of volcanic rocks. This zone marks the line of a fault or group 



86 



GOLD HILL MINING DISTEICT, UTAH 



of faults along which the beds to the west have probably been 
dropped 5,000 feet. There Is some evidence to indicate that a 
small part of this throw may have occurred in rather recent 

time. The region west of the fault zone is characterized by an 
open anticlinal fold and abundant small normal faults. Along 
the extreme west edge, however, there are locally rather close 
folds and minor overthrusts. 

Tank Wash fault. — The fault along the boundary between the 
northwestern block and the Dutch Mountain block is nowhere 
exposed, but one is obviously required in Tank Wash between 
the eastward-dipping White Sage formation at an altitude of 
5,610 feet and the fossiliferous beds high in the Oquirrh forma- 
tion near benchmark 5544, on the one hand, and the beds low 
In the Oquirrh formation to the east, on the other. The total 
throw along the fault in this region must amount to about 4,000 
feet, which was probably accomplished in stages, as indicated 
by the relations of the fault to the Ochre Mountain thrust. 

To the north the strike of the fault appears to swing to the 
northwest, as is suggested by the fracturing seen in the exposures 
at the road fork southwest of benchmark 5068 on the Ferber 
Road. A fault with similar strike and westward dip in the 
Ochre Mountain block (pp. 76-77) is thought to be a continuation 
of the Tank Wash fault. This fault is clearly later than the 
overthrust and has a throw estimated at 300 feet. In both of 
these respects it differs from the northerly outcrops of the Tank 
Wash fault. The large throw along the 
fault is clearly of pre-thrust age, as the 
nearly continuous exposures south of Dutch 
Mountain show that the thrust has nowhere 
been cut by normal faults that cause more 
than a few hundred feet of vertical dis- 
placement. The main movement along 
the Tank Wash fault must therefore have 
occurred before the development of the 
Ochre Mountain thrust, and the post- 
thrust throw of 300 feet represents renewed 
movement along the older fault. 

Twin Peaks recumbent anticline. — The 
recumbent anticline that is so prominent 
a feature of the east half of the block is 
best exposed just south of the southern 
summit of Twin Peaks. Exposures on 
the south side of peak 6147, 4 miles to 
the south, are also convincing and serve 
to justify the extension of the axis of the 
fold between the two points into regions 
where it can be located less easily. As 
shown on the map and structure sections D"-D, F"~F, and 
N"-N, the axial plane of the fold has a low and somewhat 
irregular northerly dip. At both Twin Peaks and peak 6147 
the beds involved in the fold are the massive rather pure lime- 
stones that belong in the lower part of the western facies of the 
Oquirrh formation. This indicates that the original strike of 
the axis of the fold was about N. 15° E. The present low north- 
ward dip of the axial plane is probably a later development. 

The fold is clearly older than the Eocene (?) White Sage forma- 
tion, for beds belonging to that formation overlap the axis of the 
fold about a mile west of a point in Tank Wash on the Ferber 
Road at an altitude of 5,610 feet. It is also, of course, older than 
the northeasterly and northwesterly faults that cut that forma- 
tion. It is believed to be older than the Ochre Mountain thrust 
for. the following reasons; The fold is clearly older than the 
latest movement along the Tank Wash fault, along which the 
bulk of the throw must be of pre-thrust age, although some 300 
feet may represent post-thrust movement. It is also probably 
older than the pre-thrust component of the normal fault. If 
it were younger, some trace of the fold should appear on the 



high ridges on Dutch" Mountain west of the Trail Gulch fault, 
but none has been found. Moreover, if the fold were younger 
than the earliest movement along the fault, the fault could 
scarcely have the linear outcrop it now shows, nor could there 
have been renewed movement along it. If these two features 
can be relied upon, the fold must be considerably older than 
the Ochre Mountain thrust, and the folding must have been 
separated from the thrusting by a period of normal faulting. 

Relations of recumbent anticline to structural features on Dutch 
Mountain. — The Dutch Mountain thrust and the larger folds 
west of the Trail Gulch fault on Dutch Mountain, like the 
Twin Peaks recumbent anticline, are older than the Ochre 
Mountain thrust. These features are also older than two west- 
ward-dipping normal faults of rather large throw, and it is 
■believed that they were all formed during the same cycle of 
deformation. If this view is correct, the more easterly exposures 
represent the features formed at greater depths, for the two 
younger normal faults, the Trail Gulch fault and the Tank 
Wash fault, have the down-thrown side on the west. The most 
intensive folding, however, is found in the westerly exposures, 
where the recumbent anticline occurs. Folding in the Oquirrh 
formation west of the Trail Gulch fault decreased in intensity 
eastward, and east of the fault folds are essentially absent. 
The strongest folding, therefore, was originally at the higher 
altitudes. Figure 11 shows the supposed relations between these 




Approximate position 
of TankWash fault 



Approximate position 
of Trail Gulch fault 



Figdbb 11. — Generalized section showing supposed original relations between the Twin Peaks recumbent 
anticline and the Dutch Mountain thrust. The areas enclosed by dashed lines represent in a general 
way the present exposures on both sides of the two normal faults. 

features before the initiation of movement along the Trail Gulch 
and Tank Wash faults. 

The concentration of the close folding at higher altitudes 
suggests that a thrust fault, now removed by erosion, once 
existed above the highest of the present exposures. The ob- 
served structure and stratigraphy west of Bar Creek (p. 88) to 
some extent support this view. 

The close folds of relatively small scale and the variations in 
the thickness of individual beds that are thought to lie imme- 
diately below the main recumbent fold (ig. 11) appear to be 
rather poorly exposed in the vicinity of hiE 6850, west of bench- 
mark 5544, and in the region south and west of the hill toward 
summit 6266. 

Minor faulting east of Bar Creek. — Four faults of relatively 
small throw cut the recumbent fold and also the White Sage 
formation. Two of these faults strike northwest and are offset 
by two northeasterly faults. One of the northwesterly faults 
is readily recognized on the southwest side of Twin Peaks, 
where the anticlinal axis is dropped on the southwest side. 
The vertical throw amounts to about 800 feet and may be 



GEOLOGIC STRtrCTUBE 



87 



measured rather accurately by the offset shown by the upper 
contact of the series of limestones that form Twin Peaks, Just 
north of peak 5876 this fault is offset about a quarter of a mile 
to the east by a northeasterly fault. South of this point the 
offset segment is readily traced by reason of the fact that it 
limits on the east a narrow outcrop of the White Sage formation. 
Still farther to the south the fault is concealed by volcanic rocks. 

The second of the two northwesterly faults crops out north- 
east of the 5,850-foot hill that lies on the north flank of peak 
6266, This fault forms the western boundary of another 
exposure of the White Sage formation. The positions of the 
axial plane of the fold on both sides of the fault indicate that 
the maximum throw along it does not exceed 400 feet. The 
fault is terminated on the south by one of the northeasterly 
faults. The offset portion was not recognized in the lava-capped 
region to the south. 

The northeasterly fault south of Twin Peaks can be deinitely 
recognized only on the north side of peak 5876, where it offsets 
the northwesterly fault. The throw of the fault must be rather 
large at this point, with downthrow to the southeast, because 
of the stratigraphic differences on the two sides and also be- 
cause of the amount of offset of the older fault. The displace- 
ment must die out within a short distance to the southwest, 
however, for individual beds that cross its projected strike less 
than a mile southwest of peak 5876 show no offset. The relation 
of the fault to the northwesterly fault along the east boundary 
of the block is unknown, the gravel cover in this region pre- 
venting any direct observations. 

The second of the two northeasterly faults is on the north 
and northwest sides of peak 6266, where its presence is indicated 
by the difference in structure on the two sides. To the north- 
west the axial plane of the fold crops out at an altitude of about 
5,700 feet, arid to the southeast the structure observed at the 
summit of hill 6266 shows that the axial plane must have been 
several hundred feet higher still. The throw along the fault at 
this point must therefore approach 1,000 feet. To the north- 
east the course of the fault is apparently marked by a region of 
silicification east of hill 5850, Beyond this point the fault was 
not recognized, and the fact that individual beds continue 
unbroken across its projected strike seems to indicate that it 
dies out within a rather short distance in this direction. 

The age of these four faults is not known. On plate 3 they 
are all assigned to the fourth cycle, as they correspond in strike 
with the conjugate faults related to the Garrison Monster 
transverse fault. The apparent throws are somewhat larger 
than those along the other conjugate faults, and the faults may 
therefore represent two unrelated stages of faulting, the north- 
westerly faults being the older. 

Bar Creek fault. — West of peak 6147 there is a strip of vol- 
canic rocks about three-quarters of a mile in width. This is 
succeeded northward by a somewhat wider valley filled with 
gravel. The gravel and volcanic rocks in this belt must conceal 
a considerable fault or fault zone, because of the differences in 
structure and stratigraphy on the two sides. On peak 6147, 
where prevolcanic rocks crop out nearest to the supposed fault, 
here called the Bar Creek fault, the rocks belong to the thick 
limestone member that occurs near the base of the western facies 
of the Oquirrh formation. At this point, too, the axial plane of 
the recumbent fold is exposed at an altitude of about 5,600 feet. 
West of the concealed zone, however, the beds belong to the 
highest portion of the Oquirrh formation and are overlain by 
the White Sage formation. Furthermore, the structure ob- 
served on the west side cannot be correlated with the recumbent 
fold, although the altitudes are such that the axis of this fold 
should be exposed if it continued westward unbroken. These 
two features make it seem certain that the belt is the site of 
notable displacement with north-south strike and with down- 
throw to the west. The apparent throw along the fault is 
about 5,000 feet, as it includes the thickness of the Oquirrh 



formation above the limestone member (4,500 feet) plus about 
500 feet of that member. If, however, the region west of the 
fault is underlain by a thrust fault, as there is some reason to 
believe (p. 88), the actual throw may depart widely from this 
estimate. The present distribution of the White Sage formation 
on both sides of the fault is such that a much smaller throw is 
necessary than any that would reasonably explain the structure 
shown by the underlying Carboniferous rocks and suggests that 
the Bar Creek fault, like many others in the quadrangle, has 
been the site of recurrent movement. A rough measure of the 
later movement is suggested by the difference in altitude of the 
old postmature erosion surface on the two sides of the fault, 
which amounts to about 600 to 800 feet, the region west of the 
fault being the lower. This figure is ample to explain the pres- 
ent distribution of the White Sage formation if it was, aa 
supposed, deposited in relatively small basins. 

Anticline west of Bar Creek. — West of the Bar Creek fault 
the Carboniferous formations are folded in a poorly defined 
anticline, which is most readily recognized to the south. About 
a mile east of that portion of Deep Creek between benchmarks 
5097 and 5045 the Oquirrh formation strikes west of north and 
dips to the east. Farther north and west the strike swings to 
the northwest. On the west side of Deep Creek the strike is 
somewhat more westerly, and still farther west it changes to 
west with northerly dips. Finally, the most westerly outcrops 
of the Carboniferous formations strike a little east of north and 
dip to the west, completing the fold (sec. D"-D). 

The axis of the fold in this region strikes about N. 15° E. 
through benchmark 5045 and plunges gently to the north. 
North of the hills west of the 5,122-foot depression the projected 
axis passes beneath gravel and could not be further traced. At 
this point the axis is poorly defined and is obscured by faulting. 
Several minor folds and thrusts exposed near the northern 
boundary of the quadrangle may replace the single major fold 
to the north. 

Minor folds west of Bar Creek.— The most striking of the 
several minor folds west of Bar Creek is an anticline with moder- 
ately steep dips on both limbs, which is exposed in the isolated 
hill in the Deep Creek Valley half a mile east of north of altitude 
4,992 feet on the Deep Creek road. Just beyond the northern 
border of the quadrangle dips as high as 85° were observed, 
A syncline must be present in the alluvium-filled valley between 
these outcrops and the hills to the east. 

Southeast of the anticline the erratic east and southeast dips 
north of hill 5434 may indicate the presence of another sub- 
sidiary fold on the west limb of the main anticline, but the 
extensive faulting in this region prevents any satisfactory inter- 
pretation. 

Two small overturned folds are exposed beneath a minor 
thrust fault in the hills along the western border of the quad- 
rangle west and northwest of altitude 4,984 feet on the Deep 
Creek road. The presence of the folds is shown by the repeti- 
tion of outcrops of the dark cherty beds in the upper portion 
of the Oquirrh formation, which dips 60°-75° W. on both limbs 
of the folds. The more westerly of the two folds is an anticline. 
It is cut off on the south by a fault striking north of west, which 
just east of the quadrangle boundary swings in strike to nearly 
south and decreases notably in dip. The unfolded beds above 
the fault dip rather gently to the south and include the basal 
beds of the Gerster formation. The stratigraphic hiatus be- 
tween this horizon and the black chert zone is about 2,500 feet. 
The curving fault seems to be best explained as a transverse 
fault that passes eastward into a thrust, a relation that was also 
found in several places in the Deep Creek Mountains (p. 67). 
Although these faults are shown on plate 3 as being of the same 
age as the large anticline, it is equally possible that they were 
formed in a later structural cycle. 

There is apparently another fold on the west side of Deep 
Creek. This is an east-west synclinal warp that is indicated 



88 



GOLD HILL MINING DISTRICT, UTAH 



by the northerly dips in the hills west of altitude 5,045 feet and 
southerly dips in the region west of altitude 4,984 feet. The 
intervening low-lying area is covered by volcanic rocks and 
gravel, which conceal the structure of the Carboniferous rooks 
beneath them. The syncline cannot be recognized on the east 
side of Deep Creek. The strike of the axis of this fold does 
not correspond to any of the other structural features that have 
been found in the district, and the apparent limitation of the 
fold to the west side of Deep Creek suggests that it may be 
causally connected with the volcanic rocks that now occupy 
ite axial portion. Two intrusive plugs were found in this vol- 
canic area, and a careful search might disclose others. The 
syncline might therefore be interpreted as a downwarp result- 
ing from the extrusion of volcanic matter from a source imme- 
diately beneath. 

Faulting west of Bar Creek. — Three groups of faults are found 
in the region. A group of northeasterly faults appear to be 
the youngest of the three and are widely distributed. A group 
of northwesterly faults are also found throughout this part of 
the block; they are everywhere cut by the northeasterly faults. 
Two nearly north-south faults northwest of altitude 5,062 feet 
on the Deep Creek road are thought to belong to a third group. 
They are terminated on the south by one of the northwesterly 
faults. 

Two of the northwesterly faults and one northeasterly fault 
have rather large throws. The northeasterly fault cuts the 
northwesterly faults and is believed to shift them three-quarters 
of a mile, the offset being to the northeast on the northwest 
side of the younger fault. 

The two northwesterly faults are both exposed on the east 
side of Deep Creek. The more southwesterly one crops out 
east of benchmark 5097 and has brought the White Sage forma- 
tion on the southwest into contact with the Oquirrh formation 
on the northeast. By projecting the contact between the two 
formations as exposed on both sides of the fault, the throw is 
seen to be about 1,200 feet. The more northeasterly of the 
two faults is parallel in strike and about three-quarters of a mile 
distant. The relations are similar, but the throw is about 
1,800 feet. 

On the west side of Deep Creek northwesterly faults with 
comparable throws are found some distance to the north. Thus 
just west of benchmark 5062 on the Deep Creek road there is a 
northwesterly fault whose throw is about 1,000 feet and which 
appears to correspond with the more southwesterly of the two 
faults east of the creek. The second northwesterly fault appears 
to be concealed by the gravel north of altitude 5,045 feet on the 
Deep Creek road. The throw along this fault is about 2,000 
feet, as measured by exposures of the White Sage formation on 
each side of the fault, and it is therefore comparable to the 
throw along the more northeasterly of the two faults east of 
Deep Creek. 

The northeasterly fault that is believed to have caused this 
shifting of the northwesterly faults is concealed by the gravel 
and clay that floor the Deep Creek Valley throughout most of 
its course. The exposures on the east side of Deep Creek, east 
of altitude 5,045 feet, permit it to be located rather closely, 
however, as beds in the White Sage formation southeast of the 
fault strike directly into beds well below the top of the Oquirrh 
formation on the northwest. The throw along this fault appears 
to be chiefly horizontal and to amount to about three-quarters 
of a mile. The vertical component of the throw is compara- 
tively small and varies not only in amount but in direction at 
different places along the fault. 

All three faults are shown on plate 3 as having been formed 
in the fourth structural cycle, in the belief that they are a part 
of the conjugate fault system exhibited on Dutch Mountain. 
The throws along these faults are much larger than were ob- 
served on Dutch Mountain, however, and these faults may 
therefore be of different age. 



Concealed thrust fault west of Bar Creek, — If, as seems certain, 
the down-faulted continuation of the Twin Peaks recumbent 
anticline underlies the region west of the Bar Creek fault, any 
attempt to project the surface structure downward to connect 
with that fold fails, because of the impossibility of correlating 
the progressively older beds encountered in the core of the fold 
as it is followed westward with the progressively younger for- 
mations exposed at the surface westward from the Bar Creek 
fault. The only apparent method by which these conflicting 
features may be reconciled lies in the assumption that a nearly 
horizontal thrust fault must intervene between the recumbent 
fold and the structural features exposed at the surface. East 
of the Bar Creek fault this hypothetical thrust has been removed 
by erosion, but it provides an explanation of the curious relation 
of the recumbent anticline to the observed structure on Dutch 
Mountain. 

Mutual relations of the structural features. — The faults and 
folds in the northwestern block are not easily dated with relation 
to those in the remainder of the quadrangle. The folding of the 
Twin Peaks recumbent anticline and the major part of the 
movement along the Tank Wash fault are the only two events 
whose chronologic position is certain, and both belong in the 
second structural cycle. The early movement along the Bar 
Creek fault is also thought to have occurred during this cycle, 
as all the other normal faults of large throw found in the quad- 
rangle were formed at that time. If that assignment is correct, 
the large anticline west of the fault was also formed at least as 
early as the second cycle, for it is cut by the fault. The minor 
folds and thrusts associated with the anticline were perhaps also 
formed at this time, but it is equally possible that they were 
developed at some later date. 

The third structural cycle, which produced so many changes 
in other parts of the quadrangle, is very poorly represented in 
this block. The warping of the axial plane of the recumbent 
anticline may have occurred at this time, as may some of the 
minor folds and thrusts shown on plate 3 as belonging to the 
second cycle. The north-south normal faults west of Deep 
Creek are believed to represent the second stage of the third 
cycle. 

The abundant northeasterly and northwesterly faults found 
throughout the block have been assigned to the fourth cycle, 
in the belief that they are similar to the conjugate faults of 
this age on Dutch Mountain. 

The recent movement along the Bar Creek fault and the east- 
west synclinal warping west of Deep Creek are the latest events 
recognized. 

QUABTZ MONZONITE BLOCK 

The quartz monzonite block differs from the other structural 
blocks in the quadrangle in that the faults it contains either 
affect only the quartz monzonite or have a causal relation to 
the quartz monzonite. Three groups of faults appear to be 
included by this description. The first group is composed of 
faults that are thought to have formed contemporaneously with 
the emplacement of the intrusive; the second is made up of 
faults of small throw and diverse age that probably are related 
to the cooling igneous mass; and the third includes faults that 
seem to require the action of external forces for their formation. 

Faults related to the emplacement of the quartz monzonite. — The 
faults of the irst group cannot be proved to be directly con- 
nected with the intrusion, for they do not themselves cut the 
quartz monzonite. The faults that are placed in this group are 
those that displace the Ochre Mountain thrugt in the roof 
pendants, or in the sedimentary rocks adjoining 'the stock 
along or near its western boundary. The location and character 
of the two largest faults in this group are described on pages 
75-76, where these faults are correlated with the intrusion on 
the grounds that elsewhere in the district faults of this magni- 
tude did not cut the thrust. 



GEOLOGIC STBUCTUBB 



8£ 



The distribution of these faults seems to have some signifi- 
cance. They show a localization along the western border of 
the stock, to which they are roughly parallel. Similar faults 
appear to be absent both in the roof pendants to the east and 
in the exposures of sedimentary rocks along the southern and 
northern borders. These spatial relatione are the same as 
those of a group of ore deposits that contain considerable 
quantities of sueh minerals as tourmaline, hurnite, axinite, 
danburite, and scheelite, the formation of which is commonly 
thought to require relatively high temperatures. 

The coincidence of the belt of faulting with the belt of high- 
temperature mineralization is thought to indicate that this 
belt marks the location of the primary channel through which 
the quartz monzonite was intruded, the faulting being a second- 
ary consequence of the upwelling magma. As the faulting 
occurred before the intrusive solidified and the faults were 
utilized by the magma in its ascent, there would be no dis- 
placement of the igneous contacts, and thus there is no direct 
evidence of the relation between the two. 

In several other places the quartz monzonite has used faults 
during its emplacement, but in all of them, so far as can be 
ascertained, the relation is a passive one, the faults being much 
older than the intrusive and undergoing no renewal of movement 
during the process. This is certainly the case on the south side 
of Monteiuma Peak, where the influence of earlier faulting 
upon the boundaries of the igneous rock is most marked; and 
also in Pool Canyon, where the older Pool Canyon transverse 
fault has served to localize a tongue of the intrusion. 

There is a considerable body of evidence indicating that the 
intrusive did not exert any doming effect on the invaded rocks 
except for the relatively slight uplift in the zone described in 
the preceding paragraphs. This is best shown by the exposure 
of the Ochre Mountain thrust plane in roof pendants at alti- 
tudes rather closely concordant with those of the thrust in 
areas distant from the intrusion. On the southern slopes of 
Montezuma Peak, moreover, the intrusion has broken through 
an eastward-dipping monoclinal sequence without any apparent 
effect on the preintrusive strike and dip of the invaded rocks. 
The same lack of concordance between the boundary of the 
Intrusive and the structure of the invaded rocks is shown along 
the northern and western contacts but somewhat less clearly 
because of the more complex structure of the sedimentary rocks 
at these places. 

Structural features related to the solidification of the quartz 
monzonite. — The structural features of the second group are 
numerous and wide-spread. They include faults and shear 
zones whose throws can be definitely measured, as well as frac- 
tures followed by dikes and veins, along some of which also 
faulting can be definitely proved. The joints that occur in 
the quartz monzonite may also be included, for the evidence is 
clear that at least some of them were formed during the same 
period as the other structural features of this group. 

An attempt was made to classify these features according to 
their strikes and dips and to correlate such groups either with 
an areal distribution or with the type of dike or vein that filled 
them or was faulted by them — an indirect and approximate 
measure of the age. In this attempt nearly 100 strikes and dips 
were chosen at random, about one half from quartz-sulphide 
veins and the remainder from other ore-bearing veins, from 
dikes, and from unmineralized faults. 

The only conclusion that was reached from this study was that 
unmineralized faults or shear zones showed a strong tendency 
to strike either nearly east or nearly north. For the other 
groups there was no uniformity in strike or dip within a group, 
nor was any pronounced areal pattern of fracturing discernible. 
A graphic compilation of the strikes and dips upon which this 
conclusion is based is shown in figure 12. 

These fractures appear to be of diverse age and throw, as 
well as of diverse orientation, although they were al formed after 

35311-35 7 



the solidification of the quartz monzonite and before the intro- 
duction of the material that now fills them. Only a few pre- 
serve any evidence whatever of the amount of movement along 
, them. 

Intersecting dikes of different kinds within the stock indicate 
Assuring at different times. They are found particularly north- 
west of Gold Hill, and also immediately east of hill 5675, on 
the north side of Bodenhouse Wash. There appears to have 
been little or no movement along any of these fractures. 

The relatively early formation of some of the joints in the 
igneous rock is shown by two different sets of phenomena. 
One is the coating of joints by black tourmaline or green epidote, 
both minerals characteristic of what are thought to be the earli- 
est of the ore deposits. The other is the transgression of the 
joints at a large angle by quartz-sulphide veins on the old Mam- 
moth claim and also at several prospects on the south side of 
Rodenhouse Wash. 

Less conclusive evidence for different times of fracturing is 
furnished by compound dikes and by the occurrence in the same 
fracture either of two different kinds of veins or of a dike and a 
vein. Compound dikes are not uncommon, and in the Monoeca 
mine a carbonate vein follows the same fissure that had been 
filled earlier by a eopper-lead sulphide deposit. The presence 
of a quartz-sulphide vein along the wall of a granite porphyry 
dike in the Cyclone mine proves that this particular fracture 
must have been opened at two widely separated times, for quartz- 
sulphide veins were formed relatively late in the sequence of 
mineralization, all of which took place later than the intrusion 
of the dike. 

There are only a few fractures along which the throw can be 
determined. One of these is exposed on the property of the 
Silver & Gold Mining Co., southeast of Calico Hill. Here an 
unbrecciated quartz vein occupies a fissure that displaces the 
contact of the quartz monzonite and the sedimentary rocks 10 
feet. An even more striking example is shown on the Helmet 
claim of the Western Utah Extension Copper Co., where a 
mineralized fissure striking north cuts an augite porphyry dike 
striking east of north and displaces it about 50 feet. The indi- 
vidual mine descriptions include additional information on this 
group of fractures. 

The differences shown by these fractures in strike and dip, 
and in age, seem rather definitely to eliminate any directed hori- 
zontal force as being instrumental in their formation. As they 
are essentially limited to the intrusive, they have evidently re- 
sulted from the stresses set up at intervals in the slowly cooling 
stock. 

Structural features not related to the emplacement or cooling of 
the quartz monzonite. — In addition to the structural features of 
the two groups just described, there appears to be some evidence 
for faulting that requires a cause outside of the stock itself. 
One of the most significant pieces of evidence in this respect was 
observed in a tunnel on the northeast side of Ochre Mountain, 
which cuts the crushed rocks immediately beneath the Oehre 
Mountain thrust. East of the tunnel an uncrushed dike of 
quartz monzonite porphyry is exposed cutting the overridden _ 
rocks. The dike is about a mile west of the stock — clearly 
well beyond the range of any movements emanating from the 
igneous rocks. What is apparently a continuation of the dike 
in the tunnel, however, is thoroughly crushed, apparently as 
the result of movement along the major thrust. As several 
of the roof pendants included within the quartz monzonite 
show that the Ochre Mountain thrust is older than the intrusion, 
the crushed dike in the tunnel can only be interpreted tq mean 
that there has been renewed movement along the thrust after 
the emplacement of the stock and beyond its range of influence. 

Evidence to the same effect appears to be -afforded by the 
intersecting dikes east of hill 5675, on the north side of Boden- 
house Wash. At the summit of the hill and extending westward 
are several quartz and quartz-carbonate veins that dip at a 



90 



GOLD HILL MINING DISTRICT, UTAH 



rather low angle to the west and are exposed at intervals for 
more than 2 miles to the south. One of the dikes on the east 
side of the hill strikes south of east, almost normal to the strike 
of the veins. The other dike, a composite one, strikes south of 
east and is clearly the younger, as it can be traced continuously 
through the first. It has, however, been sheared sufficiently to 
develop a rude cleavage, a feature that is lacking in the older 
dike. Both dikes are cut off by the most easterly quartz- 
carbonate vein. West of the zone of veins the quartz monzonite 
has been thoroughly chloritized and is seamed by a network of 
thin quartz veinlets. 



evidence of compression movements. Among the most notable 
are two faults exposed a short distance south of the Western 
Utah Copper Co.'s open cut on Gold Hill. Both strike about 
N. 20° E., and one at least definitely dips to the west. The 
more westerly of the two cuts the vein on the Helmet claim of 
the Western Utah Extension Copper Co. in such a way that it 
must either be a reverse fault or a normal fault in which the 
horizontal component of movement is large. The dip on the 
eastern fault was not observed, but its relations to the westward- 
dipping porphyry dike that extends southward from the summit 
of Gold Hill are the same. Although neither of these faults can 



W. 90 




90'£. 



Figure 12. — Strikes and dips of various types of fractures in the quartz monzonite. Fractures having dips with an easterly component shown at the right, those with i 
westerly component at the left. Strike direction measured along the circumference of the circle; amount of dip measured by distance outward from center of circle. 



These observations, particularly the selective shearing shown 
by the dikes, suggest that the zone now occupied by the veins 
represents a zone of faulting that resulted from compression. 
The faulting must have occurred after the intrusion of the 
dikes on the east side of hill 5675 and before the formation of 
the quartz and quartz-carbonate veins. 

With the evidence from these two localities in mind, other 
phenomena observed in the intrusive area appear to present 



be definitely said to be a reverse fault, their parallelism in 
strike with the zone to the south would seem to make this the 
most probable explanation. 

Similarly, the fact that all the veins in the district with a 
nearly north-south strike show gouge, in which crushed ore 
minerals are present, on either or both walls, although veins with 
a nearly east-west strike do not, is also suggestive of a directed 
pressure. It is also possible that the numerous small faults of 



IGNEOUS METAMOBPHISM 



01 



east-west strike and nearly vertical dip that cut both veins 
(as on the Copper Queen Midland group) and dikes (as best 
shown east of the Success workings) may be considered to 
represent small transverse faults that accompanied the reverse 
faulting. 

The normal faults that form the boundaries between sedi- 
mentary and igneous rock east of the U.S. mine (p, 76) and 
the Western Utah mine (p. 77) may represent a stage of 
normal faulting that followed the reverse faulting. Both the 
normal and reverse faults at the U.S. mine are clearly later 
than the ore. The throws along the normal faults — 200 to 300 
feet at the U.S. mine and probably an equal amount or more 
at the Western Utah mine — are much larger than any deter- 
mined for the faults belonging to the second group, and this, 
with their postmineral age, makes it difficult to consider that 
they have formed as a result of the cooling of the intrusion. 

IGNEOUS METAMORPHISM 

Throughout the greater part of the quadrangle the 
quartz monzonite stock and the sedimentary rocks 
which it invades have changed in composition or 
texture in varying degrees as a result of the after effects 
of the intrusion. In part these changes may be 
correlated with differences in the original composition 
of the rocks affected, but for the greater part they 
are clearly the result of the addition of material to 
the rock. In both igneous and sedimentary rocks a 
single rock type may have several different altered 
faeies, each of which is characterized by some distinct 
mineral or group of minerals. In many places rocks 
containing minerals of different groups were found, 
but microscopic study of such occurrences indicated 
that different groups were not contemporaneous but 
that one set replaced or was replaced by another. 
. Recognition of a series of such progressive replacements 
in both the altered sedimentary rocks and the igneous 
rocks led to the conclusion that the processes causing 
the alteration extended over a considerable time, dur- 
ing which they were continuously changing. 

Ores of gold, silver, copper, lead, zinc, arsenic, 
tungsten, bismuth, and molybdenum are also widely 
distributed throughout the quartz monzonite area 
and in the bordering sediments. These are associated 
with the metamorphosed rocks mentioned in the pre- 
ceding paragraph, and in many of the occurrences it 
is apparent that some, if not all, of the ore minerals 
closely approximate in age certain of the mineral 
groups that characterize the igneous metamorphism. 
There thus appears to exist a parallelism between the 
progress of the rock alteration and the formation of 
the ore minerals. Additional factors, however, prevent 
a close correlation between the distribution of a par- 
ticular faeies of rock alteration and the ore bodies, 
which are the result of concentrations of ore minerals. 
Perhaps the most effective of these factors is the 
presence of crustal movements during the time interval 
in which the alteration and ore deposition took place. 
In localities where no crustal movement has occurred 
the correlation is possible. There is some evidence to 
indicate that in this region fracturing and minor fault- 



ing proceeded hand in hand with the processes of 
alteration and to this may perhaps be attributed the 
numerous but disappointingly small concentrations of 

ore minerals in the district. 

AITERATION OF THE SEDIMENTARY ROCKS 

The metamorphism of the sedimentary rocks as con- 
sidered here is of four classes — reerystallization, altera- 
tions resulting in the formation of silicate minerals, 
alteration to jasperoids, and dolomitization. This 
grouping is in some respects unsatisfactory, for it does 
not permit separate consideration for the effect of the 
original composition of the rock. It lends itself more 
readily to a comparison with the changes undergone 
by the quartz monzonite, however, and has been 
adopted for this reason. Moreover, the greater part 
of the rock affected is made up of limestone. 

Reerystallization. — The most widely distributed type 
of alteration within the quadrangle is reerystallization, 
and the greater part of the metamorphosed area shown 
on plate 2 is underlain by rocks that have been recrys- 
tallized rather than changed by the introduction of 
additional material. This appears to have been the 
earliest of the several types of metamorphism, for 
minerals characteristic of the other types have been 
found replacing all varieties of the recrystallized sedi- 
ments. The distribution of the recrystallized rocks 
and especially the failure to find much evidence of 
alteration of this kind in some of the masses of Ochre 
Mountain limestone occurring as roof pendants within 
the quartz monzonite area appear to require some " 
causative agency in addition to the heat given off by 
the intrusive rock. The fact that the essentially unaf- 
fected limestones lie above the Ochre Mountain thrust 
and are separated by it from highly altered sediments 
beneath would seem to support the theory that the 
reerystallization was induced by circulating waters, 
either connate or magmatic, that had been started in 
motion by the magma. 

Both limestones and quartzites affected by the re- 
crystallization show an increased grain size, which was 
accompanied by the development of an allotriomorphic 
texture and a marked bleaching. In addition, the 
strain phenomena found in both the unaltered calcite 
and the quartz have disappeared. In the rocks made 
up of calcite and quartz there appears to have been 
practically no reaction between these two minerals 
during the period of reerystallization. For example, 
in specimens of strikingly recrystallized limestone from 
the Western Utah Copper Co.'s Gold Hill mine no 
silicate minerals were noted, although solution of the 
rock in dilute acid showed the presence of a small 
percentage of quartz. 

This feature does not seem to be true for the argil- 
laceous rocks, of which the black shales of the Manning 
Canyon formation are the most abundant examples. 
These rocks have been altered to andalusite hornfels, 
in which biotite and sericite have been formed in 



92 



GOLD HILL MINING DISTEICT, UTAH 



abundance, in addition to the andalusite. The sev- 
eral stages in the development of the andalusite, which 
have been illustrated and described by Kemp, 20 may 
be observed in a single thin section and, to the writer, 
appear to furnish clear evidence that these minerals 
were formed without the introduction of any new 
material. 

Alteration to silicate minerals. — The type of metamor- 
phism consisting of alteration to silicate minerals is 
frequently referred to as "contact" metamorphism. 
The writer has refrained from the use of this term 
because of the two most striking features in the dis- 
tribution of rock of this kind in the Gold Hill quad- 
rangle. One of these features is that the silicate- 
mineral alteration has been effected with very little 
regard for the actual igneous contact. Perhaps one of 
the best localities to show this lack of relationship is 
on the southern boundary of the quartz monzonite 
body on the south slope of Montezuma Peak. Just 
east of the road leading up Barney Reevey Gulch the 
rocks in contact with the quartz monzonite are mem- 
bers of the central facies of the Oquirrh formation. 
They have been only slightly affected by the igneous 
rock, and in one place a limestone bed that appeared 
to have escaped even the usual bleaching was found 
essentially at the contact. The same beds as those 
]"ust described are also in contact with the quartz 
monzonite about half a mile to the east, in the vicinity 
of the Midas mine. There appears to be no differ- 
ence in physical conditions at these two localities, but 
at the more easterly outcrops the limestone beds have 
been almost completely replaced by silicate minerals. 

Alteration of this type was also noted at two locali- 
ties in Spotted Fawn Canyon, both more than a mile 
from any outcrops of the quartz monzonite. These 
localities may, of course, be underlain by igneous rock 
at no great depth, but the fact remains that alteration 
of this type has occurred here, where there is no con- 
tact, and no evidence of it has been found at many 
places along the contact. 

The second feature in the distribution of this altera- 
tion is the fact that the rocks lying above the Ochre 
Mountain thrust have suffered essentially no alteration. 
In several places, particularly in the vicinity of the 
Lucy L mine, there are roof pendants in which nearly 
unaltered Ochre Mountain limestone rests upon highly 
altered members of the Oquirrh formation. The sides 
of the pendants are steep, and both formations are in 
equal proximity to the intrusive. 

This lack of relation between the so-called "contact " 
metamorphism and the igneous contact has been 
emphasized by many authors, and the only excuse that 
is offered for bringing up the matter here is that the 
term is still used for alteration of this type, even though 
it is recognized that the term is inappropriate. It 



» Kemp, J. F., Notes on <Md Hill and vicinity, Tooele County, western Utah: 
Eoon. Geology, vol. IS, pp. 258-256, 1918. 



hardly seems desirable to use so descriptive a term in 
this region where its lack of pertinence is so obvious. 

Individual occurrences of this alteration have several 
different habits. The most wide-spread of these is 
probably the localization of the silicate minerals to a 
single bed, between others that have been affected to 
only a very minor degree. This habit is well shown in 
the 760-foot level of the Western Utah Copper Co.'s 
Gold Hill mine, where two beds of limestone have been 
almost entirely converted to a mixture of silicates but 
are separated by a coarsely crystalline limestone, 
which yielded practically no insoluble matter on test- 
ing with dilute acid. In the Midas, Alvarado, and 
Cane Springs mines limestone beds that have been 
altered to silicate minerals have been developed in the 
search for ore; and in all three of these mines the 
altered bed has been the site of minor slipping that 
parallels the strike and dip of the bed. In other locali- 
ties the silicate minerals are found as small irregular 
masses. At least some of these masses appear to have 
been localized by intersecting fractures, but whether 
or not all of these occurrences can be so explained is 
somewhat questionable. Finally, on the fourth level 
of the Cane Springs mine a tabular mass of silicate 
rock about 1 foot thick was found cutting across the 
bedding of the enclosing rocks nearly at right angles. 

In all these types of occurrence there is, in some 
localities, a suggestion that the alteration has been 
guided by preexistent minor fractures. Something of 
this nature is required in view of the lack of relation 
to the igneous contact. 

Mineralogically, there tend to be two main types of 
rock that are formed by the silicate alteration of the 
limestone beds. One of these is dark-colored and 
heavy and is composed almost entirely of green diop- 
side and a brown garnet, probably near grossularite in 
composition. The other is a strikingly light-colored 
type in which white bladed wolastonite predominates. 
In general the wollastonite-rich rock is more wide- 
spread than the gamet-diopside mixture, which appears 
to be more or less confined to regions in which the 
intensity of metamorphism has been at a maximum, 
as indicated by the nearly complete destruction of 
original minerals and texture in the sedimentary rocks 
and the adjacent quartz monzonite and by the occur- 
rence in these places of tungsten, bismuth, and molyb- 
denum minerals. Several specimens were collected in 
which the three silicate minerals occur together. In 
these specimens the colored minerals occur as rounded 
areas or as bands in the wolastonite, and thin sections 
cut from such areas indicate that the wollastonite was 
the latest mineral to form (pi. 8, A). 

Variations from these two types of alteration are 
rather numerous but are quantitatively of distinctly 
minor importance. Perhaps the most interesting of 
these unusual facies are found in the immediate vicin- 
ity of ore bodies. Microscopic examination of garnet- 



IGNEOUS METAMOEPHIBM 



93 



diopside rocks from such localities shows that locally 
zoisite, humite, and an amphibole near actinolite have 
partlj replaced the garnet and diopside. In such 
specimens also microscopic crystals of titanite and 
apatite may be also present. The wollastonite rock 
was not found to contain these later minerals. In 
several of the gold mines, however, wollastonite has 
been replaced almost completely by the hydrated 
magnesium silicate, spadaite (MgO-SiOr2H 2 0), (See 
pi. 8, C.) 

A more wide-spread variation, which, however, 
seems to be most abundantly represented near the ore 
bodies, consists of a chloritic replacement of the other 
silicate minerals. Both the gamet-diopside facies and 
the wollastonite facies appear to have been subject to 
such a replacement. Both green and colorless chlorite 
were noted, generally accompanied by either quartz or 
calcite. In many of the specimens the chlorite is in 
the form of microscopic rosettes, which in some places 
are embedded within quartz areas and in others 
embayed by the quartz. 

The silicate alteration of rocks that originally con- 
tained minerals other than calcite is an additional 
facies of metamorphism. The sandstone members of 
the Woodman and Oquirrh formations, which have 
only a relatively small content of calcite, characteristi- 
cally change to a light-colored, heavy rock that is 
composed of diopside and quartz. The brown color 
shown by weathered surfaces of the unaltered rock is 
absent from the metamorphosed equivalent, suggesting 
that the small amount of iron normally present was 
incorporated into the newly formed diopside. 

Many of the metamorphosed quartz-rich rocks were 
also found to contain orthoelase in amounts ranging 
from scattered tiny grains, which had developed in 
quartz near the diopside areas, to aggregates that in- 
cluded only small amounts of other minerals. Biotite 
was found in moderate amounts in some of these 
quartz-rich rocks, and garnet and wollastonite were 
noted in specimens that probably were originally 
rather calcareous sandstones. Sericite and chlorite 
were also found in some specimens, but, as in the 
garnet-diopside and wollastonite rocks, they appear to 
have formed at the expense of the earlier silicates. 

Tourmaline was recognized in only two specimens. 
Both of these rocks were originally sandy shales — one 
from the Cambrian in Spotted Fawn Canyon and the 
other from the Manning Canyon formation near the 
head of Overland Canyon. 

Alteration to jasperoids, — Alteration of the sedimen- 
tary rocks to jasperoids has been rather wide-spread. 
This phase of the metamorphism occurred, in general, 
rather near the contact with the quartz monzonite. 
(See pi. 2, on which areas of jasperoid are shown.) 
Its occurrence at the igneous contact is particularly 
striking east of Clifton, in the vicinity of the Minne- 
haha group of claims, where the interbedded sandstones 



and limestones of the Oquirrh formation have been 
almost completely altered for distances of more than 
100 feet from the contact. 

In other places faults older than the quartz monzon- 
ite have localized the formation of jasperoid. One 
of the most striking occurrences of this sort is the linear 
ridge composed of brownish-weathering jasperoid that 
extends north and south from the summit of Gold 
Hill. This mass marks a fault that separates the Ochre 
Mountain limestone and the Manning Canyon forma- 
tion. The workings in the Western Utah Copper Co.'s 
mine have exposed this jasperoid on both the 300- 
foot and 700-foot levels. The low jasperoid hill west 
of the Yellow Hammer mine, northwest of Clifton, 
is also clearly the result of alteration along the lines 
of two intersecting faults. 

Bodies of jasperoid probably were also formed in 
the Ochre Mountain limestone where the limestone 
is directly overlain by flat-lying beds of the Manning 
Canyon formation. This is particularly clear near the 
mouth of Barney Reevey Gulch and was probably 
also a contributive factor in the development of the 
abundant jasperoid found in the vicinity of the U.S. 
mine, south of the town of Gold Hill. 

The jasperoids are dense siliceous rocks, which have, 
in general, the appearance of cemented siliceous brec- 
cias, owing to the presence of several generations of 
quartz. In many specimens gray quartz is cemented 
by veinlets of white quartz, in the centers of which are 
sporadic vup lined with terminated quartz crystals, 
but in other specimens white quartz fragments are 
set in a matrix of darker quartz. The cementing 
veinlets, when examined closely, are seen not to cut 
the older quartz sharply but to have gradational con- 
tacts, marked by a gradual change in color and a slight 
coarsening of grain outward. Locally similar changes 
may be observed within the older quartz areas around 
small vugs. White, glistening barite is in many places 
abundant in the jasperoids, especially where remnants 
of unreplaced limestone are present. Near the south 
end of the jasperoid mass forming Gold Hill plates of 
this mineral more than an inch in length were observed 
set in a matrix of green chalcedony. Small quantities 
of sulphides, probably chiefly pyrite, are present in 
most of the occurrences, and weathered surfaces of the 
rock as a result have a deep reddish-brown coloration. 

Under the microscope the jasperoids present many 
interesting features. Quartz forms the great bulk of 
the material, and with it are associated small amounts 
of barite, sericite, calcite, a colorless chlorite (?), chal- 
cedony, and opal. In most of the specimens a very 
finely crystalline quartz predominates. Within it are 
small inclusions of the colorless chlorite or sericite, 
splotches or bands of barite, and locally tiny blebs 
of opal (pi. 8, B). Remnants of replaced calcite are 
present in many of the specimens, and in one slide 
cleavage lines of calcite characteristic of the recrystal- 



94 



GOLD HILL MINING DISTRICT, UTAH 



lized limestones have been preserved (pi. 8, D). The 
fine-grained quartz in some places shows features that 
might be interpreted as desiccation cracks, and these 
appear to have partly controlled localization of the 
veinlets of later quartz that give the rock its breeeiated 
appearance. The later quartz veinlets are more 
coarsely crystalline than the earlier quartz. In plain 
parallel light individual crystals appear to have devel- • 
oped normal to the walls of the veinlets, and lines of 
inclusions mark several stages in the growth of each 
grain. With crossed nicols, however, it may be seen 
that the present grain boundaries do not conform to the 
outlines marked by the inclusions. This recrystalliza- 
tion has apparently also extended into the areas of 
older quartz adjacent to the veinlets and accounts for 
the blurred outlines of the veinlets noted in the hand 
specimens. 

The time of formation of the jasperoid was clearly 
later than the initial recrystallization of the sedimen- 
tary rock, as the quartz has been found to replace the 
recrystallized limestones. Its relations at the U.S. 
mine indicate that it is also later .than the silicate 
alteration. There the ore minerals are limited in their 
distribution by the silicate rock and are later than that . 
rock. Some of the sulphide minerals, however, partic- 
ularly arsenopyrite, are shattered and veined by the 
jasperoid, whose age must therefore be relatively late 
in the metamorphic sequence. 

The texture disclosed by the microscope indicates 
that the initial replacement of the limestone by silica 
resulted in a gel-like material which contained at 
least some opal and in which were developed cracks 
resembling desiccation cracks. There is no positive 
evidence that all of the material was originally opal 
and that this changed to fine-grained quartz during 
the drying represented by the cracks, but this view 
seems not unlikely. The origin of the more coarsely 
crystalline quartz in the veinlets and its subsequent 
recrystallization, together with that of the older fine- 
grained quartz, are also not susceptible of definite 
proof, but it might well be the result of slow deposition 
from expelled liquid and subsequent growth induced 
by the continued presence of the liquid. 

Dolomitization. — Dolomitization is one of the most 
widely distributed of the four types of alteration recog- 
nized. It does not affect, in general, the limestones 
near the quartz monzonite contact, but rather those 
at some distance from the intrusive. Thus, the Cam- 
brian limestones in the Deep Creek Mountains and 
the northern part of Dutch Mountain have been locally 
converted to dolomite, as have the Ochre Mountain 
limestone on Dutch Mountain and the limestones of 
the Oquirrh formation in the vicinity of Twin Peaks. 
On the other hand, there has been some dolomitization 
of the Ochre Mountain limestone at the Western Utah 
Copper Co.'s mine at Gold Hill rather close to the 
quartz monzonite, but this seems to be of compara- 
tively small extent. 



The Cambrian limestones and to a smaller degree 
the Carboniferous limestones have been changed by 
the alteration from a dense blue limestone to a rather 
coarsely crystalline rock which weathers to shades 
of light brown to chocolate-brown. Blowpipe tests 
on some of these dolomites show that manganese as 
well as iron is present, and it is probable that the 
coloring on the weathered surfaces may be ascribed to 
this metal. The marked distinction in color between 
the unaltered limestone and the dolomite makes it 
possible to prove the dependence of the alteration 
upon lines of fracturing in the limestone beds. This 
is best shown in the Deep Creek Mountains, where 
the alteration is comparatively slight. Near the Gar- 
rison Monster mine, however, dolomitization of the 
Cambrian limestone has been so nearly complete that 
remnants of unaltered limestone are relatively rare. 

The time of dolomitization with respect to the other 
phases of metamorphism is not definitely known, as 
dolomitized bodies are not in contact with the other 
types of altered rocks. Carbonate veins, containing 
dolomite of apparently similar composition to that 
replacing the limestone, are, however, rather abundant 
in the mineralized quartz monzonite and appear to 
represent the latest stages of the magmatic after effects. 

A1TE1ATION OF THE QUAKTZ MONZONITE 

The quartz monzonite stock has been altered over 
much of its extent. Several different faeies of altera- 
tion may be distinguished in it, but they are not 
spatially so distinct as those recognized in the meta- 
morphosed sedimentary rocks, although it is believed 
that the two groups may be directly compared. The 
oldest faeies contains garnet, diopside, orthoclase, and 
other silicates. In many places these minerals, as well 
as the original constituents of the quartz monzonite, 
are altered to sericite and chlorite with some quartz, 
and this grouping is considered to form the second 
faeies. A stage in which fine-grained quartz was in- 
troduced appears to have been still later and appar- 
ently was essentially contemporaneous with the forma- 
tion of jasperoids in the sedimentary rocks. The 
second of these three fades appears to occupy the 
largest area. In many specimens two or even all 
three may be observed in contact. 

Diopside-orthoclase alteration. — The alteration that 
introduced diopside and orthoclase was of relatively 
small extent. Most of the exposures are found in a 
linear belt extending from the Eeaper and Yellow 
Hammer claims, in Clifton Flat, to the U.S. mine. 
In this zone diopside, orthoclase, and other silicates 
are rather abundant and at a few places have almost 
completely replaced the original minerals of the quartz 
monzonite over large areas. Similarly altered rock 
is found in other localities but in the form of small 
isolated patches, 

Orthoclase is the most abundant and wide-spread 
mineral in this group. In most localities it is asso- 



IGNEOUS METAMOKPHISM 



95 



ciated with other minerals, but in several places it 
appears to occur alone. A short distance north of the 
Yellow Hammer mine irregular veinlets and splotches 
of pink orthoclase have replaced the quartz monzonite 
over a considerable area and constitute almost half 
of its volume. As seen in thin sections, the orthoclase 
is in the form of large crystals, much of it with a 
pseudopoikilitie habit due to the enclosure of incom- 
pletely replaced fragments of other minerals. Locally 
the orthoclase is replaced by white, finer-grained albite. 

Diopside is the next most abundant member of the 
facies. It is similar to that found in the metamor- 
phosed sedimentary rocks and replaces all the original 
minerals of the quartz monzonite. Its localization in 
the altered areas of the quartz monzonite shows clearly 
that it has been introduced after the consolidation 
of the intrusive. In many of the occurrences of this 
mineral it is either bordered or invaded along its 
cleavage lines by an amphibole near actinolite. The 
diopside is, in part at least, older than the orthoclase, 
for remnants of similar orientation may be found em- 
bedded in a single orthoclase crystal. 

Titanite in euhedral crystals is also wide-spread and 
might almost be considered to characterize the facies 
as well as diopside or orthoclase. In some places it 
has formed as a swarm of tiny crystals, but in others it 
occurs as larger grains adjoining diopside areas. 

Garnet was found only in the vicinity of the Frankie 
and Lucy L mines, where it is locally abundant. Its 
general absence contrasts with its wide-spread occur- 
rence in the altered limestone that contains silicates. 
Scapolite, epidote, and black tourmaline were noted 
in small amounts. The epidote and tourmaline are 
also found away from the metamorphosed areas coat- 
ing joints in the quartz monzonite. This habit of the 
tourmaline is especially striking in the bottom of the 
gulch northwest of United States mineral monument 
no. 11. 

In all the areas that have suffered the diopside- 
orthoclase alteration, minerals characteristic of the two 
other groups have replaced the minerals of this group. 
The diopside appears to have been particularly sus- 
ceptible to later alteration, and in many places it is 
almost completely altered to chlorite, calcite, or quartz 
or a mixture of these three minerals. 

Sericitization and chloriiization, — The most exten- 
sive area showing sericitization and chloritization lies 
east of and roughly parallel to the northward-sloping 
portion of Eodenhouse Wash, extending from hill 5675 
on the north to a point about half a mile north of 
Goshute Spring on the south. On the north this area 
extends much farther westward and encloses the 
greater part of the relatively low-lying country west 
of the Climax mine. This area of intense alteration 
is situated immediately west of a series of barren 
quartz and quartz-carbonate veins that dip at a rather 
low angle to the west and are thought to mark a zone 



of reverse faulting in the quartz monzonite after its 
consolidation (pp. 89-90). 

• Evidence of this alteration is also prominently dis- 
played in the quartz monzonite walls of the ore-bearing 
quartz veins, but in these the altered zone does not as 
a rule extend more than a few feet from the vein. The 
characteristic minerals are also developed in most of 
the exposures of the altered rock of the diopside- 
orthoclase phase. 

In the Eodenhouse Wash area the igneous texture is 
largely and in places completely destroyed, and the 
resultant rock is a rather pale greenish-gray fine- 
grained aggregate of sericite and chlorite, cut by 
reticulating veinlets of quartz. The microscope shows 
that the dark minerals are the first to be attacked, 
and these are followed by plagioclase, orthoclase, and 
quartz in the order named. In the less altered portions 
the outline of the former feldspar crystals is preserved 
by an aggregate of matted sericite of slightly different 
grain size than that in the remainder of the rock, but 
as the alteration becomes more intense even this 
remnant of the old texture is lost. The altered wall 
rocks of the veins are similar in appearance and 
composition. 

The relation between the sericite and chlorite is 
not clearly understood from the specimens studied. 
In the less altered rocks chlorite tends to be localized 
in the original dark minerals and sericite in the feld- 
spars, but in the more highly altered rocks this is not 
true. From the several specimens in which the two 
minerals are in contact it is difficult to determine then- 
relative age. In some places remnants of chlorite 
appear to be enclosed within masses of sericite and 
might therefore be thought to be earlier. In other 
places veinlets of quartz and chlorite cut across sericite 
areas and must be later. Finally, in several specimens 
the relations observed might be interpreted to indicate 
that either one or the other of the two minerals was 
formed first. These relations seem to be most easily 
explained by assuming that the two are essentially 
contemporaneous and that locally, depending upon the 
physico-chemical conditions, either mineral may have 
replaced the other. 

Sericite is the more abundant of the two minerals. 
The proportion varies widely in different specimens, 
and in places either one may be present to the exclusion 
of the other. By a rough estimate, whose only value 
lies in indicating the order of magnitude, sericite is 
between 5 and 10 times as abundant as chlorite. 

Introduced quartz and calcite are found in many of 
these altered rocks. Almost all of the quartz is clearly 
later than the chlorite and sericite, cutting across them 
as veinlets or replacing them in bulk. It is similar in 
appearance and habit to the jasperoidal alteration 
product next described. 

Silicijication. — Silicification of the quartz monzo- 
nite, corresponding to the formation of jasperoids in 



96 



GOLD HILL MINING DISTRICT, UTAH 



the sedimentary rocks, has occurred, for the most part, 
on a microscopic scale. The only place where it was 
found to have occurred on a large scale was under- 
ground in the Western Utah Copper Co.'s Gold Hill 
mine, where a rather large mass is exposed at several 
places along the western contact Of the limestone with 
the quartz monzonite. The partial replacement of the 
quartz monzonite by microscopic quartz appears to 
have been rather wide-spread in the region between 
Lucky Day Knob and Gold Hill and is shown with 
particular abundance in specimens taken in the 
vicinity of ore bodies. 

The silicified rock differs from the jasperoid tex- 
turally. It is almost invariably somewhat coarser 
grained, and only one of the specimens examined 
showed the successive generations of quartz that are 
so marked a feature of the jasperoids. Vugs are 
almost entirely lacking. The silicification produced 
either veinlets cutting the quartz monzonite or 
irregular masses of quartz that form a matrix around 
the remnants of unattacked minerals. In one specimen 
showing almost complete silicification the quartz grains 
instead of having their usual anhedral habit, are in the 
form of laths, which show in some places a subparallel 
orientation (pi. 9, A). 

Sericite, chlorite, barite, and an iron-rich carbonate 
are in places associated with the quartz. The chlorite 
may be either green or colorless in thin section, but 
the colorless variety is the more characteristic. It is 
difficult to determine definitely whether or not the 
sericite and chlorite are invariably earlier than the 
quartz or are in part contemporaneous with it. Some 
of the specimens suggest strongly that small amounts 
of these minerals are of the same age as the quartz. 
Barite was recognized in only one specimen, as 
microscopic crystals within a veinlet of the fine-grained 
quartz. The carbonate, which is in part at least an 
ankerite (index of refraction of w near 1.70), occurs as 
megascopic rhombs in the quartz or as veinlets cutting 
the quartz. Barite and ankerite were both found with 
quartz in the same veinlet and were presumably de- 
posited at the same time. These minerals were not 
seen in quartz containing what was thought to be 
contemporaneous chlorite or sericite, however, and it 
is suggested that the silieifieation continued over a 
considerable period of time, in the early stages of 
which chlorite and sericite were deposited and in the 
later stages barite and ankerite. 

COMPARISON Of THE ALTERATION OF THE SEDIMENTARY 
ROOKS AND THE QUARTZ MONZONITE 

In comparing the results of the metamorphism of 
the sedimentary rocks and that of the quartz monzo- 
nite, three features may be noted that appear to bear 
upon the process — the phases of alteration bear defi- 
nite time relations to one another; the phases recog- 
nized in the quartz monzonite overlap to a far greater 
extent than those in the sedimentary rocks; and phases 



that are prominent in the one may be absent or un- 
important in the other. 

The first of these observations has been emphasized 
in the descriptions of the individual phases, and the 
consistency with which all the specimens collected 
showed the same succession appears to warrant the 
generalization that the metamorphism was accom- 
plished over a relatively long period of time, during 
which the conditions under which the alterations took 
place changed progressively in such a way that period- 
ically groups of minerals already formed were no longer 
stable and were replaced by a new set. 

The three phases that were distinguished in the 
alteration of the quartz monzonite not only overlap 
spatially to a marked degree, but there also appears to 
be a mineralogic overlap between the second and third 
phases. These two features are only rarely observed 
in the altered sedimentary rocks. The cause of this 
distinction is not entirely clear, but it seems most 
reasonable to infer that it is the result of an essentially 
continuous passage of the metamorphosing fluids 
through the major fractures in the quartz monzonite, 
from which they were derived, as opposed to a dis- 
continuous flow through the outlying sediments. 

The fact that phases present in the quartz monzo- 
nite may be essentially lacking in the sediments, or 
vice versa, is probably in large part the result of the 
different composition of these two kinds of rock. The 
lack in the igneous rock of a corresponding phase to 
the recrystallization in the sediments obviously cannot 
be explained in this way but is better interpreted as 
indicating that the quartz monzonite was still largely 
molten at the time of recrystallization. The silicate 
alteration of the sedimentary rocks was clearly very 
similar to the diopside-orthoclase alteration of the 
quartz monzonite— so similar, in fact, that it is almost 
impossible to distinguish the intrusive contact in 
places where this kind of alteration has taken place. 
There is, however, a distinction between them that 
appears to have a bearing on the later alteration — 
the absence of orthoclase in the altered limestones. 
This is clearly the result of the low alumina content 
of the unaltered limestone. Eskola 21 has shown 
that rocks in which the alumina content is too low 
to permit the development of feldspar commonly 
contain garnet. Conversely, the relative rarity of 
garnet in the quartz monzonite appears to show that 
it contained sufficient alumina to satisfy the K 2 
content of the solutions causing metamorphism. 

The wide-spread sericite-chlorite alteration of the 
quartz monzonite is for the most part lacking or only 
sparsely developed in the sediments. If this phase is 
considered to be the result of the hydration of older 
aluminous silicates of magnesium, iron, or potassium, 
it is apparent that the explanation may be found in 
the fact that such silicates are far more abundant 



« Eskola, P., The mineral fades of rocks: Norsk, gaol. Tldsskrift, vol. 8, pp. 143- 
194,1920. 



U.S. GEOLOGICAL SUHVKY 



PROFESSIONAL PAPEH 177 PLATE 8 





...:.- ■ *:•. ■ *V >>.'.. j;'--:- " **ft 





A. WOLLASTONITE (w) REPLACING GARNET (g) IN METAMORPHOSED 
OCHRE MOUNTAIN LIMESTONE. 



B. JASPEROID FROM THE U.S. MINE, WITH INCLUSIONS OF 

OPAL IN QOAHTZ. 

Plain light. Opal is mineral with high relief. 














^^^BB?87 



6". WOLLASTONITE REPLACED BY SPADA1TE. 
Plain light, w, W r olla»tonite remnants. 



D. PRESERVATION OF CALCITE CLEAVAGE LINES IN JASPEROIIX 



U.S. GEOLOGICAL SURVEY 



PROFESSIONAL PAPER 177 PLATE 




A. ELONGATED QUARTZ GRAINS IN SILICIFIKD QUARTZ MONZONITE, SHOWING TENDENCY TOWARD PARALLEL ORIENTATION. 

Grossed nicols. 

B. SUCCESSIVE REPLACEMENTS IN A SPECIMEN FROM THE TUNGSTEN-BEARING PIPE ON THE REAPER CLAIM. 

Plain light, e, Ejudote; <i, diopside; a, amphihole; ap, apatite; c, caleite. 

C. APATITE (ap) AND MOLYBDENITE (m) IN AMPHIBOLE, FROM REAPER CLAIM. 



ORB DEPOSITS 



97 



in the igneous rock than they are in either the 
altered or unaltered limestones or sandstones. The 
relation of dolomitization to composition is of course 
obvious. 

The course of the metamorphism may be summa- 
rized as follows: Coincident with the intrusion of the 
quartz monzonite, the invaded sedimentary rocks 
were subjected to a wide-spread recrystallization and 
bleaching, which appears to have been induced by 
circulating fluids, probably propelled by the heat of 
the magma and certainly impeded in their progress by 
such relatively impermeable material as the fault 
breccia along the Ochre Mountain thrust. After the 
consolidation of the now exposed portions of the in- 
trusive rock, solutions containing large quantities of 
silica, potash, iron, and magnesia and probably small 
quantities of alumina traveled along fractures and 
reacted with both the intrusive and the invaded rocks, 
forming a group of minerals characterized by diopside, 
orthoclase, and garnet. Smaller quantities of minerals 
containing the so-called "volatile constituents" of the 
magma, such as scapolite, tourmaline, and axinite, 
were also formed at this time, apparently somewhat 
later than, the bulk of the other minerals. After the 
deposition of these minerals the alteration became 
essentially one of hydration, and large areas in the 
quartz monzonite were converted to rocks containing 
much chlorite and sericite. This phase is almost lack- 
ing in the sedimentary rocks, probably because of 
their composition. Still later the solutions, becoming 
cooler, appear to have lost their corrosive power and 
instead deposited silica, much of it apparently in a 
gelatinous form, which afterward largely recrystal- 
lized to quartz. The final stage in the metamorphism 
resulted in the dolomitization of limestone, at con- 
siderable distances from the intrusive mass but clearly 
related to fracturing. This phase appears to be 
related to veins of quartz and ferruginous dolomite 
that cut the quartz monzonite and are later than the 
other products of alteration. 

OBE DEPOSITS 

The ore deposits found within the Gold Hill quad- 
rangle differ from those of many other mining districts 
in that they are not closely similar deposits, which may 
be described as a group. On the contrary, the greater 
number of the explored ore bodies differ from one 
another to a marked degree, both as to form and as 
to composition. Hence, a general treatment of the ore 
deposits must be in the nature of a series of descrip- 
tions of individual ore bodies. As another section of 
this report (pp, 119-168) contains detailed descriptions 
of the mines and prospects, the descriptive part of this 
section is rather more brief than might otherwise be 
considered desirable and is designed to show primarily 
the relations that exist between the several kinds of 
deposits rather than their individual characteristics. 



Headers desiring more information about a particular 
type of deposit are therefore referred to the detailed 
descriptions and also to the sections on superficial 
alteration and mineralogy (pp. 104-107, 110-118). 

CLASSIFICATION 

As the ore bodies within the quadrangle include 
representatives of several different kinds of deposits, 
which vary not only in mineralogy but also in form, 
it is desirable first of all to classify them in order that 
they may be described systematically. Three methods 
of classification have been used more or less generally — 
one based on the metal present, a second based on the 
form of the deposit, and a third that utilized the sup- 
posed temperature of formation of the deposit, often 
referred to as a "genetic" classification. The first of 
these is scarcely applicable to this area, for not only 
do many of the ore bodies contain minerals of several 
different metals, but several of the metals are found in 
utterly unlike kinds of deposits. Neither of the other 
two methods of classification is entirely satisfactory, 
because, if they are applied rigidly, they result either 
in the separation of rather closely related types of 
deposits or in the combination of unlike types. This 
difficulty is, of course, inherent in any system based 
on a single factor that attempts to classify objects 
that vary in several different ways. The following 
classification of the ore bodies found in the quad- 
rangle is essentially a combination of the second and 
third methods noted above, with the primary emphasis 
placed upon form: 

1. Pipelike deposits locally containing tungsten and molyb- 

denum. 

2. Veins: 

(a) Veins characterized by silicate minerals in the 

gangue. 

(b) Veins containing chiefly quartz and metallic 

sulphides. 

(c) Veins containing chiefly carbonate minerals with 

or without quartz. 

3. Replacement bodies: 

(o) Arsenic minerals dominant. 

(6) Copper-lead-silver minerals dominant. 

The replacement bodies have furnished by far the 
greater part of the production recorded from the 
Clifton district. The pipelike deposits yielded small 
quantities of tungsten ores during the period of high 
tungsten prices; small quantities of tunpten and 
copper and moderate amounts of gold have been 
produced from the silicate veins; and a fair tonnage 
of lead-silver ore was obtained from the quartz veins 
in the earlier part of the district's existence. 

PIPEIIKE DEPOSITS 

The ore bodies belonging to the first group are peg- 
matitic masses in the quarts monzonite that have a 
tubular or pipelike habit. The few deposits of this 
kind occur almost entirely in the nearly level stretch 
of country immediately north of the town of Clifton, 



98 



GOLD HILL MINING DISTBICT, UTAH 



but a few are present in other areas underlain by the 
intrusive rook. 

The largest and best-known representative of the 
group is the tungsten-bearing pipe on the Reaper 
claim. This ore body had an elliptical cross section 
at the surface, with a long axis of nearly 60 feet and a 
short axis of about 30 feet. On the 50-foot level it was 
considerably smaller and had a circular outline, with a 
diameter of about 20 feet. On this level there are two 
apophyses from the pipe, one extending to the north- 
west and the other to the north-northeast. The 
pipelike habit persists only a short distance below this 
level, however, for on the bottom or 100-foot level the 
ore shoot has a lenticular shape, striking northeast. 
Smaller pipes were observed on the Centennial, Enter- 
prise, and Doctor claims and on the property of the 
Yellow Hammer mine. In these the tubular form is 
clearly the result of localization of mineralization at 
the junction of two intersecting fractures, along both 
of which apophyses may extend for short distances 
away from the pipe. None of these pipes have been 
sufficiently developed to show whether or not the 
tubular habit changes downward to a veinlike habit, 
but it is perhaps significant that on all these claims 
there are veinlike masses of similar composition. 

The walls of the pipes are not well defined, for not 
only are there numerous irregular projections of 
pegmatitic minerals from the pipe into the wall rocks, 
but in many places there are isolated occurrences of 
these minerals in the quartz monzonite adjacent to 
the pipe. The igneous rock itself is rather thoroughly 
altered for some distance from the ore bodies. Two 
kinds of alteration were recognized. One has resulted 
in the formation of a rock of striking appearance but 
was quantitatively of relatively little importance. It 
consisted in the development in the quartz monzonite 
of pink perthitic orthoclase and a green amphibole 
that is near actinolite in its optical properties. Both of 
these minerals are also found in the pipes, but there 
they are much more coarsely crystalline. This phase 
of alteration, however, was not everywhere closely 
related in space to the pipes but locally took the form 
of irregular replacements of the igneous rocks some 
distance away from the pipes. The second and more 
wide-spread kind of alteration produced sericite, 
chlorite, and calcite in the quartz monzonite adjacent 
to the ore body. 

Both Butler n and Hess 2% have referred to these 
deposits as pegmatites, and, if variety of minerals and 
a large size for individual crystals are considered as 
characterizing pegmatites, these bodies may well be 
called by that name. 

The two most abundant minerals in the pipes are 
orthoclase and amphibole. Cleavage faces of perthitic 
orthoclase may be more than a foot across. The 



» Butler, B. S., Ore deposits of Utah: U.S. Geol, Survey Prof. Paper 111, pp. 476- 
477, IBM. 
» Hess, F. L., Molybdenum deposits: U.S. Geol. Survey Bull. 781, p. 5, ISM. 



mineral is pink, in contrast to the white albite that 
locally has replaced it. The amphibole is actinolite 
and occurs as sheafs of crystals as much as 4 feet in 
length. Much of it is partly altered to micaceous 
minerals, calcite, and quartz, but even in these the 
amphibole cleavage is preserved. Black tourmaline is 
also abundant but tends to be found near the borders 
of the pipes, where it is generally accompanied by 
clear glassy quartz. Smaller amounts of diopside, 
epidote, titanite, zircon, garnet, and scapolite have 
also been recognized among the silicate minerals 
forming the pipes. 

Scheelite is the most abundant of the nonsilicate 
minerals. Very little scheelite could be found in the 
prospects at the time of this examination, but Butler, 
who examined the district before the active exploita- 
tion during the war, writes that on the Reaper claim 
"a body composed largely of scheelite 18 to 24 inches 
in thickness had been exposed for 4 or 5 feet along the 
strike and 3 or 4 feet below the outcrop. The scheelite 
occurs in large crystals, some of which are 4 inches long. 
One block of nearly pure scheelite on the dump was 
estimated to weigh fully 200 pounds." 2i 

Apatite is also abundant in euhedral crystals that 
are commonly embedded in the actinolite, particu- 
larly near the base of the sheafs. Much of it at first 
glance resembles scheelite, but it lacks the cleavage 
commonly found in the tungsten mineral. Molybde- 
nite occurs as small rosettes and is locally rather abun- 
dant. Chalcopyrite, pyrite, magnetite, and specula- 
rite may also be recognized in small amounts. 26 Gold 
is reported to occur in the pipes, and its presence is 
said to have led to the development of the pipe on the 
Reaper claim. 

There is some question as to the propriety of calling 
these deposits pegmatites, for the evidence is clear 
that the minerals were introduced by a long series of 
replacements, first of the country rock and later of the 
earlier-formed replacing minerals. The localization of 
the pipes along intersecting fractures alone suggests an 
origin by replacement, and specimens taken at the 
borders confirm this view in that they show the 
minerals of the pipe embaying and replacing the min- 
erals of the quartz monzonite. The fact that isolated 
patches of the introduced minerals are found in the 
walls of the pipes is also difficult to explain except by 
replacement. 

The exact sequence in which the minerals forming 
the pipe were deposited cannot be ascertained from the 
specimens collected. A fair amount of information is 
available, however, and may be summarized as follows: 
Epidote and titanite were among the first minerals to 
form, as they have replaced the minerals of the quartz 
monzonite and have been replaced by other constit- 



» Butler, B. S., op. eit., p. 476. 

! « Photographs illustrating the occurrence of scheelite and molybdenite in deposits 
of this type in the Gold Hill area are included in two reports by F. L. Hess (Tungsten 
minerals and deposits: U.S. Geol. Survey Bull. 652, pis. 12, A; 18, A, B, 1907; Molyb 
denum deposits: U.S. Geol. Survey Bull. 761, pi. 5, B, 1924). 



OBE DEPOSITS 



99 



uents of the pipes. Zircon may be contemporaneous 
with them, and also possibly scheelite, of which Butler 
writes, "The scheelite was one of the earliest minerals 
to form. Much of it is in well-formed crystals, and 
little of it includes the other minerals." 26 The epidote 
and titanite are definitely earlier than diopside in a 
specimen from the Reaper claim, but this mineral is 
relatively rare. It is probable that the equally sparse 
garnet found in the pipes is also of this stage. The 
diopside in turn is replaced by actinolite along its 
cleavage planes (pi. 9, B). In other specimens actino- 
lite appears to have formed immediately after epidote 
and titanite, without an intervening stage in which 
diopside was formed. Apatite and molybdenite are in 
many places associated with the sheafs of amphibole 
and are possibly of about the same age, although they 
generally appear to replace the amphibole (pi. 9, (J), 
as they interrupt and embay individual crystals. 

In all the specimens in which actinolite and ortho- 
clase are in contact, orthoclase is clearly later, for it 
corrodes the amphibole and locally includes oriented 
remnants of it. Orthoclase in turn has been replaced 
by albite, in the few places that this mineral was 
recognized. The next mineral to form appears to have 
been tourmaline, with which is generally associated 
some glassy quartz that must have been developed 
somewhat later. The greater part of the tourmaline is 
dense black and rather coarsely crystalline, but locally 
this variety is replaced by a much finer grained blue 
tourmaline. The last stages in the formation of the 
pipe were the introduction of sericite, chlorite, calcite, 
and quartz. The sericite and chlorite are generally 
accompanied by either calcite or quartz or both, but 
these two minerals also continued to form for some 
time afterward. The sulphide minerals are associated 
with this group of minerals. 

The pipes are associated with veinlike bodies of 
similar mineral composition, and the large pipe in the 
Reaper claim changes downward into a deposit of 
veinlike form. This relation of the pipes to veins may 
be a result of proximity to the upper surface of the 
intrusive, which acted to dam the solutions forming the 
pipe and caused them to spread beyond the fissure to 
which they were limited at greater depths in the 
intrusive. That this may be the explanation is indi- 
cated by the localization of the pipes in the region 
north of Clifton, where it is clear, from exposures in 
the surrounding hills, that the original, nearly flat top 
of the intrusion must have been only a short distance 
above the present surface. 

VEINS WITH SILICATE MINERALS IN THE GANGUE 

Three subclasses of the veins with silicate minerals 
in the gangue may be distinguished for purposes of 
description, but there are almost continuous gradations 
between them. 



» Butler, B. S., op. cit., p» 476. 



The first subclass includes the lenticular or vein- 
like bodies that are associated with the tungsten- 
bearing pipes. They are mineralogically similar to the 
pipes, except that the size of individual crystals tends 
to be smaller and the content of scheelite is probably 
distinctly lower. 

The second subclass is found both in the quartz 
monzonite and in the sedimentary rocks and is char- 
acterized by a general fine-grained habit of the silicate 
minerals and by the general dominance of copper over 
tungsten as the valuable metallic constituent. These 
veins are restricted to the region between the Lucy L 
mine on the north and the town of Clifton on the south. 

These veins vary considerably in form, ranging from 
the rather small lenticular masses found in places on 
the Gold Bond claim and the Copper Bloom group to 
the persistent lode on the Frankie claim, which has 
been developed for several hundred feet. All of them, 
however, appear to have been localized by earlier frac- 
tures or narrow sheeted zones. Some of these frac- 
tures give evidence of having been reopened over a 
long period of time. Thus the vein on the Frankie 
claim is in a narrow dike of quartz monzonite which 
was intruded along a fault that was active at a period 
long prior to the intrusion. After the intrusion, Assur- 
ing along the same line permitted the introduction 
of the silicate minerals, which in turn were cut by 
closely spaced parallel fractures, in which copper min- 
erals are concentrated. 

Mineralogically these veins show a rather wide vari- 
ation, and one vein may contain one or more minerals 
in abundance that are almost or entirely lacking in 
an adjacent vein. In general, epidote, titanite, and 
scheelite, which are thought to have been among the 
earliest minerals to form in the pipelike deposits, are 
relatively scarce in these veins. Garnet is particularly 
abundant, however, and with diopside appears to have 
been among the earliest minerals to form. Amphibole 
is distinctly later but is irregularly distributed, being 
very scarce in some of the deposits, particularly on the 
Gold Bond claim. Orthoclase also is of rare occur- 
rence. 

Tourmaline is wide-spread, and in some of the depos- 
its, as in the Keno, Pole Star, and Copper Bloom 
claims, it was the only silicate mineral observed. Most 
of the tourmaline occurs as black bladed crystals, 
similar to those found in the pipes, and there is in 
addition some finer-grained blue tourmaline that is of 
somewhat later development. In the Gold Bond de- 
posits specularite is widespread and is clearly later 
than tourmaline (pi. 10, B). 

The next minerals to be formed are characterized 
by the presence of boron, chlorine, and fluorine and 
include danburite, humite, scapolite, and fluorite. 
These minerals are surprisingly abundant, the vein- 
like occurrences of danburite in the Gold Bond claim 
being nearly a foot across and similar masses of humite 
on the Calaveras claim being several inches thick. 



100 



GOLD HILL MINING DISTRICT, TJTAH 



These minerals are clearly later than the other silicate 
minerals except sericite, and on the Gold Bond claim 
danburite and fluorite corrode and embay specularite 
(pi. 10, A). 

The final stage in the mineralization consisted in the 
introduction of small amounts of sericite, calcite, 
quartz, and the metallic sulphides, which have all re- 
placed the older silicate minerals. Chalcopyrite is by 
far the most abundant sulphide, and most of the pros- 
pecting on these deposits has been for copper. Gold 
is present in small quantities in all of them, and in a 
few properties it has been the sole element present in 
anything approaching economic amounts. Pyrite is 
wide-spread in small amounts, and locally bismuth- 
inite is fairly abundant. Tetrahedrite was recognized 
on the Copper Bloom group, and grains of galena and 
sphalerite were recognized on the Lucy L and Gold 
Bond claims, respectively. 

There is an obvious similarity in mineralogy and 
habit between the veins of this subclass and those of 
the first subclass. The chief differences between them 
appear to be a somewhat finer grain size, a general 
lack in deposits of the second subclass of the earlier- 
formed minerals in the first subclass, and a greater 
variety and abundance of sulphide minerals in the 
deposits of the second subclass. Similarly there is a 
rather close relationship between the veins of this sub- 
class and those of the third subclass. 

The veins of the third subclass have been exploited 
for their gold content. They are more widely distrib- 
uted than those of the first two subclasses, although 
they appear to be considerably less abundant. They 
are restricted to limestone beds near the contact of 
the sedimentary rocks with the quartz monzonite. In 
all of them the gold ore is found in relatively small 
shoots that appear to be localized along minor struc- 
tural features, such as linear igneous contacts, as in 
the Alvarado and the Eube mines, or along fractures 
parallel to the bedding, as in the Cane Springs and 
Midas mines. 

The Cane Springs, Alvarado, Midas, and two smaller 
deposits are very similar in character and may be 
considered as a unit. The ore is found in limestone 
that has been almost completely altered to silicate 
minerals and resembles very closely similarly altered 
limestones that are wide-spread throughout the district. 
Zoisite and vesuvianite are relatively rare constituents 
of the rock and appear to have been the first minerals 
to form during the alteration. They were succeeded 
by equally small amounts of garnet and diopside. 
The bulk of the rock in all the mines, however, is made 
up of white bladed wollastonite which is invariably 
later than the other silicates. This in turn has been 
widely altered to spadaite (see pi. 8, B). 

The last stage consisted of the introduction of the 
metallic sulphides with quartz and calcite. The 
observed relations between the quartz and calcite indi- 



cate either that there were several generations of each 
or that conditions of temperature and pressure varied 
so that first one and then the other might be deposited. 
Chalcopyrite is by far the most abundant sulphide, 
but the quantity found varies in the different mines. 
It is relatively abundant in the Cane Springs mine 
and rather scarce in the Alvarado. Pyrite, bornite, 
arsenopyrite, and galena have also been recognized in 
the ore specimens. Molybdenite has been reported 
from the upper levels of the Cane Springs mine, but 
its relations to the other sulphides are not known. It 
is extremely probable that the gold in the ores of these 
mines is essentially contemporaneous with the quartz, 
calcite, and sulphides, for all the specimens of ore that 
were examined contained some of these minerals. On 
the 200-foot level of the Alvarado mine several small 
pipes of ore were stoped that were not connected with 
the main shoot, and in these there were apparently 
practically none of the silicate minerals that form so 
large a proportion of the other ore shoots. The gangue 
in these places was composed almost entirely of quartz 
and calcite. Kemp has described ore from the Cane 
Springs mine in which gold was embedded in some of 
the silicate minerals, 27 and there may therefore be 
some occurrences of the mineral that are not related to 
the introduction of quartz. It seems very improbable, 
however, that the amount of such gold is very great. 

The ore at the Eube mine is somewhat different from 
that described above. Most of it is composed of lime- 
stone, partly or completely replaced by quartz, sericite, 
calcite, and several metallic minerals, among which 
gold, pyrite, and galena are the most abundant, al- 
though chalcopyrite, spalerite, pyrrhotite, and arsen- 
ical boulangerite have also been recognized. Bismuth 
is shown by analysis of the ore, but no bismuth min- 
erals were recognized in the specimens collected. One 
portion of the new ore shoot in the mine, however, was 
of radically different composition and appears to pro- 
vide a connecting link between the Rube and the other 
deposits in this subclass. This part of the shoot con- 
tains as the earliest-formed minerals small quantities 
of zoisite, scapolite, and muscovite and rather large 
quantities of molybdenite. These have been replaced 
by green and colorless chlorite, which with calcite, 
makes up a large part of the rock. Pyrite is also 
abundant, particularly near the borders of this phase 
of the ore, but quartz is relatively rare. 

The remaining deposit in this subclass is that on the 
property of the Wilson Consolidated Mining Co. Here 
a bed of limestone intercalated between sandstones 
contains a small shoot of ore locally rich in gold and 
bismuth. The bulk of the ore is composed of coarsely 
crystalline white calcite, undoubtedly derived from 
the original limestone, in which are veinlets and 
euhedral crystals of quartz (pi. 10, D). Locally small 

«' Kemp, J. F., Notes on Gold Hill and vicinity, Tooele County, western Utah: 
Eeon. Geology, vol, 13, p, 398, 1918. 



ORE DEPOSITS 



101 



quantities of orthoclase and sericite are also found. 
Bismuthinite, scheelite, and native gold were the only 
hypogene metallic minerals recognized. 

This class of veins with silicate minerals in the 
gangue present an almost continuous sequence from 
the pipelike deposits in which silicate minerals are 
dominant and quartz, carbonates, and sulphides are 
relatively rare to deposits like the Copper Bloom or 
Wilson Consolidated, in which the silicates have been 
reduced to a single variety, and the bulk of the ore is 
composed of quartz, carbonates, and sulphides. The 
transition is marked more or less definitely by a 
uniform decrease of the earlier-formed minerals and 
a comparable increase in the younger ones. In all the 
deposits there is a clear dependence of localization 
upon earlier-formed fractures. On the other hand, 
there is relatively little relation between the character 
of the ore and the character of the wall rock, except 
for the obvious restriction of wollastonite and other 
lime-rich silicates to deposits formed in limestone. 

VEINS CONTAINING CHIEFLY QUARTZ AND METALLIC 
SULPHIDES 

The veins characterized by quartz and metallic 
sulphides are found chiefly in the quartz monzonite, 
but some are known to occur in the sedimentary rocks. 
They have a wide distribution throughout the intrusive 
mass, showing no discernible tendency toward locali- 
zation. The veins are found along fissures, many of 
which can be definitely proved to be minor faults, or, 
as in the Cyclone mine, along dikes. Most of the veins 
show a postmineral gouge along one or both walls. A 
general northerly strike and westerly dip are charac- 
teristic, but exceptions to both are not uncommon. 

Sericite, chlorite, and quartz have been introduced 
into the quartz monzonite where it forms the wall 
rock of the veins, but it is in most places impossible 
to determine the amount of such alteration that may 
be attributed to vein formation, because of the min- 
eralogically similar regional alteration of the igneous 
rock. There appears to have been essentially no 
alteration of the wall rock adjacent to the few veins 
that occur in the sedimentary rocks. 

Like those of the preceding class, these veins are 
rather variable in mineral composition. The varia- 
tions, however, are expressed in the metallic minerals 
present, and there appears to be a rather complete 
series showing the stages in the variation. 

A subclass that, appears to be most closely related 
to the veins described in the preceding section is 
typified by the bismuth-bearing gold quartz vein on 
the Lucy L group of claims. This deposit is a lenticu- 
lar bod3^ of quartz containing bismuthinite and native 
gold, enclosed in quartz monzonite. The greater 
abundance of quartz and the absence of orthoclase 
definitely distinguish this ore from the gold-bismuth 
ore at the Wilson Consolidated mine, but there is 
obviously a rather close resemblance between them. 



A second subclass contains arsenopyrite and quartz. 
Such veins are fairly abundant throughout the quartz 
monzonite area, but, except for the one on the Boston 
claim, they have been only slightly developed. The 
Boston vein contains also small quantities of other 
sulphides and in addition is reported to carry $14 to 
the ton in gold. 

The most abundant veins in this class and about the 
only ones that have yielded any significant tonnage 
of ore are the quartz veins containing the sulphides of 
the base metals. The Cyclone, Success, and Southern 
Confederate veins are representative of this subclass. 
They are restricted to the quartz monzonite but are 
scattered over the greater part of its outcrop. Many 
of these veins may be traced for long distances along 
their strike, but ore shoots have proved to occur rather 
sparingly and to have rather small dimensions. 

The ore contains arsenopyrite, pyrite, sphalerite, 
galena, chalcopyrite, arsenical tetrahedrite or anti- 
monial tennantite, and aikinite, the lead-bismuth sul- 
phide. These sulphides are rather erratically dis- 
tributed throughout the ore shoot, one predominating 
in some places and another in others. In polished 
sections arsenopyrite is seen to have been the earliest 
sulphide to form, as it has in most places been thor- 
oughly fractured and cemented by quartz and the 
other sulphides (pi. 10, E). Quartz is the only abun- 
dant gangue mineral, but fragments of altered wall 
rock are not uncommon constituents of the veins. 
Veinlets of an iron-rich carbonate cut both quartz 
and sulphides. 

The final subclass of veins in this group has fur- 
nished small quantities of rather rich ore. They are 
quartz-tetrahedrite veins, in which the only metallic 
minerals are arsenical tetrahedrite, which is rich in 
silver, and small quantities of galena. One of these 
veins occurs in the quartz monzonite on the Undine 
claim, but the others are in sedimentary rocks, the 
bulk of them being found on the northern and north- 
western slopes of Dutch Mountain. A variety of this 
subclass is represented by a tetrahedrite-galena vein 
on the Reaper claim south of the open cut. This 
contained barite in the gangue, in addition to quartz, 
and is thus a connecting link between these veins and 
those of the next class. 

VEINS WITH CARBONATE OB SULPHATE MINERALS IN THE 
GANGUE 

The veins that have carbonate or sulphate minerals 
in the gangue are of relatively little economic impor- 
tance but are described here because they appear to 
represent the final stages in the mineralization of 
the area. They are rather widely distributed through- 
out the quartz monzonite and the adjacent sedimentary 
rocks. Many of the veins follow older structural fea- 
tures. Thus the quartz carbonate veins in Roden- 
house Wash are thought to occupy a zone of probable 
thrust faulting (pp. 89-90) ; and carbonate veins on the 



102 



dOLD HILL MINING DISTRICT, UTAH 



north and south sides of Montezuma Peak follow linear 
contacts of the quartz monzonite with the sediments, 
which in turn were determined by old faults. On 
the Monocco claim a carbonate vein has been intro- 
duced along an older lead-bearing fissure. 

The veins with carbonates in the gangue show a 
considerable variety in composition, ranging from those 
in which the carbonate is relatively scarce and quartz 
predominant to those in which carbonates form the 
bulk of the rock and quartz is essentially absent. 
In many places the wall rocks of the veins in which 
carbonate minerals are in excess contain isolated crys- 
tals of the carbonate. 

The most striking feature of these quartz-carbonate 
veins is their texture. Almost all of them show a 
banding that is locally parallel to the walls of the veins 
but in most places is rosettelike or colloform. In 
some specimens such curved banding clearly reflects 
the outlines of inclusions of altered quartz monzonite 
(pi. 10, <7), but in many of them no inclusions can be 
found. Thin sections of the veins show remnants of 
different sizes of sericitized and chloritized quartz 
monzonite, replaced by several generations of quartz 
and carbonate. The carbonate is iron-bearing in al- 
most all specimens, but the proportions of iron, mag- 
nesium, and calcium in the mineral appear to vary 
widely. For example, one specimen had indices of 
refraction indicating a content of more than 75 percent 
of FeC0 3 , and, at the other extreme, the carbonate 
from a vein in Rodenhouse Wash had much less than 
25 percent. Small quantities of sulphides occur in 
some of the veins, but their presence is unusual. They 
appear to be limited to veins that contain relatively 
small amounts of carbonate. An occurrence of a 
pocket of rich gold ore is reported in one of these veins 
on the Troy claim, but there appears to be some doubt 
as to the validity of the discovery. (See p. 151.) 

Barite veins are not abundant and are limited to 
areas of Ochre Mountain limestone near the quartz 
monzonite contact. The two regions in which they 
were found in any quantity were on the southeast side 
of Ochre Mountain and on the northeast side of the 
large roof pendant north of Clifton. In both of these 
places they are more or less closely associated with a 
jasperoid resulting from alteration of the limestone. 
In the Ochre Mountain occurrence the veins are con- 
trolled by lines of faulting but in many places spread 
out from the fault and replace the limestone. The 
barite is coarsely crystalline and has a platy habit. 
Where pure it is creamy white, but most of it has a 
dull-gray color due to inclusions. These veins have 
been practically unexplored, but it seems probable that 
a moderate quantity of fairly pure material might be 
exposed by a small amount of work. 

ABSENIC BIPIACIMINT BODIES 

The arsenic replacement bodies have been developed 
in only two mines in the quadrangle — the Gold Hill 



mine of the Western Utah Copper Co. and the Gold 
Hill mine of the United States Smelting, Eefining <fc 
Mining Co. (locally known as the U.S. mine). The 
ore bodies in these mines are the largest ones in the 
Clifton district and have furnished a large part of the 
ore produced. 

In both mines the deposits are found within the 
Ochre Mountain limestone in roof pendants enclosed 
in quartz monzonite. The preference for the unaltered 
limestone as a site of ore deposition is striking, for 
wherever there has been extensive formation of silicate 
minerals, or where more siliceous rocks, such as the 
Manning Canyon or Oquirrh formation or the quartz 
monzonite, abut against the ore body, there is an 
almost complete lack of arsenic mineralization. Two 
other factors appear to have played an important part 
in determining the localization of the deposits. One 
of these is the presence of a major fracture through 
which the ore-bearing solutions could have traveled 
across the strike of the beds, and the other is the occur- 
rence of one or more fissures essentially parallel to the 
bedding. The second factor appears to be required 
by the fact that locally unmineralized limestone beds 
may be found adjacent to the ore bodies in both mines, 
and that, in the U.S. mine at least, the beds which 
have been replaced are cut by minor faults parallel to 
the bedding. The combination of these two factors 
produces an ore shoot with a roughly triangular plan, 
the base of the triangle being the crosscutting fracture 
and the altitude being represented by the fracture 
parallel to the bedding. It would seem that these 
features show that the ore solutions found it difficult 
to react with the limestone for more than a relatively 
short distance away from the fractures through which 
they could circulate freely. 

Most of these arsenic-rich ore bodies are, in their 
unoxidized portions, made up of arsenopyrite. In a 
few places this sulphide has a bladed structure (pi. 1 1 , 
A), and this habit is also shown by isolated crystals 
of the mineral in unaltered limestone adjacent to the 
ore. No gangue minerals contemporaneous with the 
arsenopyrite have been recognized in this material. 
Most of the massive arsenopyrite, however, lacks the 
bladed habit and is apparently textureless when seen 
underground. Polished specimens of this kind of ore 
show that it is the result of a thorough brecciation by 
which almost all trace of the original bladed habit was 
destroyed. Small amounts of pyrite appear to have 
been introduced during the brecciation, for in many 
places this mineral also is brecciated, but by no means 
to the extent of the arsenopyrite. Still later, quartz 
was introduced into the brecciated sulphides, accom- 
panied by small quantities of serieite, sphalerite, 
galena, and chalcopyrite (pi. 11, B). The introduction 
of silica appears to have continued over a long period, 
and locally it has largely replaced the arsenopyrite, 
the interior of the sulphide fragments apparently 
being particularly susceptible (pi. 11, C). In the U.S. 



OKB DEPOSITS 



103 



mine the introduced quartz is locally continuous with 
a jasperoid alteration product of the sedimentary 
rocks. 

In both the Western Utah and U.S. mines the 
arsenic ore bodies are associated with ore shoots that 
are valuable chiefly for their lead-silver content and 
contain relatively small amounts of arsenic. Such ores 
are characteristically found either along the wall of 
the arsenic ore or, as in the U.S. mine, replacing the 
same limestone bed in which the arsenic ore occurs, 
but beyond the arsenic ore in a direction away from 
the major fracture through which the mineralizing 
solutions are thought to have traveled. Where the 
relations between the two types of ore have not been 
masked by subsequent alterations it is clear that the 
arsenopyrite ore bodies are invariably the older. 

COPPER-LEAD-SILVEE REPLACEMENT BODIES 

Three subclasses of the replacement ore bodies con- 
taining copper, lead, and silver may be distinguished — 
those associated with the arsenic ore bodies, those in 
the Oquirrh formation, and those characterized by 
barite in the gangue. 

The lead-silver replacement bodies associated with 
the arsenic ore bodies are restricted to the occurrences 
of Ochre Mountain limestone in the Western Utah and 
U.S. mines. They have in many places a peripheral 
position with respect to the arsenic ore and are gen- 
erally more distant from the mineralizing fissure. The 
relation of these ore shoots to fractures parallel to the 
bedding is particularly well shown by the "lead 
fissure" on the tunnel level of the U.S. mine. In the 
lowest of the three ore bodies in the Western Utah 
mine, ore of this type away from the mineralizing 
fracture is restricted to a single limestone bed 
and is separated from arsenopyrite that has replaced 
a similar bed by several feet of garnet-diopside 
rock. 

All these ores contain some arsenopyrite. This 
mineral is distinctly older than the other sulphides 
and undoubtedly represents material deposited on the 
fringes of the main arsenopyrite ore bodies. Pyrite 
was the next mineral to form and is locally found 
almost to the exclusion of the other sulphides. It is 
in general rather thoroughly fractured and replaced 
by the later sulphides and quartz. Sphalerite is wide- 
spread throughout the ores and is invariably later than 
pyrite. It contains in many places inclusions of 
chalcopyrite and pyrrhotito in the form of dots and 
discontinuous veinlets. Chalcopyrite may also be 
found in irregular areas of microscopic size bordering 
the sphalerite, but it is for the most part relatively 
rare in these ores. Pyrrhotite in large masses was 
recognized only on the 760- and 900-foot levels of the 
Western Utah mine. On the upper level it was com- 
paratively scarce and appeared to be present only 
adjacent to the mineralizing fracture. On the 900-foot 



level, however, it was wide-spread and had replaced 
pyrite as the most abundant sulphide. This was the 
only place in the quadrangle where there appeared to 
have been a change in the hypogene mineralization 
with increasing depth. 

Galena was the next sulphide mineral to form. 
Locally it contains inclusions of the copper-bismuth- 
lead sulphide, aikinite. Galena is not found in speci- 
mens from the U.S. mine that contain a mineral 
identified by M. N. Short, of the Geological Survey, 
as jamesonite, which, however, has the same relations 
to the other sulphides as galena. The two minerals 
appear to have been mutually exclusive, the formation 
of one or the other seemingly having depended upon 
the local concentration of antimony. Stibnite was also 
recognized in specimens from the dump of the U.S. 
mine. 

The several sulphides are not uniformly distributed 
throughout these ore bodies. Pyrite or pyrrhotite is 
almost invariably by far the most abundant, but the 
proportions of the other sulphides vary widely from 
place to place. In the 234-foot level of the U.S. mine, 
for example, much of the sulphide ore shows a rude 
banding, caused by the separation of the sulphide 
minerals into individual layers. 

Gangue minerals are scarce in these replacement ore 
bodies. Most of them are composed of almost solid 
sulphides with small amounts of interstitial quartz 
and less abundant calcite veinlets. Near the margins 
the replaced limestone also acts as a gangue mineral. 

The factors localizing the ore shoots are the same as 
those that have been described as causing the distri- 
bution of the arsenopyrite ore bodies (p. 102). 

The replacement ore bodies in the Oquirrh forma- 
tion are more numerous than thope of the preceding 
subclass, but are much less extensive. They are found 
in the limestone beds of the Oquirrh formation both 
near to the quartz monzonite contact, as at the 
Monocco and Silver King prospects, and at some 
distance from the contact, as on the Walla Walla 
and Mohawk claims. 

These ore bodies occur in thin beds of limestone 
which are rather free from impurities and which are 
interbedded with sandstone and siliceous limestone. 
Mineralization extends outward into these beds, which, 
wherever these deposits are found, have dips less than 
30°, from steeply dipping fractures that are themselves 
mineralized. The dimensions of such ore shoots are 
small, ore being rarely found more than 15 or 20 feet 
away from the mineralizing fracture, and at such 
distances it is not uncommon for only a portion of the 
favorable bed to be ore-bearing. The mineralizing 
fissure itself locally contains as much as 2 feet of ore, 
but the average thickness is less than 1 foot. In several 
places more than one favorable limestone bed is cut 
by a single fissure, and in that case all the limestones 
may be mineralized. 



104 



GOLD HILL MINING DISTRICT, UTAH 



None of the prospects on deposits of this subclass 
have had sufficient work done to disclose the charac- 
teristics of the unoxidized ore. The oxidized ore in the 
fissures is almost invariably higher in copper and 
lower in lead than the ore from the replaced limestone 
beds, and it seems certain that this difference repre- 
sents an original distinction. Small quantities of 
galena and chalcopyrite have been recognized in these 
ores and are the only remnants of the original intro- 
duction of sulphides. Analyses of the ore shipped to 
smelters show also small quantities of zinc, arsenic, 
and antimony, and it is probable that sulphides of 
these metals were also present originally. The gangue 
of the ore in addition to the replaced limestone consists 
of fine-grained quartz and iron oxides. 

The third subclass of the eopper-lead-silver replace- 
ment ore bodies is represented by the deposit at the 
Garrison Monster mine. Similar deposits occur at 
several nearby localities on the north side of Dutch 
Mountain. These ore bodies lie chiefly along minor 
reverse faults that generally dip at low angles and are 
essentially parallel to the major thrust faults that are 
so abundant in that region. The deposits occur 
exclusively in limestone or dolomite, but individual 
beds of this composition have had no apparent influ- 
ence on the localization of the ore bodies. Ore shoots 
are distributed sporadically along the fissures. They 
are relatively small in lateral extent, none of them 
having a strike length of more than 50 feet, but in the 
Garrison Monster mine, at least, they persist for con- 
siderable distances down the dip. In that mine, the 
ore shoots coincide with troughs in the fissure zone. 

Unoxidized ore is found only in the Garrison Mon- 
ster mine on the tunnel level. There it consists of 
relatively small amounts of pyrite and sphalerite as 
residual remnants in galena. Like most of the sphal- 
erite found elsewhere in the district, this mineral con- 
tains microscopic rounded inclusions of chalcopyrite. 
Associated with the galena in some places, particularly 
near the borders of galena crystals, are small areas of 
an antimonial tennantite. In addition to the limestone 
or dolomite wall rock, the gangue contains small 
amounts of fine-grained quartz and considerable quan- 
tities of barite. The barite appears to be in large 
part later than the sulphides (pi. 11, D). 

SOTEBFICIAI ALTERATION OF THE OSES 

The fact that many ore deposits in unglaciated 
regions have been extensively altered at the surface 
is generally recognized. This alteration is the result 
of the reaction of oxygen-charged surface waters upon 
the suphide minerals in the ore body, producing, near 
the surface, minerals characterized by a relatively high 
oxygen and low sulphur content, and locally, at greater 
depths, concentrations of redeposited or "secondary" 
sulphides. In many places such concentrations of 
redeposited sulphides are of considerable value, and 



much has been written concerning the mechanism and 
results of the process. 88 

Several factors influence the character and extent of 
the alteration. Among these are the position of the 
ground-water table, the rate at which erosion of the 
region is progressing, the past climatic history, the 
recency of any differential uplift, and the physical 
character and mineral composition of the ores and their 
walls. The greater number of the ore bodies in the 
Gold Hill quadrangle have not been sufficiently devel- 
oped to determine adequately the true importance of 
these factors, but from the evidence available it would 
appear that the last one has been the most influential. 
In none of the ore bodies so far developed has there 
been any significant amount of enrichment through the 
formation of secondary sulphides. 

RELATION OF THE WATER TABLE TO SUPERFICIAL 

ALTERATION 

Only four mines in the district have, so far as known, 
reached the ground-water table. These are the West- 
ern Utah mine at the 760-foot level, equivalent to an 
altitude of about 5,125 feet; the U.S. mine at the 234- 
foot level, altitude about 5,430 feet; and the Success 
and Cyclone mines, in whose shafts the water table 
stands at altitudes of 5,450 and 5,950 feet, respectively. 
The Climax shaft was filled with water at the time of 
examination, but it is not known whether this water 
represents ground water or simply filling of mine open- 
ings in relatively impermeable rock. The altitude of 
the water table thus varies considerably in the places 
where it has been determined, and these localities 
also show a comparable variation in the distance from 
the water table to the surface. The data seem to 
indicate, however, that the water surface not only 
has a higher absolute altitude but is nearer the exist- 
ing surface in regions where the old erosion surface, 
discussed on page 61, shows a maximum amount of 
dissection. 

In all four of these mines the bottom of essentially 
complete oxidation is higher than the surface of the 
present water table. In the Western Utah and U.S. 
mines the distance betweeen the two is about 100 
feet, in the Cyclone mine from 30 to 35 feet, and in the 
Success mine 20 feet. Oxidation, however, may extend 
down to the ground-water level along fractured zones. 
The somewhat abrupt transition between rather com- 
pletely oxidized ore and relatively unaltered sulphides 
some distance above the present water table points 
definitely to a recent wide-spread lowering of the 
ground-water level. The relation that appears to exist 
between the level and the old erosion surface suggests 
that such a lowering is the result of the normal faulting 
that is thought to have deformed the old surface. 
(See pp. 61-63.) 



'« Emmons, W. H., The enrichment of ore deposits: TT.S. Geol. Survey Bull. 625, 
1917. Locke, Augustus, Leached outcrops as guides to copper ore, Baltimore, 1926. 



U.S. GEOLOGICAL SURVEY 



PROFESSIONAL PAPER 177 PLATE 10 




~*''Sf -. -."' . , 






A. REPLACEMENT OF SPECULARITE (s) BY DANBURITE (d) AND FLUORTTE (f), GOLD BOND CLAIM. 

B. REPLACEMENT OF TOURMALINE (t) BY SPECULARITE (s), GOLD BOND CLAIM (q, quartz). 

C. QUARTZ CARBONATE VEIN, 7.00(1 FEET EAST OF CLIFTON. 

I). QUARTZ (q) AND ORTHOCLASE (o) REPLACING CALCITE (c), WILSON CONSOLIDATED MINE (plain light). 

POLISHED SECTION SHOWING ARSENOPYRITE FRAGMENTS CEMENTED BY QUARTZ AND OTHER SULPHIDES, CYCLONE MINE. 



U.S. GBOLOOICAL St'KVEY 



PROFBSSIONAL PAPER 177 PLATE 11 




A. BLADED ARSENOPYRITE. TUNNEL LEVEL, U.S. MINE. 

B, POLISHED SECTION SHOWING BRECCIATED ARSENOPYRITE (FcAsS), VEINED BY PYRITE (py), QUARTZ (q), SPHALERITE (a), AND GALENA (g), U.S. MINE. 

C. POLISHED SECTION SHOWING REPLACEMENT OF ARSENOPYRITE FRAGMENTS BY QUARTZ AND SEHICITE, WESTERN UTAH MINE. 

D. THIN SECTION SHOWING BARITE (b) REPLACING SULPHIDES (s), GARRISON MONSTER MINE (plain light; I, limestone). 



0.8. GEOLOGICAL SURVEY 



PROFESSIONAL PAPER 177 PLATE 12 






A. DENSE WHITE SCORODITE WITH ASSOCIATED CRYSTALLINE GREEN SCORODITE, WESTERN UTAH MINE. 

B. BROWN SCORODITE, WESTERN UTAH MINE. 

C. CRYSTALLINE SCORODITE FORMING FROM METACOLLOID. 

Plain light. 



ORB DEPOSITS 



105 



RELATION OF THE PHYSICAL AND CHEMICAL CHARACTER 
OF THE ORES TO SUPERFICIAL ALTERATION 

Alteration of the pipelike deposits and of veins with 
silicate minerals in the gangue. — The pipelike deposits 
and the greater number of the veins with silicate 
minerals in the gangue are alike in being relatively 
little affected by oxidation. This condition arises in 
part because the silicate minerals are resistant to altera- 
tion, in part because the low content of sulphides pre- 
vents the formation of much sulphuric acid, and in part 
because the toughness and compact texture of the indi- 
vidual minerals do not permit the formation of cracks 
and fissures through which surface waters may percolate 
and react with the ore minerals. In many places in 
these ores hypogene sulphide minerals are found at or 
near the surface, essentially unaltered. Even in spec- 
imens that show some alteration it is generally found 
that the core of the mineral grain has not been affected. 
The changes that have been noted in these deposits 
are the local alteration of scheeHte to cuprotungstite, 20 
molybdenite to powellite, pyrite to iron oxides, and 
chalcopyrite to copper pitch which in turn is veined by 
copper carbonates and chrysocolla. These minerals 
are locally accompanied by supergene silica in the 
form either of chalcedony or of opal. The general 
occurrence of copper pitch in place of the usual oxida- 
tion products of chalcopyrite may be explained by the 
scarcity of pyrite and a consequent deficit in the 
amount of sulphuric acid available during the altera- 
tion. In ores like those found on the Copper Bloom 
group of claims, in which the ratio of quartz and sul- 
phides to silicate minerals is higher, the secondary 
copper sulphides covellite and chalcocite have replaced 
chalcopyrite. This feature appears to be explained 
chiefly by the greater abundance of pyrite but is prob- 
ably also accented by the greater mobility of solutions 
in the more readily fractured quartz. The hypogene 
bismuth sulphide, bismuthinite, was recognized only 
in ores containing small quantities of silicate minerals 
in the gangue. It was everywhere pseudomorphously 
altered to a mineral of varying appearance and optical 
properties that is probably close to bismutite in com- 
position, A small piece of native bismuth was found in 
an area of the supposed bismutite, which in turn was 
thought to be pseudomorphous after bismuthinite. 

Alteration of the quartz-sulphide veins. — Of the veins 
with a quartz gangue, those containing mixed sulphides 
are almost completely altered at the surface. Galena 
is the only sulphide that has been found near the sur- 
face in these deposits, and it is generally surrounded 
by rims of varying thickness of anglesite and cerusite. 
The stable lead mineral in the oxidized zone, however, 
is plumbojarosite, and this mineral probably contains 
the bulk of the lead in the ore shipped from the oxidized 
parts of these veins. Much of it is arsenical and 



»« Hess, F. L., unpublished notes. 
35311-35 8 



1 approaches beudantite in composition owing to the 
general occurrence of arsenopyrite in the ores. Jaro- 
site, also arsenical, is likewise widely distributed. The 
oxidized ore also contains some zinc, probably in the 
form of calamine, and copper, chiefly as the basic 
carbonates and chrysocolla. Small quantities of des- 
cloizite, mimetite, and wulfenite are also present. The 
Cyclone mine was the only one in which the contact 
between the oxidized and unoxidized ore could be 
examined, and here there was no evidence of any 
appreciable accumulation of secondary sulphides at 
the contact. The copper content of the unoxidized 
ore is low in this mine, ranging from 0.5 to 1.7 percent, 
and is apparently balanced by a sufficient quantity of 
carbonate in the vein to prevent any downward trans- 
portation of copper. There is certainly no accumula- 
tion of secondary copper sulphides at the present 
water table in this mine. 

Quartz veins containing arsenopyrite as the metallic 
mineral are not so thoroughly oxidized at the surface. 
Scorodite is widely distributed throughout these veins, 
and all stages in its replacement of arsenopyrite may 
be recognized, but the alteration is far from complete. 
This in part at least appears to be the result of the 
massive character of the sulphide, in which relatively 
few cracks unhealed by quartz may be distinguished. 
The quartz veins containing tetrahedrite and galena 
are still less altered. The sulphide content of these 
veins is extremely small, and pyrite is totally absent. 

Alteration of the carbonate and sulphate veins. — The 
carbonate veins are affected by weathering chiefly in 
the elimination of carbon dioxide from the iron-rich 
carbonates at the surface. Most of these veins on 
weathered surfaces are colored various shades of brown 
by the residual iron oxides. The barite veins are 
essentially unaltered. 

Alteration of the arsenic replacement bodies. — The ar- 
senic replacement bodies in limestone provide the most 
spectacular results of superficial alteration. The out- 
crop at the Western Utah mine consists of the hydrated 
iron arsenate, scorodite, with some intermixed iron 
oxides, and originally had a length of about 300 feet 
and a width of nearly 200 feet. The ore shoot repre- 
sented by this outcrop and the next lower one are 
both completely altered, and the third and lowest ore 
shoot is similarly affected for most of its developed 
extent. The upper portion of the ore shoot at the 
U.S. mine has also been converted to scorodite. 

The scorodite varies considerably in appearance and 
texture. The greater part of it is a fine-grained dense 
brownish to greenish-brown rock with a conchoidal 
fracture in which are sporadic vugs lined with finely 
crystalline material (pi. 12, B). In several places, 
however, there are considerable amounts of white mate- 
rial, which also has a conchoidal fracture. With this 
locally is associated crystalline green scorodite (pi, 12, 
A). Thin sections show the relations of these differ- 



106 



GOLD HILL MINING DISTRICT, UTAH 



ent kinds of material to one another. The dense white 
material, in which remnants of arsenopyrite may lo- 
cally be distinguished, is a metacolloidal substance 
which has a streaked or collofonn habit and which 
is in part isotropic and in part has a fibrous crystal- 
lization. The refractive indices and birefringence of 
the nonisotropic portion are both somewhat lower 
than those of scorodite. • In sharp contrast with 
the white metacolloid is fine-grained crystalline green 
scorodite. The textures shown by the metacolloid do 
not pass across the contact into the true scorodite, 
and the grain size of the scorodite increases away from 
the contact, reaching a maximum in the terminated 
crystals that line the vugs (pi. 12, O). Several speci- 
mens show that the green scorodite has formed at the 
expense of the metacolloid, and in a few places, as 
on the 150-foot level of the Western Utah mine, it 
has almost completely displaced the metacolloidal 
material. 

Similar stages may be observed in the brown to 
greenish-brown ore, but in this there are abundant 
microscopic flakes of iron oxide that impose their 
color upon the material. If the oxidation of arseno- 
pyrite to scorodite, neglecting intermediate steps, is 
considered as represented by the equation 

FeAsS + 70 + 3H 2 = FeAs0 4 .2H 2 + H 2 S0 4 

it is clear that there is no excess iron to form the iron 
oxide observed in the brown ore, and it is necessary to 
assume that sufficient pyrite must have been present 
in the original ore to provide the excess iron. 

Locally the scorodite has been altered to a micaceous 
golden-brown mineral that appears to be arsenosiderite. 
This alteration involves the addition of lime, which is 
probably derived from the limestone wall rocks. 

The white metacolloidal mineral in the specimens 
studied appears to have been developed essentially 
in place, but there is abundant evidence to prove that 
scorodite has formed in the wall rocks at some distance 
from the hypogene sulphides. Veinlets of scorodite 
cutting the silicate minerals in the wall rocks are 
not uncommon. 

Alteration of the copper-lead-silver replacement bodies 
associated with the arsenic replacement bodies. — The 
oxidation of the copper-lead-silver replacement bodies 
associated with the arsenopyrite ore shoots has been 
distinctly influenced by the proximity of the arsenic 
ore. The bulk of such oxidized ore consists of mam- 
miliary, stalactitic, and powdery iron oxides, members 
of the jarosite group, and a varying quantity of scoro- 
dite, depending upon the distance from the arsenic 
ore shoot. The jarosite minerals include both jaro- 
site and plumbojarosite, both of which contain the 
arsenate radicle locally, and in some places qualitative 
tests show that the sulphate radicle has been almost 
completely displaced by the arsenate radicle. 



Together with this aggregation of minerals in the 
upper ore shoot of the Western Utah mine there was 
apparently a considerable amount of copper in the 
form of copper arsenates. The greater part of this ore 
has been stoped, and the relations and identities of the 
copper arsenates are not known. Small amounts of 
conichalcite were recognized in the lower ore bodies in 
the form of mammillary growths upon iron oxide and 
scorodite mixtures. Small quantities of olivenite and 
clinoclasite were also found in specimens studied by 
W. F. Foshag, of the National Museum. Zinc is present 
in the oxidized ores as the arsenate, adamite, which forms 
white prismatic minerals resting upon the iron oxides. 

The lead-bearing minerals in the oxidized portions 
of these deposits are not disseminated through the 
mass but are generally restricted to rather narrow 
lenticular masses. A jarositelike mineral is the only 
one present in any quantity in such lenses, but in 
composition it appears to range from plumbojarosite 
that is nearly free from arsenate to a hydrous arsenate 
of lead and ferric iron that is nearly free from sulphate. 
Doubtless some of this corresponds to the mineral 
beudantite. Small quantities of a white crystalline 
substance found in this material at the surface proved 
to be the lead chloroarsenate, mimetite. 

Associated with both the oxidized arsenic and copper- 
lead ore shoots are considerable quantities of clay 
minerals. In most specimens these are isotropic and 
have a low refringence and are probably halloysite. 
Some, however, are distinctly birefrigent and probably 
belong to the leverrierite group. Locally masses of 
black wad are embedded in the clay. The greater part 
of the clay occurs in the walls of the oxidized ore, but 
some of it is intermixed with both the iron oxides and 
the scorodite. It appears to represent the product of 
the reaction between the silicate minerals in the wall 
rocks and the sulphuric acid set free during alteration. 
Small quantities of opal and quartz are also found with 
the other oxidation products. 

Several additional minerals are present in the West- 
ern Utah and U.S. mines where oxidation has extended 
downward to the present water table. Small quantities 
of secondary sulphides, of which marcasite is the most 
abundant, have developed in these places. Some 
chalcocite was recognized but in insufficient quantities 
to form a copper ore. The most surprising sulphide 
in this group is arsenopyrite, which apparently has 
not been previously recognized as a supergene sulphide. 
The mineral, whose identity was determined by W. 
T. Schaller, was found as a crystalline coating on a 
mixture of scorodite and iron oxides from the 760-foot 
level of the Western Utah mine. In addition to these 
sulphides gypsum is wide-spread at this horizon and 
locally has associated with it small quantities of native 
sulphur. The assemblage of minerals clearly indicates 
that, at this depth, the addition of oxygen that char- 
acterized the processes of alteration nearer the surface 



OEE DEPOSITS 



107 



was no longer operative and was replaced by an 
abstraction of oxygen. 

On the lower levels of the Western Utah mine also, 
though not associated with the secondary sulphides, 
there are considerable quantities of siderite that has 
replaced the limestone wall rocks. In appearance this 
material is not unlike the smithsonite ores of other 
western mining districts, but chemical tests show that 
its zinc content is extremely low. 

Alteration of the replacement bodies in the Oguirrh 
formation. — The replacement bodies in the Oquirrh 
formation are almost completely oxidized. The copper 
ores in the fissures consist dominantly of dark-brown 
to black copper pitch, which contains remnants of 
chalcopyrite and is veined by malachite, azurite, and 
chrysocolla. The lead ores contain sparse remnants of 
galena, from which anglesite, cerusite, and plumbo- 
jarosite have been formed. Several specimens show 
that these minerals were formed in the order named, 
and each one at the expense of the preceding mineral. 
The process of alteration has apparently nearly reached 
completion, for plumbojarosite is the most abundant 
lead mineral in these deposits. In both lead and copper 
deposits secondary silica in the form of opal and chal- 
cedony is present. 

Alteration oj replacement bodies containing- barite. — 
The lead replacement bodies with barite in the gangue 
have also been altered in a similar way. At the 
Garrison Monster mine, however, the proportion of 
cerusite to plumbojarosite is relatively high. 

ABIAI RELATIONS OF THE ORE DEPOSITS 

In many mining districts it has been observed that 
different types of ore deposits are arranged in con- 
centric zones with respect to a central area, which is 
commonly occupied by an intrusive rock mass. The 
deposits of the successive zones are held to represent 
deposition at decreasing temperature away from the 
central area, and the mineralogic changes that are 
observed in them are considered to be the same as 
those found at different depths in a single vein, the 
deeper mineral facies in the vein being represented by 
a similar grouping in the inner zones on the surface. 
Emmons 30 has recently summarized the evidence for 
such a zonal distribution of ore. In view of the large 
number of different kinds of ore bodies occurring in 
the Gold Hill quadrangle, it is desirable to bring out 
in what respects the distribution of these deposits con- 
forms to the ideal arrangement, and in what respects 
and for what reasons it appears to depart from a 
uniform zoning. 

Influence oj zoning on the distribution of the ore 
deposits. — Almost all the ore bodies characterized by 
silicate minerals in the gangue are concentrated in a 



*> Emmons, W. H,, Primary downward changes in ore deposits: Am. Inst. Min. 
Ing. Trans., vol. 70, pp. 964-997, 1924; Relations of metalliferous lode systems to 
igneous intmsiws; Idem, vol. 74, pp. 29-70, 1926; Relations of the disseminated 
copper ores in porphyry to igneous introsives: Idem, vol. 7S, pp. 797-816, 1927. 



relatively narrow zone extending from a point near 
the town of Clifton to the vicinity of the U.S. mine. 
This zone coincides with a belt of normal faulting that 
is considered to be closely related in age to the intru- 
sion of the quartz monzonite, and it has been suggested 
that the belt represents the primary channel through 
which the igneous rock was intruded (pp. 88-89). 
Such a relation between the site of intrusion and the 
higher-temperature ore deposits seems to be good 
evidence that areal zoning has to that extent been 
operative. 

Within this same zone, however, there are numerous 
representatives of other types of deposits, which 
clearly have been formed at lower temperatures. 
Thus on the Eeaper claim, in addition to the tungsten- 
bearing pipe, there is a quartz vein containing tetra- 
hedrite, galena, and barite and a quartz-carbonate 
vein, both less than 300 feet from the pipe. Similarly, 
in the areas outside of the zone, deposits of notably 
different mineralogy are found in close proximity. At 
the Western Utah mine, on Gold Hill, for example, 
a gold-bearing lode with silicate gangue, a quartz- 
tetrahedrite vein, and arsenic and lead-zinc replace- 
ment bodies in limestone are essentially in contact 
with one another. 

There must therefore be some other factor than 
distance from the center of intrusion that has influ- 
enced the distribution of the ore deposits. It seems 
probable that this factor lies in the age relations 
between the mineralogic facies characterizing the 
different types of ore deposits. As has been noted, 
there is a demonstrable sequence for the several facies, 
the higher-temperature deposits being the oldest. The 
writer believes that to these differences in age is due 
the lack of zoning shown by the greater number of the 
deposits, and that in this district the time factor 
(resultant from such age differences) has been vastly 
more important in determining the distribution of ore 
bodies than the space or temperature factor that 
causes the zonal distribution. It is not improbable 
that the dominance of the time factor in this area is 
in large part the result of the repeated fracturing 
of the quartz monzonite (p. 89), which provided 
channels for the ore-depositing solutions in regions 
that might otherwise have been closed to them through 
sealing of the earlier-formed fractures by older, higher- 
temperature ore bodies. 

It is obvious that if the time factor is as important 
as is thought, the period during which .ore deposition 
took place must have been a long one, because it 
must have included time enough for the ore-bearing 
solutions traveling through the same stretch of quartz 
monzonite country rock to cool from the temperatures 
at which the tungsten-bearing pipes were deposited to 
those which permitted the carbonate veins to form. 

The proposed relation between the recurrent frac- 
turing in the quartz monzonite and the lack of a general 
zoning pattern in the distribution of the ore deposits 



108 



GOLD HILL MINING DISTBICT, UTAH 



would imply that regions in which a zonal distribution 
of the ores is well denned have undergone essentially 
no fracturing during the period of ore deposition. 

Both Hills 31 and Knopf 82 have described districts 
in which the distribution of the ore deposits is markedly 
at variance with that to be expected if there had been 
a simple zonal control. Both men came to closely 
similar conclusions, which may be summarized by the 
following quotation from Knopf: 

The principle that successive ore-forming differentiates 
("distillates"), each with its own distinctive constituents and 
characteristics, are given off during successive stages of a pro- 
gressively cooling magma will be found, it is here suggested, to 
be widely applicable in the study of ore deposition. As a modi- 
fying factor the principle of zonal distribution is recognized as 
having been operative in some districts, but of and by itself 
the principle of zonal variation in ore deposition is of very 
narrow application. 

The writer prefers the view that recurrent fracturing 
in the intrusive rock is of more importance in changing 
the character of the ore bodies than distinctive com- 
position of successive differentiates. The evidence for 
this opinion is given in the section on the origin of 
the ores. 

Influence of the Ochre Mountain thrust on the distri- 
bution of the ore deposits. — A singular feature in the 
distribution of the ore deposits is the barrenness of the 
formations above the Ochre Mountain thrust. In 
several places roof pendants within the quartz monzo- 
nite or reentrants of sediments into the intrusive rock 
are made up largely of Ochre Mountain limestone 
lying above the thrust, with only small amounts of the 
overridden beds beneath. The beds below the thrust 
are intensely metamorphosed and contain various 
kinds of ore bodies, but the overlying beds are essen- 
tially unaltered and in almost all places contain no 
ore bodies whatever. This difference in behavior can- 
not be attributed to any lithologic features of the 
overlying beds, because the occurrences of Ochre 
Mountain limestone beneath the thrust contain numer- 
ous and locally large ore bodies. It seems probable 
that the barrenness of the rocks above the thrust may 
be attributed to the fact that the thrust plane pre- 
vented the continuation upward of fractures that were 
forming in the quartz monzonite and in the rocks 
below the thrust and localized the flow of the solutions 
that were causing metamorphism and ore deposition. 
As almost all these fractures appear to be genetically 
connected with the intrusive rock, it is likely that the 
zone of weakness represented by the thrust would 
deflect the fractures horizontally along itself and 
prevent their further upward extension. 



« Hills, Loftus, The zinc-lead sulphide deposits oJ the Bead-Bosebury district: 
Tasmania Oeol. Surrey Bull. 28, pp. 86-88, 1915. 

»" Knopf, Adolph, Geology and ore deposits of the Bochester district, Nev.: U.S. 
Gaol. Survey Bull. 782, pp. 57-68, 1924. 



GENESIS OF THE OBE DEPOSITS 

The ore deposits within the quadrangle very clearly 
represent the final stages of the intrusion of the quartz 
monzonite stock. The evidence proving the close 
relationship between them lies in the obvious con- 
nection between metamorphism and the ore deposits — 
particularly the pipes and the veins with silicate 
gangue — and the dependence of the metamorphism in 
turn upon the quartz monzonite intrusion. The 
exposures within the quadrangle appear to provide a 
rather complete picture of the ever-changing results 
effected by the emanations given off by the solidifying 
intrusive. 

At the start of this final stage of the igneous activity 
the emanations resulted in the formation of anhydrous 
silicate minerals with, locally, tungstates in the form 
of scheelite. The minerals formed show that all the 
common rock-forming elements were contained in the 
emanations and, as they developed by the replacement 
of either the wall rocks or the quartz monzonite, lead 
to the view that the material was simply a residuum 
of the rock magma made highly mobile by the con- 
centration within it of the small quantities of volatile 
constituents originally contained in the magma. These 
constituents do not enter into the earlier-formed 
minerals, however, either because their concentration 
was not large enough to cause precipitation, or, more 
probably, because the temperature was too high to 
permit them to enter a stable solid phase. 

This assemblage of minerals was succeeded by one 
in which the minerals formed are made up not only of 
the rock-forming elements but also of the volatile 
constituents. Amphiboles, tourmaline, axinite, apa- 
tite, scapolite, fluorite, humite, and danburite, for 
example, were formed during this period, in many 
places at the expense of the minerals of the first stage. 
In addition, iron oxides appear to have been formed 
at this time. 

The initiation of a third period is marked by the 
appearance of quartz and the metallic sulphides. 
Chlorite and sericite are essentially contemporaneous 
with these minerals and show that the emanations 
still contained some of the rock-forming elements, 
even though many occurrences of these minerals sug- 
gest that in large part they have developed at the 
expense of earlier-formed silicate minerals. This 
period, like both of the preceding ones, may be sub- 
divided into successive steps. Thus, bismuthinite 
and arsenopyrite appear to have been among the 
earliest sulphides to form. Galena and tetrahedrite, 
on the other hand, are among the last and appear to 
have been deposited near the end of the period. 

The products of the final period are characterized 
by the almost complete absence of silicate minerals 
and metallic sulphides. During this period the emana- 



OBE DEPOSITS 



109 



tions deposited silica (much of it probably in the form 
of a gelatinous substance that later recrystallized to 
quartz), barite, and carbonates. The carbonate min- 
erals contain considerable quantities of iron and mag- 
nesium and indicate the persistence of these rock- 
forming elements as constituents of the igneous 
emanations. 

Although the assemblages of these four periods are 
distinct mmeralogically, they are by no means sep- 
arated areally; in many places all four may be found 
in the same ore deposit, where they are intimately 
associated but clearly of different ages. This fact, 
together with the persistence of certain of the con- 
stituents, such as iron, magnesia, and silica, throughout 
the series, makes it highly improbable that there have 
been several emissions of distinctive composition from 
the magma, as postulated by Knopf and Hills (see 
p. 108), but indicates rather that metamorphism 
and ore deposition have been one continuous process. 
The abrupt changes in mineralogy shown by the 
deposits of the four periods appear to have been the 
result of a constantly decreasing temperature, by 
which new mineral groups became the stable phase in 
place of the older minerals that they replaced. This 
view requires that the different elements contained in 
the emanations should have widely different fields of 
stability. Thus, fluorine and boron could have been 
precipitated during only one of the four periods, but 
magnesium, iron, and silicon appear to have formed 
stable compounds throughout the process, although 
it is recognized that the compounds formed differ for 
each period. 

Although it is probable that all cooling igneous 
emanations in general pass through successive periods 
more or less similar to those recognized at Gold Hill, 
it is obvious that the details of the process must differ 
considerably in different places. The individual 
minerals formed reflect not only the original compo- 
sition of the emanations but also changing concentra- 
tions of the different phases contained in them, the 
rate of change in temperature, reaction with the wall 
rocks^ and the presence or lack of equilibrium. The 
important feature, it would seem, is that the fluids 
that cause igneous metamorphism and ore deposition 
undergo a differentiation of the same or even a greater 
degree of complexity than that which has been deter- 
mined for the igneous rocks themselves. 

The chief modifying factor in the progress of ore 
deposition appears to have been the presence of re- 
current fracturing in the rocks within which the ores 
were being deposited. The evidence indicating that 
fracturing continued over a long period after the 
intrusion of the quartz monzonite is presented on 
page 89, and to this cause may be attributed many 
of the present features of the ore deposits found in 
the quadrangle. This factor can be used to explain 
the preservation of the pipelike deposits through the 



abandonment of the mineralizing channel by reason of 
renewed fracturing; had this not occurred, the mineral 
assemblages of the early periods would probably have 
been in large part replaced by those of the later periods. 
On the other hand, a channel once sealed by deposition 
of material from the emanations may be reopened and 
again filled by minerals of a much later period, as 
illustrated by the late carbonate veins that cut ore 
deposits of an earlier stage. 

It is possible that the existence of so many small ore 
deposits instead of a smaller number of large deposits 
is to be ascribed to recurrent fracturing. As renewal 
of fracturing may have caused the abandonment of old 
channels and the opening of new ones, it would appear 
that the process, if carried far enough, might easily 
result in so shortening the time during which ore 
deposition was operative at any one place that the 
bodies of ore thus formed would be so small and of so 
low a grade as to be of relatively little value. 

FUTURE OF THE DISTRICT 

At the time of the last field work by the writer 
(1927) the production of the district had decreased 
to a small part of that made in the years after the com- 
pletion of the railroad from Wendover. The reasons 
for this decrease were in part economic and in part 
inherent in the ore deposits themselves, but the two 
reasons were of different importance for each class of 
ore body. The future possibilities of the district may 
therefore be most readily discussed by a separate 
consideration of each type of deposit. 

Tungsten-bearing pipes and veins, — The production 
of tungsten from pipes and veins has been small and 
was made only during the war-time period of high 
prices. Although it is probable that similar deposits 
might be developed in the region between Clifton and 
the Lucy L mine — particularly at the upper contact 
of the quartz monzonite stock beneath the roof pend- 
ants that conceal much of the igneous rock in this 
region — it is doubtful if such deposits could be worked 
profitably at the prevailing prices for tungsten. 

Veins with silicate minerals in the gangue. — Two 
main varieties of the veins having silicate minerals 
in the gangue have been prospected: in one, copper 
is the valuable metal ; in the other, gold. The copper- 
bearing veins have been rather thoroughly prospected 
on the Frankie, Calaveras, Pole Star, and other claims, 
and several shipments of ore have been made from 
them. In general, however, the average copper con- 
tent is too low and the ore bodies developed are too 
small for them to be worked profitably except when 
prices for copper are unusually high, and owing to the 
nearly complete extraction of these ores at the outcrop, 
where mining has been relatively cheap, it is doubt- 
ful if they will ever be of any importance, 

A different conclusion may be drawn concerning the 
veins in which gold is the valuable constituent. At 



110 



GOLD HILL MINING DISTRICT, UTAH 



least four mines have worked ore deposits of this 
type — the Rube, Alvarado, Midas, and Cane Springs — 
and these have shown that the ore shoots, though small, 
contain sufficient gold to make properly conducted 
operations successful. The known deposits have a 
rather wide distribution in the sedimentary rocks near 
the quartz monzonite contact, but the outcrops of 
the ore deposits are relatively inconspicuous. It seems 
probable that careful prospecting in the sediments near 
the igneous contact may disclose other deposits of 
this class which contain either direct smelting ore simi- 
lar to that at the Rube, or lower-grade milling ore. 
The tonnage of milling ore in a single one of these 
veins would probably be insufficient to warrant the 
erection of a mill, but it is probable that ore from sev- 
eral of them would justify the operation of one mill. 

Quartz-sulphide veins. — A large number of the 
quartz-sulphide veins have been prospected more or 
less thoroughly and have furnished some small ship- 
ments of ore, valuable chiefly for the content of silver 
and lead. The work that has been done has shown 
rather conclusively that the ore shoots are too small 
for any operations except on the most modest scale, 
and future production from deposits of this type will 
very probably be confined to occasional carload lots 
extracted by lessees. 

Carbonate-sulphate veins. — The carbonate veins have 
essentially no valuable metallic constituents and need 
not be further considered. If the demand for barite 
continues to increase, however, there is a possibility 
that deposits large enough to warrant mining opera- 
tions may be developed. So little work has been done 
on the deposits containing barite, however, that it is 
difficult to predict their future importance. 

Arsenic replacement bodies. — The two important 
arsenic replacement bodies — in the Western Utah and 
U.S. mines — have, with the lead-silver replacement 
bodies associated with them, provided a large part of 
the district's production. The shipments "of arsenic 
ore from the two mines were made during the period 
from 1919 to 1925, when prices of white arsenic (As 2 O s ) 
ranged from 7 to 20 cents a pound. Both mines still 
possess large reserves of arsenic ore, but the prevailing 
prices of 2 to 4 cents a pound for white arsenic since 
about 1925 have been too low to permit profitable 
operations. Should prices improve sufficiently, these 
mines would undoubtedly be able to provide a large 
quantity of ore. According to Clifford F. Rowley, 
manager, the Western Utah mine has 225,000 tons of 
proved ore, averaging 24 percent of arsenic. The 
quantity of arsenic ore developed in the U.S. mine was 
not ascertained but must be of about the same magni- 
tude. Only a minor amount of exploration has been 
directed toward the development of new arsenic ore 
bodies, but it seems probable that, if due regard is 
given to the factors which were operative in localizing 
the two known deposits, additional ore bodies may be 



found in regions where the Ochre Mountain limestone 
beneath the Ochre Mountain thrust is adjacent to 
the quartz monzonite. 

Copper-lead-silver replacement bodies, — The remarks 
made above concerning the quartz-sulphide veins are 
applicable also to the copper-lead-silver replacement 
bodies, for, except for the lead-silver ore associated 
with the arsenic ore deposits, the exploitation of these 
ore bodies has been, in general, disappointing. Some 
of the deposits, particularly those in the Garrison 
Monster mine, contain rather rich ore, but the ore 
shoots without exception are so small in cross section 
that the quantity of ore available is meager. 

Summary. — A large tonnage of arsenic ore is devel- 
oped in the quadrangle, and the possibilities of- in- 
creasing the amount are thought to be good. Profit- 
able exploitation of the ore, however, must wait until 
the price of arsenic is higher than that which has 
prevailed in recent years. It is also considered that 
careful prospecting may disclose additional deposits of 
gold ore which, though of small size, may repay the 
discoverer. Possibly the district contains barite 
deposits that may be worked at a profit if the demand 
for this material increases. The remaining types of 
deposits are thought to be too small or too low in 
grade to provide any great future production. Many 
of these deposits, however, offer opportunities to 
small groups of individuals who, working with little or 
no overhead expense, might extract several carloads of 
ore at a satisfactory profit. 

MINERALS OF THE METAMORPHOSED ROCKS AND 
THE ORE DEPOSITS 

In this section the minerals are described in the 
order followed by Dana. 

NATIVE ELEMENTS 

Graphite (C). — Pound as small flakes in the altered limestone 
wall rock in the Alvarado mine, associated with museovite, 
quartz, calcite, and spadaite (?). Opal and a clay mineral are 
also present, but are probably supergene. 

Sulphur (S). — Small quantities of native sulphur were recog- 
nized in the Western Utah mine at ground- water level. Mar- 
casite, gypsum, and iron oxides were the most abundant 
associated minerals. 

Bismuth (Bi). — Small quantities of bismuth were found at 
the Wilson Consolidated and Lucy L mines. In the former a 
speck of native bismuth was embedded in bismuthinite; in, the 
latter it was associated with bismutite. 

Gold (Au). — Native gold is present in a number of the mines 
in the district, particularly those in which the gangue consists 
of silicate minerals. Previous observers have considered the 
gold to be contemporaneous with the silicate minerals, but the 
writer's observations indicate that it was introduced somewhat 
later and is more closely associated with quartz and sericite. 
Two varieties of gold were recognized in specimens from the 
Rube mine. One was in the form of microscopic specks widely 
distributed throughout the unoxidized ore. The other was 
coarser-grained and in the form of well-developed crystals and 
was observed in anglesite, cerasite, and other supergene minerals 
and also resting upon iron oxides. The second variety was 



MIN1EALS OF THE METAMOKPHOSED ROCKS AND THE OBE DEPOSITS 



111 



clearly formed during the oxidation of the ore. There was, 
however, no apparent enrichment during the oxidation, for the 
unoxidized ore has essentially the same content of gold as the 
oxidized ore. 

Copper (Cu). — Mr. Tiffany, superintendent of the Western 
Utah mine in 1925, reported that some native copper had been 
found on the 760-foot level. 

SULPHIDES, SELBNIDES, TELLTJBIDE8, ARSENIDES, AND 
ANTIMONIDES 

Realgar (AsS). — Small quantities of realgar are reported to 
have occurred in the Western Utah mine, but it was not observed 
by the writer. The almost complete absence of realgar and 
orpiment from the ores of the district is rather surprising, in 
view of the abundance of arsenopyrite and the fact that the two 
iron-free arsenic sulphides are generaEy considered to be super- 
gene alteration products. 

Orpiment (As 2 83). — Also said to have been found in small 
amounts in the Western Utah mine. 

Stibnite (SbSi) .- — Stibnite is locally abundant on the 234-foot 
level of the U.S. mine. In one specimen, in which it was identi- 
fied by W. T. Schaller, bladed crystals more than 1 inch long 
were associated with pyrite. 

Bismuthinite (Bi 2 S 2 ). — This hypogene bismuth sulphide was 
found in the ores from the Lucy L and Wilson Consolidated 
mines, as rounded blebs in both quartz and calcite. It is 
generally either partly or completely replaced by bismutite, 
which retains the pronounced cleavage of the older mineral. 

Molybdenite (MoS 2 ).' — Molybdenite is present to many of the 
ore deposits containing silicate minerals in the gangue and was 
also noted disseminated through altered quartz monzonite in 
the vicinity of the Eeaper claim. It appears to have formed 
earlier than most of the other sulphides, for it is embayed and 
replaced by chlorite in specimens from the Rube mine. In this 
mine it is extremely abundant in one portion of the ore shoot. 
Because of its presence in several of the gold ore bodies the 
mineral is thought by some to be gold-bearing. This, however, 
is not borne out by an assay made by E. T. Erickson, of the 
Geological Survey, of a specimen containing 61.6 percent of 
MoS 2 , in which the gold content was 0.26 ounce to the ton — 
much less than is found in the shipping ore. A second assay 
was made of material containing less molybdenite, which may 
be compared with the first as follows: 



MoSi 
(percent) 


Asll Gold 

o )oreent >|p < &toS 


20.4 
81. § 


79.6 0.52 
38.4 .28 



The gold content is thus almost exactly proportional to the 
ash content and bears no relation to the molybdenite content 
whatever. 

Galena (PbS). — Galena is found in almost all the quartz- 
sulphide veins and limestone replacement bodies and is sparingly 
present in some of the veins with silicate minerals in the gangue. 
It has clearly formed later than arsenopyrite, pyrite, and sphal- 
erite, but its relations to chalcopyrite are obscure, as in some 
places it appears to be later and in others to be veined by chal- 
copyrite. In several places it contains tiny inclusions of aikinite 
and tetrahedrite or tennanite. In specimens from the Garrison 
Monster mine it is replaced by barite (pi. 11, D). Alteration to 
anglesite, cerusite, and plumbojarosite has been wide-spread. 

Chalcocite (Cu 2 S) . — Small quantities of chalcocite were found 
in several places as supergene replacements of the hypogene 
sulphides. 

Sphalerite (ZnS). — The distribution of sphalerite is similar 
to that of galena. It was noted in quartz-tourmaline rock at 
the Gold Bond claim and is moderately abundant in the quartz- 



sulphide veins and in the limestone replacement deposits. It 
replaces arsenopyrite and pyrite and is generally replaced by 
quartz and the other sulphides. Tiny rounded inclusions of 
chalcopyrite and pyrrhotite are present in most of the speci- 
mens. In several of the mines sphalerite occurs in masses 1 
inch or more across and has a nonmetallic appearance. The 
color is dark brown to black, and the cleavage is well marked. 
A thin section from the footwall of the Rube vein contained 
some dark sphalerite embedded in dolomite. Several quartz 
veinlets cut the section and in one place a veinlet impinges 
upon the sphalerite. Adjacent to the quartz the dark sulphide 
has been bleached to a colorless sphalerite whose index of 
refraction is slightly lower than that of the older darker 
sphalerite. 

Covellite (CuS). — Covellite was recognized in a few specimens 
as a supergene alteration product of the hypogene sulphides, 
chalcopyrite, galena, and tetrahedrite. 

Pyrrhotite (FeSi+). — Pyrrhotite is abundant only on the 900- 
foot level of the Western Utah mine, where it appears to have 
taken the place of the pyrite that is found on the upper levels. 
It was also noted as inclusions in sphalerite in specimens from 
other mines. 

Bornite (CusFeS 4 ). — Bornite was noted in small quantities in 
ores from the Alvarado, Midas, and Cane Springs mines. 

Chalcopyrite (OuFeS 2 ). — Chalcopyrite is found in small 
amounts in all the different types of ore deposits except the 
carbonate and sulphate veins. It occurs both interstitial to 
other sulphides and silicate minerals and as tiny rounded 
inclusions in sphalerite. Much of it has been altered to copper 
pitch, in which remnants of the sulphide are generally abundant. 

Pyrite (FeS 2 ), — Pyrite is found both in many of the ore 
deposits and disseminated through the altered quartz monzonite. 
It was one of the earliest sulphides to form in the ore deposits. 
It is probably later than molybdenite and has definitely replaced 
arsenopyrite but has been replaced by all the other sulphides. 

Marcasite (FeS 2 ). — Marcasite was noted in several specimens 
from the Western Utah mine that were collected at about the 
present ground-water level. It has replaced pyrite, from which 
it may be readily distinguished in polished specimens by reason 
of its anisotropism in polarized light. 

Arsenopyrite (FeAsS). — Arsenopyrite occurs in very large 
quantities in the ores of the district, both in the quartz-sulphide 
veins and in the limestone replacement bodies, locally being 
present to the almost complete exclusion of the other sulphides. 
The arsenopyrite masses in the Western Utah and U.S. mines 
are probably the largest bodies of this mineral that have thus 
far been discovered. Where arsenopyrite has replaced lime- 
stone it appears to have formed originally as bladed radiating 
crystals (see pi. 11, A), but in most of the occurrences this 
habit has been destroyed by later fracturing and subsequent 
cementation and replacement by quartz, sericite, pyrite, and 
other sulphides. The arsenopyrite has been altered in many 
places to scorodite. Another mode of occurrence was noted on 
the 760-foot level of the Western Utah mine, at ground-water 
level, where tiny crystals of supergene arsenopyrite rest upon 
a mixture of iron oxides and scorodite. 

Calaveritef (AuTes). — Kemp M has described a mineral from 
the Lucy L mine that "afforded the characteristic and unmis- 
takable test for tellurium and sweated under the blowpipe 
little beads of gold. Traces of lead and antimony were also 
indicated. The mineral is a silvery, thin-bladed brittle variety 
and would suggest a telluride or stibnite to an observer." 

SULPHOSALTS 

JamesonUe (4FbS.FeS.3Sb 2 S 8 ).— Identified by M. N. Short, 
of the Geological Survey, in several polished specimens of ore 
from the U.S. mine. In the sections it appears as a bladed 

» Kemp, J. F., Notes on Gold Hill and vicinity, Tooele County, Utah: Eeon. 
Geology, vol. 13, p. 260, 1918. 



112 



GOLD HILL MINING DISTBICT, UTAH 



mineral with a galenalike color that has replaced arsenopyrite, 
pyrite, and sphalerite. No galena was found in the specimens 
containing jamesonite, and the two appear to have been 
Incompatible. 

Boulangerite (PbjSbiSn). — Identified by Mr. Short in a speci- 
men from the wall rock of the Rube mine. It was rather abun- 
dant as small particles in limestone. Microchemical tests by 
Mr. Short showed that it contained appreciable amounts of 
arsenic. 

Aihinite (2PbS.Cu 2 S.Bi 2 S 3 ). — Small amounts of the bismuth- 
bearing sulphide aikinite were identified by Mr. Short in speci- 
mens from both the Cyclone and U.S. mines. It is associated 
with galena and appears to have formed relatively late in the 
sequence of sulphide minerals, 

Tetrahedrite and tennantite (5Cu 2 S.2(Cu,Fe,Zn)S.2SbaS 3 ; 
5Cu 2 S.2(Cu,Fe,Zn)S.2As 2 S3).- — Microchemical tests by Mr. 
Short showed that both tetrahedrite and tennantite are present 
in the ores of the district. Neither, however, is free from vary- 
ing quantities of the other mineral, and it is probable that all 
gradations between the two end members could be found. No 
correlation could be made between the content of arsenic or 
antimony and the type of deposit in which the mineral was 
found, although the amount of material tested was not suffi- 
cient to make this conclusion a certainty. Small quantities 
of these two minerals were found in the veins having silicate 
minerals in the gangue, but they are most abundant in the 
quartz-sulphide veins and in the limestone replacement bodies, 
where they appear to be of nearly the same age as galena. 
Quartz veins containing tetrahedrite (or tennantite) as the chief 
sulphide are widely distributed, particularly in the vicinity of 
Hoyal Gulch. In these veins the minerals contain considerable 
amounts of silver, specimens from the Undine claim being said 
to run as high as 409 ounces to the ton. 



Fluorite (CaF 2 ) . — Small amounts of purple and white fiuorite 
are associated with danburite on the Gold Bond claim. 

OXIDBS 

Quartz (Si0 2 ). — Quartz, as is usual, is the most abundant and 
widely distributed mineral in the ore deposits and was also 
introduced in considerable amounts in the metamorphism of 
hoth the sedimentary rocks and the quartz monzonite. It is 
relatively rare in the pipelike deposits; becomes more abundant 
in the veins with silicate minerals in the gangue (some of which 
contain only a few remnants of silicates surrounded by quartz) ; 
is the dominant constituent of the quartz-sulphide veins; and 
becomes progressively less abundant in the carbonate and sul- 
phate veins. It is the chief gangue mineral, except for the 
replaced limestone, in the replacement deposits. 

Much of the quartz found associated with the ore deposits 
characterized by silicate minerals is relatively coarse-grained 
and contains numerous fluid inclusions, within which are gas 
bubbles. This habit is also found in much of the quartz that 
has replaced the quartz monzonite. In the quartz-sulphide 
veins the grain size is also relatively large, but the fluid inclu- 
sions were not observed to be so abundant. Much of the quartz 
associated with the limestone replacement bodies and composing 
the jasperoids, however, is extremely fine-grained and appar- 
ently free of the fluid inclusions. This material locally is 
associated with contemporaneous opal and barite, and much of 
it has apparently resulted from the crystallization of a gel-like 
material. (See pp. 93-94.) 

In several specimens there is good evidence for the presence 
of some supergene quartz. One from the Rube mine, for exam- 
ple, is made up of quartz molded on pyromorphite and contain- 
ing euhedral crystals of plumbojarosite. 

Chalcedony (SiO z ). — All the occurrences of chalcedony are 
considered to be supergene. It was found on specimens col- 



lected near the outcrops of different types of ore bodies and 
occurred both as veinlets and as cavity Mings. It is locally 
associated with both opal and quartz. 

Opal (Si0 2 .nH 2 0). — Some opal that is definitely hypogene 
was noted in thin sections of the silicified wall rock in the U.S. 
mine. The opal occurred as irregular microscopic inclusions 
in fine-grained quartz. (See pi. 8, C.) All the other occur- 
rences of this mineral, however, are probably supergene, and it 
is generally associated with chalcedony. Opal was locally 
abundant on the Undine claim and in the Alvarado mine, but 
elsewhere it was noted only in small quantities. 

Hematite (Fe 2 3 ). — The specular variety of hematite was 
found on the Reaper claim and in several of the veins with 
silicate gangue, notably on the Gold Bond claim, where it clearly 
replaced tourmaline (see pi. 10, J3) and was replaced by 
danburite. 

Hematite is undoubtedly present in the oxidized portion of 
many of the ore bodies, but no attempt was made to distinguish 
it from goethite, and the two have been grouped together and 
described as iron oxides throughout this report. 

Spinel (MgAl 2 4 ). — A green isotropic mineral of high relief, 
recognized in a thin section of altered rock from the Undine 
claim, was identified as spinel. It was partly replaced by 
muscovite. 

Magnetite (FejOi). — Small quantities of magnetite were found 
in several deposits of different types. For the most part it 
has replaced calcite that appears to have formed relatively 
late, but on the Doctor claim it has replaced apatite and amphi- 
boie. In much of the altered quartz monzonite it is also abun- 
dant and has apparently formed as a result of the alteration. 
It is suggested that this mineral tends to form as a result of 
the attack of the later stages of mineralizing or metamorphosing 
solutions upon earlier-formed iron-bearing minerals. On the 
Undine claim there is a considerable amount of magnetite that 
has replaced limestone. This material was reported by the 
owner of the claim to carry 0.96 ounce of gold to the ton. 

Rutile (Ti0 2 ). — In several specimens of an altered quartz 
monzonite porphyry dike from the Western Utah mine the 
original biotite was found to be altered to chlorite, sericite, cal- 
cite, and an acicular mineral that has the habit of rutile. 

Wad (amorphous brown manganese oxide of indefinite com- 
position). — Small black nodular masses embedded in a clay 
mineral were found in the walls of the oxidized ore bodies of 
the Western Utah mine. The material gave off chlorine when 
dissolved in hydrochloric acid, left a large insoluble residue, 
and gave a strong test for manganese, all of which indicate that 
it is probably wad. 

Copper pitch (amorphous cupric oxide of indefinite composi- 
tion, usually containing silica and manganese). — Much of the 
chalcopyrite in the district has been altered to a dark-brown to 
black resinous-appearing substance that has been called copper 
pitch. Remnants of chalcopyrite are found in most of the 
material, and veinlets of chrysocolla and other oxidized copper 
minerals are generally associated with it. Some of this material 
from the Silver King claim was reported to contain 62 percent 
of copper and must therefore be composed largely of copper 
oxides. 

CARBONATES 

Calcite (CaCOa) . — Calcite is a wide-spread constituent of both 
the metamorphosed rocks and the ore deposits. Considerable 
quantities are found in the pipes and veins with silicate minerals 
in the gangue, in which it appears in general to be later than 
all the silicate minerals. Its relations to quartz are contradic- 
tory, as in some places it is earlier and in others later. Locally 
it is closely associated with either magnetite or specularite and 
appears to be roughly contemporaneous with them. In most of 
the limestone replacement ore bodies and in the quartz-sulphide 
veins calcite is rare, its place being taken by ankerite or siderite. 



MINBKALS OF THE METAMOBPHOSED BOCKS AND THE ORE DEPOSITS 



113 



A peculiar habit of the caleite was observed in a thin section 
from the ore of the Rube mine, A veinlet shown in the slide 
was composed of caleite crystals developed normal to the walls 
of the veinlet. These showed. an extinction inclined to the 
direction of growth, however, and the crystals must therefore 
be elongated parallel to the rhomb faces rather than the prism 
faces, 

Caleite is also wide-spread as a supergene mineral, and in 
several places it was observed associated with supergene opal 
or as well-formed crystals on iron oxides. 

Dolomite ((Ca,Mg)CO») and ankerite (CaC0 3 (Mg,Fe,Mn) 
C0 3 ). — Veinlets of pink earbonate cutting the quartz monzo- 
nite in the vicinity of the Midas and U.S. mines were found to 
have a> near 1.70 and are therefore ferrodolomite, or ankerite. 
Carbonates of similar appearance were also found cutting 
several of the quartz-sulphide veins. Very large quantities of 
dolomite were also formed in the limestones of the quadrangle, 
probably during the final stages of metamorphism. In most 
places these weather to shades of brown, indicating that they 
are ferruginous. Some of the dolomitized rock near the Garri- 
son Monster mine weathered to a deep chocolate-brown, and 
blowpipe tests showed that this material contained also some 
manganese. 

Siderite (FeCO a ). — Rather large quantities of siderite are 
found on the 700- and 760-foot levels of the Western Utah mine. 
The mineral resembles closely the "dry-bone ore" of many 
mining districts, but chemical tests show that it is almost pure 
siderite and contains less than 1 percent of zinc. This siderite 
has replaced the limestone beds immediately north of the lower 
ore body of the mine and is limited downward by the ground- 
water level. It is clearly supergene. 

In several of the quartz-sulphide veins some hypogene siderite 
is present as thin veinlets cutting the sulphides. One of these 
veinlets in ore from the Copper Queen Midland prospect was 
tested microscopically and found to have a near 1.83, indicating 
an FeCOj content of 75 percent. It is probable that there are 
all gradations between this material and the ferrodolomite 
found at the U.S. and Midas mines. 

Large crystals of an iron-rich carbonate are also found in 
many of the carbonate veins. At the surface, however, these 
have largely weathered to iron oxides, but the preservation of 
the carbonate cleavage lines indicates their original nature. 

Smithsonite (ZnCQj). — Small quantities of smithsonite are 
present in the Garrison Monster mine, and probably it can also 
be found in the oxidized ores of some of the other limestone 
replacement ore bodies. 

Cerusite (PbCOa), — Small quantities of cerusite were found 
in almost all the mines containing lead ore. Most of the occur- 
rences of this mineral are coarse-grained gray masses associated 
with galena but generally separated from it by a zone of angle- 
site. In the Garrison Monster mine, however, the mineral is 
in the form of the familiar "sand carbonate" and is unusually 
abundant. Locally small cream-colored terminated crystals of 
the mineral were observed. In almost all places the cerusite 
has been partly replaced by plumbojarosite. 

Malachite (CuC0 3 .Cu(OH) 2 ). — Veinlets and small crystals of 
malachite can be found in all the mines that have copper sul- 
phides in the hypogene ore. It is generally associated with 
azurite, chrysoeolla, and copper pitch. 

Azurite (2CuC03.Cu(OH)j). — Azurite is relatively rare, but 
small quantities of it were noted as an oxidation product of 
copper sulphides at several localities. 

Bismutite (Bi 2 3 .0O 2 .HjO?). — The mineral referred to bis- 
mutite is a common constituent of the ores in the Wilson Con- 
solidated, Lucy L, and Copper Bloom claims. It has formed 
as a result of the oxidation of bismuthinite. In places the mate- 
rial is pseudomorphous after the sulphide, preserving the old 
cleavage planes perfectly. This variety of the mineral is gray 
in color and is foT the most part isotropic with an index of refrac- 



tion greater than 2.15. It is apparently not of homogeneous 
composition, for in thin section it is streaky and of variable 
eolor. The gray color is possibly due to the content of tiny 
bismuthinite remnants, because in specimens in which the min- 
eral is not pseudomorphous but is localized along fractures of 
quartz or caleite it is granular in habit and is either green or 
yellow. Some of this material has a rather high birefringence. 
No optical distinction could be made between the yellow and 
green varieties, and it is possible that the green color may be 
caused by relatively small amounts of admixed malachite. 

SILICATES 

Orthoclase (KAlSi a 8 ). — Orthoclase feldspar is one of the most 
abundant silicate minerals that were formed during the meta- 
morphism of the quartz monzonite and of the intruded sand- 
stones and calcareous sandstones. In the vicinity of the Wil- 
son Consolidated mine, for example, a sandstone bed in one 
place is almost completely converted to orthoclase; and near 
the Yellow Hammer mine the quartz monzonite in several 
places was found to contain as much as 50 percent of intro- 
duced orthoclase. The mineral is also present in large amounts 
in the pipelike deposits, where single crystal faces more than 
1 foot across were observed, and in smaller quantities in many 
of the veins with silicate gangues. The color in most occur- 
rences is pink. 

The orthoclase is generally perthitic and locally has been 
replaced by rather coarse-grained white albite, particularly in 
the pipelike deposits, but this feature has also been observed 
in the metamorphosed quartz monzonite. The mineral appears 
to have been, except for albite, one of the last of the anhydrous 
silicates to form, as it has replaced garnet, diopside, epidote, 
and amphibole. In several localities it has been replaced by 
minerals characterized by the presence of mineralizers, such as 
tourmaline and danburite, and replacement by quartz and ser- 
icite has been very common. 

Albite (NaAlSijOs). — Noted in several specimens from the 
pipelike deposits and in the altered quartz monzonite, where 
it has replaced orthoclase. It is also present in the orthoclase 
in the form of perthitic inclusions. 

Oligoclase (albite with 10 to 30 percent of CaAl 2 Si 2 8 ). — 
Small amounts of a fine-grained mineral identified as oligoclase 
were found in altered limestone at the Alvarado mine. 

Diopside (CaMg(Si0 3 ) 2 ). — Diopside is an abundant constitu- 
ent of both the metamorphosed quartz monzonite and the altered 
sedimentary rocks. Where the mineral is found in the igneous 
rock it may be readily distinguished in thin sections from the 
augite that is a sparse original constituent by the larger size of 
the crystals, their euhedral habit, and the fact that they have 
replaced all the original constituents. The mineral is partic- 
ularly abundant in the altered limestones and sandstones, in 
some of which it is present to the almost complete exclusion of 
other minerals. It is relatively rare in the pipelike deposits 
but is abundant in many of the veins with silicate gangue. It 
is probable that in some occurrences the mineral is aluminous, 
as much of it has replaced garnet. It has also been observed as 
a replacement product of zoisite, epidote, and titanite. Locally 
the diopside has been replaced by amphibole, the alteration 
starting along the cleavage lines. Orthoclase has also replaced 
this pyroxene, and in the altered limestone woUastonite has 
developed at its expense. 

WoUastonite (CaSi0 3 ). — WoUastonite is one of the most abun- 
dant silicates in the metamorphosed limestones. It occurs 
as bladed crystals that may be an inch or more in length, and 
locally it has almost completely replaced a thick limestone bed. 
It is generally associated with small quantities of garnet and 
diopside, both of which have been replaced by it. WoUastonite 
itself in many places has been altered to the mineral spadaite, 
particularly in the vicinity of the gold-bearing veins having 
silicate minerals in the gangue. The woUastonite can be readi- 



114 



GOLD HIL1 MINING DISTBICT, UTAH 



ly distinguished optically from tremolite, which it closely resem- 
bles, by the fact that it has a transverse optic plane. A spec- 
imen from the Cane Springs mine gave the following optical 
data: a near 1.618, y near 1.628, optically negative, rather 
small 2V and transverse optic plane. 

Tremolite (CaMg3(Si0 8 ) 4 ). — Tremolite was recognized micro- 
scopically in two specimens of homfels from the Lucy L claim. 
These specimens were altered members of the Oquirrh formation. 
The mineral was not found in any of the specimens of altered 
Ochre Mountain limestone. 

Aclinolile (Ca(Mg,Fe)j(Si0 3 ) 4 ) and hornblende (similar to 
actinolite but containing alumina, ferric oxide, and alkalies). — 
Monoclinic amphiboles are wide-spread both in the metamor- 
phosed sedimentary and igneous rocks and in the pipes and the 
veins having silicate minerals in the gangue. In the altered 
rocks amphibole has generally replaced diopside and locally 
garnet, a common mode of occurrence being along the cleavage 
lines of the older pyroxene. This habit is also found in many 
of the silicate veins, and in both modes of occurrence the am- 
phibole has been partly replaced by calcite, chlorite, sericite, 
and quartz. Orthoclase, tourmaline, apatite, humite, and 
scapolite have also replaced the amphiboles. In the pipelike 
deposits the mineral is a conspicuous constituent. Here it has 
a sheaf-like habit, and individual clusters of crystals more than 
3 feet in length may be observed. Bemnants of diopside have 
been found in these crystals, but it is uncertain to what extent 
these giant crystals have formed at the expense of a preexistent 
pyroxene. The same minerals have replaced the amphibole in 
the pipes as in the other occurrences. 

There appears to exist a nearly continuous gradation between 
a strongly colored hornblende and a nearly colorless (in thin 
section) variety that is probably actinolite. The darker vari- 
eties are the older and in many specimens are altered along 
cleavage planes to the lighter and nonpleochroic actinolite. 
The large crystals found in the pipe on the Reaper claim seem 
to have a composition intermediate between pargasite and 
common hornblende, as is shown by the following optical data: 
o near 1.628, y near 1.645; optically negative; 2V large; pleo- 
chroism, X=pale yellow-green, Y=deep green, Z=blue-green. 

Garnet (R"iR'"j(Si04)j). — Garnet is an abundant constituent 
both of the metamorphosed rocks and of many of the ore 
deposits. It appears to have been one of the first minerals to 
form during the postmagmatic stage of igneous activity and 
generally has been more or less completely replaced by younger 
minerals. There is a rather wide variety of composition repre- 
sented by the specimens collected, as the indices of refraction 
range from 1.777 to 1.91. Most of the specimens tested, how- 
ever have n near 1.88, indicating a dominance of the andradite 
molecule. The specimen (from the Lucy L mine) whose index 
was 1.91 was associated with titanite and is probably titaniferous. 

Where the age relations of the different varieties could be 
determined, the garnet with the higher index of refraction was 
generaEy thought to be older. This variety also seemed to show 
fewer optical anomalies than the garnets of lower index. The 
birefringence of some of the gamete was close to 0.008, and 
those specimens that were tested were found to be optically 
positive. Twinning and zonal growth were also observed in 
many of the garnets, and skeleton crystals in calcite are rather 
abundant. 

Scapolite group (Ca 4 Al,Sia025-Na4AlsSi|,0 M Cl) . — Minerals be- 
longing to this group were recognized microscopically in 
specimens from the Rube, Doctor, and Gold Bond claims. In 
the specimen from the Rube the mineral is associated with 
calcite and chlorite. The birefringence is about 0.030, a being 
about 1.55, and y near 1.58. This indicates a composition near 
the meionite end of the series. In the other two specimens the 
scapolite has replaced garnet and hornblende. The material 
from the Doctor claim shows a well-developed prismatic cleav- 
age, has a small optic angle, is optically negative, and has 



o= 1.539 and y= 1.549. In this occurrence, therefore, the 
composition is rather close to the marialite end member. 

Vesuvianite (complex calcium-aluminum silicate containing 
OH and F). — Vesuvianite was noted in thin sections of the gold 
ore from the Midas and Cane Springs mines. In the Cane 
Springs specimen it occurred as large crystals in association with 
zoisite, from which it was distinguished by its uniaxial negative 
character. In this occurrence it was older than diopside and 
wollastonite, having been partly replaced by these minerals. 

Zircon (ZrSiO<), — Abundant crystals of zircon were noted 
under the microscope in several specimens of metamorphosed 
rocks and also in a specimen from the pipe on the Reaper claim. 
They showed the simple combination of prism and pyramid 
faces, were optically positive, and had a moderately strong 
birefringence. 

Dattburite (CaB 2 (Si04) 2 ). — Flesh-colored massive danburite 
is abundant on the Gold Bond claim, where it was found in 
veins as irregular or lenticular masses that were more than 1 
foot across. The mineral had replaced specularite and was 
itself partly replaced by calcite. The following optical data 
were determined by W. T. Schaller and E. P. Henderson: 
Orthorhombic, optically positive, 2E large, a= 1.627, 6"= 1.629, 
7=1.632. 

Andalusite (Al 3 Si0 5 ) . — Andalusite was noted in several speci- 
mens taken from the Manning Canyon formation near the 
quartz monzonite stock. An extended description of the occur- 
rence of the mineral near the Cane Springs mine has been given 
by Kemp. 84 

Zoisite (Ca2(A10H)Al 2 (SiOi)3). — Greenish-brown zoisite was 
recognized in several specimens of altered limestone and also 
in the gold ores from the Cane Springs, Rube, and Bonnemort 
claims. It is locally associated with vesuvianite. Where it 
has formed in calcite, euhedral crystals a quarter of an inch in 
diameter may be found. In other specimens the mineral has 
formed at the expense of garnet and ha3 itself been replaced by 
diopside, wollastonite, spadaite, and chlorite. The index of 
refraction near 1.72, low birefringence, biaxial positive character, 
parallel extinction, and small optic angle are characteristic. 

Clinozoisite (Ca s (A10H)Al 2 (Si04)3). — Brownish-green radiat- 
ing fibrous crystals of clinozoisite were found in a specimen of 
metamorphosed limestone near the Frankie claim. 

Epidote (HCa 2 (Al,Fe)3SijOis). — Two varieties of epidote were 
recognized in the specimens collected. A normal green epidote 
was found in the pipe on the Doctor claim and in the wall rock 
of the silicate vein on the Frankie claim. The other variety was 
in the form of black euhedral crystals 3 millimeters in maximum 
length in the tungsten-bearing ores on the Reaper, Yellow 
Hammer, and Lucy L claims and in the wall rock of the Gold 
Bond claim. The mineral had the following optical properties: 
Biaxial negative; 2 V large; strong dispersion (r> v on material 
from the Lucy L and r<v on specimens from the Gold Bond); 
a near 1.745, y near 1.772; twinned and strongly zoned; notably 
pleochroic, X=pale yellow to nearly colorless, Z=deep greenish 
brown to nearly opaque. The pleochroism is unlike that 
reported for other epidotes and is similar to that of allanite, 
but the indices are much too high for allanite. These crystals 
were among the first minerals to form in the deposits in which 
they are found, being associated with titanite and garnet. It 
is possible that the unusual properties of the mineral may be 
due to the presence of titanium, as the garnet in some of these 
deposits has properties suggesting that they also are titaniferous. 

Axinile (a borosilicate of aluminum and calcium). — Axinite 
was found by Butler m at several localities. It was not recog- 
nized by the writer in any of the specimens collected by him, 



» Kemp, J. F„ Notes on Gold Hill and vicinity, Tooele County, Ctoh: Eoon. 
Geology, vol. 13, pp. 254-257, 1918. 

>» Butler, B. 8„ Ore deposits of Utah: U.S. Geol. Survey Prof. Paper 111, p. 479, 
1920. 



MINERALS OF THE METAMORPHOSED ROCKS AND THE ORE DEPOSITS 



115 



but its presence in Butler's specimens was checked by optical 
determinations. 

Hvmite group (Mg(F,OB) 2 .MgSiQr-Mg(F,OHj).Mgj(S104)»)- — 
Considerable quantities of a pale flesh-colored mineral thought 
to be humite were found on the Calaveras and Frankie 
claims. The mineral has replaced garnet, tourmaline, ortho- 
clase, and other silicates and appears to have been the last 
silicate to form. It has been extensively replaced by calcite 
and some quartz. A similar mineral was recognized in the 
altered wall rook of the lower ore body in the Western Utah 
mine. The . following optical data were determined: Biaxial 
positive, large axial angle, parallel extinction, o near 1.619, 
-y near 1.652. 

Calamine (H 2 ZnSi0 5 ). — Small crystals of a mineral deter- 
mined optically and chemically as calamine were found in the 
oxidized ore of the Garrison Monster mine. It was associated 
with clay minerals and iron oxides. 

Tourmaline (complex silicate of boron and aluminum). — 
Tourmaline is of wide-spread occurrence in the district. It 
has been noted along joints in the quartz monzonite, as a con- 
stituent of the metamorphosed rocks (particularly in the Man- 
ning Canyon formation, in which it forms stubby black crystals 
as much as an inch in length), and as a common mineral in 
many of the ore deposits with silicate minerals in the gangue. 
It was formed relatively late, for the only minerals noted as 
having replaced it are danburite, specularite, quartz, sericite, 
and calcite. The tourmaline is generaEy found in sheafs of 
acicular crystals, which, on the Reaper claim, reach a length 
of several inches. In these occurrences the color of the mineral 
is a brilliant black, and under the microscope its indices were 
found to be «= 1.655 and «= 1.695, and the pleochroism pale 
yellow-green to almost opaque. In several places the black 
variety was replaced by a fine-grained aggregate of sericite, 
calcite, quartz, and blue tourmaline, in which the pleochroism 
was w=pale blue-green and «=colorless. 

Muscovite (RiKAh(8iOi)t) . — Muscovite, particularly the fine- 
grained variety sericite, is widely distributed in both the altered 
sedimentary and igneous rocks and in all types of the ore 
deposits. The mineral formed relatively late and has replaced 
all the other silicate minerals. It is generally associated with 
chlorite, quartz, and calcite. It 1b probably also in part at least 
contemporaneous with many of the metallic minerals, although 
in the Western Utah mine it has clearly replaced arsenopyrite. 
It occurs with quartz in all the gold ores of the district and is 
present in the wall rocks of the quartz-sulphide veins. The 
more coarsely crystalline form known as muscovite was recog- 
nized in several of the ore deposits with silicate minerals in the 
gangue. 

Biotiie ((H,K)a(Mg,Fe)jAla(Si04)a). — Biotite is an abundant 
constituent of the metamorphosed shales of the Manning 
Canyon formation and is associated with quartz and andalusite. 
It was also observed in small quantities associated with musco- 
vite in the pipe on the Reaper claim and in vein material from 
the Gold Bond claim. 

Chlorite group (HgMgsAlsSijOig) . — Two varieties of chlorite 
were distinguished. The more abundant variety is nearly black 
when viewed In the mass and is green and pleochroic under the 
microscope. Much of it is either isotropic or has an extremely 
low birefringence. This variety is a wide-spread constituent of 
the metamorphosed rocks, particularly the quartz monzonite, 
and is generally found in association with sericite and quartz, 
having replaced the older minerals. It is also abundant in many 
of the ore deposits that contain silicate minerals. The second 
variety is colorless in thin section and has an appreciable bire- 
fringence. Materia] from the Rube mine was biaxial positive 
and had the following indices of refraction: a = 1 .549, y = 1 .653. 
The relations of this variety to the green chlorite are not known, 
but it is probably somewhat later, as it is a constituent of 
jasperoid in several localities, particularly in the U.S. mine. 



Jejferisite (complex magnesium-aluminum silicate). — The 
vermiculite known as jefferisite was found in several places in 
the low-lying region north and west of the town of Clifton, 
either in the limestone at the quartz monzonite contact or in 
some of the silicate veins near the contact. In the veins it was 
associated at several places with magnetite. The mineral 
occurred as dull-green plates that were as much as 1% inches 
in diameter in the occurrences in limestone. and y were close 
to 1.575, and C. S, Ross determined 2V to be about 11°. 

Talc (H 3 Mg3(Si03)«.) — Talc was identified by C, S. Ross in a 
thin section of ore from the Rube mine, in which it was present 
as fibrous fine-grained patches associated with calcite in mus- 
covite. 

Spadaite (MgO.SiOj.2H 3 0). — The unusual mineral spadaite s « 
was found to be relatively abundant in the gold ores of the 
Alvarado and Cane Springs mines and was also recognized in a 
specimen of ore from the Midas mine and in metamorphosed 
limestone near the Monocco claim. In ah the occurrences it 
has replaced wollastonite (see pi. 8, B) and has itself been 
locally replaced by quartz. It occurs as a fine-grained aggregate 
of fibers and in mass has a yellowish or pinkish color. The 
following analysis was made on a specimen from the Cane 
Springs mine that was largely composed of this mineral: 

Analysis of spadaite from Gold Hill, Utah 

[W. T. Schaller, analyst] 

Insoluble 8.68 

SiC>2 soluble in Na»COj ,. 41 

8i0 2 43. 28 

Fe s 3 . 22 

FeO . 27 

CaO„ 1.58 

MgO 24. 72 

H 2 0~ - 10. 36 

H,0+ 10. 51 

100. 03 

Deducting from this the impurities — 8.68 percent insoluble 
residue (diopside and garnet), 3.27 percent wollastonite (based 
on the CaO percentage), 0.41 percent opaline silica (soluble in 
10 percent Na 2 COa solution), 10.36 percent water at 110°, and 
0.22 percent FeaOa as limonite — and recalculating to 100 per- 
cent gives the following figures for the composition of the min- 
eral, with which may be compared the analysis of the original 
material from Italy: 





doM Hill 


Italy 


SlOi 

FeO - 

MgO— — - - - 


53.96 

.35 

32.08 

13.64 




56.00 
.86 

30.67 


H,0 - - - 

AHO3 - 


11.34 
.66 










100.03 


99.33 



Clay minerals (hydrated aluminum silicates) . — Clay minerals 
are found in the vicinity of many of the oxidized ore deposits 
in the district. In many places they occur as a sort of casing to 
the oxidized ore, a relation that is well illustrated by the body 
of clay that surrounds the lower portion of the gold-bearing 
quartz lens on the Lucy L claim. These minerals are commonly 
associated with iron oxides, and in one place they enclose masses 
of the mineral wad. They have apparently been formed as a 
result of the reaction between the sulphuric acid generated by the 
oxidation of the sulphides in the ore body and the silicate miner- 
als in the wall rocks. At least three varieties of clay minerals 

m Senate, W. T., and Nolan, T. B„ An occurrence of spadaite at Qold Hill, Utah: 
Am. Mineralogist, vol. 18, pp. 231-238. 1931. 



116 



GOLD HILL MINING DISISICT, UTAH 



were recognized under the microscope, and in many places these 
may occur together. One variety has an index of refraction 
near 1.57 and a low birefringence — properties that correspond to 
those of the kaoiinite group; another has indices lower than 
Canada balsam and a distinctly higher birefringence than the first 
variety and is possibly related to beidellite. The third variety 
is isotropic, and different specimens have indices ranging from 
1.51 to 1.55. This variety has been referred to as halloysite. 

Nonlronite (Pe2O3.3SiO2.2H2O). — Nontronite, which is isomor- 
phous with the clay mineral beidellite, was found as a yellow- 
green powdery coating on ore specimens from several mines in 
the district. 

Chrysocolla (CuSi03.2H 2 0). — Chrysocolla was noted in 
specimens from several mines and prospects as thin veinlets 
cutting copper pitch or as coatings on ore or wall rock. In 
the Western Utah extension mine it was in turn coated by the 
arsenic-bearing conichalcite. 

TITANOSILICATES 

Titanite (CaTiSi0 5 ) . — Titanite was found to be an abundant 
constituent of some of the specimens of metamorphosed quartz 
monzonite and was also found in the ore of several of the tung- 
sten-bearing pipes and veins. It occurs as swarms of small 
euhedral crystals from 0.1 to 1 millimeter long and is in many 
places associated with epidote and diopside. The diopside has 
locally replaced the titanite, and danburite, specularite, and 
orthoclase have also been noted as being distinctly later. 

PHOSPHATES, ABSENATBS, VANADATES, AND ANTIMONATBS 

Apatite (Ca»(F,Cl)(POi)a). — Considerable quantities of a pale 
flesh-colored or yellowish apatite are present in the tungsten 
pipes north of Clifton. In these occurrences the mineral tends 
to have crystal outlines, and crystals nearly an inch across are 
not uncommon. It is normally embedded in amphibole and 
clearly has replaced that mineral. On the Doctor claim it has 
been replaced by magnetite. Flakes of iron oxide along irreg- 
ular cracks in the mineral in places give it a distinctly pinkish 
color. On the Copper Bloom claim the ore contains numerous 
small crystals of yellow or greenish crystals of apatite that are 
about an eighth of an inch in diameter. These appear to have 
replaced tourmaline. The mineral has also been recognized 
microscopically in some of the gold-bismuth ore. 

Pyromorphile (PbjCI(POi) j) . — Pyromorphite was identified by 
E. P. Henderson in a thin section of oxidized ore from the Rube 
mine. It occurred both in large prismatic crystals and in mas- 
sive aggregates coated by supergene quartz and was partly 
replaced by plumbojarosite. 

Mimetite (PbsClfAsO^s). — Creamy-white crystals of mime- 
tite were identified chemically by Mr. Henderson in oxidized 
ore from the Western Utah mine. He also recognized the min- 
eral in oxidized ore from the Red Jacket claim, but at this 
locality the color was greenish. 

Olivenite (Cu 2 (OH)AsOi). — Deep olive-green olivenite was 
recognized by W. T. Schaller and W. F. Foshag and was also 
identified by the writer in oxidized ore from the Western Utah 
Extension mine, where it was coated or partly replaced by coni- 
chalcite. Under the microscope the mineral was seen to have a 
high birefringence and 2V near 90°. is a little higher than 1.80. 

Adamite (Zn 2 (OH)As04). — Adamite was identified chemically 
by Mr. Henderson in oxidized ore from the Western Utah mine. 
It occurred as tiny white prisms with scorodite and iron oxides. 
Under the microscope the indices were seen to be near 1.73. 
The mineral has a prismatic cleavage, parallel extinction, and 
is optically positive. 

Descloizite ((Pb,Zn)j(OH)VO<). — Small crystals of descloizite 
were determined by W. T. Schaller in oxidized lead ore from the 
New Baltimore claim. 



CUnoclasite (Cu s As 2 Og.3Cu(OH)2). — Clinoclasite was identi- 
fied by W. F. Foshag in oxidized ore from the upper ore body of 
the Western Utah mine. 

Arseniosiderite (CaiFe(As0.i)t<3Fe(OH)s). — Several specimens 
of arsenic ore from the Western Utah mine were found to con- 
tain considerable quantities of arseniosiderite. In some spec- 
imens it appears to have formed at the expense of massive scoro- 
dite; in several, however, it is not associated with scorodite 
but contains blebs of jarosite or is coated with beudantite and 
mimetite. The mineral is found in aggregates of fine-grained, 
rather fibrous crystals that have a lustrous pale greenish-brown 
color and a reddish streak. Specimens gave qualitative tests 
for calcium, iron, and the arsenate radicle. The following 
optical data were also determined: Indices of refraction between 
1.82 and 1.88, birefringence moderate, slightly pleochroic in 
reddish browns. 

Ferrisymplesitef (3Fe 2 3 .2As20s.l6H 2 0). — A bright-yellow 
powdery mineral coating a mixture of quartz and arsenopyrite 
from the U.S. mine was submitted to W. T. Schaller for identi- 
fication. He writes. "The yellow coating contains ferric iron 
and arsenate with some lime and sulphate (probably due to 
gypsum). There is no uranium present. Ammonia does not 
turn it red, like pharmacosiderite. It may be related to ferrl- 
symplesite, 87 which has the formula 3Fe 2 Q8.2As 2 05.16H 2 0. 
Refractive indices 1.650±. Strong birefringence." 

Scorodite (FeAsO«.2H 2 0). — Scorodite is by far the moat abun- 
dant oxidation product of the large masses of arsenopyrite that 
occur in the district. The largest quantities of the mineral are 
found in the Western Utah mine, in which the upper and middle 
ore bodies are composed almost completely of this mineral and 
also the lower ore body down to the 700-foot level. The amount 
in the U.S. mine is considerably less, because here oxidation 
extends only locally below the adit level. Scorodite is also 
present in the oxidized portions of all the other ore bodies in 
which arsenopyrite is one of the hypogene sulphides. The 
material that has been called scorodite varies widely in color and 
appearance. (See pp. 105-106 and pi. 12, A, B.) Most of it 
is extremely fine grained and breaks with a conchoidal fracture. 
Thin sections of such specimens show that it is composed of an 
isotropic streaked mineral that may be either white or brownish. 
The isotropic mineral is in many places in sharp contact with 
crystalline scorodite, much of which, however, is so fine grained 
that it has an appearance not unlike that of the isotropic sub- 
stance. In most places this crystalline scorodite contains an 
admixed iron oxide, and the color of the mixture is brown of 
various shades, depending upon the amount of iron present. 
Where the iron oxides are absent the scorodite is deep green. 
In a few places the size of grain increases and crystals as much 
as an eighth of an inch in diameter may be found. A specimen 
obtained just above the 150-foot level of the Western Utah 
mine was composed almost entirely of crystalline material 
from which the following optical data were determined: Biax- 
ial positive, moderate 2V, dispersion r>v; indices, a= 1,788, 
0=1.797, 7 = 1.818. Foshag, Berman, and Doggett" have 
recently studied the crystalline scorodite from the Western Utah 
mine and give the following optical properties: 

"The mineral is optically negative 31 ; 2V=54°±5°. r>v 
(easily perceived in the interference figure but not sufficiently 
strong to measure on the Fedorow stage) . The indices of refrac- 
tion for yellow light, as determined by the Merwin dispersion 
method, are as follows: <*=1.784±0.001, /3=1.796±0.002, 
T=1.814±0.001. Dispersion F-C=0.03±0.005." 



» Walker, T. L., and Parsons, A. L., The arsenate of cobalt, nickel, and iron ob- 
served in the silver-bearing veins at Cobalt, Ontario: Toronto Univ. Studies, Oaol. 
ser., no. 17, p. 17, 192*. 

» Foshag, W. F., Berman, Harry, and Doggett, B. A., Scorodite from Gold Hill. 
Tooele County, Utah: Am. Mineralogist, vol. IS, pp. 390-391, 1930. 

»» Obviously a misprint for positive. — T. B. N. 



MINERALS OF THE METAMORPHOSED ROCKS AND THE ORE DEPOSITS 



117 



Foshag's analysis of the mineral is as follows: 

Analysis of scorodite from Gold Hill, Utah (U.S.N.M. 

Fe 2 3 34 13 

A1 2 3 None 

FeO .84 

CaO .38 

MgO .01 

As 2 Oj 48. 42 

PzOj None 

H 2 + ,. 15. 73 

H 2 0- .23 

Insoluble .42 



100. 14 



Conichalcite ((Cu,Ca) 3 As 2 8 .(Cu,Ca)(OH) 2 HH 2 0).— The basic 
copper arsenate conichalcite appears to be the most wide- 
spread of the several green copper arsenates found in the 
oxidized ores of the district. It was recognized in specimens 
from the Western Utah and Western Utah Extension mines, 
in both of which it occurs chiefly as a mammillary coating on 
scorodite, iron oxides, or other minerals. It was also observed 
in one specimen as a replacement product of the olivenite. The 
mineral has a distinctly fibrous habit and under the microscope 
was seen to be nonpleochroic, with parallel extinction, with 
the slow ray parallel to the elongation, and optically positive. 
It is either uniaxial or has a very small optic angle and has a 
(or ai) near 1.76 and 7 (or e) near 1.80. 

Pharmacosiderite (6FeAs0 4 .2Fe(OH) 3 .12H 2 0). — Heikes * writes 
that the ore of the Western Utah mine is a "cellular mass 
of scorodite and brownish oxidized mineral (pharmacosider- 
ite?)." 

Beudantite (3Fe 2 3 .2Pb0.2S0 3 .As 2 6 .6H 2 0) .— A jarositelike 
mineral containing lead and arsenic is present in large quan- 
tities in the district, particularly in the Western Utah mine. 
It is probable that there are all gradations between pure plum- 
bojarosite and beudantite. The mineral is in all places very 
fine grained and appears to have been one of the most recent 
of the oxidation products to form. The color js generally 
yellow-brown, but one specimen was greenish. Under the 
microscope the mineral is seen to occur in well-formed crystals, 
either as flat hexagonal plates or as positive and negative rhombs 
combined with the basal face. 

SULPHATES, CHROMATES, AND TELLURATES 

Barite (BaS0 4 ). — Barite is present in small quantities in 
almost all the jasperoid masses. It has also been recognized 
in several of the quartz-tetrahedrite veins. The mineral is 
particularly abundant in the Garrison Monster mine, where it 
is found in the vein itself and in the limestone wall rock. At 
this place it is later than the sulphide minerals and locally has 
replaced them. Large quantities of barite are also present in 
the barite veins and limestone replacement bodies at several 
places in the quadrangle. In these the barite appears to have 
been the only mineral introduced. 

Anglesite (PbS0 4 ) .— -Anglesite was noted in almost all the 
lead-bearing ore deposits of the quadrangle^ It was developed 
as the first stage in the oxidation of galena and generally bor- 
ders and veins the sulphide. It has itself been replaced by 
cerusite and plumbojarosite. In the Rube mine native gold 
was observed embedded in anglesite in several specimens. 

Gypsum (CaS0 4 .2H 2 0). — Considerable quantities of crystal- 
line gypsum were found at the ground-water level in both the 
U.S. and Western Utah mines. 



«° Heikes, V. C, Arsenic in 1923: U.S. Qeol. Survey Mineral Resources, 1923, 
pt. 1, p. 166, 1924. 



Chalcanthite (CuS0 4 .5H 2 0). — Blue and greenish-blue glassy 
crystals of chalcanthite half an inch in maximum length were 
found embedded in copper pitch on the bottom level of the 
Alvarado mine. The mineral was also recognized in the Cyclone 
mine, where it occurred on the walls of the drift and had ob- 
viously formed since the workings had been driven. 

Siderolil (FeS0 4 .5H 2 0) . — Siderotil is associated with chal- 
canthite and copper pitch in the Alvarado mine. It is a pale- 
green fibrous fine-grained mineral that occurs in areas of rec- 
tangular outline. These areas, however, are cut by numerous 
desiccation cracks, and the mineral is probably pseudomorphous 
after melanterite. It is soluble in water and gives qualitative 
tests for iron and sulphate. The indices of refraction are a 
near 1.52, 7 near 1.54. 

Jarosite (K 2 Fec(OH)i 2 (S0 4 ) 4 ). — Because of the difficulty in 
distinguishing members of the jarosite and related groups from 
one another except by chemical tests, it is uncertain how wide- 
spread the occurrence of pure jarosite is in the oxidized ores of 
the district. Most of the specimens tested contained lead, but 
several were lead-free and gave flame tests for potassium, so 
that jarosite is definitely present in at least some of the ores. 
One specimen from the U.S. mine contained no lead but did 
contain arsenic, so that there is probably a series comparable 
to the plumbojarosite-beudantite series in the lead-free minerals. 

Natrojarosite (Na 2 Fee(OH)i 2 (S0 4 ) 4 ). — A specimen of a jarosite 
mineral from the Western Utah mine was found on testing to be 
free from lead and potassium and gave a strong flame test for 
sodium. It is probably natrojarosite. 

Plumbojarosite (PbFe 6 (OH)i 2 (S0 4 ) 4 ). — Plumbojarosite or gra- 
dations between it and its arsenic-bearing analog, beudantite, 
is probably the most abundant lead mineral in the oxidized ore 
of the district. It is found in all the lead-bearing veins and 
is clearly later than either anglesite or cerusite, and in many 
places it also veins and coats iron oxides. In the Rube mine 
the mineral is embedded in supergene quartz. Variations in 
the arsenic content may be found in the same mine. In the 
Western Utah mine, for example, a specimen from the south 
end of the open cut contained almost no arsenic, and another 
less than 100 feet away contained a considerable percentage of 
it. The mineral is found in various shades of brown and is 
always very fine-grained. At the Monocco mine lessees shov- 
eled all run of mine ore through a screen and shipped the screen- 
ings, which were composed largely of plumbojarosite. Like 
beudantite, the mineral is seen under the microscope to be in 
the form of well-developed crystals, either as the common flat 
hexagonal plates or in crystals made up of combinations of 
rhomb faces and the base. 

TUNGSTATES AND MOLYBDATES 

Wolframite ((Fe,Mn)W0 4 ). — Hess found wolframite on the 
Keno claim, according to his unpublished notes. 

Scheelite (CaW0 4 ). — Only small quantities of scheelite can 
now be found in the district, but it has been recognized in several 
of the pipes and veins having silicate minerals in the gangue. 
The numerous large crystals on the Reaper claim described by 
Butler 41 are no longer there, having been mined during the 
World War when the demand for tungsten was at its height. 
Similar deposits nearby have also been almost completely 
stripped of the visible scheelite. In the specimens collected by 
the writer from the Wilson Consolidated, Reaper, Centennial, 
Yellow Hammer, and Copper Bloom claims the scheelite 
appears as a dull-white or yellowish mineral of rather greasy 
appearance and in places is very similar to the apatite that also 
occurs in these deposits. The two may be readily distinguished 



« Butler, B. S., Ore deposits of Utah: U.S. Geol. Survey Prof. Paper 111, p. 478, 
192a 



118 



GOLD HILL MINING DISTRICT, UTAH 



under the microscope, however, by reason of the high index of 
refraction of the scheelite, as well as its higher birefringence. 
In all the specimens studied the scheelite was seen to have formed 
relatively early, and it has been replaced in different specimens 
by amphibole, tourmaline, chlorite, sericite, quartz, and 
sulphides, 

Cuprotungstite (CuW0 4 ). — Hess recognized cuprotungstite 
on the Keno claim, according to his unpublished notes, 

Powellite (Ca(Mo,W)0,i). — Powellite was found as white 
porcelaneous pseudomorphs after molybdenite at several 
places on the Reaper claim. 

Stolzite (PbWO«). — The stolzite was questionably identified 
by Butler ** in a specimen from the Wilson Consolidated mine. 

Wulfenite (PbMo0 4 ). — Small brilliant orange-colored crystals 
of wulfenite are present in the oxidized ore of several of the 
quartz-sulphide veins north and northwest of Clifton, such as 
the vein on the Red Jacket claim, in which it is associated with 
mimetite. 

MINES AND PROSPECTS 

The mines and prospects in the quadrangle are 
included in the Clifton and Willow Springs mining 
districts. The Clifton district is by far the more 
productive of the two. Its outlines are not well 
defined but are approximately those of the area shown 
on plate 2. The boundary between the two districts 
has never been fixed, so far as known, but in practice 
the line of Overland Canyon is used to separate them. 
The Willow Springs district extends for some distance 
beyond the southern boundary of the quadrangle, 
but the prospects outside of the quadrangle were not 
examined during this survey. 

The descriptions of individual mines and prospects 
in the Clifton district are arranged in the same order 
as that in which the different types of ore bodies were 
described. Several of the mines contain more than 
one type of deposit however, and for such mines, the 
more productive type was used to determine the 
position of the description. 

It is probable that the names here used for some of 
the prospects no longer apply, because each year many 
of the unpatented claims are allowed to lapse by 
omission of the required assessment work. Many of 
these claims are then restaked under new names. 

CIIITOH DISTBICT 
HISTORY OF MINING AND PRODUCTION 

The following account of the early history of the 
Clifton district is quoted from Heikes: 13 

The first discovery of mineral is said to have been made in 
1858, but the hostility of the Indians retarded development 
until 1869, when the irst mining operations were begun and the 
district was organized (on October 18). Huntley 44 reviews the 
conditions in November 1880 as follows: 

"A smelter was built in 1871 and was moved in 1876 to a spot 
6 miles distant by the St. Louis Consolidated Co. Probably 
150 tons of bullion were produced. * * * About 50 claims, 



« Butler, B. S., Ore deposits of Utah; U.S. Qeol. Survey Prof. Paper 111, p. 482, 
1920. 

« Heikes, V. 0., Ore deposits of Utah: U.S. Qeol. Survey Prof. Paper 111, p. 478, 
1920. 

« Precious metals: Tenth Census U.S., vol. 13, p. 4S6, 1885. 



of over 500 located, are still worked occasionally. Little has been 
done since 1877. " 

The smelter built in 1871 is reported by an old resident u and 
mine owner of the district to have been a stack furnace 
operated with three blacksmith bellows. Three tons of lead 
bullion represented the results of the first operations. In 1872 
Gilbertson & Berry's furnace was built at Clifton to treat the 
ores from the Gilbertson mine at Gold Hill. About 30 tons of 
lead bullion « shipped to Salt Lake averaged $93 in silver per 
ton. A few years later this furnace was moved to Gold Hill 
by J. W. Harker. The crude ore smelted carried about $4 in 
gold, 30 ounces of silver per ton, and 25 to 30 percent of lead. 

Activity in mining did not again assume importance until 1892, 
when a mill was put in operation at Gold Hill. The ores treated 
were from the Cane Springs, Alvarado, and Gold Hill claims, 
which were credited with a total gold production of $207,986 
from September 1892 to November 1895. Of this total probably 
half the ore and more than three-fifths of the gold came from 
the Alvarado mine. No complete record of the amount of 
ore handled exists, but a partial record shows 9,475 tons of ore 
milled from August 1892 to May 1894, assaying $14 per ton 
and yielding $97,393, or $10.28 per ton. At the same rate, the 
total ore worked was about 19,000 tons." The gold produced 
was very pure, some of it 0.946 fine. 

The Midas property is about 3 miles southeast of Clifton. 
In 1896 and prior to that year 95 tons of ore averaging $56 in 
gold and a traee in silver per ton were treated at the Cane 
Springs mill and shipped to the smelter. In 1902 a 40-ton 
cyanide mill was constructed and treated 622 tons with a re- 
ported saving of $15 per ton in gold. In 1904 the mill was 
operated again, but the results were unfavorable, and the 
property was practically abandoned. 

In 1906 the Western Utah Copper Co. acquired the 
principal properties on Gold Hill, and during the 
succeeding 10 years this company confined its efforts 
to development work in anticipation of the construc- 
tion of a branch line of the Western Pacific BaUroad 
from Wendover. In this period there was no produc- 
tion from the district except for small lots from a few 
prospects. 

Construction of the long awaited branch railroad 
was finally started in 1916 and completed in 1917; in 
that year the production of the district amounted to 
33,960 tons of ore valued at $705,957. Over half of 
this came from the Western Utah Copper Co.'s Gold 
Hill mine. From this initial production shipments 
gradually declined, except for a slight rise in 1920, 
until in 1922 only 211 tons of ore was shipped. In 
1923 and 1924, however, a demand for arsenic, which 
had been discovered in large quantities at the Gold 
Hill mine, caused a temporary revival. The collapse 
of the arsenic market in 1925 caused a curtailment of 
activities, and the production for the following year 
dechned sharply. Since 1926 the production has been 
made up chiefly of small and intermittent shipments. 

The following table shows the production of gold, 
silver, copper, lead, and zinc in the district from 1901 
to 1932, the figures being obtained from the annual 



« Dunyon, Isaac, Salt Lake Oity, personal Interview. 

« Fabian Bentham, Resources of Utah, 1872, p. 18, Salt lake Oity, Utah, 1873, 

<; Daggett, Ellsworth, unpublished mining notes. 



MINES AND FBOSPECTS 



119 



statistical reports by V. C. Heikes (1905-25) and 
C. N. Gerry (1926-32) in Mineral Resources of the 
United States. It is not complete for the years before 
1914, but the omissions are probably of no great 
importance. There have been in addition small ship- 
ments of tungsten, bismuth, and molybdenum ore, 
but nothing is known as to their monetary value. 



The production of arsenic ore is also uncertain, for 
most of it was shipped on the basis of a fiat rate 
per ton. Bough estimates, however, indicate that the 
arsenic ore contained about 9,000 tons of metallic 
arsenic, which, when converted to As s O«, would have 
had a value of about $2,500,000, on the basis of the 
average prices during the years of production. 



Gold, silver, 


copper, lead, 


and zinc produced in the Clifton district, 


1901-88 






Year 


Ore (tons) 


Qold (ounces) 


Silver (ounces) 


Copper (pounds) 


Lead (pounds) | Zinc (pounds) 


Value 


1901 


18 
651 




68 
641 

« 
92 

C) 
C) 
C) 
C) 
C) 
« 
C) 
C) 
(«) 
146 
149 
645 
161, 204 
97, 241 
53, 706 
89, 578 
23, 208 
2,974 
41, 195 
147, 786 
111, 372 
13, 772 
4,413 
1,578 
1,229 
3,704 
2,384 
1,207 




666 
6,000 




$69 


1902 .- 


482.20 






10, 554 


1903 






1904- ■ 


1,660 


969. 00 


20, 085 


1905— 










1906 








1907 _ 






j- 








1908 _ 














1909 














1910 ' 














1911 














1912 








1913.. 














1914. 


66 

16 

67 

33, 960 

19, 714 

14, 2S7 

39, 656 

11, 627 

211 

13, 237 

33, 094 

I3j 721 

1,382 

526 

195 

415 

1,009 

2,259 

2,915 


57.25 

5.21 

8.90 

564. 31 

449. 56 

233. 89 

77.43 

266.09 

278. 61 

860. 60 

511. 05 

808. 90 

1, 129. 20 

926. 04 

3.24 

480.27 

77.84 

1, 142. 40 

2, 361. 00 


5,054 

1,470 

10, 547 

1, 894, 731 

828, 658 

194, 476 

y«*j yitj 

3,194 

4,521 

33,040 

3,615 

54, 459 

13, 826 

2,396 

2,995 

40,001 

47, 885 

22, 046 

6,473 






1,936 


1915 


1,924 

4,782 

513,929 

1, 204, 472 

778, 869 

1, 010, 833 

336, 292 

16, 524 

291, 554 

1, 840, 453 

1, 960, 853 

267, 083 

53, 701 

50,233 

1,237 

280, 480 

458, 723 

174, 084 




530 


1916 

1917 





3,532 
705, 957 


1918 , 

1919 




396, 730 

142, 439 


1920 




197, 204 


1921 

1922 




44, 253 
10, 252 


1923 


76, 836 


1924 




257, 290 
272, 339 


1925 


2^ 243" 

14, 754 


1926 - _ - 

1927—. 


55, 416 
26, 286 


1928 

1929 


4,355 
17, 703 


1930 




23, 284 


1931 


43, 285 


1932 













> Not recorded. 



MINES AND FBOSPECTS 



MPlUtKE DEPOSITS 



The Reaper group of claims, owned by the Seminole 
Copper Co. and managed by the Wilson Brothers, of 
Salt Lake City, is about three-quarters of a mile west 
of north from Clifton, The group appears to have 
made the largest production of all the several tungsten 
prospects in the Clifton district, but the total amount 
is not known. It must have been very much less than 
100 tons of 60 percent ore, for that figure represents 
the total production from Utah during the period 
1914-18 and includes ore shipped from several other 
districts. 

The ore body was developed by a vertical shaft 
105 feet deep, from which were driven 2 levels, 
one at the bottom of the shaft and one 56 feet 
higher. The upper level was driven beneath the out- 
crop, from which the ore body was removed by means 
of an open stope to the surface (fig. 13). There are 
in addition several other shallow prospect holes on 



the property. Those adjacent to the main workings 
are shown in figure 14. 

The country rock of the vicinity is quartz monzonite. 
Where unaltered, this appears to be normal mineralogi- 
cally but of rather finer grain than the average speci- 
mens. Locally the rock has a distinctly pink color, 
due to the introduction of feldspar. A green pyroxene 
has also replaced the rock in some places. In a speci- 
men of waE rock from the 100-foot level the original 
plagioclase of the quartz monzonite had been partly 
altered to albite and calcite, and the dark minerals 
had been completely replaced by calcite, sericite, and 
iron oxides. Some orthoclase has been introduced into 
the rock, giving it a distinctly pink color in the hand 
specimen, and in addition there are several areas of 
clear, glassy quartz and black tourmaline. Locally 
also veinlets of an iron-rich calcite with some fine- 
grained quartz cut the quartz monzonite. The quartz 
monzonite at this locality must have been about at 
the upper boundary of the stock, for at the higher 
altitudes to the northeast and southwest are sedimen- 
tary rocks whose contacts with the igneous rock are 
nearly horizontal. 



120 



GOLD HELL MINING DISTBICT, UTAH 



Two thin basic dikes were found in this vicinity and 
are shown in figure 14. Neither was traced for any 
distance because of the poor surface exposures, but 
they appear to have had no influence upon the ore. 
A light^colored quartz carbonate vein is also exposed 
nearby, It strikes a little west of north and may be 
traced for several hundred feet by means of its con- 
spicuous light-colored float. 

The ore body was an irregular pipelike mass of 
pegmatite with a north-northeast trend and a nearly 
vertical dip. At the surface the mass had an elliptical 
shape with a long axis of nearly 60 feet and a short 
axis of about 30 feet. On the 50-foot level it was 
considerably smaller and had a circular outline about 



SHAFT 2S' 




so Feet 



Fkhjbe 13,— Plan of main workings, Eeaper claim. 

20 feet in diameter, from which two apophyses ex- 
tended, one to the northwest and one to the north- 
northeast. On the bottom level the pipelike character 
is not apparent, and the pegmatite minerals are found 
in a lenticular zone striking northeast. Near the north 
end of the lens a blunt apophysis extends to the north- 
west. The deposit thus shows on a small scale a form 
characteristic of many larger bodies of ore-bearing 
material, a pipelike shape at the surface, which con- 
tracts in size downward and eventually changes into 
a tabular form. 

The walls of the pegmatite are not sharp and defi- 
nite, as they simply mark the limit of replacement of 
quartz monzonite by the pegmatite minerals. In gen- 



eral the boundary between wall rock and ore body is 
not notably irregular, but locally bunches of pegmatite 
minerals may be found beyond this boundary and 
entirely within the quartz monzonite. The apophyses 
noted in the preceding paragraph represent accelerated 
replacement of the waE rock along preexistent frac- 
tures. On the 50-foot and 100-foot levels small dis- 
continuous stringers of pegmatite minerals in the 
quartz monzonite are the only indications of the 
approach to the blunt south end of the pegmatite. 

The two most abundant minerals in the pegmatite 
appear to have been green amphibole and pink ortho- 
clase. The amphibole is found in sheafs as much as 
4 feet in length. It has been locally replaced along 
the cleavage planes by chlorite, biotite, muscovite, 
calcite, or quartz. Orthoclase is also found in large 
crystals, single cleavage faces as much as a foot across 
being noted. It is later than the hornblende, which 
it has replaced. White albite is found with the ortho- 
clase in some places. Apatite is surprisingly abun- 
dant. Much of it has a pink coloration due to films 
of iron oxide along fractures in the crystals, but a 
large proportion has a light cream color and closely 
resembles scheelite. Molybdenite and its oxidation 
product, powellite, are afso found in many places. 
Black tourmaline, in many places accompanied by 
glassy quartz, occurs in considerable quantities around 
the edges of the pegmatite and is also present in 
bunches in the quartz monzonite wall rock. 

Small aggregates of sulphides, now largely Oxidized, 
are locally conspicuous within the pegmatite. They 
are especially abundant at the north end of the bot- 
tom level, where with quartz they form much of this 
part of the pegmatite lens. Chalcopyrite appears to 
have been the most abundant sulphide but is now 
represented by copper pitch and malachite. In addi- 
tion to these minerals, epidote, titanite, diopside, and 
zircon were identified microscopically. Subhedral 
magnetite was also found, a specimen from the dump 
showing the mineral embedded in a white calcite. 

Tungsten was present in the form of scheelite. Very 
little of this mineral can now be found either under- 
ground or on the dump. It is reported to have oc- 
curred abundantly in the stope from the 50-foot level 
to the surface, in the central portion of the pipe, 
Butler examined this property during its develop- 
ment and writes as follows * 8 concerning the occurrence 
of the scheelite: 

Adjacent to the shaft ** a body composed largely of scheelite 

18 to 24 inches in thickness had been exposed for 4 or 5 feet 
along the strike and 3 or 4 feet below the outcrop. Deeper 
in the shaft other apparently smaller bodies of scheelite were 
exposed. The scheelite occurs in large crystals, some of which 
are 4 inches long. One block of nearly pure scheelite ore on the 
dump was estimated to weigh fully 200 pounds. 



« Butler, B. S„ Ore deposits of Utah: U.S. Oeol. Surrey Prof. Paper 111, p. 478, 
1920, 
« This shaft was in the part of the ore body removed daring the sloping. — T. B . N; 



MINES AND PEO8PECT8 



121 



The bodies of high-grade ore appear to occur as lenticular 
masses in the vein and suggest segregations of the scheelite 
through the pegmatite material of which the scheelite is an 
essential part. The scheelite was one of the earliest minerals 
to form. Much of it is in well-formed crystals and little of it 
includes the other minerals. 

According to the Wilson brothers, who developed 
the deposit, the ore also contained some gold. No 
bismuth minerals were found during mining, however. 



Pits 1 and 4 expose quartz veins that carry minor 
amounts of sulphides. Galena and tetrahedrite are 
the most abundant, but some ehaleopyrite was ob- 
served. Malachite and other oxidized copper minerals 
are present, and some of the galena has been replaced 
by covellite. In specimens from pit 1 the quartz in- 
cluded irregular areas of barite and also a few euhe- 
dral crystals of this mineral. 






PIT N0.7 

Hornblende, quar t z, 
specularite vein 



N 



pit No.e (caved) 
Q) Orthoclase, 
tourmaline, 
etc. 




Basic 
dike 



\ 



Quartz 
monzonite 



M3 



Quartz 
monzonite 



3 ■ 

' SHAFT ■ • 



PIT NO.-* 

Quartz-galena 



,/Vr NC.3 

Quartz- 
carbonate 
vein 



Basic dike 



pit no, 5 
Hornblende, 
quartz, ete.veirt 



Settling cA 
• tanks -XV 



Quartz-barite- 
galena vein 



SO O 

\ t. t i i {_ 



[I 



Quartz, horn blende,-':. - 
tourmaline,etc.veiri.; 



PIT NO. 2 

(25 'deep) 



150 Feet 



EXPLANATION 
Vein 



> 75 

Strike and dip of vein 

Strike of vertical vein 



Figure 14. — Prospect pits and mineraliiatloii adjacent to Beaper open cut. 



Rather similar pegmatites were present in pits 2, 5, 
7, and 8 (fig. 14), but little or no scheelite has been 
found in them. In all but pit 8, which is caved, the 
pegmatites had a distinctly veinlike habit and thus 
resembled the relatively barren lower portion of the 
main ore body. Pit 7 showed in addition to the usual 
pegmatite minerals a considerable amount of specula- 
rite, and much of the quartz in this body had a purple 
color, due to finely disseminated hematite. 

38811—35 9 



About 1,000 feet northwest of the main shaft, on 
the adjoining Rex claim, also owned by the Seminole 
Copper Co., there is a smaller body of pegmatite 
that is of similar character to the main body of the 
Reaper. Some scheelite has been found at this place. 
In the altered wall rock of this body there are 
moderate amounts of disseminated sulphides, of which 
those recognized were pyrite, ehaleopyrite, bornite, 
and molybdenite. 



122 



GOLD HILL MINING DISTRICT, UTAH 



YELLOW HAMMEB 



The Yellow Hammer property includes three claims 
about three-quarters of a mile northwest of Clifton. 
The Reaper group adjoins it on the east, and the Cen- 
tennial on the west. The claims are owned by the 
Western Utah Copper Co. The property is developed 
by several shallow workings and by a shaft that was 
inaccessible at the time of the survey. The only 
recorded production was made in 1917, when 1,646 
pounds of scheelite that averaged 69.5 percent of W0 3 
was shipped. 

The claims are all in the quartz monzonite, but sed- 
imentary rocks are found nearby in every direction 
except to the southeast. As in the adjoining Reaper, 
the present surface at the Yellow Hammer is thought 
to be very near the original upper surface of the intru- 
sive. The quartz monzonite where unaltered shows no 
pecularities, biotite or biotite and hornblende being 
the dark minerals. In many places, however, it shows 
a rather striking alteration to a pink fine-grained rock 
with numerous green splotches. Orthoclase appears 
to be the most abundant mineral in the pink portions 
of the rock, and the green mineral is an amphibole 
that is similar to those found in the ore bodies. A 
specimen of the wall rock of one of the tungsten-bearing 
ore bodies showed none of this alteration, however. 
In this specimen calcite, sericite, and chlorite were 
moderately abundant, and in addition it contained small 
quantities of a brown pleochroic epidote resembling 
allanite and numerous small crystals of titanite. 

The ore bodies that were seen on these claims are 
more tabular than pipelike and thus resemble the lower 
part of the Reaper deposit. The walls, like those of 
other deposits of this type, are not sharp. The vein- 
like or tabular habit seems to be controlled by a major 
fracture, along which the ore-depositing solutions 
entered and from which they extended for varying 
distances into the walls. In many of the deposits 
mineralization has extended along other fractures at 
angles to the main one. All the deposits that were 
examined are of small size, having a length of less than 
25 feet and a width of less than 5 feet. 

The minerals forming the ore bodies are similar to 
those of the Reaper. Green hornblende, in many 
places altered to quartz and calcite, pink orthoclase, 
black tourmaline, albite, apatite, chlorite, muscovite, 
quartz, and sulphides, more or less oxidized, are readily 
recognized. Scheelite is rather irregularly distributed 
in the deposits. It was observed in several places in 
the prospect about 400 feet south of the main shaft. 
It can be readily recognized by its good cleavage, dull- 
gray color, and greasy luster. In this deposit the long 
sheafs of hornblende show a strong tendency to occupy 
the central part of the ore body, and tourmaline is 
generally found near its borders. 

Copper, chiefly in the form of copper pitch, chaleo- 
pyrite, and malachite, is locally abundant in most of 



the ore bodies. Custer 60 writes that "samples from 
the ore exposed gave 0.40 to 0.62 ounce gold, 1.40 to 
3.80 ounces silver and 1.36 to 1.68 percent copper," 

DOCTOR 

The Doctor claim is just south of the junction of 
the branch road to the Yellow Hammer mine with the 
road from Clifton to Gold Hill, about three-quarters 
of a mile northwest of Clifton. It was owned in 1917 
by Duncan MacVicbie, of Salt Lake City, and, so far 
as known, still belongs to him. The developments 
consist of a shallow shaft, now inaccessible, and several 
surface cut®. A small amount of tungsten ore is 
reported to have been shipped from the claim. 

The claim includes the contact between the quartz 
monzonite and poorly exposed sandstones and lime- 
stones of the Oquirrh formation. The two principal 
openings, however, are in the quartz monzonite about 
50 feet east of the contact. In the more northerly one 
the ore seems to have occurred in a small pipelike 
body that has a diameter of about 5 feet and dips 
65°-70° W. The walls of the pipe are poorly defined, 
and bunches of silicate minerals occur in the surround- 
ing igneous rock. In the southern prospect the ore 
zone is more veinlike. 

The ore was composed of scheelite, quartz, calcite, 
magnetite, and sulphide and silicate minerals. The 
silicates recognized include green crystalline epidote, 
pale-greenish scapolite, partly altered actinolite, abun- 
dant brownish-green garnet, black tourmaline, ortho- 
clase, albite, chlorite, and sericite. The sulphide 
minerals occur chiefly with the quartz and include 
chalcopyrite, bornite, and pyrite. Copper pitch and 
malachite are plentiful as oxidation products. The 
sulphides are more abundant in the more southern of 
the two workings. No scheelite was observed by the 
writer, but Hess," who examined the deposit in 1917, 
notes that "the scheelite is nearly white in pieces 
reaching more than 2 inches through. * * * A 
couple of hundred pounds of good ore is said to have 
been taken from the hole." He also notes the presence 
of bismuth in the deposit. 

CENTENNIAL AND ENTERPRISE 

The Centennial and Enterprise claims are about a 
mile northwest of Clifton, west of the Yellow Hammer 
mine and north of the road from Clifton to Gold Hill. 
The claims are reported to be owned by M. E. Jones, 
of Salt Lake City. The developments consist of 
several cuts and shallow shafts. Only one shipment 
from the property is recorded. This was made in 1917 
and consisted of 47 tons of ore that assayed 0.05 ounce 
of gold and 1.6 ounces of silver to the ton and 5.4 per- 
cent of copper. Scheelite is found in some of the 



» Custer, A. B., Deep Creefr, Clifton mining district, Utah: Eng. and M in. Jour., 
vol. 103, p. 916, 1917. 
*' Hess, P. L., unpublished notes. 



MINES AND PROSPECTS 



123 



prospect holes, but it is not known whether or not any 
tungsten ore was shipped. 

The claims cover the contact of the quartz monzo- 
nite with the Oquirrh formation. The trend of the 
contact here is irregular in detail, and both igneous 
and sedimentary rocks have been considerably meta- 
morphosed. Just west of the Enterprise claim the 
sedimentary rocks have been replaced by jasperoid, 
and to the greater hardness of this rock is due hill 6455. 

The ore lies close to the contact in both the sedimen- 
tary and the igneous rocks. The pit near the south 
end of the Enterprise claim is on a pipelike mass in 
the quartz monzonite, whose position seems to have 
been controlled by the intersection of two fractures, 
one striking N. 7° E. and dipping 70° E. and the other 
striking N. 60° W. and dipping south. Green amphi- 
bole, black tourmaline, apatite, calcite, quartz, and 
sulphide were recognized, in addition to much iron 
oxide and splotches of blue tourmaline, which together 
with sericite, quartz, and calcite is pseudomorphous 
after large crystals that were probably originally black 
tourmaline. In the prospect hole in quartz monzonite 
on the Enterprise claim the zone strikes N. 75° W. but 
apparently does not cross the contact into the sedi- 
mentary rocks. Black tourmaline is the most abundant 
mineral ; green amphibole, jeff erisite, quartz, muscovite, 
iron oxides, copper pitch, and malachite also occur. 

In the prospect in the Oquirrh formation on the 
Centennial claim the copper minerals are found in 
belts on a band of silicate rock that strikes northeast. 
The silicate minerals appear to be chiefly diopside and 
green amphibole. Magnetite is unusually abundant 
here, and with it are crystals of the green micaceous 
mineral jefferisite. Copper is found as copper pitch, 
malachite, and chalcopyrite. In one specimen com- 
posed largely of porous green amphibole a poorly de- 
fined pinkish-gray patch proved to be chiefly scheelite. 

VEINS WITH SI1ICATE MINERALS IN MI GANGU! 



The Frankie mine is immediately west of the Lucy 
L mine and north of the Calaveras claim. It is owned 
by the Woodman estate. In addition to a number 
of surface cuts and pits, it is developed by a tunnel, 
whose portal is at the 5,972-foot point shown on the map 
and from which several stopes extend upward to the 
surface. The mine was actively worked in 1917-19, 
during which 3,056 tons of ore was shipped that had 
an average content of 0.08 ounce of gold and 1.5 ounces 
of silver to the ton, 4,8 percent of copper, and 0.7 per- 
cent of lead. The lead ore seems to have been ob- 
tained from a different deposit than the copper ore 
and to have contained relatively more silver and less 
gold. The writer was informed that some scheelite 
was found on the property and that a small quantity 
of it was shipped. 



The geologic relations at- the Frankie are rather 
similar to those at the Calaveras, which adjoins it on 
the south. Metamorphosed limestones and sand- 
stones of the Oquirrh formation cap the ridge above 
the mine workings and are limited on both the east 
and the west by dikelike masses of quartz monzonite. 
The dike on the east side is the narrower of the two, 
being from 200 to 500 feet across, and ends abruptly 
near the north end of the claim. On its east side it is 
intrusive into the Ochre Mountain limestone, and from 
the exposures to the north it is seen that this dike has 
followed the line of a normal fault separating the Ochre 
Mountain limestone from the Oquirrh formation. The 
outcrops of the Oquirrh formation in the region be- 
tween the two masses of quartz monzonite are rather 
widely altered to garnet, diopside, clinozoisite, humite, 
and wollastonite. The quartz monzonite is also 
altered, a specimen taken from the southern pit at 
the contact with the sediments containing garnet, 
titanite, epidote, calcite, and chlorite as introduced 
minerals. 

The ore is found in a zone 20 feet or less in width at 
the contact of the eastern dike of quartz monzonite 
with the Oquirrh formation. The zone strikes west 
of north and dips about 65° E. at the north but steep- 
ens to nearly 90° at the south. Ore has been found 
for a distance of over 250 feet along the contact, chiefly 
in the metamorphosed sedimentary rocks and to a 
small extent in the quartz monzonite. 

The ore has a gangue of generally fine-grained sili- 
cate minerals. Black tourmaline and a green garnet 
are the most striking of these, possibly because in 
many places they occur, unlike the other silicates, in 
rather large, euhedral crystals. Diopside, amphibole, 
apatite, and humite also appear to be abundant, and 
calcite alone or with fine-grained quartz forms a matrix 
in much of the rock. The ore minerals are pyrite, 
bornite, and chalcopyrite with their oxidation prod- 
ucts, chiefly copper pitch, chrysocolla, and malachite. 
The sulphides and to a less extent the silicate minerals 
show a pronounced tendency to occur in sheets parallel 
to the contact. This habit is probably the result of a 
preexistent sheeted zone parallel to the normal fault 
that apparently localized the dike of quartz monzonite. 
A moderate amount of the sulphide, however, is found 
in blebs within the silicate rock. Thin sections of 
such ore show that the sulphides are almost invariably 
embedded in the calcite matrix rather than intergrown 
with the silicates. 

The copper content of the ore mined appears to 
have been rather constant throughout the stoped por- 
tion of the ore body. No scheelite was recognized 
in the field, and the average content of this mineral 
is not known but is presumably low. The deposit 
from which the lead ore was shipped was not examined 
during the survey. 



124 



GOLD HIIA MINING DISTRICT, UTAH 



CALAVERAS 

The Calaveras claims, owned by the Western Utah 
Copper Co., are about 2 miles south of Gold Hill, 
south of the Frankie claim and west of the Gold Bond. 
The developments consist of 4 shallow pits on the 
ridge line southeast of summit 6266 and 2 tunnels 
on the slope west of the ridge. Some shipments of 
ore are reported from the claims, but their grade and 
quantity are not known. 

The area covered by the claims includes part of a 
narrow band of the Oquirrh formation extending south- 
ward from the Frankie that is irregularly embayed by 
quartz monzonite. The igneous rock is a part of the 
dikelike mass that lies west of the main stock. Both 
sedimentary and igneous rocks have been extensively 
altered, and in many places it is extremely difficult 
to locate exactly the contact between them. 

Ore bodies are exposed both in the quartz monzonite 
and in the sediments. Those in the igneous rock are 
small pipelike shoots composed largely of quartz. In 
the northernmost pit in the quartz monzonite black 
tourmaline is abundant, but in the southernmost pit 
this mineral appears to have been replaced by a very 
fine-grained aggregate of blue tourmaline, sericite, and 
quartz. Blebs of copper pitch, in which are locally 
remnants of sulphides, are scattered through these 
gangue minerals, as are coatings of chrysocolla, azurite, 
and malachite. The specimens collected from these 
shoots contain a considerable amount of supergene 
chalcedony. 

The ore body in the sedimentary rocks strikes north- 
east and appears to be localized at the contact with 
the quartz monzonite. The gangue minerals are con- 
siderably more varied than in the quartz monzonite. 
Both a green and a reddish-brown garnet are abun- 
dant, together with a green amphibole, black tour- 
maline, orthoclase, and specularite. A flesh-colored 
fine-grained mineral that appears to have replaced all 
the gangue minerals just named was determined micro- 
scopically as humite. Quartz is not abundant. Pyrite 
and chalcopyrite are the most plentiful sulphides and 
in many places show comparatively little oxidation. 

Custer 52 reports that samples from the property 
assayed 0.11 to 0.20 ounce of gold and 0.20 ounce of 
silver to the ton and 1.99 to 9 percent of copper. 

POLE STAB COPPER CO. 

The Pole Star Copper Co. formerly owned about 
15 claims in the vicinity of Lucky Day Knob, about 
halfway between Clifton and Gold Hill. All but two 
of these were unpatented and have been abandoned. 
The two remaining claims are the Keno and the Pole 
Star, the former lying to the west of Lucky Day Knob 
and the latter to the east. The writer understands 



58 Custer, A. E., Deep Creek, Clifton mining district, Utah: Eng. and Min. Jour., 
vol. 103, p. 918, 1917. 



that the Western Utah Extension Copper Co. was 
under the same control. 

A considerable amount of development work has 
been done on the property. The chief openings are 
an inclined shaft on the Keno claim about 500 feet 
west of Lucky Day Knob, an inclined shaft on the 
Pole Star claim on the eastern slope of the knob at an 
altitude of 6,075 feet, and two tunnels, one about 300 
feet south of the latter shaft and another about 800 
feet west-northwest of it. The recorded production 
from the company's claims amounts to shipments of 
313 tons in 1917. These averaged 0.096 ounce of gold 
and 3.65 ounces of silver to the ton and 2.96 percent 
of copper. 

Quartz monzonite underlies the greater part of the 
two claims. It has suffered a wide-spread but not 
especially intense alteration, during which sericite, 
chlorite, locally some orthoclase, and fine-grained 
quartz have been developed in the rock. Adjacent to 
the ore bodies sericite appears to be the most abundant 
of the introduced minerals. The summit of Lucky 
Day Knob is composed of Ochre Mountain limestone, 
and this formation is also found in several other places 
in the vicinity, suggesting strongly that the roof of the 
quartz monzonite stock was here close to the present 
surface. 

On the Keno claim there are a few surface pits and 
an inclined shaft. The shaft is now caved, but it 
appears to have been sunk on the intersection of two 
veins, one striking about N. 30° W. and dipping 70° W. 
and the other striking nearly west. The quartz mon- 
zonite wall rock is intensely sericitized at the shaft. 
The gangue minerals of the two veins observed were 
green hornblende, black tourmaline, quartz, and rnus- 
covite. The ore consists of oxidized iron and copper 
minerals, the latter being chiefly malachite, azurite, 
chalcedony, and copper pitch. Except for small 
amounts of pyrite, no sulphides were found in the ore 
on the dump. 

On the Pole Star claim the most thoroughly pros- 
pected vein strikes N. 40° W. and dips 35° SW. The 
wall rock is quartz monzonite that is thoroughly 
crushed and sericitized. At the inclined shaft the 
vein is from 3 to 5 feet wide, with local short spurs 
into the walls. Where the tunnel south of the shaft 
intersects the vein the thickness is somewhat less and 
is notably variable, pinches and swells alternating 
within short distances. The ore is similar to that on 
the Keno claim, tourmaline and quartz being the 
most abundant minerals. At the surface the oxidation 
of the ore minerals is complete, but on the tunnel level 
some sulphides still remain. F. L. Hess M during a 
visit to the property in 1917 recognized wolframite, 
scheelite, cuprotungstite, and ferberite (?) in this 
vein. 



» Unpublished notes. 



MINES AND PROSPECTS 



125 



Published descriptions of the property M include 
assays that indicate the presence of local concentra- 
tions of copper-rich and silver-rich material; but the 
grade of the ore shipped seems to show that these 
concentrations must have had a rather slight extent. 

COPPBKOPOLIS (IDA LULL) 

The Copperopolis or Ida Lull group of 6 patented 
and 20 unpatented claims lies on the southeast slope 
of Gold Hill, about three-quarters of a mule southeast 
of the portal of the Western Utah mine. The property 
in 1919 was owned by the Copperopolis Mining Co., 
161 South Main Street, Salt Lake City. It is also 
known locally as the Bamberger mine, after its prin- 
cipal owners. Nearly 550 tons of ore was shipped from 
1917 to 1919, the average metal content of which was 
0.11 ounce of gold and 5.5 ounces of silver to the ton, 
5.6 percent of copper, and 0.6 percent of lead. 

The south end of the mass of sedimentary rocks that 
occurs as a roof pendant in the quartz monzonite and 
underlies Gold Hill is included within the boundaries 
of the group of claims. The jasperoid mass that was 
formed along the fault passing through the crest of 
Gold Hill makes up most of this portion of the pendant. 
The Ochre Mountain limestone, which to the north 
is extensively exposed west of the jasperoid, is almost 
completely lacking at the surface in this region, quartz 
monzonite being in contact with the jasperoid over 
most of the distance. The only known outcrop of the 
Ochre Mountain limestone in this vicinity is at the 
southern tip of the pendant, where there is a small 
mass of lime-silicate rock, to which the limestone has 
been altered. Other small masses of altered Ochre 
Mountain limestone are Exposed in the adit tunnel, 
whose portal is at an altitude of 5,517 feet. 

East of the jasperoid zone both the Manning Can- 
yon formation and the Ochre Mountain limestone are 
exposed to the north. To the south, however, the 
Manning Canyon formation is cut out, owing to the 
more southeasterly strike of the jasperoid. The Ochre 
Mountain limestone outcrop is itself limited on the 
east by a westward-dipping fault that separates it 
from the quartz monzonite. The fault is well exhibited 
in a tunnel on the east side of the low knoll that marks 
the south end of the roof pendant. 

The ore bodies occur in lime silicate rock formed as 
a result of the metamorphism of the Ochre Mountain 
limestone. Three separate shoots have been devel- 
oped. The largest and the one from which the bulk of 
the ore shipped was obtained is on the west side of 
the small knoll at the southern tip of the roof pendant. 
The ore shoot was localized along a nearly vertical 
shear zone in garnet-diopside rock that was 2 or 3 
feet wide and had a strike a few degrees east of north. 
The ore consisted of oxidized copper minerals and some 



M Custer, A. E., Deep Creek, Clifton mining district, Utah: Eng. and Mln, 
Jour., vol. 103, p. 919, 1917. Higgins, W. C, Flourishing condition of Clifton mining 
district: Salt Lake Min. Jour., vol. 19, pp. 21-26, July 15, 1917. 



blebs of the copper sulphides, chalcopyrite and bornite, 
in a matrix of silicate minerals. 

Two smaller ore shoots were found in the adit tun- 
nel (fig. 15). One of these was very near the portal, 
in what was apparently a small mass of altered Ochre 
Mountain limestone on the footwall side of the jas- 
peroid zone. The dimensions of this shoot were small, 
and the ore has been completely stoped out. Carl 
Bailey, of Gold Hill, reports that some scheelite was 
found in this ore shoot. The other ore shoot occurred 
near the face of the tunnel along a narrow fracture zone 
that here forms the contact between the quartz mon- 
zonite and the altered limestone. An interior shaft 
has been sunk to an unknown depth on this shoot, and 
two small stopes extend upward. Not much ore is 
exposed at this locality on the tunnel level. A mass 
of nearly solid chalcocite more than 2 inches in diameter 
was found on the tunnel dump, but it is not known from 
which of the two ore shoots it was obtained. 

NAFOLBON MINING CO, 

The principal workings on the property of the Napo- 
leon Mining Co. are about a mile north of the Western 
Utah mine, on the northwest slope of the small but 
prominent peak known locally as Calico Hill. The 
seven patented claims of the property have also been 
known as the Incas group and were at one time con- 
trolled by the Red Copper Queen Mining & Milling 
Co. Several small shipments of ore have been made 
from the property. Lots aggregating 135 tons that 
were shipped in 1917-18 averaged 0.11 ounce of gold 
and 2.6 ounces of silver to the ton and 6.4 percent of 
copper. 

The ore occurs in a small body of Ochre Mountain 
limestone that on the west and south is irregularly 
embayed by the quartz monzonite and on the east is 
separated by a fault from beds belonging to the central 
facies of the Oquirrh formation. The limestone is for 
the most part bleached and recrystallized, but locally, 
particularly near the contact with the intrusive, it 
is altered to silicate minerals. In other places it has 
a pronounced pinkish-brown color due to the wide- 
spread presence of small quantities of iron oxides. 
Locally the iron oxides are concentrated into "iron 
blowouts." Such masses, however, are shown by sev- 
eral prospect pits to have relatively small dimensions. 

The ore bodies have been developed by several shal- 
low pits or short tunnels and also by two shafts, both 
of which are now inaccessible. 

The ore shoots consist of small lenses of copper- 
bearing lime-silicate rock within a few feet of the quartz 
monzonite contact. The ore minerals are all oxidized 
copper compounds, chiefly copper pitch, malachite, and 
chrysocolla. No sulphide minerals were observed. 

GOLD BOND 

The Gold Bond claim is in Lucy L Gulch, about 
1,500 feet south of the main Lucy L tunnel. It is 



126 



GOLD HILL MINING DISTKICT, UTAH 



now reported to be owned by the Galinske brothers, 
of Sioux City, Iowa, but in 1917 it appears to have 
been the property of the Babcock Mining Co. One 
shipment, presumably of copper ore, is said to have 
been made from the property some time ago, but the 
amount and grade are not known. The developments 
on the claim consist of a tunnel, whose portal is 800 
feet west of the cabin at an altitude of 6,053 feet, and 
several shallow pits. The claim appears to have been 
actively worked in 1917-18. 

The country rock consists of altered quartz mon- 
zonite, in which the dark minerals have been replaced 
by calcite and chorite and much of the remainder of 



ularite are the most abundant minerals. The specular- 
ite has been locally altered to a reddish powdery 
oxide and in such places is generally associated with 
quartz or chalcedony. Coarsely crystalline glassy 
quartz is also found in parts of the vein, and much 
of the copper ore is associated with it. Diopside, 
amphibole, biotite, a white scapolite in part seriei- 
tized, orthoclase also locally sericitized, and purple 
and white fluorite are found less abundantly. Dan- 
burite, the calcium borosilicate, is surprisingly abun- 
dant in the vein but in many places has been partly 
replaced by calcite. In the pit on the vein southeast 
of the tunnel portal danburite makes up a large part 



Ochre Mountain limestone 
largely altered to 
lime- silicate rock 




Fracture 



Strike and dip' of fault 
Strike of vertical contact 



50 



150 Feet 



Slope and raise to surface 
in lime-si/icate rock ? 






Figure 15. — Plan ol adit tunnel, Copperopolis group. 



the rock by a fine-grained mixture of quartz, orthoclase, 

and albite. The quartz monzonite is near the eastern 
edge of an irregular mass that lies west of the main 
stock. Ochre Mountain limestone underlies the east- 
ern part of the claim. 

The largest vein on the claim is exposed in the tun- 
nel. It strikes N. 50° W. and dips 45° SW. The vein 
zone is about 5 feet wide, but this figure includes nearly 
1 foot on each wall that is composed of quartz mon- 
zonite largely replaced by massive dark epidote and 
smaller amounts of other silicate minerals that are 
also found within the ore-bearing portion. In the 
central portion of the vein black tourmaline and spec- 



of the vein and has clearly replaced the other silicates 
and specularite. The ore minerals are copper pitch, 
in which are remnants of chalcopyrite, and other oxi- 
dized copper minerals, chiefly chrysocolla and mala- 
chite. Much of the copper pitch is found within 
quartz, but some of it is embedded in the silicates. 
It/ was 'reported [that during the!, period /of activity at 
this mine the ore taken out carried 2 to 4 percent 
of copper. 55 The writer's observations indicate that 
the distribution of the copper minerals in the' vein is 
irregular. 

6i Schwalenberg, L. G., Mining in the Deep Creek region: Salt Lake Min. Bev., 
vol. 19, p. 43, January IS, 1918. 



MINES AND PKOSPECTS 



127 



There are three other veins on the claim that have 
a similar strike. All three, however, appear to have 
a small horizontal extent and might better be described 
as pipelike. They earrj ore of a similar type but 
show rather less diversity in the number of minerals 
present. 

COPPEB BLOOM 

The Copper Bloom group of claims is about halfway 
between the towns of Clifton and Gold Hill, adjoining 
the Keno claim on the west and south. It is owned 
by the Copper Bloom Mining Co., in which the Wilson 
brothers, of Salt Lake City, are the guiding spirits. 
Shallow shafts and cuts constitute the developments, 
but, so far as known, there has been no production. 

The quartz monzonite that forms the walls of the 
ore bodies is a part of the main Gold Hill stock. The 
area covered by the claims is near the western border 
of the stock, which is, in plan, highly irregular. Sev- 
eral roof pendants composed chiefly of Ochre Moun- 
tain limestone are found east and northeast of the 
claims within the quartz monzonite. 

Four ore bodies have been exposed on the claims. 
In all of them black tourmaline with a sheaf-like habit 
and smaller amounts of coarsely crystalline quartz 
are the most abundant minerals. The two more west- 
erly deposits are about 1 ,500 feet south of west of the 
old Keno shaft. One of these is a vein striking N. 
45° E. and dipping about 65° SE. The vein filling 
consists of black tourmaline with some quartz. Abun- 
dant pulverulent iron oxide fills areas formerly occupied 
by sulphides. Some chalcedony veinlets and coatings 
of yellow-brown jarosite were also recognized. The 
iron oxide is said to be rather rich in gold, with the 
result that locally assays of $50 a ton have been ob- 
tained. Some bismuth is also reported from this vein, 
but none was recognized in the specimens collected. 
Nearby a shaft has been driven on a vein that strikes 
north and dips east. Black tourmaline and quartz 
are the most abundant minerals, as in the other deposit, 
but instead of the iron oxides there are splotches of 
copper pitch, which contain remnants of chalcopyrite 
and pyrite. In one specimen a pseudomorph of bis- 
mutite after bismuthinite has the same relations to 
the gangue as the copper pitch. Azurite, malachite, 
and a clay mineral that is probably beidellite occur 
in small quantities. Tungsten minerals and gold are 
reported also to be present. This vein is not per- 
sistent downward, 

A few hundred feet east of these two veins a similar 
vein is exposed. This strikes N. 10° W. and dips 
45° E. and is about 3 feet in width. Near the bottom 
of the shaft the vein is displaced about 2 feet by a 
westward-dipping normal fault. The vein filling con- 
sists chiefly of tourmaline and quartz, in which are 
local concentrations of muscovite. Unreplaced rem- 
nants of the bleached and altered quartz monzonite 
that forms the walls also occur within the vein. In 



this gangue are found patches of the ore minerals. 
Those observed include pyrite, chalcopyrite, tetra- 
hedrite, and gold. Oxidation products are chalcocite, 
covellite, copper pitch, malachite, azurite, bismutite, 
and a dark-gray copper-bismuth mineral that is 
probably a very intimate mixture of bismutite and 
chrysocolla. Specimens rich in these ore minerals are 
reported to assay as high as 60 ounces to the ton in 
silver and $20 to the ton in gold. 

Still farther east, about 500 feet south of the old 
Keno shaft, a fourth ore body has been prospected. This 
has a pipelike form, in contrast to the other deposits, 
and pitches steeply to the southeast. It is mineralogi- 
cally similar to the vein deposits except that sulphide 
minerals are somewhat less abundant and that apatite 
and scheelite are both present, locally in considerable 
quantity. Apatite was found both as small cream- 
colored crystals and as large greenish masses that had 
replaced the tourmaline. Scheelite occurs as large 
greasy-appearing grayish crystals partly replaced by 
tourmaline. Bismuth minerals are reported to occur 
in this deposit, but none were recognized in the sped-* 
mens collected. 



VICTORY sro. 1 



The Victory No. 1 claim, owned by the Hudsons, 
of Gold Hill, is about 1,500 feet southeast of the road 
fork at an altitude of 5,783 feet on the Lincoln High- 
way south of the town of Gold Hill. Several surface 
workings have been opened on the claim, but so far as 
known no ore has been shipped. 

The claim is near the contact of a broad tongue of 
quartz monzonite from the main stock, with limestone 
and dolomite of the Oquirrh formation. The sedi- 
mentary rocks have been locally replaced by jasperoid. 
The ore body is a vein that strikes about N. 50° W. 
and dips vertically within the quartz monzonite, but 
at its intersection with the sedimentary rocks it changes 
its course to follow the contact. Quartz and black 
tourmaline with some cream-colored apatite are the 
most plentiful gangue minerals. Pyrite, chalcopyrite, 
and tetrahedrite occur in blebs and patches through- 
out the rock; the pyrite and chalcopyrite are more 
abundant in the tourmaline, and the tetrahedrite is 
localized in the quartz. "Limonite," azurite, mala- 
chite, chalcocite, and chrysocolla are oxidation prod- 
ucts. No assays of the ore are available, but it is 
certain that the average grade is low. 

MINNEHAHA 

The Minnehaha group of 13 claims lies along 
Goshute Wash about a mile east of Montezuma Peak. 
The claims, of which three are patented, are owned 
by P. H. Robinson, of Gold Hill. Mr. Bobinson 
reports that small shipments of ore were made from 
one of the patented claims, the Albert, in 1912 and 
1925. These contained $1.60 in gold and 6 or 7 ounces 
of silver to the ton and from 5 to 16 percent of copper. 



128 



GOLD HILL MINING DISTRICT, tJTAH 



The claims cover a considerable distance along the 
contact between the quartz monzonite and the Oquirrh 
formation. The contact in this region dips to the 
east-southeast at a moderately low angle. The 
Oquirrh formation has been converted to jasperoid 
for as much as 50 feet above the contact. The ore is 
found in the jasperoid in sheetlike layers 5 to 10 feet 
above the contact. Over much of the distance the ore 
zone is essentially barren and consists of jasperoid 
very rich in iron oxides, much of it carrying 20 per- 
cent or more in iron. Locally, however, the material 
is cupriferous, and the most abundant copper mineral 
is a siliceous copper pitch, in which are not uncom- 
monly remnants of ehalcopyrite. Chrysocolla and the 
basic copper carbonates are locally conspicuous but 
are probably unimportant as ore minerals. One speci- 
men from the Albert claim contained considerable 
arsenopyrite, but this mineral was not noted elsewhere. 
There has been considerable post-ore shearing in the 
vicinity, both along the ore horizon and at the under- 
lying contact of the jasperoid with the quartz monzo- 
' nite. 

Another small copper prospect on the group is a 
short distance southwest of Mr. Eobinson's house, 
within a small block of limestone surrounded by quartz 
monzonite. The limestone has been largely converted 
to lime-silicate rock, in which there has been a slight 
copper mineralization similar to that at the Frankie 
mine. 

OZARK 

The Ozark group of claims, about a mile southeast 
of Montezuma Peak, is reported to be owned by F. 
M. Johnson, of Wendover. A shipment of 12 tons of 
ore from this group in 1917 contained 0.11 ounce of 
gold and 5.1 ounces of silver to the ton and 3.2 percent 
of copper. 

In the vicinity of the claims a small triangular plug 
of quartz monzonite, satellitic to the main stock, is 
intrusive into the Oquirrh formation. The sedimen- 
tary rocks here are composed of interbedded thin 
limestones and sandstones. The limestone beds in 
particular have been thoroughly altered in the vicinity 
of the workings, in part to silicate minerals and in part 
to jasperoid. 

Two ore shoots are present on the property, both 
in the sedimentary rocks near the quartz monzonite 
contact. The larger one is a vein striking N. 20° W. 
and dipping 60° E. The hanging wall of the vein is a 
dark porphyry dike and the footwall a mass of jas- 
peroid 25 feet in width. The ore mined contained 
abundant iron oxides and various copper minerals, of 
which copper pitch appears to have been the most 
plentiful. In the more westerly workings on the claim 
scorodite and arsenopyrite appear to be the only ore 
minerals present. 



COPPER HILL 

The Copper Hill group of unpatented claims is on 
the west and southwest side of hill 5852, a little less 
than 2 miles north of west from the town of Gold Hill. 
In 1926 it was owned by J. C. and H. V. Hicks, of 
Salt Lake City. 

The ore shoots are in lime-silicate rock produced by 
the alteration of limestone beds in the Oquirrh for- 
mation. They occur near dikelike masses of quartz 
monzonite that were intruded in part along a north- 
westward-striking fault that brings the Manning 
Canyon formation into contact with the Oquirrh 
formation. The mineralization was rather scanty, 
copper pitch and other oxidized copper minerals being 
found locally in ore shoots of small dimensions. 

ALVABADO 

The Alvarado mine is about 1 mile east of the town 
of Gold Hill and half a mile northwest of the Western 
Utah Copper Co.'s Gold Hill mine. It is now owned 
by the Woodman Estate. The writer was informed 
that difficulty in securing united action by the large 
number of heirs to the estate has prevented recent 
attempts to work the mine. The mine workings con- 
sist of an inclined shaft about 250 feet deep and about 
1,500 feet of tunnels, in addition to short raises and 
winzes (fig. 16). A shaft house and a bunk house, both 
in need of repair, are on the property, which adjoins 
the spur of the railroad to the Western Utah property. 

The bulk of the production from the mine was made 
in the period from 1892 to 1895, during which it is 
supposed to have produced about $120,000 in gold. 
Since that time the mine has been idle for the most 
part, although several small shipments of ore have 
been made. One lot of 25 tons is reported by William 
Darnell to have been shipped in 1909 and another of 
35 tons in 1916. 

Since the field work for this report was completed 
some ore has been extracted froin the mine by lessees. 
Toward the end of 1931 the Aurum Mining Corporation 
was reported to have obtained control of the property. 

Two formations are recognized near the Alvarado 
mine — Ochre Mountain limestone and quartz monzon- 
ite. The thick beds of limestone are generally bleached 
to a dazzling white color and are coarsely crystalline. 
Locally silicate minerals have replaced the limestone; 
the most wide-spread is wollastonite in bladed crys- 
tals as much as an inch in length. One notable expo- 
sure of this mineral was found a short distance south- 
east of the shaft house. The beds strike rather uni- 
formly a little west of north and dip steeply to the 
east. 

The quartz monzonite is not notably different from 
the average for this formation. Biotite appears to 
be the most abundant of the primary dark minerals, 



MINES AND PROSPECTS 



129 



but diopside, partly altered to hornblende, has been 
introduced into the rock in many places. In a spec- 
imen from the east end of the 200-foot level magnetite 




Figure 16, — Plan of Alvarado mine workings. Blank areas are limestone. 

and smoky apatite are unusually abundant sw. 
accessory minerals and quartz is relatively rare. 
Calcite and pyrite are secondary minerals in 
this plaeej as in several others. 

The quartz monzonite is a part of the main 
stock, and its contact with the limestone beds, 
about 150 feet southwest of the shaft, is 
approximately parallel with their strike. This 
contact is also exposed on the 100-foot level, 
where the dip is steep to the northeast. A 
dike from the main body about 20 feet wide 
is also exposed at the surface. At the shaft 
the dike has a course that is approximately 
the same as that of the bedding and dips 
steeply to the northeast. It does not extend 
to the northwest much beyond the mine work- 
ings but may be traced with the same strike 
about 200 feet to the southeast. There the 
strike swings sharply to the south, and the 
width increases rapidly until a junction with 
the main body of the stock is effected. 

Underground the dike is found to have some 
minor irregularities. On the 40- and 60-foot 
levels, for example, it cuts across the bedding 
of the limestone at a low angle, thereby terminating 
the main ore body. On the 100-foot level irregularities 
also appear. The hanging-wall crosscut just south of 



the shaft shows a minimum thickness of 60 feet for 
the dike, although only 20 feet was found at the 
surface. Further, near the shaft the contact of lime- 
stone and quartz monzonite on the 100-foot 
level is almost vertically beneath the contact 
on the 60-foot level, indicating that here the 
dike transgresses the dip of the beds. Finally, 
at the south end of the 100-foot level, a hang- 
ing-wall crosscut discloses 25 feet of limestone 
between walls of quartz monzonite. These 
features indicate that the dike branches at this 
altitude near the shaft, and that the south- 
westerly branch is a spur that extends upward 
so short a distance that it is not exposed on the 
60-foot level (fig. 17). The block of limestone 
between the two branches apparently reaches 
a greater depth to the south than it does near 
the shaft. 

The 200-foot level adds little to the knowl- 
edge of the dike except that its dip must flatten 
notably below the 150-foot level . The extension 
of the shaft below the 200-foot level, however, 
again cuts quartz monzonite and strongly sug- 
gests a reversal of dip, as shown in the section. 
The bottom level also shows three other 
exposures of quartz monzonite in the work- 
ings northwest of the shaft. All of these 
are rather irregular lenticular masses with 
relatively small cross sections. The lime- 




100 Feet 



Figure 17. — Oeologic cross section through Alvarado shaft. 

stones surrounding these masses have undergone a 
rather extensive replacement by silica. Much of this 
is in the form of fine-grained quartz that has veined 



130 



GOLD HILL MINING DISTRICT, UTAH 



or irregularly replaced the calcite, but locally thin 
lenses of chalcedony, which are bordered by quartz, 
are present. In many places the altered rock is col- 
ored a deep brown by specks of a finely disseminated 
mineral of that color. The several exposures of quartz 
monzonite on this level and the abundant silicification, 
together with the apparent reversal of dip of the dike 
indicated by the presence of the igneous rock in the 
bottom of the shaft, lead the writer to the belief that 
the limestone will be bottomed at no great distance 
below the level. 

The ore bodies of the mine consist of irregular shoots, 
carrying a minable amount of gold in limestone that 
has been almost completely replaced by silicate min- 
erals. Two chief ore bodies have been exploited. 

One, which may be called the main ore body, is 
much larger than the other, here designated the foot- 

SE. 



NW. 




IOO Feet 



Figure 18, — Stops projection on plane through shaft, Alvarado mini 

wall ore body. (See fig. 18.) It has been followed 
from the surface down to the 200-foot level and has 
been stoped over a width as great as 40 feet, with an 
average between 5 and 10 feet. The stope length 
reaches a maximum of about 120 feet on the 60-foot 
level and decreases considerably on the lower levels. 
The dike of quartz monzonite forms the hanging wall 
of this deposit almost throughout its extent, except 
for the portion below the 150-foot level, where lime- 
stone forms both walls. In this region the tabular 
form of the ore body is replaced by a roughly pipe- 
like or cylindrical shape. On the upper levels the 
stopes indicate a pitch to the northwest. This may 
be the result, at least on the 60-foot level, of the trans- 
gression of the limestone bedding by the dike. West- 



ward-dipping cross fractures, however, may also have 
influenced the pitch. The division of the ore body 
into two parts below the 60-foot level also appears to 
be the result of the position of the dike, as the unstoped 
region corresponds in position with the junction of the 
two branches of the dike that has interrupted the ore- 
bearing bed. 

The footwall ore body is comparatively small and 
was stoped only from the 60-foot level to a point a 
few feet above the 40-foot level. Its maximum stope 
length was about 30 feet. The northwestern part of 
this shoot had the dike of quartz monzonite for a hang- 
ing wall, but the remainder had limestone on both 
walls. A minor amount of stoping was done on the 
60-foot level along the limestone and quartz monzonite 
contact in a way to connect the two ore bodies. It 
could not be ascertained, however, whether the mate- 
rial removed contained gold or whether 
the work was done in the expectation 
that the ore should be found along the 
contact. 

In addition to these two main ore 
bodies there appear to have been several 
pipes of ore on the 200-foot level, for 
moderate amounts of stoping have been 
done from the several winzes and raises 
shown on the map. One of these pipes 
is entirely within a lenticular mass of 
quartz monzonite. The remainder are 
in the limestone. 

A notable feature of most of the stoped 
areas is the general presence of cross 
fractures, striking somewhat east of 
north and dipping steeply, for the most 
part to the west. These are locally filled 
with wollastonite and other silicates, 
quartz, which is in part chalcedony, and 
oxidized iron and copper minerals. In 
most places the stope width appeared to 
reach a maximum where these cross frac- 
tures were intercepted. Similar frac- 
tures were found in the pipelike bodies on the 200-foot 
level. The writer feels that they have played a much 
more important part in localizing the ore shoots than 
the presence of the dike of quartz monzonite, for, as 
noted in a previous paragraph, most of the pipelike 
ore bodies and some parts of the tabular bodies may 
be found within walls of limestone. 

Where quartz monzonite forms the hanging wall of 
the ore body the line between ore and waste is sharp 
and is found at the igneous contact. The limestone 
walls, however, are not sharp and appear to have been 
determined by assay, rather than by any obvious 
mineralogic change, for silicate replacement of lime- 
stone extended far beyond the limits that have been 
reached by the stoping. 



MINES AND PBOSPECTS 



131 



The greater part of the ore mined consisted of sili- 
cate minerals that had replaced limestone, with which 
were associated considerable amounts of quartz, small 
amounts of sulphide minerals with their oxidation 
products, and native gold. The most widespread 
silicate mineral appears to be wollastonite, which in 
many places has been largely replaced by fine-grained 
fibrous spadaite. This alteration resulted in a massive, 
almost porcelaneous rock of a cream or pale-pink color. 
Smaller amounts of green diopside and brown garnet 
are also abundant, and Kemp 86 in addition mentions 
zoisite, vesuvianite, tremolite, and serpentine. The 
relations between the tremolite and serpentine as 
described by Kemp are similar to those noted between 
wollastonite and spadaite. 

The silicate minerals have been replaced or cut by 
irregular areas or veinlets of quartz. Both mega- 
scopically crystalline and very fine-grained quartz have 
been recognized, and the latter is the younger. In 
addition, chalcedony is s of frequent occurrence, but 
it seems in most places to be the result of weathering. 
Calcite veinlets of several ages with respect to the 
quartz are also abundant. 

The sulphides recognized are pyrite, galena, ehalco- 
pyrite, bornite, and chalcocite. They are relatively 
rare in this mine but have been found both in the sili- 
cate rock and quartz veins. The occurrences in asso- 
ciation with quartz are the more abundant. The 
most striking occurrence of sulphides is on the 200-foot 
level just south of the shaft. This exposure is not on 
either of the two chief ore bodies, and as it has not 
been stoped, presumably it is not rich in gold. This 
body has been thoroughly oxidized and now consists 
of brown resinous copper pitch with a few remnants 
of sulphides, which shows local alteration to iron oxides, 
a lighter-brown jarosite, blue crystalline chalcanthite, 
and a pale-greenish mineral that has the optic proper- 
ties of siderotil, a hydrous iron sulphate. 

Native gold is said to have been locally very abun- 
dant and to have been found in pieces "as large as a 
bean." William Darnell, who has worked in the mine, 
says that it was especially abundant in the spadaite 
areas, particularly where that mineral contained cop- 
per minerals or quartz veinlets. No gold was col- 
lected in the mine by the writer, but in specimens 
which he has seen the native gold is crystalline and is 
associated with oxidized copper and iron minerals and 
with chalcedony. The enclosing rock in these speci- 
mens was quartz and spadaite. Kemp" described 
native gold from this mine associated with zoisite, 
limonite, and malachite. 

In the pipelike ore bodies on the 200-foot level the 
silicate minerals appear to be much less abundant. 
Small quantities of diopside and a very fine-grained 
mineral that is probably spadaite were recognized in 



* Kemp, I. F., Notes on Gold Hill and vicinity, Tooele County, Utah: Econ. 
Geology, to]. 13, pp. 258-269, 1918. 
« Kemp, J. V., op. cit., pp. 268-259. 



the thin section studied, but the bulk of the rock is 
composed of calcite replaced by fine-grained quartz. 
No sulphides were noted in these pipes. Oxidation 
products are much more abundant near the ore bodies 
on this level than elsewhere, perhaps because of the 
greater abundance of easily replaced calcite. 

The grade of the ore is reported to have been rather 
variable. No figures are available for the Alvarado 
mine alone. An examination of the assay records of 
the mill that treated ore from the Alvarado, Cane 
Springs, and Gold Hill mines, showed that the heads 
assayed from $4 to $35 a ton, of which about 80 per- 
cent was recovered. The average content during a 
period of slightly less than two years was $10.28 a ton. 
Bullion assays indicated a fineness of 0.750 to 0.850. 
Some of the gold, however, is reported to have been 
0.950 fine. 

CANB SPRINGS 

The Cane Springs mine is about 2,000 feet south- 
west of the town of Gold Hill and 250 feet west of 
U.S. Mineral Monument No. 7, Like the Alvarado, it 
is owned by the Woodman Estate, and similar diffi- 
culties are reported to have been met in attempts to 
reopen the mine. The development consists of an 
inclined shaft 150 feet deep, two short winzes, and 
about 1,000 feet of drifts and crosscuts (fig. 19). A 
vertical shaft connects the most easterly workings with 
the surface but appears to have been little used. 

In 1931 work was resumed at the Cane Springs 
mine by G. H. Short, of Salt Lake City, under a 
3-year lease with an option to purchase the property. 
Toward the end of the year the Aurum Mining Cor- 
poration was organized to operate this lease together 
with one on the Alvarado. Development was actively 
prosecuted, and at the end of 1932 it was reported that 
25 tons of ore a day was being mined, of an average 
grade of about $12 a ton. 

The production of the Cane Springs mine is not 
accurately known. Its period of greatest activity 
appears to have been from 1892 to 1895, when the 
gold production was probably between $50,000 and 
$70,000. A shipment of 46 tons reported from the 
Cane Springs claim in 1914 contained 1.07 ounces of 
gold and 3 ounces of silver to the ton and 5.5 per- 
cent of copper. 

The mine is in a rather narrow northwestward- 
striking belt of Ochre Mountain limestone. This is 
separated from the Oquirrh formation on the south- 
west by a normal fault of rather large throw, whose 
strike cuts that of the limestone at a small angle, with 
the result that individual beds are progressively cut 
out to the northwest, the uppermost one disappearing 
just southeast of the wash in which Cane Spring is 
located. The limestone is overlain by the Manning 
Canyon formation. Two small plugs of quartz rnonzo- 
nite cut the limestone belt, one about 1,000 feet north- 
west of the main shaft and the other, larger one a 
similar distance to the southeast. The main body of 



132 



GOLD HILL MINING DISTBICT, UTAH 



the quartz monzonite stock crops out only a slightly 
greater distance to the east. 

The limestone is similar to that exposed at the 
Alvarado — massively bedded, bleached and recrys- 
tallized, and locally altered to silicate minerals. It 
has a rather constant northwest strike and dips 
55°-65° NE. The Manning Canyon formation above 
is not well exposed but appears to have been rather 
generally metamorphosed to a dark andalusite hornfels. 
The only igneous rocks found in the mine are two 
dikes, each a foot or so thick. These occur along two 
fault planes, one exposed on the third level and the 



passes into either a sheeted zone in metamorphosed 
limestone, as near the portal of the tunnel level, or a 
tight barren fissure within silicate minerals. The 
greatest stope length is on the first or tunnel level 
and amounts to about 125 feet. 

Cross fractures are prominent within the ore shoots. 
These strike nearly east and dip steeply to the south. 
Mineralization similar to that of the ore body has 
occurred along these fractures and extended outward 
into the walls. One such fracture is excellently dis- 
played in the winze connecting the third and fourth 
levels. 



-\V-Ai7' 



EXPLANATION 



Shaeta 

zone 




Approximate contact? 
Ochre Mountain !ime- 
s'mRricAL stone. and Manning 
Canyon formation 



Figure 19— Plan of Cane Springs mine workings. For sections on lines A-A', B-B, and C-C see figure 20. 



other on the fourth level. The dike rock is a dull 
brownish-gray fine-grained rock in which flecks of iron 
oxide are the only constituents readily recognizable. 
The microscope shows that it has been thoroughly 
altered and is now composed chiefly of fibrous pleo- 
chroic hornblende and sericite, together with smaller 
amounts of apatite, chlorite, calcite, and iron oxides. 
There is also a greenish isotropic mineral of high relief 
that is probably spinel. Kectangular areas of sericite 
apparently represent former feldspar phenocrysts. 

The ore body is found in a thick bed of limestone 
that has been almost completely replaced by silicates, 
quartz, and sulphides. The walls appear in large part 
to have been assay walls, and the width stoped ranges 
from about a foot to 20 feet. Laterally the ore shoot 



The continuity of the ore shoot is broken by six or 
seven low-angle faults (figs. 20 and 21). These have 
rather widely different strikes that range from north- 
northeast through east-west to north-northwest, con- 
siderable variations in strike being observed in a single 
fault. They are all alike, however, in having a low 
dip — 25° to 35° — which always has a northerly element 
in its direction. The sections in figures 20 and 21 show 
an apparent gap in the ore above the third level, 
but it seems probable that this was actually stoped, 
for the ore shoot is shown by Billingsley ss to be essen- 
tially continuous through this section. These workings 
if they are present, are probably now concealed by the 



• ! Billingsley, Paul, Notes on Gold Hill and vicinity, Tooele County, Utah: Eeon. 
Geology, vol. 13, p. 272, 1918. 



MINES AND PBOSPECTS 



133 



filling at the bottom of the raise connecting the second 
and third levels. 

The offsets of the ore shoot by the faults are not 
consistent among themselves. Some, particularly 




Third level 
on section A A 



Third level 

on section BB' 



Vein 



^-^ 



^ 




SE. 



Fault 

Figure 20.— Composite section along lines A-A', B-B 1 , and C-C, figure IB, through 
Cane Springs mine. Sections B-B' and C-C have been shifted both vertically 
and horizontally relative to A-A' so that individual faults appear continuous. 

those on the higher levels, require reverse movement 
with a large horizontal component, but others show 
equally large offsets that require the normal type of 
movement, though also with horizontal components. 

These relations of the faults 
suggest that they were formed 
before ore deposition and that 
the apparent displacement of 
the ore by the faults is rather 
the result of a control of ore dep- 
osition by the faults. The rea- 
sons for this view are as follows: 

The two dikes described in a 
preceding paragraph are in- 
truded along the faults and thus 
are clearly younger. The dikes 
are themselves metamorphosed, 
and if it is held that faulting 
followed the deposition of the 
gold ore it becomes necessary to 
assume two periods of silicate 
metamorphism separated by an 
epoch of both reverse and nor- 
mal faulting. This is difficult to accept in view of the 
fact that in other parts of the district mineralization 
has clearly followed dike formation. 



The shapes of the portions of the ore shoot between 
faults offer some evidence. Although it is realized 
that the stoped areas had very different gold contents, 
a rough approximation to similarity in dimensions on 
both sides of a fault might be expected, but figure 21 
shows that such a similarity is not present. Further- 
more the extension of the stopes upward along the 
fault plane, as shown especially well by the stope above 
the end of the second level, suggests very strongly a 
greater age for the fault, which thus dammed and 
directed upward the incoming ore-forming material. 

The apparent displacement of the ore shoots by the 
faults is difficult to accept on the theory that both 
reverse and normal faults, which are roughly parallel 
in attitude, could have formed in the interval between 
ore deposition and dike formation and be unrecognized 
elsewhere in the quadrangle. It is much more proba- 
ble that the ore solutions entered along the closely 
related cross fractures and that .deposition was con- 
trolled by preexisting faults, whose present attitudes 
may be quite different from their original ones. 

The ore is similar to that of the Alvarado and Midas 
mines. Wollastonite, which is locally fibrous, is the 
most abundant silicate mineral and in many places 
has been altered to spadaite. Pinkish-brown garnet, 
green diopside, and greenish-brown vesuvianite and 
zoisite are also found. Fine-grained quartz and calcite 
cut the silicates in veinlets and more irregular masses. 
Sulphides and their oxidation products are relatively 
more abundant in the mine and consist of pyrite, 
chalcopyrite, bornite, chalcocite, covellite, and molyb- 
denite. The molybdenite is reported to have been 
found very plentifully near the surface. These min- 
erals occur in veinlets cutting the silicate minerals. 

NW. 



rr^^^ 





so Feet 



j 



Figure 21.— Stope projection, Cane Springs mine. 

No gold was observed in the specimens collected by 

I the writer. William Darnell, who worked in the mine, 

informed the writer that the best ore was found near 



134 



GOLD HILL MINING DISTRICT, UTAH 



concentrations of copper minerals. Kemp, 59 however, 
has described the occurrence of native gold embedded 
in silicate minerals. 

No data are now available as to the grade of the ores 
other than those quoted in the description of the 
Alvarado mine — namely, that the mill heads, on ore 
from the several mines, ranged from $4 to $35 in gold 
to the ton and the recovery averaged $10.28 a ton 
over a period of 2 years. It is said that the Cane 
Springs ore was somewhat more refractory than that 
from the other mines because of the higher content of 
sulphide minerals. Either for this reason or perhaps 
because of a generally lower grade, the stoping in this 
mine shows that only the most accessible material 
was mined. 

MIDAS 

The Midas mine is on the south side of Montezuma 
Peak, just east of Hopkins Gulch and a little more 
than a mile east-southeast of Mineral Monument 
No. 9. Four patented claims are owned by the Midas 
Gold Mining & Milling Co., of Salt Lake City, Utah. 
The mine developments consist of an adit tunnel in 
which about 1,100 feet of work has been done (fig. 22) 
and several stopes at the surface. It is said that the 
slopes were connected with the tunnel level by means 
of four raises, but it is not now possible to pass from 
one to the other. The tunnel is badly caved in sev- 
eral places. Water draining from it is piped to the 
location indicated by the spring symbol on the map 
and is utilized occasionally to water sheep. The ruins 
of a 40-ton cyanide mill are about 500 feet south of 
the tunnel portal. 

Concerning the production Heikes 80 notes that "in 
1896 and prior to that year 95 tons of ore averaging 
$56 in gold and a trace in silver per ton were treated 
at the Cane Springs mill and shipped to the smelter. 
In 1902 a 40-ton cyanide mill was constructed and 
treated 622 tons with a reported saving of $15 per ton 
in gold. In 1904 the mill was operated again, but the 
results were unfavorable, and the property was prac- 
cally abandoned." 

The operations in 1904 resulted in the recovery of 
somewhat less than $20,000 in gold, and the grade 
appears to have been lower than that of the ore pre- 
viously treated. The total production of the mine is 
about $35,000. So far as known no work has been 
done since. 1904. 

The mine workings are in metamorphosed sedimen- 
tary rocks belonging to the Manning Canyon and 
Oquirrh formations, which are cut by quartz mon- 
zonite. The Manning Canyon formation is exposed 
at the portal of the tunnel and for several hundred 
feet to the south and southwest. It is composed of 



'• Kemp, J. F., Notes on Gold Hill »nd vicinity, Tooele Comity, Utah: Econ- 
Geology, vol. 13, pp, 257-258, 1918. 

«» Heikes, V. C, Ore deposits of Utah: U.S. Geol. Survey Prof. Paper 111, p. 475, 
1920. 



black shale and dark sandy shale and quartzite. Bio- 
tite, andalusite, and tourmaline in microscopic crystals 
are present in many beds. The Oquirrh formation 
overlies the Manning Canyon formation southeast of 
the tunnel portal. North of the tunnel it is in contact 
with quartz monzonite at the surface, but the mine 
workings disclose the Manning Canyon formation be- 
neath it. Sandstone beds form the bulk of the part 
of the formation here exposed. Interbedded with 



Cfc Quartz 








xjL* monzonite 






Mf 






j 1*30* so' 






I c 


Txt* ?0 ' 






fj -CO 


M\ 


^~-£S* 




so* 




RAISE 






*,^ 










25' jj 


_f3K. 


It or 




-fissure 


*>% 








INCLINE 


WfA 






SHAFT 









\WiNZ£ 
Jfu/J of water) 



Sf 



'-.Crashed ~ 
Crashed? j&vp 

A 



*' 



s> 



loo Feet 



Fkhjbe 22.— Plan of tunnel level, Midas mine. 

them are several beds of limestone. Both rocks are 
thoroughly bleached and contain varying amounts of 
silicate minerals, chiefly wollastonite, garnet, and diop- 
side, as the result of metamorphism. 

The beds have a rather general strike west of north 
and dip 30°-45° E. About 1,100 feet south of the 
tunnel portal the succession of beds exposed near the 
mine is terminated by an east-west transverse fault, 
whose throw is somewhat uncertain but appears to be 
more than a mile. Another fault exposed just north 



MINES AND PROSPECTS 



lOD 



of the tunnel portal brings the Manning Canyon for- 
mation on the south into contact with the Oquirrh 
formation on the north. This fault may be traced up 
the hill to the east in a direction north of east until 
the crest is reached, where the course swings to east 
of north. The same fault is exposed in the tunnel 
along the hanging wall of a dike of quartz monzonite. 
Its strike is sinuous but averages a few degrees east 
of north. The dip is about 30° W., and this feature 
appears competent to explain the change in course on 
the surface. The throw is estimated to be about 200 
feet, to judge from the position of the upper Manning 
Canyon contact on the two sides of the fault. The 
west side is down thrown. 

Another fault is exposed in the tunnel at the inte- 
rior inclined shaft. This strikes east of north and 
dips 30°-50° SE. It was not recognized on the sur- 
face. The relation of this fault to the one just de- 
scribed is not clear. It is probably cut by the west- 
ward-dipping fault, because it cannot be connected 
directly with the similar eastward-dipping fault in the 
eastern drift north of the shaft. However, if the two 
are the same, it indicates that there has been only a 
small displacement of a reverse character along the 
the westward-dipping fault, which directly opposes 
the stratigraphic evidence. On the other hand, the 
westward-dipping fault cannot be recognized to the 
north, either in the two drifts or in the crosscut connec- 
ting them. The writer suspects that the true relations 
between the two faults are that the eastward-dipping 
fault is younger than the bulk of the movement along 
the westward-dipping fault, but that there has been 
a slight renewed movement along the latter (for which 
there is some evidence, as noted below). 

The quartz monzonite near the mine is at the south- 
eastern tip of the triangular outcrop of this rock on the 
south side of Montezuma Peak. The contact at the 
mine trends roughly north and south but is irregular 
in detail. It is exposed underground near the north 
end of the tunnel workings and there dips 70° E. 
South of the tunnel a broad hook-shaped mass of the 
intrusive extends into the sedimentary rocks. An 
isolated mass of quartz monzonite crops out along the 
ridge east of the mine workings. On the surface its 
shape is that of a flattened triangle, whose base has a 
north-south direction and whose northwestern limb is 
the westward-dipping fault previously described. This 
mass is also exposed in several , places in the tunnel, 
where the fault everywhere forms its hanging wall. 
To the north it apparently has a dikelike form, but to 
the south its lower boundary seems to be very irregu- 
lar. (See fig, 22,) There has been some movement 
along the boundary fault after the emplacement of the 
quartz monzonite, as can be seen from the gouge along 
the fault, but the lack of displacement at the contact 
of the fault and the intrusive rock on the surface indi- 
cates that this movement must have been very small — 



far less than the 200-foot throw shown by the sedi- 
mentary rocks. Furthermore, at several other places 
in this region the quartz monzonite has utilized pre- 
existent faults of similar strike and dip to this one dur- 
ing its intrusion. The evidence available therefore 
suggests strongly that the greater part of the movement 
along this fault preceded the intrusion. 

The ore at the Midas mine was found in a bed of 
limestone that has been almost completely replaced 
by silicate minerals. The limestone is interbedded 
with the predominantly sandy beds that here make up 
the Oquirrh formation. The ore body in this bed is 
in the exposure of this formation on the hanging- 
wall side of the westward-dipping fault and cropped 
out on the east side of the gulch in which the tunnel 
is located, the contact with the main mass of monzonite 
being on the west side. The ore body had an average 
thickness of about 4 feet and was found in shoots for 
several hundred feet along the strike of the bed, A 
vertical depth of about 100 feet seems to have been the 
limit of the ore body, for it is not exposed on the tunnel 
level. Locally it is said that it was terminated above 
the level by a fault on whose footwall was found 
"granite", and it seems probable that the fault on the 
tunnel level is the one that terminated the ore. It 
was not possible, however, to examine the bottoms of 
the stopes to ascertain if this view is correct. If it 
is, it would appear that the reported effort to discover 
the faulted portion of the ore bed was foredoomed to 
failure, for, as shown above, the faulting preceded the 
intrusion of the quartz monzonite, which in turn is 
older than the ore. It would probably be more profit- 
able to search for a new ore body in one of the limestone 
beds in the hanging wall of the fault. 

The ore, like that of the Alvarado and- Cane Springs 
mines, was composed chiefly of wollastonite, in part 
altered to spadaite, and less abundant diopside and 
garnet. Butler 61 also reports vesuvianite. Sulphides 
are not abundant and consist of pyrite and various 
sulphides of copper. Butler notes in addition arsen- 
opyrite. No free gold was observed by the writer. 
The grade of the ore appears to have been somewhat 
higher than the average in the Alvarado and Cane 
Springs mines. 



BONNBMOBT 



The Bonnemort claim is about 2,000 feet southeast 
of the U.S. mine and adjoins the Undine group on the 
northwest. It is owned by the Woodman Estate. 
Gold ore is reported to have been mined some years 
ago from the inclined shaft 350 feet west of hill 5001, 
but the amount and grade are unknown. The shaft is 
now considerably out of repair. 

The country rock consists of sandstone and lime- 
stone belonging to the Oquirrh formation. These 



« Butler, B. 8., Ore deposits of Utah: U.S. Oeol. Survey Prof. Paper 111, p. 47B, 
1920. 



136 



GOLD HILL MINING DISTRICT, UTAH 



rocks make up the south end of the roof pendant of 
sedimentary rocks in which the U.S. mine is located. 
The sediments in the vicinity of the ore body are al- 
most completely bleached and reerystallized, and many 
of the limestone beds have been altered to silicate 
minerals. In addition to the quartz monzonite on 
each side of the roof pendant, a dike of this rock occurs 
about 25 feet west of the inclined shaft. It strikes 
nearly due north over most of the exposure, but at 
the thicker south end it changes its strike abruptly to 
nearly due east. The portion of the dike with this 
strike does not extend far beyond the bend. 

The ore body appears to be similar in several respects 
to that of the Cane Springs and Alvarado mines, but 
the inaccessibility of the workings prevents any close 
comparison. A bed of limestone more or less replaced 
by silicates was mined. This bed strikes N. 5° W. and 
dips 60° E. Gold is said to have occurred in thin 
seams "within the bed as well as being disseminated 
through it. Factors such as cross fractures that may 
have localized the ore shoot could not be certainly 
recognized at the surface. 

Specimens from the dump that were said to resemble 
the ore consisted of coarsely crystalline white calcite 
in which were scattered abundant laths of wollastonite 
or of dense greenish diopside. Brown zoisite was ob- 
served in a few specimens. Specks and patches of 
chalcocite and copper pitch with remnants of chal- 
copyrite were rather abundant in some specimens. 
Spadaite, which is so wide-spread at the Cane Springs, 
Alvarado, and Midas mines, was not recognized. 



The Bube mine, formerly owned by Leffler Palmer, 
of Gold Hill, is 1 % miles northeast of the town on the 
southeast side of Gold HOI Wash. The mine, which 
produces a high-grade direct-smelting gold ore, in 1927 
was developed by a 150-foot inclined shaft from which 
two levels have been driven, in addition to a group of 
shallow workings east of the shaft. A small compres- 
sor and hoist engine were utilized. From April 1921 to 
July 1927, 22 shipments of gold ore that averaged more 
than 7 ounces of gold to the ton had been made. 

In May 1932 the mine was sold to the Gold Hill 
Mines, Inc., and since then it has been actively worked. 
At the end of 1932 it was reported that 2 cars of ore 
a week were being shipped, the grade of which ranged 
from $12 to $30 a ton. 

The wall rock shown by the mine workings is a white, 
massively bedded, finely crystalline limestone or dol- 
omite, locally shattered and iron-stained. It is 
thought to be a portion of the Ochre Mountain lime- 
stone that is in part dolomitized. Comparatively little 
alteration to silicate minerals has occurred. The 
strike and dip of the bedding is difficult to determine. 
From several exposures the strike is rather confidently 



thought to be northwest and the dip is with consider- 
ably less assurance considered to be steep to the north- 
east. 

About a quarter of a mile north of the shaft Prospect 
Mountain quartzite crops out with a nearly east-west 
strike and a moderate northerly dip. The contact 
between the quartzite and the Ochre Mountain lime- 
stone is a fault, the movement along which is thought 
to have been chiefly horizontal. The fault is cut and 
displaced by a later fault, which probably extends 
through the eastern part of the Rube No. 3 claim, 
although it is possible, as noted on page 80, that the 
offset is due to a northerly fault following Gold Hill 
Wash and concealed by the gravel in the floor of the 
wash; 

Quartz monzonite crops out at the surface about 
1,000 feet west of the shaft and at an equal distance 
to the south, but none has been found in the under- 
ground work. The outcrop west of the shaft is at 
the eastern edge of the body of igneous rock along the 
south side of Dutch Mountain; the other is at the 
north end of the main stock. 

The only igneous rock found in the underground 
workings is a thin dike of hornblende andesite that 
forms the hanging wall of the ore bodies. This rock 
in most of the exposures is a dull brownish-gray rock 
composed of a paler fine-grained indeterminate matrix 
flecked with numerous areas of "limonite." It effer- 
vesces briskly with dilute hydrochloric acid, not only 
in the numerous veinlets of calcite that streak the rock 
but also in the matrix. At the bottom of the winze 
from the lower level of the western workings much 
fresher material is found. This is a fine-grained gray- 
ish-green rock of pepper and salt appearance. It is 
much jointed, with some calcite filling the joints, but 
the microscope shows that the hornblende and plagio- 
clase that are the original minerals have been relatively 
little altered. The rock found on the upper levels, on 
the other hand, has been almost completely replaced 
by calcite. 

The dike ranges in thickness from a few inches to 
5 feet and has an average though variable strike of 
about east-west and dip of about 60° N. The hanging 
wall is generally a slickensided surface and the contact 
with the footwall sulphide-bearing dolomite is in many 
places a thin crushed zone or joint plane. Locally the 
andesite shows a faint banding parallel to these walls, 
but in other places small apophyses into the walls may 
be found. 

Two small faults cut and offset the dike a few feet 
at the foot of the main shaft, and a third fault appears 
to terminate it about 110 feet east of the shaft on this 
level. The offsets along the two other faults and the 
presence of the dike in the eastern shallow workings 
indicate that the easterly continuation should be found 
south of the present workings. 



MINES AND PBOSPECTS 



137 



The ore occurs chiefly In two pipelike shoots, known 
as the east and west ore bodies (figs. 23 and 24). The 
hanging wall of both these ore shoots is the hornblende 
andesite dike. The contact of the ore with the dike is 



in the eastern workings, a little ore has been found in 
the hanging wall of the dike. 

The east ore body was the first to be discovered. 
The cross-sectional dimensions of this pipe average 



Limestone with 
abundant pyrite 



Crushing and silicification: 
no value 




Pronounced 
sheeting 



#0.2 INCLINE 



Figurk 23,— Plan of mine workings, Hube mine. From map furnished by Leffler Palmer. 



E. 



W. 




EAST DRIFT 



k 


k 


->, 


ci 


<> 


o 


<o 


v> 


in 


in 


r> 


o 


0- 


?" 


o 


o 


ar 


> 




K 


!* 


C» 


u 


11 


< 


<0 



r\ is 



\ \ 
\ 






X ^% 



25 

1-I....J... ) .. I -I „ 



100 Feet 




Fioobi 24. — Longitudinal section through Bube mine. Famished by Leffler Palmer. 



sharp. Sulphide-bearing dolomite forms the footwall 
of the ore bodies, and there is generally an abrupt 
contact between the two. Locally, as near the surface 

35311-35 10 



close to 3 feet in a direction normal to the andesite 
hanging wall and 15 feet parallel to it. The shoot 
rakes 35° W. and has been followed for a distance of 



138 



GOLD HILL MINING DISTEICT, UTAH 



135 feet along the rake. The new or west shoot is 
somewhat larger in cross section than the eastern one 
and also extends to a greater depth, having been stoped 
for a distance of 230 feet down the rake, which averages 
about 45°. On the bottom level the rake is locally 
extremely variable, being 90° at the level and flatten- 
ing to about 30° in the winze below. It is probably 
a coincidence that the flatter portion if projected 
upward would join the east ore body. Ore of good 
grade was still present in the lowest workings in 1927. 

The hanging wall of the ore bodies is marked by a 
pronounced sheeted zone which in the western ore 
body strikes northwest and dips 60°^80° SW. Similar 
directions are shown by thin bands of sulphides in the 
footwall dolomites. The constant association of the 
sheeting and ore probably has a genetic significance, 
but there are several places where apparently similar 
jointing is not accompanied by a concentration of gold. 

Northeast of the eastern workings there is a promi- 
nent outcrop of brecciated dolomite with quartz. This, 
like the main ore zone, has an approximate east-west 
strike. Both might be considered to have been formed 
at about the same time as the large transverse fault 
farther north and to represent sympathetic fractures. 

The ore mined has several different facies. The 
most abundant variety so far has been a brownish 
fine-grained rock of siliceous appearance but having a 
notable content of calcite, as shown by its effervescence 
with dilute acid. Pseudomorphs of "limonite" after 
pyrite and of anglesite and cerusite after galena and 
veinlets of cerusite are abundant, and locally unaltered 
galena may be seen. Native gold in small partly 
crystalline aggregates is found in the iron and lead 
oxidation minerals and in one specimen was super- 
posed on a "limonitic" coating. In a specimen of a 
heavy grayish-green fine-grained rock from the east 
ore body pyromorphite and plumbojarosite cemented 
by supergene quartz were found. 

In thin sections quartz and calcite are found to be 
the most abundant minerals. The quartz grains are 
full of calcite inclusions and in most places contain 
numerous liquid , inclusions, each with a tiny gas 
bubble. Calcite also occurs in larger grains and as 
veinlets cutting the rock. Its cleavages are usually 
deeply iron-stained. In a specimen of very rich ore 
from the east ore body sericite was abundant and was 
veined by anglesite and cerusite, as well as calcite. In 
this specimen the native gold was localized in the 
anglesite. 

Ore of this type is seen to pass, in the lower portion 
of the western workings, into much less oxidized mate- 
rial. This is a blue-gray fine-grained rock locally 
splotched by brown oxidation products that in places 
shows a faint banding. Galena and less abundant 
pyrite are only partly altered, and locally native gold 
may be found either in galena or in the matrix, 
although most of it occurs in the supergene minerals. 



The banding is shown by the microscope to be due 
to varying proportions of calcite and quartz, which 
still form the bulk of the rock. Veinlets of coarser- 
grained clear calcite are abundant and in some places 
are closely associated with the gold and sulphides. In 
other places, however, the metallic minerals are with- 
out visible relation to the veinlets and appear as 
isolated areas in the matrix, surrounded by a rim of 
coarser-grained and clear calcite. 

A third type of ore was found in the western ore 
body just above the second level, in the position 
marked "sulphide ore" on figure 24. The hanging- 
wall portion of this ore is composed chiefly of shattered 
crystalline pyrite that is cut by quartz and calcite 
veinlets containing small amounts of galena, ehal- 
copyrite, and sphalerite. The remainder of this ore 
contains abundant molybdenite with some pyrite in a 
greenish or black fine-grained matrix, which the 
microscope shows to be composed of calcite, talc, 
slightly pleochroic muscovite, scapolite near meionite, 
zoisite, and two varieties of chlorite. This facies of 
the Rube ore appears to offer a sort of connecting link 
with the gold ore of the Alvarado, Midas, and Cane 
Springs mines. 

Sulphide minerals are present in the footwall lime- 
stone or dolomite of the ore bodies. They are asso- 
ciated with relatively small quantities of quartz and 
sericite and locally contain some gold, although not 
enough to warrant mining at the time of examination. 
The metallic minerals recognized in the two specimens 
of this rock studied under the microscope include 
native gold, pyrite, pyrrhotite, deep-red and colorless 
sphalerite, galena, and arsenical boulangerite. Sphal- 
erite is by far the most abundant. 

The grade of the ore mined varies from place to 
place in the stopes> x The carloads shipped up to June 
1927 ranged in gold content from 2.83 to 24.42 ounces 
to the ton and avera^d over 7 ounces. The silver 
content is generally lower and is roughly proportional 
to the lead content, ranging from 2 to 3 ounces to the 
ton for each percent of Wad. One shipment from the 
east ore body carried mojre than 6 percent of arsenic. 
The presence of antimony and small quantities of 
bismuth and tellurium in the ore has been proved by 
analysis. One picked specimen, which the writer did 
not see, is reported by Mr. Palmer to have contained 
7 percent of bismuth. 

WILSON CONSOLIDATED 

The Wilson Consolidated mine is on the northeast 
side of Clifton Flat, about 2,500 feet south-southwest 
of the prominent jasperoid hill at an altitude of 6,455 
feet north of the road to Clifton and immediately 
west of hill 6266. The headquarters of the company 
is in Salt Lake City. Production from the property 
appears to be confined to several small shipments of 
high-grade ore in 1914 and 1917. Relatively little 



MINES AND PROSPECTS 



m 



work has been done since 1917. The mine workings 
aggregate less than 500 feet, chiefly in the form of 
crosscuts and shallow winzes. The vertical range of 
the workings is about 75 feet (fig. 25). 

The rocks exposed in the mine workings are meta- 
morphosed sandstones and limestones belonging to 
the central facies of the Oquirrh formation. About 
200 feet west of the portal of the tunnel these beds are 
separated from limestones thought to belong to the 
western facies of the same formation by a normal 
fault of unknown but probably considerable throw. 
The most pronounced effect of the metamorphism 
upon the sediments of the central facies is a nearly 



dip in the region southeast of the mine, however, is to 
the east, and it is thought that the westward dip may 
be a local feature peculiar to the zone bordering the 
large fault immediately to the west. Igneous rocks 
are almost lacking in the immediate vicinity of the 
mine. A dike of volcanic breccia was observed about 
50 feet from the portal of the adit. This is thoroughly 
crushed and much altered, chiefly to chlorite with 
minor amounts of a clay mineral. Locally the tex- 
ture has been preserved in some of the rock fragments, 
and there is little doubt that the dike is related to the 
outcrops of volcanic rocks that occur along the borders 
of Clifton Flat in this region. 




-4p^3£.£*s: 



PLAN 



50 O 

l ' ' ' l i 



250 Feat 



Figtoe 26.— Sketch plan and section of Wilson Consolidated mine. 



complete bleaching to white or pale cream color. 
There has also been a marked niineralogic change in 
many of the rocks, and the resulting hornfels is in 
many places difficult to distinguish from bleached 
quartzite. In the two specimens of hornfels examined 
under the microscope diopside and orthoclase had been 
abundantly developed. Bedding can be distinguished 
with difficulty in this series, owing in part to the meta- 
morphism and in part to the widespread shattering. 
So far as observed the bedding strikes a little west of 
north and dips about 30°-40° W. The prevailing 



The bismuth-gold ore is found in what is locally 
known as a vein but what appears to be nothing more 
than a bed of coarsely crystalline bleached limestone, 
like the barren wall rocks, it dips about 30° W. The 
contacts of the bed are sharp but show no signs of 
movement or replacement . The limestone has a maxi- 
mum thickness of 6 feet at the south end of the drift 
on the tunnel level but is usually nearer 3 feet in thick- 
ness. The ore-bearing bed is cut by at least nine 
north-south normal faults. These dip 30°-70° E. and 
all have throws of less than 50 feet. Of the two faults 



140 



GOLD HILL MINING DISTBICT, UTAH 



that are shown in the tunnel level, the throw along the 
more easterly appears to be negligible and that along 
the more westerly to be about 25 feet. The throw 
along the fault that cuts off the limestone in the winze 
connecting the tunnel and middle level must be about 
15 or 20 feet, as the three small faults exposed on the 
middle level displace the ore zone as it is exposed in 
the raise from the south drift on this level scarcely 
more than a foot apiece. The throw along the fault 
that terminates the ore at the bottom of the winze 
leading to the bottom level is easily determined as 
being close to 15 feet by reason of the exposure of the 
faulted segment in the crosscut to the west. This 
exposure of the ore zone is also cut by a fault striking 
north of west and dipping steeply to the south. The 
throw along it is about 5 feet. Both the fault and the 
ore zone are cut off a short distance to the west by 
another north-south fault dipping 45° E. The throw 
along this fault as well as along another a short dis- 
tance to the west that has a similar strike but dips 
70° E. is somewhat uncertain. If the southward-dip- 
ping fault which is exposed to the west of the more 
westerly of these two faults and which is cut off by it 
is the same as the fault of similar dip to the east, the 
combined throw along the two faults amounts to about 
25 feet. On the other hand, the ore zone is reported 
to be reached in the shaft at a depth of 30 feet from 
the surface, and no faults were recognized between the 
shaft and the faults in question — facts which require 
a combined throw of about 50 feet. This figure is 
perhaps the closer to the truth, because to correlate 
the two southward-dipping faults would require hori- 
zontal movement along either or both of the north- 
south faults, and if this were admitted, the divergent 
figures for the vertical displacement could be readily 
explained. 

The ore contains gold, bismuth, and a little tungsten. 
The chief gangue mineral is quartz, which is present 
either as euhedral crystals 1 millimeter or less in diam- 
eter, distributed through the limestone, or as veinlets 
of very fine grained allotriomorphic material. In one 
specimen from the south drift on the tunnel level the 
limestone is also cut by veinlets of orthoclase. This 
mineral was not found in any of the other ore speci- 
mens, however. 

The ore minerals observed were native bismuth, 
bismuthinite, bismutite, and scheelite. Copper sul- 
phides and a lead-tungsten mineral, probably stolzite, 
are also reported from this mine by Butler. 62 Bismu- 
thinite and its oxidation product, bismutite, are by far 
the most abundant. The sulphide is found as rounded 
specks as much as a quarter of an inch in diameter em- 
bedded in the limestone. Much of the bismutite forms 
pseudomorphs after bismuthinite, as is shown by the 
preservation of cleavage lines, but a moderate amount 



» Butler, B. S., Ore deposits of Utah: U.S. Geo]. Survey Prof. Paper 111, p 482, 
1920. 



is clearly transported, for it is found also in veinlets of 
supergene opal and chalcedony and along cleavage 
planes of the calcite matrix. Native bismuth was 
found in only one specimen, which was taken from 
the stope leading to the surface from the east end 
of the tunnel level. The mineral was found in the 
center of a grain of bismuthinite. Scheelite was also 
recognized in only one specimen, which was taken from 
the open cut about 50 feet south of the stope to the 
surface. Its occurrence is similar to that of the bis- 
muthinite. Scheelite is reported to have been rather 
abundant in the raise from the south drift on the 
middle level. Native gold also occurs in the ores, but 
none was found in the specimens collected. The two 
stoped areas were mined chiefly for their gold content. 
Butler 63 notes that the gold is closely associated with 
bismuthinite, and in one of his specimens the writer 
observed gold adjacent to several copper minerals. 

The grade of the ore is variable. The distribution 
of gold and scheelite is apparently limited to rather 
small shoots in the vein. No figures are available as 
to the grade of the scheelite-rich portions, but the 
shoots of gold ore seem to have averaged somewhat 
less than 1 ounce to the ton. Bismuth minerals, 
however, are rather widely distributed throughout the 
ore zone, although the amount is far from being con- 
stant. The only figures as to grade that are available 
apply to a shipment of 4.33 tons of concentrates that 
contained 12.43 percent of bismuth. This lot presum- 
ably came from the stope from the surface to the 
tunnel level. It contained about $9 a ton in gold. 
These figures are probably considerably higher than 
the average of the vein. 

VEDTS COSTAIHING CHIBTI* OUABTZ AND 
M1TALUC SUIPHIB1S 

LUCY L 

The Lucy L mine is in Lucy L Gulch about 2 miles 
south-southeast of the town of Gold Hill. It includes 
a group of seven patented claims that are owned by 
the Lucy L Mining Co. The Wilson Brothers, of Salt 
Lake City, have directed the past operations of the 
company. Exploration of the gold-quartz ore body 
had been effected prior to Kemp's visit in 1908, and 
the tungsten deposit on the property was being devel- 
oped at the time of Butler's examination in 1912. 
The property was idle during the period of the writer's 
field work. It is developed by about 1,300 feet of 
workings from two adits (pi. 13), in addition to several 
shallow surface pits. No figures are available as to 
the production, but it is believed that a few small lots 
of gold ore and possibly one or more of tungsten ore 
have been shipped. 

The most prominent formation in the vicinity of the 
Lucy L mine is the Ochre Mountain limestone. Mas- 
sively bedded members of this formation make up 



» Butler, B. a., op. cit., p. 482. 



GEOLOGICAL BURVEY 



PROFESSIONAL PAPER 177 PLATE IS 
£/. 5946' 



, Gold-bearing 
e % .crushed rock 

'Crushed dark "*~~-C- 



'Ot, 



porphyry 



EXPLANATION 



Quartz 
rnonzonite 

Si |> i 

Quartz outcrop 
on level 



H 



^ 



Stope 
Fault 

Strike and dip 



Tunnel level 
Lower level 



Lower /eve/ 77 below 
tunnel /eve/ o 









lower /eve/ 19' below i&, 
tunnel level -*j? 



Series of u/K/er/iand <sg0B. 
stapes from winze ^^ 







N\> 


*!?" 


$S 






% 



t RAISd 



l4i -iiJ^ 



Block of black shale 






4>W 



>«^ 



£/,S9S0 r ± 



o 

_! I I l_ 



ioo Feet 




« 


r 




u 


1 




* 

<*- 


v 




L 


* 




3 


< 




<fl 






C 


K 




°n 




« 


t 




-p 


< 






^ 




c 


^ 







k 
-» 




N 


> 


Hornfels 


c 


V 







^ 




E 




,< v -iLltl^Ii^ii-^ 


_S— 


-VTV 


f -^rir?r-^Ty*~T^ lrzrX 


^tf 






(B 


, 




3 


„ 




B 


7 




<~ 






O 


r« 




k< 




>>K 




ty 




^ /T 




c J* 
o i 


/•~. 

1 \ 
1 i 
; i 


/ A 


i 


A 


i I Tungsten 


"J 




J j working's 

1 | 
I i 
1 

1 i 
1 * 



PLAN OF WORKINGS, LUCY L MINE. 



MINES AN© PROSPECTS 






the greater part of the hill (altitude 6,125 feet) on 
whose slopes the mine workings are found. The lime- 
stone is shattered and locally bleached but shows 
practically no development of silicate minerals. 
Strikes and dips are almost impossible to determine 
by reason of the thickness of the beds and the wide- 
spread shattering. Those that were obtained, however, 
suggest that minor warping or folding has been 
widespread. 

Two other sedimentary formations are exposed on 
the lower slopes of the hill. One of these is the Man- 
ning Canyon formation, which crops out in the gulch 
on the south side of the hill and is also seen at the 
portal of the south tunnel. In the tunnel the forma- 
tion is composed of badly crushed and crumpled 
black shale, with thin rusty sandy partings. On the 
surface southeast of the portal reddish quartzites are 
also found in the formation. About 20 feet from the 
portal the black shale is succeeded by a zone of 
intensely crushed shale in which are included blocks of 
Ochre Mountain limestone, and this in turn is followed 
by 60 feet of the massive limestone (pi. 13). A nearly 
vertical normal fault again exposes the breccia. These 
relations clearly require that the breccia zone represent 
a thrust fault, and on page 73 it was indicated that 
it is an eastern continuation of the Ochre Mountain 
thrust. The other formation is found on the eastern 
slope of the hill in and near the northern of the two 
tunnels. Here relatively thin bedded rocks crop out, 
which resemble closely the metamorphosed sandstones 
and limestones of the central facies of the Oquirrh 
formation that are exposed a short distance to the 
north. A specimen of a metamorphosed sandstone 
taken from a point near the tunnel portal was com- 
posed largely of quartz that was presumably recrystal- 
lized, as ' the grains were rimmed by fine dustlike 
material. Scattered throughout the quartz were 
smaller crystals of diopside and less abundant grains 
of orthoclase. Veinlets of tremolite cut the rock. 
Other beds, presumably with a higher original content 
of calcium carbonate, have been altered to garnet- 
diopside rock or to one composed chiefly of wollaston- 
ite. These beds are exposed throughout the greater 
part of the northern workings and must therefore 
underlie the Ochre Mountain limestone, which crops 
out at the surface. The contact between the two is 
not well exposed on the surface, but, in view of the 
presence of the thrust in the southern tunnel, it seems 
certain that this contact represents the same fault. 

Quartz monzonite terminates the sedimentary rocks 
on the north and east, and small lenticular masses 
of the same rock occur on the south and west. The 
mine workings show that the quartz monzonite also 
underlies areas where sedimentary rocks are exposed 
at the surface, and it seems rather certain that igneous 
rock is present at no great depth beneath the whole 
hill. The upper surface of the quartz monzonite must 
be rather flat, although in detail it is very irregular 



Ji'oM Y//9, 

c'ar A V//< ' 



ir 









J» 



& 



W 






dm 



fffi 






M 

Z*« c 
in, *" 



o vm 

OLD 



(fig. 26). Two dikes are cut by the northern tunnels, 
for example, that do not appear at the surface, although 
the section suggests that they must join the main mass 



142 



GOLD HILL MINING DISTRICT, UTAH 



of the intrusive not much more than 100 feet below 
their apices. A specimen of relatively unaltered 
quartz monzonite taken from the western workings 
from the southern tunnel is of the normal type of 
biotite-quartz monzonite but shows some slight meta- 
morphism by the presence of a few idiomorpbic diop- 
side crystals. Near the ore bodies the rock is as a 
rule considerably altered. A specimen from the south- 
ern tunnel workings about 75 feet east of the shaft has 
been largely replaced by garnet, diopside, and horn- 
blende, and these minerals in turn have been partly 
altered to quartz, sericite, and calcite. Another speci- 
men adjacent to the ore body on the bottom level of 
the southern workings has been bleached to a dull 
cream-colored rock in which the igneous texture can 
be recognized only locally. The dark minerals have 
been completely and the feldspars partly replaced by 
calcite, sericite, and quartz. Butler M noted that adja- 
cent to the tungsten deposits on the southeastern 
slope of the hill diopside, a green hornblende, carbonate 
minerals, epidote, and a few crystals of allanite have 
been introduced. Underground the quartz monzonite 
locally includes blocks of the sedimentary formations. 
One of the Manning Canyon formation was observed 
in the long crosscut southeast of the shaft in the 
southern workings, and another, probably of the 
Oquirrh formation, which was found to be calcite- 
tremolite rock, was found at the extreme east end of 
these workings. 

Two kinds of ore have been mined from the Lucy L 
property. These are gold-bismuth ore and tungsten- 
copper ore. The largest body of the gold-bismuth ore 
was found in the south workings about 225 feet from 
the portal of the tunnel and took the form of a lenticu- 
lar mass of quartz 50 to 75 feet long and 10 feet in 
maximum thickness. The ore body has a crescent 
shape in horizontal section, with the concavity to the 
northwest. The dip is 40°-50° NW. Quartz mon- 
zonite forms both walls of the ore. On the tunnel 
level it is separated from the ore on the hanging-wall 
side by a well-defined slip and on the footwall side by 
a zone in which dark silicates are abundant. Both 
of these features are absent on the bottom level, where 
the quartz monzonite walls are thoroughly bleached. 
Locally minerals resembling kaolinite and halloysite 
have been developed in this rock as a result of weath- 
ering. On this level the dimensions of the ore body 
appear to be considerably smaller. 

The ore is relatively simple mineralogically. It is 
composed almost entirely of quartz, which has been 
thoroughly shattered. The fracture planes in almost 
all places have been filled with a dark-brown iron oxide, 
with which yellow-brown jarosite is only locally asso- 
ciated. The microscope shows that the quartz has 
been formed at two stages. The earlier • quartz is 

« Butler, B. S., Ore deposits of Utah: U.S. Oeol. Survey Prof. Paper 111, p. m, 
1920, 



glassy and coarsely crystalline and tends to be euhe- 
dral. It forms the greater part of the ore body. The 
younger quartz is found chiefly in the interstices of 
the older crystals and is generaEy separated from them 
by a layer of chalcedony fibers. It is very fine grained. 
Locally this fine-grained material is found in relatively 
large areas where it has clearly replaced the older 
quartz. Sericite occurs in association with much of it. 

The metallic minerals observed were bismuthinite 
and native bismuth (both largely oxidized to bis- 
mutite), pyrite (also oxidized), and native gold. 
Specimens containing these minerals were not abun- 
dant, but the impression was gained that they occur 
either in or near the areas of fine-grained quartz. All 
the gold seen was embedded in bismutite. Kemp M 
has described a gold telluride from this mine, but none 
was found by the writer. A copper mineral was also 
probably present in the primary ore, as a small amount 
of malachite was observed. The bismuth minerals 
and gold are of rare occurrence in the quartz body 
and appear to be limited to relatively small shoots 
that are roughly outlined by the stoped areas shown 
in plate 13. No figures are available as to the content 
of gold or bismuth in the shoots. 

Gold-bearing rock is also reported to occur in two 
zones near the west end of the bottom level of the 
northern workings. (See pi. 13.) This is a shattered 
grayish-green rock in which large cleavage plates of 
calcite may be seen that are interrupted by dark min- 
erals. There are a few pseudomorphs of "limonite" 
after pyrite and some copper stains. The microscope 
shows in addition to calcite, green hornblende, garnet, 
and apatite, together with numerous veinlets of fine- 
grained quartz. No gold was observed in the slide. 

Tungsten-copper ore is found in a vein about 400 
feet south of the north tunnel portal. The vein has a 
width of 4 feet or so and is exposed for a length of about 
100 feet by a series of shaEow pits in which it strikes 
about north and has a nearly vertical dip. The walls 
are both of quartz monzonite and are roughly parallel to 
the intrusive contact, which is less than 50 feet distant 
to the west. Some slickensides may be seen along the 
walls. The ore extended downward only about 15 
feet. The eastern workings from the south tunnel 
underlie the northern extension of the vein about 100 
feet below the surface but show no sign of similar 
mineralization. 

The ore consists chiefly of dark silicates in a scant 
matrix of calcite. The calcite is coarsely crystalline 
and, though largely replaced by the silicates, is readily 
recognized by the reflection of light from the large but 
interrupted cleavage surfaces. Locally the calcite is 
relatively unreplaced, and in these areas the adjoining 
silicates show good crystal faces. Pyrite and chalcqpy- 
rite are more abundant in these calcite areas than in 



» Kemp, J. P., Notes on Gold Hill and vicinity, Tooele County, western Utah: 
Boon. Geology, vol. 13, p 260, 1918. 



MINIS AND PROSPECTS 



143 



the rock rich in silicates. The distinguishing feature 
of the ore is the presence of crystals of yellowish-gray 
scheelite, which may reach an inch in length. 

The silicate minerals present include andradite 
garnet, diopside, epidote, titanite, green hornblende 
(partly altered to actinolite), and orthoelase. There 
appears to be a definite sequence in their formation, 
and the scheelite appears to belong to one of the early 
stages. Quartz and calcite veiolets with associated 
sericite and chlorite cut all the other minerals. In 
addition to the minerals cited, axinite and zoisite were 
noted in. specimens collected in 1912 by Butler from 
this property. 

Picked specimens of the ore are rich in scheelite or 
in chalcopyrite or its oxidation products, but the small 
extent of the deposit and the rather erratic distribution 
of the valuable minerals in it have prevented any 
recent development. It is thought that a small lot of 
tungsten ore was shipped some years ago from this 
property, but no data as to the grade were obtained. 

A similar mineral assemblage but without any 
scheelite is exposed at the surface contact of the quartz 
monzonite by a prospect pit west of north from the 
tungsten workings and also within the sedimentary 
rocks in the northern tunnel. The copper present in 
these occurrences is far too low for them to be of value. 

BOSTON 

The Boston claim is south of the Lincoln Highway 
about 6,000 feet east-southeast of the summit of 
Gold Hill. It is said to be owned by the Boston-Utah 
Mining Co., whose headquarters are at Los Angeles, 
Calif. No shipments are known to have been made 
from the property. 

Quartz monzonite forms the wall rock of the vein 
on the claim, which has been explored by several 
shallow surface cuts and by an inclined shaft of no 
great depth. To the north the vein strikes N, 40° W. 
and dips about 45° SW. Toward the south the strike 
swings to nearly due north and the dip steepens. The 
vein is offset for a few feet by several minor faults and 
is apparently terminated to the south by a larger one. 

The vein filling is from 1 to 3 feet thick and consists 
of crushed quartz monzonite together with quartz, 
arsenopyrite, and oxidized minerals of iron, lead, and 
arsenic. Locally arsenopyrite and scorodite are present 
to the almost complete exclusion of the other minerals. 
At the surface the results of all stages of the alteration 
of the sulphide to scorodite may be observed. The 
arsenopyrite is reported by W. M. Lamb, of Gold HOI, 
to carry $14 in gold to the ton. Near the south end of 
the vein, at the inclined shaft, some lead-silver ore is 
said to occur. Specimens of plumbojarosite or the 
related arsenic compound may be seen on the dump 
and presumably were the source of the lead. 

NEW YORK 

The New York claim, on the southwest side of Dutch 
Mountain about half a mile north of altitude 5,963 feet 



on the Ferber Boad, is owned by Messrs. Bailey and 
Delmonico, of Gold Hill. In 1927 some assessment 
work was being done on the claim in developing a small 
mass of lead-arsenic ore that was found along a fault 
that separates the Pottsville portion of the Oquirrh 
formation from higher beds in that formation. The 
ore exposed was entirely oxidized and appeared to 
consist chiefly of scorodite. Assays of the ore were 
said by Mr. Bailey to show a content of $4.40 in gold 
and 12 ounces of silver to the ton and 8 to 9 percent of 
lead. 

SILVER ft GOLD MINING CO. 

The Silver & Gold Mining Co., Inc., whose head- 
quarters are in Spanish Fork, Utah, owns five claims 
about a mile northeast of the Western Utah mine and 
east of Calico Hill. So far as known no shipments 
have been made from the claims. 

In 1926 the company was engaged in exploring a 
vein that cropped out in limestones and sandstones of 
the Oquirrh formation about 2,000 feet east of the sum- 
mit of Calico Hill. The sedimentary rocks are very 
close to the northern contact of the quartz monzonite 
stock, and the igneous rock was cut at a shallow depth 
in the inclined shaft that was being sunk on the 
vein. 

The vein occupies a fault fissure, the movement along 
which occurred before the mineralization. The throw 
along it amounts to about 10 feet, as is shown by the 
displacement of the quartz monzonite contact. The 
dip is about 55° W. at the surface but steepens to 65° 
after it enters the igneous rock. In the portion of the 
vein enclosed by sedimentary rocks the vein is as 
much as 4 feet in width and is almost completely oxi- 
dized. Quartz, scorodite, and oxidized minerals of 
iron and lead are the most prominent minerals in this 
portion. In the quartz monzonite the vein is much 
thinner (3 to 12 inches) and has been much less affected 
by oxidation. Pyrite, arsenopyrite, galena, and sphal- 
erite were recognized in sulphide-bearing specimens 
from this part of the vein. The operators reported 
that the vein as exposed in June 1927 had an average 
content of $10 in gold and 3 ounces in silver to the ton. 
In places high gold assays were obtained. 

MASCOT 

The Mascot group of claims, in the quartz monzonite 
area north of Overland Canyon and west of Barney 
Reevey Gulch, is owned by Frank J. Guilmette, of 
Gold Hill. A small amount of development work has 
been done on several quartz-sulphide veins that strike 
about north and dip on the average 45° W. The metal 
present is chiefly arsenic, in the form of both arseno- 
pyrite and scorodite, but locally there are small shoots 
of lead ore. On the Mascot No. 2 claim a small peg- 
matitic pipe is exposed, which is reported to contain 
small amounts of scheelite. The surface dimensions 
of this pipe are about 5 by 3 feet. 



144 



GOU) HILL MINING DISTRICT, UTAH 



MONTE DEI, BET 

The Monte del Rey group of four patented claims 
is in Hopkins Gulch a short distance northwest of the 
Midas mine. It is owned by P. H. Robinson, of Gold 
Hill. A long cross-cut tunnel has been driven west- 
ward in quartz monzonite from a point about 100 
yards south of the spring to cut several veins that are 
exposed on the surface. The veins contain chiefly 
arsenic minerals but locally carry small quantities of 
lead minerals. No production is known from the 
group. 

FOBTTFNA 

The Fortuna group of three claims is in Hopkins 
Gulch about three-quarters of a mile northwest of the 
Midas mine. The claims are owned by Mrs. Emma 
C. Thompson, of Denver, Colo. Several surface cuts 
and pits have been made on a quartz-arsenopyrite 
vein in quartz monzonite similar to the other veins in 
this region. Locally it contains small quantities of 
lead minerals. No shipments have been made from 
the property. 

BONANZA 

The Bonanza group of claims, owned by Mrs. Emma 
C. Thompson, of Denver, Colo., covers most of the 
ridge north of the Cyclone mine. In 1926 it was under 
lease to Prank J. Guilmette, of Gold Hill. So far 
as known, no shipments have been made. 

The ore is found as small shoots in a wide shear zone 
in quartz monzonite that has a general strike of about 
N. 20° E. and dips 65° W. The ore shoots, which are 
locally as much as 5 feet in width, contain chiefly 
arsenic ore, in the form of arsenopyrite and scorodite, 
but in some places a large proportion of the ore is 
composed of lead and zinc minerals. Mr. Guilmette 
was developing one such shoot in 1926. 

The 170-foot tunnel on the claim exposes a dike of 
dark porphyry that has been cut by numerous minor 
faults. 

CYCLONE 

The Cyclone mine is about 1,600 feet south-southeast 
of U.S. Mineral Monument No. 9, in Barney Reevey 
Gulch, on the south side of Montezuma Peak. The 
mine takes its name from the Cyclone claim, which is 
one of the six claims owned by the Engineers Develop- 
ment Co., of Salt Lake City. This company acquired 
the claims in 1925 and since that time has established 
a camp and done a moderate amount of development 
work. The workings consist of an inclined shaft on 
the vein, from which, at a depth of 80 feet, a drift has 
been extended to the north more than 400 feet. Several 
raises extend upward from the drift, and the inclined 
shaft has been extended down the dip an unknown 
distance. The vein has also been explored by a tunnel 
whose portal is north of the shaft collar. Shipments of 
lead-silver ore are reported to have been made from 
the property in 1926. 



Only two formations are exposed in the vicinity of 
the mine. Quartz monzonite underlies most of the 
surface. It does not differ notably from exposures of 
this rock elsewhere. The quartz monzonite is cut by 
a dike of granite porphyry, a light greenish-gray rock 
that weathers in many places to shades of brown. This 
rock contains numerous phenocrysts of quartz 1 to 2 
millimeters in diameter and less abundant phenocrysts 
of biotite and feldspar. The microscope shows that 
the feldspar phenocrysts include both orthoclase and 
albite. The groundmass of the rock is very finely 
crystalline and is made up of quaxtz, feldspar, and 
biotite. The dike strikes a little east of north and 
dips 50° W. 

The quartz vein that contains the ore minerals 
follows the hanging wall of the granite porphyry dike. 
It is not continuous, stretches of quartz and sulphides 
alternating with stretches in which a foot or more of 
gouge takes the place of the vein. The alternation 
appears to be correlated with changes in the strike of 
the vein. In general, the portions with a nearly 
north-south strike are occupied by gouge, and those 
that strike east of north contain quartz and sulphides. 
Similar variations along the dip of the vein are exposed 
in the raises from the level. In at least one place the 
barren stretches may be correlated with a local steepen- 
ing in the dip of the vein. 

Gouge is also found on either wall of the quartz or 
on both. About 300 feet north of the shaft, for 
example, there is a few inches of gouge between the 
vein and the footwall granite porphyry and about a 
foot of gouge and crushed quartz monzonite on the 
hanging wall. The gouge contains fragments of quartz 
and sulphides and was reported to contain in one 
place 17 percent of arsenic. 

Adjacent to the vein the granite porphyry has been 
considerably altered. The feldspar phenocrysts have 
been changed to a soft claylike mineral and the 
groundmass to a fine-grained aggregate of quartz and a 
little sericite. The quartz monzonite hanging wall, on 
the other hand, has been but little affected. 

The drift from the inclined shaft has disclosed five 
shoots of quartz-sulphide ore. The most southerly of 
these is the longest, extending about 100 feet north- 
ward from the shaft. In the succeeding 200 feet to 
the north three small shoots are exposed, two of them 
having lengths of about 15 feet and one of 30 feet. 
The fifth shoot starts about 300 feet north of the shaft 
and has a length of about 60 feet. The thickness of 
the shoots reaches a maximum of about 3 feet, but the 
average thickness is between 18 inches and 2 feet. 

The vein filling, as shown on the drift from the shaft 
consists of a mixture of quartz and sulphides in which 
the proportion of each varies, locally the one or the 
other predominating. The sulphides recognized are 
pyrite, arsenopyrite, galena, chalcopyrite, aikinite, and 
sphalerite. Small quantities of an iron-rich dolomite 
replace the sulphides locally. In most places the sul- 



MINES AND PEOSPBCTS 



145 



phides are fine-grained and intermixed, but in a few 
places concentrations of a single mineral are found in 
Which the grain size is considerably greater. 

A series of 11 samples taken at 5-foot intervals 
along the southern ore shoot showed the following 
variations in content: 

Gold (average) _ - . . .ounces to the too. . 0, 03 

Silver (average) do, — 6 

Lead percent-- 0. 4^8. 2 

Copper ....do 0. 5-1. 7 

Zinc do.,-. 0. 5-3. 8 

Arsenic do 0. 5-7. 3 

The ground-water level corresponds closely with the 
level of the drift, but there is comparatively little 
sign of oxidation in the vein at this horizon. The 
bottom of complete oxidation was found to be about 
35 feet above the drift level in the shaft and about 30 
feet above the level in a raise 300 feet north of the 
shaft. About 100 feet north of the shaft, at a point 
that corresponds with the position of a stream channel 
on the surface, the ore is partly, oxidized and contains 
much greenish-blue chalcanthite. Near the surface 
yellow-brown powdery jarosite and plumbojarosite, 
both of which probably contain a little arsenic, are 
abundant. 

SUCCESS 

The Success mine is about 2 miles southeast of the 
Western Utah Copper Co.'s Gold Hill mine and 6,000 
feet due west of bench mark 5060 on the Lincoln High- 
way. It is owned by W. F. Peters, of New York City, 
but in 1926 the property was being worked under lease 
by D. C. Scott, of Park City, Utah. In 1927 Messrs. 
Sevy & Wilkins, of Gold Hill, were lessees. Several 
shipments of lead-silver ore have been made from the 
property. In 1920 a lot of 94 tons of ore contained 
0.06 ounce of gold and 32.3 ounces of silver to the ton, 
1.55 percent of copper, and 8.96 percent of lead. 
Smaller shipments were also made in 1926 and 1927, 
but their grade is not known. 

The country rock at the mine is quartz monzonite, 
which is rather thoroughly crushed and altered. 
Surface exposures of the rock near the mine are 
relatively few. In a specimen taken from the foot- 
wall of the vein all the original minerals of the rock, 
except quartz and the accessory minerals, have been 
almost completely replaced by sericite, ealcite, and 
chlorite. 

The ore is found in a quartz vein cutting the igneous 
rock. As exposed in the inclined shaft on the vein, 
the strike is northwest and the dip 30°-45° W. In the 
shaft the thickness of the vein ranges from a few inches 
to about 4 feet. There has been considerable move- 
ment after the formation of the vein, which has resulted 
in the presence of gouge on either or both walls. Dur- 
ing the visits to the mine in both 1926 and 1927 the 
greater part of the workings from the shaft were 
inaccessible, but on one short drift on the vein north 
of the shaft considerable variations in the strike of 



the vein were observed. The writer is informed that 
the vein was cut off at one place by an east-west fault 
and that the faulted segment was never found. 
Although the fault was not observed in the mine, the 
offsets of the dike east of the mine workings as shown 
in plate 2, suggest that there has been a relative shift 
to the east on the south side of the fault. 

Oxidation of the ore minerals is complete at the 
surface, jarosite and plumbojarosite being abundant. 
Sulphides are found in the shaft about 90 feet below 
the collar (about 45 feet vertically), although the 
ground-water level is at 125 feet (about 65 feet 
vertically). The primary ore consists of white coarsely 
crystalline quartz, pyrite, arsenopyrite, galena, sphal- 
erite, and tennantite. Polished sections show the 
presence also of thin veins of a carbonate mineral. 
As in other veins of this type in the district, both the 
ratio of the sulphides to the quartz and their relative 
proportions to one another vary considerably from 
place to place. Locally there are concentrations of 
cleavable black sphalerite that has a distinctly non- 
metallic appearance when slightly weathered. 



SPOTTED FAWK 



The Spotted Fawn group of claims, now located 
under the name of the Silver Hill group, is in Spotted 
Fawn Canyon, on the east side of Dutch Mountain. 



+ 63 AT 
s0 'j& SURFACE 




N 

; . 



+ 48 AT 

SURFACE 



i oo Feet) v o' 

PORTAL 

Figure 27. — Plan of tunnel and surface workings on north side of gulch, Spotted 
Fawn mine. 

The Gold Hill Mines Co., of Salt Lake City, is the pres- 
ent owner. Shipments amounting to 78 tons were 
made from the property during 1901-17. These had 
an average content of 0.038 ounce of gold and 25.1 
ounces of silver to the ton and 18.1 percent of lead. 
The main workings on the group are on the northeast 
side of the canyon, where a tunnel has been driven 
beneath two shallow shafts (fig. 27). Some work has 



146 



GOIiD HILL MINING DISTRICT, UTAH 



also been done on the southwest side of the canyon, 
in another shallow shaft from which some short drifts 
have been driven. A well-built bunkhouse and a 
machine shop in which an air compressor is housed 
are situated just below the mine workings. These 
buildings may be reached by a wagon road following 
the bottom of the canyon. This road is passable by 
automobiles to a point within a quarter of a mile of 
the mine. 

The mine workmp are in much faulted Middle 
Cambrian rocks that he a short distance beneath the 
Ochre Mountain thrust. The ore bodies on both sides 
of the gulch occur in thin-bedded limestones, locally 
dolomitized, but in the tunnel only the Busby quartz- 
ite was observed. South and east of the mine workings 
the contact between the limestone and the quartzite 
is a fault striking west of north that is a branch of the 
Spotted Fawn fault, the main branch of which lies 
about 500 feet west of the tunnel portal. The branch 
fault, however, cannot explain the presence of quartzite 
in the tunnel immediately beneath limestone exposed 
on the surface. To account for these relations (see 
p. 82) a nearly flat fault must intervene between the 
two. Such a fault is not readily recognized on the 
surface. The breccia exposed in the top 10 feet of the 
raise near the north end of the tunnel probably repre- 
sents the fault breccia, and the fault must therefore 
dip gently to the south. Several nearly horizontal 
fractures that cut the quartzite beds exposed in the 
tunnel must be subsidiary to the major fault. 

The ore is found along fissures striking east of north 
and dipping 50°-65° W. It consists of rather coarse- 
grained white quartz with some barite and local con- 
centrations of galena in which are found small amounts 
of pyrite and other sulphides. Oxidation of the galena 
to anglesite and cerusite in most places has been rather 
complete, but unaltered sulphide nodules are not un- 
common. The flat fault that must separate the quartz- 
ite from the limestone must also limit the ore downward, 
for no evidence of comparable mineralization was found 
in the tunnel. It was not ascertained whether the lack 
of ore in the tunnel was the result of movement along 
the fault subsequent to mineralization or whether the 
fault was formed earlier than the ore and the unfa- 
vorable character of the quartzite prevented any 
deposition of ore minerals. 

WBSTEBN UTAH EXTENSION COFFEE CO. 

The group of 15 patented claims owned by the West- 
ern Utah Extension Copper Co. extends to the south- 
east from the open cut of the Western Utah Copper Co. 

The ownership is reported to be the same as that of 
the Pole Star Copper Co. Superficial exploration has 
been carried on at several places on the group, but on 
only one claim, the Helmet, has any considerable 
amount of underground work been done. In 1917 
and 1918 nearly 200 tons of ore was shipped from this 



claim. It had an average content of 0.026 ounce of 
gold and 5.4 ounces of silver to the ton and 4.08 per- 
cent of copper. The property appears to have been" 
idle since 1918. 

The workings on the Helmet claim consist of a main 
tunnel and several higher levels, on all of which some 



Dike-- 



SHAFT | 



kj«3* 



'Vein 



^. ^Gouge 



.«'/ 



I No ore 



, . JKAISE 
Breccia' \lfto$urf~ace workings) 

INCLINE SHAFT } 3 °' 

/SO Veep 



i-30 - 



^Veirs 



^"mI Vein weak 



Crushed 



lOOFeet 



Figure 28. — Plan of tunnel level, Western Utah Extension Copper Co, 

stoping has been done. Nearly 1,000 feet of drifting 
has been done on the tunnel level (fig. 28), and from 
it two interior shafts have been sunk. The tunnel 
at an altitude of 5,751 feet is more than 250 feet lower 
than the summit of the east-west ridge beneath which 
it is driven. 



MINES AND PROSPECTS 



147 



The claim is near the central part of the quartz 
monzonite stock, and this rock forms the walls of the 
ore. Both underground and on the surface a dark 
greenish-gray altered porphyry is exposed as a dike 
cutting the quartz monzonite. It is about 4 feet wide 
and strikes east of north. 

The ore is found in a quartz vein that strikes approx- 
imately north and has a normal dip of 60 o -70° W. 
The fissure occupied by the vein is clearly a fault fis- 
sure, for it cuts and displaces the porphyry. This is 
clearly shown in the tunnel about 150 feet from the 
portal, where the dike is present in the hanging wall 
of the vein but not in the footwall. The exposures of 
the dike on the surface indicate that the throw along 
the fissure is normal and amounts to about 50 feet. 

The vein and the dike are cut by another fault about 
500 feet south of the portal of the tunnel. This fault 
strikes about N. 20° W., dips to the west, and is marked 
by considerable brecciation. North of its intersection 
with the vein a crosscut shows 10 feet of gouge along 
the fault, the footwall of which dips 30° and the hang- 
ing wall about 85°. As the vein approaches the fault 
its strike swings to northwest and its dip flattens to 
30°. The offset due to the fault on the tunnel level 
amounts to about 40 feet, the portion of the vein in 
the footwall of the fault being to the north. This 
implies either that the fault is reverse or that it is a 
normal fault with a large horizontal component. 

The ore is almost completely oxidized from the sur- 
face to the tunnel level. It consists of quartz, altered 
quartz monzonite fragments, and various copper, iron, 
and arsenic minerals. The thickness of the vein ranges 
from a few inches to 3 feet, but in some of the thicker 
portions the ore minerals occupy only part of the vein. 
In a few places sulphide minerals had been preserved. 
Those recognized were arsenopyrite, pyrite, and sphal- 
erite. The oxidized ore minerals appear to have been 
chiefly copper pitch and a deep-brown fine-grained 
scorodite. In many places, however, there are striking 
concentrations of blue-green chrysocolla, bright-green 
clinoclasite, and olive-green oHvenite. The sulphide 
that was the source of these copper minerals was not 
recognized in the few specimens of unoxidized material 
that were collected. 

At several places on this group of veins prospecting 
has disclosed veins in which arsenopyrite and scorodite 
are the most abundant constituents. 

CLIMAX 

The Climax group of 12 patented claims is in Roden- 
house Wash. The greater part of the work on the 
group has been done a short distance west of the prom- 
inent hill at an altitude of 5,675 feet on the north side 
of the wash. J, P. Gardner, of Sarasota, Fla., is 
reported to be the owner. The property has been 
idle for several years. A partly caved vertical shaft 
filled with water and the remains of a shaft house are 



about the only signs of former activity. Custer 68 
reports that the shaft was 150 feet deep and that from 
it 250 feet of drifts and crosscuts had been driven. 
He further records the shipment of two cars of ore that 
contained 29 ounces of silver to the ton and 27 percent 
of lead. 

Chloritized and sericitized quartz monzonite forms 
the wall rock of the ore bodies. East of the vertical 
shaft this rock is cut by prominent quartz and quartz 
carbonate veins that strike nearly north and dip at 
rather low angles to the west. So far as could be told 
the ore does not extend through or beyond them. 

The vertical shaft is sunk on a vein striking N. 82° 
W. From the scant exposures on the surface and from 
small amounts of ore on the dump, the vein filling 
appears to have consisted of quartz, pyrite, arseno- 
pyrite, galena, and sphalerite. The sphalerite appears 
to have been particularly abundant. These minerals 
are all cut by veinlets of a brown-weathering siderite. 

SOOTHEBN eOOTEDEBATE 

The patented Southern Confederate claim, one of 
the oldest in the district, is on the high ridge southeast 
of the town of Clifton, the end of the wagon road at 
an altitude of 6,742 feet marking the present camp 
site on the claim. It is owned by the Southern Con- 
federate Mining Co., Inc., of Salt Lake City, and in 
1926 was under lease to T. E. Wessell. Much of the 
ore utilized by the old Clifton smelter is reported to 
have come from this property. Small shipments have 
been reported for the years 1918, 1919, and 1926. 
These shipments have averaged about 30 percent of 
lead and 30 ounces of silver to the ton. Small quan- 
tities of zinc, copper, and arsenic are also present. 

The ore is found in a shear zone as much as 20 feet 
in width that strikes about N. 50° E. and dips 75°-80° 
SE. The wall rock is quartz monzonite altered to a 
dense greenish rock in which only small quartz grains 
can be recognized with the hand lens. The microscope 
shows that the alteration consisted of both sericitiza- 
tion and the introduction of fine-grained quartz and 
chlorite. In this ore zone lenses of lead ore as much as 
2 feet in width and, exceptionally, 50 feet in strike 
length have been found. A shaft on the vein is said 
to reach a depth of 150 feet, but less than 50 feet of it 
is now accessible. 

The ore minerals in these lenses consist almost en- 
tirely of the oxidized lead minerals anglesite, cerusite, 
and plumb ojarosite, of which the anglesite is by far 
the most abundant. Unoxidized remnants of fine- 
grained galena are not uncommon, but no other sul- 
phides were recognized. Limonite pseudomorphs after 
pyrite are found in many places in the wall rock. 
Coarsely crystalline quartz is the chief gangue mineral. 
Small quantities of azurite and malachite are dis- 
tributed throughout the ore. 

« Custer, A. B., Deep Creek, Clifton mining district, Utah: log. and Min. Jour., 
vol. 103, p, 920, 1917. 



148 



GOLD HILL MIKING DISTRICT, UTAH 



There is abundant evidence of movements along 
the vein since the ore was deposited. These have 
formed coarse breccias in the portions of the vein rich 
in quartz, and gouge walls to the ore shoots were noted 
in several places. 



BED JACKTO 



The Red Jacket claim is immediately north of the 
Southern Confederate claim, less than half a mile 
southeast of Clifton. The owner of the claim is said 
to be R. W. Young, and in 1926 J. H. Allen and asso- 
ciates were at work under a lease and bond. like the 
Southern Confederate, the Red Jacket is reported to 
have furnished ore to the old Clifton smelter. The 
only recent production known is that made by the 
lessees in 1926. The grade of the lead-silver ore 
shipped is not known. 

As on the adjacent claim, the ore is found in a shear 
zone in altered quartz monzonite. The shear zone 
is about 4 feet wide, strikes northeast and dips steeply 
to the southeast. The workings on the vein are on the 
east side of the ridge line and consist of several tunnels 
and cuts on the vein. In one of the tunnels a winze 
was sunk on the vein and, at a depth of about 180 feet, 
is said to have struck an eastward-dipping fault that 
terminated the ore. This winze could not be examined 
at the time of this survey. 

The ore is found in lenses in the shear zone and con- 
sists of coarse white quartz with galena and a little 
pyrite, together with oxidation products of the sul- 
phides. Anglesite is the most abundant of these and 
forms the bulk of the ore. Other lead minerals present 
include cerusite, plumbojarosite, and, near the surface, 
rather considerable amounts of green crystalline mime- 
tite. Small orange-colored crystals of wulfenite are 
also found in the oxidized ore. 

COPPJBB QOTEN MIDLAND MINING CO. 

The Copper Queen Midland Mining Co., whose 
headquarters are at Grantsville, Utah, owns a group 
of unpatented claims on the southwest side of Mon- 
tezuma Peak, a short distance east of benchmark 5855, 
at the head of Overland Canyon. Prospecting has 
been done on several veins, chiefly by shallow cuts or 
pits. On one of the veins, however, a tunnel more 
than 600 feet long has been driven. Small shipments 
of ore were made from this group of claims in 1916, 
1918, and 1919, which averaged 17.4 ounces of silver 
to the ton, 0.56 percent of copper, and 15.35 percent 
of lead. 

The ore is found within the small triangular outcrop 
of quartz monzonite that lies to the west of and is 
connected with the larger intrusive mass on the south 
side of Montezuma Peak. The quartz monzonite con- 
tains both biotite and hornblende, in addition to the 
feldspars and quartz, and does not differ in any respect 
from the rock that forms the greater part of the main 
stock. Both the southern and northwestern borders 



of this small intrusive area are controlled by older 
faults and, because of this, three different sedimentary 
formations are in contact with the igneous rock — 
the Oquirrh formation on the northwest, the Manning 
Canyon formation on the east, and the Ochre Moun- 
tain limestone on the south. 

The ore occurs in veins within the quartz monzonite 
that strike N. 15°-30° E. and dip 25°-40° W, Several 
of these veins have been developed, but the most 
persistent one appears to be that followed by the 
Midnight tunnel, whose portal is about 3,000 feet east 
of benchmark 5855. The vein is exposed throughout 
the length of the tunnel, a distance of 620 feet. The 
width of the vein ranges from 1 to 5 feet. As in other 
veins of this sort in the district, a moderate thickness 
of gouge is usually present on either the hanging wall or 
footwall, or both. In a few places nearly east-west, 
steeply dipping faults cut the vein and displace it for 
distances as great as 5 feet. In many places the quartz 
monzonite wall rock has been rather completely altered 
to sericite as much as 5 feet from the vein. Locally, 
however, the alteration was much less intense, and 
specimens taken less than a foot away may be essen- 
tially unaltered. 

In the tunnel much of the ore is unoxidized and is 
seen to consist of white coarse-grained quartz, in 
which are fragments of sericitized wall rock, and a 
variable content of sulphides. Among these, arseno- 
pyrite, pyrite, galena, sphalerite, and chalcopyrite have 
been recognized. The proportions and total quantity 
of these sulphides differ in different parts of the vein. 
Veinlets of a brown-weathering carbonate cut across 
the quartz and sulphides. Optical tests prove this to 
contain about 75 percent of the FeC0 3 molecule. In 
the surface workings oxidation of the sulphides has 
been nearly complete. In some places the oxidation 
products have migrated into fractures in the wall 
rocks, giving the appearance of spurs from the vein. 
Jarosite and plumbojarosite are among the most 
abundant of these later minerals. 

CASH BOY (MAMMOTH) 

The Cash Boy group of four claims is on the north- 
east slope of hill 5696, east of the Success mine. Two 
of the claims are owned by L. H. Sevy and C. H. Aber- 
crombie, of Gold Hill, and the other two (comprising 
the old Mammoth claims, owned by J. P. Gardner) are 
under lease and bond to them. Some ore was being 
mined at the time of visit in 1926, and it is reported 
that several shipments had been made in the past. 
The only one of which there is record was made in 
1915 and consisted of 4 tons, which contained 0.02 
ounce of gold and 26 ounces of silver to the ton, 0.8 
percent of copper, and 13 percent of lead. 

Two shallow shafts 2,200 feet apart have been sunk 
on shear zones in quartz monzonite that contain shoots 
of lead-silver ore. At the northern shaft an ore shoot 
strikes N. 80° W. and dips 60° SW. At the southern 



MINES AND PEOSP1CTS 



149 



shaft the strike of the ore is N. 50° W. and the dip 
40°~60° S. It is not known if the two shear zones 
exposed in the shafts are connected, but the strikes 
recorded are similar to those shown by a continuous 
porphyry dike that crops out a few hundred feet west 
of both localities. 

The ore shoots in the shear zones have relatively 
small dimensions and appear to be limited to regions 
in which abundant quartz has been introduced. At 
the surface the ore is completely oxidized, but in 
specimens on the dumps some sulphide minerals were 
observed. Galena, sphalerite, arsenopyrite, and pyrite 
were recognized in these specimens. The oxidized 
minerals include a lead-bearing jarositelike mineral, 
anglesite, cerusite, and locally considerable amounts of 
orange-colored wulfenite. 

NEW BALTIMORE 

The New Baltimore patented claim covers the 
slopes of hill 5625 in Bodenhouse Wash, about half a 
mile west of the Qimax mine. It is owned by J. P. 
Gardner, of Sarasota, Fla., but in recent years has been 
worked in a small way under lease by Swan Moline. 
Several small shipments have been made since 1923. 
One of 22 tons in that year contained 0.02 ounce of 
gold and 53 ounces of silver to the ton and 47 percent 
of lead and is representative of the other shipments. 
The developments consist of shallow surface cuts and 
shafts. 

The wall rock is the rather thoroughly altered quartz 
monzonite that is found over so much of the region 
drained by Rodenhouse Wash. Chlorite, sericite, cal- 
cite, and quartz have largely replaced the original 
minerals of the igneous rock, although in many places 
the alteration has preserved textures characteristic of 
the quartz monzonite, especially outlines of the old 
feldspar crystals. In one of the tunnels a dark altered 
porphyry was seen, but it could not be recognized on 
the surface. 

The ore is found as thin lenses in an east-west zone 
of Assuring that dips almost vertically. The ore shoots 
in this zone range in thickness from a few inches to a 
foot or so and are succeeded by lower-grade material 
within short distances along thg strike. Galena, show- 
ing relatively little alteration to anglesite, forms the 
greater part of the vein filling in the ore shoots. Near 
the surface it is found as rude nuggets coated with 
powdery calcite. Small amounts of pyrite, arseno- 
pyrite, and quartz are present with the galena and 
have largely replaced it in the vein beyond the ore 
shoots. Locally the galena has been more completely 
oxidized, and in such places the ore consists of anglesite, 
cerusite, plumbojarosite, mimetite, and descloizite, 
together with small amounts of copper minerals. The 
fissure zone, together with the ore shoots, is cut in 
several places by north-south faults that dip to the 
west. The throw on all of them is small, but they are 



accompanied by a considerable amount of gouge. In 
one place an eastward-dipping fracture intersected the 
vein, and it is said to have contained some very rich ore. 



The Bird claim, which is unpatented, is owned by 
Ollie Young, of Clifton. It adjoins the Southern 
Confederate on the northeast and encloses the con- 
tinuation of the fissure on that claim. A small lot of 
ore from the claim was included in a shipment by 
Young in 1926 that also contained ore from others of 
his properties. 

The relations of the ore are the same as those in the 
Southern Confederate. A drift tunnel driven south- 
westward on the vein showed about 2 feet of ore in 
1926. 

SHAY 

The Shay claims are near Goshute Spring, about a 
mile east of Montezuma Peak. In 1926 some pros- 
pecting was being done on a northeastward-striking 
vein in altered quartz monzonite that contained 
stringers of lead ore in a mixture of quartz and altered 
wall rock. The ore exposed was completely oxidized 
and was composed chiefly of a mineral resembling 
plumbojarosite. Numerous small orange-colored crys- 
tals of wulfenite were also observed in the ore. 

GOLD HILL STANDARD MINING CO. 

In. 1926 the Gold Hill Standard Mining Co. owned 
18 unpatented claims east of the town of Gold Hill. 
Several exploratory workings were being driven in that 
year on the Max No. 1 and Max No. 2 claims of the 
group, to expose a number of short linked veins in 
quartz monzonite that had a northwest strike and a 
dip of 30°-60° SW. The vein filling consisted of 
quartz, altered wall rock, galena and its oxidation 
products, and oxidized iron and arsenic minerals. The 
distribution of the several minerals is very erratic. In 
some places lenses of solid galena a foot wide and 
several feet long may be found, and in other places 
galena is entirely absent, and arsenopyrite and scoro- 
dite are the only metallic minerals present. Much of 
the galena has not been oxidized, but locally it has 
been converted to anglesite, plumbojarosite, and 
wulfenite. The galena-rich ore is said to contain 2 
ounces of silver to each percent of lead. 

GOLD BELT 

The Gold Belt claim, owned by W. F. Cummings, 
of Gold Hill, covers the small outcrop of Prospect 
Mountain quartzite that occurs at bench mark 4293, 
on the edge of the Great Salt Lake Desert. The 
bedding at this locality strikes N. 30° E. and dips 30° 
SB. The ore has replaced a breccia zone striking 
N. 60° E. and dipping 50° SE. It consists of white 
coarsely crystalline quartz with local splotches of 



150 



GOLD HILL MINING DISTRICT, UTAH 



galena and minor amounts of other sulphides. 
is only partly oxidized. 



It 



PAY ROCK 



The Pay Rock group of three claims is on the south 
side of Spotted Fawn Canyon, a short distance west of 
its entrance. In 1926 it was owned by L. H. Sevy and 
C. H. Abercrombie, of Gold Hill. In that year work 
was being done on the ridge line a short distance west 
of summit 5729. Here a thin streak of cerusite and 
plumbojarosite was found along a breccia ted bedding 
plane in the Prospect Mountain quartzite. Its width 
ranged from a fraction of an inch to several inches. 



The Undine group of four unpatented claims and a 
fraction is half a mile southeast of the U.S. mine and 
half a mile north of the Lucy L. It is owned by W. 
M. Lamb, of Gold Hill. There are several relatively 
shallow workings on the claims that are grouped in 
two areas — north and northwest of hill 6081 and north 
and east of hill 5882. Three or four shipments of ore 
have been made from the group, but at the time of 
visit only assessment work was being done. 

The rocks exposed on the claims are metamorphosed 
sandstones and limestones of the Oquirrh formation and 
quartz monzonite. The sedimentary rocks are found 
in relatively small and very irregular patches capping 
the higher summits. The igneous rock surrounds them 
and crops out in all the valley bottoms. These 
relations indicate that in this region the present sur- 
face approximates the original upper contact of the 
quartz monzonite. The sedimentary rocks are for the 
most part poorly exposed, but many of the limestone 
beds have clearly been replaced by silicate minerals. 
Garnet, wollastonite, amphibole, and a green musco- 
vite were recognized in the field, and a careful study 
would doubtless show many others. Chlorite and 
sericite are abundant in places in the quartz monzo- 
nite. Weathering has been more intensive here than 
in many other places, and this in part accounts for 
the poor exposures. A large part of the outcrops of the 
sedimentary rocks and the nearby igneous rocks have 
been converted to a white powdery calcite that on 
casual inspection appears to be a clay mineral. Locally 
this is veined by dense reddish opal. 

The most extensively explored ore body is that about 
700 feet northeast of hill 6081. This is in a small patch 
of sediments at their contact with the quartz monzo- 
nite. The ore body is a nearly flat tabular mass and 
appears to be a bedded replacement deposit extending 
outward on both sides of a nearly vertical north-south 
fissure. Copper minerals, for the most part copper 
pitch and chrysocolla, are concentrated along the 
fissure, but away from it the limestone bed appears to 
have been replaced chiefly by magnetite, which is now 
partly oxidized to "limonite" and nontronite. A 



hand sample of the magnetite is reported by Mr. 
Lamb to have assayed 0.96 ounce of gold to the ton, 
and he believes that most of the gold in the two 
shipments made from this deposit was also contained 
in magnetite. One shipment, said to be a carload, he 
reports to have carried $8 a ton in gold and 1V 2 per- 
cent of copper and the other, of 12 tons, $9 a ton in 
gold and 8 percent of copper. 

A different type of deposit is found to the southeast 
near the blacksmith shop, about 250 feet north of 
bill 6081. This is a thin quartz vein in quartz mon- 
zonite. It strikes N. 5° W. and is nearly vertical. 
The width varies, but the maximum observed was 14 
inches. The vein appears to be moderately persistent 
along both strike and dip, as it has been followed to 
a depth of about 50 feet by two vertical shafts 50 
feet apart, which did not reach its end. The vein 
filling consists of rather coarsely crystalline white 
quartz containing sporadic bodies of a black sulphide, 
which M. N. Short, of the Geological Survey, deter- 
mined to be an arsenical tetrahedrite. Less common 
are patches of galena. The tetrahedrite is for the 
most part altered to green and blue oxidation products. 
Mr. Lamb states that a shipment of 3 tons returned 
$300 a ton, largely in silver, at a time when that 
metal was selling at $1 an ounce. Specimens of the 
sulphide alone were said by him to run as high as 409 
ounces of silver to the ton. 

Northwest of these deposits two veins have been 
prospected east of hill 5882. Both are in quartz mon- 
zonite just below the contact with the sediments. 
The more northerly vein strikes N. 15° W. and dips 
55° W. It consists of sheared quartz monzonite im- 
pregnated with oxidized copper minerals, chiefly cop- 
per pitch and chrysocolla. Remnants of chalcopyrito 
may be seen in the copper pitch. The quartz monzon- 
ite in the hanging wall of the vein is iron-stained and 
streaked with white powdery calcite. A shipment 
thought to have been made from this prospect in 1918 
yielded 0.03 ounce of gold and 5.8 ounces of silver to 
the ton, 3.05 percent of copper, and 1.02 percent of 
lead. The second vein, about 100 feet to the south, 
strikes N. 60° W. and dips about 70° SW. As exposed 
it is 2 to 3 feet in width and is filled by arsenopyrite, 
almost completely altered to green scorodite with a 
relatively small content of quartz. No other metallic 
minerals were observed. 

The prospects north of hill 5882 lie along a jasperoid 
vein that follows a thin highly altered dike that cuts 
the sedimentary rocks. This vein is reported to carry 
about $1 a ton in gold. 

REA 

The workings on the Rea claim are on the floor of 
Accident Canyon just below the cabin at an altitude 
of 6,051 feet. In 1927 the claim was staked by Messrs. 
Parker & Hager, of Gold Hill, but at one time it was 
owned by the Brewer Gold & Copper Mim'ng Co. 



MINES AND PEOSPBCTS 



151 



The small amount of development work is reported to 
have been done about 1900. No shipments are known 
to have been made from this claim. 

The ore occurs along a fault between the Madison 
limestone and the Woodman formation. At the bot- 
tom of the canyon the fault strikes N. 55° E. and dips 
almost vertically, but a short distance up the side of 
the canyon where the Woodman formation is on both 
sides of the fault, the dip is much lower. (See pi. 
7, C.) The ore consists of veinlets and irregular masses 
of quartz and coarsely crystalline calcite, which have 
replaced the wall rocks and with which is associated 
silver-bearing tetrahedrite. Material rich in this sul- 
phide is said to have assayed 150 ounces of silver to 
the ton. Most of the ore now exposed is rather com- 
pletely oxidized, malachite and azurite being the two 
most abundant secondary minerals. 

CHEISTMAS MINING CO. 

The Christmas group of 12 patented claims is near 
the eastern border of the quadrangle a little over 2 
miles east-northeast of the Western Utah mine. So 
far as known, the company, whose headquarters is at 
Salt Lake City, has made only one shipment of ore, a 
lot of 11 tons produced in 1917 containing an average 
of 0.08 ounce of gold and 18.8 ounces of silver to the 
ton, 0.5 percent of copper, and 4,4 percent of lead. 

The claims cover a series of outcrops of the Oquirrh 
formation that are irregularly embayed by quartz mon- 
zonite. To the north the exposures of the Oquirrh 
formation are terminated by the eastward extension 
of the Pool Canyon transverse fault, north of which is 
the Prospect Mountain quartzite. Much of the sur- 
face in the vicinity is covered by the gravel slopes that 
extend down to the Great Salt Lake Desert. The 
Oquirrh formation in this region consists of metamor- 
phosed limestone and dolomite with some interbedded 
quartzite, which have been assigned to the central 
facies of the formation. 

Several prospect pits have been sunk in the western 
part of the group on quartz stringers that follow shear 
zones. The quartz contains local concentrations of 
galena and tetrahedrite, and these two minerals are 
also found embedded in the wall rocks. Considerable 
quantities of barite are also present in the walls of 
some of the veins. 

The main workings seem to have been about half a 
mile farther east, where a vertical shaft about 100 feet 
deep has been sunk in a small outcrop of the Oquirrh 
formation that is entirely surrounded by gravel. The 
shaft was sunk on a narrow quartz vein, in which galena 
and tetrahedrite are locally abundant. At the surface 
the ore appears to have been considerably oxidized. 

VHHS WI1E CAEBOSATl 01 STOPHATB MHIIEA1S HI f HE GAHtHJB 

TBOT 

The old Troy claim is on the east side of Rodenhouse 
Wash, about 2,000 feet south-southwest of the Climax 
mine. In 1926 it had been restaked by Perry Erickson 



and Amy Hicks under the name of Sam K. No. 1. 
The claim is underlain by quartz monzonite and covers 
the western part of a zone of quartz and quartz carbo- 
nate veins which are thought to mark a belt of reverse 
faulting in the quartz monzonite. (See pp. 89-90.) 
One of these veins striking N. 75° W. and dipping 
40° N., composed almost entirely of quartz in which 
are numerous fragments of altered quartz monzonite, 
has been rather extensively explored on the surface, as 
a result of the supposed discovery some years ago of a 
pocket of rich gold ore. Doubt as to the actual pres- 
ence of gold in the vein was expressed by some of the 
older prospectors in the district, as the time of dis- 
covery coincided with a period in which "high-grading" 
was prevalent at the Cane Springs and Alvarado mines. 
No other occurrences of gold ore are known from either 
this vein or other similar veins. Small specks of a 
mineral thought to be chalcopyrite were observed in 
a few specimens of the ore. 



IMMENSE 



The Immense claim, owned by P. H. Eobinson, 
encloses a large mass of jasperoid projecting into the 
quartz monzonite about 2,000 feet southwest of 
Minnehaha Spring. The jasperoid mass strikes nearly 
north and dips about 50° E. It appears to have been 
formed by a replacement of a projecting arm of the 
Oquirrh formation into the intrusive. No information 
was obtained regarding the presence of any valuable 
minerals in the jasperoid. 

AfiSENIC REPLACEMENT BODIES 
GOLD HILL MINE OP WESTEBN UTAH COPPBE CO. 

Location, history, and development. — The Gold Hill 
mine of the Western Utah Copper Co., sometimes 
called the Western Utah mine, hks produced a large 
part of the copper, lead, and arsenic ore credited to 
the Clifton district. It comprises a group of nine 
claims and fractions, more or less overlapping, that 
cover the northwest slope of Gold Hill, about 1% miles 
east of the post office. Two of the claims were among 
the first staked in the district and appear to have made 
a small production of gold ore and oxidized silver-lead 
ore. It is said that some placer mining was done on 
the hill slope also. The activity at the Alvarado and 
Cane Springs mines in the early nineties resulted in 
renewed activity on these claims, and some gold ore 
from them was treated at the Cane Springs mill. Then 
followed a period of inactivity until 1906, when title 
to the group of claims was taken over by the Western 
Utah Copper Co., of which Duncan McVichie, of 
Salt Lake City, was the guiding spirit. 

In the succeeding 10 years a considerable body of 
copper ore was developed above the 150-foot level 
and smaller bodies of lead-silver ore on a lower level. 
No ore was shipped in these years, however. Pro- 
duction began early in 1917, shortly after the com- 
pletion of the Deep Creek Railroad, the construction 



152 



GOLD HILL MINING DISTRICT, UTAH 



of which was largely effected by those interested in 
this mining company. 

Shortly thereafter control of the company passed to 
Frank G. Rowley, of Providence, R.I. After the first 
year lead surpassed copper in value in the ore shipped. 
The discovery that the ore contained a large percentage 
of arsenic resulted in the continued operation of the 
mine in the face of a decreasing content of silver, copper, 
and lead, and a considerable tonnage of arsenic ore was 
shipped from 1923 to 1925. Much of this ore was 
shipped at a flat rate per ton, without regard for its 
metal content other than arsenic. The drop in the 
price of arsenic early in 1925 resulted in the virtual 
shutdown of the mine and after a short period during 
which lead ore was shipped company work ceased 
and the production of the mine has since been confined 
to small shipments by lessees. 

Production from Western Utah mine, 1917-29 
[Figures furnished by C. N. Gerry, U.S. Bur. Mines] 



1917- 
1918_ 
1919_ 
1920_ 
1921_ 
1922, 
1923_ 
1924, 
1925- 
1926_ 
1927_ 
1928- 
1929_ 



Ore (tons) 



32, 023 

15, 893 

13, 787 

39, 297 

11,557 

74 

13, 049 

32 r 780 

12, 802 

122 

76 

145 

"33 



Gold 
(ounces) 



421. 00 

233. 99 

197. 33 

64. 70 

150. 24 

1.00 

7.00 

82. 50 

131. 60 

.90 

1. 30 

. 72 

1. 16 



Silver 
(ounces) 



150, 767 

86, 716 

49, 825 

83, 581 

22, 479 

819 

38, 487 

145, 034 

107, 480 

891 

345 

792 



Copper 
(pounds) 



1, 715, 189 

420, 610 

181, 786 

81, 928 

3, 172 

616 

28, 363 

3, 144 

48, 101 

1, 681 
1,033 

480 

2, 033 



Lead 
(pounds) 



371,418 
1, 062, 432 
652, 980 
958, 189 
329, 866 

4, 178 
254, 854 

1, 753, 698 

1, 659, 613 

22, 506 

5, 121 
42, 117 



• Dump ore. 

The amount of arsenic recovered from the ores is 
not definitely known, but it appears to have been 
between 7,000 and 8,000 tons of metallic arsenic. 

Two shafts, one vertical and one inclined, provide 
access to the deeper workings, on which the greater 
part of the mining was being done during the time of 
examination. Both of these have been sunk from the 
adit or 300-foot level, whose portal is at an altitude of 
5,579 feet. The vertical shaft is near the portal and 
is 400 feet deep. From the bottom of it the 700-foot 
level has been driven. (See pi. 15.) This level is also 
cut by the inclined shaft, which is 700 feet farther 
south. From the inclined shaft the 400, 600, and 760 
foot levels have also been driven. From the 760-foot 
level a winze about 150 feet deep has been sunk and a 
short drift, known as the 900-foot level, turned from 
it. Above the 300-foot level are several tunnels, 
designated on the mine maps as the 80-foot level, 
150-foot level, etc. Only one of these, the 150-foot 
level, is at present extensive. The remainder have 
been largely destroyed by the caving operations in the 
glory hole that now marks the original outcrop. 

Geology. — The geology in the vicinity of the mine is 
epitomized by plate 14, which is in brief a series of 



interconnected plans and longitudinal and cross 
sections. 

The oldest of the formations shown in this diagram 
and also the most important economically is the Ochre 
Mountain limestone, which in most places forms the 
walls of the ore bodies. On the surface, north of the 
300-foot level portal, the limestone is thick-bedded, 
white, and recrystallized. South of the tunnel portal 
and in most of the exposures underground much of the 
limestone has been either altered to silicate minerals 
or partly replaced during the oxidation of the ore 
minerals. White bladed wollastonite is the most 
common of the silicate minerals, but a greenish-brown 
garnet is also widely distributed. In some places 
diopside and zoisite are locally abundant. In many 
places, however, crystalline limestone may be found 
in close proximity to the ores, and such specimens of 
this as were tested proved to be remarkably free from 
impurities. The limestone beds have a rather constant 
northwest strike. Near the surface they dip steeply 
to the east or even vertically, but on the lower levels 
of the mine the dip is 45° or less, because of the ap- 
proach to a synclinal axis to the east. (See p. 77.) 

The next younger formation near the mine is the 
Manning Canyon formation, which occupies the 
eastern slope of the ridge beneath which lie the mine 
workings. It is made up of dark quartzite and black 
shale and is not exposed underground. 

Between the Manning Canyon formation and the 
Ochre Mountain limestone there is a wide belt of 
jasperoid that has been called in previous reports 
quartzite or silicified limestone. It is reddish brown 
on weathered surfaces and forms the prominent jagged 
outcrops that make up the ridge line. Much of the 
rock has the appearance of a breccia, owing to the 
presence of several generations of quartz, each of 
which has a slightly different texture and color. Vugs 
lined with crystalline quartz are common, and in 
several places green chalcedony and plates of barite 
are present. In a few places fragments of limestone 
were^ found embedded in it. Thin sections show that 
the rock has a typical jasperoid texture, and this, 
together with the megascopic evidence, leaves little 
doubt that the rock is the result of replacement by 
silica along the limestone-shale contact. Butler 67 sug- 
gested that the contact was a fault, and the evidence 
indicating that it is one is mentioned on page 77. 
The thickness of the jasperoid is not exactly known. 
As shown on plate 14, it appears to be in excess of 100 
feet, but this figure may be too large by reason of the 
difficulty in determining the exact location of the 
debris-covered contact with the Manning Canyon 
formation. 

Underground the continuation of the surface expo- 
sure of the jasperoid is seen on the 300- and 700-foot 

« Butler, B. S., The ore deposits of Utah: U.S. Geol. Survey Prof. Paper 111, 
p. 481, 1920. 



U. S. GEOLOGICAL SURVEY 



• • • * • I 



*V 



\ 















t... .f;'. 






- *.--; v. ■ . 







"<<-. ^u*" 



# ( *"~- 






& . 




~~''\\, 






* a.- 



wr -,■ 
M.- 



1 * V. .. £.'■ ■■•■■' 




Manning Canyon 
formatior 




m 



Ore and 

gossan 



m nnu nufiPAM np rjim htt i a/ttktf nir> wfcnn^Dvr tttad /-i/w^nr* ,-«-. 



PROFESSIONAL PAPER 177 PLATE 14 




* |J 



„***#? 



Jr bp * ■ 



1 > , 'tis ..,..,. ^ • * , J 

* .<•- ... V -• '•-•- . I 










^rt>&KS 







•><3 



EXPLANATION 



KSMJ 



Manning Canyon Ochre Mountain 
formation limestone 






t- > V < : 

I- > A > 



Quartz 

monzonite 



xS$g 



nq 




I x x x x x I 

L v X x x *' 

K x*x X x x 

IX X X X X X: 



Ore and 



•'Quartz Quartz monzo- Jasperoid 



7 -,;f * * x J! 



\"% 



■s^ 



-rfsfc-- 



IjUT 
II ; -ittl"-' 11 



rf ,# fl 






^^^^mmmvmmm 



f 



lfii.K'' 










EXPLANATION 



ov77^ 



Manning Canyon Ochre Mountain 
formation limestone 



1- 


> 


V 


< 


L 


A 




V 


U 


> 


A 


> 



Quartz 



\ 



Ore and 

gossan 




Quartz 
vein 



X X X X X 
w x X X X X 

X X X X X 
XX X XXX 



Quartz monzo- 
nite porphyry 



Jasperoid 



BLOCK DIAGRAM OF GOLD HILL MINE OF WESTERN UTAH COPPER 



V.B. GEOLOGICAL SURVEY 



PROFESSIONAL PAPBR 177 PLATE IS 







MINES AND PBOSPECTS 



153 



levels. On both levels the rock was cut by the east- 
erly crosscuts from the vertical shaft. On the 300-foot 
level only a small amount of the jasperoid was pene- 
trated by the crosscut before a drift into the footwall 
limestones was started. On the 700-foot level, how- 
ever, the contact of the jasperoid with the limestone 
was followed for several hundred feet. Here the con- 
tact is extremely sharp. The strike is N. 35°-55° W. 
and the dip 35°-45° E. The dip of the jasperoid, 
like that of the limestone beds, must decrease down- 
ward, for the average dip obtained by connecting the 
exposures on the 300-foot and 700-foot levels is 60° E., 
and at the surface the dip is even steeper. 

Smaller masses of jasperoid are also found both on 
the surface and underground. On the surface a short 
spur from the main mass extends northwesterly from 
the mineral monument on peak 5901. On the 300-foot 
level similar material containing abundant residual 
calcite is found in the easterly crosscut north of the 
main ore body. This is directly beneath the spur on 
the surface and may be a continuation of it. Also 
on the 300-foot level typical jasperoid containing barite 
and some oxidized copper minerals has been developed 
at the contact between quartz monzonite and limestone 
near the end of the long combined drift and crosscut 
west of the ore body. Similar relations were observed 
on the 600-foot level. There appears to be a close 
relation between this contact jasperoid and the quartz- 
tetrahedrite veins in the limestone nearby. In these 
two places part of the jasperoid appears to have 
replaced quartz monzonite, rather than limestone. 

Quartz monzonite occupies the largest area in the 
vicinity of the mine. It shows no unusual features 
here. Underground much of the rock is seen to be 
altered, rarely to jasperoid as noted above, or widely 
to a quartz-sericite-calcite aggregate, in which the 
outlines of the old crystals, particularly the feldspars, 
are commonly preserved. 

The quartz monzonite is a part of the main Gold 
Hill stock and almost completely surrounds the block 
of sedimentary rocks in which the mine is located. 
North of the open cut it has a rather regular contact 
with the Ochre Mountain limestone, which strikes' 
more northwesterly than the jasperoid, with the result 
that the width of the limestone outcrop increases to 
the north. South of the open cut, however, the igne- 
ous rock cuts off the limestone and at the surface 
is in contact with the jasperoid. The termination of 
the limestone is not the result of the convergence in 
strike of the jasperoid and the limestone and quartz 
monzonite contact but is rather accomplished by the 
penetration of the limestone by three blunt wedge- 
shaped dikes of the igneous rock. 

The most westerly of these dikes is the widest at 
the surface and appears to widen rapidly downward. 
The dip of its eastern or hanging-wall side, however, 
is greater than the average dip of the jasperoid, so 

38811-35 — u 



that limestone is exposed on the bottom levels of the 
mine directly beneath places on the surface where 
the intrusive is in contact with jasperoid. This same 
conclusion may be reached from the fact that lime- 
stone is found in the long Ida Lull tunnel, to the south. 

The middle dike is about 30 feet wide at the surface 
and ends northward somewhere within the open cut. 
Near the surface it dips steeply to the east, but between 
the 300- and 400-foot levels it is nearly vertical, and 
below the 400-foot level it must reverse its dip and join 
the larger mass to the west. 

The third dike is narrower than the other two. It 
ends bluntly on the northeast side of the open cut. 
A dike of similar width and position was recognized 
on the 300-foot level but was not traced confidently 
below it. On the 700-foot level a narrow dike that 
may be its continuation was found, but the gap be- 
tween them was too great to warrant their connection 
on plate 14. If the two are actually the same, the 
dip must steepen to nearly vertical in the intervening 
distance. 

The contact of the quartz monzonite with the east 
side of the sedimentary block is a westward-dipping 
fault. These relations are similar to those at the 
U.S. mine, but here the dip of the fault is so steep that 
there is no danger of its terminating the ore zone 
downward. 

Another locality in which quartz monzonite is ap- 
parently exposed is in the south end of the 700-foot 
level in the hanging wall of the ore body, where a 
somewhat iron-stained rock of granitic appearance is 
found. A thin section of this rock showed that it was 
chiefly composed of a pale-green pleochroic amphibole 
and colorless humite, together with minor amounts of 
pleochroic apatite, titanite, iron oxides, and quartz. 
The rock is thus obviously a product of metamorpbism, 
and it is not at all clear from the meager exposures 
whether or not it was originally a sedimentary or an 
igneous rock. Similar mineral assemblages have been 
found in other places in both sedimentary and igneous 
rocks. 

A dike of quartz monzonite porphyry is exposed 
both on the surface and on the 150- and 300-foot levels. 
Megascopically, the rock is dull greenish gray or light 
green and at the surface is dotted with brown limonite 
pseudomorphs after pyrite. Rectangular phenocrysts 
of dull feldspar as much as a quarter of an inch long 
are abundant but in most places are not conspicuous 
because of the prevailing light color of the rock. 
Smaller, irregular phenocrysts of quartz and a few 
glistening areas of white mica can also be recognized. 
Under the microscope the rock is found to be consid- 
erably altered. The feldspar phenocrysts have been 
entirely replaced by calcite and sericite; the mica, 
which was originally biotite, has gone over to sericite 
and chlorite and is locally crowded with sagenite 
(rutile) needles that have the characteristic stellate 



154 



GOUD HILL MINING DISTRICT, UTAH 



arrangement; and the quartz phenocrysts show a slight 
veining by sericite. The groundmass is a finely crys- 
talline aggregate of calcite, sericite, and quartz. 

In the vicinity of the mine the dike in places is near 
the contact between the sedimentary rocks and the 
intrusive, and the exposures are in general rather poor. 
For these reasons, and possibly also because of the 
local enlargement of orthoclase crystals in the quartz 
monzonite itself, some of the previous observers have 
considered, the dike to be a porphyritic marginal facies 
of the main intrusive. That it is a separate intrusion, 
however, is shown by the distinctive texture, linear 
trend, and independence of the sedimentary contact 
except near the mine. As the dike is followed to the 
south, it is found to be enclosed within the main in- 
trusion, and three-quarters of a mile south of the open 
cut apophyses from the dike extend into the walls of 
quartz monzonite. 

Near the mine the dike strikes nearly north and dips 
45° or less to the west. Unlike the quartz monzonite, 
it is not susceptible to silieification and therefore 
appears to cut through the jasperoid without alteration 
(see pi. 14), although the jasperoid was undoubtedly 
formed at a later time. 

Another dike was found at the south end of the 
400-foot level, but it was not recognized elsewhere in 
the mine and is not shown on plate 14. It is a fine- 
grained pale-gray rock in which are scattered rectan- 
gular crystals of calcite 1 millimeter long and a few of 
quartz. A thin section showed that the matrix con- 
sisted of fine-grained quartz and feldspar partly 
replaced by calcite and sericite. The calcite crystals 
probably represent former feldspar phenocrysts. The 
rock is too much altered to permit determination of 
its original composition. 

Ore bodies.— Three kinds of ore bodies are present 
in the mine — veins with silicate gangue, quartz- 
tetrahedrite veins, and large replacement deposits 
valuable chiefly for their arsenic content. 

Veins with silicate gangue: In the central of the 
three limestone wedges extending southward from the 
open cut there are several prospect holes on an altered 
limestone bed paralleling the eastern contact. The ore 
is similar to that at the Alvarado and Cane Springs 
mines, consisting chiefly of silicate minerals, especially 
wollastonite, that have replaced the limestone, to- 
gether with small amounts of oxidized copper minerals 
and native gold. It is reported that the earliest work 
in the district was done on this deposit. So far as 
known it was last worked in 1892^95, when some ore 
was milled at the then active Cane Springs mill. No 
information is available as to the grade of ore mined, 
but the amount must have been comparatively small. 

Quartz- tetrahedrite veins: On the 150- and 300-foot 
levels a quartz vein containing copper minerals is 
found in the limestone immediately west of the arsenic 
ore bodies and a few feet east of the quartz monzonite 
contact. Both exposures strike a little east of north 



and dip to the east. If the two are the same, as seems 
probable, the vein must cut across the quartz monzo- 
nite porphyry dike, as shown in plate 14. A similar 
quartz vein at the surface near the west wall of the 
open cut is probably the upward extension of the 
exposures underground. The vein ranges in thickness 
from a foot or less to about 30 feet on the 300-foot 
level, but the average thickness and the one most 
commonly found is about 5 feet. On the 300-foot 
level the vein appears to terminate southward and its 
place to be taken by a zone of jasperoid in which copper 
minerals are disseminated. The contact between the 
two, however, is not exposed by the mine workings. 
Several small faults cross the vein on both levels and 
and offset it as much as 10 feet. The vein filling con- 
sists of coarsely crystalline white glassy quartz in 
which are numerous inclusions of altered wall rock. 
Disseminated through the quartz are specks and small 
blebs of pyrite and an arsenical tetrahedrite. The 
tetrahedrite in many places has been altered to a 
black sooty chalcocite, and films of chrysocolla, mala- 
chite, and azurite are found throughout the quartz. 
The quartz vein itself does not appear to have been 
mined at any place, but, to judge from the character 
of the two lower arsenic ore bodies, the higher copper 
content of the upper one (now represented by the open 
cut) must have been largely the result of oxidation 
and transportation of copper minerals originally 
present in this quartz-tetrahedrite vein. 

Arsenic replacement ore bodies: Three distinct 
arsenic-rich ore bodies have been developed in the 
mine. The first of these to be explored extended from 
the surface to the 150-foot level, being terminated 
downward by the dike of quartz monzonite porphyry. 
The middle deposit was found beneath the dike on the 
150-foot level and was followed downward to a few 
feet below the 400-foot level, where it appears to have 
been ended by the reversal in dip of the middle of the 
threte wedges of quartz monzonite. The third ore body 
was found about 50 feet above the 600-foot level, 
below the quartz monzonite, and has been followed to 
the lowest workings. 

The outlines of the upper ore body are roughly 
those of the open cut although, as shown on plate 14, 
there is a triangular cropping of gossan extending 
northward beyond the pit. At the surface the pit has 
a length of 300 feet and a width of nearly 200 feet, and 
these dimensions are probably only slightly greater 
than the ore-bearing zone. 

The middle ore body on the 300-foot level is nearly 
circular, with a diameter of nearly 100 feet. On the 
150-foot level the shape is similar but the dimensions 
are somewhat larger. On the 400-foot level, however, 
the circular form has changed to a tabular one, with a 
length of about 150 feet and a width of 10 to 30 feet. 

The lower ore body on the 600-, 700-, and 760-foot 
levels has a pear-shaped section with the bulbous end 
to the south. The maximum length of this lower ore 



MINES AND PROSPECTS 



155 



body is somewhat over 200 feet, and the maximum 
width in the enlarged southern portion is nearly 100 
feet. On the 760-foot level there are two northerly 
prongs to the wider south end of the ore body, rather 
than a single one, as on the 600- and 700-foot levels. 
On this level, too, several faults displace the boundaries 
not more than 5 feet. A similar split in the ore body 
and minor faults are also indicated by the meager 
exposures on the 900-foot level. The apparent locali- 
zation of these two phenomena on the two lower levels 
is probably due to the fact that the ore bodies on the 
higher levels are thoroughly oxidized, and during the 
process of oxidation sufficient quantities of material 
have migrated through the original walls to mask the 
former position effectually. 

The location of the ore shoots is controlled by sev- 
eral factors. All the ore bodies when traced north- 
ward are found to be in beds of crystalline Ochre 
Mountain limestone. The easy replaceability of this 
rock makes it the most important single cause of ore 
localization. Obviously, anything that limits the lime- 
stone must also be considered as a factor. The quartz 
monzonite porphyry dike and the wedge of quartz 
monzonite that cut the limestone have clearly been 
unfavorable for ore deposition, as is shown by their 
lack of strong mineralization adjacent to the ore bodies. 
In a similar way the alteration of the limestone to 
lime-silicate rock has been a negative factor in ore 
deposition, for this rock also must have been essentially 
immune to attack by the ore-forming solutions. On 
the 760-foot level, for example, lime-silicate rock occu- 
pies the space between the two northern prongs of the 
ore body. It also forms the walls of the ore in several 
places on higher levels. 

Two more direct factors in localizing the ore are 
suggested by the present exposures in the mine, but 
neither could be definitely proved because of the exten- 
sive surficial alteration. One is Assuring within and 
essentially parallel to a favorable limestone bed. This 
is illustrated on the 760-foot level by the occurrence of 
a pronounced sheeted zone that forms the footwall 
of the ore body and separates it from crystalline 
limestone. Unless a preliminary fracturing of the 
limestone were favorable or even necessary for ore 
deposition, there would appear to be no reason for the 
sharp contact observed between the barren, unfrac- 
tured limestone and the ore. The other factor is 
largely hypothetical. Plate 14 shows that the ore 
bodies individually and as a group pitch to the south- 
east, and that on several levels, particularly the lower 
ones, the south ends of the ore shoots are blunt and 
much wider than the north ends. These features sug- 
gest that there is some sort of a controlling or limiting 
fracture at the south ends of the ore bodies that 
strikes about at right angles to the ore and dips to the 
south. A fracture of this description appears to limit 
the ore southward on the 760-foot level but could not 



be recognized on the higher levels, where the ore is so 
thoroughly oxidized. Billingsley has reported that the 
upper ore body, now inaccessible, was controlled by a 
northeasterly fracture that dips to the northwest. 68 
This fracture obviously has not affected the two lower 
ore shoots, and this may mean that there is more than 
one cross fracture that controls the ore. 

The three kinds of ore that have been mined from 
the large ore bodies — copper, lead-silver, and arsenic — 
have all been almost completely oxidized. Eemnants 
of sulphides were found in several places on the 700- 
foot level, but the 760-foot level was the only one on 
which the relations of the sulphides to one another 
could be adequately studied. The west prong of the 
ore shoot on this level is composed almost entirely 
of arsenopyrite, and the east prong is made up of a 
mixture of sulphides in which pyrite greatly predomi- 
nates and arsenopyrite is extremely rare. Farther 
south, partial oxidation masks the relations between 
the two types of ore, but there seems to be a gradual 
intermixture. 

The arsenopyrite in the western prong has locally a 
radiating habit, but the great part of it is apparently 
massive and without crystal habit, a feature that 
polished sections show to be the result of a thorough 
brecciation on a small scale. Much of this ore con- 
tains little except the arsenopyrite. Near the hanging 
wall of the prong, however, euhedral crystals of arseno- 
pyrite occur in a gangue of coarsely crystalline calcite; 
and near the south end of the ore body there is abun- 
dant fine-grained quartz, which has replaced both the 
calcite and arsenopyrite. The attack on the sulphide 
was most intense in the central portions of the crystals, 
and in many places the arsenopyrite remaining is sim- 
ply a thin shell around a core of quartz. 

In the eastern prong arsenopyrite is either absent 
or is found only as widely scattered crystals. Pyrite 
is by far the most abundant sulphide in this portion 
of the ore body. It is veined by varying but usually 
small amounts of pyrrhotite, sphalerite, chaleopyrite, 
and galena. Pyrrhotite is especially abundant in the 
ore on the 900-foot level. Calcite and quartz are 
sparse gangue minerals. At the south end of the ore 
body, where this assemblage of sulphides joins with 
the arsenopyrite ore, the arsenopyrite has been veined 
and replaced by them. 

The oxidized arsenic ore above the 760-foot level 
consists chiefly of the hydrated ferric arsenate, scoro- 
dite, and iron oxides. Its appearance varies greatly 
from place to place, depending on the amount of iron 
oxides present and the presence or absence of crys- 
tallinity in the scorodite. If iron oxides are absent 
from the ore, the color may be either white or green. 
The white material is shown by the microscope to be 
amorphous or cryptocrystalline matter in which collo- 

88 Bfllingsley, Paul, Notes on Gold Hill and vicinity, Tooele County, Utah: 
Boon. Geology, vol. 13, p. 289, 1918. 



156 



GOLD HILL MINING DISTRICT, UTAH 



form textures are well developed. This material 
grades rather sharply into fine-grained crystalline green 
scorodite. Increase in the size of the scorodite crys- 
tals does not appear to affect the color greatly. A 
brown color is characteristic of most of the ore and is 
caused by the presence of small flakes of iron oxide. 
There appear to be all gradations of mixtures between 
pure scorodite and pure iron oxide (goethite?). Al- 
though these two minerals are largely confined to the 
space once cocupied by sulphides, in many places the 
lime-silicate wall rock has been veined and impregnated 
by them. 

In addition to these two minerals, arseniosiderite 
and jarosite were recognized in several specimens, and 
pharmacosiderite is reported to be locally present. 
The green copper arsenate, conichalcite, was found in 
the stopes above the 400- and 600-foot levels, and W. 
F. Foshag has identified the similar minerals, olivenite 
and clinoclasite. The zinc arsenate adamite was found 
in hairlike crystals in the open cut. Halloysite and 
another clay mineral of similar appearance but aniso- 
tropic occur throughout the ore, and manganese, proba- 
bly entirely in the form of wad, is in many places 
associated with them. 

The copper ore was found almost entirely in the 
upper ore body and has now been completely stoped. 
From the descriptions of Butler 89 and Billingsley ™ 
the ore probably consisted of copper arsenates and 
carbonates in a gangue of iron oxides and scorodite. 
The copper content of the ore was close to 3 percent." 
The writer considers it probable that the bulk of this 
copper was derived from the quartz-tetrahedrite vein 
that is now exposed on the west side of the open cut. 
The reasons for this view are, first, that no similar 
concentrations of copper were found in either of the 
two lower ore bodies, although they are otherwise 
similar mineralogically, and second, that the quartz- 
tetrahedrite vein was not recognized below the 300- 
foot level. 

Lead-silver ore has been found in a number of places 
from the surface down to the 760-foot level, as small 
lenses within the arsenic ore. There appears to be a 
strong tendency for such lenses to be situated either at 
the south ends of the ore shoots or near the hanging 
wall. A fine-grained powdery yellow-brown or greenish- 
brown material that appears to be made up of varying 
proportions of plumbo jarosite and beudantite is the 
principal source of lead. Smaller quantities of mime- 
tite, anglesite, and cerusite have also been found in the 
gangue of scorodite and iron oxides. 

A rather unusual assemblage of minerals was found 
at the south end of the 760-foot level and also at the 
bottom of the two south winzes from the 700-foot level. 



« Butler, B. 8., The ore deposits of Utah: U.S. Geol. Survey Prof. Paper 111, 
p. 481, MHO. 

" BilMngdey, Paul, Notes on Gold Hill and vicinity, Tooele County, Utah: Econ, 
Geology, vol. IS, p. 286, 1918. 

n Butler, B. S., op. eit„ p. 481. 



At both of these places the bottom of the zone of sur- 
ficial alteration is exhibited. In addition to minerals 
found both in the unaltered sulphide ore and in the 
completely oxidized ore, mareasite, chalcocite, super- 
gene arsenopyrite in tiny crystals upon iron oxides, 
native sulphur, and abundant gypsum were recognized. 
Siderite appears to be rather widely developed at this 
horizon, not only at the two points cited but also 
north of the ore body on the 760-foot level. It closely 
resembles the smithsonite found in other western min- 
ing districts, but qualitative tests showed that it con- 
tained only a trace of zinc. Mr. Tiffany, who was in 
1925 superintendent of the mine, informed the writer 
that small quantities of native copper, orpiment, and 
realgar had also been found at this level. 

GOLD HILL MINE OP UNITED STATES SMELTING, BJEFHriNG A 
MINING CO. 

Location and development, — The mine of the United 
States Smelting, Refining & Mining Co. is called by the 
company the Gold Hill mine but in the district is 
always spoken of as the U.S. mine to distinguish it 
from the Gold Hill mine of the Western Utah Copper 
Co. It is about 3,500 feet south of Gold Hill post 
office, east of the Lincoln Highway. The original 
claim, the Last Dollar, was developed by J. J, Gerster 
and in 1923 yielded a small shipment of copper ore. 72 
In that year, however, a vertical shaft was sunk on 
the 3 claim and passed through 42 feet of scorodite ore 
that contained from 2 to 15 percent of arsenic. The 
Grasselli Chemical Co. obtained an option on the claim, 
but a continuation of the shaft disclosed* 30 feet of 
massive arsenopyrite, below which was found a mixture 
of arsenopyrite, galena, pyrite, and sphalerite in a 
quartz gangue. 72 The United States Smelting, Refining 
& Mining Co. about this time took over the option 
from the Grasselli Chemical Co. and continued the 
development work on the Last Dollar and adjacent 
claims. In 1924 this company mined about 10,000 
tons of ore. Some of it averaged 38 percent of arsenic 
in carload lots, but the general average was 25.8 per- 
cent of arsenic, 30 percent of insoluble matter, 20 
percent of iron, 12 percent of sulphur, 0.5 percent of 
Mme, 0.4 percent of zinc, 0.02 percent of copper, and 
0.86 percent of lead. Gold amounted to 0.03 ounce 
and silver 1.6 ounces to the ton. In addition several 
carloads were shipped that contained 10 to 16 ounces 
of silver to the ton and 6 to 13 percent of lead. These 
lots averaged 7 percent of arsenic. 73 In 1925 arsenic 
ore of similar composition was shipped during Janu- 
ary and February, but the drop in the price of arsenic 
prevented any further shipments. In that year, in 
addition, a carload of lead ore was shipped that con- 
tained 10.8 percent of lead; and in 1926 lessees shipped 
10 cars of similar ore reported to have averaged about 
12 percent of lead and 15 ounces of silver to the ton. 

» Heikes, V. C, U.S. Geol. Sorvey Mineral Besourcea, 1923, pt. 1, p. 187, 1927. 
» Heikes, V. C„ U.S. Bur. Mines Mineral Besourues, 1924, pt. 1, p. 41, 1925. 



MINES AND PKOSPECTS 



157 




The principal workings at the mine (fig. 29) include 
a crosscut tunnel to the ore body, which is the chief 
means of access, This adit connects with about 800 



feet of drifts and crosscuts that constitute the tunnel 
level. About 20 feet above this level is another series 
of workings known as the working level, but a larger 



158 



GOLD HILL MINING DISTRICT, UTAH 



part of it is no longer accessible owing to stoping. In 
the vertical shaft that extends from this level to the 
surface the original discovery was made. An inclined 
shaft extends downward from the working level and 
ends at the 234-foot level, on which nearly 700 feet of 
work had been done in 1927. 

Geology. — Five formations are exposed in the vicinity 
of the mine. The oldest is the Ochre Mountain lime- 
stone, which crops out at the surface east of the portal 
of the adit and also to the north near benchmark 5416. 
It is a continuation of the outcrop in which the Cane 
Springs mine is k>eated. Almost all the mine workings 
are in this limestone, although in most of them meta- 
morphism and ore deposition have completely altered 
its original aspect. In the surface exposures as well as 
in the adit tunnel east of the quartz monzonite, the 
formation appears as a bleached and recrystallized 
coarse-grained limestone in which bedding planes are 
distinguished with difficulty. Silicate minerals are 
locally present in some beds. On the 234-foot level, 
east of the ore body, the limestone appears to have 
been almost completely replaced by pale-green garnet. 
In other places adjacent to the ore body, however, 
the limestone has been altered to a fine-grained pale- 
gray jasperoid. This rock at the surface weathers to 
a reddish-brown resistant rock that forms prominent 
outcrops. 

The Ochre Mountain limestone is overlain by the 
Manning Canyon formation, consisting of black shale 
and dark quartzite. The beds of quartzite are the 
only ones that are exposed at the surface, and in places 
where the Ochre Mountain limestone has been silicified 
it is difficult to locate the contact between them 
exactly. Small patches of the formation are exposed 
underground that show the black shale characteristic 
of the formation. In the exposures of the contact 
between the Manning Canyon and the Ochre Moun- 
tain limestone at the north end of the tunnel level and 
at the 234-foot level there is evidence of faulting, but 
from the essential concordance between the two for- 
mations on the surface, the faulting is thought to have 
been relatively slight. 

The Oquirrh formation is exposed south of the mine 
workings. It is made up of moderately thin bedded 
quartzites and limestones, some of the limestones 
silicified. It is not exposed underground. It is 
separated from the two preceding formations by a 
normal fault striking north of east. The beds that 
crop out just south of this fault must be near the base 
of the formation, for the fault is exposed at the south 
end of the tunnel level, and here the Manning Canyon 
formation is found in the hanging wall. 

The next younger formation is the quartz monzonite. 
It underlies the gulch west of the adit portal and is 
part of a bulbous outcrop that is connected with the 
stock by a narrower mass extending to the south. 
The main mass of the stock is exposed about 850 feet 



east of the adit portal on the eastern slope of the ridge 
and also about an equal distance to the north. A 
narrow dike of similar character crops out along the 
road leading to the old vertical shaft and is approxi- 
mately at the Ochre Mountain and Manning Canyon 
contact. The intrusive is also exposed at several 
places in the mine workings. In the adit it is found 
for a distance of 150 feet from the portal. This is a 
part of the body exposed in the gulch below the mine. 
At the contact with the Ochre Mountain limestone 
there has been a slight copper mineralization on the 
south side of the adit. On the 234-foot level quartz 
monzonite was struck about 60 feet south of the shaft 
crosscut and continued to the end of the drift. A 
raise near the end passed through the igneous rock in 
about 20 feet. The intrusive is also present in the 
northern workings. What appears to be the top of 
a dikelike mass was cut about 30 feet east of the 
massive sulphides, and at the end of this same cross- 
cut another mass was found. The latter mass is 
separated from the sedimentary rocks by a fault with 
low southwesterly dip that is without doubt the same 
as one exposed at the surface east of the ridge above 
the mine workings. The quartz monzonite observed 
underground is all more or less altered. That on the 
tunnel level has been partly replaced by a later gener- 
ation of orthoclase and quartz, and the dark minerals 
have been altered to actinolite, calcite, chlorite, and 
titanite. Moderate amounts of sericite are also found. 
On the bottom level dark silicates such as garnet and 
diopside have replaced the rock, and in the southern 
part of the level it is difficult to draw the contact with 
the metamorphosed limestone. The northern ex- 
posures are somewhat less altered but are badly crushed 
and contain veinlets of a pink ferruginous dolomite. 

The youngest rock formation exposed is a quartz 
porphyry dike 2 feet thick that is seen in the adit. It 
has been highly altered and is now a soft pale-gray 
fine-grained rock in which are phenocrysts of quartz 
as much as a quarter of an inch in diameter and of 
feldspar that reach a length of nearly an inch. The 
microscope shows that the matrix is composed of laths 
that were probably at one time plagioclase crystals 
but are now made up of a fine-grained clay mineral. 
The interstices between the laths are composed of 
another clay mineral that has a lower index of refrac- 
tion and a much lower birefringence. A little sericite 
and a few crystals of zircon and apatite are also present. 
This same dike appears to be exposed at the surface 
near the prospect hole 200 feet northeast of the adit 
portal. 

The Ochre Mountain limestone and the Manning 
Canyon formation, being essentially conformable, 
both strike west of north and dip 60° E. They are 
separated from the Oquirrh formation to the south by 
a normal fault that strikes north of east and dips south. 
This fault also is exposed in the most southerly work- 



MINES AND PROSPECTS 



159 



ings on the tunnel level, where the dip is seen to be 60°. 
It is of some economic importance in that it terminates 
on the south the beds of the Ochre Mountain limestone 
that contain the ore. 

A fault that is of much greater economic importance 
however, is the one cut near the end of the most east- 
erly workings on the 234-foot level. This separates 
the sedimentary rocks from the main mass of quartz 
monzonite exposed east of the mine. On the bottom 
level the fault, along which there is nearly 4 feet of 
gouge, strikes N. 65° W. and dips 35° SW., but the 
trace of the fault on the surface indicates that its 
average strike must be closer to N. 25° W. For the 
reasons given on page 76 in the discussion of the 
structure of this part of the quadrangle, the fault 
probably has normal relations. If this is so, the fault 
must terminate the ore-bearing portion of the Ochre 
Mountain limestone at a rather shallow depth below 
the 234-foot level. From its average strike and a dip 
of 35°, it should be found about 200 feet below the 
bottom of the inclined shaft. Furthermore, the fact 
that quartz monzonite forms the footwall of the fault 
at the surface indicates that the faulted portion of 
the limestone has been eroded away. 

A similar fault is exposed on the 234-foot level about 
150 feet in the hanging wall of the fault just described 
which cuts off the massive sulphide ore. This fault 
strikes N. 40° W. and dips 40° W. in the short drift 
and strikes N. 50° W. and dips 50° W. in the main 
crosscut. Projecting the Ochre Mountain and Manning 
Canyon contact that is exposed in the footwall of the 
fault, on the south end of the tunnel level, and the 
same contact exposed in the hanging wall, on the 234- 
foot level, indicates that the dip slip approximates 
100 feet (fig. 30). 

The fact that the several exposures of quartz mon- 
zonite on the 234-foot level are not represented at the 
surface raises a question as to the probable abundance 
of the intrusive rock on still lower levels. Quartz 
monzonite forms the footwall of the fault exposed in 
the northeasterly workinp on the 234-foot level, and 
the low dip of the fault must cause a rapid encroach- 
ment upon the ore-bearing limestone in depth. In 
addition, the southeastern continuation of the block 
of sedimentary rocks in which the mine is located 
shows conclusively that it is a part of a roof pendant 
in the quartz monzonite and that it is underlain to the 
southeast at a shallow depth by the intrusive. The 
Western Utah mine at Gold Hill, however, proves 
that such pendants may locally have a very consider- 
able depth in proportion to their width. Proximity to 
the bottom of a pendant, as at the Alvarado mine and 
in the country to the north, seems to be indicated by 
an abundance of small plugs and dikes of monzonite. 
In one sense the two exposures of intrusive rocks on 
the 234-foot level, neglecting that in the footwall of the 
eastern fault, could be interpreted as suggesting such 



proximity. On the other hand, they might be corre- 
lated with the dike on the surface that approximately 
follows the contact between the Ochre Mountain lime- 
stone and the Manning Canyon formation. This dike 
cannot be traced southward to the region of the mine 
workinp, and its top is presumably below the surface 




in that direction. The more northerly of the two ex- 
posures underground might thus be interpreted as the 
top of the dike at that point, and the larger southerly 
exposure as a part of the dike that here extends more 
nearly to the surfaee but does not quite reach it. The 
only evidence in favor of this view is that the three 
are more or less in alinement, but considerably more 



160 



GOLD HILL MINING WBTKICT, UTAH 



extensive mine workings would be necessary to prove 
it. In figure 30 this interpretation has been accepted, 
and the dike is shown as being offset by the fault that 
terminates the sulphides, on the assumption that the 
fault is of the same age as that to the east which cuts 
the igneous rock. 

Several small faults can be recognized on the tunnel 
level by reason of the displacement of the quartz 
porphyry dike. At least four faults cut the dike in the 
25 feet between the two drifts that branch from the 
adit. The displacements are all small, and their 
algebraic sum is equal to zero, for the dike has the 
same position east of the fault zone as west of it 
(fig. 30). The largest throw appears to be along the 
so-called "lead fissure," and adjacent to it the dike 
changes its strike nearly 90°, becoming approximately 
parallel to the fault. Other fractures were recognized 
at different points underground, but the absence of any 
distinctive horizon in the beds cut by them prevented 
any estimate of their importance. To judge from 
surface exposures, however, their throws must be 
slight. 

Ore body. — The ore body of the mine is a replace- 
ment deposit in a belt of Ochre Mountain limestone 
which is at least 100 feet wide and whose eastern 
boundary appears to be the contact with the Manning 
Canyon formation. The limits of the ore are not well 
defined except where quartz monzonite or a later fault 
is adjacent. On the tunnel level arsenic or lead- 
arsenic ore extends for more than 300 feet along the 
strike of this zone and for nearly 100 feet normal to 
the strike. The width appears to be at a maximum 
to the south and decreases to the width of the "lead 
fissure" at the north. On the 234-foot level the 
exposed mineralized area has considerably smaller 
dimensions. Nearly solid sulphides were cut for a 
distance of about 30 feet in the more northerly of the 
two east crosscuts and are terminated to the east by 
a fault. Disseminated sulphides, however, are found 
on this level over a strike length of about 175 feet 
and a width of nearly 100 feet. If the occurrence 
of sulphides cut in the raise at the south end of the 
level is considered, the strike length would be increased 
about 75 feet. On this level the apparent maximum 
width is much farther north than on the tunnel level. 

The walls of the ore bodies are of different character 
in several parts of the mine. The fault on the 234- 
foot level is clearly later than the ore and is readily 
recognized. The quartz monzonite at the south end 
of the level is equally distinct. On the bottom level 
also a pale-greenish rock, which the microscope shows 
to be composed chiefly of garnet, is almost completely 
devoid of sulphides, except for thin veinlets and 
sparsely disseminated molybdenite. This rock may 
therefore be considered a well-defined wall rock, in 
that it has been distinctly unfavorable for the deposi- 
tion of the sulphide ore. It is exposed on the east 



side of the drift for more than 50 feet north and south 
of the shaft and also makes up the stretch between 
the fault that terminates the nearly massive sulphides 
and the Manning Canyon formation. 

In most places, however, the walls are gradational 
contacts between nearly solid masses of sulphide and 
fine-grained jasperoidlike quartz with a very minor 
content of metallic minerals. Much of the ore zone 
on the 234-foot level is occupied by such siliceous rock 
with only a moderate content of ore minerals. On 
the tunnel level similar rock separates areas of high- 
grade arsenic ore and in such places might be consid- 
ered as in the nature of "horses" of low-grade material 
between the more valuable bodies. Microscopic study 
of the siliceous material shows that locally it contains 
considerable amounts of a colorless chlorite and also 
of opal which in most of the occurrences seems certainly 
to be contemporaneous with the quartz. On the north 
end of the tunnel level, particularly adjacent to the 
"lead fissure", silicifieation has been much less preva- 
lent, and in the hanging wall of the stope at the north 
end crystalline marble is found adjacent to the ore. 
On figure 29 the intensity of the stippling indicates 
approximately the relative amount of the ore minerals 
to the gangue. 

Ore. — Two classes of ore have been shipped from 
the mine — arsenic ore and lead-silver ore containing 
arsenic. On all the levels the arsenic ore is found to 
the south and the lead-bearing material to the north 
in the ore zone. 

The hypogene arsenic ore mineral is arsenopyrite. 
The southern part of the ore body in the tunnel level 
is made up almost entirely of this mineral. Locally it 
occurs as long, slightly radiating bladed crystals that 
are generally found near the hanging wall, though 
some are within the ore body. For the most part 
masses of the arsenopyrite are almost structureless 
as viewed in the mine. Polished specimens of this 
kind of ore, however, disclose that it has been thor- 
oughly breccia ted and later cemented by quartz. The 
chief gangue mineral in the arsenic portion of the ore 
body is fine-grained quartz. This not only cements the 
fractured arsenopyrite but also forms rather linear 
bands within the ore body, like the jasperoidlike mate- 
rial that acts as the walls in many places. On the 
bottom level the portion of the ore body that contains 
chiefly arsenic has a much higher content of quartz 
than is found on the tunnel level. Small quantities 
of pyrite and even less abundant sphalerite are found 
in the arsenic ore. They normally occur near the 
edges of the ore body. Polished sections show that 
the sphalerite contains microscopic inclusions of chal- 
copyrite, jamesonite, and pyrrhotite. 

The greater part of the arsenic ore on all three levels 
shows relatively little surficial alteration. Locally on 
the working and tunnel levels the sulphide is veined 
by thin seams of greenish massive scorodite, and in a 



MINES AND PKOSPECTS 



161 



few places small vugs filled with crystalline seorodite 
were found. On the bottom level the arsenopyrite 
appears to be essentially fresh, but the approximate 
coincidence of the level with the water table has caused 
it to be locally coated by gypsum, nontromte(?), and 
a yellow-green fine-grained mineral that appears to be 
an undescribed hydrous iron arsenate. In the hang- 
ing-wall crosscut from the shaft on this level a reddish- 
brown ooze that contained considerable quantities of 
arsenic was being deposited. 

On the two upper levels about 25 feet north of the 
inclined shaft there is a rather sharp contact between 
nearly fresh sulphides and ore that is almost completely 
oxidized to seorodite. This is associated with an abun- 
dant white chalky-appearing mixture of opal and 
quartz. The occurrence of oxidized ore at this point 
is rather puzzling, because the vertical distance from 
the level to the surface here is somewhat greater than 
it is in the unosddized area to the south. The expla- 
nation perhaps lies in the fact that there is much less 
of the relatively impervious jasperoid adjacent to the 
ore body here than there is to the south. 

The lead ore on the tunnel level is thoroughly 
oxidized, and as a result its primary relations to the 
arsenic ore are not definitely known. The wide lead 
stope just north of the shaft Immediately adjoins the 
seorodite portion of the arsenic ore, and in it, as well 
as in the small stopes on the working level above, both 
arsenic and lead minerals are found. A fine-grained 
pale-brown member of the jarosite group that is proba- 
bly beudantite occurs in considerable quantities, in 
addition to varying quantities of cerusite, seorodite, 
and jarosite. In the large stope mentioned the ore 
appears to form a continuation of the wide body of 
rather poorly defined arsenic ore, and the arsenic con- 
tent is relatively high. North of the stope the ore is 
limited to relatively narrow veinlike zones in which the 
arsenic content is probably somewhat lower, as some 
of the specimens of the jarosite minerals occurring 
to the north are found when treated to be nearly free 
of the arsenate radicle. 

On the 234-foot level the massive sulphides termi- 
nated by the northwesterly normal fault probably 
represent the downward extension of the lead ore on 
the tunnel level. In polished specimens of this ore 
arsenopyrite, pyrite, sphalerite, chaleopyrite, galena, 
jamesonite, aikinite, and stibnite are the metallic min- 
erals recognized and are set in a quartz or calcite 
gangue. Pyrite and arsenopyrite are the most abun- 
dant of the sulphides. Both are thoroughly fractured, 
and the angular fragments are cemented by quartz and 
the other sulphides. The arsenopyrite is the more 
thoroughly fractured of the two, and in some places 
angular and cracked fragments may be seen that are 
surrounded by unfractured pyrite. Sphalerite is the 
next most abundant sulphide. It appears to be essen- 
tially contemporaneous with the quartz and shows no 



sign of fracturing. It contains locally tiny dots and 
stringers of chaleopyrite, in addition to rounded rem- 
nants of the pyrite that it has replaced. Chaleopyrite 
was recognized only as small inclusions in the sphal- 
erite. Jamesonite and galena are both somewhat later 
than the sphalerite, for they embay and vein it as well 
as the pyrite and arsenopyrite. They appear to be 
mutually exclusive, specimens that contain one being 
free from the other. Galena is readily recognized in 
polished sections by reason of its cleavage . It contains 
small inclusions of a darker-gray mineral that is aikin- 
ite, a copper-lead-bismuth sulphide. The relations 
between galena and jamesonite suggest that the forma- 
tion of the one or the other was dependent on the local 
relative concentration of antimony with respect to lead 
at the time of ore formation. 

The only gangue mineral in the massive sulphide ore 
is quartz in very small quantities. In the lower-grade 
ore to the west the sulphides, chiefly pyrite and arseno- 
pyrite, have replaced coarsely crystalline calcite which 
the microscope shows to have suffered considerable 
deformation. Locally a white soft claylike mineral 
that has some of the optical properties of kaolinite 
veins and coats the lower-grade sulphide ore. 

The relative proportions of the sulphides vary within 
the ore body. Pyrite or arsenopyrite or a mixture of 
the two generally predominates and in some places is 
present to the almost complete exclusion of the other 
sulphides. Sphalerite appears to be somewhat more 
widely distributed and more abundant than the lead- 
bearing sulphides. Near the eastern boundary of the 
high-grade sulphide mass differing proportions of sul- 
phides have caused a rude banding that strikes nearly 
north and dips about 50° W. 

There appear to be several factors that have con- 
trolled the ore deposition in this mine. The Ochre 
Mountain limestone is obviously the most important, 
in that it has provided an easily replaceable rock. The 
fault that terminates the limestone to the south and 
the quartz monzonite exposed on the bottom level 
both affect the continuity of the limestone. The rela- 
tively greater difficulty in the replacement of the forma- 
tions thus brought into contact with the limestone may 
perhaps account for the large dimensions of the south 
end of the ore body. The alteration of the limestone 
to garnet and other silicate minerals is also unfavorable 
to ore deposition, as is clearly shown on the bottom 
level. 

These factors are negative ones in that they limit 
the ore body. A more positive factor in its localization 
is thought to be a series of fractures or minor faults that 
are essentially parallel to the strike and dip of the 
limestone. The most evident of these is the so-called 
"lead fissure", which has faulted the quartz porphyry 
dike. Another parallel fracture that is closely related 
to the lead ore is exposed in the lead stope and at the 
north end of the working level. Its relation to the 



162 



GOLD HILL MINING DISTRICT, UTAH 



dike was riot observed. These fractures were not 
observed in the arsenic-rich portion of the ore body, 
but the linear nature of the siliceous horses in the 
arsenic ore and the apparent gradation between arsenic 
and lead ore may indicate that similar fractures were 
utilized by the arsenic-bearing ore solutions. 

The occurrence of the lead ores north of the arsenic 
ore is perhaps the result of the later introduction of 
the lead sulphides and the fact that the unreplaced 
rock to the north was more readily attacked than the 
nearly massive arsenopyrite, 

OBEQON 

The Oregon group of 10 unpatented claims, owned 
by J. J. and Ada Gerster, of Gold Hill is west of 
benchmark 5416 on the Lincoln Highway, south of 
the town of Gold Hill. The workings consist of shallow 
pits and cuts, chiefly along or near a fault that sep- 
arates the Ochre Mountain limestone from the Oquirrh 
formation. The fault strikes west of north and dips at 
a moderately low angle to the west. Along it the lime- 
stones have been crushed and thoroughly silicified 
and crop out as reddish-brown jasperoid. The foot- 
wall side of the fault line has been the site of two small 
intrusions of quartz monzonite in this vicinity. The 
work done has been in the nature of exploration for 
ores similar to those in the U.S. mine, to the east, or 
in the Cane Springs mine, to the northwest, both of 
which are in the same belt of Ochre Mountain lime- 
stone, rather than a development of any specific 
ore-bearing outcrops. 

HBBAT 

The principal workings of the Herat mine are on the 
south side of the low hill about 1,000 feet northeast of 
Clifton. The mine was the scene of some of the earliest 
work in the district, and the inclined stack of an old 
smelter that treated the ores may still be seen extend- 
ing up the side of the hill. In 1920 the owners of the 
mine were reported to be Messrs. Watson & Chandler, 
of Bingham, Utah. 

The early production from the mine is not known. 
In recent years several shipments, mostly of slag and 
speiss from the smelter dump, have been made by 
lessees. One of 156 tons was made in 1920 and had an 
average content of 0.025 ounce of gold and 11.1 
ounces of silver to the ton, 0.3 percent of copper, and 
7.4 percent of lead. Another shipment of 47 tons in 
1923 contained 0.021 ounce of gold and 16.0 ounces 
of silver to the ton, 0.15 percent of copper, and 11.4 
percent of lead. 

The mine workings are all in a mass of Ochre 
Mountain limestone that occurs as a blunt northward 
extending arm into quartz monzonite. The limestone 
near the mine has been rather thoroughly altered to 
lime-silicate rocks, and the detailed structure in the 
vicinity is not discernible. 

The ore bodies appear to have replaced the limestone, 
but the original outlines of the ore shoots and their 



structural relations have been almost completely 
destroyed. Ore apparently cropped out both north 
and south of the road that runs along the south side 
of the hill, to judge from the old stopes and workings 
that are found there. 

The ore that was seen in the old workings and on the 
dumps was thoroughly oxidized. In only one speci- 
men were any sulphide areas noted, and these were all 
composed of arsenopyrite. The bulk of the ore now 
visible consists of brown and greenish scorodite, 
with which are large amounts of dark-brown to black 
massive iron oxides. Small quantities of plumbo- 
jarosite or its arsenic-bearing analog and minor 
amounts of other oxidized lead minerals are present. 
Vein quartz in small quantities was also found on the 
dumps. It resembles closely the quartz of the tetra- 
hedrite-bearing veins, and the small copper content 
of the shipments may have been derived from this 
source. 

The scanty evidence that is now available indicates 
that this deposit is in many respects similar to the 
oxidized portions of the arsenic-rich ore bodies in the 
Western Utah and U.S. mines. There is some doubt 
as to any future importance of the mine, however, for 
the contact of the quartz monzonite with the sedi- 
mentary rocks in this region has in most places a very 
low dip, and as the igneous rock is exposed at the 
surface only a short distance away, it probably cuts 
out the favorable limestones at no great depth. 

COPFEB-HAD-SIIVa BBPIACEMENT BODIES 
MONOCCO 

The Monocco claim is about 1,000 feet west-north- 
west of Montezuma Peak and is reached by the north- 
ern branch of the central road leading eastward from 
Clifton Flat. The claim has been patented for many 
years and is now reported to be owned by the heirs 
of a Mr. Kimball. In recent years the claim has been 
worked by lessees. From 1917 to 1920 shipments 
amounted to 786 tons of copper and lead-silver ore, 
which had an average content of 0.002 ounce of gold 
and 3.52 ounces of silver to the ton, 10.17 percent of 
copper, and 0.88 percent of lead. In 1926 the claim 
was under lease to Richard Lyman, J. R. Driggs, and 
G. R. Steele. At the time of visit they had made a 
shipment of copper ore and one of lead-silver ore. 
The copper ore contained 0.01 ounce of gold and 3.6 
ounces of silver to the ton, 11.1 percent of copper, 15.9 
percent of iron, and 38.8 percent of insoluble matter. 
The lead-silver ore assayed 0.045 ounce of gold and 11.4 
ounces of silver to the ton, 8.8 percent of lead, 1.0 
percent of copper, 2.0 percent of zinc, 3.5 percent of 
arsenic, 0.5 percent of antimony, 3.0 percent of sul- 
phur, 3.8 percent of lime, 2.5 percent of insoluble 
matter, and 25.6 percent of iron. Shallow cuts and 
tunnels are scattered over the surface of the claim, 
the only concentrated work being found in an incline 
200 feet long on the southern slope of the ridge south 
of the cabins. 






MINES AND PROSPECTS 



163 



The workings are all in interbedded sandstone and 
limestone of the central facies of the Oquirrh formation. 
In the vicinity of the mine these beds strike N. 10°- 
20° W. and dip gently to the east. No igneous rocks 
are exposed on the claim, but the western contact of 
the quartz monzonite stock crops out about 1 ,500 feet 
to the north and a slightly greater distance to the east. 

The ore is found both in fissures cutting the sedi- 
mentary rocks and as replacement deposits in rather 
pure limestone beds adjacent to the fissures. At least 
three fissures are exposed on the claim. They strike 
northeast and their dip ranges from 75° W. to nearly 
vertical. The thickness of ore in the fissures is gen- 
erally less than 2 feet. Locally quartz-carbonate veins 
have been introduced along the older ore-bearing fis- 
sures. Eight ore-bearing limestone beds are cut by 
these fissures. Their average thickness is less than 3 
feet, and in many places only a part of the limestone 
has Heen replaced by ore. Replacement has extended 
only a short distance away from the fissures, 15 feet 
being the maximum observed. Cherty limestone beds, 
sandstones, and limestone altered to silicates appear 
to have been unfavorable for ore deposition. At sev- 
eral places the ore beds are displaced a few feet by 
northwesterly faults that dip to the northeast. 

The copper ore is found either in or very close to the 
fissures. It is almost completely oxidized and consists 
chiefly of copper pitch in which remnants of chalcopy- 
rite may locally be observed. Chrysocolla, azurite, 
and malachite are less abundant sources of copper. 
The lead ore is found chiefly in the limestone beds, 
although small concentrations of unoxidized galena are 
not uncommon in the fissures. Plumbojarosite ap- 
pears to be the most wide-spread lead mineral, but 
where superficial alteration has been, less intense an- 
glesite and cerusite are found, in places surrounding 
a core of galena. Fine-grained quartz and iron oxides 
are abundant gangue minerals, and in some places 
mammillary opal fills vugs in the ore. 

SILVER KING 

The Silver King group, which has also been known 
as the Mineral Hill, is on the western and northern 
slopes of Montezuma Peak. It is said to enclose about 
200 acres of ground, which almost completely surrounds 
the Monocco claim. The owners of the claims are 
F. C. Little, of Moroni, Utah, and Ollie Young, of 
Clifton. Small shipments have been made from the 
group at different times. One shipment of 10 tons of 
ore containing 6 ounces of silver to the ton and 18 
percent of copper prior to 1912 is reported by Dick, 7 * 
and one of 64 tons in 1917 contained 9.3 ounces of sil- 
ver to the ton and 8.1 percent of copper. Shipments 
of less than a ton that were valuable chiefly for their 
silver content were made in 1920 and 1921. In 1922 
and 1923 shipments aggregating 132 tons had an aver- 

" Dick, J. C, unpublished mining report. 



age content of 0.035 ounce of gold and 18.1 ounces of 
silver to the ton, 2.77 percent of copper, and 5.19 per- 
cent of lead. 

The greater part of the development on the group 
has been done a short distance west of the Monocco 
camp. Here the interbedded sandstones and lime- 
stones of the Oquirrh formation strike N. 40° W. and 
dip 20° NE. These beds are cut by three ore-bearing 
fissures that strike northeast and dip 85° NW. Ore 
is also found adjacent to the fissure in two thin lime- 
stone beds which are unusually free from impurities 
and which are separated from each other by 10 feet 
of thin-bedded cherty limestone, which has been partly 
replaced by wollastonite. An inclined shaft has been 
driven down the intersection of the strongest fissure 
with the higher of the limestone beds for about 200 
feet, and from it have been extended several short 
drifts and stopes along the mineralized limestone. At 
the bottom of the shaft a fault striking N. 60° W. and 
dipping 30° SE. brings the ore bed into contact with 
cherty limestone similar to that in the footwall. If 
the two are the same, the throw along the fault cannot 
be much more than 5 feet. 

The ore is almost completely oxidized. In the fis- 
sures a deep-brown to almost black copper pitch is the 
chief copper mineral. Some of the black pitch is said 
to assay 62 percent of copper. Chrysocolla, mala- 
chite, and azurite vein the copper pitch in most places. 
Comparatively little lead ore is found in the fissures. 
It occurs chiefly in the adjacent limestone bed and con- 
sists of cerusite, anglesite, and plumbojarosite. Al- 
though the limestone is about 2 feet thick, in many 
places the ore is present in only a part of the bed, the 
remainder being unmineralized. 

Fine-grained quartz and iron oxides are the most 
abundant gangue minerals. In addition to being 
mixed with both copper and lead minerals, they also 
form a casing to the lead ore, extending beyond it in 
the replaced limestone bed. 

Other parts of the group show similar copper and 
lead-silver deposits, though none so far developed are 
as extensive. A moderate amount of shallow work 
has been done on these other deposits, particularly on 
the Searchlight claim, which is north of the Monocco. 

MOHAWK 

The Mohawk group is on the eastern slope of hill 
5852, about 1% miles west-northwest of the town of 
Gold Hill. In 1926 the claims were owned by Hicks 
& Hudson. Development work on these claims has 
beep directed toward the exploration of lead replace- 
ment ore bodies in limestones of the Oquirrh forma- 
tion. The limestone has been bleached and recrys- 
tallized to a white marble but shows almost no develop- 
ment of silicate minerals. The ore shoots are for the 
most part rather small and contain considerable quan- 
tities of quartz and iron oxides in addition to the 



164 



GOLD BILL MINING DISTRICT, UTAH 



oxidized lead minerals. There are numerous minor 
faults on the property. A small dike of quartz mon- 
zonite crops out a short distance east of the workings, 

WALLA WALLA 

The Walla Walla claim is on the eastern slope of 
hill 5702 about a mile and a quarter west of Gold Hill. 
It is owned by Hicks & Hudson. The ore on the claim 
has replaced a limestone bed in the Oquirrh formation 
that strikes N. 20° W. and dips 30° W. A fissure 
striking N. 80° E. and dipping 65° N. appears to hare 
afforded a channel for the mineralization. The lime- 
stone bed is about 3 feet thick but has not been com- 
pletely replaced by the ore minerals. The ore consists 
of quartz, iron oxides, a mineral resembling plumbo- 
jarosite, and scorodite. Some unoxidized remnants 
of galena were also observed. 

GAEBISON MONSTBR MINING CO. 

The Garrison Monster group of 27 patented claims 
is on the northeastern tip of Dutch Mountain. The 
property is owned by J. P. Gardner, of Salt Lake City, 
but during the period of examination it was being 
worked by lessees. The first locations are reported 
to have been made in 1882. The earliest recorded 
production, however, was in 1917. In that year and 
the succeeding two years 700 tons of ore was shipped 
that averaged 0.004 ounce of gold and 2.38 ounces of 
silver to the ton, 0.63 percent of copper, and 15.33 per- 
cent of lead. Production began again in 1924, and 
from the end of that year until July 1927 about 35 
carloads of ore were shipped. These shipments had 
a silver content that ranged from 1.16 to 6.2 ounces 
to the ton and a lead content from 6.70 to 40.40 percent. 

An old camp, consisting of a bunk house and several 
smaller buildings, is 1 % miles south-southwest of Gar- 
rison Monster siding on the Deep Creek Railroad and 
is reached by automobile along a road that branches 
from the Gold Hill-Wendover road a quarter of a mile 
north of the siding. The road branching from the 
main road south of the siding is passable by automobile 
only as far as the new camp near the tunnel portal at 
an altitude of 4,894 feet. 

Activity on this group of claims has been concen- 
trated at three places — the Uncle Sam claim, three- 
quarters of a mile southwest of the old camp in Royal 
Gulch; the New Year claim, at the old camp; and 
the Consolidated and adjacent claims, half a mile east 
of the old camp. The latter locality has provided 
almost the entire production credited to the company, 
and the tunnel at 4,894 feet, to the north, was driven 
with the idea of more fully developing the ore there 
exposed. 

Consolidated claim. — The Consolidated claim is on 
the south side of the low hill (altitude 5,750+ feet) 
that has at times been known as Wilson Hill. The 
hill is separated from Dutch Mountain proper by a 
gulch eroded along a transverse fault. On the south 



side of the fault the Prospect Mountain quartzite is 
exposed. North of it are a series of nearly horizontal 
outcrops of formations that range in age from Middle 
Cambrian to Carboniferous. These are, for the most 
part, thrust plates related either to the Ochre Moun- 
tain thrust or to the transverse fault. (See structure 
sec. A-A', pi. 2.) 

The lowest outcrop in the vicinity of the claim con- 
sists of thin-bedded limestones and shales of Middle 
Cambrian age. In many places the limestones of 
this group have been altered to dolomite. The por- 
tions thus changed have lost all of their original texture 
and weather to a deep-brown color. Next above is a 
plate of Upper Cambrian dolomite. This rock is nor- 
mally deep bluish black and is thick-bedded, but in a 
few places individual beds have been bleached to a 
cream color. A 10-foot zone of thin-bedded limestone 
is interbedded with the dolomite near the mine work- 
ings. This plate is about 300 feet thick on the south 
side of Wilson Hill but is more than 500 feet thick on 
the north side. Both upper and lower contacts are 
faults, as is shown not only by the stratigraphy but 
also by the striking discordance between the bedding 
of the formations on both sides of the two faults and 
between the bedding planes and the contacts. The 
contact between the dolomite and the underlying lime- 
stones is well exposed at several places on the east 
side of the hill at an altitude of about 5,300 feet and is 
made conspicuous by the contortions in the thin- 
bedded limestones. The upper fault is not as strik- 
ing, but close observation readily reveals its presence 
on the south side of the hill a short distance higher up 
the slope from the line of prospect holes on the ore. 

Overlying the dolomite is a plate of variable but 
small thickness, composed of interbedded brown- 
weathering sandstone and blue limestone. Its lith- 
ology and fossil content are those of the upper portion 
of the Woodman formation. It in turn is overlain by 
100 feet or more of fossiliferous Madison limestone, 
the contact between the two being obviously a thrust 
fault. This fault is well exposed near the southwest 
shoulder of Wilson Hill at an altitude of about 5,650 
feet. The limestone is overlain conformably by about 
50 feet of reddish-brown sandstones and sandy shales 
that are characteristic of the basal portion of the Wood- 
man formation. 

Igneous rocks are not abundant near the mine. The 
most prominent is an exposure of thoroughly altered 
porphyry in which the "porphyry incline", or main 
shaft, is driven. This is a white, irregularly iron- 
stained rock in which a few quartz phenocrysts can 
be seen. Under the microscope a few laths of sericite 
after biotite are shown to be present, together with 
accessory apatite and zircon. The remainder of the 
rock is a fine-grained aggregate of quartz. The dike 
is exposed at intervals for more than 500 feet to the 
west. Another series of exposures of a porphyry is 



MINKS AND PEOSPECTS 



165 



Raise 

|„ Face 88 feet 
' below main fens/ 




' Bottom of _> 
fshaft4Sfeet^j 
below main level 



Gobbed '* 






50 
i 




40feet 
below collar 



Figure 31.— Mine workings on Consolidated claim, Garrison Monster mine. From sketch famished by the lessees. 



present higher on Wilson Hill, along the thrust fault 
that separates the Madison limestone from the Wood- 
man formation. 



In addition to the thrusts that separate the several 
plates, other faults occur in the vicinity of the mine. 
In the long tunnel, for example, two steep reverse 



166 



GOLD HILL MINING DISTRICT, UTAH 



faults can be recognized at distances of 685 and 800 
feet from the portal, by reason of the repetition of 
exposures of tlie Middle Cambrian limestone. In 
other places minor faults are made apparent by offsets 
of particular beds or contacts. 

The ore appears to be localized in still another minor 
fault, for the wall rock is thoroughly brecciated, and 
its northeast strike and low northwest dip make large 
angles with the strike and dip of the adjacent sedimen- 
tary rocks. The fault fissure at the surface crops out 
within the plate of Upper Cambrian dolomite, about 
75 feet below its upper limit. Several prospect holes 
along it show that it has a strike length of about 
1,000 feet. The average strike as shown by these 
workings is east-northeast, but notable variations from 
this direction are shown by the mine workings (fig. 
31). The dip is also somewhat variable but averages 
close to 30°, as shown not only by direct measurements 
on the vein but also by the point of intersection of the 
vein in the long tunnel. The fault is clearly later 
than the thrust between the Upper and Middle Cam- 
brian, for the ore occurring in the tunnel has partly 
dolomitized Middle Cambrian limestones as its wall 
rock. 

In the main workings from the porphyry incline 
the ore is thoroughly oxidized. Gray sandy cerusite 
and yellow-brown powdery plumbojarosite are by far 
the most abundant lead-bearing minerals. They 
occur, in many places relatively free from impurities, 
in lenticular masses as much as 3 feet in width and 
10 to 20 feet along the strike. Such occurrences have 
a casing of banded reddish-brown iron oxides, in which 
are masses of a white clay mineral that appears to be 
largely halloysite. Smaller quantities of calamine, 
malachite, plumbojarosite, and other oxidized min- 
erals are also included. The walls of the vein are 
composed of a thoroughly brecciated and bleached 
dolomite, in which there is locally a considerable 
amount of barite, and also isolated crystals of galena 
and limonite pseudomorphs after pyrite. In several 
places oxidation of the dolomite has converted the 
normally dense rock to a sandy aggregate of dolomite 
grains that closely resembles the sand carbonate (ceru- 
site) found in the mine. The difference in weight of 
the two minerals, however, provides a ready means 
of distinguishing them. The rather scant exposures 
in these workings suggest that the shoots or concen- 
trations of lead minerals may be correlated with syn- 
clinal warps in the vein. 

The continuation of the vein struck in the long 
tunnel nearly 1,000 feet from the portal shows very 
little oxidation. It consists of a zone of dolomitized 
limestone 5 feet or more in width that is impregnated 
with sulphides and white barite. Galena is by far the 
most abundant sulphide. Small quantities of pyrite 
may also be recognized in hand specimens, but the 
microscope is required to prove the presence of small 



quantities of sphalerite and tennantite. Another 
galena-bearing zone was struck about 150 feet nearer 
the portal. 

The exposures of the ore zones in the tunnel are 
much less veinlike than in the porphyry incline work- 
ings. This may be the result of the change in wall 
rock, for the thinner-bedded Middle Cambrian would 
probably not fracture as cleanly as the higher dolo- 
mites. The change might also be due to the fact that 
the exposed ore shoots on the higher levels pitch to 
the west and would at this altitude lie some distance 
westward along the strike of the ore zone. 

New Year claim. — On the New Year claim, a short 
distance west of the old camp, a long tunnel has been 
driven to the south with the expectation not only of 
tapping several small veins on the hillside but also of 
eventually reaching the vein on the Uncle Sam claim, 
in Royal Gulch. The tunnel is now largely caved and 
could not be examined, but the writer was informed 
that nothing of consequence was found in it. 

Uncle Sam claim.— The workings on the Uncle Sam 
claim are about 1,500 feet southeast of the cabin in 
Royal Gulch, on the northeast side of the gulch. As 
shown on plate 2, the structure in this vicinity is 
extremely complex. A number of thin and discon- 
tinuous thrust plates are exposed beneath the Ochre 
Mountain thrust. 

The ore on the Uncle Sam claim was found in a vein 
essentially parallel to the bedding of the Madison lime- 
stone that forms one of these thrust plates. The ore 
mineral exposed at the surface is plumbojarosite, and 
the gangue is composed of barite and the limestone. 
A chute extending down to the gulch bottom seems to 
indicate that some shipments have been made from 
this claim, but the quantity and grade are not known. 

EVANB 

The Evans group of 21 claims, all of which are said 
to be patented, covers a large part of Royal Gulch 
other than that enclosed within the boundaries of the 
Garrison Monster property. Shallow pits, shafts, and 
tunnels are located at various places on the property, 
but so far as known there have been no shipments of 
ore. 

The workings are concentrated for the most part 
either in the "window" of pre-Carboniferous rocks 
exposed in the gulch beneath the Ochre Mountain 
thrust or in the Madison limestone immediately above 
the thrust. The geologic structure in this region is 
unusually complex. (See pp. 81-82). The ore bodies 
developed include both galena-barite replacement 
deposits in limestone, similar to those on the adjoining 
Garrison Monster property, and quartz-tetrahedrite 
veins like those on the Undine and Rea claims. The 
replacement bodies are for the most part in the 
Madison limestone, and the quartz-tetrahedrite veins 
in the pre-Carboniferous dolomites. 



MINES AND PROSPECTS 



167 



WIIIOW SPRINGS DISTRICT 
HISTORY AND PRODUCTION 

The Willow Springs district was organized May 
21, 1891. Only a few claims in the district are within 
the Gold Hill quadrangle, and most of these, except 
for those of the Sunday group and the Dewey group, 
are unsurveyed. The production from the part of the 
district here considered appears to have been limited 
to a few small shipments of high-grade ore. 

PROSPECTS 

DEWEY 

The Dewey group of five patented claims is on the 
north side of Sevy Canyon about half a mile west- 
southwest of South Peak, which is on the ridge line of 
the Deep Creek Mountains. Swan Moline, of Gold 
Hill, reports that a shipment of 800 to 900 pounds of 
ore was made from the property between 1890 and 
1900 and yielded about $1,800, the valuable metal 
being silver. 

The country rock in this vicinity is the upper portion 
of the Laketown dolomite, of Silurian age. A strike 
fault of low westward dip cuts the dolomite and has 
resulted in considerable brecciation. The fault has 
caused a repetition of beds in the dolomite and is 
therefore of the reverse variety. The throw was not 
determined but probably amounts to a few hundred 
feet. 

The dolomite breccia along the fault has been 
cemented and partly replaced by fine-grained quartz 
across a width that is locally as great as 20 feet. In 
places the quartz is vuggy, and the vugs are lined with 
terminated quartz crystals. In the lower portion of 
the zone there is abundant coarsely crystalline white 
dolomite in the breccia. Several small prospect pits 
and stopes have been opened in this quartz-rich zone, 
and this material apparently constituted the ore. The 
only signs of mineralization other than the quartz are 
a few copper stains and small quantities of iron oxides. 
It is probable, in view of the copper stains and the 
high silver content of the ore shipped, that the valuable 
mineral was tetrahedrite and that the deposit is related 
to the quartz-tetrahedrite veins in the Clifton district. 

SUNDAY 

The Sunday group of 16 claims is in Bagley Gulch, 
on the south side of North Pass Canyon. The claims, 
some of which were being surveyed for patent in 
1926, are owned by the Bullion-Bagley Mining Co. of 
Salt Lake City. A camp had been established at the 
point marked "7058" on the topographic map, within 
a short distance of which the prospecting activities of 
the company were concentrated. 

The Abercrombie formation underlies the surface 
in the vicinity of the claims, and almost all of the 
prospecting has been done in the dolomitized massive 
limestones of that formation. The group of claims is 



about halfway between two northwestward-striking 
transverse faults, and the minor faults and fractures 
in the region, including those followed by the veins, 
are apparently related to them, as they have parallel 
strikes. 

Prospecting has been done at several places on the 
group of claims. What appears to be the most 
promising deposit is a quartz vein exposed a short 
distance north of the camp. The vein is from 1 to Z% 
feet wide, strikes N. 65° W. and has a dip that ranges 
from vertical to about 80° S. The vein filling consists 
of coarsely crystalline white quartz that contains 
numerous vugs lined with terminated quartz crystals. 
In this are local concentrations of galena and tetrahedrite 
with their oxidation products. Some of this sulphide- 
bearing ore is reported to contain as much as 1,700 
ounces of silver to the ton, but so far as known no 
shipments have been made. 

South of the camp a shallow shaft has been sunk to 
explore several "watercourses" in the limestone that 
are filled with barren iron oxides. No valuable min- 
erals had been found in this material at the time of 
examination. 



LEAD CARBONATE 



The Lead Carbonate claim is in the south fork of 
Dry Canyon, at an altitude of about 7,200 feet. The 
present ownership of the claim and whether or not it 
is patented are unknown. The ruins of small buildings 
below the workings indicate the site of the former 
camp. The claim was worked in 1917 by W. J. 
McLaughlin, of Salt Lake City. 

The workings are all in mottled limestones that are 
dolomitized here and there in the vicinity of the claim. 
The beds at this point strike a few degrees east of north 
and dip 35°-40° W. A large transverse fault, striking 
east, is exposed about a quarter of a mile north of the 
ore shoot. 

The ore has replaced one of the limestone beds and 
is localized in a shoot that has a strike length of about 
10 feet and a width of 2 to 3 feet. It appears to pitch 
to the southwest. An inclined shaft has been driven 
on the shoot, and a tunnel, whose portal is 40 feet 
below the outcrop, extends toward its projected 
position in depth. No transverse mineralizing frac- 
ture, such as was observed at other replacement bodies 
of this type, was recognized at the surface. 

The ore appears to have been completely oxidized 
at the surface, but some specimens of relatively 
unaltered ore, presumably from the lower part of the 
ore shoot, were found on the dump. They showed 
veinlets and blebs of galena and tetrahedrite embedded 
in limestone or dolomitized limestone that contained 
a considerable amount of quartz, much of which was 
in the form of terminated crystals as much as a quarter 
of an inch in length. At the surface much of the car- 
bonate has been leached out, leaving a skeleton of 



168 



GOLD HILL MINING DISTKICT, UTAH 



quartz, with which are associated various oxidized 
lead, copper, and iron minerals. 

One shipment of 8 tons of ore was made from the 
claim in 1917. This contained 18 ounces of silver to 
the ton and 37 percent of lead. It is probable that 
some other small shipments have also been made. 

SILVER 

The unpatented Silver claim, which in 1926 was the 
property of Alvin Trippe, is on the south side of Dry 
Canyon a short distance east of summit 8182, at an 
altitude of about 8,000 feet. 

The ore is found in fissures cutting dolomitized 
limestone in the lower part of the Abercrombie for- 
mation. The fissures strike about N. 70° W. and dip 
very steeply to the northeast. They are from 2 to 6 
inches in width and are filled with quartz, fragments 
of wall rock, and oxidized copper, lead, and iron 
minerals. The wall rock shows minor amounts of 



silicification away from the fissures. Only a relatively 
small amount of shallow work has been done on the 
claim, and apparently no ore has been shipped. 



OTHER PROSPECTS 



There are several other prospects in the part of the 
Willow Sprinp district that is included within the 
quadrangle, particularly near the mouth of Dry 
Canyon. These do not differ in any important respect 
from the prospects already described, and as the names 
of the claims could not be ascertained they are not 
described here. The name of the claim upon which is 
located the shaft shown on the map near summit 
6954, on the north side of North Pass Canyon, is alsd 
unknown. The shaft is an incline sunk on a few 
parallel joints that strike N. 85° E. and dip 75° S. 
No valuable minerals were observed in the shaft or 
on the dump. 



INDEX 



Page 

Abercrombie formation, age and correlation of -io 

distribution of - 8 

fossils of _ 10 

lithology of.. . s-9 

section of — .' 9 

thickness of _ 9 

Abstract of report... vn-vm 

Accessibility of the area — 1 

Acknowledgments for aid - — 4 

Actinolite, occurrence of. 114 

Adamite, occurrence of... 116 

Aikinite, occurrence of. 112 

Ajax limestone, correlation of 15 

Albert claim, features of _ 127-128 

Alblte, occurrence of. ' 113 

Alkali basalt, partial analysis of 52 

petrography of 62 

Alteration of ores, relation of physical and chemical character to superficial. . 105-107 

relation of water table to superficial 104 

Alvarado mine, features of 128-181 

Amphibole, apatite and molybdenite in _ pi. 9 

Andalusite, occurrence of.. '. '__:"_' 114 

Andesite, biotite and hornblende, petrography of 60 

Anglesite, occurrence of. 117 

Apatite, occurrence of _ lie 

ApUte dikes, features of 48 

Arseniosiderite, occurrence of.. 116 

Arsenopyrite, occurrence of HI 

Axinite, occurrence of. 114 

Azurite, occurrence of 113 

B 

Bamberger mine, features of. 125 

Bar Creek, anticline west of 87-88 

concealed thrust fault west of , 88 

faulting west of - - . 88 

minor faulting east of 88-87 

minor folds west of 87-88 

Bar Creek fault, rela tions of 66,87 

Barite, occurrence a 1 . 117 

Beudantite, occurrence of. -. 117 

Bighorn dolomite, correlation of.. 17 

Biotite, occurrence of. 115 

Bird claim, features of 149 

Bismuthinite, occurrence of 111 

Bismuth, occurrence of - 110 

Bismutite, occurrence of 118 

Blood Canyon, normal faulting in 70 

Blood Canyon fault, direction and amount of movement along 69 

relations of 69,67 

Blood Mountain, minor structural features on 68-69 

Bluebird dolomite, correlation of 11 

Bonanza claims, features of — 144 

Bonnemort claim, features of... 135-136 

Bonneville beach and spit, view of z pi. 4 

Bornite, occurrence of _ Ill 

Boston claim, features of.. 143 

Boulangsrite, occurrence of 112 

Bowman limestone, correlation of.- - 10 

Braaer limestone, correlation of. 28,30 

Burling, L. D., fossils collected by 27 

Busby quartette, age and correlation of ... 8 

distribution of ' 7-8 

lithology of - 8 

thickness of 8 



Cabin shale, age and correlation of 7 

distribution of 6 

lithology of. 6-7 

thickness of ; .- 7 

M8H--88 12 



Page 

Calamine, occurrence of 115 

Calaveras claims, features of. 124 

Calaverite?, occurrence of... m 

Calotte, occurrence of _ 112-113 

Cambrian beds, unconformity at top of upper 14-15 

Cambrian system, formations of. _ 4-15 

Cane Springs mine, features of. 131-134 

Carbonate-sulphate, veins, alteration of 105 

features, of 101-102 

■mines. and prospects in isi 

outlook for mining... - - 110 

Carboniferous beds, unconformity at base of- 21-22 

Carboniferous system, formations of. _. 23-42 

formations of, correlations of _ 41-42 

Cash Boy claims, features of. 148-149 

Centennial claim, features of.. — 122-123 

Cerusite, occurrence of.- __ 113 

Chalcanthite, occurrence of — 117 

Chalcedony, occurrence of. 112 

Chalcocite, occurrence of - ill 

Chalcopyrite, occurrence of- — Ill 

Chisholm shale, correlation of 10 

Chlorite group, occurrence of 115 

Chloritiiation, alteration of quarts monionite by 95 

Chokeoherry dolomite, age and correlation of _ 15-16 

distribution of. - 16 

fossils of. _ 15 

lithology of - 16 

thickness of.. 16 

Christiansen and Sheridan Quiches, minor structural features between 89 

Christmas Mining Co., claims of 151 

Chrysocolla, occurrence of— 116 

Claron limestone, correlation of 43 

Clay and gravel, older, occurrence and character of 64 

Clay minerals, occurrence of - - - 115-116 

Clifton district, history of mining in us 

mines and prospects in .■ 119-166 

production of 118-119 

Clifton Flat, major anticline south of 70 

minor faults west and southwest of 70 

view of, from the southwest pi. 4 

Climate, data on 2-3 

Climax claims, features of 147 

Clinoclasite, occurrence of - 116 

Clinosoisite, occurrence of - 114 

Cole Canyon dolomite, correlation of 12 

Conichaleite, occurrence of 117 

Consolidated claim, features of 164-166 

Copper Bloom claims, features of. 127 

Copper Hill claims, features of 128 

Copper, occurrence of Ill 

Oopperopolis claims, features of - 125 

Copper pitch, occurrence of. 112 

Copper Queen Midland Mining Co., claims of.... 148 

Covellite, occurrence of 111 

Cuprotungstite, occurrence of 118 

Cyclone mine, features of 144-145 

polished section showing arsenopyrite fragments cemented by other sul- 
phides and quartz from pi. 10 

D 

Dagmar limestone, correlation of 10 

Danburite, occurrence of „ 114 

Deep Creek Mountain block, mutual relations of structural features of 69 

structure of. 66-69 

Deep Creek Mountains, fault along east base of _ 56 

fault along east base of, relations of 68 

structure of. 55 

Deformation of the beds, progressive variation in character of .'. 60-61 

Desclomte, occurrence of „ 116 

Deseret limestone, correlation of.. 28 

Devonian system, formations of... - 18-21 

Dewey claims, features of 167 

189 



170 



INDEX 



Page 

Dikes, porphyry, appearance of - - 46 

porphyry, distribution and size of — 46 

microscopic features of - - 46-47 

relations of, to one another - _ — 47-48 

relations of, to other rocks - - - - 47 

Diopside, occurrence of — 118 

Diopside-orthoelase alteration, features of 94-95 

Doctor claim, features of— -_ 133 

Dolomite, occurrence of - 113 

Dolomltic formations, origin of the pre-Carboniferotis.- — 22-23 

Dolomitteation, features of - 94 

Dry Canyon and Sevy Canyon faults, minor faults between j 67 

Dry Canyon fault, relations of — - 68,68 

minor faults south of- — . , 88 

Dutch Mountain block, structural features of, mutual relations of 85 

structure of - .— 78-85 

Dutch Mountain, fault along west side of 85 

faults on ... ._ ' 56 

• relations of recumbent anticline to structural features on- 86 

view of, from the southeast ... • pi. 4 

Dutch Mountain thrust, features of - .... - - 54 

relations of — 84 

E 

Ely Springs formation, correlation of - _ — . 17 

Enterprise claim, features of - 123-123 

Eocene (I), unconformity at base of - - - - 42 

Erosion surface, dissected postmature pi. 6 

Epidote, occurrence of — - 114 

Evans claims, features of - , - 166 



Faircbild, J. Q., chemical analyses by .. — 60,51,52 

Faulting, late normal, characteristics of 63 

late normal, relation of, to present topography - 61-63 

Faults in Gold Hill quadrangle, map showing pi. 3 (in pocket) 

Ferrisymplesite?, occurrence of - - - 116 

Field work - 3-4 

Fish Haven dolomite, age and correlation of 16-17 

distribution of. - . 16 

fossils of. _ - - 17 

lithologyof .1 - 16 

thickness of - - - 16 

Fluorite, occurrence of - - - 112 

Fortune claims, features of 144 

Frankie mine, features of * - 123 

Fusselman limestone, correlation of - 18 

Q 

Galena, occurrence of - - - - — 111 

Garden City limestone, correlation of.- - - 15 

Gardner dolomite, correlation of - 27 

Garrison Monster fault, probable conjugate faulting related to. 83-84 

relations of - - 59 

Garrison Monster fault zone, nature and amount of movement along 83 

relations of., j - - 82-83 

Garrison Monster mine, thin section from, showing barite replacing sulphides, pi. 11 

Garrison Monster Mining Co., claims of. — 164-166 

Geologic formations, age of- 4 

Geologie map and sections of Gold Hill and vicinity- pi 2 (in pocket) 

Geologic map and sections of Gold Hill quadrangle, Utah- _ pi. 1 (in pocket) 

Gerster formation, age and correlation of.. 40-41 

distribution of. — — 39 

fossils of. - - 40-11 

lithologyof — - — 39 

thickness of - - 39-40 

Olrty, G. H., fossils identified by. 28,28-29,30-31,32,33 

quoted 26,32,35-36,39,42 

Gold Belt claims, features of- 149-150 

Gold Bond claim, features of # „ 125-127 

replacement of minerals in specimens from pi. 10 

Gold Hill mine of United States Smelting, Refining & Mining Co. See TJ. S. 
mine. 

Gold Hill mine of Western Utah Copper Co., block diagram of- pi. 14 

geology of — 152-154 

level map of - - - — - pi. 15 

location, history, and development of.. - 151-152 

ore bodies of _ 154-156 

Gold Hill, northeasterly faults west and northwest of. 77 

Gold Hill Standard Mining Co., claims of _ 149 

Gold, occurrence of - - - _ 111 

Grampian limestone, correlation of _ _ 16 

Graphite, occurrence of. - 110 

Gravel and clay, older, occurrence and character of . 54 

younger, occurrence and character of. 54 



"Great Blue" limestone, correlation of 

Guilmette formation, age and correlation of., 
distribution of. 

fossils of-- - 



Page 
30 
21 
20 
21 

lithologyof. 20-21 

section of _ ___ 20-21 

thickness of 21 

Gypsum, occurrence of 117 

H 

Hartmann limestone, correlation of 10 

Heikes, V. C, quoted— - - l._ 118 

Hematite, occurrence of - 112 

Herat mine, features of 162 

30 
10 
14 
14 
14 
14 



Herat shale member of Ochre Mountain limestone, lithology of 

Herkimer limestone, correlation of 

Hicks formation, age and correlation of--- - - 

distribution of _ — _. 

fossils of - — , 

lithologyof 



pisolitio dolomite from pi. 5 



section of - 

thickness of - 

Highland Peak limestone, correlation of. 

Hornblende, occurrence of 

Humbug formation, correlation of 



- 14 

- - - 14 

10 

... 114 

28 

Humite, occurrence of— - 115 



Ida Lull claims, features of 125 

Igneous metarnorpMsm, features of. — — 91-97 

Igneous rocks, older, age of 48 

older, general features of. - 43 

younger, distribution and relations of.— 49 

petrography of - 49-53 

Immense claim, features of ._ 151 

Ineas group of claims, features of — 125 



Jamesonite.- ■ 111-112 

Jarosite, occurrence of 117 

Jasperold, alteration to - 93-94 

caicite cleavage lines in '. pi. 8 

Jefferisite, occurrence of - — 115 



Keno claim, features of - - 124-125 

Kirk, Edwin, fossils identified by 15,17,18,20,21 

quoted _. _. 21 

Knopf, Adolph, quoted 108 



Lake Bonneville beds, occurrence and character of. 54-55 

Laketown dolomite, age and correlation of 18 

distribution of. - 17 

fossils of. - 18 

lithologyof — - -. 17 

"marble cake" dolomite near base of pi. 5 

thickness of - - - 17-18 

Lamb