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

PHYSICAL SCIENCES
LIBRARY

- / UC DAVIS

GEOLOGY AND ORE DEPu^i i S

OF THE
BODIE MINING DISTRICT

MONO COUNTY, CALIFORNIA

....

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CAl-!F, 0€?»©S

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

Charles W. Chesterman

Rodger H. Chapman

and
Cliffton H. Gray, Jr.

DIVISION OF MINES AND GEOLOGY

1986

^-'^^JM^

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

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

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

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

1 71

085

150

1.21

1.40

062

053

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

004

007

009

O10

010

004

000

0.00

000

005

004

1 11

006

008

006

0000

100.00

10000

100.00

100 00

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

* 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-

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

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

CO,

ooo

006

009

001

Total

10000

100 00

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

..u

Rhyolite / ' Rhyodacite ' Loi.te \

\ \

•-.■■..■:•. VA

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

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

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

301

230

H,0

1.50

160

1.50

130

083

TO,

0.73

0.62

064

068

088

0.34

0.40

047

034

MnO

0.07

0.21

0.02

008

014

ZrO,

0.00

000

CO,

0.00

000

Total

100 00

10000

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

• * 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

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

East
Dipping

/ °

/ o
/ °

* ctoO o\

o o

\ o

(P o

\ °

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

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

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 —

U II 11 •

// // // '

•

1 1 // / ""

r-"

•^

II 1 II 1 —

•
a.

/// ''

//I

^Lo^

1 ^

Burgais \

/ /I

Senas (

•

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-

CALIFORNIA DIVISION OF MINES AND GEOLOGY

Bull 206

Bodle New Shaft

Ml"

III

-^ III

g U

«, t»z--

;iU206' Lev

Burges

LEGEND

^^5?l -

r.-^^ptii

yfifi^ Fortuno Slopes

i:XI308' Lev.

;,'i«;

Faulting Veint

■to

-■I'-f.

Wall Rock

~iir""

432' nCi
III *

^^i

1 460' Le/'v

■1

k k

462

" Lev^ll^^^'.

-;•..

«> 2

(5 ^3

536' Lev,-

AT^

^^■:.."t

* v-^

554'

Lev^

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

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

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.

Sillclfi«d (Andesl»«) doelfe «'tm^(P

ill

(Andesite) Oacitt ^ S^ ^ f' Ui

+ttJ

-r (^

c — c

Crossing illl ''^'- t^vfflt'

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

' I ''

/ -'' !^^^i *

v/ •

li^r'

>7 y

\^^

^\^

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-

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

000O4 OKI

aoH

ExtrutfV* rodisolVi*
BodNHMHM

•ndmlt

(Mew

bftuN

mKMOIuII

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

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

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

J2i.2J9

3J9

J1HJ9

341

3 4}}«9

760

3 63-7 94

37»

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

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-

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

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

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

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

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

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

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

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

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

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

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

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*

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

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,
California: Geological Society of America (abstroctj, 64th Annual Meet-
ing, Cordilleran Section, Tucson, Arizona, p. 30.

Al-Rowi, Y.T., 1969, Cenozoic history of the northern port of Mono Basin.
California and Nevada, Ph.D. thesis. University of Califomio. Berieley.
163 p.

Anderson, C.L., 1880, Mop of the Bodie mining district. Mono County, Cali-
fornia: Published and illustrated by Edward Eysen, San Froncisco, Califor-
nia.

Atwood, M.. 1879, Wall Rocks of the Bodie auriferous lodes: Mining and
Scientific Press, Son Francisco, California, v. 38, r>o. 11 (Mofch 15,
1879), p. 169.

Billeb, E.W., 1968. Mining camp days: Howell-North Books. Berkeley, Coli-
fornio, 229 p.

Bloke, W P., 1862, in Complete guide to Mono County mines, by Joseph
Wosson: Joseph Wosson (1880), p 17

Browne, J.R., 1864, in Complete guide to Mono County mines, by Joseph
Wosson: Joseph Wosson (1880), p. 17 18.

Browne, JR., 1865, A trip to Bodie Bluff and the Dead Sea of the west:
Harpers New Monthly Magazine, v. 31 (June to November, 18651, p.
274 284.

Brown. R.G.. 1907. The vein system of the Stondard mine. Bodie. Colifomio:
Trans. AIME. v. 38. p. 343 357.

Cain. EM., 1956, The story of Bodie: Fearon Publishers. Son Francisco. 196

P
Colhoun, M., 1967, Pioneers of Mono Basin: Robert C. Calhoun, 172 p
Chopmon, R.H., 1966, The Colifomio Division of Mines and Geology gravity

bose station network: California Division of Mines and Geology Speciol

Report 90, 39 p.

1986

GEOLOGY AND ORE DEPOSITS OF THE BODIE MINING DISTRICT

Chestermon, C.W., and Groy, C.H., Jr., 1966, Geology and itructure of the
Mono Bosin, Mono Counfy, Colifornio: Guidebook olong the enstcentrcl
front of the Sierra Nevodo: Geologicol Society Socromento Annual Field
Trip )966, p. 11 18.

Chestermon, C.W., 1968, Volconic geology of the Bodie Hillj, Mono County,
Colifornio: in Studies m volconology, Geological Society America Mem-
oir 116, p. 45-68.

Chestermon. C W , and Groy. C.H., Jr., 1975, Geology of the Bodie 15
minute quodrongle. Mono Courity. Colifomio: Colifornio Division of
Mines ond Geology Map Sheet 21.

Eokle, AS. and McLoughlin, R.P , 1917, Mono County, 15th Annuol Report
State Mineralogist, p. 143-160

Gilbert, C.M., Chnstensen. M.N., AlRowi, Y T . ond Lojoie, K.R , 1968, Struc
turol and volcanic history of Mono Bosin, Colifornio-Nevodo, in Studies
in volconology. Geologicol Society of America Memoir 116, p. 275-329.

Hakes, OF,, 1902, Mining lowi of Bodie mining district: Bodie Miner Index.
Bodie, Californio. 48 p.

Johnson, Russ and Anne, 1 967, The ghost town of Bodie: Cholfant Press, Inc.,
Bishop, California. 119 p.

Kleinhompl, F.J., Davis, W.E., Silbermon, M.L., Chestermon, C.W., Chopmon,
R.H., and Groy. C.H , Jr., 1975, Aeromognetic ond limited gravity studies
ond generalized geology of the Bodie Hills Region, Nevada ond Colifor-
nio: U.S. Geological Survey Bulletin 1384, 38 p.

Koenig, J.B., 1963, Geologic Mop of California, Olaf P. Jenkins edition.
Walker Lake Sheet: California Division of Mines ond Geology, scole
1:250,000.

Loose, W., 1971, Bodie Bonanza: Exposition Press, Jericho. New York, 246

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

McLaughlin, R P., 1907. Geology of the Bodie district: Mining ond Scientific

Press, Son Francisco. Colifornio, v, 110. p. 795.
Oliver, H.W., Griscom, A., Robbins, S.L.. and Honno, W.F., 1969, U.S.

Geologicol Survey grovity doto in California, port IV: U.S. Geological

Survey Interogency Report. 53 p.

O'Neil, J R , Silbermon, ML., Fobbi, B.P., ond Chestermon, C.W., 1973,

Stoble isotope ond chemical relations during mineralization in the Bodie

mining district. Mono County, Colifornio: Economic Geology, v. 68, p.

765-784.
Pakiser, L.C., Kone, M,F., ond Jackson, W.H., 1964, Structurol geology and

volconism of Owens Volley region. Colifornia — o geophysical study: U.S.

Geological Survey Professionol Paper 438, 68 p
Plouff, D., 1966, Digitol terrain corrections based on geographic coordinotes

[abstract): Geophysics, v. 31, no. 6, p. 1208.
Silbermon, ML., ond Chestermon, C.W., 1972, K Ar age of volconism and

minerolizotion. Bodie mining district and Bodie Hills volcanic field. Mono

County, Colifornia: Isochron West, no. 3, p. 13-22.
Silbermon, ML., Chestermon, C.W., Kleinhompl, F J . ond Groy, CM., Jr..

1972, K-Ar ages of volconic rocks and gold-beoring quartz odulono veins

in the Bodie mining district. Mono County, Colifornio: Economic Geology,

V. 67, p 597 604.

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

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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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BULLETIN 206
PLATE 2

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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

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

8800

8600

8400

8200

8000

7800

7600

— ' 7400

8000

7800

7600

LEGEND

GEOLOGIC EXPLANATION

Qal

Tpd

Tp»

Tsdi

Tsf

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

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7. South Bulwer Hoisting Works

8. Jupiter Hoisting Works

5S0C

jwrfv.

ng Works

9. Dudley Hoisting Works

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830t

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IN.

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BULLETIN 206
PLATE 3

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fHYSIMl SCIENCES

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UC OAVIS

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10. Defiance Hoisting Works

11. Booker Mine

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1. Syndicate Mine

REFERENCES.

STANDAQD-BUUNER MILL.

MOUTH Of BULWER TUNNEL.

OeiBINiL SUMMIT MINE.

BODIE BLUFF MINE

BECHTEL MINE.

STANDARD MINE

CON. PACIFIC MINE

BELVIDERE MINE

eODIE MINE .

STANDARD MILL .

SOUTH BULWER MINE

MONO MINE

CHAMPION MINE

14 GOODSHAW MINE.

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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

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_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

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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

^^^/,

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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