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Full text of "Geology and ore deposits of the Bodie Mining District, Mono County, California"

PHYSICAL SCIENCES 
LIBRARY 

- / UC DAVIS 



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GEOLOGY AND ORE DEPu^i i S 

OF THE 
BODIE MINING DISTRICT 

MONO COUNTY, CALIFORNIA 



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BULLETIN 206 



THE RESOURCES AGENCY 

GORDON K VAN VLECK 
SECRETARY FOR RESOURCES 



STATE OF CALIFORNIA 

GEORGE OEUKMEJIAN 
GOVERNOR 



DEPARTMENT OF CONSERVATION 

RANDALL M. WARD 
DIRECTOR 




DIVISION OF MINES AND GEOLOGY 

JAMES F DAVIS 
STATE GEOLOGIST 



■-^v 



GEOLOGY AND ORE DEPOSITS 
OF THE 
BODIE MINING DISTRICT 

MONO COUNTY, CALIFORNIA 



By 

Charles W. Chesterman 

Rodger H. Chapman 

and 
Cliffton H. Gray, Jr. 

DIVISION OF MINES AND GEOLOGY 



1986 



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UNIVERSITY OF CAUFORNIA 
DAVIS 

Jl'L 1 5 1SB7 

CALIF. DEPOS. 

GOVT. DOCS. -LIBRARY 



BULLETIN 206 

California Department of Conservation 
Division of Mines and Geology 
1416 Ninth Street, Room 1341 
Sacramento, CA 95814 



To 

Francis H. Frederick 

1907-1968 



CONTENTS 



Page 

ABSTRACT yH 

INTRODUCTION 1 

Location 1 

Field Work end Acknowledgments 1 

Previous Work ■\ 

REGIONAL GEOLOGIC SETTING 2 

Pre-Tertiory Basement 2 

Tertiary Rocks 3 

GEOLOGY OF THE BODIE MINING DISTRICT 3 

Silver Hill Volcanic Series 3 

Tuff Breccia 4 

Docite Flov^s 5 

Intrusive Dacite 5 

Chemical Composition 7 

Age of Silver Hill Volcanic Series 7 

Murphy Spring Tuff Breccia 7 

Pyroclastic Deposits 7 

Dacite Flows and Plugs 7 

Chemical Composition ]0 

Age of Murphy Spring Tuff Breccia 10 

Potato Peak Formation }q 

Dacite Flows 10 

Tuff Breccia 1 1 

Age of Potato Peak Formation 1 1 

STRUCTURE H 

Faults 12 

Jointing and Sheeting 14 

P'ugs 14 

GEOLOGIC HISTORY 16 

Structure Interpretation 1^ 

Tertiary Rocks 1^ 

ALTERED AND MINERALIZED ROCKS 17 

GEOPHYSICAL INVESTIGATIONS !"."!."'I.'".."."!""..! 19 

Regional Gravity and Mognetic Dato 19 

Detailed Gravity and Magnetic Data 20 

Results of the Gravity Survey 21 

Results of the Ground Magnetic Survey 22 

Summary 24 

ECONOMIC GEOLOGY ."..... 24 

Standard Hill areo 25 

Fortuno Series 25 

Incline Vein Series 26 

Burgess Vein Series 27 

Middle and Southern Mines Area 27 

Concordia Vein 27 

Red Cloud Vein 27 

Oro Vein 28 

Base Metal Vein 28 

Booker Vein 29 

Distribution of Metals in the Veins 29 

Depth of Mineralization 3I 

HISTORY OF MINING AND PRODUCTION 3I 

SUGGESTIONS FOR PROSPECTING !"!1."!."".""".""."!!"1 33 

REFERENCES CITED !!!!!!!!!!!!!!!"!H!!!!!!!!!"I"" 34 

APPENDIX: KAR SAMPLE DESCRIPTIONS 

AND LOCATIONS 35 



III 



ILLUSTRATIONS 
Plates 

(PLATES 1-5 IN POCKET) 

Plate 1. Generalized geologic map of the Bodie mining district and surrounding region. Mono 
County, California, showing gravity and mognetic profiles 

Plate 2. Geologic mop of the Bodie mining district. Mono County, California, showing rock alteration 
zones, residuol gravity, and vertical intensity magnetics 

Plate 3. Claim mop of the Bodie mining district 

Plate 4. Mine workings of the Bodie Bluff-Standard Hill area 

Plate 5. Mine workings of the Southern Mines area 

Figures 

Figure 1. Index mop of east-centrol California showing location of 

Bodie mining district 2 

Figure 2. Index to Plates 3, 4, and 5 2 

Figure 3. Normative compositions of rocks of the Silver Hill Volcanic 

Series in the Bodie mining district 9 

Figure 4. Normative compositions of lovos from the Murphy Spring Tuff 

Breccia of the Bodie mining district 11 

Figure 5. Normative compositions of dacite lavas of the Potato Peok 

Formation of the Pototo Peak-Bodie Mountoin areo 13 

Figure 6. Polar plot of the faults in the Red Cloud mine 15 

Figure 7. Cross section of the vein system of the Standard mine 17 

Figure 8. Vertical section through the Fortuna stopes, Bodie mine 18 

Figure 9. Face in o stope on the Fortuna vein, Bodie mine 19 

Figure 10. East-west section through the Fortuna stope in the north drift 

no. 1 of the 432-foot level of the Bodie mine showing the cross-cutting 

age relationships of the Fortuna and Gildeo veins 19 

Figure 11. Cross section of the veins of the Incline vein series showing 

their relationships to the Moyle Footwall fault, Standord mine 27 



Tables 

Table 1. Chemical anolyses and normative compositions of dacite flows and 

intrusives of the Silver Hill Volcanic Series, Bodie mining district 8 

Table 2. Chemical analyses and normative compositions, in percent, of 
docite flows from the Murphy Spring Tuff Breccia, Bodie 
mining district ond odjocent area 10 

Table 3. Chemicol analyses and normotive compositions, in percent, of 
dacite flows of the Potato Peak Formation, Potato Peak- 
Bodie Mountain area 12 



Table 4. Magnetic susceptibility measurements of rocks of the Bodie 

mining district and surrounding orea 20 

Table 5. Rock density measurements of rocks of the Bodie mining district 

and surrounding area 22 

Table 6. Production of gold and silver of the Bodie mining district. Mono 

County, California, from 1860 to 1941 32 

Table 7. Production, dividends, and operations of the Standard Consoli- 
dated Mining Company, Bodie mining district. 
Mono County, California 33 



Photographs 

Photo 1. View of Bodie in 1932 from Standord Hill 1 

Photo 2. View looking southeastward with the White Mountains in left 
distance. Glass Mountain in middle distance, and 
the Sierra Nevada in right distance 3 

Photo 3. View westward toward Sugarloaf 4 

Photo 4. Intrusive dacite of the Silver Hill Volcanic Series as exposed 

in the face of the Roseklip cut f, 

Photo 5. View to the southwest of the Bodie mining district 14 

Photo 6. View to northwest of central and northern sections of Bodie 

mining district 1^ 

Photo 7. Veined ond propylitically altered tuff breccio of the Silver 
Hill Volcanic Series, as exposed underground in 
the Bulwer tunnel 20 

Photo 8. Fractured ond propylitically altered intrusive docite of the 
Silver Hill Volcanic Series, as exposed underground 
in the Bulwer tunnel 21 

Photo 9. Ribbon quartz, containing fine-grained gold. Typical of the 

veins mined in the Bodie Bluff area 23 

Photo 10. Ribbon quartz veins in the intrusive dacite near the summit of 

Bodie Bluff 24 

Photo 11. Quartz-breccia zone, containing free gold, 436-foot level of the 

Bodie mine 25 

Photo 12. Fortuna vein, 400-foot level of the Bodie mine 26 

Photo 13. Ralston vein, just south of the Bulwer tunnel 28 

Photo 14. Argillicolly oltered tuff breccia of the Stiver Hill Volcanic 
Series, cemented by dork-gray, pyrile-rich chalcedony. 
700-foot level of the Red Cloud mine 29 

Photo 15. Lent shaft hoist house and office, as they appeared in 1895 30 

Photo 16. View of Bodie looking southwest from Stondard Hill. Excavation 
in foreground in port of large-scale sampling 
conducted by Yukon-Treodwell Company, Inc. in the spring of 1931 31 

Photo 17. View north toward Standord Hill 34 



ABSTRACT 

The Bodie mining district, located in the northeastern part of Mono County, California, was the 
source of gold and silver valued at more than $34,000,000 between 1860 and 1942. 

The district is underlain by volcanic rocks, including flows, plugs, ond pyroclostic deposits, principolly 
of dacitic composition. The oldest rocks ore those of the Silver Hill Volcanic Series, which consists of 
lovo flows, plugs, ond tuff breccio with minor layers of welded tuff. This sequence is overloin 
unconformably by lava flows and pyroclostic deposits of the Murphy Spring Tuff Breccia, which, in 
the southern part of the district, ore intruded by several plugs of porphyritic dacite. Flows and 
pyroclostic deposits of the Potato Peak Formation unconformobly lie upon units of the Silver Hill 
Volcanic Series in the northern port of the district. 

Investigotions of the geochronology of the rocks of the Bodie mining district, using the K-Ar method, 
indicate that the several units of the Silver Hill Volcanic Series were emplaced 8.6 to 9.4 m.y. ago 
and, furthermore, that they ore o locol phase of on extensive suite of colc-olkaline volcanic rocks 
(including bosalt, ondesite, docite, and rhyolite) that were erupted 7.8 to 9.5 my. ago in the region 
surrounding the Bodie mining district. Volconism ceased in the district and in the region surrounding 
it, following ore deposition in the district, and did not resume until 5 m.y. ago, when rhyolite plugs 
intruded rocks of docitic composition west of the district. 

Four plugs in the district were emplaced into vents from which the lava flows and pyroclostic deposits 
of the Silver Hill Volconic Series evolved. The largest plug, comprising Bodie Bluff ond Stondord Hill, 
is the host rock for the quartz veins from which more than 90 percent of the total production of gold 
and silver wos obtained. The other plugs at the Red Cloud mine. Queen Bee Hill, and Sugarloaf ore 
smoller in size and contain fewer quartz veins. 

The two major faults, the Moyle Footwoll ond the Standard Vein, along which movement was both 
pre- and post-mineral, were responsible for the formation of the grobcn in the Bodie Bluff-Standard 
Hill plug. Other pre-mineral foults ore the sites of vein deposition. The post-mineral foults, especially 
the Mono ond the Tioga, did much to offset the veins. 

Hydrofhermal alteration of the rocks was widespread in the district. Propylitic alteration, which is 
characteristic of the morgins of the district, occurred first; orgillic and potassic olterotion sequences 
occurred later and were more pervasive. Propylitically altered rocks ore greenish in color and contain 
chlorite, epidote, various cloy minerals, albite, pyrite, and minor quortz. The orgillicolly altered rocks 
ore usually light colored and contain montmorillonite, illite, sericite, quartz, and pyrite. They weather 
easily and form sparse croppings. The potossically altered rocks ore only locally light colored, and tend 
to resemble the original rock in color and texture. They show extensive development of odulorio, 
quartz, sericite, and pervasive, irregular veins of quortz-oduloria, with or without colcite. The silicic 
olterotion generolly occurred lost. Silica -altered rock is light colored, hard, and forms o capping on 
argillicolly altered rocks. 

K-Ar dating of odulorio in the gold-bearing quartz veins and in the hydrothermolly altered rocks 
indicotes that the alteration-mineralization occurred between 7.2 ond 8.6 m.y. ago and that the 
hydrofhermal system responsible for the mineralization lasted for about 1.4 m.y. 

Principol gold-silver production in the Bodie mining district came from severol systems of quartz veins 
in the intrusive docite plug of the Bodie Bluff-Stondord Hill area. Farther south, in the Silver Hill area, 
the mineralization wos pervosive, and the gold and silver were recovered from quortz veins ond 
irregular silicified zones in dacite flows and tuff breccia. The ore minerols include native gold, 
pyrorgyrite, tetrohedrite, stephonite, ond pyrite. The ratio of gold to silver by weight in the northern 
port of the district wos obout 1:12, whereas in the southern port of the district the ratio was obouf 
1:40. 

Mining activities ceased in the district in 1942, but interest in the mineral deposits in the district 
hos not reloxed. The intensely mineralized and mined bononzo zone of the Bodie Bluff Standard Hill 
area contains numerous narrow, gold-bearing quartz veins that, collectively, may constitute o lorge, 
low-grade deposit thot would be o fair target for further exploration and development. 



VII 




Photo 1. View of Bodie in 1932 from Standard Hill. Photograph by Fronds H. Frederick. 



INTRODUCTION 
Location 

The Bodie mining district (Figures 1 and 2), in which the 
mines and the now famous ghost town of Bodie are situated, is 
in the southern part of the Bodie Hills in northeastern Mono 
County. The two routes leading to the Bodie mining district from 
State Highway 31 and US Highway 395 are graded dirt roads 
that are usually closed durmg the winter. 

The B(xiic mming district, as originally defined in 1860, "shall 
extend in each direction from the Bodie claim, north, south, east 
and west, five miles" (Hakes, 1902). For many years, however, 
the Bodie mining district (Plate 1 ) has been confined to a nar- 
row tract of mountainous land which measures about 3 miles 
long and one mile wide, roughly encompassing a north-trending, 
ridge-hke feature. At the northern end, Bodie Bluff, the highest 
peak in the district at 9,(XX) feet in elevation, stands some 600 feet 
above the Bodie townsite. The southern end of the district is 
about one mile south of Sugarloaf, a conical shaped peak which 
is a prominent landmark of the area. Bodie Creek drains the area 
and flows throughout the year down Bodie Canyon. 

Field Work and Acknowledgments 

Most of the 1968 field season was spent by Chcsterman and 
Gray making a detailed geologic study of the Bodie mining 
district. R.H. Chapman made detailed magnetic and gravity 
surveys. Fortunately, several of the long-inaccessible mine tun- 



nels had been reopened in 1968 for prospecting, making it possi- 
ble for the writers to make limited observations underground 
and to collect samples of rock and ore for laboratory study. All 
geologic field work was plotted upon enlarged aerial photo- 
graphs and transferred to a topographic base, scale 1:4,800, 
which had been compiled in 1931 from a survey made by D.W. 
Ormsbee. 

M.L. Silberman of the U.S. Geological Survey assisted in the 
collection of rock and mineral samples for age dating and geo- 
chemical studies, and to him are tendered special thanks for 
making readily available all analytical data from the laboratories 
of the U.S. Geological Survey. The writers are especially grateful 
to the late E.W. Billeb of the J.S. Cain Company for making 
available unpublished notes and maps and for his many helpful 
suggestions and discussions. The late F.H. Frederick permitted 
the use of his maps as part of his long-continued interest in the 
district. 

Previous Work 

The Bodie mining district was organi/ed in I860, and several 
reports about il have appeared in various technical journals since 
that time The earliest, perhaps, of the published rep<irts is by 
Joseph Wasson (1879), who obtained much of his information 
from visits to the district and from early investigations made by 
Blake (1863, p 17), Silliman (1864, p 13-15). and Browne 
( 1 864, p. 17-18) Wasson's report was made for members of the 
New York Bullion Club and received limited circulation Mel- 
ville At wood ( 1879, p. 169) examined wall nxks from the mines 



CALIFORNIA DIVISION OF MINES AND GEOLOGY 



Bull. 206 




Figure 1. Index map of east-central Californio showing location of tfie 
Bodie mining district. 



at Bodie and reported his Findings before the California State 
Geological Society. 

Toward the middle of the 1880s, H.A. Whiting, superintend- 
ent of the Bodie Consolidated Mining Company, made an exten- 
sive study of the mines at Bodie and published his report in 1888 
(Whiting. 1888, p. 382-401). In the early 1900s, several investi- 
gations were made of the district; notable among these are stud- 
ies by R.P. McLaughlin (1907, p. 795), R. Gilman Brown 
(1907, p. 343-357), and AS. Eakleand R.P. McLaughlin ( 1917, 
p. 143-160). Much later still, Al-Rawi, then a graduate student 
at the University of California, reported upon the age of mineral- 
ization at Bodie (1968, p. 30). 



REGIONAL GEOLOGIC SETTING 




The Bodie Hills (Plate 1) comprise a complex mass of late 
Tertiary volcanic rocks (KleinhampI and others, 1975) which 
consists of lava flows, tuff breccia, and intrusive dikes, plugs and 
domes that were erupted from well-defined vent areas. The rcx'ks 
range in composition from rhyolite to basalt, and those of dacitic 
and andesitic compositions are most widespread and volumi- 
nous. The oldest volcanic rocks in the Bodie Hills, range in age 
from II to 29 m.y., consist of andesite, dacite, and rhyolite. and 
occur principally in the northeastern part of the area. These 
older volcanic rocks are overlain unconformably by ash tlow luff 
units that are mildly to intensely welded, but lixally non-welded, 
and include conspicuous black to dark brown vitric zones. They 
are trachyandesitic in composition and have an average age of 
9.4 my. 

Pre-Tertiary Basement 

R(Kks older than Tertiary are not exposed in the immediate 
area surrounding the Bodie mining district, but in adjacent areas 



Figure 2. Index mop showing locotion of plates 3, 4, and 5. 



to the west and northwest, the Tertiary volcanic rocks rest un- 
conformably upon pre-Tertiary metamorphic and granitic rocks 
that crop out usually as islands in the lava flows and pyroclaslic 
deposits (Chesterman and Gray. 1966; Chestcrman, 1968; and 
Chesterman and Gray. 1975) The metamorphic rivks include 
gneiss and schist of pre-Cretaceous age (Koonig. 1963) at Ma- 
sonic Mountain. 12 miles northwest of Bodie. and quarizofeld- 
spathic hornfels and greenstones of Paleozoic(?) and 
Mcsozoic(?) age (Chesterman. 1968) cast and northeast of Con- 
way Summit, 12 miles southwest of B<')dic. 

Granitic bodies iKCur in the Bixiie Hills and are generally 
found intrusive into the pre-Cretaccx)us metamorphic rocks. East 
of Conway Summit, there is a body consisting principally of 
biotile granite which has a Cretaceous age of 93.4 my (Chester- 
man, 1968). Masonic Mountain, that is at the northern end of 



1986 



GEOLOGY AND ORE DEPOSITS OF THE BODIE MINING DISTRICT 




Photo 2. View looking southeastward, with the White Mountains in left distance. Glass Mountain in middle distance, and the Sierra Nevodo on the 
right distance. In the middle-ground ore Bodie Townsite (B) , Bodie Bluff (BBj , Stondord Hill (St. H| , Silver Hill (SH) , lookout Peak (LP), 
Queen Bee Hill (QH) ond Sugorloof (S). Photograph by Norman F. Prine, U.S. Geological Survey. 



the Bodie Hills, is underlain by a body of granitic rock whose 
composition ranges from granodiorite to quartz monzonite. This 
body is presumed to be pre-Cretaceous in age (Koenig, 1963). 
A sample, referred to as black chert possibly altered from 
some underlying sedimentary formation, is said to have been 
collected at a depth of about 500 feet in mine workings near the 
Lent shaft (McLaughIm, 1907, p. 795) (Plate 2). Specimens of 
a fine-gramed, dense, dark gray to black rock were collected 
from the waste dump of the Dudley shaft. Presumably this is the 
underground workings to which McLaughlin referred. A micro- 
scopic examination of specimens of this material collected by the 
writers indicates that the rock is a well-indurated, fine-grained 
phase of welded tuff There are several outcrops of the welded- 
tuff phase of the Silver Hill Volcanic Series in the district, and 
It seems most likely that the malenal from the Dudley shaft is 
from a layer of this welded tuff that was encountered under- 
ground in the Dudley mine. 

Tertiary Rocks 

The most widespread volcanic rocks of the Bodie Hills consist 
largely of lava flows, tufT breccia, and intrusive plugs of dacitic 
composition, although lava flows, lufTbreccia, and intrusive bod- 
ies of rhyolilic, andesitic, and basaltic compositions arc present. 
Several small plugs of rhyodacilic composition iKcur near the 
mining district These rcK-ks form a blankcl-likc deposit and 
include the Mount Biedcman and Potato Peak Formations, the 
Murphy Spring TufT Breccia, and the Silver Hill Volcanic Series 



(Chesterman and Gray, 1966). Their range in age is approxi- 
mately 8.6 to 9.4 m.y. 

Lying unconformably upon the late Miocene volcanic rocks 
are lava flows of andesitic and ba.saltic composition of the Cedar 
Hill-Trench Canyon complex (Al-Rawi, l<}69). Their range in 
age is 2.2 to 3.6 m.y. 

GEOLOGY 
OF THE BODIE MINING DISTRICT 

Rocks of the Bodie mining district (Plate 2) include extrusive 
and intrusive lavas and pyrtKlastic deposits of the Potato Peak 
Formation and Murphy Spring Tuff Breccia (Chesterman, 1968, 
p. 51-60) and of a unit referred to as the Silver Hill Volcanic 
Series (Chesterman and Gray, l'>66, p 14), all of which appear 
to range in age from 8.6 to 9.4 my. (Silbcrman and others, 1972, 
p. 601). 

Silver Hill Volcanic Series 

The riKks of the Sihcr Hill Volcanic Series (Chesterman and 
Gray, 1966, p. 14) crop out extensively in the liodie mining 
district. They consist of inlerlayered lava flows and lufTbreccia, 
and intrusive plugs, and are named after Silver Hill, a small hill 
near the center of the district (Plate 2) Outcrops of thi-sc rcKks 
that show contacts are nol common, but their relationships arc 
well exposed in underground mine workings. It appears (hat luff 



CALIFORNIA DIVISION OF MINES AND GEOLOGY 



Bull. 206 







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Photo 3. View westward toword Sugorloof, o plug of docite of the Silver Hill Volconic Series ot the southern end of the district. Snowcapped Sierra 
Nevada in distance. 



breccia layers were deposited and are overlain by lava flows and 
more layers of tuff breccia. The principal tufT breccia layer, 
which underlies a large portion of the district, is about 400 feet 
thick. Remnants of a thinner tuff breccia layer caps Silver Hill 
and occupies the small graben near Standard Hill; it has been 
extensively altered and probably is no more than 150 feet thick. 

Several flows are exposed on the surface, and some are ex- 
posed in mine workings, especially the deeper ones. One compos- 
ite flow in particular, which underlies much of the district, is 
between 500 and 700 feet thick and appears to be composed of 
two units. The upper unit is biotite-nch dacilc and the lower unit 
is hornblende-rich dacite. The contact between the two was not 
observed. 

Four plugs of dacite intrude the tuff breccia layers and flows 
of the Sliver Hill Volcanic Series. The largest plug (xcurs at the 
northern end of the district and makes up the bulk of the rocks 
that form Bixlie Bluff and Standard Hill (Plate 2) The other 
plugs are near the Red Cloud mine, al Queen Bee Hill and at 
Sugarloaf (Plate 2) These plugs are composed of hornblende 
dacite and are probably connected at depth. 

In general, the sequence of pyriKlastic deposits and inlerlay- 
ered lava flows dips from 5 to 15 degrees in a southerly direction 
except near the plugs where they dip outward al steefwr angles. 

TVff BRECCIA 

Throughout much of the Bodie mining district the rocks of the 
Silver Hill Volcanic Scries are difficult to discern because Ihcv 



have undergone alteration. The tuff breccia is best exposed in 
scattered exposures at the north end of the district, where a 
stratigraphic section consisting of about 200 feet of pyroclastic 
rocks was studied and measured The basal unit is gray luff 
breccia which is massive and sufTiciently indurated to form low 
cliffs. It has indistinct layering and consists of angular and 
subangular blocks of dark- and light-colored dacite from a few 
inches to several feet across enclosed in a matrix of volcanic ash 
and mineral grains. At least 125 feet of this basal unit is exposed. 
The basal, gray tufT breccia is overlain unconformably by a layer, 
from one to 60 feet thick, of well-induraicd, buff-colored tufT 
breccia which is massive, ptwrly layered, and consists of angular 
fragments of tan-colored tuff breccia. Grading into it is a layer 
of black welded lutT. which ranges in thickness from 4 to 6 feet. 
The welded tuff has been referred to by various people as obsid- 
ian, and in color, texture, structure, and nuxle of ivcurrence it 
resembles other layers of welded tufflhat (Kcur in several of the 
volcanic formations in the Btxiie Hills (Chesterman, I'JbS, p. 
49-5.'') At Us contact with the underlying luffbrcccia the welded 
luff IS dark brown, and the color transition from dark welded tuff 
to buff-colored tuff breccia is gradual. 

The welded tuff is dense, has a well-developed vitroclaslic 
texture, and consists of angular and rounded fragments of light 
to dark gray and dark brown porphynlic dacite enclosed in a 
dark gray, fine-grained groundmass streaked with black glass. 
The lithic fragments rarely cxcecxi several inches in diameter, 
and Ihe average size is less than one-half an inch The dacite 
clasls contain euhedral phenocrysts of glassy while plagiocla.se 



1986 



GEOLOGY AND ORE DEPOSITS OF THE BODIE MINING DISTRICT 



(An ivio). black hornblende, and deep-brown biotite. A small 
mass of dark gray to black welded tufT crops out in the eastern 
part of the district, about 700 feel southeast of the Defiance shaft 
(Plate 2). It is completely enclosed in I utT breccia overlain by 
hornblende-rich dacile, all in a triangularly shaped fault block. 
Still larger and more prominent outcrops of the welded tuff are 
exposed in the walls of Milk Ranch Canyon in the northwestern 
part of the study area. Although outcrops of the black welded 
luff are neither very large nor abundant, it is apparent from their 
distribution that the rock cmered nuich of the Bodie mining 
district. 

Much of the pyroclastic riK-k of the district probably was 
derived from vents in the district, which are now sites of plugs, 
and because of the lack of sorting and layering, they suggest a 
lahar mode of deposition. 

Lying above the black welded tuff in what appears to be a 
conformable relationship is a sequence of weakly indurated tuff 
breccia layers. Because of scarce and inadequate exposures of 
this sequence of tuff breccia layers, it was not possible to ascer- 
tain its thickness or structural characteristics. It is composed of 
angular and subangular blocks and fragments of medium-gray 
dacite, ranging in diameter from a few inches to one foot and 
enclosed in a matrix of fine-grained volcanic ash and mineral 
grains. The sequence of upper tuff breccia layers is unconforma- 
bly overlain by mtxderately indurated and layered tuff breccia of 
the Potato Peak Formation. 

The clasts in all of the tuff breccia layers, except the black 
welded tuff, range in color from light and medium gray to brown 
and tan. The rock is principally hornblende dacite in composi- 
tion and contains phenocrysts of black hornblende and glassy 
white plagioclase enclosed in a fine-grained, light gray ground- 
mass of plagioclase, hornblende, minor biotite, and devitrified 
volcanic glass. 



DACITE FLOWS 

Based on sparse information from records of extensive mining 
operations in the district, several fiows of dacite, separated by 
relatively thin interlayers of luff breccia, were encountered in 
shafts. In the Lent shaft (Plate 2), which extended to a depth 
of 1,200 feet below its collar elevation of 8,422 feet, a layer of 
dacite about 8 feet thick was encountered at a depth of 650 feet. 



Composite Flow 

A composite flow covers much of the district and is exposed 
in many of the mine workings. The composite flow is made up 
of two rather distinct units: The upper unit is biotile-rich dacite 
and the lower unit is hornblende-rich dacite. Because of the lack 
of adequate exposures, it was not possible to ascertain the thick- 
ness of the composite How or to delineate its individual units and 
their contact relationships, but it is estimated that the thickness 
of the flow is between 5(X) and 700 feet. The interrelationship of 
the two units is constant throughout the district. 

Exposures of unaltered units of the composite flow are uncom- 
mon, primanly because of extensive hydrothermal alteration of 
the rocks, but relatively unaltered samples were obtained on the 
south side of Queen Bee Hill and in the underground workings 
of the Red Cloud mine (Plate 2). 

The lower hornblende-rich unit has well-developed platy 
jointing and conspicuous necdie-like. black crystals of horn- 
blende. The upper biotite-rich unit lacks the platy structure but 
shows blix'ky jointing, conspicuous black crystals of biotite, and 
an equigranular appearance of the plagioclase phenocrysts. 



LOWER UNIT. The hornblende-rich dacite is light gray, por- 
phyritic, and contains phenocrysts of plagioclase and hornblende 
enclosed in a fine-grained groundmass of mineral grams, niicro- 
phencKrysIs of biotite, and partly dcMtrified volcanic glass. The 
plagiiK'lase, with phenocrysts of euhedral and subhedral grains, 
ranges in composition between intermediate and calcic andesine 
(An„,^), and shows multiple twinning and oscillatory zoning. It 
is remarkably fresh in spile of the generally slightly altered con- 
dition of the rock, and it constilulcs about 60 percent of the 
phenocrysts. 

The hornblende is light brown and greenish-brown, is weakly 
pleochroic, and occurs in euhedral and subhedral grains, of 
which the larger are partly resorbed and the smaller are com- 
pletely resorbed, leaving residues of tiny grains of black iron 
oxide. The hornblende constitutes about .^0 percent of the pheno- 
crysts. Biotite is dark brown in color and strongly pleochroic 
from Ian to dark brown. It is in euhedral and subhedral grains, 
all of which are resorbed to varying degrees. The biotite consti- 
tutes about 10 percent of the phenocrysts. 

The groundmass constitutes about 30 percent of the rock It 
consists of plagioclase microlites which show simple polysyn- 
thelic twinning and are probably sodic andesine in composition. 
They are unaltered and (K'cur with microphenocrysts of horn- 
blende and biotite in partly devitrified volcanic glass 

Samples of altered hornblende-rich dacite from the under- 
ground workings of the Red Cloud mine (Plate 2) and from 
outcrops elsewhere in the district illustrate very well the types 
and degrees of hydrothermal alteration to which the rock has 
been subjected. 

UPPER UNIT. The biotite-rich dacite of the upper unit ranges 
in color from pale gray to pinkish gray. It is porphyritic and 
contains phenocrysts of dark brown biotite, scarce black horn- 
blende, and glassy-white plagioclase enclosed in a fine-grained 
groundmass. Phenocrysts make up about 60 to 65 percent of the 
rock. The plagioclase phenocrysts are in euhedral and subhedral 
grains, which occur singly or in clusters. They show multiple 
twinning, oscillatory zoning, and range in composition between 
sodic and intermediate andesine (An^M,,). Alteration is present 
in the large phenocrysts and manifests itself as a narrow zone 
immediately beneath a clear glassy rim on the grain. The plagio- 
clase phenocrysts constitute from 40 to 50 percent of the pheno- 
crysts. The groundmass plagioclase is in small microlites that 
show simple polysynthetic twinning, and has a composition of 
sodic andesine. 

Sanidine occurs as small rectangular-shaped euhedral grains 
which show simple carlsbad twinning. The grains are skeletal 
and have dark shadowy interiors. They are not altered and con- 
stitute about 5 percent of the rock. 

The femic minerals are generally resorbed. Relatively fresh 
biotite occurs in dark brown, strongly pleochroic euhedral grains 
which constitute ab<iul .10 to 40 percent of the phenocrysts. 
Hornblende is subordinate to the biotite, and where it is incom- 
pletely resorbed it (xcurs as deep-green euhedral and subhedral 
grains which are weakly ple(x;hroic. 

The groundmass gla.ss is usually pinkish-Ian in color and 
somewhat devitrified. It constitutes aboul .15 to 40 percent of the 
rock. 



INTRUSIVE DACITE 

Aside from dikes, which crop out rarely but were cncounlcrcd 
in mines, the bulk of the intrusive dacite occurs in plugs. The 
dacile shows well developed fiow banding, especially near con- 
tacts with wall rocks, and shows a range in color from pale gray 



CALIFORNIA DIVISION OF MINES AND GEOLOGY 



Bull 206 




li^ 



Photo 4. Intrusive doclte of the Sliver Hill Volcanic Series as exposed in the face of the Rosekllp cut, on the south side of Standard Hi! 
Photograph by M.L. Silberman, U.S. Geological Survey. 



to medium gray, rarely pinkish (Photo 4). The dacite is porphy- 
ritic with phenocrysts of hornblende occasionally up to 10 mm 
in length and plagioclase as much as 5 mm across; biotite. when 
abundant, tends to form cuhedral plates as much as 3 mm across. 
The phenocrysts range in amount from 40 to 80 percent of the 
rock. The groundmass is fine grained and generally contains 
from 10 to 15 percent volcanic glass that is more or less devitri- 
fied. 

The plagioclase, which constitutes 40 to 60 percent of the 
phenocrysts, occurs as euhedral to subhedral grains which show 
multiple twinning and complex oscillatory zoning. Their compo- 
sition range is from sodic to intermediate andesine (Anl^„). 
Many of the larger euhedral-shapcd grains show considerable 
alteration, generally as a narrow zone of calcite and scricite 
surrounding an unaltered core and rimmed by a narrow zone of 
clear, glassy feldspar which lacks twmning and has an extinction 
position different from the interior feldspar. Inclusions of vol- 
canic glass commonly form a narrow zone immediately beneath 
the clear glassy rim of the grain. Other inclusions include femic 
minerals and magnetite. 

Sanidinc phenocrysts. as much as 3 mm across, are common 
in the dacite that forms the eastern part of the plug at Btxlie 
Bluff, and constitute about 40 percent of the phenocrysts. They 
are euhedral. gla.vsy where unaltered, and show carlsbad twins. 



Altered sanidine phenocrysts contain carbonate and sericite. 

Feldspar in the groundmass. which constitutes about 20 per- 
cent of the rock, is sodic andesine and sanidme. The sodic ande- 
sine occurs as small lath-shaped grains and as microlites which 
show simple polysynthetie twinning and are generally unaltered. 
The sanidine is in rectangular-shaped crystals which are com- 
monly uniwinned and generally unaltered. 

Phenocrysts and microphenocrysts of bioiite and hornblende 
are largely resorbed and altered, but unaltered phenocrysts are 
dark brown in color and strongly pleochroic. The strongly re- 
sorbed femic phenocrysts arc represented by residual accumula- 
tions of small black grains of iron oxide. Partly rcs<irbed grains 
contain the residual iron oxide grains, calcitc, and the unaltered 
mineral. Apatite and magnetite occur as inclusions in the unal- 
tered biotite The femic minerals comprise generally 10 to 40 
percent of the total phenocrysts. Apatite and sphene are accesso- 
ry minerals. 

The volcanic glass is usually completely devitnfied to crypto- 
crystalline and microcrystalline aggregates. Tridymite occurs as 
small, wedge-shaped, twinned crystals, but it is rare. 

The intrusive dacite of the Bodie Rluff-Slandard Hill plug 
(Plate 2) has undergone p«itas.sic alteration as well as livally 
intense argillic alteration (sec section on hydrolhcrmal altera- 
tion). 



1986 



GEOLOGY AND ORE DEPOSITS OF THE BODIE MINING DISTRICT 



CHEMICAL COMPOSITION 

The lava flows of the Silver Hill Volcanic Series in ihe Bodie 
mining dislnct have a range in composition from iatite-andcsitc 
through latite and dacite to rhyodacite. Fourteen chemical anal- 
yses, available through the U.S. Geological Survey, are given in 
Table I. Norms were calculated for these rocks and plotted on 
a Streckeisen diagram (Figure }). The spread of points on the 
diagram reflects the alteration effects on the rix;ks. RiKks of the 
plug at Bodie Bluff-Standard Hill, in spile of iheir apparent 
freshness, have undergone considerable potassic alteration; the 
added potassium shows up principally in the groundmass. The 
comp<isite flow, of which analysis 12 is from the upper biotite- 
rich unit and analysis 13 is from the lower hornblende-rich unit, 
appears to be fairly constant in chemical comptisition. regardless 
of its two-phase division on a basis of mineralogical composition. 

AGE OF THE SILVER HILL VOLCANIC SERIES 

Biotite and hornblende separated from plugs and flows of the 
Silver Hill Volcanic Series have been dated by the K-Ar method. 
The flows have ages ranging from 8.8 i .2 m.y. to 9.1 ± .5 m.y., 
and the plugs have a range of 8.3 ± .4 my. to 9,2 ± .5 m.y. 
(Silberman and others. 1972. p. 601). 

Murphy Spring Tuff Breccia 

Lava flows and pyroclastic deposits of the Murphy Springs 
Tuff Breccia (Chesterman. 1966. p. 51-52) crop out extensively 
in the southern part of the Bodie mining district. The formation 
consists of flows and plugs of dacite and tufT breccia of dacitic 
composition. 

The pyroclastic member of the Murphy Springs TufT Breccia 
in the district consists pnncipally of tuff breccia and minor luff 
layers. The tuff breccia in the vicinity of Sugarloaf (Plate 2) has 
a maximum thickness of about 750 feet. The source vents for 
much of the pyroclastic deposits in the district are at the south- 
ern end of the district, where the tuff breccia dips steeply away 
from central plugs of dacite. The dip of the layenng in the tuff 
breccia flattens greatly and is generally in a westerly direction. 

Individual lava flows cannot be traced for more than a few 
hundred feet because of poor exposures, but they tend to range 
in thickness from a few feet to several tens of feet. Several flows 
in the low hill west of Sugarloaf. which contain very little inter- 
layered fragmenlal or pyroclastic material, have an aggregate 
thickness of about 375 feet; on the northwest slope of Lookout 
Peak, just within the distnct. the dacite lava flows have an 
aggregate thickness of at least 450 feel. Flow banding within the 
flows locally dips in many directions, but in general the flows 
tend to have a low to moderate dip to the west and southwest. 

PYROCLASTIC DEPOSITS 

The luff breccia is a ma.ssivc rock in which layering is most 
distinct near the source vents. Exposures of luff breccia arc 
scarce, principally because of removal by erosion, but the pres- 
ence of the rock can easily be ascertained by the large number 
of small rock fragments and angular boulders up to 5 feel across 
lying on the surface 

Tuff breccia exposed west of Sugarloaf can he divided into a 
gray luff breccia unit and an underlying brown luff breccia. The 
color of the clasts contained in the two units is the ba,sis for Ihe 
division. The gray tuff breccia appears to be restricted lo this 
small area, whereas the brown luff breccia is widely distributed 

Tlie gray tuff breccia lies unconformably upon the brown luff 
breccia, and is estimated lo be approximately 170 feet thick 



Layering is indistinct in the rock, but indications are that the 
general dip of the unit is toward the southwest at a low angle. 
The clasts are pale lo medium gray in color and occur as angular 
lo subangular btiulders and fragments that range in size from a 
few inches to several feet across, enclosed in a matnx of pale gray 
rock, mineral fragments, and volcanic ash. The clasls are com- 
prised of porphyritic hornblende dacite. in which phenocrysis of 
black hornblende, glassy feldspar, and scarce black biotite are 
enclosed in a fine-grained matrix of plagioclase and partly devi- 
trified volcanic glass. Hornblende compnses about 40 percent of 
the phencKrysts. It occurs in euhedral grains which are pleo- 
chroic from dark brown to greenish brown. A few of the grains 
are partly resorbcd and contain granules of iron oxide concen- 
trated at the central part of the host grain Plagioclase (Ann,,) 
constitutes about 40 percent of the phenocrysis. It occurs as 
euhedral to subhedral grains which show multiple zoning, inclu- 
sions of volcanic gla.ss, and evidence of re-solution during a 
complex cooling history. The interior part of some of the larger 
plagioclase phenocrysis are altered to carbonate and kaolin, 
which are surrounded by a rim of glassy feldspar. Black biotite 
is in euhedral phenocrysis that are strongly pleochroic and part- 
ly resorbed. 

The groundmass plagioclase is in the form of small euhedral 
and subhedral lath-shaped grains which are more sodic in com- 
position than the plagiocla.se phenocrysis. Excepi for the 
groundmass plagioclase and microphenocrysts of hornblende 
and minor biotite, the remainder of the groundmass is cloudy, 
partly devitnfied volcanic glass. 

The clasts in the brown tuff breccia unit are hornblende dacite, 
angular and subangular, and range in size and shape from sharp 
angular fragments several inches across to large angular blocks 
as much as 5 feet in diameter. The average clast size is ab<iut one 
fool. Near Ihe source vents, this tuff breccia unit has distinct, 
massive layering with individual layers that range in thickness 
from several feet to several lens of feel. 

The clasts range in color from dark reddish-brown to pale 
pinkish-brown The rock, similar petrographically lo the dacite 
in the gray tuff breccia, is porphyritic and contains phenocrysis 
of basaltic hornblende and plagitKlase enclosed in a fine-grained, 
microcryslalline and glassy groundma.ss. The basaltic horn- 
blende IS strongly pleochroic, from pale yellowish- to deep 
golden-brown, and is the principal contributor lo Ihe color dis- 
tinction between the clasts in the two tufT breccia units. The 
groundmass has a pale pinkish-yellow color due to the secondary 
limonite which contributes to Ihe overall color of the rock. The 
color of the scarce biotite is deep golden brown, identical to that 
of Ihe basaltic hornblende. 

Because Ihe clasts in Ihe two luff breccia unils arc hornblende 
dacite and differ only in the type of hornblende, one can assume 
that the brown dacite was extruded at a higher temperature than 
was ihc gray dacite. and that Ihe color differences are due princi- 
pally lo the presence of brown basaltic hornblende and brown 
colored glass in Ihe brown dacite. The pyrix-lastic deptisits of the 
Murphy Spring TufT Breccia lie unconformably upon unils of the 
Silver Hill Volcanic Series. 

DACITE FLOWS AND PLUGS 

I^va flows of the Murphy Spring Tuff Breccia arc dacitic in 
composition and crop out principally in the s<Hilhern and s<iuth- 
caslcrn parts of the Hodic mining dislnct The thickness of indi- 
vidual flows within the district could not be measured, but 
several flows outside the dislnct on the south flank of Ltxikoul 
Peak (name applied by Icxral residents), the west fiank of which 
lies within the district, range in thickness from 10 to 20 feel 



CALIFORNIA DIVISION OF MINES AND GEOLOGY 



Bull. 206 



Table 1. Chemical analyses and normative compositions, in percent, of the docite flows 
and intrusives from the Silver Hill Volcanic Series in the Bodie mining district. 



CHEMICAL ANALYSES 



10 



11 



12 



13 



14 



SiO, 

A 1,0, 

feA, 

FeO 

MgO 

CaO 

Na,0 

K,0 

T-0, 
PA 
MnO 
ZrO, 
CO, 

Total 



63 67 


6866 


6211 


6383 


6266 


62 14 


6152 


60 30 


62 44 


6115 


66.23 


64 15 


64 20 


6407 


1602 


1453 


1710 


1621 


1692 


1721 


1659 


1678 


1744 


1733 


16.31 


1649 


1738 


1662 


260 


361 


4 70 


280 


300 


360 


233 


342 


331 


332 


280 


4.00 


422 


350 


ISO 


032 


020 


140 


150 


1.60 


2.33 


161 


120 


171 


100 


052 


036 


068 


220 


052 


130 


220 


240 


2.00 


263 


2.81 


190 


222 


160 


190 


0.95 


120 


3.30 


076 


19 


250 


4 10 


430 


476 


5.33 


321 


463 


340 


380 


342 


400 


3.00 


231 


031 


3.50 


360 


450 


364 


3.22 


401 


403 


350 


360 


392 


400 


511 


7.32 


10.91 


4.60 


310 


230 


2 73 


251 


261 


272 


340 


300 


3.21 


340 


135 


120 


240 


201 


1.42 


1 11 


129 


281 


281 


1 71 


085 


150 


1.21 


1.40 


062 


053 


056 


056 


071 


080 


070 


073 


067 


074 


050 


062 


071 


069 


026 


023 


019 


025 


029 


035 


030 


034 


031 


033 


025 


026 


038 


032 


006 




004 


009 


009 


004 


007 


13 


009 


10 


O10 


010 


004 


004 


000 


























0.00 


000 






005 




004 


1 11 








006 


008 




006 


0000 


100.00 


10000 


10000 


100.00 


100.00 


100.00 


100 00 


100 00 


10000 


10000 


10000 


10000 


10000 



NORMATIVE COMPOSITIONS 



Ouanz 
Corundum 
Onhociase 
Albile 
Anorlhile 
Wollaslonile 
Enslalile 
Ferrosilile 
Magnetite 
Hematile 
llmenile 
Rulile 
Apatite 
Calcite 
Total 
Salic 
Femic 



16923 


25.492 


0167 


1989 


30170 


43 421 


25413 


19 508 


14689 


2273 


5485 


1298 


0245 




3.774 






3609 


1 179 


0677 




0175 


0616 


546 


98662 


98808 


87 363 


92 504 


11.299 


6305 



18.051 


17104 


16034 


19056 


17390 


20316 


15.007 


24039 


21739 


21438 


18.465 


1633 


0534 


0421 


2304 




2936 


0.125 


1419 


1229 


2159 




27 193 


18335 


13599 


16144 


14847 


15400 


16.074 


20.100 


17714 


18997 


20114 


29 628 


32183 


38101 


30 823 


27214 


33 925 


34 099 


29.628 


30438 


33153 


33 884 


10.457 


18462 


18804 


14574 


23 940 
106 


13882 


20.819 


14861 


16634 


14 451 


17317 
0.032 


5 481 


5983 


4984 


6552 
1330 


7008 


4 743 


5520 


3986 


4 728 


2377 


2992 


3 184 


3073 


2070 


3374 
















0605 


0883 


1.554 




3483 


2.225 


3717 


2101 


0^05 




0323 


1.064 


1.350 


1520 


1326 


1.015 


1773 


0.761 


1352 


3.855 


4.219 


3.281 










1.393 


1275 


1397 


O950 


1 177 


0850 


1312 


0592 


0688 


0830 


0719 


0809 


0736 


787 


0592 


615 


0266 


759 


0114 




0091 


2531 








0137 


0182 


0904 


137 


98 003 


98 595 


98 908 


98 731 


97 205 


97 211 


98 306 


99.164 


98516 


98815 


98615 


86936 


86619 


86959 


82.899 


83.391 


86459 


86124 


90045 


87 753 


90198 


89 781 


11040 


11.976 


11949 


15832 


13815 


10752 


12 192 


9118 


10 762 


8616 


8835 



(BH-27I*) Homb)endc-bioiited«aierrcpfT) theinirusiveda' 

cue of lh« Silver Hill Vokanic Senes of ihe Bodie BlufT- 

Sundard Hill plug^ colkcled from Ihe dump of (he New 

Standard thaft in ihe ioulh central p«n of Sec 9. T4N. 

R27t 

(BH-272) Hornblende btolite dacitc Trom the intrusive da- 

cite of the Silver Hill Volcanic Senes of the Bodie BlufT 

Standard Hill plu^ collected Trom a thallow prospect pit at 

Ihe lummil of Bodie Bluff in the central pan of Sec. 9, T4N. 

R27E 

(II4G-1) Biolile-hornbtende dacile from the intrusive da- 

cile of Ihe Silver Hill V<ilcanic Ser»e» of the B<xlie BlufT 

Standard Hill pluf. cotleclcd from ■ tunnel near the vtuth- 

ern margin of Sec 10. T4N. R27K, abtml one -quarter mik 

Mnilhwetl of the Gray Mill 

(ll^Wi B) Hornblende dacile frimt Ihe inlruiive dacile of Ihe 

Silver Hill Volcanic Senc* of the Bodie BlufT-Slandard Htll 

plug, collected from the M)-called Rineklip cut in vKilh 

tenlral part of Sec 9. T4N. R27K 

(III I 17) Hotnhlende ila«.iir from the iniru\ue d»i lie of ihr 

Silver Hill Vokanic Sene% of the Quern Bee Hill plug, col 

Iccled near the tummit of Queen Bee Hill m (he «ve%ucntral 

pan of Sec 21. T4N. R27E 

(8H J0> Hofnbkttdebiolile dacite from the homblcfMle- 

rxh unit of the compoulc tUrm of the Silver Hill VokanK 



Senea. collected near (he eutcm bour»dary of Sec 20. T4N. 
R27E 

7 (BH-273) Homblende-biolite dacile from the intrusive da- 
ate of (he Silver Hill Volcanic Senes of the Queen Bee Hill 
plug, collected on the nonh ude of Queen Bee Hill in (he 
we»t central pan of Sec 21. T4N. R27E 

8 (BH-I$) Biot lie- hornblende dacite from a lava fV>w of Ihe 
Silver Hill Volcanic Senes. collected in (he nonh ccnlral 
pan of Sec 21. T4N. R27E. about 300 feci u>uthe»tcrly 
from the Red Cloud ihaD 

** (S# 1 ) Homblende-btotitc dacitc from the intrxuive Silver 
Hill Volcanic Senes of the Sugartoaf plug, collecled at the 
summit of Sugafloaf in the touthwcst quaner of Scc- 21, 
T4N. R27E. 

10. (BH-26) Homblende-biolilc daate from the intrusive Silver 
Hill Volcanic Senes of ihe Sugarloaf plug, collecled from the 
nonh slope of Sugarloaf in the loulhwcst quaner of Sec 2 1 . 
T4N. R27E- 

11 (S36I0) Btotitc-honiblende dacitc of the Silver Hill Vol- 
canic Senes from a small intrusive plug, collecled jusi out> 
tide (he Bodie mining disinci in the wcsi central pan of Sec 
1 7. T4N. R27E. On the basu of cbcnucal compositton and 
abundance of biotKc. (he rock might be considered as 
rhyodaate. 

12 (Lilac) Honiblende daalc from the homblende-rKh unit of 



(he composite flow of dacite of (he Stiver Kill Volcvuc 
Senea. collected from a small hill m (he ikortbeast quarter of 
Sec 16. T4N. R27E. about 1.000 feel eastcrt) from the 
Dudley shaft 
. (BH-16) Btoute-bomblendc dMste from the bwute-nck 
unit of the oompoaile daate flow of (he Silver Hill Vokamc 
Scnct, coUected from a prominent cropping in the iou(hcut 
quarter of Sec. 16. T4N. R27E 

(BH-32) Biodte-homblcDde daale from the bMtitc-nch 
unit of (he compoaitc daate flow of the Silver Hill Vokanic 
Senes, collected near (be top of a small hill tn the center at 
Sec 21. T4N. R27E 



For samples 6 af>d 1 4. method of analysts used is the ungle 
•olulKin procedure docnbed in US Geological Survey Pro- 
fessional Paper 5758. p 187-141 ( |Q67) Ana)>-stv P D- 
more. S Botts. L Artts, J Kdaey. H Smith and t Gknn 
For samples 1. 2. 3. 4. 5. 7. g. 9. la II. 12. and U. methods 
of analysu used are descnbed m US Geokipcal Survey 
Bulletin 1 144- A. suppiemenied by atomic abaorpliOB Ana- 
lys(s. P Elmore. S Bo((v G Chloc. H Smith. J Kehey. L- 
Ann and J Glenn 



' liMbcatrt fieM nuinbrt 



1986 



GEOLOGY AND ORE DEPOSITS OF THE BODIE MINING DISTRICT 





60, 




'■ I 



I 
J- 



\ 



Rhyohte / , . Rhyodacite.v. \ Dacite 



/ 



.g/ / 



/ 




'. '4« '«.'«8.' 




Latite - andesite 



\ 



.1 

* PC'_ : - 
F«ld«por 



Latife 



Latite - basalt 



\. 



y^ .-■ugiutloii 
Ftldtpor 



Figure 3. Nonnative compositions of rocks of (he Silver Hill Volcanic Series in the Bodie mining district plotted on o Streckeisen 
diogrom. (lumbers refer to analyses in Table 1. Diagram adapted from Streckeisen (1967, p. }61J. 



Individual flows wedge out laterally, and the thickesi section of 
them (about 450 feet) is in the vicinity of Lookout Peak — one 
of the local vents for much of the matenal for the Murphy Spring 
Tuff Breccia. The plug at Liwkout Peak is somewhat circular in 
plan and is about half a mile in diameter. Another plug lies about 
one mile south of Sugarloaf It has a circular plan and is about 
one quarter of a mile in diameter (Plate 2). 

TTie dacite in the plugs and flows is dense, shows flow banding, 
and ranges in color from pale to dark gray and medium brown. 
Brown is the predominant color, especially in the plugs. The 
dacite is porphyrilic, and 30 to 40 percent of the rock is made 
up of phenocrysis enclosed in a fine-grained groundmass com- 
posed of mineral grains and volcanic glass. 

About 50 to 60 percent of the phenocrysts are plagioclase 
They occur in cuhedral and subhcdral grains which show multi- 
ple twinning and oscillatory zoning. The interiors <if a few larger 
phenocrysts arc altered to calcite and kaolin and have glassy 
clear nms of more sodic plagioclase The unaltered plagioclase 
phenocrysts range in composition from sodic andesine to calcic 
andesinc (Ann«). and the average composition is intermediate 



andesine (An,,). Inclusions of volcanic glass are common, espe- 
cially in the rims of the larger phenocrysts. 

About 30 to 35 percent of the phencKrysts arc hornblende and 
biotite. The biotite. usually less abundant than the hornblende, 
is pleochroic and ranges from pale yellow to dark brown, but 
where ass(Kiatcd with basaltic hornblende, it is reddish- to 
golden-brown and strongly pleiKhroic, Many of the biotite 
grains have undergone resorption, which leaves a residue of 
black iron oxide grains at their nms Hornblende in the gray 
dacite occurs in euhcdral and subhcdral grains that are mtxler- 
ately pleochroic and range from pale yellowish-grccn to deep 
yellowish-brown. Many of the grains are partly to completely 
resorbed and leave dark nms around unaltered hornblende or 
residues of dark iron oxide grains. The amphib«ile in the brown 
dacite IS basaltic hornblende It is strongly pictxhroic and ranges 
in color from pale yellowish- to deep reddish-golden brown. 
Those grains that are strongly resurbcd show subhcdral form, 
whereas those that arc weakly resorbed show cuhedral form 

The groundmass of the dacite, regardless of the color of the 
rock, appears lo consist of an aggregate of microlites of plagio- 



10 



CALIFORNIA DIVISION OF MINES AND GEOLOGY 



Bull 206 



clase, microphenocr>'sts of short prismatic plagioclase, euhedral 
hornblende and biolKc, and partly devitrified volcanic glass. The 
plagioclase is probably sodic andesine or calcic oligoclase in 
composition The mafic minerals in the groundmass are general- 
ly partly to completely resorbed. The groundmass of the brown 
dacite has a pale bufT color due to secondary limonite. The partly 
devitrined glass is cloudy and contains minor carbonate and 
kaolin. 

CHEMICAL COMPOSITION 

Four new chemical analyses, all by the U.S. Geological Sur- 
vey, are given in Table 2 for the dacite of the Murphy Spring TufT 
Breccia. Three of these analyses are of samples collected in the 
Bodie mining district, and the fourth is from a prominent out- 
crop of dacite near Murphy Spring, about 2.5 miles west of the 
district (Plate 1). Norms for these analyses are plotted in Figure 
4. The spread of the points on the diagram indicates a change 
of composition due to different source vents for the samples. 
Points 2, 3, and 4 represent samples from the flows near the large 
plug at Lookout Peak and Point 1 represents the sample from 
a flow whose source is near Murphy Spring (Plate 1). 



Table 2. Chemical analyses end normative composition, !n 
percent, of the dacite flows from the Murphy Spring Tuff 
Breccia of the Bodie mining district and adjacent areo. 

CHEMICAL ANALYSES 





1 


2 


3 


4 


SO, 


60.34 


6154 


63 56 


64 36 


A1A 


teao 


1771 


1752 


1694 


FeA 


332 


450 


420 


3 19 


FeO 


161 


068 


0.36 


130 


MgO 


181 


200 


1.30 


liO 


CaO 


493 


510 


3.S0 


398 


Na,0 


3.82 


3.90 


3.70 


428 


K,0 


2.92 


2.40 


300 


279 


H,0 


1.79 


084 


1.80 


100 


TO, 


0.70 


082 


058 


061 


P,Os 


0.37 


033 


0.30 


032 


MnO 


0.08 


008 


007 


004 


ZfO, 


000 


000 


000 


000 


CO, 


ooo 


006 


009 


001 


Total 


10000 


100 00 


10000 


10000 



ACE OF THE MURPHY SPRING TUFF BRECCIA 

Biotites separated from dacite samples from the plug at Look- 
out Peak give identical K-Ar age dates of 8.7 ± 0.2 m.y. 



Potato Peak Formation 

Several hundred feet of Potato Peak Formation, consisting of 
interlayered dacite flows and layers of tuff breccia of dacitic 
composition, are exposed in the northwestern comer of the Bo- 
die mining district (Plate 2). 

DACITE FLOWS 



NORMATIVE COMPOSITIONS 



Quartz 


14 744 


16883 


22175 


19370 


Corundum 


0791 


O390 


2732 


0411 


Orthoclase 


17 235 


14 192 


17 746 


16483 


Albile 


32 339 


33 024 


31340 


36248 


Wollaslonile 










Enslatile 


4509 


4985 


3^41 


2977 


Ferrosilile 










Magnetite 


3408 


0076 




2543 


Hemalile 


0968 


4451 


4^04 


1434 


llmenite 


1337 


15580911 


1.154 




Rulile 






O101 




Apatite 


0881 


782 


0711 


0755 


Calcite 




182 


0205 


0023 


Total 


98.230 


99177 


98214 


99021 


Salic 


87 126 


87 143 


88 841 


90135 


Femic 


11 104 


12 034 


9373 


8886 



Individual flows of dacite are not well defined in the district, 
but their aggregate thickness is estimated to be appro.ximately 
350 feet. The dacite lies unconformably upon tuff breccia. 

The dacite is medium- to coarse-grained, is medium gray col- 
ored, and shows well-developed flow banding. It is porphyritic 
and contains phentxrysis of andesine, black bioiiie, and dark 
greenish-brown hornblende enclosed in a fine-grained crystalline 
to semi-crystalline groundmass composed of andesine, biotite, 
hornblende, deep-green diopsidic augite, and devitrified glass. 
The feldspar phenocrysis are generally euhedral, show well-de- 
veloped twinning and oscillatory zoning, and are in the composi- 
tion range of intermediate to calcic andesine (An,,,,). The 
groundmass feldspar is in small lath-shaped crystals whose com- 
position ranges from sodic to intermediate andesine (An,,,,). 
Biotilc IS generally more common than the hornblende. It (Kcurs 
in dark brown to golden brown euhedral plates; the hornblende 
is in dark brownish-green euhedral grains Both, when altered, 
show black borders consisting of dust-like magnetite. 

Diopsidic-augite is not common, but usually occurs in deep- 
green, weakly ploKhroic euhedral grains in those dacite flows 
with hornblende content exceeding that of the biotUe Quarts •'< 
rare and generally (x:curs in anhedral grains. 

Pctrographic examinations of the lava flows in the Potato 
Peak Formation indicate that the flow rocks arc andesilic in 
composition Chemical analyses, on the other hand, indicate a 
dacitic composition (Table 3, Figure 5). 



(BH-14*) Biotite-homblende dacite from near the top of 
one of the latest lava flows in the Murphy Spnng Tuff Brec- 
cia, collected from the west edge of Sec. 24, T4N, R26E, 
MDM, about three-quarters mile westerly of Murphy 
Spring. 

(BH-18) Biotite-homblende dacite from a lava flow in the 
Murphy Spring Tuff Breccia, collected in the northeast 
comer of Sec. 21, T4N, R27E, MDM, about one and one- 
quarter miles northeasterly of Sugarloaf 
(854G-1) Biotite dacite from lava flow in Murphy Spring 
Tuff Breccia, collected in the central part of Sec. 28, T4N. 
R27E, MDM, about 300 feet southeast of Sugarloaf. 
(BH-20) Biotile-homblend dacite from a lava flow in an 
easternmost exposure of Murphy Spnng Tuff Breccia, col- 
lected at an abandoned railroad cut in the northca.st quarter 
of Sec. 23. T4N, R27E, MDM. 

For samples I, 2 and 4, mcthixls of analysis used arc de- 
scnbed in U.S. Geological Survey Bulletin 1 144-A. supple- 
mented by atomic absorption. Analysts: P. Elmore, S. Bolts. 
G Chloc, H Smith, J Kelscy, L. Artis and J Glenn For 
sample 3, method of analysis used is the single solution 
prcKcdure described in US Geological Survey Professional 
Paper 575-B, p 187-I<J1 Analysis: P Elmore. S. Bolts. L. 
Anis, J. Kelscy, H. Smith and J Glenn. 



* Indinln ftcld numtM-r 



1986 



GEOLOGY AND ORE DEPOSITS OF THE BODIE MINING DISTRICT 



11 




i 




..u 



\ 



Rhyolite / ' Rhyodacite ' Loi.te \ 



\ \ 




•-.■■..■:•. VA 



\ 



i 



LGtite 



Pototlium IQ 
FtldtpOf 




! 'Lafite - dndesite"^) 
\ Lotife - basalt -.vX'.! 

65 90 Plo9iocio»« 



^•Idipar 



Figure 4. Normative compositions of docite lavas from tfie Murphy Spring Tuff Breccio of tfie Bodie mining district and adjocent 
area plotted on a Streckeisen diagram. Numbers refer to onalyses in Table 2. Diagram adopted from Streckeisen 
(1967. p. IAD- 



TUFF BRECCIA 

TufT breccia of the Potato Peak Formation is a massive rock 
unit whose actual thickness in the Bodie mining district is not 
known, but whose exposed thickness is estimated to be about 1 50 
feet. ExfKJSures of the tuff breccia are scarce; but, where ob- 
served, it is medium gray in color and firmly indurated, and 
contains minor interbcds of luffaceous sandstone and conglom- 
erate The tuff breccia is po<irly bedded and consists of angular 
fragments and blocks of light gray biolite dacitc, as much as 6 
feet across, enclosed in a matrix of small rock fragments and 
volcanic ash The average size of blocks in the tu(T breccia is 
approximately one foot. 

The luffaceous sandstone and conglomerate layers are lens- 
like and generally range in thickness from 6 inches to 2 feet The 
tuffaceous sandstone is well bedded, medium to fine grained, 
light gray in color, and firmly indurated The tuffaceous con- 
glomerate, too, IS hght colored, and firmly indurated, and con- 
sists of subangular and well-rounded clasts that range in size 
from pea-size fragments to boulders ten inches acros<i. Volcanic 



ash makes up at least 40 percent of the matrix material, and the 
clasts consist largely of light gray biotitc dacite and minor 
brown-colored hornblende andesite. 

The tuff breccia unit rests unconformably uptm tuff breccia of 
the Silver Hill Volcanic Series and is unconformably overlain by 
dacite flows of the Potato Peak Formation. 

AGE OF THE POTATO PEAK FORMATION 

Based upon K-Ar age determinations of biotite from flows of 
dacite, the age of the Potato Peak Formation ranges between 9 I 

and 8.4 my. 

STRUCTURE 

Whiting (1888. p. 383) favored a siruclurat picture for the 
B<xlie mining district consisting of inter-laycrcd \a\a flows and 
tuff breccia layers dipping gently toward the south The irregular 
outcrop pattern of the hydrothennally altered rocks and their 



12 



CALIFORNIA DIVISION OF MINES AND GEOLOGY 



Bull. 206 



disturbed condition, due principally to faulting, may have con- 
tnbuted much to this thesis. F.H. Frederick (wntten communi- 
cation, l*)60) earned on a systematic geologic investigation of 
the district m the early l93C)s, and many of his thoughts and 
maps were the basis of some of the conclusions expressed by 
Wisser (I960, p. 70), who considered the structure to be an 
irregular northeastward-trending anticline, upon which are su- 
penmptised several domes. 

Table 3. Chemical analyses and normative composition. In 
percent, of the dacite flows of the Potato Peak Formation of 
the Potato Peak-Bodie Mountain area. 

CHEMICAL ANALYSES 





1 


2 


3 


4 


5 


SiO, 


61.70 


6181 


6147 


62 53 


6140 


AlA 


17.63 


16.93 


17 49 


17 74 


17 53 


Fe,Oj 


401 


3.81 


4.30 


3.31 


4.21 


FeO 


130 


1.20 


0.72 


150 


096 


MgO 


1.30 


240 


190 


130 


2.20 


CaO 


5.01 


4.81 


4.90 


431 


4.91 


Na,0 


391 


3.61 


4.00 


3.91 


391 


KjO 


2.50 


2.60 


2.60 


301 


230 


H,0 


1.50 


160 


1.50 


130 


083 


TO, 


0.73 


0.62 


064 


068 


088 


PA 


0.34 


0.40 


047 


034 


73 


MnO 


0.07 


0.21 


0.02 


008 


014 


ZrO, 


0.00 


0.00 


0.00 


000 


000 


CO, 


0.00 


0.00 


0.00 


000 


000 


Total 


100 00 


10000 


100.00 


100.00 


100 00 




NORMATIVE COMPOSITIONS 






Quartz 


17.684 


18107 


16 270 


18078 


18123 


Corundum 


0202 


0395 


0322 


1035 


1436 


Orihoclase 


14797 


15 390 


15356 


17763 


13613 


Albile 


33 054 


30514 


33 830 


33 067 


33 054 


Anorlhile 


22 620 


21236 


21228 


19149 


19571 


Wollasloniie 












Enslalile 


3.243 


5987 


4730 


3.244 


5488 


Ferrosilile 












Ivlagnelile 


2.306 


2761 


0531 


3131 


1002 


Hematite 


2.416 


1902 


3932 


1 147 


3516 


ilmenite 


1389 


1 180 


1215 


1294 


1674 


Rulile 












Apatite 


0807 


0949 


1 113 


0807 


1732 


Calciie 












Total 


98516 


98 421 


98 525 


98716 


99 208 


Salic 


88 356 


85 641 


87 005 


89 093 


85 797 


Femic 


10160 


12779 


11520 


9623 


13.411 



(48101*) Biotite-homglende dacite from a lava flow in the 
Potato Peak Formation, collected from a peak in the western 
part of Sec. 4, T4N, R26E, MDM, about two miles west of 
Potato Peak. 

(48102) Biotite-hornblende dacite from a lava flow in the 
Potato Peak Formation, collected from the southeast flank 
of Potato Peak in the eastern part of Sec. 3, T4N, R26E, 
MDM 

(48103) Biotite-hornblende dacite from a lava flow in ihc 
Potato Peak Formation, collected from the southeast corner 
of Sec. 3, T4N, R26E, MDM 

(BH-13) Biotite-hornblende dacite from a lava flow in the 
Potato Peak Formation, collected from a small hill in Sec. 
23, T4N, R26E, MDM, about three-quarters mile northwest 
of Murphy Spring. 

(BM-2) Biotilc dacite flow of the Potato Peak Formation, 
collected from the center of Sec 12, T4N. R26E, MDM, 
about two and one-half miles northwest of Bodie townsitc. 
For analyses I, 2, 3 and 5. methixl of analysis used is Ihc 
single solution procedure described in U.S. Geological Sur- 
vey Professional Paper 575-B. p. 187-191 (1967). Analysts; 



P Elmore, S. Bolts, L. Artis, J. Kelsey, H. Smith and J. 
Glenn. For sample 4, methods of analysis used are described 
in U.S. Geological Survey Bulletin 1 144-A, supplemented by 
atomic absorption. Analysis: P. Elmore, S. Bolts, G. Chloe, 
H. Smith, J. Kelsey, L. Artis and J. Glenn. 

* Field numbrr) Uktmh on plalc 2. 



Faults 

The main faults, the Moyle Footwall fault and the Standard 
Vein fault, are parallel in general to the axial plane of the anticli- 
nal upfold (Plate 2) mentioned by Wisser. Both faults are nor- 
mal with very little stnke-slip movement. The Moyle Footwall 
fault has a fairly constant stnke of N 38° E and dips eastward 
from 60 to 70 degrees. It can be traced intermittently along its 
strike for a distance of about 4,000 feet It was encountered 
underground in the Bodie and Standard mines and supposedly 
in the Syndicate mine at the north, but no evidence could be 
found to indicate whether it was cut by the later Mono fault 
(Plate 2). Where seen in the Roseklipcut, underground near the 
Standard New shaft, the Moyle Footwall fault has a well-defined 
breccia zone about 2 feet wide that contains quartz fragments. 
It appears from the character of the gouge and the off-setting of 
veins formed later that activity on the Moyle Footwall fault 
extended from pre-mineral into post-mineral time. 

The Standard Vein fault, so called because it contains the 
Main Standard vein, has about the same magnitude a.s the Moyle 
Footwall fault. It slnkes N 18-20° E, has a 60 to 70 degree 
westerly dip, and can be traced intermittently along its strike for 
a distance of about 3,500 feet. The fault was encountered in the 
Standard and Syndicate mines and in small intervening mine 
workings, but apparently not in the workings from the Lent 
shaft. It is pre-mineral in age, but with sustained post-mineral 
movement which produced a saccharoidal or granular condition 
in large sections of the Main Standard vein. 

As the direct result of extensive sloping in the Standard mine, 
a relatively large block of rock pnncipally altered tuff breccia of 
the Silver Hill Volcanic Series, dropped. At the surface, this 
produced an eastward-facing escarpment 3 to 5 feet high and 800 
feet long at the Moyle Footwall fault and a westward-facing 
escarpment from one to 4 feet high and 150 feet in length along 
a segment of the Standard Vein fault. 

A third major fault, which also is roughly parallel to the axial 
plane of the anticlinal upfold (Plate 2), is in the valley occupied 
by the Bodie townsite, where it is overlain by alluvium. The 
position of the northern trace of the fault is indicated by several 
springs. The fault slnkes N 18° E for much of its studied length, 
but strikes N 30° E at its northern end. It is a stcx-p. normal fault 
whose dip could not be measured, and it appears to have down- 
dropped the block on the east by at least several hundred feet. 

There are several cross faults in the district; the Tioga, the 
Mono, and the Jupiter. The Tioga and Mono help define what 
has been referred to as the Bonanza zone Brown ( 1907. p. 356) 
ptiinted out that the riKks underground between thc-se faults are 
highly altered but contain no ore. 

The Tioga fault, which forms the northern boundary of the 
Bonanza zone, strikes N 62° E. It crosses the canyon west of 
Bodic Bluff and follows Milk Ranch Canyon in a westerly direc- 
tion (Plate 2) The fault is clearly marked on the surface by 
depressions and gulches, c-spccially on the west slope of Bodie 
Bluff. It is a normal fault in which the bUxk on the south has 
dropped, probably in a near-vertical direction, by perhaps as 
much as 5(X) feet. It is a pre-mincral fault, as veins pa.v. through 
altered, brecciated rock in its fault zone and reappear on the 



1986 



GEOLOGY AND ORE DEPOSITS OF THE BODIE MINING DISTRICT 

iQtz 



13 




• * 90 Plogioclot* 

Ftldipor 

Figure 5. Normative compositions of docite lovos of the Pototo Peak Formation of tfie Bodie Mountain-Potato Peak area plotted on 
a Streckeisen diagram. Numbers refer to onolyses given in Table 3. Diagram adopted from Streckei%er} (1967, p. 1611. 



Other side. Post-mineral movement along the Tioga fault was 
relatively small, probably no more than several tens of feet at the 
most. 

The Mono fault forms the southern boundary of the Bonanza 
zone. This fault strikes N 66° W and, like the Tioga fault, is 
marked at the surface by topographic expression as well as by 
displacement of rock units. It, too. is a normal fault with a 
horizontal right lateral displacement of about 500 feet; the extent 
of vertical displacement, down on the south, is not known. The 
Mono fault zone, about 100 feet wide, is visible on the surface 
and in mine workings. The water storage tank for the Bodie State 
Historic Park is situated in the Mono fault zone, and during the 
excavation for the tank's foundation, relatively pure montmoril- 
lonitc and altered dacite were encountered. 

Major movement on the Mono fault was pre-mineral, as no 
quartz veins were offset in the fault zone The Fortuna vein 
fracture was traced into the Mono fault zone and its presence 
was indicated by vein material consisting essentially of coarsely 
crystalline gypsum 

Faulting in the Middle mines and Southern mines areas of the 
district has done much toward dislcxaling various units of the 
Silver Hill Volcanic Scries and opening them to mineraliz.ation 
and alteration. The principal fault in the Southern mines area 
extends in a northwesterly direction through the Queen Bee 
shaft, across the northern flank of Queen Bee Mill, and through 



the University and Spaulding shafts (Plate 2) Beyond the latter 
shaft, it dies out at or along the contact between tulT breccia and 
dacite lava flows of the Silver Hill Volcanic Series. This is a 
normal fault which dips eastward 60° in the Boiiker workings, 
and whose principal movement was pre-mineral. The amount of 
downward movement is not known, but an andcsile dike on 
Queen Bee Hill was cut and its segments were displaced by as 
much as 200 feet by sirikc-slip movemenl Quart/ veins along the 
fault have been crushed as the result of post-mineral movement, 
which apparently was not great. 

A fault whose strike rangi-s from N 75° W to S 60' W trends 
across the district just north of Sugarloaf( Plate 2) It is a normal 
fault whose upward movement on the south side brings the lower 
hornblende-rich dacite unit of the composite flow into contact 
with the upper biolile-rich unit of the flow. This fault is cut off 
on the east by what appears to be one of the youngest faults in 
the district, which trends approximately north, dips steeply to- 
ward the west, and forms for some distance the contact between 
units of the Murphy Spring Tuff Breccia and rocks of the Silver 
Hill Volcanic Scries. 

Numerous small faults occur in the district Although Mime 
of them can be found at the surface, others are identified only 
in mine workings where they have displaced veins or are fracture 
zones along which veins were der>osiled and were avenues for the 
migration of hydrolhcrnial fluids A polar plot (Figure 6) of the 



14 



CALIFORNIA DIVISION OF MINES AND GEOLOGY 



Bull. 206 




Photo 5. View to southwest of the Bodie mining district, showing the Syndicate mine (Sd), Whitney tunnel (W), Davis tunnel (D), Tiogo tunnel 
(Tt), Bodie Bluff (BB), Standard Hill (St.H), Tailings pond (Tp) ond Sugorloof (S), Sierro Nevada on skyline. Photograph by Bennie 
W. Troxel. 



principal faults encountered underground in the Red Cloud 
mine indicates that the faults here essentially trend north and are 
parallel in large measure to the trend of the shear zones and vein 
system. 

Jointing and Sheeting 

Studies of the outcrops of the intrusive dacite and flows in the 
Bodie mining district failed to reveal any joint patterns or sys- 
tems that might help to decipher the structural history of the 
rocks. In the mines, especially those in the Standard Hill area, 
early investigators found closely spaced parallel fractures called 
"sheeting" in the wall rocks, generally parallel to the so-called 
fissures which contained the quartz veins in the Standard and 
Bodie mines. Whiting (1888, p. 387) states: "Even in the minut- 
er structure of the rock this effect of compression is no less 
stnkingly evidenced by a schistose foliation along now one, now 
the other, wall of a fissure; and, as a peculiar feature of these ore 
bodies such foliated portions have invariably been found to be 
very rich in gold and silver; as though this structure, originally 
due to compression, had affected in the innumerable, though 
minute, fault fissures thus formed, such retardation to the flow 
of the mineral bearing solutions and such virtual increase of 
deposition surface as to have caused a more abundant minerali- 
zation of the veins at such l<x;alities." 

The development of sheeting and tension fissures in the intru- 
sive dacitc of the B<xlic Bluff-Standard Hill plug has been at- 
tributed to up-arching of the rocks to form the Ikxiie aniiclinc 



(Wisser, 1960, p. 73). Certain sheeting planes became the Moyle 
Footwall and the Standard Vein faults, which produced the 
graben in the Standard Hill mines area. The fan pattern of longi- 
tudinal sheeting, which is said to show up so well in cross section 
in the vicinity of the Syndicate mine (Whiting, 1888, p. 387), is 
related to the same dynamics that produced the longitudinal 
sheeting in the Bodie and Standard mines. This same fan pattern 
is said to occur in the mines near Silver Hill and Red Cloud mine, 
where the tension fractures and sheeting are in lava flows of the 
Silver Hill Volcanic Senes and are related directly to the forma- 
tion of the anticlinal upfold. 

Farther south at Queen Bee Hill and at Sugarloaf, evidence of 
sheeting is scarce, although the flows and intmsive bodies are 
highly jointed. 

Plugs 

The largest plug in the district underlies Bodic Bluff and 
Standard Hill. In plan, it is elongate in an easterly direction, with 
its greatest development at Btxlic Bluffand Standard Hill, where 
it is approximately 3,500 feet across. At the surface, the plug is 
divided into two sections by a narrow septum of brcccialcd. 
propylili/cd luff breccia of the Silver Hill Volcanic Scries, the 
eastern mass is p<itassically altered dacite. but the main btxiy of 
the plug has undergone strong propylilic alteration and mild 
p<ilassic alteration. 

Internal structures in the plug are not abundantly evident, but 
flow-banding, where observed, is generally sleep. Contacts 



1986 



GEOLOGY AND ORE DEPOSITS OF THE BODIE MINING DISTRICT 



15 



N 



East 
Dipping 



/ ° 


^^ 


/ o 
/ ° 


\ 


/ 


* ctoO o\ 


o 


o o 


\ o 


(P o 


\ ° 


I 


\ ° 


^ 



West 
Dipping 



Figure 6. Polar plot of faults in the Red Cloud mine. Plotted on upper hemisphere. 



between the plug and the wall rock are steep and generally 
accompanied by intense argiliization of both the plug r<Kk and 
the wall rock and by local shearing in the walls of the plug. 

Based upon exposures of the plug in the field and the sequence 
in which the several types of hydrothermal alteration occurred, 
it is reasonable to assume that the plug was emplaced m two 
separate yet overlappmg pulses of volcanic activity. The main 
body of the plug at Bodie Bluff was formed first, as the dacite 
of which It IS composed was subjected to early propylitic altera- 
tion, and later the plug dacite east of the septum in the plug was 
emplaced at a time when p<ilassic alteration was taking place. 

The plug at Queen Bee Hill, which was emplaced at about the 
same time as was the Bodie Bluff-Standard Hill plug, is small 
and elongated in a northwesterly direction, and has a maximum 
dimension of about 1,000 feet. Flow-banding is vertical or dips 
steeply, generally inward toward the central part of the plug. 
Lack of accevs to mine workings al Oucen Bee Hill made it 
impossible to observe the contact between the plug dacite and the 
wall rock, but the nature of the flow-banding in the plug indi- 
cates that the contact is steep. The dacile of the plug has under- 
gone argillic alteration, which extends outward from the plug 
into the wall rock for only a few lens of feet Ihc wall rock 
consists principally of units of the composite flow thai have 
undergone propylitic alteration. 



The plugs at Sugarloaf and near the Red Cloud mine were 
emplaced between 8.3 and 8.9 my. ago, and are later than the 
other plugs in the district (Silbcrman and others, 1972, p 601 ) 
The plug al Sugarloaf forms a symmetrical cone when viewed 
from ground level and has an ellipsoidal shape whose north- 
trending axis measures approximately 1,300 feet. Flow-banding 
and ihe principal joint pattern in the plug dip very steeply to 
vertically. The Gorman tunnel (Plate 2), on the west side of 
Sugarloaf, passes first through the lower hornblendc-rich dacite 
unit of the composite flow, then penetrates the intrusive dacite 
of the plug at a point about 100 feet from the portal, which is 
now caved (Frederick, I960, written communication) The con- 
tact between the plug and the wall rock is sleep and marked by 
a zone about 4 feet wide, of clay and sheared rock. Inward from 
the contact, a zoneof propylili/ed inlrusive dacite ab<iul 1 50 feel 
wide is uniformly developed around the circumference of the 
plug. The interior of Ihe plug is relatively unaltered hornblende 
dacite. 

The smallest plug in the distnct lies a few hundred feel south 
of the Red Cloud mine It is roughly circular in plan and has a 
diameter of approximately 5f)0 feel I'niikc Ihc olhcr inlrusive 
bodies, this plug has no dislinclivc topographic expression The 
contact between the plug and the wall riKk is concealed by soil 
Flow-banding is scarce, but where found it is steeply inclined 



16 



CALIFORNIA DIVISION OF MINES AND GEOLOGY 



Bull. 206 




Photo 6. View to northwest of the central and northern sections of the Bodie mining district, showing Red Cloud mine (RC), Silver Hill (SH), 
Standard Hill |St.H| and Bodie Bluff (BB|. 



inward. The plug is composed of hornblende-biotite dacite, 
which is relatively unaltered at the interior but argillically al- 
tered near the margins. The biotite-rich dacite unit of the com- 
posite flow, which forms the wall rock of the plug at the surface, 
also has been argillically altered. 

Silver Hill is considered by Wisser ( 1960, p. 70) to be under- 
1am by an anticline at whose core is a dome, but no evidence 
could be found to support this hypothesis. Instead, the topo- 
graphic high at Silver Hill is capped by a mass of intensely 
silicified tuff breccia of the Silver Hill Volcanic Series that lies 
upon the biotite-rich dacite unit of the composite flow. 



GEOLOGIC HISTORY 



Structure Interpretation 

The interpretation of the structure of the Hodie mining district 
by the present writers is based on detailed geological mapping of 
the district and of the area immediately surrounding it. a great 
deal of which lies in the Hodie quadrangle (Chestcrman and 
Gray, \^15) 

The writers concur in general with the anticlinal suggestion of 
Wisser, but the structure of the district is complex and can be 
perhaps best understood through a discussion of its history. 



Tertiary Rocks 



The extrusive rocks of the Silver Hill Volcanic Series are 
considered to be the oldest exposed volcanic rocks in the Bodie 
mining district. The distribution of thepyroclastic deposits of the 
Silver Hill Volcanic Series indicates that the pnncipal eruptive 
vents for the materials were what are known as Bodie Bluff, 
Queen Bee Hill, and Sugarloaf (Plate 2). The pyroclasiic depos- 
its in the \icinity of Bodie Bluff are thickest north of the peak 
of Bodic BlutT Because of the lack of adequate exposures, the 
thickness of the series in the district can only be estimated at 
between 800 and 1,000 feet. That there were several explosive 
periods in the volcanoes of the district is indicated by the occur- 
rence of several thin tuffbreccia layers among dacite flows in the 
vicinity of Silver Hill 

The deposition of the main (lowermost) layer of tuffbreccia 
was followed by flows of dacite, the first of which, from the vent 
near Silver Hill, was interrupted by brief pcncxls of explosive 
activity The emplacement of the comp<isile flow at B«xlic Bluff 
some 'i A to S.8 my. ago was near the closing phase of \olcanic 
activity in the district The emplacement of the plugs at Bodie 
Bluff, near the Red Cloud mine, at Queen Bee Hill, and at 
Sugarloaf represents the intrusion of dacite into the several vents 
following the last outptmnng of lavas as flows. It seems most 
likely that these plugs were connected with the same magma 
chamber; the activity at each vent, however, was not neces.sanly 
contemporaneous with that of the others, although their overall 



1986 



GEOLOGY AND ORE DEPOSITS OF THE BODIE MINING DISTRICT 



17 



range in age from 8.3 ± .4 m.y. to 9.2 ± 0.5 m.y. indicates a 
relatively brief time interval within vshich these plugs could have 
been emplaced. The chemical analyses and pctrographic studies 
indicate that no appreciable difTerentiation has taken place with- 
in the magma chamber. 

The emplacement of the plugs was accompanied by a general 
anticlinal upfolding of the earlier dep<isited interlayered lava 
flows and pyroclastic layers. Bedding in the tuff breccia and flow 
banding in the lava flows in the immediate vicinity of the plugs 
is steeply dipping, especially around the plug at Btxlie Bluff and 
Standard Hill, where contacts were observed in the mines The 
evidence suppcirts the assumption that the plugs are apophyses 
of a larger intrusive body of volcanic rock, probably dacitc. at 
depth, and that the shape of this body is elongated in a generally 
north-south dirtx-tion. Both magnetic and gravity data support 
this concept The axis of the anticlinal upfold is parallel to the 
general alignment of the plugs. The major fractures, faults (other 
than the cross faults), and veins arc parallel to the axis of this 
upfold and dip generally toward its axial plane. 

The fracture systems which opened the rocks to alteration and 
mineralization were developed in the intrusive btxlies following 
their emplacement and the formation of the anticlinal upfold 

The Fortuna vein fracture is perhaps the oldest in the district. 
It strikes approximately N 10° E. In the upper levels of the Bodie 
and Standard mines, the fracture dips 30° toward the east and, 
in the lower levels of these mines, steepens to as much as 45° E. 
Where it steepens, the fracture contains very little vein material 
and appears pnncipally as a zone of thinly sheeted and highly 
altered dacite and gouge showing slickensides and striations 
(Whiting, 1888, p. 392). 

The Fortuna fracture (Figures 7, 8, 9. and 10) is cut by later 
veins and fractures, and its origin may be related more to the 
emplacement of the plug at Bodie Bluff than to the general 
anticlinal upfolding in the dislnct. Wisser ( I960, p. 73) related 
the Fortuna fracture to a period of uplift which was supposed to 
have occurred east of the Bodie anticline and developed before 
the extrusion of lava from the vents at Bodie Mountain. 

Lava flows of the Potato Peak Formation overlap the pyro- 
clastic deposits and flows of the Silver Hill Volcanic Series at the 
northern and northwestern parts of the Bodie mining district, 
but nowhere could any evidence be found to support Wisser"s 
thesis that units of the Potato Peak Formation covered the entire 
area now encompassing the Bodie anticline. Tension fractures 
would have been developed in the flows and pyroclastic layers 
in the development of the anticlinal upfold, but what dynamics 
are required to produce linear fractures and sheeting in the 
intrusive dacite plugs themselves, which should have been 
marked by radial and concentric fracture systems? 

Although the K-Ar age data indicate a continuous process of 
emplacement of the intrusive bodies in the district, specific age 
dating indicates that the plugs at Bodie Bluff-Standard Hill and 
Queen Bee Hill were emplaced ab<iut 9.2 i 0.5 my. ago (Silber- 
man and others, 1972, p. 602) — older than those at Sugarloaf 
Peak and near the Red Cloud mine, which were emplaced at 8.3 
and 8.9 my. ago, respectively. 

Partial withdrawal of the magma from the plug at Bodie Bluff 
to form the plugs at Sugarloaf and near the Red Cloud mine 
resulted in the development of the faults and graben stnicture in 
the Bodie Bluff-Standard Hill area. 

Mineralization in the Bodie mining district seems to have 
commenced shortly after the emplacement of the plugs K-Ar 
age determinations made on adularia obtained from a vein in the 
Moyle Footwall fault zone gave an age of 7 t 2 my to 7.0 
± 0.1 my. Adulana from the waste dump of the McClinlon 
shafi, either from the Burgess or Incline vein series, gave an age 
of 8.0 ± 0.2 my. (Silbcrman and Chcstcrman, 1972. p 17). 



w*- 


Incline Series 


— E 


1 v™^ 






^ 1 






• 1 


1 FhT^-'^^II^ 


low>i«. 


-n k 


s 11 It " r 




o \ 




a 11 I o 






o 1 




1 II II — 


:d 




it 




U II 11 • 

// // // ' 


• 




o^ 




1 1 // / "" 


r-" 




•^ 




II 1 II 1 — 


• 
a. 




\k 




/// '' 


\ 








//I 


\ 


s 


s 








// 




^Lo^ 


























1 ^ 


/ 


r^ 


Burgais \ 


/ /I 




"\ 


Senas ( 


i 




• 



Figure 7. Crojs section of the »ein tyslem of the Standard mine. Modified 
from Brown, 1907 



Adularia from the vein specimen, of coarse-grained calcite and 
intergrown fine-grained quartz and adularia from the Red Cloud 
mine, gave an age of 7.7 ± 0.1 m.y. (Silberman and Chesterman, 
1972, p. 17). 

ALTERED AND MINERALIZED ROCKS 

Hydrothermal alteration (Plate 2) has been widespread in the 
Bodie mining district. The type of hydrothermal alteration has 
determined to a considerable degree the color of the altered rock. 
Propylitic alteration has given a greenish color to lava flows and 
tuff breccia: argillic and silicic alteration generally results in 
white and pale gray rocks, with fracture surfaces thinly coated 
by reddish, reddish-brown, and yellow hydrous iron oxide stains. 
Rocks that have been alTected principally by potas,sic alteration 
do not appear to have suffered significant color changes; where 
these rocks have not been affected by additional argillic altera- 
tion, they are dense and firm and have the general appearance 
of unaltered rock. 

Hydrothermal alteration in the district commenced during or 
soon after the closing stages of volcanism (Silberman and others, 
1972. p. 602). Detailed field mapping in the district indicates 
that there were four stages of hydrothermal activity, commenc- 
ing with propylitic and followed in succession by argillic. pcitas- 
sic, and silicic. 

The propylitic alteration was widespread and seems to have 
afTected all rock types regardless of composition and structure. 
The resulting mineral a,sscmblage includes chlontc. scricitc, epi- 
dotc. quartz, pyrile. and hematite, in addition to the feldspar and 
other minerals characteristic of the original rock (Photos 7 and 
8). 

Argillic alteration resulted in formation of rocks characten/ed 
by quartz, chalcedonic and opaline silica, montmonllonilc. kao- 
lin, limited sencite, carbonate, and pyritc (see Photo 14) The 
altered rock is usually soft and friable, and forms smimth slopes 
The pyritc is irregularly distributed in the argillically altered 
rocks and appears to be more concentrated along joints and 
fractures and occasionally sparsely disscininatcd throughout lo- 



18 



CALIFORNIA DIVISION OF MINES AND GEOLOGY 



Bull 206 



Bodle New Shaft 














1 


Ml" 






III 














III 














III 














III 














III 














III 














III 














III 














III 














-^ III 














^ 














g U 














«, t»z-- 


;iU206' Lev 












Burges 












LEGEND 












^^5?l - 


r.-^^ptii 












yfifi^ Fortuno Slopes 


i:XI308' Lev. 


^ 

a 
















;,'i«; 


Faulting Veint 




1 

■to 










-■I'-f. 


Wall Rock 




















~iir"" 

432' nCi 
III * 


^^i 


1 460' Le/'v 








1 

■1 




k k 


462 


" Lev^ll^^^'. 


-;•.. 




S 




«> 2 






^ 




t) 




(5 ^3 




536' Lev,- 


AT^ 


^^■:.."t 


* v-^ 










554' 


Lev^ 














641' Levl;^;'' 1 '^^^j;i!:3;.r. 





50 


SCALE 










M"^^^^ 


100 




200 ft 




























^Op "•'-<"•'' ^..;---5%A'^- 












Lent 


Shaft 707' Lev.'@i"£ 


~Z~ZZ ZI.ZZt^S'3i'Wrnze No 3 


^» ^^ ^— ^H ^H ^B ^m 4_ ^B ^^ ^M ^"^BK- Jj »**. 4^ 1 






































































■\V^cS«r!P.^ 




























~-7Sf<' 



Figure 8. Vertical section through Fortuna slopes, 

cal areas. Oxidation of the pyrite has given outcrops of the rock 
a blotchy brown and reddish-brown color. 

Potassic alteration appears to be confined to the rocks in and 
surrounding the Bodie BlufT-Slandard Hill plug, where it is obvi- 
ously later than the propyliiic alteration. The relationship of 
potassic to argillic alteration is not well known, but exposures in 
the Bulwer tunnel suggest that the potassic alteration is later. 
Dacite thai has undergone potassic alteration is firm, appears 
unaltered in hand specimens, and forms bold outcrops, especially 
on and near crests of ridges and hilK. It is porphyrilic; a micro- 
scopic examination revealed small rectangular microphenocrysts 
of sanidinc and fine-grained adularia in the groundmass. 

Analyses 1, 2, 3, and 4 (Table I) on rocks from the Bodie 
Bluff-Standard Hill plug show abnormally high K.O content in 
comparison to the analyses (nos. 5, 7, 9, 10, and II) of dacite 
from the plugs al Queen Bee Hill and Sugarloaf 

Pota.ssic alteration undoubtedly (Xcurred over a considerable 
span of lime, even into the formation of quart/ veins in rixks 
which had potassic alteration superimposed upon earlier propy- 
liiic and argillic alteration processes. Adularia is a common 
constituent in some of the quart/, veins, especially those of the 



Bodie mine. Modified from Whifing, 1888. 

Burgess series, which are clearly later than those of the early 
Fortuna series, and which have been dated as being between 7.1 
and 8.0 my. old. 

Silicic alteration, the last stage of hydroihermal activity and 
perhaps a factor in the formation of the quartz veins, is evident 
on the surface at several areas but is kvalized in the central part 
of the district on Silver Hill (Plate 2), in an area surrounding 
the Noonday mine and near the portal of the Aurora tunnel Two 
rock types arc involved in silicic alteration, the biotite-nch dacite 
unit of the composite flow and a tuff breccia layer that lies ab*ive 
the composite flow. 

The silicically altered rock is pale gray to white in color and 
dense, and appears to consist largely of quart/ and chalcedonic 
silica. A sample of silicified tuff breccia, which forms the cap on 
Silver Hill, contains 91 14 percent SiO... 0.11 percent CaO. 006 
percent Na..O. and 0.72 [XTcenl K.O; the remainder consists pnn- 
Lipally of iron and sulfur and minor amounts of aluminum (Maj- 
inundar, written communication. 197.1) Where the alteration 
has affected the dacilc la\a flows, icxiurc-s and structures of the 
original rcxk are Msible but not common However, the original 
clastic structure is plainly visible in silicified tuff breccia. A 



1986 



GEOLOGY AND ORE DEPOSITS OF THE BODIE MINING DISTRICT 



19 



structural control for selective siliciflcation can be deduced from 
the fact that the pyrivlastic materials, because of their lower 
bulk density and high porosity, are more readily and completely 
silicified and pervasively mineralized than are the denser flow 
rocks. 



M 


Sillclfi«d (Andesl»«) doelfe «'tm^(P 


ill 


(Andesite) Oacitt ^ S^ ^ f' Ui 






+ttJ 


m\ 


-r (^ 


c — c 


Crossing illl ''^'- t^vfflt' 




w 



Figure 9. Foce in stope on th« Fortune vein, Bodie mine. Modified from 
Brown, 1907. 















'/ 








' I '' 


/ -'' !^^^i * 






v/ • 


li^r' 






>7 y 


J 




\^^ 


^\^ 






V-"'^'* 








Wi' 






4M tl li.al 


W^/ 


\ ^^m 






EAST , 


:0% • 




lEST 



Figure 10 Eail well icdion through the Fortuno ilope m the north drift No. 1 
of the 432 foot level of the Bodie mine, showing the cross-cutting 
oge relationships of the Fortuno ond Gildeo veins. Modified 

from Whitifig, J838 



GEOPHYSICAL INVESTIGATIONS 



Regional Gravity and Magnetic Data 

The results of regional aeromagnctic and gravity studies in the 
Bodie Hills area of California and Nevada by the L' S Geological 
Survey and the California Division of Mlnc^ and (icology have 



been discussed by Kleinhampl and others (1975). The aeromag- 
nctic and gravity data presented by Kleinhampl and others 
(Plate 1 and Figure 4) include anomalies thai have a significant 
bearing on the interpretation of the geology of the Bodie mining 
district. The features of greatest importance shown by these may 
be two nearly coincident, north-trending anomalies: a negative 
aeromagnctic anomaly and a positive gravity anomaly, both of 
which are centered near the mining district. Plate 1 shows a 
comparison of the regional aeromagnctic and gravity data along 
Profile RS across the Bodie mining district near Queen Bee 
Hill (location shown on Plate 2) This profile illustrates the 
close association of the aeromagnctic and gravity anomalies 
here and suggests the possibility thai bi>ih anomalies may reflect 
the same source or closely related sources. 

The local gravity anomaly is a part of a more extensive positive 
anomaly trend that extends through the Bodie Hills area This 
major feature trends northeastward from near Lundy Canyon, 
north of Mono Lake, to Cottonwcxxl Canyon, where it turns 
almost directly north and passes through the Bodie mining dis- 
trict (Kleinhampl and others, 1975, Figure 4; Plate 1 of this 
report). Near Bixlie the anomaly turns northeastward again and 
continues to the vicinity of Aurora Peak in Nevada. The anom- 
aly is essentially continuous except for a possible interruption 
near the change in trend east of Cottonwood Canyon. 

Pre-Tertiary ba.semeni rocks are closely associated with the 
gravity anomaly in the northeastern and southwestern parts of 
the Bodie Hills, but in the intervening area, which includes the 
Bodie mining district, only younger extrusive and intrusive rocks 
are exposed. Thus, a possible explanation for ihis anomaly may 
be relief on the basement rock surface. An alternative explana- 
tion for the gravity high, which would be reasonable at least in 
the Btxlie mining district, is suggested by the series of dacite 
plugs that have been mapped in ihe area (Plate 1). These plugs 
are believed to be apophyses of a larger intrusive mass at depth 
(this report, page 17). Either of these possible explanations, 
basement relief or intrusive rixrks, assumes a higher average 
density for the anomaly source than for the surrounding rocks. 

The cause of the local aeromagnctic anomaly in the vicinity 
of the Bodie mining district might be either the extensive hydro- 
thermal alteration, which has resulted in destruction of magnet- 
ite in some of the extrusive and intrusive rocks underlying the 
district (this report, page 17), or simply a contrast in magnetic 
properties between two or more rock types. The results of meas- 
urements of the magnetic susceptibility of a number of samples 
(Table 4) suggests that the average value (0.0012 emu/cm) for 
extrusive daciie from the Bodie mining district is only slightly 
less that that (0.(X)14-0(X)17 emu/cm) for similar rtx-ks (dacite 
and andesite) from the surrounding areas in the Bodie Hills. 
Nevertheless, it is possible thai Ihe sampling did not give proper 
weight to the relatively altered extrusive riKks in the mining 
district. 

The average value (0(XX)« emu/cm'; Table 4) of magnetic 
susceptibility obtained for intrusive dacilc from the Bodic min- 
ing district is distinctly lower than ihal (0.0012-0.0017 emu/ 
cm') for the extrusive rocks given above. Although this apparent 
difference may be large enough to cause the observed anomaly — 
considering ihe p<issible si/e of Ihe intrusive mass at depth — ii 
is not known whether these results are truly representative of the 
mass of the rock The relatively low magnetic susceplibililies of 
the intrusive rocks sampled may. however, be Ihe result of the 
intense hydrolhermal alteration which characlcri/es these rtKks 
in surface exposures throughout most of ihe B<xlic mining dis- 
incl. 

The loss of magnetite during alteration of the nvks in ihc 
mining district also would reduce the effect on the magnetic field 
caused by remanent magnetism. This, or the presence of reverse- 



20 



CALIFORNIA DIVISION OF MINES AND GEOLOGY 



Bull 206 




Photo 7. Veined ond propyiiticaiiy oitered tuff breccia of the Silver Hill Volcanic Series, as exposed underground in the Bulwer tunnel, 
about 150 feet west of the contact with the intrusive dacite. Scale is 6 inches long ond rests against o pyroclost of orgillicotly 
altered dacite. 



ly magnetized rocks, might also help account for the negative 
aeromagnetic anomaly, but no measurements of the intensity of 
remanent magnetism of samples were made during this study. 
The direction of remanent magnetism was determined in the 
field for a number of intrusive and extrusive rock samples from 
the Bodie Hills (see Chesterman and Gray, 1975). In the Bodie 
mming district, these measurements showed normal and re- 
versed directions of remanent magnetism for appro,\imaIely 
equal numbers of both intrusive and extrusive rocks. Thus, it was 
not determined whether the direction of remanent magnetism 
contributes significantly to the observed anomalies in the Bodie 
area. A more detailed and extensive study would be required to 
resolve this question. 



Detailed Gravity and Magnetic Data 

While the regional geophysical work for this report was in 
progress, relatively detailed gravity and ground niagnelic sur- 
veys were also undertaken in the Uodic mining district Approxi- 
mately 180 gravity and magnetic stations were (Kcupied at 
points of known IcKution aiid elevation in the district. A Worden 
gravity meter and a Jalander fluxgate magnetometer were used. 
These p<>inls include a few bench marks established by the U.S. 
Coast and Geodetic Survey and the LIS. Geological Survey and 



spot elevations from U.S. Geological Survey topographic maps, 
but most are spot elevations that had been established by survey- 
ing in the district. In addition to these stations, a few lines of 
closely spaced magnetic values were added in parts of the area. 



Table 4. Magnetic susceptibility measurements of rocks of 
the Bodie mining district and surrounding oreo. 



(i>c> rn» 




No ol 




lim, am'l 


Intrusive rock* of »*• 
BodaHM VM 














dKlM 

niy<*w 








0001 • 0Q?O 




0011 
OO0& 


Inwutnw tockM ol Om 












DKM 




16 




000O4 OKI 




aoH 


ExtrutfV* rodisolVi* 
BodNHMHM 














•ndmlt 

(Mew 

bftuN 

mKMOIuII 




4 

s 

1 
1 




0O06 . OQ?S 
0006 - 0Q?1 




0017 
OOK 
0Q?1 

001 r 


EalruWv* rodi* ol tf« 


or*, 












IMCM 

MltncoK 




• 
1 




000O1 ooos 




0017 



1986 



GEOLOGY AND ORE DEPOSITS OF THE BODIE MINING DISTRICT 



21 




Photo 8. Ffoctured ond propyiiticolly altered intrusive dacite of the Stiver Hill Volcanic Series, os exposed underground in the Bulwer tunnel, about 
50 feet from the contact between the intrusive dacite ond tuff breccio. Scale is 6 inches long and lies across a quortz vein that dips 
steeply to the right. 



Values of observed gravity were tied to a local station in Bodie 
which was referenced to a California Division of Mines and 
Geology base station in Bridgeport (Chapman, 1966, p. 46). 
Terrain corrections were calculated for all stations; these include 
inner zone corrections out to 2.29 km, estimated from topo- 
graphic maps by using Hayford zones A-F and subzones (Oliver 
and others, 1969, p. 20-21). The remaining terrain corrections, 
out to a distance of 166.7 km, were obtained by the use of a U.S. 
Geological Survey computer program (Plouff, 1966). The ter- 
rain corrections calculated for stations in the Bodie mining dis- 
trict range from about 3 mgal in the flat area south of the 
townsite of Bodie to more than 9 mgal for a station on top of 
Bodie Bluff. Gravity values were reduced to complete Bouguer 
anomalies for densities of 2.67 g/cm' and 2.50 g/cm' usinga U.S. 
Geological Survey reduction program. 

Values of the vertical intensity of the magnetic field were 
determined at each of the gravity stations and on a few separate 
profiles, as mentioned above. These values are on an arbitrary 
datum but were tied to a base in the Bodie townsite. Repeated 
readings at this base were used to remove drift and diurnal 
effects. 

RESULTS OF THE GRAVITY SURVEY 

The Bodie Hills, including the Bodic mining distnct, arc locat- 
ed near the axis of a large regional gravity minimum (Woollard 
and Jocsting, 1964). Although the Bodie mining district is on the 
eastern side of this minimum, there is apparently only a relative- 



ly gentle regional gradient in this area. Therefore, a flat regional 
anomaly surface was assumed for purposes of constructing a 
residual gravity map of the Bodie mining district area Gravity 
values calculated for a density of 2.50 g/cm' were used because 
the density measurements given in Table 5 indicate that this 
should be close to the average for the Tertiary intrusive and 
extrusive rocks of the Bcxiic Hills. The value of density used is 
important, because local elevation changes, which are as much 
as 600 feet in this area, will greatly influence the results if an 
incorrect density is assumed. 

After subtracting the estimated regional gravity gradient from 
the values at indiMdiiai stations, the resulting residual values 
were plotted and contoured using a 1 mgal interval. The result- 
ing gravity map, I'late 2, shows a north-trending gravity high 
with an amplitude of 7 mgal in the south part of the district near 
Queen Bee Hill which decreases to an amplitude of about 5 mgal 
near the north end of the mining district In the southern end of 
the district, the axis of the anomaly passes close to Sugarloaf 
Queen Bee Hill, and Silver Hill, but to the north this axis turns 
northeast and passes east of Bodie Bluff. The southern end of the 
anomaly in Plate 2 appears to consist of two parts: a relatively 
broad high with an amplitude of a few mgal. up«in which is 
superimposed a second anomaly of short-wavelength with an 
amplitude of 2 <ir .1 mgal. 

Although the positive residual gravity anomaly in the Bodie 
mining district is larger in areal extent than the district, the 
anomaly appears to be spatially related to the mining district, 
particularly in the southern part. This can also be seen in the 



22 



CALIFORNIA DIVISION OF MINES AND GEOLOGY 



Bull. 206 



regional gravity map (Plate I). Furthermore, the steepness of 
the gravity gradients, especially in the southern part of the dis- 
trict, suggests that at least part of the source of the anomaly 
should be close to the ground surface. 

As mentioned above, the Bodie gravity anomaly could be 
caused by relief on the basement rock surface if these rcx'ks have 
a sufTicienlly high density and if they are at a relatively shallow 
depth beneath the mining district. Measured values of densities 
for pre-Tertiary rix;ks from the Bodie Hills area, given in Table 
5, show a range from an average of 2.60 g/cm' for plutonic 
(granitic) rocks to an average of 2.82 g/cm' for a sample of 
greenstone (altered basic volcanic rock). For comparison, the 
most common Tertiary extrusive and intrusive rcK'ks range from 
averages of 2.39 g/cm' for samples of dacite to 2.60 g/cm' for 
samples of andesite. Samples of basalt (2.79 g/cm') and Quater- 
nary tuff and pumice ( 1.36 and 1.14 g/cm', respectively) repre- 
sent extreme values for rocks which are not quantitatively 
significant in the Bodie mining district. Thus, density measure- 
ments confirm the possibility that the anomaly could be related 
to the underlying basement rock surface, considering the fact 
that dacitic intrusive and extrusive rocks are probably the most 
common of the Tertiary rock units in the area. However, this 
would require that a basement topographic high coincide in 
position with the mining district. The fact that no basement 
rocks crop out in this area and that mining operations to a 
maximum depth of about 1,000 feet apparently have not encoun- 
tered any such rocks does not tend to support this explanation. 

The other possibility is that the gravity anomaly in the Bodie 
mining distnct might be caused by an intrusive mass, which is 
believed to underlie and extend beyond the district. The average 
density of a suite of samples of the dacitic intrusive rocks from 
the mining district is 2.41 g/cm' (Table 5). This value is not 
significantly different than those for the extrusive dacite and tuff 
breccia measured (2.39 and 2.41 g/cm', respectively) and is 
decidely low for intrusive igneous rocks of this composition. 
Both the extrusive and intrusive rocks in the Bodie mining dis- 
trict are commonly affected by argillic, potassic, or prophylitic 
alteration, however, which may account for these lower than 
normal density values. The intrusive rocks exposed near the Red 
Cloud shaft. Queen Bee Hill, and Sugarloaf appear to be less 
affected by alteration than those in most of the rest of the mining 
district. Density values obtained from samples of these rocks 
average approximately 2.59 g/cm', in sharp contrast to the over- 
all average. Thus, the density contrast between these intrusive 
rocks and the surrounding extrusive rocks is nearly 0.20 g/cm' 
in this part of the area. This may explain at least the local, 
short-wavelength part of the anomaly which is closely associated 
with the exposures of intrusive rocks in the south end of the 
distnct. The remaining part of the gravity anomaly might be 
caused by a large mass of intrusive rocks at depth. These deeper 
rocks might be less affected by alteration and thus have a higher 
average value of density than those measured at the surface. The 
intrusive mass at depth may also have a different, p<5ssibly more 
basic, composition, which could also result in a higher average 
density. 

In the north end of the B(xlie mining distnct, the axis of the 
gravity anomaly turns northeastward, away from the surface 
exposures of intrusive rocks at Bodie Bluff and also eastward 
from the location of the apparent northern extension of the 
acromagnetic low. This fact is pu/.zling if the p<isitive gravity 
anomaly is caused by the exposed intrusive rcKks of the area. It 
may suggest, however, that the pnncipal intrusive mass dix-s not 
underlie Bcxlie Bluff, but instead is located ab<iut ' .. mile to the 
east An incorrect density used for reduction of the data or 
failure to obtain complete terrain corrections in the area of high 
local relief near Bodic Bluff may affect the gravity map, but 



errors of the magnitude required to shift the location of the 
anomaly appear unlikely. 

Table 5. Rock density measurements of rocks of the Bodie 
mining district and surrounding area. 



te€k tn» 



No of D«*t%dtf tango At 
Scvno o/ Onto iomptot Ig'cm') 



o*>on 1)964. 

r Ml 



OoMurf 
l» cm' I 









Docil* 

of )h« %oa^ 
maM,g diitnci oiif 



Eamnir* rock* 

of l*M »0<ft« 



Dociw 

>OK>lt 

WoldMJ tiM 

CitivtJv* racit 
of Iho Bodfo 
Mining Dtttrxt enfy 

I»ff 

brOCCM* 



TKii f 






l.U 
1.M 



1.19 



^f»- Tortioo' M«fo«ic 
racki 



M«iotuff 



Tliit lopert 
T),ii ropen 
T>wi report 
TM npofl 



Ow rot«n 

PokiM*. ond 
oihon n«6' 

r^knm.ona 
oltMn < 196, 
f> 131 

TK(( npvft 
TImi roporl 



2J4^1.M 


}ao 


2J0.3J< 


349 


- 


UT 


_ 


Ul 



J2i.2J9 


3J9 


J1HJ9 


341 


3 4}}«9 


760 


3 63-7 94 


37» 


_ 


U> 


_ 


3AS 



RESULTS OF THE GROUND MAGNETIC SURVEY 

Possible causes for the aeromagnetic low associated with the 
Bodie mining district are discussed earlier in this report. Meas- 
urements of values of the magnetic susceptibility of samples from 
the Bodie mining district (Table 4) did not provide a conclusive 
answer to the question of the cause of the magnetic anomaly, but 
did suggest that the cause might be related to rock alteration, 
particularly of the intrusive rocks. 

Plate 2 is a vertical intensity magnetic map of the Btxlic min- 
ing district with a contour interval of 200 gammas, based on an 
arbitrary datum. Magnetic values shown for most stations arc 
the average of approximately 3 or 4 separate observations taken 
around each station site. The resulting map of the magnetic field 
vanes in magnitude from a low cast of Queen Bee Hill (zero 
contour), to a high exceeding 1200 gammas southeast of the Red 
Cloud shaft Because of the irregular station interval and possi- 
ble rapid liKal variations in the magnetic field, this magnetic 
contour map may not shov* many of the lival features that would 
be detected in a more detailed survey. 

In contrast to the relationships shown by the regional anomal- 
ies, there is little apparent correlation between the gravity and 



1986 



GEOLOGY AND ORE DEPOSITS OF THE BODIE MINING DISTRICT 



23 




Photo 9. Ribbon quartz, containing fine-grained free gold. Typical of tfie veins mined in tfie Bodie 
Bluff Oreo. Photograph by Francis H. Frederick. 



ground magnetic maps of the Bodie mining district (Plate 2). 
Furthermore, the negative aeromagnctic anomaly which charae- 
lenzes this area is difficult to identify in Plate 2, but this is 
probably because of the relatively small area studied on the 
ground (a part of this negative anomaly can be seen in profile 
X-Y, Plate 1). The observed variations in the magnetic field 
shown in Plate 2 arc relatively minor features which probably are 
all within the major regional magnetic low. It would be expected, 
however, that these minor features might show some general 
correlation on the map with local geology within the area of the 
mining district. 

The highest magnetic values observed in the ground survey are 
generally, but not exclusively, a.ssociatcd with the intrusive da- 
cites and tuff breccias of the Silver Hill Volcanic Series TTie 
intermediate and low values are a.vsociated with the dacitc flows 
of the Silver Hill Volcanic Series. This is contrary to what might 
be expected, in general, from values of magnetic susceptibility 
given in Table 4. which suggest that the intrusive daciles and the 



tuff breccias might even cause magnetic lows If is probable that 
liKal magnetic values actually arc more related to the degree of 
rock alteration than to specific r(xk type. However, no consist- 
ent relationships between the magnetic map and mineralization 
or a map showing r<K-k alteration ( Plate 2 ) could be determined 
Of interest in this regard is profile X-Y which traverses the 
mining district just south of the Red Cloud shaft, where il crosses 
the northern edge of a small dacite intrusive plug, shown on the 
geologic map (Plate 2) This profile shows a sharp, local, posi- 
tive anomaly, with an amplitude of about 5(X) gammas, which is 
closely ass(K"iatcd with the intrusive rocks In contrast with 
many of the other intrusive rixrks in the Btxiie mining district, 
the Red Cloud intrusive is believed to be relatively unaffected by 
alteration The results of magnetic susceptibility measurements 
of samples of these rixks yielded a relatively high average value 
of 0.0021 emu/cc. Thus, the susceptibility measurements tend to 
confirm the apparent asMKialion of the intrusive plug and the 
magnetic anomaly in this area Therefore, il appears that rcia- 



24 



CALIFORNIA DIVISION OF MINES AND GEOLOGY 



Bull. 206 




Photo 10. Ribbon quartz veins in intrusive docite near summit of Bodie Bluff. Photograph by Francis H. Frederick. 



lively unaltered intrusive rcx;ks in the Bodie mining district 
might be more Hkely to cause magnetic highs, or normal back- 
ground values, than magnetic lows. 

Summary 

Evidence from the regional and local geophysical data in the 
Bodie mining district and measurements of some of the rock 
properties suggests the following: ( I ) the negative aeromagnetic 
anomaly is probably caused by extensive hydro! hernial altera- 
tion of the intrusive and extrusive rocks in this area, which has 
removed a large part of the normal magnetic content of these 
rocks; (2) the positive gravity anomaly is most likely caused by 
an intrusive mass underlying the Bodie mining district; (3) hy- 
drothermal solutions responsible for the rock alteration were 
probably closely related to the emplacement of the intrusive 
body, thus explaining the close spatial relationship of the major 
gravity and magnetic anomalies; (4) some of the minor magnetic 
and gravity anomalies are associated with the relatively unal- 
tered intrusive rcKks of the Bodie mining district — otherwise 
there is little apparent relationship on a local scale between these 
anomalies and riKk types, types of alteration, or mineralization; 
and (5) iheextensionsof the gravity anomaly beyond the mining 
district suggest additional areas as possible targets for mineral 
exploration. 

ECONOMIC GEOLOGY 

The mines of the Bixlie mining district have been divided, 
principally upon the basis of their geographic distribution, into 



three groups (Plate 3): (1) Standard Hill area, centering essen- 
tially around Standard Hill and Bodie Blufl"; (2) Middle mines 
area, occupying the low saddle-like area between Standard Hill 
and Silver Hill; and (3) the Southern mines area, which lies 
between Silver Hill and Sugarloaf 

More than 90 percent of the ore from lixle deposits has come 
from mines in the Standard Hill area, where the ore occurs in 
quartz veins, principally in the intrusive dacite of the Standard 
Hill-Bodie Bluff plug, and to a lesser extent in tuff breccia of the 
Silver Hill Volcanic Series (Photos 9, 10. and IDA substantial 
lode production came from several mines in the Southern mines 
area, where veins occur in flows and tuff breccia units of the 
Silver Hill Volcanic Series. Lode production in the Middle mines 
area was small and is not known, but it, too, was from veins in 
the riK-ks of the Silver Hill Volcanic Series. 

Placer operations were conducted at sites centered principially 
in a small area in the eastern part of the Middle mines area, 
where gold was first discovered in the district. The prixluction 
of gold from the Placer area is not known but was not great. 

Because accessibility of many of the mines in the distncl was 
limited during these investigations, it was necessary to make 
extensive use of published reports and pnvate reptirts for subsur- 
face information on the mines and ore deposits. Brown (1907), 
McLaughlin ( 1907). and Whiting (1888) have been the sources 
of published data, and the extensnc personal files of Francis H 
I-rederick (deceased in 19b8) provided much valuable data that 
were obtained in the district between 1929 and |9,M 

These published and unpublished data, plus our detailed field 
investigations, provide an outline of the general features of the 
mines and ore deposits. 



1986 



GEOLOGY AND ORE DEPOSITS OF THE BODIE MINING DISTRICT 



25 




Pholo 11. Quartibreccio zone, containing free gold, 436 level Bodie mine. Pencil is 5 inches in length. Photograph by Froncii H. Frederick. 



Standard Hill Area 



Brown (1907) called altenlion to the Fortuna, Incline, and 
Burgess series of veins, all of which appear to occur only in the 
Standard and Bodie mines of Standard Hill Before the mines 
had become inaccessible, the relationships of these three vein 
senes had been mapped and clearly deciphered. The Fortuna is 
the oldest and the Burgess the youngest. In order of decreasing 
productivity, the Incline is followed by the Fortuna and the 
Burgess. 

Several prominent faults, of which only the Moyle Foolwall 
fault and the Standard Vein fault arc observable at the surface, 
have cut the veins into segments The Incline senes occurs in the 
hanging wall segment of the Moyle F-'oiUwall fault and the Bur- 
gess series is in the footwall segment of this fault The Fortuna 
scries is cut and displaced by all other veins and fractures it 
meets (Figures 7. 8, 9, and 10) In spitcof theclosejuxtaposition 
of the three vein scries and the fact that they intercscct one 
another, each series has distinguishable features. 

FORTUNA SERIES 

The F'ortuna vein scries yielded the richest ore in the Bodie 
mine. The senes consists pnncipally of the Fortuna and the 



Beehive veins, which are fissure veins. The Fortuna vein did not 
crop out at the surface and was first encountered in 1878 in the 
Bodie new shaft about 340 feet below the collar. Early in 1879, 
the vein was again cut in a crosscut on the 4?0-foot level of the 
Bodie mine, about 125 feet east of the Bixiie new shaft, and its 
apparent richness was quickly determined. The Fortuna vein had 
a strike around N 10° W and a variable dip. ranging from 30 
degrees toward the east, where first encountered in the Bodic 
new shaft, to 45 degrees in the workings below the 600-fixit 
incline level of the B<xiie mine. The average width of the vein was 
no more than 2 feet (Figure 9. Photo 12). and in many places 
it was only a few inches The strike length of the Fortuna vein 
is not known, but it was encountered in the east crosscut of the 
1,000-fixit level and at points above in the Standard mine, fol- 
lowed for several hundred feet southward into the Mono claim, 
and encountered in the lower levels of the Lent shaft workings 
The Fortuna bonan/a. the /one from which the greatest value 
was produced, extended down the dip of the vein in the Bodie 
mine for some 1.000 feet It had Us maximum horizontal deve- 
lopment of .350 feet on the 600-f(X)t level of that mine and an 
average length of 200 feet. 

The quartz in the Fortuna vein is hard, flint-like. white, and 
adhered tightly to the walls Drusy cavities and comb structures 
are common The ore minerals include native gold and silver, 
argenlitc. pyritc, and sphalcntc The sphalentc content increased 



26 



CALIFORNIA DIVISION OF MINES AND GEOLOGY 



Bull. 206 




Photo 12. Fortune vein, 400 level Bodie mine looking south. Vein is approximately one foot maximum width at this ploce. Photograph by 
Francis H. Frederick. 



with depth as the gold content decreased. Minor amounts of 
pyragyrite were encountered in drusy cavities in the vein below 
the 670-foot incline level of the Bodie mine. 

At the bottom of the Forluna bonanza, near the 600-foot level 
in the Bodie mine where the dip of the Fortuna vein starts to 
steepen, a very narrow vein, referred to as the Beehive, left the 
footwall of the fortuna vein at a high angle (Figures 7 and 8). 
The Beehive vein ranged in thickness from one inch to one foot 
and extended downward from its junction with the Fortuna vein 
to the 707-foot level of the Lent shaft, a distance of about 180 
feet; below there it disappears as narrow seams and thin veinlets 
of weakly mineralized quartz. 

The Beehive vein was rich in silver and was mined extensively 
throughout its length and depth. 

The Fortuna vein was observed on the 1,200-foot level of the 
Lent shaft, where it appears to occupy a fissure whose dip steep- 
ens to an angle greater than that observed at higher levels in the 
Standard mine. The vein had dwindled down to small isolated 
bunches of quartz veinlets which were occasionally rich in gold 
and silver. The Fortuna vein was not prospected below the 1,200- 
foot level of the Lent shaft workings. 

INCLINE VEIN SERIES 

The veins of the Incline series (Figure 1 1 ) were said to be gash 
veins by Brown (l'K)7, p. .150), although the evidence does not 
always support this designation. All of the veins of this series, 
except the Gildca in the Bodic mine, terminate at or above the 
Moylc Footwall fault in the Standard mine. Important veins of 



the Incline series include the Main Standard vein, the Gildea 
vein, the Bullion vein, the Incline vein, and the Bruce vein. 

Most of the veins of the Incline senes dip to the west at high 
angles, from near vertical to 65 degrees; the main Standard vein, 
however, had a dip of only 40 degrees. At their contact with the 
Moyle Footwall fault, which is a normal fault, the dip of the 
veins flattens and many of the veins seem to curl up into masses 
of broken quartz ( Figures 7 and II). Most of the veins range in 
width from 14 inches to 6 feet, but on the 380-foot level of the 
Standard mine, the Main Standard vein, the largest in the dis- 
trict, was 90 feet wide and averaged about 20 feet. The general 
strike of the veins of the Incline scries is from north to N 20* E. 
The Main Standard vein follows closely to the strike trend of the 
Standard vein fault, which is generally N 15' E. 

The Incline vein series can be subdivided (Brown. 1907. p. 
351) into two distinct groups of veins of difTcrcnt ages. The older 
group, which includes the Main Standard and Incline veins, is 
characterized by massive, well-banded, flint-like quariz. which is 
usually firm, but in places highly fractured, and is associated 
with red ferruginous clay that was donvcd through attntion and 
alteration of the wall rtxrk. The walls of the older group of veins 
are well defined. 

The veins of the Incline scries that were fonned later, includ- 
ing the Bullion vein, are charactenzed by well-handed, ptirous 
quart/ which is crumbly and contains scarce black manganese 
oxide and minor amounts of clay. 

Post-mineral movement in the oldest group of veins accounts 
for the fractured condition of the quariz and the development of 
the clay, whereas simple crushing action is said to account for 



1986 



GEOLOGY AND ORE DEPOSITS OF THE BODIE MINING DISTRICT 



27 



the crumbly condition of the quartz and small clay content of the 
later group of vems (Brown, IW?, p. 351). 



II \Vi 





Figure 11. Cross section of the veins of ftte Incline series showing their 
relationships to the Moyle Footwoll fault. Standard mine. 
From Brown, 1907. 

The precious metal content of the Incline veins, which were 
mined profitably along a strike length of 3,000 feet, seems to have 
dropped off greatly at about the 500-foot level in the Standard 
mine. Gold content was uneven in the veins of the younger group 
of this series, and it was soon discovered that small veins (called 
"ennchers" by the miners), which branch off generally into the 
footwall, earned fabulously rich gold ore, assaying several hun- 
dreds of dollars per ton. These enricher veins, the latest of the 
series, were thought to be related to the Burgess vein series, but 
the character of the quartz and the coarseness of the gold indi- 
cate that the enricher veins are more likely a third group of the 
Incline series (Brown, 1<J07, p. 352-353). 

Although the walls of the Incline series of veins are well 
defined, the dacite adjacent to the veins is highly altered and 
contains considerable limonite, derived from pynte. Adularia 
occurs in the veins of this series, especially on the 260-foot level 
of the Standard mine, and the entire width of the Bullion vein 
was composed of coarse quartz. 

BURGESS VEIN SERIES 

The Burgess scries makes up the youngest veins in this part 
of the distncl, and includes the Ralston vein in the Standard 
mine (Photo 13). These veins arc rep<irted to lie in the f(Xitwall 
below the Moyle Footwall fault, and very few of ihcm reached 
the surface Their strike trend is from north to N 20" E and their 
dip IS at high angles toward the east They arc rarely a foot in 
thickness and arc charactenzcd by weakly banded, while quartz 
with a comb-like structure, generally at the center of the vein. 
It was common to find a thin layer of high-grade, gold-bcanng 
quartz, referred to as "scale", adhering to one of the vein walls. 
An unfailing indication of nch ore was a layer, up to '/,K-inch 



thick, called "shale," composed of ground wall-rock and quartz 
particles in clay. Brown ( IWT, p. 354) suggested thai the 
"shale" indicates movement along the vein. 

The dacite adjacent to the veins is altered, but limonite is not 
abundant. Some of the veins were rich in gold, so much so that 
veins no more than ' ..-inch thick were sloped. Not only were the 
veins rich, but the wall rock on both sides of the vein for as much 
as several feet contained sufficient gold to make the vein zones 
worth mining. The so-called Burgess bonanza, which was some 
12 feet in width on (he 300-foot level of the Bodie mine, consisted 
of mineralized wall rock and numerous, rich, narrow quartz 
veins. The length of the Burgess vein series is not known, but the 
Ralston vein was prospected and mined for a distance of more 
than 500 feet. 

Middle and Southern Mines Areas 

Many of the mines in the Middle mines and Southern mines 
areas have been under water since 1882 and hence were not 
accessible to the early investigators who provided so much of the 
useful data on the veins in the Standard Hill area. Work done 
in the early 1930s by Treadwell-Yukon Company, Ltd., especial- 
ly in the Red Cloud mine, provides a limited amount of informa- 
tion on the Concordia, Red Cloud, and Booker veins, all of 
which appear to have provided the principal lode production in 
the Southern mines area. 

CONCORDIA VEIN 

The Concordia vein was the principal producer of silver and 
gold in the Noonday mine and was encountered on several levels 
in the western part of the Red Cloud mine. On the 402-foot level 
of the Red Cloud mine west of the Red Cloud shaft, the Con- 
cordia vein dips 60° E and has a strike of about N 5° W. Farther 
south, this ■. ..n changed to a south strike and a dip of 65° E. The 
vein ranged in width from a few inches to as much as 12 feel. 
It consists of vuggy white quartz, coarse-grained calcite. pseudo- 
morphs of quartz after calcite, and clayey gouge. The ore miner- 
als are tetrahedrite, pyrargyrite, and pyrile. 

Several ore shoots were encountered and sloped in the Con- 
cordia vein in the Noonday mine. The largest and most imp<ir- 
tant of these shoots was encountered between the 450-foot level 
and the 700-foot level. It raked to the south, measured 400 feet 
in length on the upper levels, and b<illomed on the 7C)0-f(Xit level. 
The best ore mined from this shtwt in the Concordia vein was 
more than 3 feet wide and had an average per-lon content of 
about 6 ounces of gold at the 1931 price of S20.6718 per ounce) 
and 53 ounces of silver. It was presumably from this ore shcxit 
that most of the total production of SI, 200,000 was realized for 
the Noonday mine. 

RED CLOUD VEIN 

In most places where the Red Cloud vein was encountered and 
developed, it was accompanied by gouge and crushed quartz Its 
strike is generally to the north and its dip to the east ranges from 
near vertical lo 45 degrees The vein ranges in width from a few 
inches lo 4 feel On the 256-fiHM level of the Red Cloud nunc 
north of the shaft, the vein consists of a zone of numerous 
narrow, parallel, and anastonuzing quartz veins and gouge Far- 
ther south on the same level, the vein became a definite band of 
yellowish ribbon quartz and calcite. One ore shoot, stopcd 
between the 256-foot level and the 592-f«it level, was 120 feet 
in length, 4 feel in width, and raked to the south The total Nalue 
of the ore, in gold and silver, was S10.05 per ion at 1931 prices 



28 



CALIFORNIA DIVISION OF MINES AND GEOLOGY 



Bull. 206 




Photo 13. Ralston vein, just off Bulwer tunnel, looking soutfi. Photograph by Francis H. Frederick. 



At deeper levels in the Red Cloud mine (Photo 14), the Red 
Cloud vein was consistently better defined and contained, in 
addition to quartz and pseudomorphs o( quartz after calcite, 
coarse-grained calcite and fine-grained adularia. Ore minerals 
included tetrahedrile, pyritc, galena, chalcopyrite. and minor 
sphalerite. Pyrargyrite was reported to be present in the Red 
Cloud vein by OH Hershey (written communication, 1^29). 

ORO VEIN 

The Oro vein, the pnncipal vein developed and mined m the 
Oro mine, has a general strike from N 10* E to north and a dip 
of 50* E (locally steeper) The length of the vein is not known, 
but mine maps show at least 400 feet It ranges in thickness from 
2 to 6 feel Must of the ore was obtained from a north-raking 
shoot which assayed as high as S.140 per Ion at 1*1 .M values for 
gold and silver Ore minerals included letrahednte, stephenile, 
pyrargyrite, pyrile, and galena. 



BASE METAL VEIN 

Hershey, in his study of the mines of the Btxlie mining district 
(written communication to Treadwell-Yukon Co., Inc., I''2<'), 
applied the name of "Base Metal \ein" to a minerali/ed /one 
which he maintained extended discontinuously from the Bulwer 
tunnel in the Standard Hill area to the King Bee shaft on Queen 
Bee Hill (Plate 2). a distance of about 8.000 feet. According to 
OH. Hershey (written communication to Treadwell-'^'ukon 
Co., Inc., 1''2'') this vein's maximum development in grade and 
width in the Silver Hill area ranged from 12 to 250 feet in the 
Red Cloud mine No zone corresponding to the Base Metal vein 
could be found on the surface. In the Red Cloud mine, a zone 
was encountered This /erne consisted principally of intensely 
brecciated wall rtx'k that had been bleached and replaced in part 
by veins of comb quart/ and irregular bixlies composed of 
quart/, calcite. and adulana The quartz is generally fine grained 
but developed into glassy, needle-like crystals lining vugs and as 



1986 



GEOLOGY AND ORE DEPOSITS OF THE BODIE MINING DISTRICT 



29 




Photo 14. ArgiUicotly altered lu(f brcccio of the Silver Hill Volcanic Series, cemented by dark groy, 
pyrite-rich chalcedony. 700 level of the Red Cloud mine. Photograph by Francis H. 

Frederick. 



pseudomorphs after calcite. Calcite commonly occurs as fine- 
grained intergrowlhs with quartz, and lamallar plates up to one 
inch across arc not uncommon. The adularia is fine grained and 
occurs largely m the fine-grained, quartz-calcitc intergrowlhs. 
Pyrite is abundant and occurs as small crystals, usually less than 
Vi inch across, disseminated throughout the bleached and altered 
dacite fragments. The largest pyrite crystals occur in vugs in 
quart/ masses and veins. Other ore minerals include letrahednle, 
pyrargynte, galena, chalcopyrilc, and sphalerite; a/urite and 
malachite are rare and pnncipally represent alteration of chalco- 
pynlc. 

According to E.W. Billeb (oral communication to the au- 
thors, 1965), a small ore shoot in the Base Metal vein was 
developed and sloped in the 622-A raise of the Red Cloud mine. 
This shoot was about 50 feet long and 3 feet wide; it had an 
average pcr-ton content of about one ounce of gold ($20.55 at 
the 1931 pnce of $20.6718 per ounce) and 32.27 ounces of silver. 



BOOKER VEIN 

Several prominent veins were prospected in the area between 
the Noonday mine and Queen Bee Hill The Booker vein ( Plates 
2 and 5) seems to have been the largest and most promising of 
these and the one that was developed the most. In the vicinity 
of the Noonday mine, the Booker vein stnkcs north, but farther 
south It bends to the east, stnkcs S 30* E and dips 40' E The 
thickness of the vein is not known, but near the Booker shaft it 
is less than one f(wt The vein appears lo consist of quart/ and 
calcite, and much of the quart/ is pscudomorphous after calcite 
Pyrite is present, usually as small crystals in the quart/ 

Distribution of Metals in the Veins 

A characteristic feature of the veins in the Southern mines 
area is the direct relationships between their silver and gold 



30 



CALIFORNIA DIVISION OF MINES AND GEOLOGY 



Bull. 206 




Photo 15. Lent shaft hoist house and office, as it appeared in 1895. Photographer unkown (Frederick, 1960, private communication). 



content and the amount of quartz present. Those veins that had 
the highest quartz content had the highest content in silver and 
gold, both contained in minerals such as tetrahedrite, pyrargy- 
rite, and pyrite. 

Because of the inaccessibihty of the underground workings of 
the mines (Plate 4) in the Standard Hill area, it was not possible 
for the writers to obtain first-hand information regarding the 
distribution of metals and the grade of ore. 

Whiting (1888, p. 389), from whom much of the data about 
the vcms in the Standard Hill area was obtained, made the 
following comment regarding the metal distribution in the In- 
cline and Burgess vein systems: "In all of these younger series 
of hxles the gold content largely exceeds in value that of the 
silver, though in the relative proportions of the two metals by 
weight, the silver is somewhat in excess of the gold tenor. In the 
average assay value of the Standard ore, as given in its Superin- 
tendent's rep<irt for the fiscal year ending February 1, 1883, the 
gold content was stated at $34.28 per Ion, the silver at $4.07, in 
a total of $38.35 per ton of two thousand pounds. Its silver value 
was calculated at $1.2929 per troy ounce, the gold at $20.6718 
per ounce In weights, therefore, the average gold contents of the 
ore for the year were 1.65 troy ounces per ton; while the silver 
tenure amounted to 3.14 ounces per ton, furnishing 65.6 percent 
by weight of the precious metals in the ore of these so-called gold 
mines. The native gold of these Bodic veins, moreover, is itself 



an alloy with silver in the proportion of about six hundred and 
ninty-five thousandths gold and three hundred and five thou- 
sandths silver. Apart from this occurrence of the silver, however, 
these veins also carry that metal in flakes and wires, and mineral- 
ized as argentite and kerargyrite..." Further along in his report. 
Whiting (p. 392) slates, "As is the case along all of the Bodie 
fault fissures the andesite on either wall of the nch vein is more 
or less thinly sheeted, and along such structural planes, to the 
depth of a fixit or more from this narrow quartz vein, nalise 
silver was often found in the wall-rock, in small fronds and wires; 
so that where the quartz of the vein did not exceed six inches in 
width, from eighteen inches to two fc"et could be profitably 
mined." 

Brown ( 1907, p. 347), in his analysis of the veins in the B<xlic 
mining district, stated, "The Fortuna is the only \ein with 
marked easterly dip. It is also the only one presenting the charac- 
teristics of a strong, deep-reaching zone of fissunng Unfortu- 
nately, this permanency is of structure alone, and does not 
extend to Ihe contents; for in the lower portions the vein rapidly 
becomes imp<nerished; sphalerite, from being almost absent, 
increases to a large percentage; gold values weaken and almost 
die out; and silver diminished to a few sparse patches of wire in 
ma.s.scs of impure, bluish kaolin." 

Wisser (I960, p 76) summed up Ihe relation of structure to 
nictalli/.;ition at the B<x)ie mining district as follows; "All Bodie 



1986 



GEOLOGY AND ORE DEPOSITS OF THE BODIE MINING DISTRICT 



31 




Photo 16. View of Bodie looking southwest from Standard Hill. Excavation in foreground is port of lorge scale sampling conducted by 
Yukon-Treodwell Compony, Inc. in the Spring of 1931. Photograph by Francis H. Frederick. 



veins earned both silver and gold, but some were relatively high 
in silver, some in gold. Where earlier vein matter was fractured 
and later vein minerals deposited in the openings created, the 
later vein matter was invanably richer in gold than the earlier. 
Solutions, therefore, changed in time from relatively silver-rich 
to relatively gold-nch " 

Depth of Mineralization 

As was brought out in the discussion of the veins, mineraliza- 
tion in the district appears to be shallow , and the precious metals 
values rarely e.xtended much lower than the 500-foot level in any 
mine. This is especially true in the Standard Hill area for the 
Incline and Burgess vein series. The Fortuna vein, an exception 
to the general depth rule, was mined down dip for 1,000 feet, or 
to a depth of about 600 feet below the surface. 

Mineralization in the Southern mines area appears to have 
extended at least 800 feet below the surface. Below this depth, 
veins continue but consist almost wholly of calcile with an occa- 
sional small irregular body of quartz pscudomorphous after cal- 
cite. 

The depth to which precious metal mineralization extends in 
the Middle mines area is not known, although the Dudley shaft 
(Plate 2) IS said to have been sunk 500 feet below its collar (O.H. 
Hcrshey. written communication to Treadwell-Yukon Co., Inc., 
1929), and no veins of any significance were encountered in 
cither of the long crosscuts extending east and west from the 
bottom of the shaft. 

A study (ONcil and others, 1973, p. 780) of the stable iso- 
topes of hydrogen, oxygen, potassium, rubidium, and strontium 
in the quartz veins and their unaltered and altered host rcKks, 
and alteration clay, fluid inclusions, and mcxicrn spring waters 
in the district indicates that alteration and ore deposition oc- 
curred over the approximate temperature interval of 2 1 S-240* C. 



The study also indicates that the source of the ore constituents 
is probably magmatic and perhaps from the same source as was 
postulated for the dacite plugs of the district. 

HISTORY 
OF MINING AND PRODUCTION 

The discovery and early development of the mines in the BtxJie 
mining district have been described by Cain (1956. 196 p ). 
Billeb (1968, 229 p.), and Wedertz (1969. 211 p ). all former 
residents of Bodie. The account by Wedertz goes into considera- 
ble detail on the mines of the district. Early accounts on the 
mines of the district are by Browne (1865. p. 274-284) and 
Wasson ( 1879, 46p. ). Other accounts have been published in the 
past 10 years, but they deal primarily with events that took place 
in the town of Bodie and only incidentally with the mines of the 
district (Johnson, 1967, 119 p; Calhoun, 1967, 172 p.). These 
reports and information obtained from discussions with Emil W 
Billeb and others who have been closely associated with the 
mining activities of the district were the source's for preparation 
of this historical sketch. 

Gold was discovered in the Bodie mining district in mid- 
summer of 1859 in shallow placer deposits situated in the east- 
central part of the district. Later that summer, gold-bearing 
quartz veins were discovered on a claim, then known as the 
Montauk (Plate 3) but now called the Gixxlshaw. In I860, the 
mining district was organized and named B<xley; in 1862 the 
spelling was changed to Bodie The first mining company was 
formed in 1863 when owners of several adjacent mines con- 
solidated their claims and holdings to form the litnlic Bluff 
Consolidated Mining Company with Governor I.cland Stanford 
as president and Judge F' T Hechtel as secretary 

Between 1859 and 1876. spxiradic development was earned on 
in the district with moderate production, no statistics on this 



32 



CALIFORNIA DIVISION OF MINES AND GEOLOGY 



Bull. 206 



development are available. Rich ore found on the Bullion loca- 
tion in 1872 was milled in arra-siras on Rough Creek, about 5 
miles northwestward from the district. In April 1877 the Stand- 
ard Mining Company was incorporated, and the first ore mined 
by the new company was milled in the Syndicate mill, which was 
situated on Bodie Creek at the north end of the district. Soon 
thereafter, however, the Standard Mining Company constructed 
Its own mill. 

Rich ore found in the Standard mine in 1878 sparked a boom 
which lasted for about 10 years, during which period as many 
as 50 companies were operating simultaneously in the district. 

Costs of mining and milling of the ores were very high in the 
district, owing principally to the high cost of firewood for the 
generation of steam. In the early 1890s, the Standard Mining 
Company brought in electrical power for mining and milling 
purposes from its hydroelectric power plant on Green Creek, 
some 13 miles to the west of the district. The introduction of 
electrical power into the district dramatically reduced mining 
and milling costs, and this, in turn, stimulated new interest in 
developing the mines. 

The bonanza in the Standard mine was exhausted in the late 
1 880s and the district was faced once more with drastic decline 
in production, activity, and interest. In 1915, the Standard Con- 
solidated Mining Company was dissolved and its properties were 
acquired by the J.S. Cain Company, which still retains title to 
them. Small-scale lease operations continued for about 15 years 
on high-grade ore in place and on tailings and mine dumps. 

The first systematic development of the Bodie mining district 
was undertaken between 1928 and 1931 by theTreadwell-Yukon 
Company, Ltd. Extensive, deep exploration were conducted in 
the Noonday and Red Cloud mines of the Southern Consolidat- 
ed Company. A total of 18,000 feet of drifting and crosscutting 
resulted from these exploration attempts to locate a southern 
extension of the Fortuna vein. Although the results were en- 
couraging, the search was eventually abandoned. Treadwell-Yu- 
kon also examined the Standard Hill mines area, by 
systematically sampling underground and surface exposures 
(Photo 15) and by a large-scale pilot plant investigation of treat- 
ment of mine dumps and surface ore in place. 

Treadwell-Yukon discontinued its investigations in 1931. In 
1935, the Roseklip Mines Company, organized by John Rosek- 
ranz and Henry Klipstein, obtained a lease from the J.S. Cain 
Company and constructed a mill and cyanide plant of 500-ton- 
per-day capacity. It was operated continuously until 1942, at 
which time most gold mining ceased in the United States. Dunng 
this period, the mill treated 346,000 tons of material from dumps 
and 55,000 tons of ore mined by mechanical shovel from surface 
cuts. 

In 1945 the J.S. Cain Company leased the mines to Sierra 
Mines Incorporated. This company proposed to continue opera- 
lions to confirm the existence of a large quantity of marginal ore 
in the Standard Hill mines area. This operation, however, was 
short-lived, for on April 3, 1946, a fire of accidental origin de- 
stroyed the mill and cyanide plant, which at the time were being 
enlarged to a capacity of 20.000 tons per month. 

Since 1946. sporadic interest has been shown in the district. 
The American Smelting and Refining Company acquired most 
of the properties in ihe district in 1967 through lease and option, 
and in the summer and fall of 1968 carried on a brief extensive 
program of sampling both underground and on the surface, and 
the testing of ores. In 1970. the Phelps D<xige Corporation ac- 
quired a lease on the properties in the dislncl and immediately 
commenced a detailed, systematic sampling of veins exposed at 
the surface and in mine workings that could be made easily 
accessible. By 1972. prospecting by core dniling was started, 
particularly in areas where previous mining activities had not 
been extensive. 



Table 6. 



Year 

1860- 1876' 

1877 

1878 

1879 

1880 

1881 

1882 

1883 

1884 

1885 

1886 

1887 

1888 

1889" 

1890 

1891 

1892 

1893 

1894 

1895 

1896 

1897 

1898 

1899 

1900 

1901 

1902 

1903 

1904 

1905 

1906 

1907 

1908 

1909 

1910 

1911 

1912 

1913 

1914(2) 

1915 

1916 

1917 

1918 

1919 

1920 

1921 

1922 

1923 

1924 

1925 

1926 

1927 

1928 

1929 

1930 

1931 

1932 

1933 

1934 

1935 

1936'" 

1937 

1938 

1939 

1940 

1941 

Totals 



(1) 



Go\d 


Silver 


Value 


Value 


731.06302 


67.86728 


1.890.531 18 


239.66914 


2.371.964 36 


298.137 13 


2.333.59086 


636.66386 


2.743.39177 


416.675 74 


1.751.152 07 


466.62817 



Production of gold and silver of the Bodie mining 
district. Mono County, Californio, from 1860 fo 
1941. 

Total 
Value 

4.000.000 00 

798.950 30 

2.130.200 32 

2.670.12149 

2.970.253 87 

3.160.067 51 

2^17.780 24 

1.582.667 08 

1.123.583 96 

449,765 95 

526.455 15 

341.782 03 

126294 91 

193.264 00 

144.18000 

302.514 00 

396296 00 

293.637 00 

358.824 00 

552.690 00 

451.552 00 

520.10100 

446.107 00 

697.069 00 

670200 00 

493.355 00 

510.596 00 

334,713 00 

268.930 00 

311.959 00 

338.698 00 

383.971 00 

413.946 00 

3S4.90900 

435.724 00 

261232 00 

377,518 00 

141.772 00 

6,82100 

107,302 00 

237.064 00 

209.040 00 

31252 00 

29,42800 

144.746 00 

37.754 00 

65,74700 

34.66100 

49.65100 

5.50300 

20204 00 

3.68600 

6.X7 00 



9077134 



26.773 00 


16.30000 


95.48100 


72.888 00 


100.94200 


78,335 00 


150278 78 


76.669 


133.965 37 


89.65886 


223.55163 


59,43865 


12.643.496 38 


2.518.93083 



90.771 34 



43.07300 
168.36900 
179277 00 
226,94863 
223.624 23 
282,99028 

33554,91929 



' (islimale based upon sparse reporting ol annual production value 

' ' Between 1889 and 1928. total value includes $2,960,000 00 in goU and $4,815. 

869 00 in silver reported from oilier districts m Mono County 

• • • GokJ calculated at S35 00 per line ounce and silver at $0 70 per line ounce 

lor period Irom 1936-1941 

( 1 1 Between 1860 and 1935 gold was calculated at $206718 per fine ounce and 

silver at $1 2929 per line ounce 

(?) Standard Mill closed down 



1986 



GEOLOGY AND ORE DEPOSITS OF THE BODIE MINING DISTRICT 



33 



Table 7. Production, dividends and operations of the Standard Consolidated Mining Company, Bodie mining district. 
County, Californio (Eakle & McLoughlin, 1917, p. 151). 



Mono 



1177- 

ino 
ini 
im 






na 

MM 
IMS 



mo 
itii 
ifij 
»i] 



'•.437710 
1.033 3*3 35 
1.441.134 47 
I.39V.U4 67 
I.937.t43 33 
7.049.331 33 
»,t73.73«0t 
t.0»4.914 46 

347.093 74 

nt.nioo 

M3.707IO 
137440 94 
1 34.900 17 
Ua.73 36 
33 79937I 
7]9.]«l 70 
17135139 
193.907 30 
>3«17 9« 
J94J7»97 
M1.73aO 
443.179 91 
4U.*I>7I 
U1J04.0S 
M0.77S.40 

3n.ayst 

nijTon 

373.04&9I 

mow 03 

1»U>47J« 
3J3.3U03 
n«.4040l 
J47.9JJJ9 
n3.47&<l 
in.9D3)4 
133.943 69 
tU.304.79»U 



Vokf p*> 



r<ni o/ 



Coil mtning 


P*rc«Al 


Tolol 


p«r ion 


U»«d 


pvnwit 




tn mtl 


tC*Ml 



•90.000 00 

330.000 00 
930.000 00 
973.000 W 
•73.00000 
373.000 00 
30.00000 



x.ooooo 

40.000 00 



I •903 to 
3«S34 30 
ia.903(0 

37.ao3.ta 

I •.903 10 

UiTtao 
M.tft.ao 

S3.511JO 

7U)7«a 

71.357 40 
71J57 40 
S3J1t.30 

17.(39 40 
44 39*30 
33.t7«a0 
33.i7«^KI 

17.t39 40 
17.nt40 tt 

44.39*30 

3.364 407 SO 



r.430 
6.930 

10.111 
10.160 
13.967 

13J3« 
I7.M3 
30.473 
ia.047 
14.734 
17,734 
10.310 
1^.340 
16.031 
14.339 
11J33 
13.13* 
•.79* 
•.130 
6J43 
360.901 



3*44 
1663 
30 40 
33 37 

3«71 
3&06 
19.14 
l>4a 
30 70 
l>36 

19 77 
17 13 
14.34 
14.14 
14.M 
14^14 
1171 
130* 



I 

I 

I 

7.017 

7J4J 
11.037 
9.337 

10.603 
13.93* 
14.773 
11433 
14.t61 
30.934 



9.147 
*179 
14.7*4 
13.433 
13.077 
14.749 

319,903 



1143 
<U4 

Ml] 
4407 
4034 
33*3 
4741 
7M1 
7304 
6106 
6049 

3437 
1634 
»*} 
60*7 
4440 
«»4 
4214 
3*46 



37a 


6.03 


493 


9(3 


143 


731 


113 


*90 


393 


734 


333 


*ll 


IK) 


*oa 


3 17 


74a 


19« 


793 


339 


905 


3 34 


• 13 


169 


397 


160 


436 


143 


493 


113 


733 


163 


a79 


1.2a 


755 


303 


1367 


193 


10 71 


164 


10 50 



— AtMtuMMi «l |33.00a00 



— AtM*iM*Af ol 373.000 00 



^ fWotK pew*, wttTodwcd 



— SAnM. crOM,d« pion< b«90>< flp«i 



90 MJ ond Umm plant ckM*d. Ociofe** i« end tt ftrnt 



•frvm wKrw^ laaa. p 19* 

tCa>6w hgum i^woJohh 

tTOvy III iii| | i tnm 1911. »«t 



Thi.s apparently was the first core drilling in the Bodie mining 
district. Mine records fail to indicate whether any long-hole 
percussion drilling had been done in the mme workings. Because 
many of the veins thai were profitably mined underground have 
not been found at the surface, especially in the bonanza zone, 
core drilling from underground mine workings may disclose new 
veins or extensions of veins that had been dislocated by faulting 
but not found by crosscutting and drifting. 

Dunng the productive life of the Standard Consolidated mines 
from 1877 to 1915, the group accounted for more than 90 per- 
cent of the bullion produced in the district, which exceeded 
$18,000,000 in value at pnces prevailing at that lime (see Tables 
6 and 7). 

In the course of mining and milling ore from the bonanza 
zone, an estimated 527,000 tons of waste material was hoisted to 
the surface and placed as waste dumps. An estimated 150,000 
tons of waste material remains underground as slope filling. 

The Bodie Histonc State Park was created in 1956 to preserve 
a ghost town of a colorful past It encompa.sses the townsite of 
Bodie but docs not include the mining properties in the Bodie 
mining district 

Milling 

The first ore mined in the Bodie mining district was milled in 
arrastras on Rough Creek, about 5 miles northwestward from 
the district, and some ore was hauled 1.1 miles to Aurora. Ne- 
vada, and processed in stamp mills 

Ab<iut 186.1 a mill was established low at the western base of 
Bodic Bluff (Wcdertz, 1969, p 178) By 1882, eight mills were 
operating in the district; they contained 140 stamps, all powered 
by steam engines. 



The Bodie ores were characterized as "free-milling." A large 
percentage of the gold was recoverable in the free and relatively 
pure stale by amalgamation or strakc (shaking table) concentra- 
tion. The silver occurs in the gold and as sulfides or as the 
chloride-cerargyrite. In the early 1900s, it was found that the 
Bodie ores were amenable to simple cyanidation; the process 
yielded high extraction with relatively low costs and low con- 
sumption of reagents. 

SUGGESTIONS FOR PROSPECTING 



On the basis of sampling by Treadwell-Yukon Company, Inc., 
during the early 1930s, the bonanza zone (a highly prtxluctive 
block bound by the Mono, Tioga, Moyle Footwall, and Standard 
Vein faults) offers the best possibilities for new exploration and 
development This conclusion is ba.sed up<in several factors: ( I ) 
the character and widespread distribution of innumerable veins 
in the bonanza zone, of which many yielded high-grade ore; (2) 
productive history of the mines in this zone; and (.1) detailed 
sampling of some of the underground workings in the margins 
of the bonanza zone. 

The bonanza zone yielded more than 6.1.1.000 ounces of gold 
and as many as 800.000 ounces of silver from approximately 
.180.000 tons of ore (SB. McCluskey, written communication. 
Rcp<irt to Sierra Mines, Inc.. 1947). It has been estimated that 
the bonan/ji zone still contains as much as 25,000,000 tons of ore 
whose average value in 1947 was reported to be $1 86 per ton. 
rurthcrmorc, this value might be increased substantially (to 
perhaps $2 10 per Ion) from enrichment due to fills, pillars, and 
veinlets of high-grade ore that were undiscovered or rejected 
because of the high costs of operating the mines 



34 



CALIFORNIA DIVISION OF MINES AND GEOLOGY 



Bull. 206 











im^f^ ■i-.'i.iri 



Jt^ 



■IX 



Photo 17. View north toward Standord Mill. High peck is standard Mill 



Zones of marginal ore lie in the footwalls of the Moyle Foot- 
wall and Standard Vein faults adjacent to and on the west and 
east sides of the bonanza zone and on Bodie Bluff on the north 
side of the Tioga fault. The marginal ore zones contain many 
quartz veins, barren and ore-bearing, and an intervening lattice 
of veinlets, stnngers. and seams which form a stockwork in the 
firm intrusive dacite. 

Underground workings in these zones are, in a majority of 
cases, accessible, and from them drilling can be done in many 
directions, even into the bonanza zone, where mine workings 
have been inaccessible for many years. 

Only a few of the veins south of the Mono fault were produc- 
tive, but those that were apparently barren or too low in grade 
to be considered at the time were not explored along their length 
or to any significant depth. These veins occur in highly altered 
tuff breccia and dacite flows, and, as most of them are also highly 
mineralized, none should be overlooked. 

Because of extensive surficial debris at the southern end of the 
B<xlie mining district, especially in the areas surrounding Sugar- 
loaf and underlain by units of the Silver Hill Volcanic Scnes. 
very few quartz veins and zones of mineralized rock were found 
at the surface 

Samples of mineralized rock containing significant amounts of 
pyrargyrite and pyrite were collected from the waste dump of a 
shaft that is located about 2.000 feet south of Sugarloaf and were 
found to contain 18 ounces in silver and 0.2 ounces in gold. 
Pyrargyrite and pyritc were found on the waste dumps of other 
prospects in this particular area, thus indicating widespread min- 
eralization worthy of consideration and/or testing. 



REFERENCES 



Al-Rowi, Y.T., 1968, Age and structure of mineralization ot Bodie District, 
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Al-Rowi, Y.T., 1969, Cenozoic history of the northern port of Mono Basin. 
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163 p. 

Anderson, C.L., 1880, Mop of the Bodie mining district. Mono County, Cali- 
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Atwood, M.. 1879, Wall Rocks of the Bodie auriferous lodes: Mining and 
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Billeb, E.W., 1968. Mining camp days: Howell-North Books. Berkeley, Coli- 
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Bloke, W P., 1862, in Complete guide to Mono County mines, by Joseph 
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Browne, JR., 1865, A trip to Bodie Bluff and the Dead Sea of the west: 
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Brown. R.G.. 1907. The vein system of the Stondard mine. Bodie. Colifomio: 
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Colhoun, M., 1967, Pioneers of Mono Basin: Robert C. Calhoun, 172 p 
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1986 



GEOLOGY AND ORE DEPOSITS OF THE BODIE MINING DISTRICT 



35 



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Chestermon. C W , and Groy. C.H., Jr., 1975, Geology of the Bodie 15 
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Loose, W., 1971, Bodie Bonanza: Exposition Press, Jericho. New York, 246 

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Mojmundar, H.H., 1973, privote communicotion. 

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Sillimon, B., 1864, in Complete guide to Mono County mines, by Joseph 
Wosion: Joseph Wosson (1880), p 13- 15 

Streckeisen, A.L., 1967, Clossificotion ond nomencloture of igeneous rocks: 
Neues Jahrbuch fur Mineralogie Abhandlungen, v. 107, p. 144-240. 

Wosson, J., 1879, The mines of Bodie, o complete and occurote occount of 
the mining properties in and odjocent to the town of Bodie. Mono 
County, Colifornio: The Mining Record Office, New York, 46 p 

Wedertz, F.S., 1969, Bodie, 1859-1900: Cholfant Press, Inc , Bishop, Colifor- 
nia, 21 1 p. 

Whiting, H.A., 1888, Mono County: 8th Report State Mineralogist, p 382- 
401, 

Wisser, E., 1960, Relation of ore deposition to doming in the Americon 
Cordillera: Geological Society of America Memoir 77, p. 70-77. 

Woollord, G.P., ond Joesting, H.R., 1964. Bouguer grovity mop of the United 
States (exclusive of Alaska ond Howoiil: American Geophyncol Union, 
Special Committee on the Geophysicol and Geological Study of Conti- 
nents, and U.S. Geologicol Survey, scale 1:2,500,000. 



APPENDIX: 



K-Ar Sample Description and Locations* 



1. Adulona-quortz vein (S-centrol Sec. 9, T4N, R27E, on south tide of 
Standard Mill. Mono County. California) USGSIM) -7346-1. 

2. Adulorio-cokite-quartz vein (S-centrol Sec. 16, T4N, R27E, watte dump 
of Red Cloud mine. Mono County. Colifornio) USGS|M| RCD1B 

3. Adulorio-quortz vein (S-centrol Sec. 9. T4N, R27E. wotte dump of 
McClinton thofl. Mono County. Colifornro) USGS (M) -B270. 

4. Porphyritic biolile fiomblendc docile mtruiive |NW '/^, Sec. 21, T4N, 
R27E, about 500 feet loutti of Red Cloud thofl. Mono County, Colifor- 
nio) USGS(M) BH15. 

5. Porphyrilic hornblende docite intrutive (SW '/, Sec. 21. T4N, R27E, on 
lop of SugoHoof, Mono County, Colifornia) USGS (M) -SI 

6. Altered porphyntic hornblende docite intrutive of Bodie Bluff |S central 
Sec 9. T4N. R27E. cut »rett of Siondord thoft. Mono County. Colifor 
nio) USGS(M) B271 

7. Porphyritic hornblende docite intrutive ol Queen Bee Hill (NW '/i S«c. 
21. T4N. R27E, Mono County. Colifornio) USGSIM) BH17. 

8. Pofphyritic hornblende pyronene ondetite flow, "Wall Andciite" (SE '/« 
Sec. 10, T4N, R27E, Mono County. Colifornio). USGS (M) -7346-3. lo- 
cality off mop. 



9 Porphyritic biotitehornblende docite (NE Vi Sec. 21, T4N, R27E. Mono 
County. Colifornia) USGSIM) BH32. locolity off mop. 

10. Porphyritic biotitehornblende docite IE centrol Sec 16. T4N, R27E. old 
quarry near ditmontled railroad. Mono County, California) . USGS(M) - 
85632. 

11. Porphyritic biotite-hornblende-rhyodocite intrutive (W-centrol Sec. 16, 
T4N, R27E, 1 mile touthwetl of Bodie. Mono County. California) . 
USGS(M) 856 10 locolity off mop 

12. Porphyritic biotile hornblende docite flow, lower unit of compotiie flow 
|NE '/. Sec 16. T4N, R27E. about 2000 feet eoit of Red Cloud mine. 
Mono County. Colifornia) USGS(M) BM16. 

13 Porphyritic bioliie docite flow (N centrol Sec. 28. T4N. R27E. Mono 

County. Colifornio) USGSIM) 854-1 
14. Porphyritic biotite docite flow (center Sec 12. T4N. R26E. Mono Coun 

ty, Colifornia) USGS(M) BM2 locohty off mop 

15 Porphyritic biotite hornblende docite intrutive (NE \ Sec 23. T4N, 
R27E. near ditmontled roilrood. Mono County. California). USGS|M|- 
BH29 locality off mop 

16 Porphyritic rhyolite ( SW >/, Sec 7. T3N. R26E. Mono County. Colifor 
mo) USGS(M) BH27 locolity off mop. 



*Fke4d numbm ihown on pUir 1 



THIS BOOK IS DUE ON THE LAST DATE 
. ^, ^ STAMPED BELOW 

BOOKS REQUESTED BY ANOTHER BORROWER 
ARE SUBJECT TO IMMEDIATE RECALL 



I 



FEB 2 1 ^993 
RECEIVED 

■."• V 



4 



LIBRARY. UNIVERSITY OF CALIFORNIA. DAVIS 

D4613(7'92)M 



m 




THIS BOOK IS DUE ON THE LAST DATE 
STAMPED BELOW 



/*f K 05^5 



BOOKS REQUESTED BY ANOTHER BORROWER 
ARE SUBJECT TO IMMEDIATE RECALL 



FEB 2 1 ^993 
RECEIVED 



LIBRARY. UNIVERSITY OF CALIFORNIA, DAVIS 

04613 (7.92IM 



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DIVISION OF MINES AND GEOLOGY 

JAMES F, DAVIS, STATE GEOLOGIST 




STATE OF CALIFORNIA - GEORGE DEUKMEJIAN, GOVERNOR 
THE RESOURCES AGENCY - GORDON K VAN VLECK, SECRETARY FOR RESOURCES 
DEPARTMENT OF CONSERVATION - RANDALL M. WARD, DIRECTOR 






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GEOLOGIC MAP 

SHOWING MAGNETICS, 

GRAVITY, AND 

ROCK ALTERATIONS 

BODIE MINING DISTRICT 
Mono County, California 



Geology by 
Charles W. Chesterman & Cliffton H. Gray 

Geophysics by 
Rodger H. Chapman 



PHrSICAl SCIENCES 
lIBMRr 

UC DAVIS 



CONTOUR INTERVAL 50' 



SCALE 

500 



lOOOft. 



Note: Refer to Plate I for gravity and ground magnetic 
profile X-Y and aeromagnetic and gravity profile 
R-S. 




7900 >— 



Btxiis ..... 



Mono 

Fault 



Queen Bee Hill 








I 

Sugorloaf 



Tsdi 



Tst 



Tsd (A) 



Tmd 



9000 



8600 



8400 



8200 



8000 



7800 



8000 



Bodie 



Moyle 



8800 — 



8400 — 



8200 — 




8000 — 



7800 I— 



^^ 




9000 



8800 



8600 IJ 



8400 



8200 m 



8000 



-■ 7800 



8800 I- 



8600 - 



8200 — 



8000 



7800 



Moyle 
Footwall 
Fault 
Standard Hill Standard 

New 
Shaft 



7400 





F .■7 projected 



H 




8800 



8600 



8400 



8200 



8000 



7800 



7600 



— ' 7400 



8000 



7800 



7600 



LEGEND 



GEOLOGIC EXPLANATION 



E^ 



Qal 



Os 



Tpd 



Tp» 



Tsdi 



Tsf 



i/ 



ye 



Mill tailings 

Plocered area 

Alluvium 

Slope Wosh 

Dactte flows 

Tuff breccio 

Doctte flows and plugs 

Tuff breccio; (G) groy, (B) brown 

Docile plugs 

Docile composite flow; (A) hornblende-rich, 
(B) biotrte-rich 

Tuff breccio, Includes vltric zones (WT) 

Silicic alteration 

Potossic alteration 

Argillic alteration 

Propylitic alteration 

Incline vein series, various veins 

Incline vein series, main Standard 

Burgess vein series 

Fortune vem 



GEOLOGIC SYMBOLS 






Contoct; dashed wh«re probable, queried where uncertain. 



Fauiti dashed where uncertain, dotted where concealed. 
Bor and bell on downthrown block. 



Vein; showing strike and dip, dashed where uncertain. 

strike and dip of bedding. 

Strike and dip of flow bonding. 

Strike of vertical flow bonding. 

Strike and dip of ioints. 

General direction of dip. 

Specimen locality of rock sampled for K-Ar age dating. 

GRAVITY EXPLANATION 

Gravity Station 



Contour Intervol: I.Omilllgals 
Reduction density : 2 50g/cm' 



Axis of positive onomaly trend 

MAGNETIC EXPLANATION 

Magnetometer station 

Contour Intervol: 200 gammas 
Arbitrary datum 



DRAFTING AND LAYOUT BY CA ALLEN 



DIVISION OF MINES AND GEOLOGY 
JAMES F DAVIS, STATE GEOLOGIST 








»^»»-, 



4. Tioga Mine 



5. Con Pacific Mine 




STATE OF CALIFORNIA - GEORGE DEUKMEJIAN, GOVERNOR 

THE RESOURCES AGENCY - CORDON K, VAN VLECK, SECRETARY FOR RESOURCES 

DEPARTMENT OF CONSERVATION - RANDALL M- WARD, DIRECTOR 






Belvedere Mine 



-.vr^^-jjir-r^- v^: 



7. South Bulwer Hoisting Works 




8. Jupiter Hoisting Works 



5S0C 





jwrfv. 



ng Works 



9. Dudley Hoisting Works 



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BULLETIN 206 
PLATE 3 



-■*f»fv. 



fHYSIMl SCIENCES 

new ( 

UC OAVIS 



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10. Defiance Hoisting Works 




» 







11. Booker Mine 



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nDli-^^ 




1. Syndicate Mine 





REFERENCES. 


1 


STANDAQD-BUUNER MILL. 


2 


MOUTH Of BULWER TUNNEL. 


3 


OeiBINiL SUMMIT MINE. 


il 


BODIE BLUFF MINE 


5 


BECHTEL MINE. 


6 


STANDARD MINE 


7 


CON. PACIFIC MINE 


a 


BELVIDERE MINE 


9 


eODIE MINE . 


10 


STANDARD MILL . 


II 


SOUTH BULWER MINE 


12 


MONO MINE 


13 


CHAMPION MINE 


14 GOODSHAW MINE. 




ie4^&^^ 





GENERAL VIEW OF BODIE MINING DISTRICT 

Showing the Western Slope of the Maim Range from North to South 

1880 




cas- NO.'t 



SCALE 



500 



1000 ft. 




CLAIM MAP 

BODIE MINING DISTRICT 
Mono County, California 



Surveyed and compiled 
by 

D.W. ORMSBEE - G.E. 

January, 1931 

Contour Interval: 50ft. 



rlK^*- 



-i^'-se 



:*Si. 



12. University and Maryland Mines 




13. Queen Bee Mine 



;>^^2.V 




26 



'tJS^i^.tL^ 



_iSi«i» 




^f-'swiMStosii^afei-- 



FROM ORIGINAL ILLUSTRATION BY EDWARD EYS£N 



REFERENCES, 

15 GIPSV QUEEN MINE 

16 SOUTH BODIE MINE. 

17 ADDENDA MINE 

18 SOUTH STAND Ago MINE 

19 OHO MINE 

20 SILVEH HILL TUNMEL. 
2i NOONDAY MINE 

22 NOONDAY MILL. . 

23 S PAUL DINS MILL . 

24 SPAULDING MINE 

25 BOOHEH MINE 

26 UNIVERSITY MINE 
Zl MARYLAND MINE 

28 BOSTON CON_ MINE. 

29 HING BEE MINE 




Drafting and layout by C.A Allen 



DIVISION OF MINES AND GEOLOGY 
JAMES F. DAVIS, STATE GEOLOGIST 




STATE OF CALIFORNIA - GEORGE DEUKMEJIAN, GOVERNOR 

THE RESOURCES AGENCY - GORDON K. VAN VLECK, SECRETARY FOR RESOURCES 

DEPARTMENT OF CONSERVATION - RANDALL M. WARD, DIRECTOR 




to 20C= 



BULLETIN 206 
PLATE 4 





i 




^'MiillMiimiiiiu^s 



^"^D'CATOR 



NEW STANDARD TUNNEL 




BULWER TUNNEL PORTAL 



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! 

BODIE B^LUFF - 



Mine Workings 
of the 

STANDARD HILL 



AREA 



/ 



BODIE MINING DISTRICT 

Mono Countj, California 

Revised by Charles W. Chesterman 



Scale 



50 100 



200 



300 



400 



500 



600 FEET 

55! 




GRAPHICS BY ROBERT A, SWITZER, 1979 



DIVISION OF MINES AND GEOLOGY 

JAMES F DAVIS, STATE GEOLOGfST 



STATE OF CALIFORNIA - GEORG 
THE RESOURCES AGENCY - GORDON K VAN 

DEPARTMENT OF CONSERVATION - 




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Mine Workings 
of the 

SOUTHERN MINES AREA 

BODIE MINING DISTRICT 

Mono County, California 

Compiled by Charles W. Chesterman 
Scale 

° ^° '?° 200 300 400 500 600 TOO 800 900 1000 FEET 



fL 



^^^/, 






I I I 



I I I I 




- GEORGE DEUKMEJIAN, GOVERNOR 

N K VAN VLECK, SECRETARY FOR RESOURCES 

VATION - RANDALL M WARD, PmECTOR^ ^__ 



BULLETIN 206 
PLATE 5 



PHVSICAL SCIENCES 
IIBRIRV 

UC DAVIS 



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GRAPHICS BY WOBERT A SWITZER, 1979 



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