U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Report 2015–5012

Gold-Silver Mining Districts, Alteration Zones, and 

Paleolandforms in the Miocene Bodie Hills Volcanic Field, 

California and Nevada
Cover. Photograph showing ore bins at head of aerial tramway from the Sarita Mine to the Masonic mill, 

Masonic Mining District.
Gold-Silver Mining Districts, Alteration Zones, 

and Paleolandforms in the Miocene Bodie Hills 

Volcanic Field, California and Nevada

By Peter G. Vikre, David A. John, Edward A. du Bray, and Robert J. Fleck

Scientific Investigations Report 2015–5012

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

SALLY JEWELL, Secretary

U.S. Geological Survey

Suzette M. Kimball, Acting Director

U.S. Geological Survey, Reston, Virginia: 2015

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Suggested citation:

Vikre, P.G., John, D.A., du Bray, E.A., and Fleck, R.J., 2015, Gold-silver mining districts, alteration zones, and 

paleolandforms in the Miocene Bodie Hills volcanic field, California and Nevada: U.S. Geological Survey Scientific 

Investigations Report 2015–5012, 160 p., http://dx.doi.org/10.3133/sir20155012.

ISSN 2328-0328 (online)
iii

Contents

Abstract...........................................................................................................................................................1

Introduction.....................................................................................................................................................3

Bodie Hills Volcanic Field ...........................................................................................................................11

Methods.........................................................................................................................................................12

Masonic Mining District .............................................................................................................................13

Location................................................................................................................................................13

History and Production ......................................................................................................................13

Stratigraphy .........................................................................................................................................13

Structure...............................................................................................................................................17

Forms of Gold-Silver-Copper Deposits............................................................................................17

Breccias and Vein Deposits in High-Angle, Subplanar Fault Zones .................................17

Mineral and Rock Compositions of Breccias and Vein Deposits ......................................18

Clastic and Hydrothermal Sedimentary Deposits ................................................................22

Interpretation of Clastic and Hydrothermal Sedimentary Deposits ..................................22

Mineral and Rock Compositions of Clastic and Hydrothermal 

Sedimentary Deposits .................................................................................................23

Other Minerals and Forms of Mineralization ........................................................................25

Wall-Rock Alteration ..........................................................................................................................25

Sulfur Isotope Compositions and Equilibrium Temperatures .............................................27

Aster Imagery.............................................................................................................................28

Short Wave Infrared (SWIR) Spectra.....................................................................................28

Host Rock and Alteration Mineral Ages .........................................................................................28

Red Wash-East Walker River Alteration Zone........................................................................................28

Location................................................................................................................................................28

Definition ..............................................................................................................................................28

History and Production ......................................................................................................................30

Stratigraphy .........................................................................................................................................30

Structure...............................................................................................................................................30

Hydrothermal Alteration ....................................................................................................................30

Minor Elements in Rocks..........................................................................................................31

Sulfur Isotope Composition......................................................................................................31

ASTER Imagery ..........................................................................................................................31

SWIR Spectra.............................................................................................................................31

Hydrothermal Mineral Ages..............................................................................................................31

East Brawley Peak Alteration Zone..........................................................................................................33

Location................................................................................................................................................33

Definition ..............................................................................................................................................33

History and Production ......................................................................................................................33

Stratigraphy .........................................................................................................................................33

Structure...............................................................................................................................................33
iv

Hydrothermal Alteration ....................................................................................................................35

Minor Elements in Rocks..........................................................................................................35

ASTER Imagery ..........................................................................................................................35

SWIR Spectra.............................................................................................................................35

Fluid Inclusion Microthermometry and Composition....................................................................35

Hydrothermal Mineral Ages..............................................................................................................36

Sawtooth Ridge Alteration Zone ...............................................................................................................36

Location................................................................................................................................................36

Definition ..............................................................................................................................................36

History and Production ......................................................................................................................36

Stratigraphy .........................................................................................................................................36

Structure...............................................................................................................................................36

Hydrothermal Alteration ....................................................................................................................36

Sulfur Isotope Composition......................................................................................................38

ASTER Imagery ..........................................................................................................................38

SWIR Spectra.............................................................................................................................38

Hydrothermal Mineral Age................................................................................................................38

Aurora Canyon Alteration Zone.................................................................................................................38

Location................................................................................................................................................38

Definition ..............................................................................................................................................38

History and Production ......................................................................................................................38

Stratigraphy .........................................................................................................................................38

Structure...............................................................................................................................................40

Hydrothermal Alteration ....................................................................................................................40

Minor Elements in Rocks..........................................................................................................40

ASTER Imagery ..........................................................................................................................40

SWIR Spectra.............................................................................................................................40

Hydrothermal Mineral Age................................................................................................................40

Potato Peak Alteration Zone......................................................................................................................41

Location................................................................................................................................................41

Definition ..............................................................................................................................................41

History and Production ......................................................................................................................41

Stratigraphy .........................................................................................................................................41

Structure...............................................................................................................................................41

Hydrothermal Alteration ....................................................................................................................41

Minor Elements in Rocks..........................................................................................................41

Sulfur Isotope Compositions....................................................................................................43

ASTER Imagery ..........................................................................................................................43

SWIR Spectra.............................................................................................................................43

Hydrothermal Mineral Age................................................................................................................43

Aurora Mining District.................................................................................................................................43

Location................................................................................................................................................43

History and Production ......................................................................................................................43

Stratigraphy .........................................................................................................................................46

Structure...............................................................................................................................................46
v

Forms of Gold-Silver Mineralization ................................................................................................47

Veins and Vein Zones ................................................................................................................47

Ore Bodies...................................................................................................................................48

Juniata-Prospectus Vein Minerals .........................................................................................49

Mineral Compositions in Silver Hill and Middle Hill Veins ..................................................50

Minor Elements in Rocks..........................................................................................................50

Fluid Inclusion Microthermometry and Compositions.........................................................50

Sulfur Isotope Compositions of Vein Minerals......................................................................53

Wall-Rock Alteration ..........................................................................................................................54

ASTER Imagery ..........................................................................................................................54

SWIR Spectra.............................................................................................................................54

Hydrothermal Mineral Ages..............................................................................................................54

Four Corners Alteration Zone.....................................................................................................................54

Location................................................................................................................................................54

Definition ..............................................................................................................................................54

History and Production ......................................................................................................................56

Stratigraphy .........................................................................................................................................56

Structure...............................................................................................................................................56

Hydrothermal Alteration ....................................................................................................................56

ASTER Imagery ..........................................................................................................................56

SWIR Spectra.............................................................................................................................56

Hydrothermal Mineral Ages..............................................................................................................56

Paramount-Bald Peak Alteration Zone ....................................................................................................56

Location................................................................................................................................................56

Definition ..............................................................................................................................................56

History and Production ......................................................................................................................60

Stratigraphy .........................................................................................................................................60

Structure...............................................................................................................................................60

Hydrothermal Alteration ....................................................................................................................64

Paramount Mine Area...............................................................................................................64

Minor Elements in Rocks..........................................................................................................64

Atastra Creek Area....................................................................................................................65

Bald Peak Area...........................................................................................................................65

Sulfur Isotope Compositions....................................................................................................69

ASTER Imagery ..........................................................................................................................69

SWIR Spectra.............................................................................................................................69

Hydrothermal Mineral Ages..............................................................................................................69

Cinnabar Canyon-US 395 Alteration Zone ...............................................................................................70

Location................................................................................................................................................70

Definition ..............................................................................................................................................70

History and Production ......................................................................................................................70

Stratigraphy .........................................................................................................................................70

Structure...............................................................................................................................................70

Forms of Mercury and Sulfur Mineralization .................................................................................71
vi

Hydrothermal Alteration ....................................................................................................................71

Minor Elements in Rocks..........................................................................................................75

Sulfur Isotope Compositions....................................................................................................76

ASTER Imagery ..........................................................................................................................76

SWIR Spectra.............................................................................................................................76

XRD Mineralogy .........................................................................................................................76

Hydrothermal Mineral Ages..............................................................................................................76

Bodie Mining District...................................................................................................................................77

Location................................................................................................................................................77

History and Production ......................................................................................................................77

Stratigraphy .........................................................................................................................................80

Structure...............................................................................................................................................81

Forms of Silver-Gold Deposits ..........................................................................................................81

Incline Series Veins...................................................................................................................84

Burgess Series Veins ................................................................................................................88

Silver Hill Series Veins ..............................................................................................................90

Veins On and Near Queen Bee Hill .........................................................................................91

Wall-Rock Alteration ..........................................................................................................................91

Absolute and Relative Vein and Sinter Ages.........................................................................95

Minor Elements in Veins and Wall Rocks ..............................................................................95

Fluid Inclusion Microthermometry..........................................................................................97

Oxygen and Hydrogen Isotope Compositions of Vein Minerals and Fluid 

Inclusion Water ............................................................................................................97

Sulfur Isotope Compositions of Vein Minerals......................................................................97

ASTER Imagery ..........................................................................................................................98

SWIR Spectra; XRD Analyses..................................................................................................98

Spring Peak Sinter.......................................................................................................................................98

Location................................................................................................................................................98

Definition ..............................................................................................................................................98

History and Production ......................................................................................................................98

Stratigraphy .........................................................................................................................................98

Structure.............................................................................................................................................100

Hydrothermal Alteration ..................................................................................................................100

Hydrothermal Mineral Ages............................................................................................................100

Evolution of Landforms During Assembly and Alteration of the Miocene Bodie Hills 

Volcanic Field.......................................................................................................................100

Aldrich Station Flora and Fossils in the Bodie Hills ...........................................................100

Eureka Valley Tuff in the Bodie Hills .....................................................................................106

Landforms in Mining Districts and Alteration Zones .........................................................106

Synthesis [Masonic Mining District] ....................................................................................107

Synthesis [Aurora Mining District] .......................................................................................109

Synthesis [Bodie Mining District] .........................................................................................110

Summary......................................................................................................................................................114

Acknowledgments.....................................................................................................................................114

References Cited........................................................................................................................................115

Appendixes .................................................................................................................................................121
vii

Figures

1. Map showing locations of mining districts and alteration zones in the Bodie Hills, 

California and Nevada .................................................................................................................4

2. Geologic map of the southwestern part of the Masonic Mining District, 

Mono County, California, and Lyon and Mineral Counties, Nevada...................................14

3. Geologic map of the northeastern part of the Masonic Mining District, 

Mono County, California, and Mineral County, Nevada .......................................................15

4. Images of volcaniclastic deposits in the Red Wash-East Walker River 

alteration zone and Masonic Mining District.........................................................................16

5. Images of mineralized fault breccias and veins in the Masonic Mining District.............19

6. Secondary electron images of fault breccia, Masonic Mining District ............................20

7. Secondary electron images of fault breccia, Masonic Mining District ............................21

8. Secondary electron image of quartz+alunite+sulfide vein in granodiorite, 

Masonic Mining District............................................................................................................22

9. Image of a dump sample from the Masonic Mining District, Sarita Mine........................23

10. Images of dump samples from the Masonic Mining District, Sarita Mine .......................24

11. Images of dump samples from the Masonic Mining District, Sarita Mine .......................25

12. Secondary electron images of minerals in very fine-grained brown quartz beds 

from the Sarita Mine open cut, Masonic Mining District ....................................................26

13. Image of a dump sample from the Masonic Mining District, Sarita Mine........................27

14. Geologic map of the Red Wash-East Walker River alteration zone, Lyon and 

Mineral Counties, Nevada, and Mono County, California....................................................29

15. Advanced Spaceborne Thermal Emission and Reflection Radiometer imagery 

of the Red Wash-East Walker River alteration zone.............................................................32

16. Geologic map of the East Brawley Peak alteration zone, Mineral County, Nevada, 

and Mono County, California.....................................................................................................34

17. Geologic map of the Sawtooth Ridge alteration zone, Mineral County, Nevada, 

and image of a remnant bowl-shaped thermal vent.............................................................37

18. Geologic map of the Aurora Canyon alteration zone, Mono County, California, 

and image showing a concentrically exfoliated rhyolite dome..........................................39

19. Geologic map of the Potato Peak alteration zone, Mono County, California, and 

image showing landslides developed on altered volcaniclastic strata ............................42

20. Geologic map of the Aurora Mining District, Mineral County, Nevada.............................44

21. Image of a sample from the Aurora Mining District .............................................................49

22. Secondary electron images of an archival vein specimen from the Crocket Mine 

on Last Chance Hill, Aurora Mining District...........................................................................51

23. Secondary electron images of an archival vein specimen from the Antelope Mine, 

Silver Hill, Aurora Mining District ............................................................................................52

24. Secondary electron images of an archival vein specimen from the Antelope Mine, 

Silver Hill, Aurora Mining District ............................................................................................53

25. Geologic map of the Four Corners alteration zone, Mono County, California ..................55

26. Images of hydrothermal features, Four Corners alteration zone........................................57

27. Geologic map of the Paramount-Bald Peak alteration zone, Mono County, California, 

and Mineral County, Nevada, showing sinters, sinter groups, and prospects ................58

28. Geologic map of the Paramount Hg Mine area, Mono County, California, and 

image showing unoriented, multisized blocks of terrace sinter.........................................61
viii

29. Images of Paramount-Bald Peak alteration zone .................................................................62

30. Images of hydrothermal features in the Paramount-Bald Peak alteration zone .............63

31. Image showing oriented consecutive sections, graphs showing relative element 

concentrations, and bulk sample element concentrations of sinter from a dismembered terrace at the western base of Paramount Mine hill, Paramount-Bald Peak 

alteration zone.............................................................................................................................66

32. Image showing oriented consecutive sections, graphs showing relative element 

concentrations, and bulk sample element concentrations of a chalcedonic quartz 

vein exposed at the upper adit of the Paramount Mine, Paramount-Bald Peak 

alteration zone.............................................................................................................................67

33. Image showing oriented consecutive sections, graphs showing relative element 

concentrations, and bulk sample concentrations of sinter from sinter terrace on 

Atastra Creek, Paramount-Bald Peak alteration zone .........................................................68

34. Geologic map and schematic stratigraphic section of the Cinnabar Canyon-US 395 

alteration zone, Mono County, California................................................................................72

35. Images showing volcaniclastic deposits from the Cinnabar Canyon-US 395 

alteration zone.............................................................................................................................74

36. Cross section through the Cinnabar Canyon elemental sulfur resource, 

Cinnabar Canyon-US 395 alteration zone, Mono County, California..................................75

37. Geologic map of the Bodie Mining District, Mono County, California ...............................78

38. Geologic cross sections of the Bodie Mining District..........................................................79

39. Images of veins in the Bodie Mining District.........................................................................82

40. Secondary and backscatter electron images of samples representative of 

Incline series veins on Bodie Bluff, and of vein samples from the Noonday Mine 

near Silver Hill, Bodie Mining District.....................................................................................87

41. Secondary electron images of samples representative of Burgess series veins 

on Standard Hill, Bodie Mining District...................................................................................89

42. Secondary electron images of samples representative of Silver Hill series veins 

on and near Oro Mine dump, Silver Hill, Bodie Mining District..........................................91

43. Secondary electron images of samples representative of Silver Hill series veins 

on and near Addenda Mine, Silver Hill, Bodie Mining District ...........................................92

44. Secondary electron images of samples representative of Silver Hill series veins 

on and near Red Cloud mine dump, Silver Hill, Bodie Mining District...............................93

45. Secondary electron images of samples representative of Silver Hill series veins 

on and near Red Cloud, Contention, and Maybelle Mine dumps, Silver Hill, Bodie 

Mining District.............................................................................................................................94

46. Image showing oriented consecutive sections, graphs showing relative element 

concentrations, and bulk sample element concentrations of sinter from Bodie Bluff 

summit, Bodie Mining District ..................................................................................................96

47. Graph of Ag, As, Sr concentrations versus Au, Sb, Rb concentrations in sinter 

from the dismembered sinter terrace, sinter fragments in volcaniclastic deposits, 

and Incline series veins, Bodie Mining District, Bodie Bluff summit.................................97

48. Geologic map of the Spring Peak sinter, Mineral County, Nevada, and image 

showing nearly intact sinter beds from the northern margin of the terrace....................99

49. Image of sample, and graphs showing relative element concentrations and bulk 

sample element concentrations of Spring Peak sinter from the Hg prospect in the 

sinter terrace, Spring Peak alteration zone .........................................................................101

50. Image showing sample, and graphs showing relative element concentrations and 

bulk sample element concentrations of Spring Peak sinter from the Hg prospect in 

the sinter terrace, Spring Peak alteration zone...................................................................102
ix

51. Image showing oriented consecutive sections, and graphs showing relative 

element concentrations and bulk sample element concentrations of sinter from 

the northern edge of the Spring Peak sinter terrace..........................................................103

52. Maps showing assembly of the Miocene Bodie Hills volcanic field, California 

and Nevada, from 15 to 8 Ma based on volcanic stratigraphy, mineral deposits, 

alteration zones, and geochronology....................................................................................104

Tables

1. 40Ar/39Ar dates (Ma) of igneous and hydrothermal minerals in mining districts 

and alteration zones of the Bodie Hills, determined by incremental heating 

and laser fusion.............................................................................................................................5

2. Sulfur isotope compositions of sulfide and sulfate minerals and sulfur from 

mining districts and alteration zones, and calculated sulfur isotope equilibrium 

temperatures .................................................................................................................................9

3. Reporting limits for element concentrations in tables 1-1 through 1-12 ...........................11

4. Characteristics of Incline, Burgess, and Silver Hill series veins in the Bodie 

Mining District.............................................................................................................................83

5. Gold and silver production and precious metal grades for mines and veins in the 

Bodie Mining District from 1875 to 1942, and relative value of gold and silver 

in bullion from 1878 to 1881 .......................................................................................................85

6. Vein attitudes and widths derived from surface mapping and published 

descriptions .................................................................................................................................86

1-1. Minor element concentrations in rock samples from the Masonic Mining District .....122

1-2. Minor element concentrations in rock samples from the Red Wash-East Walker 

River alteration zone ................................................................................................................125

1-3. Minor element concentrations in rock samples from the East Brawley Peak 

alteration zone...........................................................................................................................128

1-4. Minor element concentrations in rock samples from the Sawtooth Ridge 

alteration zone...........................................................................................................................129

1-5. Minor element concentrations in rock samples from the Aurora Canyon 

alteration zone...........................................................................................................................131

1-6. Minor element concentrations in rock samples from the Potato Peak 

alteration zone...........................................................................................................................132

1-7. Minor element concentrations in rock samples from the Aurora Mining District.........133

1-8. Minor element concentrations in rock samples from the Four Corners 

alteration zone...........................................................................................................................135

1-9. Minor element concentrations in rock samples from the Paramount-Bald Peak 

alteration zone...........................................................................................................................137

1-10. Minor element concentrations in rock samples from the Cinnabar Canyon-US 395 

alteration zone...........................................................................................................................145

1-11. Minor element concentrations in rock samples from the Bodie Mining District...........149

1-12. Minor element concentrations in rock samples of Spring Peak sinter...........................159
x

Conversion Factors

Inch/Pound to International System of Units

Multiply By To obtain

Length

inch (in.) 2.54 centimeter (cm)

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

Area

square mile (mi2

) 2.590 square kilometer (km2) 

Mass

ounce, troy (oz) 31.10 gram (g) 

ton, short (2,000 lb) 0.9072 tonne, metric 

International System of Units to Inch/Pound

Multiply By To obtain

Length

centimeter (cm) 0.3937 inch (in.)

millimeter (mm) 0.03937 inch (in.)

micron (μm) 0.00003937 inch (in.)

meter (m) 3.281 foot (ft) 

kilometer (km) 0.6214 mile (mi)

Area

square kilometer (km2

) 0.3861 square mile (mi2)

Mass

tonne, metric (Mt) 1.1023 ton, short (2000 lb)
xi

Acronyms and Abbreviations Used

AA cold-vapor and hydride generation atomic 

absorption

ASTER Advanced Spaceborne Thermal Emission 

and Reflection Radiometer

FA-ICPMS fire assay-inductively coupled plasma-mass 

spectrometry

ICP-AES-MS inductively coupled plasma-atomic emission 

spectrometry-mass spectrometry

LA ICP-MS laser ablation inductively coupled plasmamass spectrometry

Ma million years before present

Moz million ounces

SEM scanning electron microscopy

SWIR short wave infrared radiation

USGS U.S. Geological Survey

XRD x-ray diffraction
xii

Ag silver

Al aluminum

As arsenic

Au gold

Ba barium

Be beryllium

Bi bismuth

C carbon

Ca calcium

Cd cadmium

Ce cerium

Co cobalt

Cr chromium

Cs cesium

Cu copper

Fe iron

Ga gallium

Hg mercury

In indium

K potassium

La lanthanum

Li lithium

Mg magnesium

Mn manganese

Mo molybdenum

Na sodium

Nb niobium

Ni nickel

O oxygen

P phosphorus

Pb lead

Rb rubidium

S sulfur

Sb antimony

Sc scandium

Se selenium

Sn tin

Sr strontium

Te tellurium

Th thorium

Ti titanium

Tl thallium

U uranium

V vanadium

W tungsten

Y yttrium

Zn zinc

Chemical Symbols Used
Abstract

The middle-late Miocene Bodie Hills volcanic field, 

Mono County, California, and Mineral and Lyon Counties, 

Nevada, contains three precious metal mining districts, 

with combined production of ~3.4 million ounces (Moz) 

gold (Au) and ~28 Moz silver (Ag), and nine variably sized 

alteration zones. Minor amounts of mercury (Hg) have been 

produced from three alteration zones; a significant sulfur 

resource has been identified in one alteration zone. The ~40 by 

~30 kilometer (km) volcanic field is made up of coalescing, 

15–6 Ma, subduction-related, trachyandesite stratovolcanoes, 

trachydacite and rhyolite lava domes, and related volcaniclastic deposits that cover an irregular erosional surface of 

Paleozoic and Mesozoic metavolcanic and metasedimentary 

rocks and Mesozoic granitic rocks of the Sierra Nevada 

batholith. Hydrothermal systems that formed precious metal 

deposits and most alteration zones were intermittently active 

during and soon after the development of trachyandesite 

stratovolcanoes and rhyolite flow-domes at 13.4–11 Ma, and 

following eruption of trachyandesite to rhyolite flows, domes, 

and associated volcaniclastic deposits at ~9–8 Ma.

In the Masonic Mining District, Au (0.056 Moz), Ag 

(0.04 Moz), and small amounts of copper (Cu) were produced 

from 0.075 million metric tons (Mt) of ore mostly during 

the period 1906–20. Deposits formed at ~13.4–13.3 Ma 

and 13.0 Ma, and comprise two styles of mineralization: 

(1) high-angle, fault breccia deposits in Mesozoic granitic 

rocks and 15–14 Ma trachyandesite flows; and (2) stratiform 

volcaniclastic and chemical sedimentary deposits in 15–14 Ma 

trachyandesite. Both types of deposits consist of quartz, 

enargite (and lesser luzonite), pyrite, small inclusions (tens of 

micrometers in size) and intergrowths of numerous Cu-As-SbFe-Bi-Au-Ag-S-Se-Te minerals including Au-rich electrum, 

alunite, kaolinite and dickite, pyrophyllite, and sericite. 

Fault breccia deposits are enclosed by meters-wide selvages 

comprised of quartz, alunite, pyrite, kaolinite and dickite, 

pyrophyllite, sericite, and montmorillonite.

In the Aurora Mining District, an estimated 1.91 Moz 

of Au and 21 Moz of Ag were recovered from ~3.9 Mt of 

vein ore, mostly during several periods of mining: 1860–64, 

1906–18, and 1988–98. The ~10.5 Ma vein system, in 

13.1–12.6 Ma trachyandesite of Aurora, is comprised of 

numerous north- to northeast-striking en echelon segments, 

which have a cumulative strike length of ~7.5 km. Veins 

are composed of fine-grained, layered to granular quartz, 

sulfide minerals, electrum, sericite, potassium feldspar 

(K-feldspar), and paragenetically late calcite. Quartz layers 

locally include finely dispersed pyrite, electrum, acanthite, 

naumannite, sphalerite, galena, polybasite, tetrahedrite, an 

Ag-Au-S mineral (~Ag4

AuS3), and clumps of these minerals 

(millimeters to centimeters in size). Trachyandesite wall 

rocks proximal to veins, vein zone septa, and internal breccia 

fragments have been altered to sericite, K-feldspar, and pyrite. 

Distal, pervasively altered trachyandesite contains variable 

proportions of chlorite, albite, calcite, and montmorillonite, 

and lesser fine-grained quartz, sericite, pyrite (and iron oxides 

after pyrite), and epidote.

In the Bodie Mining District, 1.46 Moz of Au and 

7.3 Moz of Ag were produced from ~1.5 Mt of vein ore, 

mostly during the period 1877–1913. Deposits comprise at 

least three types of N ± 30°-striking veins that formed from 

~8.9 to 8.1 Ma in ~9 Ma dacite of Silver Hill domes and flows. 

Incline series veins, the most productive vein type, consist of 

numerous layers (millimeters thick) of quartz ± adularia with 

electrum and Ag-S-Se minerals dispersed on some layers. 

Burgess series veins are composed of relatively coarse-grained 

and less distinctly layered quartz ± adularia, and contain 

as much as 5 volume percent electrum, Ag-S-Se minerals, 

pyrite, sphalerite, and galena. These vein types are enclosed 

by <1-meter-wide selvages of dacite altered to variable 

amounts of K-feldspar, quartz, sericite, and pyrite. Silver 

Hill series veins consist mostly of fault breccia cemented by 

quartz, adularia, sericite, calcite, and as much as 10 volume 

percent metallic minerals, predominantly sphalerite, galena, 

tetrahedrite, and chalcopyrite, and lesser pyrite, acanthite, 

electrum, bornite, hessite, and sylvanite. They are enclosed 

Gold-Silver Mining Districts, Alteration Zones, and 

Paleolandforms in the Miocene Bodie Hills Volcanic 

Field, California and Nevada

By Peter G. Vikre, David A. John, Edward A. du Bray, and Robert J. Fleck
2 Gold-Silver Mining Districts, Alteration Zones, and Paleolandforms in the Miocene Bodie Hills Volcanic Field

by selvages of dacite (meters wide) altered to quartz, pyrite, 

and sericite. Heterolithic volcaniclastic deposits fill a graben 

on Bodie Bluff, contain clasts of sinter at the highest exposed 

elevation (Bodie Bluff), and record the youngest volcanic and 

hydrothermal events in the district.

The areally extensive (>30 square kilometers [km2]) 

13.3 Ma Red Wash-East Walker River alteration zone, which 

formed simultaneously with the oldest Au-Ag-Cu deposits 

in the Masonic Mining District, and the large (~30 km2) 

~8.8–8.2 Ma Cinnabar Canyon-US 395 alteration zone, 

which contains a significant S° (native sulfur) resource 

(16.1 Mt @ 17.9 percent S) and a small Hg deposit, formed in 

sequences of permeable volcaniclastic rocks and subordinate 

15–8.9 Ma trachyandesite flows. The zones consist of resistant 

quartz ± alunite ± pyrite-dominant hydrothermal mineral 

assemblages enclosed by strata variably altered to kaolinite, 

pyrite, sericite, pyrophyllite, and montmorillonite. The large 

(~30 km2) Paramount-Bald Peak alteration zone mostly 

formed in a permeable sequence of rhyolite tuff, volcaniclastic 

strata, and lesser rhyolite (sedimentary rocks and tuff of 

Paramount) that accumulated in a northeast-trending basin 

at ~10.3–9.3 Ma. These strata have been variably leached 

and altered to silica minerals, montmorillonite, and lesser 

kaolinite, dickite, and pyrite, and include groups of intact 

and dismembered sinter terraces, one of which is associated 

with the intermittently mined (1878–1968) Hg vein deposit 

at the Paramount Mine. Smaller alteration zones, including 

the ~12 Ma East Brawley Peak (~7.7 km2), 11.1 Ma Sawtooth 

Ridge (~2 km2), 10.9 Ma Aurora Canyon (~8.1 km2), and 

10.8 Ma Potato Peak (~1.3 km2), formed in ~15–11.2 Ma trachyandesite, rhyolite, and volcaniclastic strata. Hydrothermal 

mineral assemblages in these zones are similar to those of the 

Red Wash-East Walker River and Cinnabar Canyon-US 395 

alteration zones. Small quantities of Hg (tens of flasks) were 

produced from the Cinnabar Canyon-US 395, Paramount-Bald 

Peak, and Potato Peak alteration zones, but no production is 

recorded from the other zones. The undated (~14–10 Ma) Four 

Corners alteration zone (< 0.02 km2) consists of brecciated 

trachyandesite of Masonic that has been cemented by quartz 

and pyrite (and iron oxides after pyrite) and contains local 

clastic and chemical sedimentary deposits. The partially 

dismembered and undated sinter terrace at Spring Peak 

(0.02 km2) lies on Cretaceous granitic and metamorphic rocks, 

and on altered volcaniclastic deposits. Slope detritus of these 

strata, adjacent to the terrace, include clasts of layered veins.

Based on volcanic stratigraphy, geochronology, remnant 

paleosurfaces, and paleopotentiometric surfaces in mining 

districts and alteration zones, present landforms in the Bodie 

Hills volcanic field reflect incremental construction of stratovolcanoes and large- to small-volume flow-domes, magmatic 

inflation, and fault displacements. In the northwestern part 

of the field, the extensive (~ 350 km2) 15–14 Ma Masonic 

volcanic center, consisting of trachyandesite flows, domes, 

and volcaniclastic deposits, was erupted on Mesozoic granitic 

and metamorphic rocks, and intruded by 13.5–13.4 Ma and 

12.9 Ma porphyritic trachyandesite. These intrusions closely 

correspond in age to the Au-Ag-Cu deposits in the Masonic 

district (13.4–13.3 Ma and 13 Ma) and to the areally extensive 

Red Wash-East Walker River alteration zone (13.3 Ma). 

Paleorelief among domes of the younger intrusions, domes of 

older trachyandesite, and prominences of Mesozoic rocks, was 

meters to tens of meters (tens to hundreds of feet).

In the eastern part of the volcanic field, the 13.1–12.6 Ma 

Aurora volcanic center was dominated by a prominent ridge of 

trachyandesite (~130 km2) flanked by lower-elevation flowdomes of trachyandesite and rhyolite. These large- and smallvolume volcanoes were emplaced on Mesozoic rocks. Parts of 

the volcanic center were altered at ~12 Ma (East Brawley Peak 

alteration zone), 11 Ma (Sawtooth Ridge alteration zone), 

and 10.5 Ma during formation of Au-Ag veins of the Aurora 

district. Paleorelief within the volcanic center was hundreds of 

meters (hundreds to >1,000 feet [ft]1) above ancestral Fletcher 

Valley to the north that was an established basin by 11 Ma.

From ~11–9.5 Ma, pre-Tertiary rocks in the central and 

southwestern parts of the field were mostly covered by large- to 

small-volume flows and domes of trachyandesite, rhyolite, and 

trachydacite. These flow-domes and older volcanic uplands 

shed detritus into the ~10.3–9.3 Ma Paramount basin, which 

was nearly simultaneously altered by hydrothermal systems 

that produced groups of sinter terraces and subjacent, locally 

Hg-mineralized veins (Paramount-Bald Peak alteration zone; 

Paramount Hg Mine). At 9.5–9.3 Ma, externally sourced Eureka 

Valley Tuff partly filled the drainages and depressions that had 

been incised into volcanic uplands in the western half of the 

volcanic field. The distribution of Eureka Valley Tuff remnants 

shows that paleorelief among volcanic and pre-Tertiary landforms was tens to hundreds of meters (hundreds of feet).

From ~10 to 8 Ma, large-volume stratovolcanoes and 

flow-dome fields, including trachydacite of Potato Peak, dacite 

of Silver Hill, trachyandesite and volcaniclastic deposits of 

Mount Biedeman, and trachyandesite of Willow Springs, were 

erupted in the southern part of the volcanic field. The volcaniclastic flow sequence exposed between Cinnabar Canyon 

and US 395 was pervasively altered and locally mineralized 

with Hg and S (Cinnabar Canyon-US 395 alteration zone), 

nearly simultaneously with the formation of multiple Au-Ag 

vein deposits in dacite flow-domes of the Bodie district at 

8.9–8.1 Ma.

The present elevation of Potato Peak (10,237 ft) is 

~1,100 ft higher than the highest elevation of Eureka Valley 

Tuff (9,150 ft) on Potato Peak, ~4,600 ft higher than the 

lowest elevation of Eureka Valley Tuff (5,600 ft) along the 

East Walker River, and ~4,200 ft higher than Fletcher Valley. 

Assuming a common Eureka Valley Tuff paleoelevation at 

9.3 Ma, these present elevation differences, and few significant 

faults in the southern part of the field, indicate that most present 

relief in the volcanic field reflects construction of 10–8 Ma 

large-volume volcanic centers, and related magmatic inflation. 

Relatively small increments of relief (tens to hundreds of 

1

Elevations are reported in feet for the purpose of comparing paleoelevations to present elevations, which are reported in feet on topographic maps..
Introduction 3

meters) have been added to northwestern and eastern parts 

of the field by displacement along east-west, and north- to 

northeast-trending normal faults in the Masonic and Aurora 

districts, and in the Paramount basin. Pliocene volcanic rocks 

of the Aurora volcanic field, which initially erupted at ~3.9 Ma, 

do not appear to be significantly offset by faults, implying that 

most fault displacement occurred between 9.3 and 3.9 Ma. 

Between 8 and 3.9 Ma, only a few small-volume, ~6–5 Ma 

rhyolite and dacite flow-domes were erupted.

The higher of two paleoelevation ranges estimated for 

the 11 Ma Aldrich Station flora, located ~22.5 km north of the 

Aurora district, is more consistent with post-Eureka Valley 

Tuff relief added to the volcanic field (4,200–4,600 ft). Based 

on the flora, paleoelevations in the 15–10 Ma Masonic and 

Aurora volcanic centers varied from ~4,300 to ~6,900 ft. 

Following eruption of large-volume stratovolcanoes and 

flow-dome fields in the southern part of the volcanic field at 

10–8 Ma, maximum paleoelevations exceeded 8,500 ft. If 

fossils in ~11 Ma Fletcher basin sediments are stratigraphically equivalent to Aldrich Station flora, then paleorelief may 

have been ~10,000 ft.

Introduction

Three precious metal mining districts and nine areas of 

extensive hydrothermally altered rocks, or alteration zones, 

occur in the Bodie Hills, an upland of Tertiary-Quaternary 

volcanic and Mesozoic granitic and metamorphic rocks that 

straddles the California-Nevada state boundary between 

Mono Lake and the East Walker River (fig. 1). Cumulative 

production from the mining districts, Bodie, Aurora, and 

Masonic, is 3.4 million ounces (Moz) of gold (Au) and 

28 Moz of silver (Ag). Small amounts of Hg were produced 

from the Potato Peak, Paramount-Bald Peak, and Cinnabar 

Canyon-US 395 alteration zones; a native sulfur (S°) resource 

in the Cinnabar Canyon-US 395 alteration zone has been 

identified by drilling. There are no known mineral resources 

in the other six alteration zones, Red Wash-East Walker River, 

East Brawley Peak, Sawtooth Ridge, Aurora Canyon, Four 

Corners, and Spring Peak. The mining districts and alteration 

zones formed between 13.4 and 8.1 Ma in predominantly 

~15–9 Ma volcanic rocks of the Bodie Hills volcanic field. 

Ages of hydrothermal minerals in the districts and zones are 

the same as, or somewhat younger than, the ages of volcanic 

host rocks (table 1).

Mining districts and alteration zones have been characterized briefly and integrated with the interpreted evolution of the 

Bodie Hills volcanic field by John and others (2012). Descriptions and genetic models of several mineral deposit types and 

alteration zones are included in Vikre and Henry (2011). This 

report provides an expanded characterization of the mining 

districts and alteration zones, including 40Ar/39Ar ages of 

igneous and hydrothermal minerals (table 1), minor element 

concentrations in mineralized and altered rocks, and modal, 

chemical and sulfur isotope compositions of hydrothermal 

mineral assemblages (tables 2, 3, 1-1 through 1-12). Paleohydrology, determined from attributes of mineral deposits and 

alteration zones, is also integrated with volcanic stratigraphy 

and mineral ages to reconstruct landform evolution during 

assembly and alteration of the volcanic field.

Descriptions of the Miocene mining districts and 

alteration zones are organized from the oldest (Masonic) 

to youngest (Spring Peak), as determined by 40Ar/39Ar ages 

of igneous and hydrothermal minerals and by stratigraphic 

constraints. Characteristics systematically described include 

definition of the district or alteration zone, history and production, stratigraphy, petrography, structure, forms of deposits, 

hydrothermal alteration, minor elements, reflectance spectra, 

and hydrothermal mineral ages. Fluid inclusion microthermometry and sulfur isotope compositions are also 

summarized for several districts and alteration zones. Small 

mines and prospects in pre-Tertiary rocks at the south end 

of Masonic Mountain, near Rancheria Gulch, and in the 

Aurora district (fig. 1) contain minor amounts of tungsten 

(W), copper (Cu) oxide, and Cu sulfide minerals that probably 

formed during the Mesozoic. Minor amounts of placer Au 

were recovered from Bodie Creek, and from drainages on the 

southwest margin of the Bodie Hills (Kleinhampl and others, 

1975). These pre-Tertiary and placer mineral occurrences are 

not described.

Volcanic (Le Bas and others, 1986) and plutonic 

(Streckeisen, 1976) rock unit names used herein are in accord 

with the International Union of Geological Sciences (IUGS) 

nomenclature system. The composition of each rock unit is the 

average composition computed from analyses in du Bray and 

others (2013), but the full range of compositional variation 

within each unit is also specified. Average abundances and 

grain sizes of phenocrysts in volcanic rocks are based on 

microscopic observations. Modal compositions of Mesozoic 

plutons are based on analyses of stained slabs.

The Masonic, Aurora, and Bodie Mining Districts were 

established, named, and renamed in the mid-1800s, in part 

during confirmation of the boundary between California and 

Nevada. In this report, the three districts are given informal 

dimensions that encompass all productive mines and most 

prospects. The nine alteration zones, named after local 

geographic features, are defined on the basis of significant 

volumes of mostly Miocene volcanic rocks in which 

(1) primary minerals have been partially or entirely replaced 

by hydrothermal minerals; and (2) fabric has been modified 

substantially by hydrothermal mineral replacement, brecciation, and veining, and by hydrothermal leaching. The largest 

alteration zones, Red Wash-East Walker River, ParamountBald Peak, and Cinnabar Canyon-US 395, record strong 

disequilibrium between hydrothermal fluids and permeable 

volcaniclastic rocks, resulting in (1) extensive volumes of 

discolored, fine-grained, pyritic, and low-density rocks that 

are susceptible to weathering; and (2) stratiform masses of 

densely silicified rocks that comprise resistant hills, ridges, 

spines, and mesa-like landforms. Visual contrasts between 
4 Gold-Silver Mining Districts, Alteration Zones, and Paleolandforms in the Miocene Bodie Hills Volcanic Field

Figure 1. Map showing locations of mining districts (line pattern) and alteration zones (crosshatch pattern) in the Bodie 

Hills, California and Nevada; commodity produced or resource shown in parentheses. Base from Fleck and others (2015).

119°15' 10' 05' 119° 55' 50' 118°45'

38°25'

20'

15'

10'

38°05'

0 5

0 5

10 MILES

10 KILOMETERS

CALIFORNIA

NEVADA

Mount

Biedeman

Potato

Peak Bodie

Mountain

Masonic

Mountain

Beauty Peak

Aurora

Crater

Bald Peak

Mono Lake

Mono Valley

Fletcher

Valley

Bridgeport 

Valley

SWEETWATER

MOUNTAINS

Rough

Creek

East

Walker

River

Aurora

Canyon 

Big Alkali

Bodie

Creek

Masonic

Bridgeport

Bodie

Aurora Bridgeport

Reservoir

167

182

Masonic

(Au, Ag, Cu)

Red WashEast Walker River

Bodie

(Au, Ag)

Sawtooth Ridge

B O D I E 

H I L L S 

Alteration zone

Mining district

EXPLANATION

East Brawley 

Peak

Spring Peak 

sinter (Hg)

Brawley 

Peaks

Aurora (Au, Ag)

Aurora Canyon

Cinnabar Canyon-US 395 (Hg, S°)

Potato Peak (Hg)

Paramount-Bald 

Peak (Hg) Four

Corners

395

Fig. 1

CALIFORNIA

NEVADA

Map area
Introduction 5

Table 1. 40Ar/39Ar dates (Ma) of igneous and hydrothermal minerals in mining districts and alteration zones (AZ) of the Bodie Hills, 

determined by incremental heating and laser fusion. Some K-Ar and 40Ar/39Ar dates (see footnotes) are from Kleinhampl and others 

(1975), Morton and others (1977), Breit (2000), and Larry Snee (written commun.); most 40Ar/39Ar dates of igneous minerals are from 

John and others (2012). Dates are based on Fish Canyon Tuff sanidine=28.02 Ma. Coordinates are NAD27.—Continued

[—, no data; qtz, quartz; Kspar, potassium feldspar; K, potassium; py, pyrite; chlor, chlorite]

Sample 

number

Latitude

(decimal 

degrees)

Longitude

(decimal 

degrees)

Lithology and (or) location Mineral Age (Ma) and 

error (1σ)

Sample index 

number on 

figures

Masonic Mining District

Trachyandesite of Masonic (Tma, Tmai)

10-BA-9 38.3528 –119.0207 Porphyritic plug in trachyandesite of Masonic Plagioclase 14.998 ± 0.019 —

098-12B 38.38762 –119.18139 Lava flow in trachyandesite of Masonic Plagioclase 14.715 ± 0.025 —

09-BA-7 38.33786 –119.08727 Lava flow in trachyandesite of Masonic Plagioclase 14.674 ± 0.025 —

098-12D 38.4 –119.1194 Lava flow in trachyandesite of Masonic Plagioclase 14.590 ± 0.02 4 (fig. 14)

10-BA-13 38.3515 –119.1042 Porphyritic dome in trachyandesite of Masonic Plagioclase 14.410 ± 0.016 —

088-23F 38.31068 –119.117 Lava flow in trachyandesite of Masonic Plagioclase 14.193 ± 0.038 —

MAS10-76 38.38169 –119.11534 Hornblende andesite dome in trachyandesite of Masonic Hornblende 14.190 ± 0.021 7 (fig. 14)

10-BA-15 38.3413 –119.1157 Lava flow in trachyandesite of Masonic Plagioclase 14.140 ± 0.017 —

08-BA-62 38.32005908 –119.0494277 Lava flow in trachyandesite of Masonic Plagioclase 14.130 ± 0.031 —

10-BA-69 38.3054 –119.1365 Lava flow in trachyandesite of Masonic Plagioclase 14.107 ± 0.014 —

098-12F 38.37542 –119.11418 Lava flow in trachyandesite of Masonic Hornblende 14.094 ± 0.017 11 (fig. 3)

088-22B 38.37937 –119.07802 Lava flow in trachyandesite of Masonic Plagioclase 14.067 ± 0.08 12 (fig. 3)

Trachyandesite of Masonic Gulch (Tamg)

MAS10-75 38.39169 –119.11549 Porphyritic trachyandesite dome in trachyandesite 

of Masonic

Plagioclase 13.497 ± 0.023 13 (fig. 14)

MAS10-72 38.40189 –119.13718 Porphyritic trachyandesite dome in trachyandesite 

of Masonic

Plagioclase 13.485 ± 0.017 14 (fig. 14)

MAS10-73 38.39643 –119.1347 Porphyritic trachyandesite dome in trachyandesite 

of Masonic

Plagioclase 13.467 ± 0.016 15 (fig. 14)

098-12E 38.39143 –119.12397 Porphyritic trachyandesite dome in trachyandesite 

of Masonic

Plagioclase 13.441 ± 0.026 16 (fig. 14)

Andesite of Lakeview Spring (Tals)

07-BA-38 38.36049 –119.14502 Andesite of Lakeview Spring dome Plagioclase 12.930 ± 0.03 17 (fig. 2)

Hydrothermal minerals

MAS12-10 (#2) 38.33762 –119.15973 Success Mine area Alunite 13.638 ± 0.077 —

MAS12-10 (#1) 38.33762 –119.15973 Success Mine area Alunite 13.398 ± 0.081 —

MAS07-1A 38.34991667 –119.1483167 Chemung Mine; volcaniclastic rocks Alunite 13.390 ± 0.07 20 (fig. 2)

MAS09-1A 38.35847 –119.13824 Red Rock Mine area; volcaniclastic-flow sequence Alunite 13.370 ± 0.11 21 (fig. 2)

MAS09-1 38.35783 –119.13268 Red Rock Mine area; volcaniclastic-flow sequence Alunite 13.320 ± 0.14 22 (fig. 2)

MAS07-3 38.35968 –119.12682 Sarita mine; hydrothermal and clastic 

sedimentary strata

Alunite 13.260 ± 0.05 23 (fig. 2)

07-BA-40 38.36546 –119.11607 Pittsburg-Liberty Mine; granodiorite Alunite 13.020 ± 0.05 24 (fig. 2)

088-22A 38.36731 –119.10727 Maybell Mine; granodiorite Alunite 13.018 ± 0.061 25 (fig. 3)

MAS11-2B 38.36064 –119.08681 Perrini Mine, trachyandesite, upper dump Alunite 12.960 ± 0.020 26 (fig. 3)

MAS11-1 38.36041 –119.08369 Perrini Mine, trachyandesite, lower dump Alunite 12.956 ± 0.014 27 (fig. 3)

Basin-fill of Fletcher Valley

08SB032 38.34561 –118.95589 Unwelded tuff, Fletcher Valley sediments Plagioclase 11.075 ± 0.041 —

10-BA-62 38.36327 –119.00635 Tephra, Fletcher Valley sediments Plagioclase 10.582 ± 0.023 —

Biotite 10.464 ± 0.042 —

Red Wash-East Walker River AZ

Hydrothermal minerals

RW08-1 38.41123 –119.12414 Quartz-alunite matrix breccia Alunite 13.340 ± 0.035 28 (fig. 14)

MAS10-55 38.41419 –119.10259 Quartz-alunite matrix breccia Alunite 13.270 ± 0.02 29 (fig. 14)

East Brawley Peak AZ

Hydrothermal minerals

89EB002 — — Altered andesite, East Brawley Peak Alunite 1, 213.7 ± 0.5 —

FA66 38.2375 –118.9008 Silicified andesite, south slope East Brawley Peak Alunite 1, 212.34 ± 0.04 —

AUR10-3 38.23752 –118.89919 Silicified andesite, south slope East Brawley Peak Alunite 11.954 ± 0.016 —
6 Gold-Silver Mining Districts, Alteration Zones, and Paleolandforms in the Miocene Bodie Hills Volcanic Field

Table 1. 40Ar/39Ar dates (Ma) of igneous and hydrothermal minerals in mining districts and alteration zones (AZ) of the Bodie Hills, 

determined by incremental heating and laser fusion. Some K-Ar and 40Ar/39Ar dates (see footnotes) are from Kleinhampl and others 

(1975), Morton and others (1977), Breit (2000), and Larry Snee (written commun.); most 40Ar/39Ar dates of igneous minerals are from 

John and others (2012). Dates are based on Fish Canyon Tuff sanidine=28.02 Ma. Coordinates are NAD27.—Continued

[—, no data; qtz, quartz; Kspar, potassium feldspar; K, potassium; py, pyrite; chlor, chlorite]

Sample 

number

Latitude

(decimal 

degrees)

Longitude

(decimal 

degrees)

Lithology and (or) location Mineral Age (Ma) and 

error (1σ)

Sample index 

number on 

figures

Sawtooth Ridge AZ

Volcanic rocks

077-9C 38.27661 –118.93036 Porphyritic lava flow in rhyolite of Del Monte Canyon Plagioclase 11.258 ± 0.14 —

077-9D 38.27661 –118.93036 Porphyritic lava flow in rhyolite of Del Monte Canyon Plagioclase 11.197 ± 0.03 —

077-9C 38.27661 –118.93036 Porphyritic lava flow in rhyolite of Del Monte Canyon Sanidine 11.187 ± 0.02 —

077-9D 38.28562 –118.92803 Porphyritic lava flow in rhyolite of Del Monte Canyon Sanidine 11.136 ± 0.02 —

10-BA-21 38.30315 –118.8974 Glassy lava flow in rhyolite of Aurora Creek Sanidine 11.181 ± 0.022 —

10-BA-20 38.31679 –118.91129 Glassy pyroxene rhyolite, rhyolite of Aurora Creek Plagioclase 11.177 ± 0.013 —

Hydrothermal mineral

SAW11-9 38.29036 –118.91657 Brecciated rhyolite of Aurora Creek Alunite 11.105 ± 0.018 —

Aurora Canyon AZ

Hydrothermal mineral

PP09-10A1 38.25309 –119.13844 Silicified breccia matrix Alunite 10.870 ± 0.07 —

Volcanic rocks

098-13D 38.27655 –119.16062 Porphyritic plug in trachyandesite of Clark Canyon Plagioclase 11.341 ± 0.017 —

09-BA-43 38.26358 –119.16825 Porphyritic lava flow in trachyandesite of 

Clark Canyon

Plagioclase 11.268 ± 0.11 —

088-21A 38.27363 –119.13962 Flow dome in trachyandesite of Aurora Canyon Plagioclase 10.358 ± 0.025 —

098-13B 38.26802 –119.13218 Porphyritic intrusion in rhyolite of Bodie Hills Sanidine 9.813 ± 0.027 —

088-24B 38.25504 –119.14115 Porphyritic lava flow in trachyandesite of 

Willow Springs

Plagioclase 8.575 ± 0.22 —

088-24A 38.25278 –119.13951 Porphyritic dome in rhyolite of Big Alkali Plagioclase 6.201 ± 0.026 —

098-13A 38.25754 –119.12788 Porphyritic dome in rhyolite of Big Alkali Plagioclase 6.173 ± 0.028 —

09-BA-42 38.27001 –119.14887 Porphyritic dome in rhyolite of Big Alkali Biotite 5.455 ± 0.026 —

Potato Peak AZ

Hydrothermal mineral

08-BA-46 38.2443 –119.10385 Matrix of silicified breccia Alunite 10.830 ± 0.06 —

Rhyolite of Bodie Hills

08-BA-50 38.24816 –119.09663 Rhyolite Sanidine 9.757 ± 0.013 —

Trachydacite of Potato Peak

088-24D 38.22678 –119.10376 Porphyritic lava flow Plagioclase 9.090 ± 0.04 —

108-12B 38.23830 –119.00784 Porphyritic biotite-hornblende dacite Biotite 9.032 ± 0.022 —

098-13C 38.25072 –119.09223 Biotite rhyolite/dacite Plagioclase 8.998 ± 0.021 —

088-24C 38.24786 –119.11208 Porphyritic lava flow Plagioclase 8.996 ± 0.025 —

08-BA-68 38.1932 –119.0684 Porphyritic trachyandesite flow Plagioclase 8.99 ± 0.02 —

098-10C 38.24919 –119.09203 Biotite-hornblende dacite Plagioclase 8.982 ± 0.023 —

108-12A 38.24252 –119.04825 Porphyritic biotite-hornblende dacite Plagioclase 8.963 ± 0.016 —

08-BA-61 38.2077 –119.1017 Block and ash flow Plagioclase 8.93 ± 0.7 —

088-24E 38.21809 –119.10188 Biotite-hornblende dacite Plagioclase 8.925 ± 0.03 —

088-21E 38.23457 –119.08582 Porphyritic lava flow Plagioclase 8.860 ± 0.05 —

088-21B 38.2642 –119.0750 Porphyritic trachyandesite flow Plagioclase 8.84 ± 0.13 —

088-21D 38.2433 –119.09209 Porphyritic lava flow Plagioclase 8.810 ± 0.07 —

10-BA-46 38.1738 –119.1151 Porphyritic trachyandesite flow Plagioclase 8.779 ± 0.013 —

10-BA-66 38.17250 –119.10125 Porphyritic lava flow Plagioclase 8.749 ± 0.019 —
Introduction 7

Table 1. 40Ar/39Ar dates (Ma) of igneous and hydrothermal minerals in mining districts and alteration zones (AZ) of the Bodie Hills, 

determined by incremental heating and laser fusion. Some K-Ar and 40Ar/39Ar dates (see footnotes) are from Kleinhampl and others 

(1975), Morton and others (1977), Breit (2000), and Larry Snee (written commun.); most 40Ar/39Ar dates of igneous minerals are from 

John and others (2012). Dates are based on Fish Canyon Tuff sanidine=28.02 Ma. Coordinates are NAD27.—Continued

[—, no data; qtz, quartz; Kspar, potassium feldspar; K, potassium; py, pyrite; chlor, chlorite]

Sample 

number

Latitude

(decimal 

degrees)

Longitude

(decimal 

degrees)

Lithology and (or) location Mineral Age (Ma) and 

error (1σ)

Sample index 

number on 

figures

Aurora Mining District

Volcanic rocks

00-BA-16 38.2708 –118.8908 Porphyritic lava flow in trachyandesite of Aurora Hornblende 3

13.130 ± 0.44 —

00-BA-26 38.2542 –118.8841 Porphyritic lava flow in trachyandesite of Aurora Hornblende 3

13.130 ± 0.08 —

108-10A 38.27293 –118.91272 Fine-grained pyroxene trachyandesite of Aurora Plagioclase 12.58 ± 0.024 —

108-10C 38.2805 –118.9062 Porphyritic lava flow in trachyandesite of West 

Brawley Peak

Plagioclase 11.514 ± 0.019 —

10-BA-21 38.30315 –118.8974 Porphyritic lava flow in rhyolite of Aurora Creek Sanidine 11.181 ± 0.022 —

10-BA-27 38.275 –118.9045 Porphyritic intrusion(?) in rhyolite of East 

Brawley Peak

Sanidine 11.178 ± 0.016 —

10-BA-20 38.3168 –118.9113 Sparsely porphyritic lava flow in rhyolite of 

Aurora Creek

Plagioclase 11.177 ± 0.013 —

Hydrothermal minerals

ESM — — Altered andesite wall rock, Esmeralda vein Illite 1, 212.2 ± 0.3 —

CH8Z1 38.28361 –118.86889 Andesite altered to qtz-Kspar-K-mica-py-chlor; 

Juniata vein

Whole rock 2, 410.9 ± 0.3 —

AU-1/58/DD61 38.266 –118.9 Esmeralda vein K-feldspar 2, 310.47 ± 0.1 —

AU-2/59/DD61 38.28437 –118.8934 Last Chance Hill, Del Monte shaft dump K-feldspar 2, 310.35 ± 0.05 —

FA1 38.2931 –118.8914 Prospectus vein Adularia 1, 210.04 ± 0.03 —

37 — — Quartz-adularia vein Adularia 2, 510.6 ± 0.2 —

Four Corners AZ

Trachyandesite of Aurora Canyon

088-23A 38.27852 –119.10021 Porphyritic flow dome Biotite 10.580 ± 0.03 —

088-23B 38.27831 –119.09908 Porphyritic flow dome Biotite 10.540 ± 0.05 —

088-23D 38.28113 –119.10206 Porphyritic flow dome Biotite 10.460 ± 0.032 —

088-25A 38.27322 –119.09077 Porphyritic flow dome Plagioclase 10.430 ± 0.03 —

088-23B 38.27831 –119.09908 Porphyritic flow dome Plagioclase 10.310 ± 0.02 —

088-23A 38.27852 –119.10021 Porphyritic flow dome Plagioclase 10.270 ± 0.11 —

088-23D 38.28113 –119.10206 Porphyritic flow dome Plagioclase 10.270 ± 0.05 —

Paramount-Bald Peak AZ

Volcanic rocks

09-BA-35 38.2905 –119.0464 Porphyritic dacite plug Biotite 11.269 ± 0.034 —

077-8B 38.2833 –119.0562 Porphyritic dacite plug Sanidine 11.160 ± 0.03 —

077-8C 38.27145 –119.07783 Flow dome in trachyandesite of Aurora Canyon Biotite 10.467 ± 0.04 —

077-8C 38.27145 –119.07783 Flow dome in trachyandesite of Aurora Canyon Sanidine 10.447 ± 0.01 —

077-8C 38.27145 –119.07783 Flow dome in trachyandesite of Aurora Canyon Plagioclase 10.426 ± 0.03 —

08-BA-65 38.3107146 –118.978084 Glassy lava flow in rhyolite of Bald Peak Sanidine 9.686 ± 0.01 —

09-BA-49 38.26389 –119.04748 Trachydacite ignimbrite in Eureka Valley Tuff Biotite 9.267 ± 0.019 —

Cinnabar Canyon-US 395 AZ

Trachyandesite of Mount Biedeman

108-9A 38.1654 –119.0982 Biotite hornblende andesite lava Plagioclase 9.947 ± 0.019 —

108-12F 38.1634 –119.0992 Glassy porphyritic andesite lava Plagioclase 9.939 ± 0.024 —

10-BA-61 38.1401 –119.0155 Glassy block and ash flow Plagioclase 9.676 ± 0.061 —

6-215-1 38.1344 –119.0825 Hornblende andesite lava Plagioclase 3

9.24 ± 0.008 —

098-11E 38.1110 –119.1584 Hornblende andesite lava Plagioclase 9.019 ± 0.028 —

09-BA-22 38.1430 –119.1797 Pyroxene andesite flow Plagioclase 8.996 ± 0.10 —

09SB015A 38.1231 –119.1484 Porphyritic trachyandesite lava Plagioclase 8.895 ± 0.06 —
8 Gold-Silver Mining Districts, Alteration Zones, and Paleolandforms in the Miocene Bodie Hills Volcanic Field

Table 1. 40Ar/39Ar dates (Ma) of igneous and hydrothermal minerals in mining districts and alteration zones (AZ) of the Bodie Hills, 

determined by incremental heating and laser fusion. Some K-Ar and 40Ar/39Ar dates (see footnotes) are from Kleinhampl and others 

(1975), Morton and others (1977), Breit (2000), and Larry Snee (written commun.); most 40Ar/39Ar dates of igneous minerals are from 

John and others (2012). Dates are based on Fish Canyon Tuff sanidine=28.02 Ma. Coordinates are NAD27.—Continued

[—, no data; qtz, quartz; Kspar, potassium feldspar; K, potassium; py, pyrite; chlor, chlorite]

Sample 

number

Latitude

(decimal 

degrees)

Longitude

(decimal 

degrees)

Lithology and (or) location Mineral Age (Ma) and 

error (1σ)

Sample index 

number on 

figures

Hydrothermal minerals

CC09-9D1 38.19869 –119.1705 Matrix of silicified breccia in altered dacite(?) Alunite 8.820 ± 0.29 —

CC09-9D2 38.19869 –119.1705 Veins cutting silicified breccia Alunite 8.680 ± 0.02 —

39509-3K 38.20793 –119.22751 Partially leached clasts in volcaniclastic deposits Alunite 8.169 ± 0.013 —

Trachyandesite of Willow Springs

088-24B 38.25504 –119.14115 Porphyritic hornblende-pyroxene trachyandesite Plagioclase 8.575 ± 0.022 —

08-BA-51 38.17449 –119.15441 Dacite flow breccia Plagioclase 8.305 ± 0.017 —

088-24F 38.20176 –119.08978 Olivine-pyroxene trachyandesite Plagioclase 8.154 ± 0.02 —

077-7B 38.19178 –119.1524 Lava flow Biotite 8.124 ± 0.03 —

077-7B 38.19178 –119.1524 Lava flow Plagioclase 8.094 ± 0.03 —

077-7B 38.19178 –119.1524 Lava flow Hornblende 8.073 ± 0.02 —

077-7A 38.19178 –119.1524 Lava flow Plagioclase 8.053 ± 0.02 —

077-7A 38.1786 –119.19476 Lava flow Biotite 8.002 ± 0.04 —

Dacite of Hot Springs Canyon

39509-10 38.21532 –119.22755 Lava flow Plagioclase 8.070 ± 0.017 —

Bodie Mining District

Dacite of Silver Hill

108-12E 38.20763 –118.96489 Porphyritic biotite-hornblende dacite Plagioclase 9.140 ± 0.020 1

09-BA-26 38.2036 –119.00021 Block and ash flow in dacite of Silver Hill Biotite 9.132 ± 0.02 2 (fig. 37)

108-12C 38.18925 –118.98343 Porphyritic clinopyroxene-biotite dacite Plagioclase 9.088 ± 0.014 3

077-6F 38.18809 –119.00854 Dome in dacite of Silver Hill Plagioclase 9.088 ± 0.03 4 (fig. 37)

08-BA-66 38.1863 –119.0568 Block and ash flow Plagioclase 9.07 ± 0.024 5

108-12D 38.17315 –118.97800 Porphyritic oxyhornblende-biotite dacite Plagioclase 9.017 ± 0.014 6

077-7F 38.20252 –119.0263 Late intrusion in dacite of Silver Hill Plagioclase 8.925 ± 0.03 7 (fig. 37)

Silver Hill series veins

09-BA-28I 38.2015 –119.0036 Red Cloud Mine dump Adularia 8.852 ± 0.013 8 (fig. 37)

BOD09-3 38.20146 –119.0048 Red Cloud Mine dump Adularia 8.628 ± 0.014 9 (fig. 37)

BOD09-5 38.2043 –119.0066 Oro Mine dump Adularia 8.473 ± 0.007 10 (fig. 37)

AU-18/65/DD61 38.201 –119.004 Red Cloud Mine dump Adularia 2, 38.46 ± 0.02 11 (fig. 37)

Burgess series veins

BOD11-3B 38.21257 –119.00402 Layered vein; Upper Hobart Tunnel dump Adularia 8.542 ± 0.025 12 (fig. 37)

11-BA-22 38.21257 –119.00402 Bodie Mine dump Adularia 8.498 ± 0.005 13 (fig. 37)

BOD11-4E 38.21257 –119.00402 Bodie Mine dump Adularia 8.426 ± 0.003 14 (fig. 37)

AU-16/63/DD61 38.215 –119.004 Roseklip open-cut, southeast slope Standard Hill Adularia 2, 38.38 ± 0.02 15 (fig. 37)

Incline series veins

077-6A 38.2149 –119.0037 Upper southeast slope Standard Hill Adularia 8.290 ± 0.02 16 (fig. 37)

AU-17/64/DD61 38.215 –118.997 Tioga Mine dump Adularia 2, 38.28 ± 0.04 17 (fig. 37)

11-BA-7G 38.2042 –119.00649 Oro Mine dump Adularia 8.217 ± 0.012 18 (fig. 37)

11-BA-21 38.2037 –119.00919 Noonday Mine dump Adularia 8.124 ± 0.006 19 (fig. 37)

Uncorrelated veins

12-BA-17 38.21961 –119.00083 Euhedrons in lenticular vug in narrow vein; dump, 

top of Bodie Bluff

Adularia 8.358 ± 0.029 20 (fig. 37)

BOD11-3A 38.21961 –119.00354 Euhedrons in lenticular vug in narrow vein; Upper 

Hobart Tunnel dump

Adularia 8.194 ± 0.005 21 (fig. 37)

1

Breit (2000); age standard not provided; location coordinates for some samples not provided.

2

Age standard not provided and age may have been calculated using Taylor Creek rhyolite age=27.84 Ma.

3

Analysis by L. Snee.

4

Morton and others, 1977.

5

Kleinhampl and others, 1975.
Introduction 9

Table 2. Sulfur isotope compositions (‰) of sulfide and sulfate minerals and sulfur (S°) from mining districts and alteration zones, 

and calculated sulfur (S) isotope equilibrium temperatures.—Continued

[Some analyses are from Vikre (2000) and Vikre and Henry (2011); others were provided by Simon Poulson (University of Nevada Reno, Reno, Nev.). 

Sulfur isotope equilibrium temperatures (T °C SO4-py) were calculated from fractionation equations in Field and Fifarek (1985). AZ, alteration zone; en, 

enargite; py, pyrite; ISV, Incline series vein; BSV, Burgess series vein; FV, Fortuna vein; SHSV, Silver Hill series vein; —, no data]

Sample number Mineral Location δ34S sulfide 

minerals δ34S S° δ34S alunite; barite T °C SO4

-py

Masonic Mining District

Sarita Mine

MAS07-3 Enargite Mill loading bin reject –10.4 — — 1

192; en=py

MAS07-3A Alunite Mill loading bin reject — — 18.1 —

Red Rock Mine

MAS09-1 Alunite Mine dump, hillside — — 13.4 —

MAS09-1 Pyrite Mine dump, hillside –11.0 — — 231

MAS09-1 Enargite Mine dump, hillside –10.5; –10.2 — — 1

238; 228; en=py

MAS09-1 Alunite Mine dump, hillside — — 14.5 —

MAS09-3a Enargite Mine dump –12.2 — — —

Chemung Mine

MAS07-1A Alunite Cut — — 15.4 —

MD82-2A Sulfur Mill dump — –16.8 — —

MD82-2A Sulfur Mill dump — –16.5 — —

MD82-2A Sulfur Mill dump — –16.9 — —

MD88-1s Pyrite Mill dump –9.4 — — —

MD88-4s Luzonite Mill dump –11.8 — — —

MD88-1Bs Barite Mill dump — — 13.6 —

MD88-3As Alunite Mill dump — — 7.1 —

Pittsburg-Liberty Mine

MAS10-62 Pyrite Dump on Masonic Gulch –10.6 — — 218

MAS10-62 Alunite Dump on Masonic Gulch — — 15.1 —

Perini Mine

MAS11-2B Pyrite Upper dump on Red Wash –9.4 — — 188

MAS11-2B Alunite Upper dump on Red Wash — — 19.6 —

MAS11-3B Enargite Upper dump on Red Wash –12.2 — — 1

167; en=py

Maybell-Alton Jack Mine

MAS08-21 Pyrite Middle dump –10.0 — — —

MAS08-22 Pyrite Lower dump –8.0 — — —

Aspen Grove Mine

MAS08-23 Pyrite Prospect dump –7.9 — — 198

MAS08-23 Enargite Prospect dump 0.2 — — 1

283; en=py

MAS08-23 Alunite Prospect dump — — 19.9 —

Red Wash-East Walker River AZ

RW08-1 Alunite Western end of AZ — — 20.60 —

Sawtooth Ridge AZ

SAW11-9 Alunite Del Monte Creek — — –3.2 —

Potato Peak AZ

POTPK08-1 Cinnabar Alta Plana Mine open cut –10.30 — — —

POTPK08-1 Cinnabar Alta Plana Mine open cut –9.80 — — —

POTPK08-1 Barite Alta Plana Mine open cut — — 11.60 —

08-BA-46 Alunite Alta Plana Mine open cut — — 16.30 —
10 Gold-Silver Mining Districts, Alteration Zones, and Paleolandforms in the Miocene Bodie Hills Volcanic Field

Table 2. Sulfur isotope compositions (‰) of sulfide and sulfate minerals and sulfur (S°) from mining districts and alteration zones, 

and calculated sulfur (S) isotope equilibrium temperatures.—Continued

[Some analyses are from Vikre (2000) and Vikre and Henry (2011); others were provided by Simon Poulson (University of Nevada Reno, Reno, Nev.). 

Sulfur isotope equilibrium temperatures (T °C SO4-py) were calculated from fractionation equations in Field and Fifarek (1985). AZ, alteration zone; en, 

enargite; py, pyrite; ISV, Incline series vein; BSV, Burgess series vein; FV, Fortuna vein; SHSV, Silver Hill series vein; —, no data]

Sample number Mineral Location δ34S sulfide 

minerals δ34S S° δ34S alunite; barite T °C SO4

-py

Aurora District

K011 Sulfides Antelope Mine2 8.3 — — —

K229 Sulfides Antelope Mine2 –8.7 — — —

K147 Sulfides Amador Mine2 10.6 — — —

K155 Sulfides Amador Mine2 10.9 — — —

K208 Sulfides Martinez Tunnel2 –8.5 — — —

K2079 Sulfides Wide West Mine –7 — — —

AUR12-1A Pyrite New Esmeralda Mine cut –6.3 — — —

AUR12-2A Sulfides Esmeralda vein, S end –5.4; –2.4 — — —

Paramount-Bald Peak AZ

PM08-1A Cinnabar Paramount Mine upper adit –4.70 — — —

PM08-1B Cinnabar Paramount Mine upper adit –5.30 — — —

Cinnabar Canyon-US 395 AZ

CC08-1 Cinnabar Calmono Mine dump –0.1 — — —

CC08-1 Cinnabar Calmono Mine dump –0.7 — — —

08-BA-54A Alunite drainage W of Cinnabar Canyon — — 2.5 —

CAMO91-1As Sulfur DDH core3 — –4.6 — —

CAMO91-1Bs Sulfur DDH core3 — –5.2 — —

CCD7 Sulfur DDH core; surface discards — –4.7 — —

CCD7 Sulfur DDH core; surface discards — –4.7 — —

CCD8B Sulfur DDH core; surface discards — — — —

CCD8B Pyrite 1 DDH core; surface discards –8.0 — — —

CCD16 Pyrite 2 DDH core; surface discards –9.8 — — —

CCD16 Barite DDH core; surface discards — — 1.1 —

Bodie Mining District

BOD11-11A Pyrite Bodie Mine dump; ISV 1.4 — — —

OD 7604 Sulfides Standard Mine, 528 level; FV4 0.6 — — —

CSMMM-1793 Sulfides Jupiter Mine; BSV? 5 –2.4 — — —

CSMMM-7045 Sulfides Mono Mine; BSV5 –4.7 — — —

CSMMM-7638 Sulfides Belvedere Mine; BSV5 0.3 — — —

BOD09-7 Acanthite Lent Mine dump; BSV? –1.8 — — —

BOD11-1 Galena Oro Mine dump; SHSV –1.5 — — —

BOD11-1F Chalcopyrite Oro Mine dump; SHSV –0.1 — — —

CSMMM-5304 Sulfides Oro Mine, 520 level; SHSV5 –0.9 — — —

BOD11-2A Tetrahedrite Contention Mine dump; SHSV 0.5 — — —

BOD11-5 Tetrahedrite Red Cloud Mine dump; SHSV –3.4 — — —

BOD11-22B Chalcopyrite S slope Bodie Bluff; SHSV 0.1 — — —

CSMMM-2009 Sulfides Addenda Mine, 500 level; SHSV5 –0.0 — — —

CSMMM-7568 Tetrahedrite West Noonday Mine; SHSV5 0.6 — — —

1

Temperature calculated based on pyrite-alunite fractionation. 

2

Keck collection, University of Nevada Reno (Reno, Nev.).

3

Sample provided by M. Ward.

4

Mackay-Stanford collection, University of Nevada Reno (Reno, Nev.).

5

California State Mining and Mineral Museum collection (Mariposa, Calif.).
Bodie Hills Volcanic Field 11

Table 3. Reporting limits (concentration range) for element 

concentrations in tables A-1 through A-12. 

[Concentrations were determined by fire assay-inductively coupled plasmamass spectrometry (Au, Pd, Pt), cold-vapor and hydride generation atomic 

absorption (Hg), hydride generation atomic absorption (Se), automated 

sulfur analyzer (S), and inductively coupled-atomic emission spectrometrymass spectrometry (all other elements); ppm, part per million; ppb, part per 

billion]

Element Concentration range

Aluminum, Al 0.01% 15%

Antimony, Sb 0.05 ppm 1%

Arsenic, As 1 ppm 1%

Barium, Ba 5 ppm 1%

Beryllium, Be 0.1 ppm 100 ppm

Bismuth, Bi 0.04 ppm 1%

Cadmium, Cd 0.1 ppm 1%

Calcium, Ca 0.01% 40%

Cerium, Ce 0.05 ppm 0.10%

Cesium, Cs 0.05 ppm 0.10%

Chromium, Cr 1 ppm 1%

Cobalt, Co 0.1 ppm 1%

Copper, Cu 0.5 ppm 1%

Gallium, Ga 0.05 ppm 500 ppm

Gold 1 ppb 10 ppm

Indium, In 0.02 ppm 0.05%

Iron, Fe 0.01% 50%

Lanthanum, La 0.5 ppm 0.10%

Lead, Pb 0.5 ppm 5%

Lithium, Li 1 ppm 5%

Magnesium, Mg 0.01% 15%

Manganese, Mn 5 ppm 5%

Mercury, Hg 0.02 ppm not provided

Molybdenum, Mo 0.05 ppm 1%

Nickel, Ni 0.5 ppm 1%

Niobium, Nb 0.1 ppm 0.1%

Palladium, Pd 1 ppb 10 ppm

Phosphorous, P 50 ppm 1%

Platinum, Pt 0.5 ppb 10 ppm

Potassium, K 0.01% 15%

Rubidium, Rb 0.2 ppm 1%

Scandium, Sc 0.1 ppm 0.10%

Selenium, Se 0.2 ppm 4 ppm

Silver, Ag 1 ppm 1%

Sodium, Na 0.01% 15%

Strontium, Sr 0.5 ppm 1%

Sulfur, S 0.01% 5%

Sulfur, S 0.05% 35%

Tellurium, Te 0.1 ppm 0.05%

Thallium, Tl 0.1 ppm 1%

Thorium, Th 0.2 ppm 1%

Tin, Sn 0.1 ppm 0.10%

Titanium, Ti 0.01% 15%

Tungsten, W 0.1 ppm 1%

Uranium, U 0.1 ppm 1%

Vanadium, V 1 ppm 1%

Yttrium, Y 0.1 ppm 1%

Zinc, Zn 1 ppm 5%

gray, green, and purplish, unaltered to propylitically altered 

andesite, dacite, and rhyolite, and the beige to red-brown 

coloration of pervasively altered rocks have been used to 

approximate the areal extent of alteration zones. The margins 

of alteration zones are marked by a transition outward from 

pervasive discoloration and primary mineral hydrolysis to 

alteration mineral assemblages that are confined to fracture 

selvages and phenocrysts. However, because of map scale, 

margin irregularities, and transitional contacts, small volumes 

of less-altered rocks are included within alteration zones, and 

small volumes of pervasively altered rocks are excluded.

Descriptions of mining districts and alteration zones in 

the Bodie Hills provide information on characteristics that 

may be useful to exploration programs and mineral resource 

assessments. In addition, the evolution of landforms presented 

in this report is pertinent to the tectonic history of the Sierra 

Nevada and western Great Basin.

Bodie Hills Volcanic Field

The Bodie Hills comprise a >700 square kilometers (km2), 

15–6 Ma volcanic field north of Mono Lake, California. The 

field consists of coalescing stratovolcanoes and lava domes 

that were assembled onto an irregular pre-Tertiary surface 

composed of Paleozoic and Mesozoic metavolcanic and 

metasedimentary rock, and Cretaceous granitic rocks of the 

Sierra Nevada batholith ~8 kilometers (km) to the west (Eaton 

and others, 1978; John and others, 2012). The field includes 

~25 major eruptive units that comprise four trachyandesite 

stratovolcanoes emplaced along the margins of the field, and 

numerous, more centrally located, silicic trachyandesite to 

rhyolite flow-dome complexes. The ~ 40 by ~30 km field is in 

the southern segment of the ancestral Cascades magmatic arc, a 

subduction-related alignment of predominantly andesitic eruptive rocks that parallels the western margin of North America 

from southern Nevada to British Columbia. Compositions of 

most Bodie Hills volcanic rocks closely resemble those of 

subduction magmas worldwide, with SiO2 varying from 50 to 

77 weight percent, and high K, Ba/Nb, Ba/Ta, and La/Nb (see 

table 3 for a complete list of elemental abbreviations). Most of 

the rocks are porphyritic, commonly containing 15–35 volume 

percent phenocrysts of plagioclase, pyroxene, hornblende, and 

biotite. Geophysical data imply that the volcanic rocks were 

derived from shallow (< 2 km deep), subjacent magma reservoirs that solidified to low-density plutons (John and others, 

2012). The field is within the Walker Lane, a major northwesttrending zone of right-lateral structural accommodation 

between the Pacific and North American plates (Stewart, 1988, 

1992). It is northwest of and marginal to the Mina deflection, a 

complex, northeast-trending structural zone of faults that offset 

Walker Lane faults north of the Bodie Hills to the east (Stewart, 

1988; Hardyman and Oldow, 1991; Oldow, 1992; Oldow, 2003; 

Wesnousky, 2005; Faulds and Henry, 2008). Present elevations 

of volcanic rocks in the field are between ~ 6,500 feet (ft) 

(~1,970 meters [m]), the elevation of Bridgeport Valley, and 

10,240 ft (~3,110 m), the elevation of Potato Peak.
12 Gold-Silver Mining Districts, Alteration Zones, and Paleolandforms in the Miocene Bodie Hills Volcanic Field

Trachyandesite stratovolcanoes and trachydacite to 

rhyolite dome complexes in the Bodie Hills are as much as 

16 km in diameter. Most formed during two periods of eruptive activity: trachyandesite stratovolcanoes at 14.7–12.9 Ma, 

and trachyandesite-dacite complexes at 9.2–8.0 Ma (John and 

others, 2012). Smaller rhyolite domes and flow-domes were 

emplaced from ~6.2 to 5.5 Ma (John and others, 2012). The 

Miocene volcanic rocks are interbedded with, and overlain 

by, conglomerate and sandstone of Fletcher and Bridgeport 

Valleys (Gilbert and Reynolds, 1973). Following a 2 m.y. 

(million year) hiatus in volcanism, postsubduction rocks of 

the ~3.9–0.1 Ma, bimodal (trachybasalt to rhyolite), high-K 

Aurora volcanic field erupted unconformably onto rocks of the 

Bodie Hills volcanic field (Gilbert and others, 1968; Al-Rawi, 

1969; Chesterman and Gray, 1975; Kleinhampl and others, 

1975; Lange and others, 1993).

The scarcity of dikes in the volcanic field indicates a low 

horizontal component of stress in the middle and late Miocene. 

However, veins and faults in the three mining districts mark 

a change in strain vectors during evolution of the field from 

transtension, characteristic of Walker Lane tectonism, to 

extension at ~10 Ma when subduction ceased at the latitude of 

the Bodie Hills (Atwater and Stock, 1998). Compared to other 

volcanic fields in the southern segment of the Cascades arc, 

the prevalence of stratovolcanoes and domes of intermediate 

to silicic composition and absence of mafic rocks in the Bodie 

Hills may signify that a relatively thick crust lies beneath the 

volcanic field. Mafic, mantle-derived magma differentiated 

within this crust to form predominantly silicic eruptives 

with uniformly porphyritic texture (John and others, 2012). 

Plagioclase, pyroxene, hornblende, and biotite phenocrysts 

are present in most of the volcanic rocks. Olivine phenocrysts 

occur in some andesites; sanidine and quartz phenocrysts 

are present in most rhyolites. The groundmass of most rocks 

contains variable microphenocryst assemblages, chiefly 

plagioclase, but also Fe-Ti oxide minerals, clinopyroxene, and 

less commonly, hornblende and (or) biotite. Common accessory minerals are apatite and zircon.

Methods

Descriptions of mining districts and alteration zones are 

based on mapping and geophysical surveys, on published and 

unpublished reports and maps, and on samples collected and 

borrowed from archival repositories for mineral identification 

and textural analysis by petrography, X-ray diffraction (XRD), 

scanning electron microscopy (SEM), and short wave infrared 

spectrometry (SWIR). Other samples were collected for 

radioisotopic dating, and for determination of sulfur isotope 

compositions and minor element concentrations. Remotely 

sensed spectra, Advanced Spaceborne Thermal Emission 

and Reflection Radiometer (ASTER) data, were analyzed to 

determine the large-scale distribution and characteristics of 

hydrothermal mineral assemblages throughout the Bodie Hills.

Archival samples were borrowed from the Keck Museum 

at the University of Nevada Reno (Reno, Nevada), and from 

the California State Mining and Mineral Museum (Mariposa, 

California). Instrumental analyses (XRD, SEM, geochronology, isotope compositions, and element concentrations) were 

performed in laboratories at the U.S. Geological Survey 

(Menlo Park, California; Denver, Colorado), University of 

Nevada Reno (Reno, Nevada), and SGS Mineral Services 

(Toronto, Canada). SWIR analyses of hand samples used a 

portable infrared mineral analyzer (PIMA).

Some K-Ar and 40Ar/39Ar ages used in this investigation 

are from Kleinhampl and others (1975), Morton and others 

(1977), Breit (2000), John and others (2012), and Larry Snee 

(unpublished analyses). Additional 40Ar/39Ar ages (Ma) of 

igneous and hydrothermal minerals were determined by the 

incremental heating (multi-step) and laser fusion (single-step) 

methods (table 1). Following neutron irradiation of a single 

split of a sample, radiogenic 40Ar and potassium-derived 39Ar 

from neutron activation were simultaneously measured (for 

example, Dalrymple and Lanphere, 1974; McDougall and 

Harrison, 1999). Heating to release Ar was provided by laser, 

induction furnace, or resistance furnace. A series of incremental 

heating steps that comprises more than 50 percent of the total 

argon release, and in which each step gives an age within 

two standard deviations of the mean, defines a “plateau” age 

(Fleck and others, 1977). Laser fusion and furnace experiments 

that release all Ar from the sample in a single heating step 

provide “laser-fusion” or “total-gas” ages. Ages calculated 

by mathematically recombining the Ar released in all steps of 

incremental-heating experiments are referred to as “integrated” 

ages. Uncertainties for all Ar ages are reported at 1 standard 

error of the weighted mean (Renne and others, 2009).

Some sulfur isotope compositions (δ34S) of sulfide 

minerals, sulfate minerals, and native sulfur (S°) used in this 

investigation are from Vikre (2000) and Vikre and Henry 

(2011; table 2). Additional δ34S values were determined by 

Simon Poulson (University of Nevada Reno) using a Eurovector model 3028 elemental analyzer interfaced to a Micromass 

IsoPrime stable isotope ratio mass spectrometer, and following 

the methods of Giesemann and others (1994) and Grassineau 

and others (2001). The δ34S values are reported in units of 

per mil, part per thousand (‰) versus VCDT (Vienna Canyon 

Diablo troilite), and have an uncertainty of ± 0.2 ‰. Sulfur 

isotope equilibrium temperatures were calculated from 

fractionation equations in Field and Fifarek (1985).

Geochemical analyses were obtained under a U.S. 

Geological Survey contract with SGS Mineral Services. 

Element concentrations were determined using several multielement analytic methods with variable reporting limits (given 

as concentration ranges in table 3). Analytic methods included 

fire assay (FA)-inductively coupled plasma mass spectrometry 

(ICPMS) for Au, Pd, Pt, cold-vapor atomic absorption (AA) 

for Hg, hydride generation AA for Se, and inductively coupled 

plasma-atomic emission spectrometry-mass spectrometry 

(ICP-AES-MS) for all other elements except sulfur. Sulfur 

concentrations were determined using an automated sulfur 

analyzer. These methods were selected to include elements of 

economic interest (Au, Ag, Hg, As, Sb, Te, Se, Sn, Cu, Pb, Zn, 

and S).
Masonic Mining District 13

Atomic proportions of minerals and some mineral identities shown on SEM images were determined using integrated 

software. Atomic proportions of electrum were normalized to 

one. Atomic proportions of sulfide, selenide, and telluride minerals were calculated to positive integers of S, Se, or Te atoms, 

with the number of S, Se, or Te atoms corresponding to atoms 

per formula unit of the petrographically identified mineral. 

For minerals in which petrographic characteristics and atomic 

proportions do not correspond to documented minerals, atomic 

proportions were iteratively calculated relative to positive 

integers of S atoms to produce positive integers, or integers 

plus fractions, of other major atoms (for example, Cu, Ag). 

Comparison of atomic proportions of analyzed chalcopyrite to 

stoichiometric chalcopyrite, and replicate analyses, suggest an 

accuracy of ± 0.2 atoms.

Masonic Mining District

Location 

Secs. 14, 15, 16, 17, 20, 21, 22, 23, 29, 30, T. 6 N., R. 26 E., 

Mono County, California, Lyon County, Nevada (fig. 1)

History and Production

Gold was discovered in the Masonic Mining District 

in the 1860s by placer miners from Monoville (abandoned; 

originally located on Virginia Creek near Conway Summit), 

who named the district after the Freemasonry fraternal 

organization. In the latter half of the 19th century, mining 

activity in the Bodie Hills was focused on high-grade Au-Ag 

veins at Aurora and Bodie, and little development took 

place at Masonic until 1900–1902 when the Jump-Up-Joe 

and Pittsburg-Liberty Mines were located. Three towns 

were established: Upper, Middle, and Lower Masonic had a 

combined population that reached ~1,000. Gold and lesser Ag 

and Cu production occurred mainly during the period 1906–20 

(McLaughlin, 1915; Eakle, and others, 1917; Eakle and 

McLaughlin, 1919; Sampson, 1940). Production was sporadic 

because mining small, irregular deposits was often unprofitable, and because Au recovery by different milling operations 

was, at best, marginally successful. Episodic but short-lived 

mining revivals with small and mostly unrecorded production 

took place from the 1920s to 1960s (Sampson, 1940; Jenkins, 

1951; Wedertz, 1969; Mono County Historical Society 2004 

Newsletter).

Production totals are incompletely known because of the 

numerous small and episodic mining operations that spanned 

five or more decades. Total district production from 1902 

through 1959 is estimated at 55,800 ounces (oz) of Au, and 

39,000 oz of Ag from ~75,000 tons (t) of ore; minor amounts 

of Cu were also recovered (Long and others, 1998). The 

first ore shipment in 1907 (to the Selby, California, smelter), 

from the Pittsburg-Liberty Mine, consisted of 17 t valued at 

$1,040 per ton, or about 50 troy ounces per ton (opt) Au if all 

value was gold (at ~$20/oz). Pittsburg-Liberty production is 

estimated at $600,000 to $700,000 (~30,000 to 35,000 oz of 

Au, if all value was Au; Eakle and McLaughlin, 1919). Sarita 

Mine production was $425,000 (~20,000 oz of Au, if all value 

was Au), and Chemung Mine production was 3,700 oz of 

Au (R.T. Wilson and W.A. Rehrig, written commun., 1987). 

Ore grades at the Sarita and Lakeview Mines were reportedly 

0.2–2 opt Au (Eakle and McLaughlin, 1919). An unpublished 

assay plan (~1930s) of Sarita underground levels shows 

similar Au grades. An unpublished (1935) map of the Perrini 

Mine underground workings includes eight samples containing 

trace–0.18 opt Au, and 0.6–30.02 opt Ag over widths of 

2–6.7 ft (R.T. Wilson and W.A. Rehrig, written commun., 

1987). Drilling programs by several mining companies in 

the 1980s identified a resource of ~180,000 tons at 0.15 opt 

Au at the Sarita Mine (R.T. Wilson and W.A. Rehrig, written 

commun., 1987). It appears that some of this resource was 

mined from an open cut on the northwest side of New York 

Hill since the 1980s, although processing facilities for this 

excavation are not evident.

Stratigraphy

Published geologic maps and lithologic descriptions 

of the Masonic Mining District include those in Eakle and 

McLaughlin (1919), Johnson (1951), Vikre and Henry (2011), 

and John and others (2012). The oldest rocks in the district 

are Jurassic (?) metavolcanic rocks (Jmv) that are extensively 

exposed at lower elevations on Masonic Mountain (9,195 ft). 

These pre-Tertiary rocks, thought to represent metasomatized 

rhyolite (Johnson, 1951), form pendants in Mesozoic granitic 

rocks (Kg; fig. 2). Mesozoic granitic rocks consist of palegray to pinkish-gray, hypidiomorphic granular, equigranular 

to porphyritic granodiorite and minor monzogranite that 

comprise Masonic Mountain; a smaller mass of granodiorite 

is exposed about 6 km to the east (John and others, 2012). The 

medium-grained, 95.2 Ma granodiorite (Robinson and Kistler, 

1986) contains prominent, euhedral, perthitic, pink potassium 

feldspar megacrysts 2–5 centimeters (cm) long, and about 

3 volume percent red-brown biotite (Johnson, 1951; John and 

others, 2012; du Bray and others, 2013). The granitic rocks 

form a plutonic mass covered in most places by trachyandesite 

of Masonic.

The trachyandesite of Masonic is pale- to medium-darkgray, gray-green, and purplish, and variably porphyritic, 

and includes basaltic trachyandesite, trachydacite, basaltic 

andesite, and andesite. It comprises interbedded lava flows 

and mostly small-volume plugs and domes of trachyandesite 

that were erupted from 15 to 14 Ma (Tma, table 1), and 

includes associated volcaniclastic deposits (Tvc; figs. 2, 3, 4). 

Trachyandesite flows and volcaniclastic deposits aggregate 

tens to hundreds of meters in thickness. Combined, the lava 

flows, intrusions, and volcaniclastic deposits that make up the 

trachyandesite of Masonic define the nearly circular Masonic 

stratovolcano in the northwestern part of the Bodie Hills 

volcanic field (John and others, 2012).
14 Gold-Silver Mining Districts, Alteration Zones, and Paleolandforms in the Miocene Bodie Hills Volcanic Field

?

?

?

x

x

◄

◄

60–75

50

60–75

65–80

80–90

30–40

40

65

Jmv

Jmv

Jmv Tvc Tvc

Jmv

Tev

Jmv

Kg

Lakeview 

Spring

Masonic

Gulch

RED 

ROCK 

MINE

CHEMUNG 

MINE

Sunday 

adit

Pittsburg-Liberty

Mine Creek adit

LAKEVIEW 

MINE

SARITA MINE

PITTSBURGLIBERTY MINE

MASONIC 

MILL SITE

New York 

Hill

Home 

View 

Hill

Stall 

shaft

aspen

grove 

prospect

New 

York

 shaft

120, 160 

levels; 

projected

dike

HERMINE

MINE

Base modified from U.S. Geological Survey

Dome Hill, Calif.-Nev., 1989, 1:24,000

0 0.5

0 0.5

1 MILE

1 KILOMETER

figure 3

17

20

21

22

23

24

Fig. 2

Tma

Tma

Tma

Tls

Tev

Tvc

Tvc

Tvc

Tvc

Tvc Tvc

Tvc

Tals Tals

Tals

Tals

Tals

Qc

Qc

Qc

Qc

Qc

Qc

Tma

Kg

Kg

Kg

Kg

Tbar

Trbh

N

20

EXPLANATION

35

40

Kg Kg x◄

Tma

Tvc

Jmv

Tals

Trbh

Tbar

Tev

Tls

Qc

Mill tailings

Colluvium

Landslide

Eureka Valley Tuff (9.3–9.5 Ma)

Rhyolite of Big Alkali (5.5–6.2 Ma)

Rhyolite of Bodie Hills (9.6–9.9 Ma)

Andesite of Lakeview Spring (12.9 Ma)

Trachyandesite of Masonic

Volcaniclastic deposits and andesite

Altered slope wash

Landslide—Internal contacts delineate different slide blocks

Trachyandesite of Masonic (~14–15 Ma)

Granitic and metamorphic rocks

Granitic rocks

Metavolcanic and metasedimentary rocks

Dike

Altered fault zone

Contact—Dashed where approximated

Fault—Long-dashed where approximated, short-dashed where inferred, queried 

where uncertain

High-angle normal fault—Bar and ball on downthrown block

Aerial tramway line and ore bins

Bedding

Foliation

Mine shaft

Adit

Open-pit mine

40Ar/39Ar sample site and index number (table 1)

119°15' 119° 118°45'

38°25'

38°15'

38°05'

CALIFORNIA

NEVADA

Mono Lake

Mono Valley

Bridgeport

Fletcher Valley

East

Walker

River

Masonic

Bodie

Aurora

Area of map

Figure 2. Geologic map of the southwestern part of the Masonic Mining District, Mono County, California, and Lyon and 

Mineral Counties, Nevada. Aerial tramway ore bins (also shown on report cover) are ~120 m northeast of the Sarita Mine adit that 

accesses the 120 and 160 levels.
Masonic Mining District 15

Figure 3. Geologic map of the northeastern part of the Masonic Mining District, Mono County, California, 

and Mineral County, Nevada.

119°06' 119°05'

38°23'

38°22'

GOLD FUND 

MINE

MAYBELL

MINE

PERRINI

MINE

MELLOR

MINE

OLD MAN 

MINE

CRAZY MAN 

SHAFT

Dome 

Hill▲

Red

Wash

Tdi

HERMINE

MINE

ALTON 

JACK 

MINE

JUMP-UP 

JOE MINE

12

27

11

25

26

0 0.5

0 0.5

1 MILE

1 KILOMETER

EXPLANATION

Base modified from U.S. Geological Survey

Dome Hill, Calif.-Nev., 1989, 1:24,000

MINERAL COUNTY

MONO COUNTY

Fig. 3

Tmai

Tmai

Tma

Tma

Tma

Kgm Kgm Kgm

Kgm

Kgm

Tev

Qc

Qc

Tma

Tma

Colluvium

Eureka Valley Tuff (9.3–9.5 Ma)

Trachydacite intrusion

Trachyandesite of Masonic

Trachyandesite intrusions of Masonic (14.2 Ma)

Trachyandesite of Masonic (~14–15 Ma)

Granitic rocks

Granodiorite of Masonic Mountain (Cretaceous)

Contact—Dashed where approximated

Fault—Dashed where approximated, dotted where concealed

Altered fault zone

Mine shaft

Adit

40Ar/39Ar sample site and index number (table 1)

Tdi

Tev

Qc

119°15' 119° 118°45'

38°25'

38°15'

38°05'

CALIFORNIA

NEVADA

Mono Lake

Mono Valley

Bridgeport

Fletcher Valley

East

Walker

River

Masonic

Bodie

Aurora

Area of map
16 Gold-Silver Mining Districts, Alteration Zones, and Paleolandforms in the Miocene Bodie Hills Volcanic Field

Figure 4. Images of volcaniclastic deposits in the Red WashEast Walker River alteration zone and Masonic Mining District. 

A, Propyliticly altered debris flow in trachyandesite of Masonic, 

hill 6696 (elevation), and Red Wash-East Walker River alteration 

zone. Hammer for scale. B, Closeup view of black rectangle 

shown in A. C, Volcaniclastic deposits replaced by quartz, alunite, 

kaolinite, and pyrite (weathered to iron oxides), Sarita Mine. 

Hammer for scale.

Trachyandesite flows and intrusions contain 2–53 volume percent phenocrysts of plagioclase, clinopyroxene, 

hornblende, and trace amounts of biotite and olivine in a 

variably devitrified groundmass or, less commonly, in a felty 

intergrowth of plagioclase, opaque oxides, and clinopyroxene. 

Euhedral, acicular hornblende phenocrysts (2–5 millimeters 

[mm]) are a distinctive constituent in many places. Volcaniclastic deposits include laharic debris flows and lesser block 

and ash-flow deposits. These strata are massively to distinctly 

bedded, generally poorly sorted, clast- to matrix-supported, 

mass wasting deposits with a clay- and ash-rich matrix (fig. 4). 

Clasts are 1 cm to several meters in diameter, angular to 

subangular, and principally consist of volcanic rock fragments 

similar to the associated trachyandesite lavas and intrusions.

Between the Masonic Mining District and the Red WashEast Walker River alteration zone (fig. 1) some trachyandesite 

flows were erupted from small plugs marked by low-relief 

spires, generally meters in dimension, with steep foliations 

and joints. Conical to rounded hills in the northern and 

northeastern parts of the district comprise a group of larger 

trachyandesite and trachydacite domes that are the same age 

as trachyandesite flows (15.0, 14.4, and 14.2 Ma porphyritic 

and hornblende andesite plug and domes; Tmai, fig. 3; 

table 1), or younger than trachyandesite flows (13.5–13.4 Ma 

trachyandesite of Masonic Gulch; Tamg, table 1; undated 

trachydacite intrusion of Dome Hill; Tdi, fig. 3). Trachyandesite of Masonic also has been intruded by 12.9 Ma andesite of 

Lakeview Spring (Tals, fig. 2; table 1; John and others, 2012) 

that forms small-volume domes north of Masonic Mountain. 

The medium-pale-gray, moderately porphyritic andesite 

contains about 16 volume percent phenocrysts of plagioclase, 

hornblende, clinopyroxene, and trace amounts of olivine set in 

a moderately devitrified groundmass. Plagioclase phenocrysts 

are characteristically larger than those in most rocks in the 

Bodie Hills volcanic field.

Trachyandesite of Masonic west, northwest, and north of 

Masonic Mountain is overlain by 9.5–9.3 Ma Eureka Valley 

Tuff (Eureka Valley Tuff; Tev, figs. 2, 3; Pluhar and others, 

2009; John and others, 2012), and by Miocene and younger 

sedimentary deposits, including Fletcher Valley basin-filling 

fanglomerate, talus (Qfg and Qt, respectively), landslide 

deposits northwest of Lakeview Spring (Tls, fig. 2), perched 

terrace gravels, and perched fluviolacustrine sediments (Tg 

and Ts, respectively). The Eureka Valley Tuff is a grayishblack, moderately porphyritic trachydacite ash-flow tuff. It 

contains about 13 volume percent phenocrysts of plagioclase, 

biotite, clinopyroxene, and trace amounts of hornblende set 

in a grayish-black to iron-stained, reddish-brown, glassy 

groundmass. Clasts are composed of the same phenocrysts 

and matrix. In the Bodie Hills, where tuff is moderately to 

densely welded, most exposures appear to fill paleochannels. 

Abundance of biotite suggests that most Eureka Valley 

Tuff exposures in the Bodie Hills correlate with the lower, 

Tollhouse Flat Member, but upper member deposits also could 

be present.

A

BB

A

C

Fig. 4
Masonic Mining District 17

Basin-fill of Fletcher Valley consists of fanglomerate 

and braided stream deposits (Tfg, at least 200 m thick) 

that contain well-rounded volcanic pebbles and, in places, 

interbedded felsic tephra. The braided stream deposits are 

moderately well-sorted, clast-supported sandstone and 

siltstone that contain 0.1–2 mm subangular detrital clasts 

composed of plagioclase and lesser quartz. Mafic silicate 

minerals (clinopyroxene>olive-green hornblende>biotite) 

comprise about 1 volume percent of detrital grains. These 

deposits also contain lithologically diverse volcanic rock 

fragments. Interbedded tephra deposits have dates of 11.7 Ma 

(Gilbert and Reynolds, 1973), 11.07 Ma (John and others, 

2012), and 10.6–10.5 Ma (table 1). Landslide deposits 

northwest of Lakeview Spring (Tls) consist predominantly of 

altered volcaniclastic-flow sequence detritus derived from the 

northwest side of Masonic Mountain, and also include clasts 

of Eureka Valley Tuff, Mesozoic granitic rocks, metamorphic 

rocks, and andesite of Lakeview Spring. The unconsolidated, 

perched terrace gravels (Tg) vary from thin veneers to massive 

deposits of poorly sorted, silt- to boulder-size clasts in a 

sandy to silty matrix. Clasts include cobbles of Mesozoic 

granitic rocks, petrified wood, Eureka Valley Tuff, and diverse 

volcanic rocks. The semiconsolidated, gray- to dark-gray, 

perched fluviolacustrine sediments (Ts) are predominantly 

relatively well-sorted and distinctly bedded, coarse sand, sand, 

and silt.

In the Masonic Mining District and in the Red Wash-East 

Walker River alteration zone, large volumes of interstratified 

volcaniclastic deposits and trachyandesite lava flows were 

pervasively altered to hydrothermal mineral assemblages that 

include quartz, alunite, kaolinite, pyrophyllite, and pyrite 

(mostly weathered to iron oxides). Adjacent to and gradational with these quartz-alunite-altered volcaniclastic-flow 

sequences, are large volumes of less-altered, gray-green and 

purple lava and debris flows (figs. 2, 3) in which phenocrysts 

are partly to entirely replaced by chlorite, montmorillonite, 

iron oxide minerals, sericite (fine-grained white mica containing K), and calcite (propylitic alteration). Thin veneers (tens 

of meters thick) of quartz-alunite-altered sequence strata 

that overlie pre-Tertiary rocks on the west and north sides of 

Masonic Mountain (Tvc, figs. 2, 3) contain the Au-Ag-Cu 

deposits at the Sarita, Lakeview, and Chemung Mines. Thicker 

quartz-alunite-altered sequences are exposed between Sonoma 

Canyon and Red Wash, south of the East Walker River.

The quartz-alunite-altered volcaniclastic-flow sequences 

have been designated separate stratigraphic units by others (for 

example, Red Wash volcanics and Masonic Gulch volcanics, 

Johnson, 1951). Based on igneous and hydrothermal mineral 

ages, chemistry, petrography, and stratigraphy (John and 

others, 2012), the altered sequences reflect contrasting primary 

permeability among largely conformable volcaniclastic 

deposits and lava flows rather than separate lithologic units. 

More permeable volcaniclastic deposits and interstratified 

volcaniclastic-flow sequences have been intensely altered 

and discolored, whereas thicker sequences of homogenous 

flows have largely retained primary mineralogy and darker 

coloration. The volcaniclastic-flow sequences are cogenetic 

eruptives with limited lateral continuity (common on the 

flanks of stratovolcanoes) and their designation as separate 

map units is not warranted.

Structure

North and west of Masonic Mountain, trachyandesite of 

Masonic has been displaced along west-east and northeaststriking, high-angle normal faults (fig. 2). Down-to-the-north 

displacement along these faults, estimated at tens of meters, 

enabled preservation of relatively thick sections of the 

volcaniclastic-flow sequence along the East Walker River, and 

preservation of perched gravel terraces and fluviolacustrine 

sediments between the Masonic Mining District and East 

Walker River. Faults bounding granitic rocks on the west side 

of Masonic Mountain (Johnson, 1951; Stanford Geological 

Survey, 1961; John and others, 2012) are subparallel to 

mineralized structures and are inferred to have been active 

both during and after hydrothermal events in the district.

Mineralized structures in the Masonic Mining District 

are attributed to stress accommodation within the Walker 

Lane transtensional structural zone of strike-slip displacement, extension, and rotated tectonic blocks. Attitudes of 

these structures and kinematic indicators are consistent with 

maximum horizontal extension and compression oriented 

N60°W and N30°E, respectively (John and others, 2012).

Forms of Gold-Silver-Copper Deposits

Two forms of Au-Ag-Cu deposits occur in the Masonic 

Mining District (1) breccia and vein deposits in high-angle, 

subplanar fault zones, and (2) clastic and hydrothermal 

sedimentary deposits. 

Breccias and Vein Deposits in High-Angle, 

Subplanar Fault Zones

Faults that contain mineralized breccias and veins are 

part of a north- to northeast-trending, curvilinear series of 

en echelon faults that extend for ~6.5 km along the west 

and north sides of Masonic Mountain, and north of Masonic 

Mountain along Red Wash (figs. 2, 3). Individual fault 

segments are vertical to near-vertical, tens to several hundreds 

of meters long, and strike N15°W–N60°E. Most mineralized 

faults occur in granodiorite, metavolcanic rocks, and trachyandesite of Masonic north of Masonic Mountain, although the 

Chemung and Red Rock Mine workings follow high-angle 

fault zones partly in a volcaniclastic-flow sequence (fig. 2). 

District production was mostly derived from near-vertical, 

N15–20°W-striking faults in granodiorite and metavolcanic 

rocks in the Pittsburgh-Liberty Mine. Other small mines 

north of the Pittsburgh-Liberty, including Hermine, Maybell, 

Mellor, and Perrini (fig. 3), were excavated in similar north- to 
18 Gold-Silver Mining Districts, Alteration Zones, and Paleolandforms in the Miocene Bodie Hills Volcanic Field

northeast-striking, high-angle faults in granodiorite and 

trachyandesite of Masonic, but produced little or no ore. 

None of these mines are deeper than ~60 m (~200 ft). Stopes 

exposed at several mines indicate that mineable fault segments 

were as much as 2 m wide (fig. 5).

Based on textures of mineral assemblages, alunite 

dates, and sulfur isotope compositions, the sulfide, telluride, 

sulfate and silicate minerals, and electrum, described below 

and imaged by scanning electron microscopy (SEM), are 

largely if not entirely hypogene. Some complex Cu-As-SbFe-Bi-Pb-Ba-Al-Te-S-O phases may have been produced 

during weathering of sulfide minerals, or may represent 

submicron intergrowths of sulfide and oxide minerals. Iron 

oxide minerals that marginally replace pyrite are interpreted to 

have formed during weathering, and mineral assemblages in 

fault breccia and veins that formed during weathering are not 

further characterized.

Mineralized fault breccias consist of angular to subrounded clasts (millimeters to centimeters in size) of trachyandesite and pre-Tertiary rocks that have been variably replaced 

by quartz, alunite, pyrite (commonly weathered to iron oxide 

minerals), and lesser kaolinite, dickite, pyrophyllite, and 

diaspore. Some clasts consist of fine-grained to chalcedonic, 

gray to white quartz ± pyrite (partly to entirely weathered to 

iron oxides) in which little to no primary texture is evident 

(fig. 5). Fault breccias are locally multigenerational. Clasts 

that have been completely replaced by fine-grained white-gray 

quartz are juxtaposed with voids that represent leached clasts, 

and with clasts of porphyritic volcanic rocks in which phenocrysts have been leached. Breccia clasts in faults at the Perrini 

and Chemung Mines are replaced by quartz+pyrite(iron 

oxides) ± alunite, but many retain porphyritic texture.

Similar to altered clasts, breccia matrices consist 

predominantly of quartz, alunite, pyrite (iron oxides), and 

kaolinite, but locally include small amounts of pyrite, enargite, 

numerous other metallic minerals, and barite. Enargite in 

some samples is intergrown with quartz, pyrite, and alunite 

in centimeter-sized aggregates (fig. 5). Breccia matrices of 

dump samples from the Chemung Mine contain discrete 

crystals and intergrowths of pyrite, chalcopyrite, electrum, 

enargite, sphalerite, naumannite, and pyrrhotite; some enargite 

is encrusted on breccia clasts. The source of these samples is 

uncertain because the Chemung mill also processed ore from 

the Success, Sarita, and Lakeview Mines; sulfur (S°) in some 

samples links them to the Success Mine (Vikre, 2000).

Well-defined planar veins having sharp wall-rock 

contacts are relatively uncommon in the district. Veins cutting 

breccias in fault zones were mined with enclosing breccia 

at the Pittsburg-Liberty Mine, and, to a lesser extent, at the 

Red Rock and Lakeview Mines. The relationship between 

breccias and veins is evident in dump samples from the lower 

Pittsburg-Liberty Mine in Masonic Gulch that mostly consist 

of granodiorite that was altered to quartz+alunite+pyrite, 

brecciated, and cemented by dense fine-grained quartz+pyrite. 

Mineralized granodiorite breccia is cut by planar veins 

(millimeters to centimeters in size) composed of fine-grained, 

vuggy quartz, pyrite, and lesser enargite (fig. 5). Veins in the 

volcaniclastic-flow sequence at the Red Rock and Lakeview 

Mines are centimeters wide, and consist of fine- to mediumgrained, locally banded quartz, and lesser alunite, pyrite, 

and enargite.

Mineral and Rock Compositions of Breccias 

and Vein Deposits

Samples of mineralized fault breccia from upper 

Pittsburgh-Liberty Mine dumps (fig. 2) consist of completely 

silicified clasts that have been cemented by dense to porous 

(leached) matrices of fine-grained, gray to white quartz and 

aggregates of pyrite, enargite, famatinite, alunite, and lesser 

barite (millimeters to centimeters in size; fig. 5). Enargite 

and famatinite contain a large variety of <10 μm mineral 

inclusions of predominantly gold, silver, and copper minerals, 

based on semiquantitative SEM analyses. Gold minerals 

include Au-rich electrum (Au>0.8Ag<0.2 with minor Cu), an 

Au-Cu-Ag alloy (~Au7.1Cu2Ag0.9), an Au-Ag-S mineral 

(~Au2Ag1.7S2), a Cu-Ag-Au-Se-S mineral with variable 

Cu/Ag/Au, and an Au-Ag-Se mineral. Silver minerals are 

naumannite (~Ag2Se with minor Cu and Fe), and an Au-AgCu-Se mineral (~Ag4.5Au1.3Cu1.2Se3

). Copper minerals include 

~Cu6Bi1.7S5; Cu3Bi2S5 with minor Se; Cu4.3As1.2Sb0.1 S5; Cu1.5S 

with minor Sb; Cu2.3S with minor Se; Cu5Ag0.5Fe0.4Se3S1.3

(possibly athabascaite); Cu3As2 with minor Sb, Au, Fe, S; 

and a Cu-Se mineral (figs. 6, 7). Atomic proportions of some 

Cu-S inclusions correspond to those of digenite. Textures of 

Cu-As-O minerals intergrown with enargite and famatinite 

appear to be hypogene.

A sample from the lower Pittsburgh-Liberty adit dump in 

Masonic Gulch (figs. 2; 5) consists of Mesozoic granodiorite 

that has been altered to quartz and alunite, and cut by millimeter to ~1 cm veins of quartz, pyrite, enargite (As/Sb weight 

percent ~1.2–11; minor Te), famatinite (As/Sb weight percent 

~0.3–0.8), and lesser goldfieldite (Cu12(Te,Sb,As)4S13). Numerous minerals with variable Cu-Sb-As-Zn-Te-S, and variable 

Cu-Bi-S-Se, occur as intergrowths with, and inclusions in, 

pyrite, famatinite, and goldfieldite (fig. 8). Atomic proportions 

of many intergrown and inclusion phases in Pittsburg-Liberty 

Mine samples may represent submicron-sized intergrowths of 

several minerals (based on backscattered electron images), or 

undocumented minerals. Dump samples from Lakeview and 

Red Rock Mines consist of quartz, alunite, “goldfieldite” (with 

minor Zn), naumanite (with minor Te and S), argentite, and an 

Ag-Te-Se-S mineral.

Bulk samples of the imaged sections contain 27.6 

and 53.9 parts per million (ppm) Au, 136 and 395 ppm 

Ag, 92.1 and 149 ppm Pb, 26.9 and 461 ppm Sn, >10 ppm 

Hg, >500 ppm Te, and >1,000 ppm As, Ba, Bi, Cu, and Sb 

(table 1-1; Se was not determined). Other bulk samples from 

the Success, Chemung, and Pittsburgh-Liberty Mine dumps 

contain concentrations of minor elements that are broadly 

similar to, or lower than, concentrations in mineralized fault 

breccia from upper Pittsburgh-Liberty dumps.
Masonic Mining District 19

Figure 5. Images of mineralized fault breccias and veins in the Masonic Mining District. A, B, ~N-S-trending fault breccias cemented by 

quartz, alunite, and pyrite; A, Maybell-Alton Jack Mine upper adit (elevation ~7,750 ft) and B, Mellor Mine shaft (elevation ~7,600 ft; fig. 2). 

C, Fault breccia replaced by fine-grained quartz, alunite, pyrite, enargite, gold, and numerous other Cu-As-Sb-Bi-Fe-Te-Se-S minerals, 

unnamed mine dump, upper Pittsburg-Liberty Mine workings, 0.5 km (1,650 ft) east of New York Hill (sample MAS09-3b, elevation ~8,350 ft; 

fig. 2). D, Quartz+pyrite+alunite+enargite veins cutting granodiorite (left sample, Pittsburg-Liberty Mine, creek adit dump, elevation 

~7,500 ft) and trachyandesite (right sample, Red Rock Mine dump, elevation ~8,080 ft; fig. 2).

4 cm 4 cm

1 m

A

B

C D

Fig. 5
20 Gold-Silver Mining Districts, Alteration Zones, and Paleolandforms in the Miocene Bodie Hills Volcanic Field

Figure 6. Secondary electron images of fault breccia shown in figure 5C, Masonic Mining District (sample MAS09-3b, elevation ~8,350 ft). 

Mineral identifications and approximate atomic proportions in this figure and in figures 7, 8, and 9 were determined petrographically and 

by scanning electron microscopy algorithms. Imaged phases include quartz, barite, enargite, a Cu-Bi-S mineral (~Cu6

Bi1.7S5), a Cu-As 

mineral (~Cu3

As2), Au-rich electrum with minor Cu, and Cu-S minerals (~Cu1.5S; ~Cu2.3S).

enargite

barite

void

Cu3As2; minor Au Cu3As2

Au.78Ag.22

quartz

Au.78Ag.22

Au.78Ag.22Cu.05

Cu Au.71Ag.2Cu.09 1.5S

~Cu1.5S; minor Sb

~Cu1.5S; minor Sb

~Cu2.3S

quartz ~Cu3.2AsS4

~Cu6Bi1.7S5; minor Se

quartz

~Cu6Bi1.7S5

A B

C D

20μm 10μm

10μm 20μm
Masonic Mining District 21

Figure 7. Secondary electron images of fault breccia shown in figure 5C, Masonic Mining District (sample MAS09-3b, elevation 

~8,350 ft). Imaged phases include quartz, enargite, a Cu-As mineral (~Cu3As2), Au-rich electrum with minor Cu, chalcopyrite, 

naumannite, Cu-S minerals (~Cu1.5S; ~Cu1.8S; ~Cu2.5S; Cu4

S), Cu-Bi-S minerals (~Cu6Bi1.6S5; Cu3Bi2S5), Cu-As-S minerals (~Cu5.3As1.5S3; 

~Cu3.1AsS4

), and an Au-S mineral (~Au8.6S1.4). Some multielement analytical sites may represent submicrometer intergrowths of 

several minerals (see B, Ag-Au-Cu-Se, for example), or partially oxidized Cu-As-S minerals (see D, ~Cu4.4As2.7O2.8, for example).

~Cu3Bi2S5; minor Se

enargite

~Cu6Bi1.6S5

quartz

~Cu3As2; minor Fe, S

~Cu1.8S

~Cu3.1AsS4

~Cu1.5S

quartz

Au.76Ag.24

●

Ag-Au-Cu-Se

Fe-Cu-As-Sb-Ba-S-O

Cu1.5S

chalcopyrite

~Ag2Se; minor Cu

pyrite; minor Se

enargite

~Cu2.5S; minor Se

quartz

~Cu4.4As2.7O2.8

~Cu4.5As2.7O2.8

~Au6Cu.03S

~Au6Cu.03S

~Cu4S

~Cu4S

~Cu5.3As1.5S3

~Cu5.3As1.5S3

A B

C D

10 μm

20 μm 20 μm

10 μm

~Au.76Ag.24; minor Cu
22 Gold-Silver Mining Districts, Alteration Zones, and Paleolandforms in the Miocene Bodie Hills Volcanic Field

Figure 8. Secondary electron image of quartz+alunite+sulfide 

vein in granodiorite shown in figure 5D, left sample, Masonic 

Mining District (Pittsburg-Liberty Mine, creek adit dump, sample 

MD83-2, site 2A, elevation ~7,500 ft). Imaged phases include 

quartz, pyrite, Cu-Bi-S minerals, Cu-Sb-As-S minerals, and 

Cu-Sb-As-Te-Zn-S minerals.

If gold-bearing inclusions in enargite (described previously) are representative of Au occurrences in the district, then 

the absence of placer deposits and historically difficult gold 

recovery can be attributed to a predominance of micron-sized 

Au minerals. However, visible Au has been reported at several 

mines (Success, Chemung, Maybell, and Jump-Up Joe Mines; 

Eakle and others, 1917; Johnson, 1951; R.H. Kern, written 

commun., 1977; F.M. Smith, written commun., 1984). Gold 

at the Chemung Mine is described as “fine particles in milky 

quartz”, and “very fine particles in chalcedonic bands” in vugs 

(R.H. Kern, written commun., 1977). Gold at the Maybell 

Mine is described as “+1 mm pieces” in fine-grained quartz 

(F.M. Smith, written commun., 1984). Such relatively coarse 

Au apparently was not sufficiently abundant to form placer 

deposits.

Clastic and Hydrothermal Sedimentary Deposits

Distinctive, mineralized clastic and hydrothermal bedding 

sets occur within the volcaniclastic-flow sequence at the 

Sarita and Lakeview Mines (fig. 2). Opencut and underground 

workings of these mines do not clearly follow structures and 

thus attest to lateral dispersion of precious metals within parts 

of the sequence. Mineralized bedding sets are best exposed 

at the Sarita Mine on New York Hill and in mine workings 

on the adjacent hill ~0.5 km (~1,650 ft) to the east, where the 

volcaniclastic-flow sequence unconformably overlies granodiorite and pendants of pre-Tertiary metavolcanic rocks (fig. 2). 

At the Sarita Mine, volcaniclastic-flow strata are as much as 

~ 90 m (300 ft) thick, strike N30–70°W, and dip 30–80°SW. On 

the hill to the east, these strata are tens of meters thick, have 

variable northwest-northeast strikes, and dip 50°NW to 75°NE.

At the Sarita Mine, Au, Ag, and Cu were recovered 

from ore initially mined underground in the early 1900s and 

between 1951 and 1989, from an open cut on the northwest 

slope of New York Hill (the cut postdates the mine photograph 

in Jenkins (1951) and predates an unpublished mining 

company map dated 1989). The underground workings, open 

cut, and Au resource are in a zone of silicified, relatively 

well-sorted volcaniclastic strata that contains bedding sets of 

very fine-grained, quartz-rich chemical sedimentary strata that 

trend north-northeast. Similar mineralized strata were mined 

from a small open cut and underground workings on the hill to 

the east. At the Sarita Mine, the 120 (haulage) and 160 levels 

on an unpublished (~late 1930s) map outline roughly circular 

areas, about 145 m in diameter, of rib assays that vary mostly 

between 0.1 and 1 opt Au (converted from dollar values at 

$35/oz). Based on descriptions in Eakle and others (1917) 

and Eakle and McLaughlin (1919), these levels apparently 

represent two of five juxtaposed, stratiform ore bodies. The 

ore bodies were as much as 10 m thick, indistinctly bounded, 

and within ~48 m of the surface. Ore reportedly consisted of 

dense to porous chalcedony and brecciated “chert” with seams 

of yellow-brown clay (Eakle and others, 1917; Eakle and 

McLaughlin, 1919; Jenkins, 1951). The Sarita open cut may 

coincide with one of the upper ore bodies, as two shafts and 

numerous small stopes occur south and west of the cut at the 

same or higher elevations (fig. 2).

Interpretation of Clastic and Hydrothermal 

Sedimentary Deposits

Based on examination of dump samples and limited 

mine exposures, mineralized strata at lower elevations, 

including the 120 haulage level, are predominantly coarse, 

unsorted volcaniclastic deposits that are variably silicified and 

leached. Leached to partially leached breccia clasts, ≤5 cm in 

dimension, are represented by voids and by skeletal aggregates 

of fine-grained quartz, alunite, and kaolinite that largely 

reflect original clastic texture. Some voids are encrusted with 

millimeter-sized alunite euhedral crystals and mixtures of 

alunite and kaolinite. Matrix of the volcaniclastic deposits 

consists of dense, fine-grained quartz with variable amounts of 

pyrite and alunite. Small amounts of enargite occur with iron 

oxides in fractures and in leached clast sites.

Mineralized strata at higher elevations, including the 

open cut, comprise two distinct bedding sets (a) sequences of 

alternating, relatively poorly to well-sorted volcaniclastic beds 

and thinly laminated brown and white beds (≤1 mm thick) of 

very fine-grained anhedral quartz with minor pyrite, hematite, 

enargite, and other minerals (fig. 9); and (b) sequences of 

thinly laminated brown and white beds of very fine-grained 

quartz ± Fe-Cu-S-O minerals that conformably and unconformably overlie coarser, relatively unsorted volcaniclastic beds 

(fig. 10). A conformable layer of relatively coarse-grained 

enargite+iron oxide and millimeter-sized, euhedral quartz 

quartz

pyrite

Fe-S-O-Cu-Sb-Al-Te

CuSb1.2As0.1Te1.8S3

Cu2.8Bi6.6S2 minor Se

Cu2.1Bi7.5S2 minor Se

~Cu5Sb1.7As0.6S2.8

Cu6.8Sb1.2As0.1Te1.8S3 Cu6Sb2As0.7Zn0.8Te0.7S3

~Cu5.2Sb1.2As0.8S3

200 μm
Masonic Mining District 23

crystals commonly occur between quartz bed sequences (such 

as sequence [a], described previously) and voids (leached 

clast sites). Enargite+iron oxide+fine-grained quartz also form 

millimeter-wide veins that cut thinly laminated, brown quartz 

beds and feather into layers of enargite+iron oxide-vuggy 

quartz. Sedimentary structures in thinly laminated, brown and 

white quartz beds include channel scour and fill, crossbedding, 

soft-sediment folds and slumps with sag micro-faults, and 

bed draping on clasts. Supersaturation textures in these beds 

are reflected by very fine-grained quartz and sulfide minerals, 

and by intergrowths of pyrite+hematite in hopper-like cubic 

euhedral crystals.

Based on sedimentary textures, structures, and 

stratigraphy, and on grain sizes and mineral modes, thinly 

laminated quartz beds in both bedding sets are interpreted to 

have precipitated from aqueous fluid (1) intermittently with 

volcaniclastic detritus; (2) conformably and unconformably 

on hummocky surfaces of unsorted and sorted volcaniclastic 

deposits; and (3) in depressions and spaces among blocks of 

silicified and leached, coarse volcaniclastic deposits. Paragenetically, the coarse volcaniclastic deposits were silicified 

following deposition of sorted volcaniclastic beds (such as 

sequence [a], described previously), and subsequently partially 

leached. These silicified and partially leached volcaniclastic 

strata were then eroded and slumped, creating channels in, 

and voids between, silicified and leached blocks that were 

filled with brown and white quartz beds (such as sequence [b], 

described previously), and with fine and coarse volcaniclastic 

detritus. The presence of angular leached dropstones in thinly 

laminated white and brown beds of sequence b (fig. 11) supports these paragenetic interpretations. Given the fairly steep 

present attitudes of these strata in the vicinity of New York 

Hill (described previously), slumping was most likely caused 

Figure 9. Image of a dump sample from the Masonic Mining 

District, Sarita Mine (elevation ~8,400 ft). Semiconformable set of 

beds that includes silicified and leached, coarse volcaniclastic 

detritus, variably sorted gravel and sand beds, and very finegrained white quartz beds. Subsequence a (described in text).

10 cm

Fig. 9

by uplift or tilting associated with faulting, and (or) with slope 

failure enhanced by deflation related to hydrothermal leaching 

of volcaniclastic strata. Vein and vug-filling quartz, enargite, 

and iron oxide that cut and conformably overlie, respectively, 

brown quartz beds constitute the youngest hydrothermal 

event that affected sequence b strata. Hydrous fluids that 

altered, leached, and mineralized the volcaniclastic deposits 

and chemical beds may have circulated in north-northwest 

to northeast-striking faults that contain the slightly younger 

mineralized breccias and veins. However, district-scale faults 

directly associated with Au-Ag-Cu deposits at the Sarita Mine 

and east of New York Hill are not evident at present levels of 

exposure.

Based on textures of mineral assemblages, alunite dates, 

and sulfur isotope compositions, the sulfide, telluride, sulfate 

and silicate minerals, and electrum in fault breccias and veins, 

and in sedimentary deposits, are hypogene. Some iron oxide 

minerals that occur with pyrite and enargite may also be 

hypogene. Iron oxide minerals that marginally replace pyrite, 

occur in fractures, and encrust void margins, are interpreted to 

have formed during weathering. These supergene iron oxide 

minerals and other minerals in sedimentary deposits that 

formed during weathering are not further characterized.

Mineral and Rock Compositions of Clastic and 

Hydrothermal Sedimentary Deposits

Thinly laminated, brown and white beds of very finegrained quartz at the Sarita Mine contain small amounts of 

very fine-grained pyrite, iron oxide, and enargite, in places 

intergrown with goldfieldite, a Cu-Sn-S mineral (with minor 

Se and Sb), a Bi-Se-Mo-S mineral (with minor Cu), and 

numerous Cu-Bi-As-Te-Sb-Pb-S-O minerals (fig. 12). Other 

quartz beds include complexly zoned pyrite(?) crystals that 

are pseudomorphically replaced by cores and concentric to 

partially annular zones of multielement phases. These euhedral 

crystals consist of (1) cores of iron oxide phases ±quartz with 

1–9.8 weight percent Si, S, Cu, and Sb, and with 1–3 weight 

percent Cu, As, Sb, Si, and S, and quartz with 1–3 weight 

percent Al, Fe, and S; (2) medial zones of Fe-Cu-Sb-As-Si-SCa-O, local Ba, W, Ag, Bi, and quartz; and (3) margins of iron 

oxides or multiphase margins with 1–9.8 weight percent Si, 

S, Cu, and Sb; one multiphase margin consists of iron oxides 

with <1–7 weight percent Cu, Sb, Si, and S, and Cu-Fe-SbAs-Si-Ca-O. Some pyrite remains in medial zones, along with 

minor barite, and in <1 μm inclusions in iron oxides with 

minor Cu and Se. These zoned euhedral crystals appear to be 

remnants of pyrite and Cu-As-Sb minerals, and other Se and 

Ag minerals that have been re-equilibrated in iron oxide and 

quartz-dominant zones. However, it is unclear if these zoned 

pseudomorphs were produced by hypogene or supergene processes, although the presence of sulfide minerals in the dense, 

finely laminated quartz beds suggests limited weathering.

Samples (collected from 2007 to 2012) of clastic and 

chemical (hydrothermal) sedimentary strata with enargite 

from Sarita Mine exposures and dumps contain elevated 
24 Gold-Silver Mining Districts, Alteration Zones, and Paleolandforms in the Miocene Bodie Hills Volcanic Field

Figure 10. Images of dump 

samples from the Masonic Mining 

District, Sarita Mine (elevation 

~8,400 ft). A, Silicified and leached, 

sorted gravel and sand-sized clastic 

beds unconformably overlain by 

channel-filling sets of very finegrained, brown quartz beds, and an 

unleached, coarse volcaniclastic 

deposit. Dark-gray beds contain 

pyrite. B, Very fine-grained white 

and brown quartz beds filling 

depressions in silicified and 

leached volcaniclastic deposits. 

C, Very fine-grained brown quartz 

beds filling fractures in silicified 

and brecciated trachyandesite, 

and overlain by a conformable 

vuggy layer of enargite+iron 

oxide(pyrite)+euhedral quartz. 

D, Very fine-grained brown quartz 

beds cut by a coarser-grained, 

quartz-enargite-iron oxide(pyrite) 

vein that is contiguous with a 

conformable layer of enargite+iron 

oxide (pyrite)-euhedral quartz. 

E, A bed of enargite+pyrite 

(~2 mm thick) within a set of very 

fine-grained, white quartz beds 

that fills a channel in brecciated 

trachyandesite. Subsequence b 

(described in text).

8 cm

enargite+FeOx (pyrite)-

euhedral quartz layer

enargite+FeOx (pyrite)

+quartz vein

◄

enargite+pyrite layer

◄

A

B C

D E

enargite+FeOx 

(pyrite)-euhedral 

quartz layer

4 cm 4 cm

4 cm

4 cm

Fig. 10
Masonic Mining District 25

Figure 11. Images of dump samples 

from the Masonic Mining District, Sarita 

Mine (elevation ~8,400 ft). Silicified 

and leached volcaniclastic deposits 

overlain by very fine-grained white and 

brown quartz beds with dropstones of 

leached trachyandesite. Subsequence b 

(described in text).

concentrations of Au (9.2–82.3 ppm), Ag (15–238 ppm), Bi 

(~57–3,110 ppm), Cu (~73–1,310 ppm), Pb (~98–216 ppm), 

Hg (~2–86 ppm), Se (~6–198 ppm), and ~100–860 ppm 

As, Ba, Sb, and Te. Other samples (collected in 1988) 

contain higher Hg (16–43 ppm), Ag (<300 ppm), and Sb 

(<4,600 ppm), in addition to elevated concentrations of 

As (174–3,107 ppm), and Te (<3,220 ppm; table 1-1). The 

elevated element concentrations in these bulk samples reflect 

the presence of numerous Cu-Bi-As-Te-Sb-Pb-Sn-Se-S-O 

minerals and also indicate the presence of additional Au- and 

Ag-bearing phases.

Other Minerals and Forms of Mineralization

Other minerals reported in the Masonic Mining District 

include tellurides, bismuthinite, argentite, bornite, and 

cinnabar (for example, Johnson, 1951). Although telluride 

minerals and bismuthinite were not identified in the samples 

examined, high concentrations of Te and Bi in bulk samples 

(table 1-1) imply the presence of telluride minerals and 

possibly bismuthinite in addition to the Te and Bi minerals 

imaged (figs. 6, 7, 8, 9). Other forms of mineralization in the 

district include (1) a 0.6–1.2-m-wide quartz vein in granodiorite at the Sunday Mine that contains sparse 3–4 mm crystals 

of galena and pyrite; and (2) discontinuous, <30-cm-wide 

quartz veins with minor pyrite and chalcopyrite in pre-Tertiary 

metavolcanic rocks southeast of the Success Mine near 

McMillan Spring. Other quartz veins occur in the granodiorite 

of Masonic Mountain. However, all of these veins differ in 

form, mineralogy, and structural control from the mineralized 

fault breccias and veins described previously.

Wall-Rock Alteration

Mineralized faults are bordered by dense to porous 

selvages of brecciated trachyandesite and granodiorite, or by 

trachyandesite flows that are extensively replaced by quartz, 

alunite, iron oxides (weathered pyrite), and lesser dickite, 

4 cm

4 cm

dropstones 

dropstones 

A

B

Fig. 11
26 Gold-Silver Mining Districts, Alteration Zones, and Paleolandforms in the Miocene Bodie Hills Volcanic Field

Figure 12. Secondary electron images of minerals in very fine-grained brown 

quartz beds from the Sarita Mine open cut, Masonic Mining District (fig. 2). 

A and B correspond to sample MAS07-3A (elevation ~8,300 ft). Imaged phases 

include quartz, a Cu-As-Sb-S mineral (~Cu5.2As1.3Sb0.6S2.9), a Cu-Te-Sb-As-S 

mineral (~Cu5.2Te1.3Sb0.8As0.3S2.4), and several Cu-Bi-As-Te-Pb-S-O minerals or 

mineral intergrowths.

Cu6.5Te1.6SbAs0.4S3

Cu5.2As1.5Sb0.4S2.9

Bi-As-Te-O Bi-As-Te-O Cu-Te-Sb-S-O

Cu-Sb-S-O

quartz

Bi-As-Te-O

100μm

quartz

Bi-As-Te-Pb-O

Cu5.4As1.3Sb0.6S3

Cu-O-S

Bi-As-Te-O

Cu5.1As1.3Sb0.5S3

Cu-S-Te-Sb-As-O

Cu5.4As1.2Sb0.8S3

Bi-As-Te-O

100μm

A

B
Masonic Mining District 27

pyrophyllite, and diaspore. Wide fault zones (for example, 

Maybell-Alton Jack Mine structures; fig. 3) are represented 

by resistant ridges as much as 15 m wide and 5 m high (fig. 5) 

in which primary rock textures in breccia clasts and flows are 

partly to entirely obscured. Narrower, meters-wide selvages 

of trachyandesite adjacent to other stoped fault breccias (for 

example, Mellor and Perrini Mines), largely retain primary 

igneous texture; phenocrysts and matrices in these selvages 

are replaced by pink to white mixtures of fine-grained alunite, 

kaolinite, pyrite, iron oxides after pyrite, and other clay 

minerals. With increasing distance from faults, illite and 

montmorillonite become the dominant replacement minerals. 

Wall-rock hydrothermal mineral associations are mainly 

the same as, and contiguous with, hydrothermal minerals in 

adjacent fault breccias that were stoped. Stoped fault breccias 

are distinguished by greater abundances of quartz, sulfide 

minerals, and precious metals.

Hydrothermal alteration associated with mineralized 

clastic and chemical sedimentary deposits is coextensive with 

those strata, as described previously. Lateral permeability of 

volcaniclastic deposits within the volcaniclastic-flow sequence 

on the west and northwest sides of Masonic Mountain enabled 

pervasive hydrothermal alteration; the quartz-alunite-pyritekaolinite alteration mineral association is fairly homogenous 

throughout these rocks. The presence of silicified and leached 

volcaniclastic deposits, clastic and chemical quartz beds, 

and Au-Ag-Cu-Fe sulfide minerals distinguish mineralized 

strata in the vicinity of New York Hill. Lateral boundaries of 

mineralized strata appear to be gradational, whereas vertical 

boundaries are largely stratigraphic, based on the absence of 

significant mineralization in underlying pre-Tertiary rocks. 

Volcaniclastic deposits and brecciated trachyandesite on 

Sarita Mine dumps, and lateral to mineralized strata at lower 

elevations, have been extensively replaced by quartz, alunite, 

and kaolinite, and cut by millimeter-wide veins composed of 

fine-grained quartz and alunite (fig. 13). On New York Hill, 

metavolcanic rocks in workings near the Sarita open cut have 

been altered to clay minerals, and granitic and metavolcanic 

rocks exposed on the hill to the east are extensively silicified 

and cut by planar and stockwork quartz veins. Density and 

competency contrasts between altered volcaniclastic-flow 

strata and subjacent pre-Tertiary rocks, and slopes oversteepened by fault displacement, caused masses of altered 

rocks tens of meters in dimension to slide down the north side 

of New York Hill (fig. 2).

Sulfur Isotope Compositions and Equilibrium 

Temperatures

Most sulfur isotope values (δ34S) for enargite, pyrite, and 

luzonite vary from −7.9 to −12.2 ‰, and values for alunite 

vary from 13.4 to 19.9 ‰ (table 2). No clear compositional 

differences exist between the two forms of mineralization 

(breccia and vein deposits in fault zones; clastic and 

hydrothermal sedimentary deposits). One higher δ34Senargite

value (0.2 ‰), and one lower δ34Salunite value (7.1 ‰; table 2) 

presumably reflect sample impurity because both minerals 

occur in sulfide-sulfate mixtures.

The relatively low δ34S sulfide and relatively high δ34S 

sulfate values of most samples are consistent with disproportionation of magmatic SO2

 into H2S and SO4

2- (Rye, 2005) 

during the formation of both deposit types. Disproportionation 

occurs when SO2 derived from magma degassing condenses in 

overlying groundwater at temperatures <400 °C:

2SO2 + H2O = H2S + SO4

2-+ 2H+

Groundwater acidified by this reaction decomposes silicate 

rocks to hydrothermal mineral assemblages dominated by 

quartz, alunite, and pyrite. K+, Fe2+, and Al3+, solubilized during silicate mineral decomposition, react with aqueous SO4

2- 

and H2S to form alunite and pyrite with markedly different 

sulfur isotope values.

Calculated sulfur isotope equilibrium temperatures 

(δ34Ssulfide- δ34Ssulfate) of coexisting pyrite, enargite, and alunite 

in samples from the Red Rock and Sarita Mine dumps are 

228, 231, and 238 °C, and 192 °C (all calculations are based 

on pyrite-alunite fractionation; table 2; Vikre and Henry, 

2011). Calculated sulfur isotope equilibrium temperatures 

of coexisting pyrite and alunite from the lower dump of the 

Pittsburgh-Liberty Mine, from a small mine dump in Masonic 

Gulch (“aspen grove” mine), and from the lower Perrini Mine 

dump, are 218, 198, and 188 °C, respectively (table 2).

Figure 13. Image of a dump sample from the Masonic Mining 

District, Sarita Mine (elevation ~8,200 ft). Trachyandesite of 

Masonic that has been altered to quartz, alunite, kaolinite, and 

pyrite, brecciated, and cemented by veins of fine-grained quartz 

and alunite.

5 cm

Fig. 13
28 Gold-Silver Mining Districts, Alteration Zones, and Paleolandforms in the Miocene Bodie Hills Volcanic Field

Aster Imagery

ASTER imagery of the Masonic Mining District 

(Rockwell, 2010) shows a fairly uniform cluster of pixels 

that corresponds to kaolinite, montmorillonite, illite, and 

locally, quartz on Masonic Mountain, and on granitic rocks 

and trachyandesite of Masonic to the northeast to Masonic 

Gulch. Several clusters of pixels that correspond to alunite 

and kaolinite are coincident with the Sarita Mine and altered 

slide blocks on the north slope of New York Hill, and on the 

hill ~ 0.5 km east of New York Hill. Smaller and more diffuse 

groups of alunite ± kaolinite pixels are coincident with the 

Red Rock Mine, the Pittsburg-Liberty Mine, the north slope 

of Masonic Gulch above (lower) Masonic town site, and the 

Lakeview Mine. Four relatively dense clusters of alunite 

pixels are coincident with the landslides north of the Lakeview 

Mine (Tls, fig. 2).

Short Wave Infrared (SWIR) Spectra

SWIR spectra of hydrothermally altered and mineralized 

hand samples correspond to the same minerals identified 

by field and petrographic examination. Trachyandesite of 

Masonic on the Success, Chemung, Maybell-Alton Jack, 

and Perrini Mine dumps contains alunite, kaolinite, dickite 

and lesser pyrophyllite and illite. Granodiorite and metavolcanic rocks on New York Hill, and on Sarita and PittsburgLiberty Mine dumps, contain alunite, kaolinite, dickite, and 

lesser pyrophyllite.

Host Rock and Alteration Mineral Ages

The granodiorite that encloses mineralized faults is 

~98 Ma (Robinson and Kistler, 1986). Based on 40Ar/39Ar 

ages of plagioclase and hornblende in unaltered flows and 

domes, trachyandesite of Masonic is ~15–14 Ma (table 1). The 

volcaniclastic-flow sequence that hosts Au-Ag-Cu mineralization in the central and southern parts of the district has not 

been directly dated; however, stratigraphic relations indicate 

that the age of the volcaniclastic-flow sequence is probably 

close to the youngest ages determined for trachyandesite of 

Masonic (~14 Ma), and could be as young as 13.3 Ma, the age 

of alunite in clastic and chemical sedimentary deposits at the 

Sarita Mine. Locally altered porphyritic trachyandesite domes 

in the northern part of the district are ~13.5–13.4 Ma (table 1). 

Unaltered andesite of Lakeview Spring in the southwestern 

part of the district is ~12.9 Ma (fig. 2; table 1).

The 40Ar/39Ar dates of hydrothermal alunite mostly 

consist of two groups. Alunite in the volcaniclastic-flow 

sequence in the southwestern part of the district (Sarita, Red 

Rock, and Chemung Mines) is ~13.4–13.3 Ma; one alunite 

date near the Success Mine is 13.6 Ma (table 1). With the 

exception of the 13.6 alunite date, the older alunite dates are 

similar to the dates of alunite in the Red Wash-East Walker 

River alteration zone (table 1); they are slightly younger than 

the ages of porphyritic trachyandesite domes (trachyandesite 

of Masonic Gulch) north of the district. Alunite in fault 

breccias in granodiorite and trachyandesite in the northern part 

of the district is ~13 Ma (Pittsburgh-Liberty, Maybell-Alton 

Jack, and Perrini Mines; table 1), and is indistinguishable from 

the age of andesite of Lakeview Spring when analytical error 

is considered.

Red Wash-East Walker River 

Alteration Zone

Location

Secs. 2, 31, 32, Tps. 6 and 7 N., R. 26 E. (incompletely surveyed); secs. 31, 32, 33, 34, 35, 36, T. 7 N., R. 26 E., Lyon 

County, Nevada (fig. 1)

Definition

The Red Wash-East Walker River alteration zone 

(RW-EWR AZ; fig. 14) is the western part of a larger, 

approximately west-east-trending alteration zone between 

the East Walker River and Fletcher Valley. The western 

part of the zone described here is bordered on the west and 

northeast by the East Walker River, and occurs entirely in 

volcaniclastic strata and lavas of trachyandesite of Masonic. 

In the vicinity of Red Wash, the alteration zone bifurcates 

with (1) an east-northeast-trending branch that extends across 

meanders of the East Walker River into Fletcher Valley, and 

(2) a more diffuse branch that extends south along Red Wash 

and southeast of Red Wash for ~2 km. To the north, the zone is 

covered by Tertiary and Quaternary sediments and colluvium 

(in part, Tfg, Ts, and Tg; fig. 14; John and others, 2012). The 

minimum dimensions of the western part of the zone are 

~12 km west-east and <1–6 km north-south (~22 km2 ; figs. 1, 

14). The entire zone from the East Walker River to Fletcher 

Valley covers at least 30 km2.

The approximately west-east-oriented, central part of the 

zone consists of volcaniclastic strata and lesser trachyandesite 

lavas that have been pervasively altered to quartz, alunite, 

and other minerals described below. Numerous small areas of 

quartz-alunite-kaolinite-altered rocks occur within 1 km south 

and north of the central part of the zone. Because of mapping 

scale and alteration zone definition, some of these outliers are 

not shown on figure 14. Between contiguous quartz-alunitekaolinite-altered rocks of the zone and the Masonic Mining 

District (south of the area of fig. 14), extensive volumes of 

trachyandesite of Masonic have been partially altered to 

chlorite, sericite, clay minerals, calcite, and pyrite, which have 

mostly weathered to iron oxide minerals.
Figure 14. Geologic map of the Red Wash-East Walker River alteration zone, Lyon and Mineral Counties, Nevada, and Mono County, California.

EX

4035

FanglTerraFluvioEurekTrach

Man

Trach

VolcTracTrac

Areas 

qutran(fi

ContaFault—

Hig

BeddFoliatMine AditColor Analy40Ar/39

(ta

Qfg

Tg

Ts

Tev

Tamg

Tmau

Tma

Tmai

0 0.50 0.5

1 MILE

1 KILOMETER

Tma

Tamg

Tmau

Tmau

Tmau

Tmau

Tmau

Tmau Tmau

Tmau

Tmau

Tg

Ts

Ts

Qfg

Tg

Tg Tma

Tma

Tma

Tma

Tmau

Tmaidome

Tev

Tev

Tev

Tamg

Tma

Base modified from U.S. Geological SurveySweetwater Creek, Nev.-Calif., and The Elbow, Nev.-Calif., 1989, 1:24,000

Sonoma

Canyon

Gulch

Masonic

hill 6696

13

28

29

7

area of figure 3

MAS10-37

MAS10-36

MAS10-74

RWEWR12-1

Tma

Tev

Tmau

75 bx dike

MAS10-53

MAS10-53A

MAS10-52

MAS10-51

MAS10-54

MAS10-50

RW08-3

5-10

10-15

MAS10-55A

10-20

RW08-2 MAS10-60

MAS10-38

MAS10-39

MAS10-61

MAS10-40

MAS10-43

MAS10-44

MAS10-45

MAS10-46

MAS10-47

15

14

4

16

Wash

East Walker River

fanglomerate on ridges Tma in drainages

Red

N
30 Gold-Silver Mining Districts, Alteration Zones, and Paleolandforms in the Miocene Bodie Hills Volcanic Field

History and Production

Despite its relatively large size, no production is recorded 

for the RW-EWR AZ. Approximately 15 scattered and small 

prospect pits and trenches have been excavated, mostly in and 

adjacent to resistant exposures of volcaniclastic rocks and 

flows of trachyandesite of Masonic that are replaced by quartz, 

alunite, kaolinite, pyrite (iron oxide), and minor pyrophyllite. 

The workings presumably sought precious metals or Hg. 

Drill roads and drill cuttings, probably from exploration for 

precious metals ~1980–2000, are evident in secs. 5, 6, T. 7 N., 

R. 26 E. between Masonic Gulch and Sonoma Canyon, and in 

secs. 34, 35, T. 7 N., R. 26 E. southeast of the confluence of 

Red Wash and the East Walker River. Exploration leases for 

alunite, uranium, and clay minerals were filed in the 1970s 

over parts of the alteration zone (Gilbert, 1976).

Stratigraphy

The RW-EWR AZ is in volcaniclastic strata and 

trachyandesite flows of trachyandesite of Masonic (fig. 14). 

Volcaniclastic strata are predominantly debris flows that are as 

much as ~60 m thick, and are nearly completely replaced by 

hydrothermal minerals. Less altered (propylitized) debris flows 

in one exposure consist of greenish-gray, rounded, and poorly 

sorted blocks of trachyandesite (<0.7 m in dimension) in a 

fine-grained matrix of comminuted andesite (fig. 4). Bedding, 

reflected approximately by outcrop orientation, strikes N30°E 

and dips 10–20°NW. Beneath and south of the volcaniclastic 

deposits are green to greenish-gray trachyandesite flows that 

have been variably altered to chlorite, mica-clay minerals, 

calcite, and pyrite (iron oxides).

Adjacent north-south and west-east alignments of 

porphyritic trachyandesite domes (trachyandesite of Masonic 

Gulch) occur ~1–1.5 km south of the central part of the 

alteration zone at the northern margin of the Masonic Mining 

District (fig. 14). The domes rise tens of meters above adjacent 

flows of trachyandesite of Masonic that have been variably 

altered to chlorite, mica-clay minerals, calcite, and pyrite (iron 

oxides). East of Masonic Gulch, the domes are partly overlain 

by Eureka Valley Tuff (Tev) and perched terrace gravels (Tg). 

Based on four 40Ar/39Ar ages of plagioclase, the domes are 

13.5–13.4 Ma, ~ 0.5 m.y. younger than the trachyandesite 

of Masonic lavas that they intrude (table 1). The porphyritic 

domes consist of 12–20 volume percent plagioclase crystals 

(1–4 mm), 3–5 volume percent subhedral and euhedral 

hornblende and clinopyroxene (0.5–3.5 mm), and <1 volume 

percent subhedral biotite (0.5–1.2 mm) in a pale-tan to 

olive-green matrix composed of partly devitrified glass, 

submillimeter-sized plagioclase, hornblende, biotite, pyroxene, 

and small amounts of apatite. Parts of the domes are altered to 

mica-clay minerals and pyrite (iron oxides).

Semiconsolidated gray- to dark-gray, fluviolacustrine 

sediments cover the north side of the alteration zone between 

Sonoma Canyon and East Walker River (Ts, fig. 14). These 

relatively well-sorted and distinctly bedded, coarse sands, 

sands, and silts are distinguished from other basin-fill and colluvial deposits by color, sorting, bedding, and sparse, rounded 

heterolithic clasts that are mostly <10 cm in dimension. Gray 

sediments west of Masonic Gulch are overlain by thin (meters 

thick) gravel deposits consisting of rounded heterolithic 

cobbles and lesser boulders that partially cover several of the 

low, flat-topped ridges of trachyandesite south of the zone (Tg, 

fig. 14). Slopes of most north-south drainages that flank these 

ridges are partially covered with cobbles, which represent 

remnants of more extensive colluvial terraces that accumulated 

south of a more contiguous west-east landform of silicified 

volcaniclastic deposits. The gray sediments and dissected 

gravel terraces, together with west-east and northeast-trending 

normal faults between the Masonic Mining District and the 

alteration zone, suggest (1) uplift of Masonic Mountain and 

the district relative to the alteration zone since 11 Ma, the 

approximate age of the oldest basin-fill of Fletcher Valley 

(table 1); and (2) deposition during at least two hydrologic 

regimes based on differing clast size and sorting within the 

sedimentary deposits.

Structure

Structures that may have channeled hydrothermal fluids 

into permeable volcaniclastic strata and trachyandesite to form 

the RW-EWR AZ are evident at contrasting scales. Veins and 

crosscutting breccias, described below, are common within the 

alteration zone, but most can be traced for only a few meters 

to a few tens of meters and are not aligned. On the scale of 

the entire zone, linear and slightly curvilinear structures are 

conspicuous on color air photos and, to a lesser extent, on 

ASTER imagery (Rockwell, 2010). Within the alteration zone 

these lineaments trend predominantly west-east and northwestsoutheast (figs. 14, 15). Because of their linearity, these 

structures most likely represent postalteration faults, but little 

to no stratigraphic displacement can be demonstrated. A northsouth lineament along Red Wash may displace the zone east 

of Red Wash to the north, although evidence of stratigraphic 

offset also is minimal (John and others, 2012). Furthermore, 

silicified carapaces of volcaniclastic strata, which cap most 

uplands in the RW-EWR AZ, are not significantly displaced 

vertically, nor do they appear to be displaced laterally. The 

lateral dimensions of the zone are probably controlled by a 

series of en echelon west-east faults with minor vertical and 

lateral displacement, and by local breccias, which were likely 

conduits for hydrothermal fluids.

Hydrothermal Alteration

Topographic definition of the RW-EWR AZ is reflected 

by the west-east series of flat-topped to rounded landforms 

with resistant, silicified carapaces that are flanked by 

recessive-weathering slopes of clay-mica-pyrite-altered 

volcaniclastic strata and trachyandesite flows. The farthest 
Red Wash-East Walker River Alteration Zone 31

western part of the alteration zone consists of low, en echelon 

ridges and small spires, mostly meters in dimension, of silicified volcaniclastic strata and trachyandesite that commonly 

are brecciated and cemented by quartz and alunite. These 

resistant ridges and spires in part occur in clay-mica-pyritealtered trachyandesite and locally protrude through overlying 

Tertiary-Quaternary sedimentary deposits. Outcrops of the 

silicified strata vary in color from gray to mottled, intense 

red-brown and beige, depending on iron oxide abundance, and 

have hackly to dense, smooth surfaces. In contrast, clay-micapyrite-altered volcaniclastic strata and trachyandesite are beige 

to reddish-brown with rough surfaces, although most exposures have largely degraded into fine talus.

Silicified volcaniclastic strata and trachyandesite flows 

consist of very fine-grained aggregates of quartz and alunite, 

and lesser pyrophyllite, dickite, and kaolinite (figs. 14, 15). 

Alunite and clay minerals also occur in breccia matrices, and 

in irregular and discontinuous, millimeter-thick veins, usually 

with quartz. At least three sets of crosscutting breccias and 

veins are evident. The youngest breccia matrices are locally 

vuggy, with vugs encrusted by submillimeter-sized, euhedral 

quartz, and rarely by euhedral alunite. The interpreted age 

of alteration, ~13.3 Ma (table 1), is based on the ages of 

relatively coarse-grained matrix alunite (samples RW08-1 and 

MAS10-55, fig. 14) of the youngest breccias. Older veins and 

breccia matrices consist of fine-grained to microcrystalline 

aggregates of quartz ± alunite. Breccia clasts are gray to beige, 

and consist of very fine-grained aggregates of quartz ± alunite ± pyrite. Some relict trachyandesite clasts comprise very 

fine-grained gray quartz with casts of leached phenocrysts. 

On recessively weathered slopes adjacent to carapaces, 

breccia clasts and matrices consist of quartz+clay-mica 

minerals ± pyrite.

Minor Elements in Rocks

Although the exploration workings are in or near the 

most intensively altered rocks, they have exposed no obvious 

evidence of element concentrations. Most minor element 

analyses of 26 rock samples indicate zero to somewhat 

elevated concentrations of metals and other elements 

(table 1-2). Samples of intensely altered rocks contain 

variably elevated concentrations of Hg (1–5.2 ppm), As 

(205; 477 ppm), Bi (1–7 ppm), Co (~ 6; 30 ppm), Cu (148; 

189 ppm), Mo (21–168 ppm), Pb (66–258 ppm), and Te 

(~1–7 ppm). Elevated concentrations of Ba, W, Se, Sr, Cr, 

Mn, and Ni occur in individual samples. Samples with sulfur 

abundances >1 volume percent and >1,000 ppm Ba contain 

alunite, pyrite, and barite. 

Sulfur Isotope Composition

The sulfur isotope value (δ34S) of matrix alunite in a 

dated sample (RW08-1) of brecciated and silicified volcaniclastic strata is 20.6 ‰ (table 2). This δ34S value is consistent 

with disproportionation of magmatic SO2 (Rye, 2005) as the 

fundamental process responsible for pervasive quartz-alunitepyrite (iron oxides) alteration of the volcaniclastic strata and 

trachyandesite flows.

ASTER Imagery

ASTER spectra of the RW-EWR AZ (fig. 15; Rockwell, 

2010) show that an extensive quartz-alunite ± pyrophyllite 

association spatially coincides with erosionally resistant, 

stratiform carapaces of volcaniclastic strata that form the westeast alignment of landforms. Pixels interpreted as representing 

kaolinite and montmorillonite are within and north of the 

main area of quartz-alunite-pyrophyllite-altered rocks. Many 

of these pixels are coincident with Tertiary-Quaternary 

sedimentary deposits that contain altered clasts, but exposures 

of clay-altered trachyandesite beneath sedimentary deposits in 

drainages, and in Red Wash, indicate that, for the most part, 

the pixels represent bedrock. East of Red Wash, kaolinitemontmorillonite-altered rocks overlap and extend south of 

the area of quartz-alunite-pyrophyllite-altered rocks. These 

alteration patterns continue east-northeast into Fletcher Valley.

SWIR Spectra

SWIR analyses of representative samples from the 

RW-EWR AZ confirm the presence of alunite, pyrophyllite, 

dickite, kaolinite, and montmorillonite in and adjacent to the 

resistant stratiform carapaces of altered volcaniclastic strata.

Hydrothermal Mineral Ages

Within the RW-EWR AZ, alunite in the matrices of silicified breccias near Masonic Gulch, and near Sonoma Canyon, 

has 40Ar/39Ar dates of 13.34 ± 0.035 Ma and 13.27 ± 0.02 Ma, 

respectively (fig. 14; table 1). These alunite dates are analytically indistinguishable from the dates of alunite at the Sarita, 

Red Rock, and Chemung Mines in the Masonic Mining 

District ~5 km south of the RW-EWR AZ. They are slightly 

younger than the ages of porphyritic domes of trachyandesite 

of Masonic Gulch (13.5–13.4 Ma; table 1) in the northern part 

of the Masonic Mining District, ~1–1.5 km south of the central 

part of the alteration zone (fig. 3).
0 1 2 

0 1 2 3 

Clay-bearing assemblages Kaolinite1 Kaolinite ± sericite Kaolinite ± sericite1 (high-albedo surfaces with minor and (or) impure kaolinite, often supergene

Montmorillonite/smectite, or low-abundance sericite

1Kaolinite-bearing assemblages may be misidentified in 

areas with sparse, dry vegetation ± sericite or montmorillonite

Sulfate-bearing assemblages

Possible prophyllite (± alunite)2

Alunite (± prophyllite)2Natroalunite, or alunite and minoAlunite and kaolinite2Jarosite ± gypsum, or ferric iron aGypsum ± clays

2These assemblages may represen

clay/mica and dry vegetation, or arinstability related to low or high sur

EXPLANATION

M

a

s

o

n ic

Gul

c h

East 

Walker 

River 

Red 

Wash East Walker River

Red Wash-East Walker River alteration zone Red Wash-East Walker River alteration zone

S

o

n

oma

C

a

nyo

n

East 

Walker 

River 

Red 

Wash East Walker River

S

o

noma

C

a

n

yon

Red Wash-East Walker River alteration zone

BA

M

a

s

o

n

i

c

Gulch

A

A'

A

A'
East Brawley Peak Alteration Zone 33

East Brawley Peak Alteration Zone

Location

Secs. 24, 25, 36, T. 5 N., R. 27 E.; secs. 30, 31, T. 5 N., R. 28 

E., Mineral County, Nevada; secs. 4, 5, T. 4 N., R. 28 E., Mono 

County, California (fig. 1)

Definition

The East Brawley Peak alteration zone (EBP AZ; fig. 16) 

is southwest of the adjacent Aurora Mining District, and lies 

mostly north of the California-Nevada border. It has a northsouth dimension of ~4.5 km, an average west-east dimension 

of ~1.7 km (~7.7 km2), and is approximately centered on East 

Brawley Peak. The alteration zone is underlain predominantly 

by trachyandesite of Aurora, bordered to the west by trachyandesite of West Brawley Peak, and bordered to the north by 

rhyolite of Del Monte Canyon and rhyolite of East Brawley 

Peak (fig. 16). To the northeast and south, quartz-alunitepyrite-dominant mineral assemblages of the EBP AZ grade 

into propylitically altered trachyandesite of Aurora. To the 

east, the EBP AZ adjoins a west-east-aligned zone of variably 

altered Tertiary and pre-Tertiary rocks that includes the Spring 

Peak sinter (fig. 16). Temporal relationships of the Spring Peak 

sinter, the EBP AZ, and the Aurora Mining District, have not 

been determined by geochronology.

History and Production

No production is recorded from the EBP AZ. A drilling 

access road to the top of East Brawley Peak was constructed 

in the 1980s (?), and at least one hole was drilled from a site 

~ 0.2 km north of the summit. Several shallow bulldozer 

excavations near the summit may predate the drill access road 

and site.

Stratigraphy

Most of East Brawley Peak is mantled by slope wash 

consisting of strongly silicified rocks exposed on and near the 

summit, and on the hill ~1 km south of the summit. Based on 

relict textures in silicified and subjacent altered rocks, and 

on exposures in the Aurora Mining District, the EBP AZ is 

underlain entirely by trachyandesite of Aurora. The trachyandesite of Aurora forms a series of moderate-volume lava flows 

and associated laharic debris flows and volcaniclastic deposits 

similar to those included in the trachyandesite of Masonic. The 

abundance of debris flows interbedded with compositionally 

equivalent lava flows, both intruded by numerous small, 

intermediate-composition intrusions, suggests that these 

rocks comprise a stratovolcano centered near the Aurora 

Mining District. Trachyandesite of Aurora is a medium- to 

pale-gray, moderately porphyritic trachyandesite, and includes 

andesite and trachydacite. It contains about 3–42 volume 

percent phenocrysts, trachytically layered in some places, 

of plagioclase, distinctive 1–5 mm hornblende euhedra, and 

trace amounts of clinopyroxene and biotite set in a moderately 

devitrified groundmass.

K-Ar ages of trachyandesite of Aurora range from 15.8 

to 13.8 Ma (Silberman and McKee, 1972; Kleinhampl and 

others, 1975). More precise 40Ar/39Ar dates of hornblende and 

plagioclase are 13.13–12.58 Ma (table 1). Based on 40Ar/39Ar 

dates of plagioclase, unaltered trachyandesite of West 

Brawley Peak, which overlies altered rocks of the EBP AZ, is 

11.51–11.32 Ma (table 1; John and others, 2012).

Structure

Breit (2000) attributed structural control of the EBP 

AZ to a N75°W-striking “left-stepping dilational jog in a 

N45°W-striking strike-slip fault near the summit of East 

Brawley Peak.” This fault pair is defined by the distribution 

of silicified trachyandesite, N75°W-striking quartz veins, and 

high temperature, saline fluid inclusions in quartz fragments in 

veins atop East Brawley Peak that may have been transported 

upward from a deep source. On a regional scale, the northsouth Esmeralda vein, which trends into the EBP AZ, other 

N40–70°E-trending veins in the Aurora Mining District, 

and the structures atop East Brawley Peak, may be related to 

right lateral faults produced by N40–45°W-oriented shear 

(Sylvester, 1988; Breit, 2000). However, northwest-trending 

structures with significant oblique displacement have not been 

recognized elsewhere in the Bodie Hills.

Figure 15. (Facing page) A, Advanced Spaceborne Thermal Emission and Reflection 

Radiometer (ASTER) imagery of the Red Wash-East Walker River alteration zone (after Rockwell, 

2010). B, Image showing view to the northeast of the alteration zone.
Figure 16. Geologic map of the East Brawley Peak alteration zone, Mineral County, Nevada, and Mono County, California, modified from Breit (2000) and John and others (2012). Taa Tach Qa Qa West Brawley Peak East Brawley Peak AURORA MINING DISTRICT Si Qac Qac Qac Qa figure 48 figure 20 38°14 38°15 38°16 118°55 118°54

0 0.50 0.5

1 MILE

1 KILOMETER

MINERAL COUNTY

MONO COUNTY

Base modified from U.S. Geological SurveyKirkwood Spring, Calif.-Nev. and Aurora, Nev.-Calif., 1989, 1:24,000

11.95 ± 0.02 Ma;

alunite

Trsp

Tadi

Tadi

Trsp?

Tach

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Qa

Qa

Qa

Qt

Qt

Qt

Qt

Qt

Qt

Qa

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Taa

Taa

Taa

Taa

Treb

Twba

Twba

Twba

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Trsp

Trsp

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Tach

Trsp

Twba

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Trdc

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Alluvium Aurora V

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Bodie H

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Contact—Fault—D

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Color ai

40Ar/39Ar 

119°15' 

38°25'38°15'38°05'

Bridgeport

M
East Brawley Peak Alteration Zone 35

A west-east lineament that is conspicuous on color aerial 

photography (CAP lineament; fig. 16) trends through the EBP 

AZ and is coincident with the southern border of the west-east 

zone of altered rocks that includes the Spring Peak sinter 

(fig. 16). Although stratigraphic displacement of Miocene and 

Pliocene volcanic rocks along this lineament has not been 

recognized, Pliocene trachyandesite of Cedar Hill straddles the 

lineament. This relationship suggests that, if the lineament is 

a fault, then displacement along it is pre-Pliocene. High-angle 

displacement along this lineament may have contributed 

to relief and the relatively large amount of erosion of the 

Aurora Mining District.

Hydrothermal Alteration

According to Breit (2000), hydrothermal alteration 

minerals within the EBP AZ are vertically zoned. Quartzalunite-kaolinite-pyrite-altered trachyandesite and vuggy silica 

(presumably hydrothermal and residual quartz) are dominant 

between 8,050 and 8,800 ft elevation, and pervasively silicified and brecciated trachyandesite is dominant from 8,800 to 

9,400 ft elevation (summit of East Brawley Peak). Laterally 

adjacent to quartz-alunite-kaolinite-altered trachyandesite on 

East Brawley Peak, are zones of “intermediate argillic alteration” (Breit, 2000) and propylitically altered trachyandesite.

Alteration mineral assemblages within the EBP AZ 

appear to grade to the north into propylitically altered 

trachyandesite of Aurora in the Aurora Mining District, but the 

transition occurs on slopes mantled by silicified trachyandesite 

shed from the summit of East Brawley Peak. Hydrothermal 

mineral ages indicate that the Aurora veins are younger than 

the EBP AZ. Detailed mapping, geochronology, and paragenetic examinations required to determine the relationship of 

the EBP AZ to veins of the Aurora Mining District, and to the 

Spring Peak alteration zone, have not been completed.

Minor Elements in Rocks

Breit (2000) reported elevated Ti (>1 weight percent) 

and Zr in samples of pervasively silicified trachyandesite, and 

somewhat elevated concentrations of Au, Ag, As, Sb, Hg, Cu, 

Pb, Bi, Mo, Se, Te, and Ba in a small percentage of samples 

categorized as argillized, argillized and iron-stained, propylitized, silicified, silicified and iron-stained, and vein rock. This 

geochemical characterization was derived from three sets of 

samples collected during 1967–68, 1988, and 1992 that were 

analyzed by different methods.

ASTER Imagery

ASTER imagery (Rockwell, 2010) of the EBP AZ 

shows clusters of pixels on East Brawley Peak and on the 

hill to the south that represent quartz-alunite ± pyrophyllite 

and lesser kaolinite. The clusters are spatially coincident 

with silicified trachyandesite of Aurora that contains variable 

amounts of alunite. Scattered pixels that represent sericite are 

distributed near the south and southeast margins of the zone. 

On the north-northeast side of the alteration zone, quartzalunite ± pyrophyllite-altered trachyandesite and kaolinitealtered trachyandesite terminate rather abruptly against 

relatively dense pixelation that represents sericite-altered 

trachyandesite of Aurora in the Aurora Mining District.

SWIR Spectra

SWIR spectral analyses of rock samples within the 

EBP AZ show that recessively weathered greenish, altered 

trachyandesite of Aurora in the saddle on the summit of 

East Brawley Peak contains montmorillonite. Veins and 

breccia matrix in silicified trachyandesite north of the summit 

consist of dickite; adjacent trachyandesite wall rocks contain 

dickite and kaolinite. Trachyandesite of Aurora and rhyolite 

of East Brawley Peak(?), north and south of the summit, 

contain alunite, dickite, kaolinite, montmorillonite, illite, and 

illite/montmorillonite.

Fluid Inclusion Microthermometry and 

Composition

Breit (2000) described narrow cryptocrystalline quartz 

veins near the summit of East Brawley Peak that contain 

quartz fragments with four populations of fluid inclusions, 

and silicate melt inclusions. One type of inclusion containing 

halite and other daughter minerals homogenized to liquid 

at T≥470 °C; another type contains liquid CO2. According 

to Breit (2000) high homogenization temperatures and the 

presence of silicate melt inclusions suggest that these quartz 

fragments are magmatic in origin and were transported upward 

from an unexposed intrusion.
36 Gold-Silver Mining Districts, Alteration Zones, and Paleolandforms in the Miocene Bodie Hills Volcanic Field

Hydrothermal Mineral Ages

Breit (2000) reported K-Ar and 40Ar/39Ar dates 

of 13.7 ± 0.5 Ma and 12.34 ± 0.04 Ma, respectively, for 

alunite from East Brawley Peak. The 40Ar/39Ar date of 

11.954 ± 0.016 Ma (sample AUR10-3, table 1) was obtained 

for alunite on the south slope of East Brawley Peak (approximately the same location as the samples dated by Breit). This 

latter alunite occurs as millimeter-sized crystals that encrust 

fractures and irregular pockets in silicified and leached 

trachyandesite of Aurora. The alunite dates are older than 

40Ar/39Ar dates of K-feldspar in veins in the Aurora Mining 

District, which range in age from 10.5 to 10.0 Ma (table 1).

Sawtooth Ridge Alteration Zone

Location

Secs. 12, 13, T. 5 N., R. 27 E., Mineral County, Nevada (fig. 1)

Definition

The Sawtooth Ridge alteration zone (SR AZ; fig. 17) 

is mostly in rhyolite of Aurora Creek (11.18 ± 0.01 Ma, 

table 1; John and others, 2012) that has been altered to quartz 

and opaline silica, alunite, and clay minerals. The SR AZ 

covers ~2 km2 immediately north of Aurora Creek and 

adjoins the Aurora Mining District to the south and east. It is 

distinguished from alteration of rhyolite of Aurora Creek in 

the northern part of the Aurora Mining District by alteration 

mineral associations, by age (11.105 ± 0.018 Ma, table 1), and 

by the presence of Aurora district veins (~10–10.5 Ma, table 1) 

in rhyolite of Aurora Creek east of the Aurora cemeteries, but 

not in altered rocks of the zone to the west.

History and Production

No production is recorded from the SR AZ. A prospect 

near the north edge of the zone was excavated in brecciated 

rhyolite with dense iron oxide matrix. Roads in the southern 

part of the zone, west of the Aurora cemeteries, apparently 

provided access to drill sites, but most have been partly 

reclaimed and no drill cuttings were identified. A small open 

cut and shaft in rhyolite of Aurora Creek east of the SR 

AZ expose narrow quartz veins that most likely represent a 

northern extension of Aurora district veins.

Stratigraphy

The rhyolite of Aurora Creek consists of coalescing 

domes and proximal flows of flow-banded rhyolite and subordinate lithic-rich tuff that are gray where unaltered and beige 

to white where altered (fig. 17). The rhyolite is overlain to the 

west and northeast by trachyandesite of Del Monte (11 Ma), 

to the southwest by nearly coeval rhyolite of Del Monte 

Canyon (11.2 Ma; John and others, 2012), and to the north and 

northeast by late Pleistocene trachyandesite of Aurora Crater 

(north and northeast of the area of fig. 16). Rhyolite of Aurora 

Creek overlies trachyandesite of Aurora (~13.1–12.6 Ma; 

table 1), which is extensively exposed immediately south of 

the SR AZ in the Aurora Mining District. Trachyandesite of 

West Brawley Peak (~11.5 Ma, table 1) crops out in the north 

part of the alteration zone and is locally clay-altered.

Structure

No faults transect rhyolite of Aurora Creek within the 

area of figure 17, nor can any be demonstrably projected 

into the SR AZ from available geologic maps (John and 

others, 2012).

Hydrothermal Alteration

Alteration of rhyolite of Aurora Creek within the SR 

AZ is most pervasive in an area bounded by Aurora Creek to 

the south and extending about 2.5 km north of Aurora Creek 

(fig. 17). In this area, rhyolite is variably altered to quartz and 

opal, and lesser amounts of alunite, kaolinite, montmorillonite, 

and illite. Sparse feldspar and biotite phenocrysts commonly 

are replaced by sericite and clay minerals. The most intensely 

altered rocks are flow breccias or breccias related to dome 

emplacement on the ridge top north of Aurora Creek (fig. 17). 

The high point on that ridge was known as “Mt. Chalcedony” 

during the main period of production in the Aurora Mining 

District (Wasson, 1878). On Sawtooth Ridge between Mt. 

Chalcedony and the Aurora cemeteries, thermal vents are 

represented by small, bowl-shaped depressions of layered 

chalcedonic quartz and oncoids, or quartz spheres that were 

turbulently agglomerated (Lynne, 2012; fig. 17). Abundant 

alunite occurs in chalcedonic quartz stockwork veins and in 

matrices of brecciated rhyolite ~135 m below the oncoidal 

thermal vents.

Float blocks of layered quartz veins that strongly 

resemble Aurora district veins are sporadically distributed 

in and east of the Aurora cemeteries. Narrow quartz veins 

(millimeters to centimeters thick) are exposed in a small open 

cut in rhyolite of Aurora near the eastern margin of figure 17 

(sample AUR11-19). Montmorillonite in light-colored tuff 

exposed along haul roads to the Esmeralda mill northeast of 

the cut (fig. 17, sample AUR11-18) may also be related to vein 

mineralization in the Aurora Mining District.
Sawtooth Ridge Alteration Zone 37

Figure 17. A, Geologic map of the Sawtooth Ridge alteration 

zone, Mineral County, Nevada. B, Image of a remnant bowlshaped thermal vent consisting of layered chalcedonic quartz 

and turbulently agglomerated, spherical quartz oncoids.

65-75

Aurora 

townsite

quartz vein float

Aurora

Cemetaries

Aurora district veins

Aurora district veins

Mt.

Chalcedony

EXPLANATION

65-75

0 0.5

0 0.5

1 MILE

1 KILOMETER

oncoidal thermal vent

Photograph location

Colluvium

Trachyandesite of Del Monte

Rhyolite of Del Monte Canyon

Rhyolite of Aurora Creek

Tuff

Silica-alunite-kaolinite alteration

Trachyandesite of Aurora

Contact—Dashed where approximated

Bedding

40Ar/39Ar sample site—Number, age, mineral

Sa w t o oth Ridge

Tra

Tra

Tra

Tra

Tra

Taa

Qc

Qc

Tra

Tra

Tdm

Tdm

Tdm

Trdc

Trdc

Taa

Qc

N

SAW11-9

11.105 ± 0.018 Ma

alunite

10-BA-21

11.181 ± 0.022 Ma

sanidine

119°15' 119° 118°45'

38°25'

38°15'

38°05'

CALIFORNIA

NEVADA

Mono Lake

Mono Valley

Bridgeport

Fletcher Valley

East

Walker

River

Masonic

Bodie

Aurora

Area of map

Base modified from U.S. Geological Survey

Aurora, Nev.-Calif., 1989, 1:24,000
38 Gold-Silver Mining Districts, Alteration Zones, and Paleolandforms in the Miocene Bodie Hills Volcanic Field

Most samples of altered rhyolite in the SR AZ do not 

contain elevated concentrations of minor elements; however, 

several samples of rhyolite and iron oxide-matrix breccia 

contain variably elevated concentrations of Ag, As, Hg, Mo, 

Rb, Sb, Sr, and Te (table 1-4).

Sulfur Isotope Composition

Alunite in veined and brecciated rhyolite below oncoidal 

thermal vents that was collected for 40Ar/39Ar dating has a δ34S 

value of −3.2 ‰ (table 2), and is not associated with sulfide 

minerals. This isotope composition and the absence of sulfide 

minerals indicate that SR AZ alunite formed by near-surface 

oxidation of H2S (steam-heated environment of Rye, 2005).

ASTER Imagery

ASTER imagery (Rockwell, 2010) shows that the SR AZ 

is coincident with a central area of relatively dense pixels that 

correspond to alunite ± kaolinite and lesser quartz, surrounded 

by a more diffusely altered area of illite-altered rocks.

SWIR Spectra

SWIR spectra of hand samples of rhyolite of Aurora 

Creek from the SR AZ correspond to opal, alunite, kaolinite, 

dickite, and montmorillonite.

Hydrothermal Mineral Age

Alunite (± chalcedonic quartz) matrix that cements 

angular clasts of brecciated rhyolite of Aurora Creek (fig. 17, 

sample SAW11-9) has a 40Ar/39Ar date of 11.105 ± 0.018 Ma 

(table 1).

Aurora Canyon Alteration Zone

Location

Secs. 17, 18, 19, 20, 21, 30, 31, T. 5 N., R. 26 E. (unsurveyed); 

sec. 24, T. 5 N., R. 25 E. (unsurveyed), Mono County, California (fig. 1)

Definition

The Aurora Canyon alteration zone (AC AZ; fig. 18) 

is a contiguous volume of predominantly trachyandesite of 

Masonic that has been extensively altered to quartz ± alunite, 

pyrite (iron oxides), mica, and clay minerals. The AC AZ 

occurs in and south of Aurora Canyon, has west-east and 

north-south dimensions of 4.5 and 2.3 km, respectively, and 

covers ~8.1 km2. The AC AZ is overlain by younger volcanic 

rocks to the south (trachydacite of Potato Peak and trachyandesite of Willow Springs), and may be coextensive with the 

Potato Peak alteration zone ~2 km to the southeast. Alteration 

intensity within the AC AZ decreases to the west and east into 

unaltered trachyandesite of Clark Canyon; small internal areas 

of unaltered trachyandesite are mostly represented by float.

History and Production

No production is recorded from the AC AZ, consistent 

with the small scale of surface disturbance, scattered prospect 

pits, trenches, and drill roads. Roads in the eastern part of the 

alteration zone probably provided drill site access, although 

no drill cuttings were identified. Ages of these workings and 

roads are unknown, but the absence of reclamation suggests 

that they predate land use regulations of the Federal Land 

Policy Management Act (FLPMA) of 1976.

Stratigraphy

Trachyandesite of Masonic flows and debris flows 

(~15–14 Ma) were erupted and extensively altered prior to 

emplacement of younger volcanic rocks that intrude and 

enclose the AC AZ (fig. 18). Younger, unaltered rocks include 

trachyandesite of Aurora Canyon (10.6–10.3 Ma; John and 

others, 2012), rhyolite of Bodie Hills (9.9–9.7 Ma) near the 

center of the AC AZ, trachydacite of Potato Peak (9.1–8.8 Ma) 

to the southeast, and trachyandesite of Willow Springs 

(8.6–8.0 Ma) to the southwest. Unaltered trachyandesite of 

Clark Canyon (11.3 Ma; John and others, 2012) is exposed 

west of the alteration zone. Trachyandesite of Willow Springs 

that unconformably overlies altered trachyandesite flows 

comprise domelike landforms that partly filled depressions 

between resistant hills and ridges of altered trachyandesite. 

Three prominent domes of rhyolite of Big Alkali (6.2–5.5 Ma) 

have intruded the alteration zone; the internal structure of 

these domes is depicted by a small concentrically foliated 

“half” dome in NW1⁄4/NW1⁄4 sec. 31, T. 5 N., R. 26 E. (fig. 18). 

The youngest deposits in the AC AZ consist of colluvium that 

accumulated in recessively weathered areas of clay-altered 

trachyandesite, and in active drainages.

The trachyandesite of Clark Canyon forms a series of 

small-volume plugs, arrayed along an east-northeast trend in 

Aurora Canyon, and includes a small-volume lava flow about 

1.5 km south of Aurora Canyon. The trachyandesite of Aurora 

Canyon forms a discontinuous series of small-volume lava 

domes; coarse block and ash flow deposits and (or) carapace 

breccias are preserved along the margins of some domes. The 

trachydacite of Potato Peak forms an elliptical eruptive center 

of moderate volume consisting of coalesced lava flows and 

exogenous flow domes. The trachyandesite of Willow Springs 

forms a north-northwest elongate set of moderate-volume, 

coalesced, lava domes and flows. These four units contain 

6–38 volume percent phenocrysts of plagioclase, clinopyroxene, hornblende, and biotite that are locally trachytically 
Aurora Canyon Alteration Zone 39

Figure 18. A, Geologic map of the Aurora Canyon alteration zone, Mono County, California. B, Image showing a concentrically exfoliated 

rhyolite dome (unit Tbar, rhyolite of Big Alkali) near the southern map boundary.

0 0.5 MILE

0 0.5 KILOMETER

A

Base modified from U.S. Geological Survey

Bridgport, Calif., and Dome Hill, Calif.-Nev., 1989, 1:24,000 

Fig. 18

Tbar

Qc

Twa

Tpp

Trbh

Tac

Thai

Tma

EXPLANATION

Colluvium

Rhyolite of Big Alkali

Trachydacite of Willow Springs

Trachydacite of Potato Peak

Rhyolite of Bodie Hills

Trachydacite of Aurora Canyon

Hornblende andesite intrusion

Trachyandesite of Masonic—

Line-patterned where hydrothermally 

altered; dense red color shows 

quartz-alunite ledge 

Contact

Fault—Dashed where 

approximated, dotted where 

concealed

Foliation

Vertical foliation

Sample locality

40Ar/39Ar sample site—Number, 

age, mineral

Breccia

-21

-20

-22

-23

15 -14

20

-14A

75

20

-13

-10A

PP09-1

-4

clay-alt por 

 rock

-7

-9

-5

-2

-3

-10

-6

-8

65-75

35

15-40

-11

75-v

PP09-10A1

10.87 ± 0.065 Ma

alunite

088-24B

8.58 ± 0.22 Ma

plagioclase

088-24A

6.20 ± 0.026 Ma

plagioclase

location of 

photo inset B

09-BA-42

5.46 ± 0.026 Ma

biotite

088-21A

10.36 ± 0.025 Ma

plagioclase

09-BA-43

11.27 ± 0.11 Ma

plagioclase

098-13A

6.17 ± 0.028 Ma

plagioclase

0.98-13B

9.81 ± 0.027 Ma

sanidine

Thai

Tcc

Tac

Trbh

Tma

? ?

Tma

Tma

Tma

Thai

Thai

Tbar

Tma

Tma

Tma

Tma

Tac

Tac

Tac

Tbar

Tpp

Tpp

Tbar

Tbar

Twa

Twa

Twa

Qc

Qc

Qc

Qc ▲

▼ ►

◄ ▼

▲

▼ ►

◄ ▼

B

119°15' 119° 118°45'

38°25'

38°15'

38°05'

CALIFORNIA

NEVADA

Mono Lake

Mono Valley

Bridgeport

Fletcher Valley

East

Walker

River

Masonic

Bodie

Aurora

Area of map

N
40 Gold-Silver Mining Districts, Alteration Zones, and Paleolandforms in the Miocene Bodie Hills Volcanic Field

aligned. Trachyandesite of Willow Springs contains rare 

olivine phenocrysts, and plagioclase phenocrysts in this unit 

are characteristically larger than those in most rocks of the 

Bodie Hills volcanic field.

Rhyolite of Bodie Hills forms a series of small-volume 

lava domes, many with carapace and (or) basal flow breccias. 

It contains 1–23 percent phenocrysts of plagioclase, quartz, 

sanidine, biotite, hornblende, and rarely clinopyroxene in 

locally glassy and flow-banded matrix. The rhyolite of Big 

Alkali forms a prominent north-trending array of low-volume 

domes. It contains 6 – 42 volume percent phenocrysts of 

plagioclase, hornblende, and biotite, and trace amounts of 

quartz and sanidine. Small exposures of hornblende andesite 

along the Aurora Canyon road in the eastern part of the AC AZ 

contain prominent hornblende phenocrysts.

Structure

No faults have been identified in the AC AZ, and the 

distribution of alteration mineral associations and lithology 

does not require significant fault displacement. However, a 

west-east (±10°) structural trend is implied by the distribution of altered trachyandesite, by alignment of resistant 

exposures of quartz-altered trachyandesite, and by west-east 

and east-northeast-trending linear ridges of silicified breccia 

(fig. 18). On a larger scale, rhyolite of Big Alkali domes in 

the AC AZ are roughly collinear with a north-south alignment of other rhyolite of Big Alkali domes to the south and 

north (John and others, 2012). Although the rhyolite domes 

are ~4–5 m.y. younger than the AC AZ, their alignment may 

reflect an older structure that controlled alteration within 

the zone. The AC AZ is the same age as the Potato Peak 

alteration zone, but is ~1,000 ft (~300 m) lower in elevation, 

and the two alteration zones may be displaced by an unrecognized fault. Alternatively, the Potato Peak alteration zone 

has been elevated relative to the Aurora Canyon alteration 

zone by magmatic inflation during construction of the Potato 

Peak stratovolcano.

 Hydrothermal Alteration

Within the AC AZ, nearly all trachyandesite of Masonic 

has been altered to assemblages dominated by quartz ± alunite, 

clays, and mica. Quartz-altered trachyandesite consists of gray 

to light-brown, very fine-grained to microcrystalline quartz in 

which some relict feldspar phenocrysts are discernible. Most 

quartz-altered trachyandesite has been brecciated and locally 

veined. Breccia matrices and veins, mostly <5 mm in width, 

consist of very fine-grained to microcrystalline quartz, and 

quartz+alunite ± pyrite (iron oxides). Quartz-alunite-pyritealtered trachyandesite and silicified breccia are erosionally 

resistant, capping hills and forming linear ridges as much 

as 5 meters high and meters to tens of meters long. These 

resistant ledges are flanked by recessively weathered zones 

of trachyandesite (tens of meters wide) altered to alunite, 

clay-mica minerals, pyrite (mostly weathered to iron oxides), 

and lesser chlorite. Kaolinite, where present, is proximal to 

quartz-alunite-pyrite-altered trachyandesite, whereas clay 

minerals distal to quartz-altered trachyandesite are dominated 

by illite and montmorillonite. An altered porphyritic rock that 

rests on altered trachyandesite in a small basin (SW4/SW4 

S30, T5N, R26E) is characterized by polygonally desiccated 

soil, indicative of expandable clays, recessive weathering, 

sparse ground flora and little outcrop.

Minor Elements in Rocks

Eight samples of quartz-alunite-pyrite(iron oxides)- and 

clay-pyrite(iron oxides)-altered trachyandesite of Masonic, 

and silicified breccia, contain very low concentrations of 

Au (most <5 parts per billion [ppb]) and Ag (<1 ppm; 

table 1-5). Several samples contain elevated concentrations 

of Hg (~2–21 ppm), As (81–480 ppm), Bi (~1–5 ppm), Te 

(~2–4 ppm), and Sb (tens of ppm). As much as several percent 

sulfur, and Ba concentrations >1,000 ppm, reflect the presence 

of alunite, pyrite, and probably barite, although no barite was 

observed.

ASTER Imagery

ASTER imagery of the AC AZ (Rockwell, 2010) 

shows alunite ± pyrophyllite and lesser alunite+kaolinite, and 

kaolinite-dominant pixels coincident with altered trachyandesite of Masonic. Kaolinite, alunite+kaolinite, and kaolinite/

montmorillonite pixels are coincident with altered porphyritic 

rock in SW1⁄4SW1⁄4 sec. 30, T. 5 N., R. 26 E. Although these 

rocks are pervasively altered, pixels that represent alteration 

mineral assemblages are discontinuously distributed in small 

clusters because of tree (pinion pine) cover, unaltered float of 

younger volcanic rocks, and imagery resolution. 

SWIR Spectra

Hand samples of quartz-alunite-clay-altered trachyandesite and silicified breccia have SWIR wavelength 

absorption bands characteristic of alunite, dickite, jarosite, 

and possibly montmorillonite, which support ASTER imagery 

interpretations and field observations. A sample of the altered 

porphyritic rock contains montmorillonite.

Hydrothermal Mineral Age

Alunite in the matrix of silicified breccia near the 

exfoliated half dome (fig. 18) has a 40Ar/39Ar date of 

10.87 ± 0.065 Ma (table 1). This alunite date is analytically 

indistinguishable from the date of alunite at the Alta Plana 

Mine in the Potato Peak alteration zone (10.83 ± 0.06 Ma, 

table 1) ~1 km to the southeast.
Potato Peak Alteration Zone 41

Potato Peak Alteration Zone

Location

Secs. 33, 34, T. 5 N., R. 26 E.; secs. 3, 4, T. 4 N., R. 26 E. 

(unsurveyed), Mono County, California (fig. 1)

Definition

The Potato Peak alteration zone (PP AZ; fig. 19) on 

the northwest slope of Potato Peak consists of a contiguous 

volume of volcaniclastic rocks, thought to be trachyandesite 

of Masonic (John and others, 2012), that is extensively altered 

to quartz, and assemblages comprised of quartz, alunite, 

mica-clay minerals, and pyrite (iron oxides). The roughly 

circular area of altered strata covers ~1.3 km2 and is entirely 

enclosed by younger volcanic rocks (trachydacite of Potato 

Peak; rhyolite of Bodie Hills), and by colluvium. Some altered 

strata beneath slope wash have been exposed by landslides. 

The PP AZ extends under cover to the north, east, and 

northwest where it may be contiguous with the Aurora Canyon 

alteration zone.

History and Production

Mercury from the Alta Plana Mine, an open cut in the 

central part of the alteration zone, was recovered ~1942 

(Holmes, 1965) in a retorting mill (dismantled) at the mouth 

of Aurora Canyon. Mill feed included cinnabar in brecciated 

and silicified volcaniclastic rocks. The dimensions of mine 

workings and volume of mill calcines suggest that production 

was probably no more than tens of flasks of Hg. Trenches and 

small excavations tens to hundreds of meters northeast of the 

Alta Plana Mine in clay-altered and silicified volcaniclastic 

rocks contain no obvious metallic minerals other than pyrite.

Stratigraphy

Volcaniclastic rocks in the alteration zone consist of debris 

flows derived from volcanic uplands associated with trachyandesite of Masonic that predate the trachydacite of Potato Peak 

and the present Potato Peak landform (fig. 19). Because of 

pervasive alteration, the volcaniclastic rocks are mottled gray, 

beige, and white, and are only exposed in mine workings and 

landslide scarps. These strata consist of as much as 70 volume 

percent angular, subangular, and subrounded clasts of aphanitic 

and faintly porphyritic volcanic rocks (millimeters to centimeters in size) that have been replaced by forms of hydrothermal 

silica, clay minerals, pyrite (iron oxides), and lesser alunite. 

Matrices are composed of variable proportions of the same 

hydrothermal minerals. No unaltered exposures were observed, 

and bedding and foliation are not evident.

Altered and partly leached rocks, exposed in landslide 

scarps and toes ~0.5 km southeast and south of the Alta Plana 

Mine, include several textural varieties of porphyritic rocks. 

These pre-alteration porphyritic rocks are either interstratified 

flows or intrusions within volcaniclastic strata, all of which 

may be trachyandesite of Masonic. 

Structure

Exposure of the PP AZ through younger rocks is a 

consequence of erosional resistance of silicified landforms 

(below), and slope failure caused by unstable mica-clayaltered substrates. A fault northeast of the Alta Plana Mine is 

marked by a linear ridge of silicified breccia, but displacement 

could not be determined and is probably small. The PP AZ is 

coeval with the Aurora Canyon alteration zone but is 1,000 

or more feet higher in elevation; the two alteration zones may 

have been displaced by an unrecognized fault on the west side 

of the PP AZ or by magmatic inflation during assembly of the 

large Potato Peak flow-dome complex (fig. 19).

Hydrothermal Alteration

The Alta Plana Hg Mine is in a resistant knob, a few tens 

of meters in dimension, composed of light-gray to beige, finegrained to microcrystalline, slightly vuggy quartz that replaced 

volcaniclastic strata. Near-vertical joint sets, one of which 

strikes ~N70°W, give parts of the knob a columnar aspect. 

Silicified volcaniclastic deposits on the west and northwest 

sides of the knob exposed by mining have been brecciated and 

cemented by at least three matrices that consist of (1) dense, 

gray, fine-grained to microcrystalline quartz and lesser opaline 

silica; (2) soft, white to beige kaolinite and alunite; and 

(3) fine-grained quartz, cinnabar, barite, jarosite, and voids. 

Cinnabar also occurs in millimeter-thick veins and on irregular 

fractures in densely silicified volcaniclastic strata.

A north-south-oriented, resistant ridge composed of 

silicified, multigenerational, pyritic breccia ~0.5 km northeast 

of the Alta Plana Mine has been explored by shallow cuts and 

trenches. Mottled gray-brown volcaniclastic rocks exposed in 

workings near this ridge consist of subangular to angular clasts 

(millimeters to centimeters in size) of fine-grained to microcrystalline quartz and variable amounts of white clay minerals. 

The altered clasts are enclosed by white to gray matrices of 

fine-grained to microcrystalline clay minerals and quartz, and 

up to 20 volume percent voids lined with submillimeter quartz 

crystals. Some gray, fine-grained quartz clasts are pocked with 

small voids where phenocrysts have been leached.

Minor Elements in Rocks

Samples of breccia with quartz-cinnabar matrix from the 

Alta Plana Mine (table 1-6) contain 1.9–17 weight percent Hg, 

and 64–900 ppb Au. These samples and four others from the 

alteration zone contain elevated concentrations of Hg (several 

parts per million to percents), As (tens to hundreds of parts per 

million), Bi (~1–19 ppm), Te (~1–3 ppm), Sb (as much as tens 

of parts per million), and sulfur (as much as several percent), 

presumably residing in cinnabar, pyrite, and lesser barite and 

alunite.
42 Gold-Silver Mining Districts, Alteration Zones, and Paleolandforms in the Miocene Bodie Hills Volcanic Field

Figure 19. A, Geologic map of the Potato Peak alteration 

zone, Mono County, California. B, Image showing landslides 

developed on altered volcaniclastic strata.

Tpp

Trbh

Trbh

Tpp

Tpp

Qc

 dozer 

Alta Plana trenches

Hg Mine

-4

-7

-6

POTPK08-1

-3

POTPK09-2

heterolithic bx; 10’ 

POTPK09-20

POTPK09-20A

POTPK09-21

POTPK09-22

POTPK09-23

POTPK09-24

POTPK09-26 POTPK09-29

POTPK09-28

POTPK09-25

POTPK09-27

altered 

volcaniclastic 

strata

landslides

landslides

Potato 

Peak

088-24C

8.996 ± 0.025 Ma

plagioclase 

hornblende

08-BA-46

10.83 ± 0.06 Ma

alunite 

hornblende

08-BA-50

9.757 ± 0.013 Ma

sanidine 

hornblende

088-21D

8.81 ± 0.07 Ma

plagioclase 

hornblende

088-21E

8.86 ± 0.05 Ma

plagioclase 

hornblende

088-24D

9.09 ± 0.04 Ma

plagioclase hornblende

(actual sample site is ~450 m 

south of symbol)

80-v 60-80

15-35

20

20

B

A

Base modified from U.S. Geological Survey

Bodie, Calif., 1998 and Dome Hill, Calif.-Nev., 1989, 1:24,000

0 0.5

0 0.5

1 MILE

1 KILOMETER

N

EXPLANATION

Fig. 19

Tpp

Trbh

Qc Colluvium

Trachydacite of Potato Peak

Rhyolite of Bodie Hills

Volcaniclastic deposits—Altered to 

quartz, pyrite, mica, clay 

minerals, and alunite

Contact

Fault—Dashed where approximated

High-angle normal fault—Bar and 

ball on downthrown block

Foliation

40Ar/39Ar sample site—Number, age, 

mineral

Sample site and number

Open-pit mine

Mine dump

119°15' 119° 118°45'

38°25'

38°15'

38°05'

CALIFORNIA

NEVADA

Mono Lake

Mono Valley

Bridgeport

Fletcher Valley

East

Walker

River

Masonic

Bodie

Aurora

Area of map
Aurora Mining District 43

Sulfur Isotope Compositions

The S isotope compositions (δ34S) of matrix cinnabar in a 

sample of brecciated and silicified volcaniclastic rocks in the 

Alta Plana Mine are −10.3 and −9.8 ‰ (table 2). Alunite and 

barite in matrices of breccia samples from the mine have δ34S 

values of 16.3 and 11.6 ‰, respectively. The low δ34S sulfide 

and high δ34S sulfate values are consistent with disproportionation of magmatic SO2

 (Rye, 2005) during formation of the 

alteration zone. Sulfur isotope equilibrium temperatures were 

not calculated because cinnabar, alunite, and barite do not 

coexist in the samples examined.

ASTER Imagery

ASTER imagery (Rockwell, 2010) of the PP AZ 

shows small clusters of pixels that correspond to quartz and 

alunite ± kaolinite centered on the Alta Plana Mine and on the 

ridge of silicified breccia to the northeast.

SWIR Spectra

Based on SWIR analyses of hand samples, breccia 

from the Alta Plana Mine consists of quartz, probable opal, 

jarosite, kaolinite, alunite, and topaz. Mica-clay minerals in 

altered volcaniclastic rocks in mine workings near the ridge of 

silicified breccia northeast of the Alta Plana Mine are dickite 

and probable halloysite, based on SWIR and XRD analyses. 

Alteration minerals in porphyritic rocks exposed in landslide 

scarps southeast and south of the Alta Plana Mine include illite 

and dickite.

Hydrothermal Mineral Age

Alunite in the matrix of silicified breccia from the 

Alta Plana Hg Mine has a 40Ar/39Ar date of 10.83 ± 0.06 Ma 

(table 1), which is analytically indistinguishable from 

the date of alunite in the Aurora Canyon alteration zone 

(10.87 ± 0.07 Ma) ~2 km to the northwest.

Aurora Mining District

Location

Secs. 9, 10, 17, 18, 19, 20, 30, T. 5 N., R. 28 E., Mineral 

County, Nevada (fig. 1)

History and Production

Gold-silver veins were discovered in 1860 in an area 

of the Bodie Hills initially called the Esmeralda Mining 

District and thought to be in Mono County, California. The 

Esmeralda Mining District was soon thereafter renamed 

the Aurora Mining District, and in 1864 was found by a 

state boundary survey to be in Nevada Territory (originally 

Esmeralda County, now Mineral County, Nevada). The towns 

of Esmeralda and Aurora were established in the early 1860s. 

Most underground mining occurred between 1860 and 1864 

(Stretch, 1867; Wasson, 1878; Clarke, 1882; Hill, 1915), when 

the population of the district exceeded 6,000. After 1864, 

production declined precipitously, and by 1865 mining stocks 

were worth less than “Confederate script” (Wasson, 1878). By 

1880, production had decreased to 907 oz Au and 4,834 oz Ag 

recovered from 250 t of ore (King and others, 1885). During 

the early 20th Century (~1906–18), estimated production of 

0.6 Mt @ 0.15 opt Au equivalent (Lawrence, 1987; Couch and 

Carpenter, 1943; Stone, 1982) was derived from cyanidation 

of tailings and from small amounts of ore recovered from 

dumps and old workings (Vanderburg, 1937). In the late 

1940s, ~10,000 t of ore containing >1 opt Au (Stone, 1982; 

Tingley, 1990) were produced from underground mining of 

the Juniata vein system (fig. 20). Production since the 1980s 

has been derived from opencut and underground mining of the 

Humboldt-Hilton, Prospectus, Juniata, and Ann vein systems 

on Martinez and Humboldt Hills, and in the New Esmeralda 

area, ~4.2 km northeast of the Prospectus vein (Gilbert, 1976; 

Osborne, 1985; Shaddrick, 1989; Tingley, 1990; Knudsen and 

Prenn, 2002). From ~1988 to 1998 these vein systems yielded 

an estimated 0.3–0.4 Moz Au and 0.5–0.8 Moz Ag from 3  

to 4 Mt of ore that graded ~0.1 opt Au (Knudsen and Prenn, 

2002; Nevada Bureau of Mines and Geology, 2009). Production during this period was derived from separate mining 

operations and may have been counted twice or more in total 

district production. Measured and indicated resources include 

a bulk-mineable resource of ~31 Mt @ 0.031 opt Au, and 

an underground resource of 0.19 Mt @ 0.5 opt Au (Nevada 

Bureau of Mines and Geology, 2009). Perlite deposits on 

Aurora and Bodie Creeks, and on a tributary of Bodie Creek, 

north and northwest of the district have been episodically 

mined at small scales (Archbold, 1966).

Total district production reported by Long and others (1998) for the period 1860–1995 is 1.817 Moz Au, 

20.605 Moz Ag, and 3.86 Mt of ore. Total production 

through 1998 was estimated by Knudsen and Prenn (2002) 

at 1.91 Moz Au. These production totals are largely based on 

dollar values of bullion and estimated Au/Ag from the most 

productive period (1860–64), when an estimated 1.5 Moz Au 

was recovered (Wasson, 1878; Angel, 1881; Ferguson, 1929; 

Vanderburg, 1937; Couch and Carpenter, 1943).

Accurate weight records do not exist for most early production. Production through 1869, estimated at $2.4–29.5M 

(Wasson, 1878; Ross, 1961), was in part reconstructed from 

recollections of shipping agents and newspaper accounts, as 

most shipping and assay records were lost or destroyed. Early 

Aurora production may include initial production from the 

Bodie Mining District that was milled at Aurora (Blake, 1869; 

Angel, 1881; Wasson, 1878; Vanderburg, 1937). Furthermore, 

Au/Ag used to convert value to weight varied considerably 
44 Gold-Silver Mining Districts, Alteration Zones, and Paleolandforms in the Miocene Bodie Hills Volcanic Field

60-70o

40-60o

30-35o

40-75o

45o

30-80o

50o

50o

25-80o 40-80o

50o

45o 70o-v

75o-v

60°

55-70o

55-70o

75-85o

45-50o

Creek

Humboldt vein

Humboldt 

Hill

Bald Eagle

SILVER 

HILL

Prospectus vein

Juniata

 veins

Esmeralda

Radical

Spotted Tiger

Last

Chance 

Hill

Wide West

Middle 

Hill

Martinez

Hill

Prospectus fault

Aurora 

Townsite

Del Monte 

shaft

Gregory 

Aurora Flats

Hill

Antelope

Dream adit

Middle adit

North

 Utah Opposition

CortezUtah

Gladiator Monarch

Seminole

Black Hawk

Hornet?

Eureka

Hypo

Summit

Sawtooth Ridge 

Alteration Zone

Aurora

Sandlot

Philadelphia

quartz vein float

Aurora

Cemeteries

Durant

Live Yankee

Juniata Fault

LadyJane

Hornet

adit

Brewery

Spring

Tra

Tra

Tra

Tra

Tra

Tra

Taa

Taa Taa

Taa

Taa

Taa

Qc

Qc

Qc

Qac Qac

Qc

Taa

Taa

Taa

Kgr

Tmr

Twba

Tsm

AU-2/59/DD61

10.28 ± 0.05 Ma

adularia

FA1

10.04 ± 0.03 Ma

adularia

AU-1/58/DD61

10.4 ± 0.1 Ma

adularia 

00-BA-16 

13.13 ± 0.44 Ma

hornblende

00-BA-21

11.181 ± 0.022 Ma

sanidine

(actual sample site is ~300 m 

north of symbol)

N

Base modified from U.S. Geological Survey

Aurora, Nev.-Calif., 1989, 1:24,000

0 0.5 MILE

0 0.5 KILOMETER

Fig. 20
Aurora Mining District 45

Figure 20. (Facing page) Geologic map of the Aurora Mining District, Mineral County, Nevada. Geology and vein locations and 

names modified from Hill (1915), Lawrence (1987), Osborne (1985), Shaddrick (1989), Knudsen and Prenn (2002), and John and 

others (2012).

40

40

EXPLANATION

Mine dumps and disturbed ground

Colluvium and volcaniclastic deposits (Quaternary–Pliocene)

Trachyandesite of Aurora Crater (Pleistocene)

Rhyolite of Martinez Hill (Pliocene)

Sedimentary rocks of Martinez Hill (Pliocene and Miocene)

Rhyolite of Aurora Creek (Miocene)

Trachyandesite of West Brawley Peak (Miocene)

Trachyandesite of Aurora (Miocene)

Granitic rocks

Cretaceous granite

Contact—Dashed where approximated

Fault—Dashed where approximated, dotted where concealed

Bedding

Foliation

Mine shaft

Adit

Quartz vein zones—Numbers indicate dip

Color air photo (CAP) lineament

Open-pit mine

40Ar/39Ar sample site—Number, age, mineral

Tra

Tsm

Tmr

Twba

Qc

Kgr

Taa

Qaca

119°15' 119° 118°45'

38°25'

38°15'

38°05'

CALIFORNIA

NEVADA

Mono Lake

Mono Valley

Bridgeport

Fletcher Valley

East

Walker

River

Masonic

Bodie

Aurora

Area of map
46 Gold-Silver Mining Districts, Alteration Zones, and Paleolandforms in the Miocene Bodie Hills Volcanic Field

by reference (Hill, 1915; Ferguson, 1929) and mine (Osborne, 

1985). From “detailed records” Knudsen and Prenn (2002) 

estimated a grade of >2 opt Au for the first 1.5 Moz, implying 

≤3 Mt of ore. This tonnage would have been derived from 

underground vein mining mostly during the 1860s. Based on 

dimensions of veins, stopes, dumps, and tailings, estimated ore 

tonnage and recovered Au seem unrealistically high, unless a 

large volume of early tailings was eroded and (or) Au grades 

were tens to hundreds of ounces per ton. Wasson (1878) 

stated that during the first few years “many thousands of tons 

were milled that produced several thousand dollars per ton.” 

However, specimens of such multiounce ore apparently were 

not archived.

Stratigraphy

Mesozoic granitic and metavolcanic rocks and Tertiary 

trachyandesite and rhyolite are exposed in the eastern and 

southeastern parts of the district (Hill, 1915; John and others, 

2012; fig. 20). Trachyandesite of Aurora (~13.1–12.6 Ma; 

table 1), which encloses nearly all veins, unconformably 

overlies Mesozoic quartz monzodiorite of Aurora and 

metavolcanic rocks. It is exposed in a roughly elliptical area, 

~10 km north-south by ~5 km west-east, which is largely 

defined by younger volcanic rocks. Trachyandesite of Aurora 

may be as much as 400 m thick if exposures between the top 

of East Brawley Peak and granite on the east slope of Middle 

Hill are unfaulted. Trachyandesite flows and volcaniclastic 

strata on Middle, Silver, and Martinez Hills have been 

intruded by porphyritic rocks, including rhyolite and latite 

dikes and plugs (Lawrence, 1987; Osborne, 1985; Knudsen 

and Prenn, 2002; John and others, 2012). Altered trachyandesite of Aurora on and south of East Brawley Peak, adjacent to 

the southwest edge of the district, comprises the East Brawley 

Peak alteration zone.

Rhyolite of Aurora Creek (11.2 Ma; table 1), rhyolite 

of Del Monte Canyon (~11.2 Ma; John and others, 2012), 

trachyandesite of Del Monte (11 Ma), and trachyandesite of 

West Brawley Peak (~11. 5–11.3 Ma; John and others, 2012) 

unconformably overlie trachyandesite of Aurora to the north, 

northwest, and west. Rhyolite of Aurora Creek forms a group 

of small-volume lava domes and includes minor cogenetic 

pyroclastic flow deposits, especially in the lower reaches of 

Bodie Creek. It contains 1–9 volume percent phenocrysts of 

plagioclase and rare quartz, sanidine, hornblende, clinopyroxene, and biotite in a glassy groundmass. Altered flowdomes of rhyolite of Aurora Creek north of Aurora Creek 

and northwest of the Aurora town site comprise the Sawtooth 

Ridge alteration zone (fig. 20). Veins in rhyolite of Aurora 

Creek in and northeast of the Aurora cemeteries, represented 

largely by float, closely resemble veins in trachyandesite of 

Aurora.

Rhyolite of Del Monte Canyon forms a set of lowvolume lava domes and associated pyroclastic deposits that 

are well-bedded, lithic rich, and underlie the lava flows. It 

contains 6–26 volume percent phenocrysts of plagioclase, 

quartz, hornblende, biotite, and sanidine in glassy (perlitic in 

places) to moderately devitrified groundmass. The trachyandesite of Del Monte, which includes basaltic trachyandesite 

and trachydacite, forms a discontinuous, north-trending 

series of exposures that consist of lava flows and associated, 

heterogeneous, laharic debris flow and volcaniclastic deposits. 

It contains 0–50 volume percent phenocrysts of plagioclase, 

biotite, clinopyroxene, and hornblende in a weakly devitrified 

groundmass. The trachyandesite of West Brawley Peak forms 

a series of lava flows erupted from the moderate-volume 

composite volcano centered on West Brawley Peak. It contains 

~10–35 volume percent phenocrysts of plagioclase, hornblende, biotite, clinopyroxene, and trace amounts of olivine in 

a moderately devitrified groundmass. Plagioclase phenocrysts 

in trachyandesite of West Brawley Peak are characteristically 

larger (commonly >1 cm) than those in most rocks of the 

Bodie Hills volcanic field.

Pliocene-Pleistocene rocks of the Aurora volcanic field 

(John and others, 2012) overlie the trachyandesite of Aurora 

and other premineralization rocks north, east, and south of 

the district. These rocks include the rhyolite of Martinez Hill, 

sedimentary rocks of Martinez Hill, trachydacite of Aurora 

Peak, trachyandesite of Aurora Crater, and various other trachyandesite and trachydacite lava flows of the Aurora volcanic 

field. These eruptive rocks vary in age from 3.4  to  0.1 Ma 

(Gilbert and others, 1968; Silberman and McKee, 1972; Lange 

and others, 1993; Lange and Carmichael, 1996). Based on 

drill hole intercepts near Fletcher Junction, ~ 4 km north of the 

Aurora Mining District, trachyandesite of Aurora Crater covers ~150 m of unaltered colluvial deposits that overlie at least 

455 m of altered mafic tuffs and lacustrine deposits (Nevada 

Exploration Inc., 2013). These strata comprise basin-fill of 

Fletcher Valley (Tfv of John and others, 2015), and alteration 

of the mafic tuffs and lacustrine deposits is interpreted to have 

coincided with formation of Aurora veins.

Structure

Predominant faults in the district contain quartz veins 

that number in the hundreds if all the short and unaligned vein 

segments are counted (Brady’s map of Aurora and Esmeralda, 

1862; fig. 20). Fault sets (and veins in them) presumably 

reflect stress accommodation within the Walker Lane transtensional structural zone of strike-slip displacement and extension. Vein attitudes and kinematic indicators in the Aurora 

Mining District are consistent with maximum horizontal 

extension oriented N60°W and maximum horizontal compression oriented N30°E, similar to those of mineralized structures 

in the Masonic Mining District (John and others, 2012).
Aurora Mining District 47

Most veins strike N45–70°E and dip 20–75°SE, reflecting fault orientations in which the veins formed. Episodic 

displacement along northeast-striking faults created dilatancies 

in which vein minerals precipitated, as evidenced by distinct 

opposing layers of vein minerals, by numerous narrow crosscutting veins in wall rocks, and to a lesser extent, by several 

generations of internal wall-rock fragments in wide veins. 

Several short vein segments, the prominent Esmeralda 

vein, and the Prospectus Fault, strike north-south to N10°E, 

and dip at high angles or are vertical. These veins and the 

Prospectus Fault define a second significant structural trend 

in the district. Post-vein, right-lateral movement of at least 

545 m on the Prospectus Fault has been invoked to explain 

offset of veins and rhyolite of Aurora Creek in the eastern 

part of the district from veins and rhyolite in the western part 

(fig. 20; Hill, 1915; Green, 1964; Osborne, 1985, 1991). Other 

pre-(?) and post-vein faults (not shown of fig. 20) include a 

N10–30°W-trending set on Middle Hill, N70°W faults that are 

most prominent on East Brawley Peak (Silberman and others, 

1995; Lawrence, 1987; Breit, 2000), and a west-east set that 

has dismembered and laterally displaced northeast-striking 

veins for as much as 15 m (Knudsen and Prenn, 2002). Postvein faults offset alteration zones and volcaniclastic deposits 

in the vicinity of the Juniata vein system (fig. 20; Osborne, 

1985).

Thin seams of gouge, mostly in hanging walls of veins, 

and fluvial gravels interpreted as sag deposits (Knudsen and 

Prenn, 2002), also attest to post-vein strike-slip movement. 

Clasts of 2.5 Ma Martinez rhyolite in the sag deposits, 

coupled with the absence of clasts of trachyandesite of Aurora 

Crater (~0.25 Ma; Silberman and McKee, 1972), constrain 

sag deposit ages and at least some postmineralization fault 

displacement to <2.5 Ma. A west-east lineament that is 

conspicuous on color aerial photography (CAP lineament, 

fig. 20) separates veins on Last Chance Hill and Humboldt 

from Martinez Hill and veins on Middle Hill and Silver Hill. 

This lineament may mark a fault that displaced some veins and 

volcanic strata down-to-the-north.

Veins apparently extend northeast of the district under 

colluvium and trachyandesite of Aurora Crater to the New 

Esmeralda area where veins similar to those in the Aurora 

Mining District were mined underground in the 1860s and by 

open cut in the 1990s. The presence of veins beneath Aurora 

Crater north of the district has been proposed based on float 

and geochemical anomalies in the tributary of Bodie Creek 

that drains the district to the north. Other evidence of covered 

veins includes altered and geochemically anomalous strata 

intersected in drill holes (Nevada Exploration Inc., 2013). 

Float of chalcedonic and layered quartz veins, and a mined 

vein in rhyolite of Aurora Creek ~0.5 km northeast of Aurora 

cemeteries, may be coeval with veins in trachyandesite of 

Aurora; the rhyolite may contain or cover other veins. Poorly 

exposed veins also have been intersected by drill holes 

southeast of the Juniata Mine (Osborne, 1985), and additional 

veins may be covered by rhyolite of Martinez Hill.

Forms of Gold-Silver Mineralization

Veins and Vein Zones

All precious metal production in the Aurora Mining 

District has been derived from veins mined underground prior 

to ~1950, and mined by open pit in the 1980s, 1990s, and early 

2000s. Between 1860 (when the district was discovered) and 

1862, more than 300 veins were located and named on Silver, 

Middle, Last Chance, Humboldt, and Martinez Hills (Brady’s 

map of Aurora and Esmeralda, 1862). Ore was produced from 

~30 veins. Other veins are exposed in the New Esmeralda area 

~4.2 km northeast of the Prospectus vein. Although partially 

covered by younger strata, the Aurora district vein system 

apparently extends northeast from Silver Hill to at least the 

New Esmeralda area, a distance of ~7.5 km.

Many of the early claim locations covered segments 

and branches of veins that, based on structural and textural 

characteristics, can be grouped into vein zones (fig. 20). Vein 

zones on Silver Hill consist of meters-thick tabular segments 

of layered quartz veins and subparallel, centimeters-thick 

layered quartz veins that occur commonly in the footwall of 

thicker vein segments. Thick vein segments are contiguous 

along strike for tens to hundreds of meters, although thicknesses and dips vary considerably over short strike distances. 

Extremities of vein zones are marked by thin anastomosed 

veins that merge with fractures. With the exception of 

the Esmeralda vein zone, which strikes N10°E and dips 

75°E-vertical, vein zones on Silver Hill predominantly strike 

N40°E and dip 50 ± 20°SE. One of the largest vein zones, the 

Spotted Tiger-Bald Eagle, is ~0.6 km long, dips 30–80°SE, 

and is as much as ~9 m thick (fig. 20).

Thick veins consist of tens to >100 laterally symmetrical 

layers of fine-grained and chalcedonic quartz. Central and 

internal layers commonly enclose small (centimeter dimensions) voids lined with millimeter-sized or smaller quartz crystals; other layers consist of opposed centimeter-sized euhedral 

quartz crystals. Adularia is sparingly present in some quartz 

layers, but most has been replaced by quartz or sericite. Calcite 

is uncommon in layers, although calcite pseudomorphs and 

perimorphs are present in most veins. They form unoriented 

“blades” of fine-grained quartz, and tabular voids enclosed by 

fine-grained quartz crystals, respectively (“lattice-type” bladed 

quartz after calcite; Etoh and others, 2002); both forms occur in 

centimeter-wide layers that are as much as 50 volume percent 

void. Ore in vein zones reportedly occurred as discontinuous 

layers (submillimeters to centimeters thick) and clots (millimeters to centimeters wide) of fine-grained sulfide minerals, 

electrum, and sericite that alternate with quartz layers and 

constituted as much as several volume percent of the vein.

The Prospectus, Humboldt, Juniata, and New Esmeralda 

vein systems, and some veins on Last Chance Hill, were 

inaccessible during the period of this investigation because 

of active milling operations (ore transported from the Midas 

district, Humboldt County, Nevada). The N50–60°E-trending 
48 Gold-Silver Mining Districts, Alteration Zones, and Paleolandforms in the Miocene Bodie Hills Volcanic Field

Prospectus-Humboldt vein system is exposed for ~1,850 m, 

and consists of veins that vary in width from <30 cm to 9.1 m 

and dip 55–70°NW (Osborne, 1985). The Juniata vein system 

consists of three subparallel veins that strike N60–85°E, dip 

75–85°SE, and are as much as 15 m thick. Descriptions and 

images of these vein systems in Osborne (1985) demonstrate 

a similarity to Silver Hill vein zones. The New Esmeralda 

vein system is exposed in an open pit in secs. 9, 10, T. 5 N., 

R. 28 E. The vein system in the pit consists of six layered 

veins that are 1–1.5 m wide, and numerous narrower veins 

between and adjacent to wider veins. Wide veins strike 

~N30°E and dip ~75°NW. Based on attitudes of chalcedonic 

sediments that filled a void internal to quartz layers, original 

vein dips were 50–70° (fig. 21).

Present vein dips may be ~5–25° steeper than vein 

dips during deposition. If present vein declinations have 

been reversed by fault displacement, then the dip change 

approaches vertical. However, no stratigraphic evidence for 

significant tilting exists, and present and original vein attitudes 

apparently differ by no more than a few degrees.

A second type of vein zone consists of numerous closely 

spaced, subparallel quartz veins, quartz-matrix breccias, and 

internal trachyandesite septa that collectively define a tabular 

geometry. These vein zones are tens to hundreds of meters 

long and meters to tens of meters wide; most dip steeply 

southeast (for example, Wide West and other veins on Last 

Chance Hill and Middle Hill; fig. 20). Within these vein zones, 

individual veins are centimeters to tens of centimeters wide 

and consist of fine-grained to chalcedonic quartz in which 

layering is less pronounced or absent. Tabular quartz-matrix 

breccias, also centimeters to tens of centimeters wide, consist 

of centimeter-sized fragments of trachyandesite in matrices of 

fine-grained to chalcedonic quartz, lesser K-feldspar, sericite, 

and calcite, and rare sulfide minerals, mostly pyrite. Calcite is 

typically coarse-grained (millimeter-sized crystals) and usually 

occurs in central parts of veins and matrices, suggesting a 

late paragenetic position. Fluorite, mostly in cubic crystals, 

is locally found in veins near the Del Monte shaft (fig. 20) on 

surfaces of fine-grained drusy quartz, and encrusted by similar 

quartz; it is also paragenetically late. Trachyandesite between 

closely spaced veins, and trachyandesite fragments in breccias, 

are densely silicified or replaced by quartz-sericite-pyrite 

assemblages. Internal trachyandesite septa in wide vein zones 

are altered to propylitic assemblages.

A third type of vein zone is represented solely by the 

N10°E-striking, near-vertical Esmeralda-Radical vein zone 

on Silver Hill (fig. 20), which was the district discovery site 

in 1860. The Esmeralda-Radical vein zone is as much as 

18 m wide (Hill, 1915) and is the widest in the district, and 

among the longest at 0.8 km. It consists of a resistant tabular 

mass that includes several generations of quartz breccia and 

stockwork (arbitrarily distinguished by relative matrix and 

clast proportions) that include trachyandesite clasts, much 

like the Comstock Lode (Vikre, 1989). Breccia matrices and 

stockwork veins are composed of quartz, lesser K-feldspar, 

sericite, and calcite, and uncommon sulfide minerals (mostly 

pyrite). Euhedral quartz crystals in vugs and veins vary in size 

from submillimeters to centimeters. Most calcite is internal 

to quartz in matrices, implying a late paragenetic position. 

Trachyandesite clasts are largely replaced by fine-grained to 

chalcedonic quartz, K-feldspar, and pyrite; some K-feldspar 

has been altered to sericite.

Ore Bodies

Mines in the Aurora Mining District are largely inaccessible, mineralized samples on dumps are sparse, and 

documented archival ore specimens are few and small (most 

are centimeter in size). Descriptions of 19th century mining, 

stopes, and ore occurrences, mostly from early literature and 

unpublished reports (Clarke, 1882; Hill, 1915; Payne, 1965; 

Lawrence, 1987; Shaddrick, 1989; Rhoden, 1992), are uneven 

in detail, and ore bodies can only be described generally. Ore 

produced from 1860 to 1864 apparently contained several 

or more ounces per ton gold. As described by Hill (1915), 

ore occurred in rich “streaks,” as much as 15 cm wide, that 

consisted of quartz, adularia, tetrahedrite, pyrite, chalcopyrite, 

Au (presumably electrum), and a Au-Ag-Se phase. The 

value of Au in early mined ores exceeded that of Ag, where 

reported, by 2–5 times (Burchard, 1884), implying Au/Ag of 

~ 0.13– 0.31 (gold = $20.68/oz; silver = $1.29/oz).

Ore within vein zones on Silver Hill raked downdip 

at high angles. It usually was positioned along or internal 

to hangingwalls or footwalls, and seldom comprised entire 

vein widths. Clarke (1882) described the high-grade ores 

(called “rich chambers”), which were mined out by 1864, as 

occurring in wider parts of otherwise barren veins. Five such 

chambers were mined from a 1,500 ft-long section of the 

Utah-Cortez vein on Silver Hill. One chamber that extended 

from the surface to −150 ft, was 50–75 ft long, 20–25 ft wide, 

and contained 20,000 t @ ~5 opt Au. Unmineralized parts of 

the vein were 3 ft wide. Ore in Antelope vein on Silver Hill 

averaged ~7–15 opt Au equivalent (Lawrence, 1987). On 

Last Chance Hill, five high-grade ore shoots in the Wide West 

vein were 60–120 ft below the surface, 16–60 ft wide, and 

100–200 ft long (Lawrence, 1987). Some veins were mined to 

depths of 500 ft, but most stoping terminated tens to several 

hundreds of feet below the surface. At 800 ft in the Del Monte 

and Juniata shafts, heavy water flows prevented deeper 

excavation (Burchard, 1884). Veins have been intercepted 

in drill holes at depths exceeding 300 m, although on Silver 

Hill, veins transitioned downward from contiguous veins 

(meters wide) at the surface to narrower, low-grade to barren, 

zones of stockwork veins and silicification (Lawrence, 1987; 

Rhoden, 1992).
Aurora Mining District 49

Figure 21. Image of a sample from the Aurora Mining District. Layered vein from New Esmeralda Mine dump with a restored 65° dip 

based on bedded chalcedonic sediments that filled an internal void (enlarged inset on left). Relative to ~75° dips of wide veins exposed 

in the high wall, vein declinations may have changed since deposition (~10.5 Ma) by 5° to as much as 80° if declinations are reversed.

edge of

former

void

bedded

chalcedony

4 cm

2 cm

Original vein dip based on bedded 

chalcedony is 50–70°

New Esmeralda mine dump (AUR12-1)

Juniata-Prospectus Vein Minerals

Detailed published descriptions of vein mineral assemblages, textures, and paragenetic relationships are limited 

to veins in the northeastern part of the district (Osborne, 

1985). The Juniata and Prospectus vein systems consist of 

variable proportions of quartz, adularia, pyrite, chlorite, 

electrum, acanthite, naumannite, bromargyrite, and barite 

that comprise three partially cospatial depositional stages: 

early barren, ore stage, and post-ore stage barren. In Juniata 

veins, stage 1 mineralization is mainly situated along vein 

margins. It consists of trachyandesite fragments with as much 

as 30 volume percent pyrite that are cemented by crustiform 

quartz and lesser calcite that is replaced by quartz ± adularia. 

At higher elevations, most stage 1 quartz has colloform 

or botryoidal textures. Stage 2, the ore stage, consists of 

greenish-tinted quartz+adularia that has textural and grain 

size similarities to stage 1. In stage 2, electrum, with variable 

Au/Ag, acanthite, naumannite, and pyrite are closely associated. Stage 3 is characterized by crustiform vuggy quartz and 

replacement of calcite by quartz. Throughout the Juniata vein, 

Au/Ag decreases with depth.
50 Gold-Silver Mining Districts, Alteration Zones, and Paleolandforms in the Miocene Bodie Hills Volcanic Field

Mineral Compositions in Silver Hill and Middle 

Hill Veins

Based on petrographic and semiquantitative SEM and 

XRD analyses, metallic minerals in archival specimens and 

dump samples from the Antelope, Wide West, Martinez, 

Crocket (figs. 22, 23, 24), and Amador Mines include pyrite, 

acanthite (with minor amounts of Se, Cu, and Sb), naumannite, sphalerite (with minor Cd and no detectable Fe or Mn), 

galena, polybasite (~Ag 15 Cu 2.6 Sb 1.5 As 0.7 Se 0.7 S 11 ), tetrahedrite 

(~ (Cu 7 Ag 3 Zn 2 ) 12 Sb 4.2 S 13 ), chalcopyrite, arsenopyrite, and a 

Ag-Au-S mineral (~Ag4AuS3). SEM analyses also suggest the 

presence of submicrometer intergrowths of Ag-Au-Sb-S-Se 

minerals, because atomic proportions of many metallic 

phases do not match those of documented minerals. Two 

compositional groups of electrum, ~Ag0.5 ± 0.1Au0.5 ± 0.1 and 

~Ag0.2 ± 0.1Au0.8 ± 0.1, may be present within a single petrographic 

section; variable electrum compositions may, in part, reflect 

the absence of buffering by an Ag phase. Based on textures of 

mineral assemblages and on the absence of copper and iron 

oxide minerals, most imaged minerals are interpreted to be 

hypogene. Some Ag-As-Au-S phases that enclose other sulfide 

minerals may be all or part supergene.

In addition to the imaged minerals, pearcite, proustite, 

covellite, and barite have been reported (Vanderburg, 1937; 

Osborne, 1985; Knudsen and Prenn, 2002). Breit (2000) 

reported Te concentrations of as much as 20 ppm in vein 

samples analyzed by bulk methods, but no Te minerals were 

identified during this investigation.

Minor Elements in Rocks

Samples of veins and altered wall rock (mostly trachyandesite of Aurora), collected and analyzed in 1967–68 by 

the U.S. Geological Survey (Breit, 2000), contain elevated 

concentrations of Au, Ag, As, Sb, Hg, F, Mo, Te, Cu, Pb, 

Zn, and W, with the highest values in vein samples. The 

distribution of W abundances in altered trachyandesite and 

vein samples was interpreted by Breit (2000) as evidence 

that Silver Hill was the hottest and deepest part of the Aurora 

district vein system. Other geochemical zonation, including 

decreasing Ag/Au and As/Sb, and, to an extent, decreasing Te, 

Mo, W, and Sn concentrations northeast from Silver Hill, was 

attributed by Breit (2000) to a hydraulic (topographic) gradient, to regional zoning of coeval alteration on East Brawley 

Peak and Aurora veins, or to separate hydrothermal cells 

within the Aurora vein system. Minor element concentrations 

in 14 samples of trachyandesite wall rocks of the Juniata and 

Prospectus vein systems include local, elevated concentrations 

of Mo, Ag, As, F, and Hg (Osborne, 1985). Elevated minor 

element concentrations in 13 vein samples from mine dumps 

throughout the district (table 1-7) include Au (0.51–84.8 ppm), 

Ag (6–1,370 ppm), Hg (0.43–1.18 ppm), As (257–4,290 ppm), 

Bi (~4–37 ppm), Cu (131–1,090 ppm), Mo (~53–1,310 ppm), 

Sb (~21–275 ppm), Se (~1–203 ppm), and Te (~4–16 ppm). 

One or two samples contain elevated concentrations of Co, 

Mn, Bi, Pb, Tl, and (or) Zn.

Fluid Inclusion Microthermometry and 

Compositions

Fluid inclusion microthermometric data have been 

obtained from samples of the Juniata, Wide West, Humboldt, 

and other veins (Nash, 1972; Osborne, 1985; Knudsen and 

Prenn, 2002), and one fluid stable isotope composition is 

reported (O’Neil and Silberman, 1974). However, most 

analyzed samples are not precisely located or paragenetically well constrained. The following microthermometry 

summary is derived largely from Knudsen and Prenn (2002), 

supplemented by deductions regarding spatial relationships 

among veins.

Fluid temperature ranges implied by inclusion homogenization in samples of vein quartz in the main part of the district 

(Silver, Middle, Last Chance, Aurora, and Humboldt Hills) 

are <180, 190–240, and >250 °C; most fluid salinities are less 

than a few weight percent NaCl equivalent. These temperature 

ranges correspond to different veins and to different layers and 

stages within veins. The episodic presence of K-feldspar in 

quartz samples with 190–240 °C fluids, and sericite alteration 

of wall-rock feldspars, suggests that fluid pH was controlled 

by the K-feldspar-muscovite stability boundary at near-neutral 

pH. Inclusion populations inferred to represent boiling at 

<180 °C occur in some clear quartz crystals, and apparently 

represent late-stage fluids. Inclusions with homogenization 

temperatures >250 °C have salinities of 3–6 weight percent 

NaCl equivalent; some contain a daughter mineral that may 

be dawsonite. Lower inclusion homogenization temperatures 

(<200 °C) in New Esmeralda area veins broadly correlate with 

relatively abundant chalcedonic quartz, implying shallower 

depths of formation. Temperature-elevation relationships of 

fluid inclusion populations show no clear district-wide trends, 

and in Juniata Mine samples they imply a “reversed” thermal 

gradient because populations with higher temperatures occur 

in vein samples collected near the present surface.

Fluid inclusions in quartz, most closely associated 

paragenetically with ore minerals in the Wide West vein and 

in veins on Silver Hill, homogenize at 230–236 °C, have 

salinities of 1–3 weight percent NaCl equivalent, and boiled 

intermittently, requiring minimum quartz depositional depths 

of 260 m (Haas, 1971) below the potentiometric surface. 

Relative to the present elevation of the Wide West vein 

(~7,600 ft), a paleopotentiometric surface (paleowater table) 

was at ~8,460 ft. Relative to present elevations of stoped veins 

on Silver Hill, ~7,800 ft at the Antelope vein to 8,400 ft at the 
Aurora Mining District 51

Figure 22. Secondary electron images of an archival vein specimen from the Crocket Mine on Last Chance Hill, Aurora Mining 

District. A, B, C, and D correspond to specimen K2085 (Keck museum collection, University of Nevada Reno). Mineral identifications 

and approximate atomic proportions for these images, and for images in figures 23 and 24, were determined petrographically and 

by scanning electron microscopy algorithms. Imaged phases include quartz, electrum with subequal Au and Ag, a Ag-As-Sb-Au-S 

mineral or intergrowth of minerals, Ag-Au-S (~Ag5.2Au1.2S4

), Ag-Sb-S-Se (~Ag5Sb0.8S3Se0.2), acanthite with minor Se, and sphalerite 

with minor Cd.

Ag5.2Au1.2S4

Ag5As0.2Sb0.2Au0.3S3

AgAu

quartz

quartz

Ag5Sb0.8Se0.2S3

Ag.52Au.47

Ag4.2As0.3Sb0.1Au0.3S3

Ag2Se0.1S

Ag.52Au.48

quartz

~Ag1.6As0.1Au0.1S

quartz

~Zn1.1Cd0.03S

Au.51Ag.49

Ag1.7S; minor Se

Ag1.7S; minor Se

A B

C D

Ag.5Au.5

200 μm 200 μm

200 μm 200 μm
52 Gold-Silver Mining Districts, Alteration Zones, and Paleolandforms in the Miocene Bodie Hills Volcanic Field

Pb0.8S

Au.93Ag.07

galena

Au.93Ag.07

Pb-P-Cl-O

quartz

Pb0.8S

Pb0.8S

Ag1.5S Ag.51Au.49

Ag.65Au.35

Ag.53Au.47

Ag.51Au.49

500 μm

500 μm 200 μm

500 μm

quartz

Ag.57Au.43

Ag.51Au.49

Ag2.5S

Ag.51Au.49

Ag1.9S; minor Se

quartz

Ag2.6S

Ag2.8S

Ag2.1S

Ag.51Au.49

Ag.52Au.48

quartz

A B

C D

ZnCd0.1S

Fig. 23

Figure 23. Secondary electron images of A, an archival vein specimen from the Antelope Mine, Silver Hill, Aurora Mining District 

(specimen K011, Keck museum collection, University of Nevada Reno). B, C, D, An archival vein specimen from the Martinez Mine, 

Martinez Hill, Aurora Mining District (specimen K208, Keck museum collection, University of Nevada Reno). Imaged phases include 

quartz, galena, electrum with variable Au and Ag, acanthite with minor Se, and sphalerite with minor Cd.
Aurora Mining District 53

Ag5.3Au4.7

Ag1.7Sb0.2S

Ag1.7Sb0.1S

Ag1.7Sb0.1S

Ag0.9Sb0.1Au0.1S

quartz

quartz

Cu2.7Sb1.6Ag1.2Zn0.7S5

Ag5.9Cu0.9Sb0.7S4

galena

CuCu2.7 2.7SbSb1.6 1.6AgAg1.2 1.2ZnZn0.7 0.7SS55 Ag7Cu0.5Sb0.9Se0.5S4

A

C

galena

200 μm

Ag5.8Cu0.1Sb0.1S4; minor Se

quartz

ZnS; minor Ag

Ag.47Au.53

Ag2.6S0.3Se

pyrite

B

chalcopyrite

200 μm

200 μm

Fig. 24

Figure 24. Secondary electron images of A, an archival 

vein specimen from the Antelope Mine, Silver Hill, Aurora 

Mining District (specimen K229, Keck museum collection, 

University of Nevada Reno). B, C, An archival vein specimen 

from the Wide West Mine, Last Chance Hill, Aurora 

Mining District (specimen K2079, Keck museum collection, 

University of Nevada Reno). Imaged phases include quartz, 

electrum with subequal Au and Ag, a Ag-Sb-S mineral 

(~Ag1.7Sb0.1S), a Ag-Sb-Au-S mineral (~Ag0.9Sb0.1Au0.1S), 

a Ag-Cu-Sb-S-Se mineral, a Cu-Sb-Ag-Zn-S mineral, 

chalcopyrite, sphalerite, pyrite, and galena.

southern extremity of the Esmeralda vein (fig. 20), paleo

potentiometric surfaces were at 8,660–9,260 ft. Although there 

is no identified Esmeralda vein microthermometry to further 

constrain paleoelevations, a paleopotentiometric surface at 

9,260 ft is near the present elevation of East Brawley Peak 

(~9,400 ft), ~1.3 km southwest of the Esmeralda vein. The 

summit of East Brawley Peak consists of densely silicified and 

clay-altered trachyandesite of Aurora. However, East Brawley 

Peak alteration zone assemblages include ~12 Ma alunite, 

and Aurora district veins formed at 10.5–10 Ma (table 1), 

precluding a close temporal link between the alteration zone 

and veins.

The stable isotope composition of fluid in an unattributed vein sample, determined by bulk analysis, is within 

the range of present meteoric waters in the Great Basin 

(δD=−124 ‰; calculated δ18O250 °C=−12 ‰; O’Neil and 

Silberman, 1974).

Sulfur Isotope Compositions of Vein Minerals

The δ34S values of sulfide minerals in Aurora district 

veins vary from −8.7 to 10.9 ‰ (table 2). This relatively 

large range may, in part, reflect sample quality in that most 

analyzed samples contain small proportions of sulfide minerals and large proportions of vein quartz. High δ34S values 

(10.9, 10.6, and 8.3 ‰) may indicate unrecognized sulfate 

minerals in the analyzed samples. Low δ34S values (−8.7, 

−8.5, −8.3, −7.0, and −6.3 ‰) are similar, in part, to those 

of sulfide minerals in the Masonic Mining District (table 2), 

which are consistent with SO2 disproportionation. Therefore, 

Aurora vein sulfide minerals may record sulfide-sulfate 

isotope fractionation, or several sulfur sources. Detailed 

paragenetic, geochronologic, and microthermometric 

investigations are needed to resolve temporal relationships 

among the numerous hydrothermal mineral assemblages in 

the vicinity of Aurora (East Brawley Peak, Spring Peak, and 

Sawtooth Ridge alteration zones).
54 Gold-Silver Mining Districts, Alteration Zones, and Paleolandforms in the Miocene Bodie Hills Volcanic Field

Wall-Rock Alteration

Several styles of hydrothermal alteration have modified volcanic rocks that enclose Aurora district veins. The 

trachyandesite of Aurora, the host rock for nearly all veins, 

has been altered throughout the district by partial to complete 

replacement of plagioclase, hornblende, clinopyroxene, 

and biotite phenocrysts, and matrix minerals, to variable 

proportions of chlorite, albite, calcite, montmorillonite, and 

lesser fine-grained quartz, sericite, and pyrite (iron oxides). 

Although few continuous exposures exist, these gray-green to 

greenish propylitized rocks apparently extend to contacts with 

younger rocks. The critical relationship between propylitized 

trachyandesite that encloses the Esmeralda vein and quartzalunite-clay-mica-altered trachyandesite of Aurora of the East 

Brawley Peak alteration zone is masked by float, and crosscutting relationships that might distinguish the two alteration 

assemblages have not been observed. The distribution of 

epidote, which occurs in thin veins (≤1 mm) in trachyandesite 

on mine dumps along Aurora Creek east of the Esmeralda vein 

(for example, Dream adit), may reflect older, high temperature 

fluids that formed the East Brawly Peak alteration zone. 

Elevated fluid temperatures in altered rocks on East Brawley 

Peak, and minor element zonation in the Aurora Mining 

District (Breit, 2000) also support alteration of trachyandesite 

of Aurora in the southwestern part of the district prior to vein 

deposition.

Gray-lavender trachyandesite adjacent and internal 

to Aurora district veins is variably replaced by quartz and 

K-feldspar, which partially obscure primary porphyritic 

texture. Light-gray to beige trachyandesite, adjacent to and 

in vein zones, reflects alteration of K-feldspar to sericite, 

illite, quartz, pyrite, and montmorillonite, and replacement of 

trachyandesite phenocrysts and matrices by these minerals. 

In densely veined trachyandesite, quartz replacement is more 

pronounced between and adjacent to veins. Quartz-K-feldsparsericite-illite-pyrite-montmorillonite alteration grades distally 

from veins into propylitized trachyandesite, although pyrite 

is most abundant in vein selvages and in internal fragments 

of trachyandesite. Vein K-feldspar and sericite occur in 

aggregates, seams, and pockets (millimeters to centimeters in 

size) in quartz.

ASTER Imagery

ASTER imagery (Rockwell, 2010) of the Aurora 

Mining District shows diffuse and small clusters of pixels 

that extend from Silver Hill to Gregory Flat (fig. 20); these 

pixels correspond to illite and lesser quartz. Densely clustered 

pixels coincident with the Prospectus, Humboldt, and Juniata 

open pits, dumps, and tailings correspond to quartz and 

montmorillonite ± kaolinite.

SWIR Spectra

SWIR analyses of hand samples of propylitized 

trachyandesite from the Del Monte shaft, and from other mine 

dumps on Last Chance Hill and Silver Hill, show weak spectra 

characteristic of illite and montmorillonite, and less-prevalent 

chlorite and epidote. Brecciated and veined rhyolite of Aurora 

Creek in the small open cut ~ 0.6 km northeast of the Aurora 

cemeteries contains kaolinite and montmorillonite.

Hydrothermal Mineral Ages

The 40Ar/39Ar dates of adularia from the Esmeralda 

vein, and in a vein sample from the Del Monte shaft 

dump are 10.47 ± 0.1 Ma and 10.35 ± 0.05 Ma, respectively 

(fig. 20; table 1). Breit (2000) reported a 40Ar/39Ar date of 

10.04 ± 0.03 Ma for adularia in the Prospectus vein. Kleinhampl and others (1975) reported a K-Ar date of 10.6 ± 0.2 Ma 

for adularia in an unnamed quartz-adularia vein. Morton 

and others (1977) reported a K-Ar date of 10.9 ± 0.3 Ma for 

trachyandesite altered to quartz, K-feldspar, sericite, pyrite, 

and chlorite in or near the Juniata vein. Breit (2000) reported 

a 40Ar/39Ar date of 12.2 ± 0.3 Ma for illite in altered wall rocks 

adjacent to the Esmeralda vein.

Most hydrothermal mineral dates are ~2–3 m.y. 

younger than the age range of trachyandesite of Aurora 

(~13.1–12.6 Ma; table 1), the host rock for nearly all veins, 

and ~1.5–2 m.y. younger than alunite in trachyandesite of 

Aurora on East Brawley Peak (~12 Ma; table 1) adjacent to 

Silver Hill. No known magmatism in the Aurora Mining District is coeval with vein and most hydrothermal mineral dates, 

whereas in the Masonic and Bodie Mining Districts, igneous 

rocks are coeval with, or ~ 0.5 m.y. older than, hydrothermal 

mineral dates (table 1). However, most feldspar and biotite 

dates of Rhyolite of Bodie Creek and Trachyandesite of Del 

Monte, ~ 4 –5 km southwest and north, respectively, of the 

Aurora townsite (fig. 20), are ~10–11 Ma (Fleck and others, 

2015), indicating the presence of magmas near the Aurora 

Mining District during vein deposition.

Four Corners Alteration Zone

Location

Sec. 15, T. 5 N., R. 26 E., Mono County, California (fig. 1)

Definition

The Four Corners alteration zone (FC AZ) is defined by 

low outcrops of silicified, volcanic-hydrothermal breccia that 

cover < 0.02 km2 immediately northwest of the intersection 

of roads to Masonic, Aurora Canyon, Cow Camp, and Bodie 

(Four Corners; fig. 25).
Four Corners Alteration Zone 55

Figure 25. A, Geologic map of the Four Corners alteration zone, Mono County, California. B, Image showing 

figure 26C and location.

Tac Tac

Tma

Tma

Trs

Trs

Qc

Qc

Tsb

Tsb

Qc

Qc

21

23

0 0.125 0.25

0 0.25 0.5

MILE

KILOMETER

Photograph location

EXPLANATION

40

Colluvium

Trachyandesite of Aurora Canyon

Rhyolite of Rock Springs Canyon

Silicified breccia

Trachyandesite of Masonic

Paleosol

Contact—Dashed where approximated

Fault—Dashed where approximated

Bedding

Tac

Tma

Tsb

Trs

Masonic

Bodie

Aurora Canyon

Cow Camp

◄

◄

◄

◄

Four 

Corners

Trench

B

A

Base modified from U.S. Geological Survey

Dome Hill, Calif.-Nev., 1989, 1:24,000

Fig. 25

119°15' 119° 118°45'

38°25'

38°15'

38°05'

CALIFORNIA

NEVADA

Mono Lake

Mono Valley

Bridgeport

Fletcher Valley

East

Walker

River

Masonic

Bodie

Aurora

Area of map

N
56 Gold-Silver Mining Districts, Alteration Zones, and Paleolandforms in the Miocene Bodie Hills Volcanic Field

History and Production

No production is recorded from the FC AZ. A short 

bulldozer cut in argillized trachyandesite of Masonic, 

about 50 m north of the silicified breccia outcrops, is the 

only surface disturbance indicative of mechanized mineral 

exploration. Extensive production of tools and implements by 

Native Americans is evident from the scatter of locally derived 

obsidian flakes.

Stratigraphy

Two low outcrops of silicified breccia lying on a paleosol 

in a window of the trachyandesite of Masonic are exposed 

between domes of rhyolite of Rock Springs Canyon to the 

north and trachyandesite of Aurora Canyon to the south 

(fig. 25). The rhyolite of Rock Springs Canyon forms two 

prominent, small-volume, aphyric lava domes that include 

flow lobes entirely composed of grayish-black obsidian. It 

contains trace to 3 volume percent phenocrysts of plagioclase, 

sanidine, hornblende, and biotite in a weakly devitrified, 

locally glassy groundmass.

The two outcrops of silicified breccia are crudely bedded 

and form an outward-dipping semicircle that is tentatively 

interpreted as eruption breccias and overlying hydrothermal 

sediments. These features partly outline a hydrothermal 

eruption crater that was centered about 200 m west of the 

road intersection (figs. 25, 26). A prominent zone of dark-red 

clay underlies the breccias and overlies the trachyandesite 

of Masonic on the north and east sides of the breccias and 

extends approximately 700 m northeast along Cow Camp 

road. The clay zone is interpreted as a paleosol developed on 

the trachyandesite of Masonic, although parts of the clay zone 

near the breccia outcrops may have a hydrothermal origin and 

formed at the same time as the breccias. The breccias contain 

a variety of shallow hydrothermal features including finely 

bedded and crossbedded siliceous sediments filling small 

open spaces (cavern fill) and silicified hematitic muds and 

dripstones (fig. 26).

Structure

The silicified outcrops are crudely bedded with north to 

northeast strikes and shallow (~20°) northwest to east dips 

(fig. 25). A proposed northeast-trending fault southeast of the 

breccia outcrops has no apparent temporal relationship to the 

alteration zone.

Hydrothermal Alteration

Breccia clasts and matrix consist of quartz, hematite, 

jarosite, kaolinite, and montmorillonite. Ten samples of silicified breccia and sediments contain low concentrations of Au 

(≤5–61 ppb) and Ag (<1 ppm; table 1-8). All samples contain 

tens to >100 ppm Sb, and several samples contain elevated 

concentrations of Hg (6–15 ppm), As (hundreds to several 

thousand parts per million), Bi (~2–135 ppm), and Pb (hundreds 

of parts per million); one sample contains 18 ppm Te.

ASTER Imagery

No hydrothermal minerals were identified from 

ASTER imagery.

SWIR Spectra

Based on SWIR analyses, two samples of red clay 

underlying the breccia outcrops contain montmorillonite and 

kaolinite. Silicified breccias locally are coated by orangecolored jarosite ± montmorillonite.

Hydrothermal Mineral Ages

Hydrothermal minerals in the FC AZ have not been 

dated. Field relations indicate that the alteration zone is 

younger than ~15–14 Ma trachyandesite of Masonic and 

older than the 10.6–10.3 Ma trachyandesite of Aurora Canyon 

(table 1).

Paramount-Bald Peak Alteration Zone

Location

Tps. 5 and 6 N., Rs. 26 and 27 E., mostly unsurveyed, Mono 

County, California, and Mineral County, Nevada (fig. 1)

Definition

The Paramount-Bald Peak alteration zone (PBP AZ) is in 

the central and northeastern part of the Bodie Hills volcanic 

field and mostly coincides with the sedimentary rocks and tuff 

of Paramount (Tpst, fig. 27). The alteration zone includes 

three principal exposures of strongly altered rocks in a 1- to 

3-km-wide, northeast-elongate area that extends about 12 km 

from the northeast flank of Potato Peak to the north side of 

Bald Peak. The largest exposure is in the southwestern part 

of the alteration zone, covers about 12 km2

, and includes the 

Paramount Hg Mine. The southwest and central exposures 

most likely are contiguous beneath lava flows of the Pliocene 

Beauty Peak volcano.
Paramount-Bald Peak Alteration Zone 57

Figure 26. Images of hydrothermal features, Four Corners alteration zone. A, Outcrop of crudely bedded silicified breccia. Lower part 

of outcrop is hematite-rich and massive, whereas upper part contains layers of gray, finely bedded sedimentary strata. B, Close up view 

of massive hematite-rich silicified breccia in lower part of outcrop. C, Finely crossbedded, chemical and clastic sedimentary beds filling 

cavity in silicified breccia. D, Silicified hematitic mud coating cavity surface. Branching texture of grooves and ridges suggests flow from 

top to bottom.

A B

C D

Fig. 26
6

5

8

7

7

5

5

20

7

35

28

30

26

24

21

28

22

10

25

90

26

24

12

20 10

23

17

18 34

28

11

11

18

48

30

40

23

15

10

23

20 15

15

27

13

22

21

31

20

32

15

25

20

20

25

10

25 20

25

28

30

18

22 18

30

18

27

Tma

Tmai

Qal

Qal

Trb

MINERAL COUNTY

MONO COUNTY

Tmai

Tma

Tma

Tma

Tma

Tma

Tma

Tma

Qal Tev

Tac

Tac

Tac

Tac

Qacc

Trcd

Tdm

Tra

Trb

Qac

Trbc

Trb

Trb

Tpst

Tpst Tpst

Tdi

Tdi

Tpst

Tpst

Qacc

Qacc

Trcd

Qt

Qt

Qt

Qt

Qt

Qt

Qt Qt

Qt

Qt Qal

Qal

Tpp

Tpp

Tpp

Tev Tev Tev

Tev

Tev

Tba

Qal

Qal

Qa

Tg

Tba

Qal

Qal

Qal

QalQpl

Qpl

Qal

Tev

Tev

Tba

Qal Tpr

Tpr

Tpr

Tev

QTg

QTg

Tg

Tg

Tg

Tev Tba

Tev

Tac Tev

figure 28

Paramount 

Mine hill 

Paramount Mine area 

sinter group

Hydrothermal

crater

Hilton Springs

Sinters

Potato Peak

(~1.5 km ssw)

Atastra Creek

sinter

Sinter g

of Ba

Bald Peak

Beauty Peak

Bald Peak Flats

Bald Peak 

Adit

0 0.5

0.50

1 MILE

1 KILOMETER

119°04' 119°02' 119° 118°50'

38°20'38°18'38°16'

Base modified from U.S. Geological SurveyDome Hill, Calif.-Nev., and Aurora, Nev.-Calif., 1989, 1:24,000
Paramount-Bald Peak Alteration Zone 59

Figure 27. (Facing page) Geologic map of the Paramount-Bald Peak alteration zone, Mono County, California, and Mineral County, Nevada, 

showing sinters, sinter groups, and prospects discussed in the text (modified from John and others, 2012).

Landslide—Head or main scarp of 

landslide. Hachures point down-slide

Contact

20

22

EXPLANATION

Fault—Dashed where approximated, 

dotted where concealed

Landslide deposits

Alluvium

Talus deposits

Playa deposits

Older gravel deposits

Gravel deposits

Trachyandesite of Cow Camp Creek

Basaltic trachyandesite of Beauty Peak

Hornblende trachydacite

Trachydacite of Potato Peak

Eureka Valley Tuff

Sedimentary rocks and tuff of Paramount

Rhyolite of Bald Peak

Trachyandesite of Aurora Canyon

Gravel deposits

Rhyolite of Bodie Creek

Trachyandesite of Del Monte

Pyroxene rhyolite

Dacite intrusions

Rhyolite of Aurora Creek

Trachyandesite of West Brawley Peak

Trachydacite of Rough Creek

Trachyandesite intrusion of Masonic

Trachyandesite of Masonic

Vertical dike

Bedding

Foliation

Sinter

Group of sinters at common elevation

Hydrothermal crater

Qal

Qt

Qpl

Qog

QTg

Tba

Thd

Tpp

Tev

Tpst

Trb

Tac

Tg

Tdm

Tpr

Tdi

Trbc

Tra

Twba

Trcd

Tmai

Tma

Qacc

119°15' 119° 118°45'

38°25'

38°15'

38°05'

CALIFORNIA

NEVADA

Mono Lake

Mono Valley

Bridgeport

Fletcher Valley

East

Walker

River

Masonic

Bodie

Aurora

Area of map
60 Gold-Silver Mining Districts, Alteration Zones, and Paleolandforms in the Miocene Bodie Hills Volcanic Field

History and Production

The Paramount Hg Mine is in the southwestern part of 

the alteration zone (sec. 13 [projected], T. 5 N., R. 26 E.). 

Numerous small prospects, trenches, and drill roads have been 

excavated near the Paramount Mine and in the vicinity of 

Bald Peak in the central part of the zone. Although Homestake 

Mining Company explored the area in the 1980s, drill roads 

and cuttings west of Bald Peak may include pre-1976 Federal 

Land Policy and Management Act (FLPMA) exploration 

because of limited to no site reclamation. At the Paramount 

Mine, Hg was recovered from a chalcedonic quartz vein 

exposed by two adits, tens of meters of underground workings, 

and two large trenches (fig. 28). The vein was mined about 

1878 (Whiting, 1888), and from 1941 to 1944 at a reported 

grade of 1.5–5 pounds (lbs) of Hg per ton (Holmes, 1965). 

According to an unpublished historical compendium filed with 

regulatory agencies for drilling permitting in 2009, 400 t were 

also mined and processed in 1968. The volume of calcines 

associated with a dismantled retorting facility at the lower adit 

and reported mercury grades indicate that total Hg production 

was probably tens of flasks. The historical compendium also 

lists trench excavation in the late 1960s, and drilling programs 

by Homestake, Molycorp, Noranda, and Equinox from ~1981 

to 1991. From 2006 to 2010, approximately 10 holes were 

permitted and (or) drilled by Cougar Gold at the mine and at 

various sites on the hill southwest of the mine.

Stratigraphy

Sedimentary rocks and tuff of Paramount cover most 

of the PBP AZ (John and others, 2012). This stratigraphic 

sequence lies on the north and west flanks of the ~9.7 Ma 

rhyolite of Bald Peak dome. It includes abundant rhyolite 

tuffs inferred to have erupted from Bald Peak, and 

rhyolite-rich detritus shed from the dome into the shallow, 

northeast-elongate Paramount basin (fig. 27). The sequence 

unconformably overlies ~15 to 14 Ma trachyandesite of 

Masonic, ~11.3 Ma trachydacite intrusions, ~11 Ma trachyandesite of Del Monte, ~11.3 Ma trachydacite intrusions, 

and ~10.6 to 10.4 Ma domes of the trachyandesite of Aurora 

Canyon. Altered sedimentary rocks of the sequence may be 

temporally equivalent to unaltered coarse gravel deposits 

that extend northeastward into Fletcher Valley (Tg, fig. 27). 

A prominent dark-red paleosol developed locally on rocks 

underlying the sequence is exposed ~0.75 km northeast of 

the Paramount Mine. The sequence is overlain by ~9.4 Ma 

Eureka Valley Tuff, by lava flows of ~9 to 8.7 Ma trachydacite of Potato Peak, and by basaltic trachyandesite lava flows 

of the Pliocene Beauty Peak volcano.

The sedimentary rocks and tuff of Paramount consist of 

interbedded, crystal-poor, lithic-rich and pumice-rich rhyolite 

tuff, minor, sparsely porphyritic, flow-banded rhyolite 

(possibly intrusive), and poorly sorted volcaniclastic rocks 

that include volcanic conglomerate, sandstone, and siltstone. 

Several sinter terraces and numerous sinter beds are dispersed 

throughout the alteration zone (figs. 27, 28, 29, 30). Pyroclastic rocks vary from unwelded, pumice-rich ash flows that 

locally contain abundant clasts of nearly aphyric flow-banded 

rhyolite and porphyritic trachyandesite and dacite lavas, 

to finely bedded, possibly water lain, crystal-poor air fall 

tuffs. Clastic sedimentary rocks contain clasts of porphyritic 

volcanic rocks, including quartz-bearing dacite (?), and 

less-abundant sparsely porphyritic, flow-banded rhyolite. The 

sequence may be as much as 200 m thick on the west side of 

Rough Creek, although irregular dips and complex structure 

preclude an accurate estimate of thickness in most locations. 

The sedimentary rocks and tuff are pinkish-gray to pale-redpurple, nearly aphyric, weakly to strongly hydrothermally 

altered and locally iron stained. Pyroclastic rocks contain 

trace amounts of plagioclase and quartz phenocrysts in a 

recrystallized ashy groundmass. The tuff contains abundant, 

0.5–10 cm unflattened pumice blocks and exotic lithic 

fragments composed of porphyritic, intermediate-composition 

lava and nearly aphyric rhyolite lava.

The rhyolite of Bald Peak contains trace to 10 volume 

percent fine-grained phenocrysts of quartz, sanidine, and 

lesser biotite and clinopyroxene in hydrated to devitrified 

glass.

Structure

The structure of the PBP AZ is poorly understood 

because of discontinuous stratigraphy within the sequence, 

pervasive hydrothermal alteration, numerous large landslides, 

and lack of a detailed geologic map of most of the alteration 

zone. Faults on figure 27 are inferred on the basis of offset 

contacts between the sedimentary rocks and tuff of Paramount 

and underlying lava flows (trachyandesites of Masonic and 

Del Monte), prominent linear zones of silicification, and variable elevations of sinter terraces. The sedimentary rocks and 

tuff of Paramount appear to fill a shallow northeast-trending 

basin (Paramount basin) on the northern and western flanks of 

the Bald Peak rhyolite dome which probably formed during 

emplacement of the dome (fig. 27; John and others, 2012). The 

Paramount basin appears to be bounded by northeast-striking 

growth(?) faults that were active during sediment deposition 

in the basin. A series of north-striking faults apparently 

displaces sinter terraces to progressively lower elevations 

from about 9,090 ft on the hill southwest of the Paramount 

Mine, to 8,700 ft at the Paramount Mine, 8,080 ft in Atastra 

Creek, 7,800 ft on the west side of Bald Peak, and ~7,200 ft 

on the north side of Bald Peak (fig. 27). The pattern of inferred 

northeast and north-striking faults is similar to fault patterns 

observed in the Masonic and Aurora Mining Districts (John 

and others, 2012).
Paramount-Bald Peak Alteration Zone 61

70

A

J

K

E

M

L

K

I

N

D

C

B

F

G

H

P

Q1

Q

BB

AA

30

25

45

var.

10-15

5-20

5

15

10-15

Paramount 

Mine hill

PARAMOUNT 

Hg MINE sinter

breccia

building

0 0.25 0.50 MILE

0 0.25 0.50 0.75 KILOMETER

1 m

40

EXPLANATION

Qc

Colluvium

Dismembered sinter terrace

Strongly silicified volcaniclastic rocks (Tpst) ± sinter

Sedimentary rocks and tuff of Paramount (John and 

others, 2012)—Pervasively altered to quartz, 

montmorillonite, and lesser kaolinite and pyrite

Quartz-cinnabar-pyrite vein

Contact—Dashed where approximated

Fault—Dashed where approximated, dotted where 

concealed

High-angle normal fault—Bar and ball on downthrown 

block

Bedding

Mine dump or trench

Sample site and letter

dst

dst

Tpst

vc/s

vc/s

vc/s

vc/s

dst

Qc

Qc

Photograph location

Qc

vc/s

dst

Tpst

A B

Base modified from U.S. Geological Survey

Dome Hill, Calif.-Nev., 1989, 1:24,000

Fig. 28

N

119°15' 119° 118°45'

38°25'

38°15'

38°05'

CALIFORNIA

NEVADA

Mono Lake

Mono Valley

Bridgeport

Fletcher Valley

East

Walker

River

Masonic

Bodie

Aurora

Area of map

Figure 28. A, Geologic map of the Paramount Hg Mine area, Mono County, California. B, Image showing unoriented, multisized 

blocks of terrace sinter cemented by fine-grained quartz and minor iron oxide minerals (similar to figure 30G).
62 Gold-Silver Mining Districts, Alteration Zones, and Paleolandforms in the Miocene Bodie Hills Volcanic Field

Figure 29. Images of Paramount-Bald Peak alteration zone. A, View looking east at altered rocks in the southwest 

part of the Paramount basin overlain by unaltered lava flows from Pliocene Beauty Peak volcano (Tba). B, View 

looking northeast from Paramount Mine at a hill composed of altered sedimentary rocks and tuff of Paramount (Tpst) 

unconformably overlying a red paleosol developed in underlying trachyandesite of Masonic (Tma). C, View looking 

southwest at Paramount Mine hill from the hill in center of B. Paramount Mine hill consists of dismembered sinter 

terraces and altered volcaniclastic rocks. D, View of silicified ledges of the Hilton Springs prospect overlain by Beauty 

Peak lava flows (Tba) at upper right. Most of the rocks in the foreground are part of a large landslide. E, Typical leached, 

argillically altered, pumiceous volcaniclastic deposits in sedimentary rocks and tuff of Paramount (Tpst). F, Cinnabar in 

a chalcedonic quartz vein at the Paramount Mine.

A B

C D

E F

Fig. 29
Paramount-Bald Peak Alteration Zone 63

Figure 30. Images of hydrothermal features in the Paramount-Bald Peak alteration zone. A, Brecciated sinter 

recemented with red chalcedonic quartz on the northwest side of Paramount Mine hill. B, Flow textures in siliceous, 

hematitic, mud-sized sedimentary strata that coat silicified volcaniclastic rocks about 1 km southeast of the Paramount 

Mine. C, Desiccation cracks in thin pool(?) sinter bed in silicified volcaniclastic rocks on top of Paramount Mine hill. 

D, Quartz vein showing replacement texture of coarse bladed carbonate on south side of hill about 1 km southwest of the 

Paramount Mine. E, Sinter beds in Atastra Creek. F, Hydrothermal fluid vent on the sinter terrace in Atastra Creek.

A B

C DD

E F
64 Gold-Silver Mining Districts, Alteration Zones, and Paleolandforms in the Miocene Bodie Hills Volcanic Field

Hydrothermal Alteration

Sedimentary rocks and tuff of Paramount are pervasively 

altered throughout the Paramount basin. Older units underlying and along margins of the basin also are altered locally, 

whereas younger units surrounding or overlying the basin 

generally are unaltered (small exposures of the basal(?) 

member of the Eureka Valley Tuff are locally altered in Atastra 

Creek). Three types of alteration affected sedimentary rocks 

and tuff of Paramount (1) silicification, (2) advanced argillic 

(kaolinite ± dickite) alteration, and (3) intermediate argillic 

(montmorillonite ± kaolinite) alteration. Propylitic alteration 

assemblages (montmorillonite, illite/smectite, chlorite (?), and 

calcite) occur locally in underlying, intermediate composition 

lava flows and volcaniclastic rocks. Variable amounts of iron 

oxide minerals and jarosite are widespread, and relict pyrite is 

present in some silicified rocks.

Intermediate argillic alteration assemblages, the most 

common assemblages in strata of the Paramount basin, are 

manifested by variable leaching of pumice and volcanic rock 

clasts that left a porous residue of silica and clay minerals 

(fig. 29E). SWIR spectrographic analyses indicate that the clay 

minerals are montmorillonite and lesser kaolinite. These leached 

and clay-altered rocks are white, beige, or pale green. Pyrite 

casts are scarce to absent suggesting that this alteration type 

included little pyrite. With increasing silica content, intermediate argillic alteration grades into silicification as exposed in the 

bluffs on the southeast side of Paramount Hill (fig. 28).

Smaller areas of intense silicification and advanced 

argillic alteration occur locally within the broad expanse of 

strata that are altered to intermediate argillic assemblages. 

Silicified rocks consist of variably colored, commonly iron 

oxide-stained, chalcedonic silica and lesser quartz. Domains 

that contain relict, disseminated, fine-grained pyrite occur 

locally. Silicified rocks generally form bold outcrops and 

comprise both elongate cliff-forming ledges and more tabular 

bodies. Breccia zones are common within silicified rocks. 

Small zones of advanced argillic alteration locally surround or 

underlie zones of silicified rock, notably near sinters. Kaolinite 

is the predominant clay mineral, although dickite is present in 

several locations including in narrow veins beneath the sinter 

terrace on Atastra Creek. Alunite was not confirmed in hand 

samples, although interpretation of ASTER imagery shows 

alunite occurrences in several places on the southwest side of 

the Paramount basin (Rockwell, 2010).

Sinter occurs in thin beds (< 0.3 m) interstratified with 

strongly silicified volcaniclastic rocks, and forms terraces, 

several meters in thickness, that generally overlie silicified 

volcaniclastic rocks (figs. 27, 28, 29). The largest exposures 

of sinter are near the Paramount Mine (below). Another large 

sinter terrace, ~5 m thick, crops out on the west side of Atastra 

Creek about 1.25 km southeast of its confluence with Rough 

Creek. This terrace overlies kaolinite-altered volcaniclastic 

rocks. A small funnel-shaped vent, desiccation cracks, and 

filamental bacteria mats are exposed on the upper surface 

of the terrace (fig. 30). Dark-gray siltstone that underlies 

part of the terrace may represent mud pot deposits. A third, 

large terrace is exposed in cliffs above Rough Creek about 

2.7 km north-northeast of Bald Peak at the northeast end of 

the alteration zone (fig. 27). Porous, poorly indurated sinter 

~5 m thick is exposed for ~50 m along strike. More strongly 

indurated sinter, locally containing fossilized reeds, forms thin 

terraces and clusters of sinter blocks at several other locations 

in this area of volcaniclastic rocks (fig. 27).

Quartz veins, and quartz-chalcedony veins and stockworks are broadly distributed in the Paramount basin (fig. 27). 

Veins and stockworks occur (1) at the Paramount Hg Mine, 

(2) on the top and south side of the hill 1.5 km southwest of 

the Paramount Mine, (3) on the east side of Atastra Creek east 

of the sinter terrace, (4) near sinter beds on the west side of 

Bald Peak (Hilton Springs or Golden Beauty prospect), (5) on 

the west side of Bald Peak along the California-Nevada state 

boundary (Bald Peak Flats prospect), and (6) about 1.2 km 

northwest of Bald Peak (Bald Peak Adit prospect).

Paramount Mine Area

The chalcedonic quartz vein mined for mercury in the 

Paramount Mine trends N50°W, dips 70°NE, and is as much 

as 2 m wide. It is exposed in mine workings on the west side 

of a low domal hill composed of silicified and illite-clay 

mineral-altered volcaniclastic rocks (Paramount Hill; fig. 28). 

The vein consists of dense chalcedonic quartz and lesser 

clay minerals, and small amounts of pyrite, cinnabar, and 

metacinnabar. The clay minerals, mostly montmorillonite 

and kaolinite, occur in irregular, millimeter-wide seams and 

in centimeter-sized pockets that represent partially leached 

wall-rock fragments. Clasts and matrix of volcaniclastic 

deposits exposed in trenches across the vein and at the 

upper adit are altered to kaolinite and lesser opaline silica 

and montmorillonite for several meters on both sides of the 

vein. Remnants of at least five sinter terraces, and a sixth 

disaggregated and silicified terrace (figs. 28, 29), are adjacent 

to the vein on the west and north sides of the hill, at the 

southeast base of the hill, and ~0.8 km east of the mine. The 

former terraces have been dismembered by substrate deflation 

and freezing; they are represented by areas of closely spaced, 

rotated blocks of sinter and volcaniclastic strata, many of 

which are meters in dimension. Occurrences of disaggregated 

and silicified sinter are indicative of gravitational instability 

during terrace construction.

Minor Elements in Rocks

Samples from the sinter terraces on the north and 

west side of Paramount hill contain variably elevated 

concentrations of Au (as much as 32 ppb), Ag (<1 ppm), Hg 

(≤ 2.7 ppm), As (≤ 90 ppm), Sb (≤ 396 ppm), and W (≤14.4 

ppm; table 1-9). Two samples of finely laminated, dark-gray 

chalcedonic pool sinter (?) from the top of Paramount Hill 

contain elevated concentrations of Au (0.92; 3.57 ppm), Ag (3; 

6 ppm), Hg (1.5; 4.3 ppm), As (19; 38 ppm), Sb (82; 130 ppm) 
Paramount-Bald Peak Alteration Zone 65

and Tl (1.8; 4.7 ppm). Samples of quartz-chalcedony veins 

and altered wall rocks from the flat ridge southeast of 

Paramount hill contain locally elevated concentrations of 

Au (7–740 ppb), Ag (<1–13 ppm), Hg (<1,600 ppm), As 

(<170 ppm), Ba (217–1,500 ppm), Sb (<916 ppm), and W 

(<28.9 ppm).

Minor element concentrations along a continuous 

traverse orthogonal to sinter beds (determined by LA ICPMS; fig. 31), include local (submillimeter) enrichment of Hg, 

Ag, Bi, As, Pb, and Cu. Bulk analyses of the traversed beds 

show a slightly elevated Hg concentration; concentrations 

of other elements are within the range of other bulk sinter 

samples. Minor element concentrations along a continuous 

traverse across the chalcedonic quartz vein mined for Hg 

(fig. 32) include local (submillimeter) enrichment of Au, Ag, 

S, Hg, Fe, As, Sb, Cu, Mo, Sn, and Zn. Bulk analyses of the 

traversed vein indicate elevated concentrations of Hg, Au, 

Sb, and S that are within the range of other vein samples, 

but many other elements have elevated concentrations at the 

millimeter scale (for example, Cu, Mo, and Zn) that are not 

elevated in bulk samples.

A rotary drill hole sited in the vicinity of the Paramount 

Mine encountered “volcanic breccias and pyroclastic rocks 

to a depth of 230 feet”, and “dacite and andesite flows” from 

230 to 425 ft, the total depth of the hole (Silberman and 

Berger, 1985). The andesite and dacite flows are likely either 

the trachyandesite of Masonic or trachyandesite of Aurora 

Canyon (fig. 27). Alteration of these rocks includes “moderate 

to intense silicification, argillic alteration, and chloritization” 

with 2–10 volume percent pyrite. Minor element concentrations in cuttings include intervals of >1 ppm Au (maximum 

1.9 ppm) from 100 to 160 ft above the oxide-sulfide boundary, and 0.5–1 ppm Au from 215 to 240 ft. These intervals 

partly coincide with chalcedonic quartz veins. Other elevated 

element concentrations include As (mostly hundreds to 

>1,000 ppm), Sb (mostly hundreds of parts per million), Tl 

(parts per million to tens of parts per million), Ag (mostly 

parts per million), and Hg (parts per million to several tens 

of parts per million; Silberman and Berger, 1985). These and 

other element concentrations (B, Mn, Sr, Ba, Cr, Mo, Ni, Zn, 

Pb, V, Co, and Cu) have marginal to no clear relationship to 

the >1 ppm Au zone, the oxide-sulfide interface, and to the 

total sulfide content.

Veins as much as 0.3 m wide on the hill 1.5 km 

southwest of the Paramount Mine contain internal fragments 

of volcaniclastic wall rocks. These veins are enveloped by 

centimeter-wide selvages of wall rocks altered proximally 

to kaolinite and distally to illite/montmorillonite, both of 

which occur with minor amounts of pyrite; these minerals 

are interpreted as hypogene. The veins are prominently to 

indistinctly layered. The centers of most veins are elongate 

voids partly filled with tabular encrustations of submillimeter, 

euhedral quartz crystals on relict bladed calcite crystals 

(perimorphs), most of which have been leached. Vein samples 

contain variably elevated concentrations of Au (<2 ppm), Ag 

(<7 ppm), Hg (<34 ppm), As (tens to hundreds of parts per 

million), Ba (<2,500 ppm), Sb (tens to hundreds of parts per 

million), and Tl (<13.7 ppm; table 1-9).

Atastra Creek Area

In the Atastra Creek sinter terrace, minor element 

concentrations, determined by LA ICP-MS, along a continuous traverse orthogonal to sinter beds (fig. 33) include local 

(submillimeter) enrichment of Sb, As, Ag, Hg, Tl, Sr, Ba, Cu, 

Pb, and Fe. Bulk analyses of the traversed beds also show 

slightly elevated concentrations of some of these elements 

(As, Hg, Sb, and Tl).

In a road bed east of the Atastra Creek sinter terrace, 

blue-gray, pyritic, chalcedonic quartz veins are poorly 

exposed in a window of Miocene rocks beneath Pliocene 

basaltic trachyandesite of Beauty Peak lava flows. The veins 

are as much as 4 cm wide, contain 5–10 percent pyrite, and 

are within kaolinite-montmorillonite-altered lower(?) member 

rocks of the Eureka Valley Tuff. Vein samples contain low 

concentrations of Au (<5 ppb), and Ag (<1 ppm), and elevated 

concentrations of Hg (4.7–13.4 ppm), As (47–122 ppm), Sb 

(96–255 ppm), and W (70–123 ppm; table 1-9).

Bald Peak Area

Chalcedony veins and thin beds of sinter are exposed 

at the Hilton Springs (Golden Beauty) prospect on the west 

side of Bald Peak overlooking Rough Creek (fig. 27). Several 

narrow zones of centimeter-wide, sheeted chalcedony-pyrite 

veins cut strongly argillized and silicified sedimentary rocks 

and tuff of Paramount that underlie Pliocene Beauty Peak lava 

flows. The veins strike north-northeast and dip 75–90°NW. 

Samples of vein and silicified, pyritic wall rock contain 

elevated concentrations of Au (1.6–2.6 ppm), Ag (7–18 ppm), 

Hg (4–44 ppm), As (290–640 ppm), Ba (<2,800 ppm), Sb 

(55–77 ppm), and W (5–16 ppm; table 1-9). Several thin 

(≤ 2 cm) beds of dark-gray to black, very finely laminated 

chalcedonic sinter are interbedded with or overlie silicified 

sedimentary rocks of the unit (figs. 29, 30). Samples of 

the silicified sedimentary rocks and sinter contain variably 

elevated concentrations of Au (0.02–0.5 ppm), Ag (1–8 ppm), 

Hg (0.2–5 ppm), As (40–380 ppm), Ba (<2,500 ppm), Sb 

(220–370 ppm), and W (3–21 ppm; table 1-9).

Beds of silicified sedimentary rocks and tuff of Paramount are cut by narrow (mostly < 2 cm) opal-chalcedony 

veins at the Bald Peak Flats prospect along the CaliforniaNevada boundary about 1 km west-southwest of Bald Peak 

(fig. 27). Several zones (meters wide) containing banded veins 

(centimeters thick) strike north-northeast to northeast and 

dip steeply to the southeast. L.J. Peters (written commun., 

2004) reported partial chemical analyses for six vein samples 

from the Bald Peak Flats prospect: Au (< 3–106 ppb), Ag 

(0.08–0.54 ppm), As (99–1,290 ppm), and Hg (1.6 – 49 ppm).
Figure 31. A, Image showing oriented consecutive sections of sinter from a dismembered terrace at the western base of Paramount Mine hill, Param

zone. B, Graphs showing relative element concentrations in sinter measured in counts per second (counts/second) by laser ablation inductively coupspectrometry (LA ICP-MS). C, Bulk sample element concentrations determined by inductively coupled plasma-mass spectrometry (ICP-MS). Locally eelement concentrations include Au, Ag, S, Hg, Fe, As, Sb, Mo, Cu, Pb, Zn, and numerous other elements, only some of which are elevated in the bulk s

Line of traverse

1 cm

Paramount Mine sinter (PMT06-2)

cps

Counts/second Counts/second Counts/sec

102 104 106 102 104 

102 104 106 102 104 106

A B

27Al

12C

44Ca

23Na

31P

36Cl

39K

66Zn

208Pb

95Mo

118Sn

63Cu

34S

57Fe

197Au

121Sb

107Ag

75As

57Fe

202Hg

34S
Figure 32. A, Image showing oriented consecutive sections of a chalcedonic quartz vein exposed at the upper adit of the Paramount Mine, Pa

alteration zone (fig. 28). B, Graphs showing relative element concentrations in quartz vein measured in counts per second (counts/second) by lacoupled plasma-mass spectrometry (LA ICP-MS). C, Bulk sample element concentrations determined by inductively coupled plasma-mass specelevated (millimeter-scale) element concentrations include Au, Ag, Hg, Bi, Fe, As, S, Sn, Cu, Pb, Zn, and other elements, only some of which are 

1 cm

Paramount Mine vein (PMT06-3)

Counts/second Counts/second Counts/second

102 104 106 103 105 103 105

A B

Line of traverse

107Ag

75As 208Pb

118Sn

34S

63Cu

202 23Na Hg

205Ti

197Au

209Bi

57Fe

27Al

31P

66Zn

12C

39K

36Cl
1 cm

Atastra Creek sinter (ATAS06-1)

Section A

Line of traverse

Section A (expand

cps

cps

Counts/second Counts/second Counts/second Counts/second

102 104 106 102 104 106 102 104 106 103 105 107 Counts/second

102 104 10

75As

121Sb 90Zr

12C

238U

232Th

88Sr

137Ba

107Ag

107Ag

197Au

197Au

208Pb

75As

121Sb

75As

63Cu

205Ti

202Hg

118Sn

27Al

27Al

31P

34S

202Hg

57Fe

66Zn

208Bi

A B
Paramount-Bald Peak Alteration Zone 69

Figure 33. (Facing page) A, Image showing oriented consecutive sections of sinter with black beds from 

the sinter terrace on Atastra Creek, Paramount-Bald Peak alteration zone (fig. 27). B, Graphs showing relative 

element concentrations in sinter measured in counts per second (counts/second) by laser ablation inductively 

coupled plasma-mass spectrometry (LA ICP-MS). C, Bulk sample concentrations determined by inductively 

coupled plasma-mass spectrometry (ICP-MS). Sinter section A is expanded at right to show (millimeterscale) elevated concentrations of Au, Ag, Hg, Sb, and As. These elements and other elements that are locally 

concentrated (including Sn, Tl, Cu, Pb, Zn, and Fe) are mostly not elevated in the bulk sample.

The Bald Peak adit prospect lies about 1.2 km northwest 

of Bald Peak and encompasses a discontinuously exposed, 

north-northeast-trending zone of quartz-chalcedony veins and 

stockworks as much as 700 m long by 250 m wide (fig. 27; 

L.J. Peters, written commun., 2004). Veins and silicified breccia zones are within porphyritic trachyandesite of Del Monte 

lava flows. The Bald Peak adit is near the south end of the 

prospect, where a cliff-forming silicified fault zone contains 

an ~2-m-wide, massive to banded, locally brecciated, milky 

white quartz vein. The vein strikes ~N15°E, dips 80°SE–

80°NW, and splits into several thinner veins that pinch out at 

the south end of the cliff face. Several other zones of narrow 

(centimeters wide) north-northeast-striking, steeply dipping, 

chalcedonic quartz-pyrite veins are exposed near the south 

end of the prospect. Wall rocks of these veins are altered to 

montmorillonite ± kaolinite. Quartz veins exposed in bulldozer 

cuts in the northern part of the prospect consist of brecciated, 

iron oxide stained, white chalcedonic quartz as much as 0.3 m 

wide. Some veins are banded with vuggy centers and bladed 

textures that suggest quartz replacement of carbonate minerals. Vein samples from the Bald Peak adit prospect contain 

as much as 5.4 ppm Au, 12.3 ppm Ag, 1,900 ppm As, and 

6.6 ppm Hg (L.J. Peters, written commun., 2004).

Sulfur Isotope Compositions

Two samples of cinnabar from the Paramount Mine 

have similar δ34S values of −5.3 and −4.7 ‰ (PM08-1A; 

PM08-1B; table 2). These values are slightly higher than some 

δ34S values of sulfide minerals in the Aurora Mining District, 

and slightly lower than values of cinnabar in the Cinnabar 

Canyon-US 395 alteration zone, and most values of sulfide 

minerals in Bodie district veins. Paramount Mine cinnabar 

δ34S values may reflect sulfide-sulfate fractionation. However, 

the presence of sulfate minerals is unsubstantiated; additional 

sulfur isotope analyses are required to adequately characterize 

sulfur geochemistry of this very large alteration zone.

ASTER Imagery

ASTER imagery (Rockwell, 2010) of the PBP AZ 

shows widely scattered pixels and five fairly contiguous pixel 

clusters that correspond to groups of hydrothermal minerals. 

Pixel clusters that coincide with northeast-elongate, silicified 

outcrops along upper Rough Creek about 2.5–3 km southeast 

of the Paramount Mine contain abundant alunite and kaolinite. 

The largest contiguous cluster of pixels (~ 0.35 by 0.2 km) on 

the west side of Atastra Creek west of the sinter terrace corresponds to leached tuff containing abundant smectite and (or) 

kaolinite and quartz. Other pixel clusters near the confluence 

of Atastra and Rough Creeks, and on the west side of Rough 

Creek, correspond to leached tuff that contains quartz, smectite, and kaolinite, and to kaolinite and alunite, respectively. 

However, no alunite was identified by PIMA spectroscopy in 

samples collected from several of these clusters.

SWIR Spectra

SWIR spectra of ~50 hydrothermally altered and mineralized hand samples from the PBP AZ show that montmorillonite and kaolinite are the dominant clay minerals, and that 

mixed-layer illite/smectite is less common. Kaolinite is most 

abundant near sinter outcrops. Alunite, illite, and chlorite were 

not identified in the analyzed hand samples.

Hydrothermal Mineral Ages

No hydrothermal minerals in the PBP AZ have been 

dated. However, based on 40Ar/39Ar ages of underlying and 

overlying rock units, sedimentary rocks and tuff of Paramount 

were hydrothermally altered between ~9.7 and 9.3 Ma. The 

pervasively altered sedimentary rocks contain abundant clasts 

of flow-banded, nearly aphyric rhyolite that may have been 

derived from the ~9.7 Ma Bald Peak lava dome (John and 

others, 2012). In most parts of the Paramount basin, altered 

sedimentary rocks and tuff of Paramount are overlain by 

unaltered ~9.4 Ma Eureka Valley Tuff. The lower part of the 

Eureka Valley Tuff near Atastra Creek is altered, but that 

alteration occurred after emplacement of the older, >9.7 Ma 

Tollhouse Flat member (Pluhar and others, 2009) of the 

Eureka Valley Tuff. In Atastra Creek and in other parts of the 

southwestern Paramount basin, unaltered lava flows of ~9.0 to 

8.8 Ma trachydacite of Potato Peak overlie altered Paramount 

basin rocks.
70 Gold-Silver Mining Districts, Alteration Zones, and Paleolandforms in the Miocene Bodie Hills Volcanic Field

Cinnabar Canyon-US 395 

Alteration Zone

Location

Secs. 2, 3, 4, 9, 10, 11, 13, 14, 15, 16, 23, 24, 25, 26, 36, T. 4 

N., R. 25 E. (unsurveyed); secs. 19, 29, 30, 31, T. 4 N., R. 26 

E. (unsurveyed), Mono County, California (fig. 1)

Definition

The Cinnabar Canyon-US 395 alteration zone 

(CC-395 AZ) is defined by a contiguous volume of rock, 

mostly volcaniclastic deposits and lesser porphyritic volcanic 

rocks, which have been pervasively hydrothermally altered to 

quartz, chalcedony, opaline silica, clay minerals, alunite, and 

pyrite. Altered rocks extend north and west from the mouth of 

Cinnabar Canyon to highway US 395, and are partly covered 

by unaltered trachyandesite of Willow Springs (fig. 34). The 

alteration zone may be several times larger (approaching 

30 km2) than exposed. Along and south of Clearwater Creek, 

alteration intensity decreases abruptly at the contacts of 

altered rocks and Paleozoic metasedimentary rocks and at 

contacts of younger rhyolite domes. Much of the alteration 

zone in secs. 23, 24, 25, T. 4 N., R. 25 E., including the sulfur 

resource, is covered by colluvium.

History and Production

Production recorded from the CC-395 AZ consists of 

10 flasks of mercury recovered in 1923 at the Calmono (Old 

Timer) Mine (Holmes, 1965), 0.3 km south of Cinnabar Hill 

(sec. 19, T. 4 N., R. 26 E.; sec. 24, T. 4 N., R. 25 E.; fig. 34). 

A nearby drill-defined sulfur resource, known as the Cinnabar 

Canyon sulfur deposit, contains 16.1 Mt at 17.9 weight percent 

S° (sec. 19, T. 4 N., R. 26 E.; sec. 24, T. 4 N., R. 25 E.; Ward, 

1992; Vikre and Henry, 2011).

Stratigraphy

The oldest rocks in the CC-395 AZ, exposed at the 

mouth of Cinnabar Canyon, are Paleozoic metasedimentary 

rocks (Chesterman and Gray 1975; fig. 34). In the vicinity 

of Cinnabar Canyon, Paleozoic metasedimentary rocks are 

unconformably overlain by a sequence of altered volcaniclastic deposits and largely coextensive porphyritic lava 

flows (volcaniclastic-flow sequence) in low-relief, domelike 

landforms. This sequence, which comprises most of the 

CC-295 AZ, was included in the Willow Springs Formation 

of Chesterman and Gray (1975), but has been correlated 

with sedimentary rocks and debris flows of Mount Biedeman (~9.9–8.9 Ma; table 1). Unaltered and variably altered 

flows that unconformably overlie altered sequence strata are 

included in trachyandesite of Willow Springs and dacite of 

Hot Springs Canyon, respectively (fig. 34; John and others, 

2012). In the CC-395 AZ, altered sequence strata, trachyandesite, and dacite have been intruded and partly covered by 

rhyolite of Big Alkali (John and others, 2012), which includes 

rhyolites in the Mount Biedeman and Willow Springs Formations of Chesterman and Gray (1975). Within the CC-395 AZ, 

trachyandesite of Willow Springs is ~8.6–8.0 Ma, and dacite 

of Hot Springs Canyon is ~8.1 Ma. Rhyolite of Big Alkali, 

north of Cinnabar Hill, is ~5.5 Ma (fig. 34; table 1).

The Paleozoic metasedimentary rocks are dark-gray to 

black, hornfels and quartzite (Chesterman and Gray, 1975). 

These Ordovician and Silurian strata are likely correlative with 

similar rocks exposed in the Log Cabin Mine and Ritter Range 

roof pendants in the Sierra Nevada (Kistler, 1966; Chesterman 

and Gray, 1975). Sedimentary rocks and debris flows of 

Mount Biedeman consist of poorly sorted lahar, block-and-ash 

flow, and associated sedimentary deposits shed from the flanks 

of the Mount Biedeman stratovolcano ~8 km east-southeast of 

the CC-395 AZ. To the south, these strata are intercalated with 

trachyandesite of Mount Biedeman lava flows. Clast populations in sedimentary rocks and debris flows are dominated by 

trachyandesite of Mount Biedeman. Most block-and-ash flow 

deposits are brownish-black, clast supported, and include an 

ashy matrix. Light-gray, recessively weathering lahar deposits 

are massive, poorly sorted, and contain silt- to boulder-size 

clasts in an ash- to clay-rich matrix. The sedimentary facies 

of this unit consists of matrix-supported deposits that contain 

rounded, compositionally diverse clasts several centimeters to 

0.5 m in diameter.

In the CC-395 AZ, volcaniclastic deposits of the 

volcaniclastic-flow sequence have been pervasively altered 

and weather recessively except where silicified. Exposures on 

the hill marked by conspicuous cuts in clay-altered volcaniclastic deposits (clay-cut hill; fig. 34), and in drainages 1 km west 

of Cinnabar Canyon and ~ 0.2 km north of Clearwater Creek, 

consist of chaotic to well-sorted, subrounded to subangular, 

centimeter- to millimeter-sized clasts of porphyritic volcanic 

rocks in soft gray-green to beige matrices composed of sand 

to ash-sized particles (figs. 34, 35). Conformable porphyritic 

flows occur mostly near the top of the sequence as blocky to 

locally tiered outcrops. Flows contain variable abundances of 

partly altered to relict phenocrysts of plagioclase, hornblende, 

and biotite in a green-gray to beige aphanitic matrix.

Based on the abundance of altered colluvial clasts, 

deflated surfaces in sec. 24, T. 4 N., R. 25 E., and stratigraphic 

sections (Ward, 1992), surficial deposits that cover altered 

volcaniclastic rocks in areas of low relief in the CC-395 AZ 

are likely meters to a few tens of meters thick.

Structure

The distribution of exposed altered rocks indicates that 

the CC-395 AZ is elongate northwest-southeast. However, 

alteration was strongly controlled by lateral permeability in the 

volcaniclastic-flow sequence, much of the alteration zone is 

partly covered by unaltered trachyandesite of Willow Springs, 

and the overall extent of the alteration zone may be more 
Cinnabar Canyon-US 395 Alteration Zone 71

equidimensional. Faults that may have served as conduits 

for hydrothermal fluid circulation in sequence strata are not 

widely evident. Northwest-striking faults that bound the sulfur 

resource near Cinnabar Hill presumably have controlled 

alteration of sequence strata that contain the resource (Ward, 

1992). Normal displacement along the northern fault, which 

corresponds to a northwest-trending linear escarpment of 

silicified sequence strata, is interpreted to have down-dropped 

sequence strata to the south. This fault apparently served as a 

conduit for hydrothermal solutions; displacement along it confined all sulfur to the footwall block. Lineaments on color air 

photos suggest that this fault extends to highway US 395. Two 

west-east-trending structures may slightly displace altered and 

postalteration rocks near Cinnabar Canyon (fig. 34). Other 

predominantly north- and northwest-striking faults were 

mapped by Chesterman and Gray (1975) in the vicinity of the 

S° resource and north and northwest of the resource.

The west side of the alteration zone is bordered by 

surficial deposits of Bridgeport Valley. These basin-fill 

deposits unconformably overlie altered sequence strata and are 

juxtaposed against them along a northwest-striking fault that is 

subparallel to US 395 (fig. 34).

Forms of Mercury and Sulfur Mineralization

The Calmono (Old Timer) Hg Mine, in the drainage at 

the south base of Cinnabar Hill (fig. 34), consists of shallow 

pits, cuts, a caved shaft, and remnants of a retorting (recovery) 

facility. Based on examination of dump samples, cinnabar 

occurs in thin veins and coats fractures in clay-altered porphyritic flows, and was likely the source of Hg production.

The Cinnabar Canyon sulfur resource, located immediately northwest of Cinnabar Hill, is ~60–135 m below 

the surface (figs. 34, 36). Its lateral dimensions are ~545 m 

northwest to southeast, and ~275 m southwest to northeast. 

The resource was identified in core and reverse circulation 

holes drilled for gold by Homestake Mining Company and 

Amselco Minerals Inc. in the late 1980s. The resource occurs 

in volcaniclastic-flow sequence strata that are altered to 

stratiform, subhorizontal assemblages of silica, clay minerals, pyrite, sulfur, and minor amounts of gypsum, barite, 

and cinnabar.

The following description of the sulfur resource is 

condensed from Ward (1992) and supplemented by observations derived from mapping and examination of discarded 

pieces of core at drill sites (Vikre and Henry, 2011). Several 

tens to >100 m of sequence strata are replaced by fine-grained 

quartz over the sulfur resource (fig. 36). These resistant rocks 

crop out on and northwest of Cinnabar Hill but rarely contain 

sulfur. Below and lateral to the stratiform silicification, 

sequence strata are partially to entirely replaced by clay minerals and opaline silica. Beneath opaline silica-clay alteration is 

a section of sequence strata ~35–60 m thick that is replaced by 

fine-grained quartz, 0 to >20 volume percent pyrite, and 0 to 

>20 weight percent sulfur. Based on IR and XRD analyses, 

and on petrographic examination of discarded drill core, these 

altered strata also contain small amounts of anatase, gypsum, 

barite, and cinnabar. The paragenetically late gypsum, barite, 

and cinnabar encrust fractures and voids that represent leached 

rock fragments and phenocryst sites in sequence strata. 

Sulfur-mineralized sequence strata grade downward into 

“weakly argillized” sequence strata that contain significant 

sulfur in several drill holes. Sulfur occurs in several forms 

(1) replacements of plagioclase phenocrysts and matrices of 

lava flows and volcaniclastic deposits, with variable amounts 

of quartz and pyrite, and (2) open-space filling of fractures 

and breccia matrices. Sulfur grades are highest in the upper 

and lower parts of the resource, possibly reflecting lithologic 

control (contrasting fluid permeability). The resource is 

confined on the northeast and south by faults. To the southwest 

and northwest, decreasing sulfur/pyrite defines a gradational 

limit to the resource.

Hydrothermal Alteration

Adjacent to and distal from the sulfur resource, volcaniclastic deposits of the volcaniclastic-flow sequence have been 

pervasively altered to quartz, chalcedony, opaline silica, clay 

minerals, alunite, pyrite (iron oxides), and small amounts of 

sulfur (figs. 34, 35). Interbedded porphyritic flows are variably 

altered; thin flows are pervasively altered and thick flows 

are less altered. This lithologic control of fluid circulation is 

evident in numerous places including the area immediately 

south of the Calmono Hg Mine, and on the south side of the 

clay-cut hill where altered volcaniclastic deposits and lesser 

porphyritic flow rocks have been excavated for clay minerals 

(fig. 34). The predominant mineral in white-colored excavations on the clay-cut hill is montmorillonite, as determined 

by XRD. 

Volcaniclastic deposits on the upper part of Cinnabar 

Hill are white to beige where they are completely replaced by 

fine-grained quartz with local iron oxide minerals on fractures; 

millimeter to centimeter-wide voids from leached clasts and 

phenocrysts are common in these resistant exposures. At 

lower elevations on Cinnabar Hill and throughout most of the 

CC-395 AZ, volcaniclastic deposits are gray-green and beige 

to yellow-brown to red-brown, depending on proportions of 

clay minerals (montmorillonite, kaolinite), iron oxide minerals 

(limonite, hematite, jarosite), and alunite (fig. 35). On the east 

side of Cinnabar Canyon, east and south of Cinnabar Hill, 

volcaniclastic deposits locally form resistant knobs of opaline 

silica that also contain clay minerals and alunite.

Breccias and veins crop out at several locations 

northwest and west of Cinnabar Hill. Brecciated porphyritic 

volcanic rocks within the volcaniclastic-flow sequence 

(NW1⁄4NE1⁄4NW1⁄4 sec. 24, and SE1⁄4SW1⁄4/SW1⁄4 sec. 13, 

T. 4 N., R. 25 E.) consist of subrounded, centimeter-sized 

clasts of partly leached vuggy silica in a white matrix of 

fine-grained to microcrystalline quartz, alunite, and kaolinite 
CALMONO Hg MINE Cinnabar Hill So float alunite float Cinnabar Canyon S° resource (fig. 36) clay-cut hill Qc Qc Ths Ths Tsmb Tsmb Tdcc Tsmb Tsmb Tsmb Tsmb Qc Qc Qc Qc Tsmb Tsmb Tsmb Ths Ths Twt Twa Twa Twa Twa Twa Tsmb Tbar

Tbar

Tbar

Tdcc

Tdcc

Tamb

Tbar

line of sectionfig. 36

A

A'

CC09-21

CC09-22

CC09-20

♦ CC09-6 CC09-7

CC09-5

CC09-4

CC09-1

39509-6

39509-7

39509-4

39509-6

39509-8

39509-9

39509-1

39509-2

39509-11

39509-30

CC09-3

CC09-8

Clearwater Creek

Cinnabar 

Canyon 

US 395

US 395

0-15

light-gray opaline silica

35

35

15

40

15-20

75-v

v±10

45

40

10

10-20

40

45

0-20?

Bridgeport Valley

0 0.5

0 0.5

1 MILE

1 KILOMETER

Bridgeport Valley

↓

Cinnabar 

↓ Canyon

 US 395

hydrothermal  alteration

NW SE SCHEMATIC SECTION

Tsmb

Twa

Ths

ms

ms

077-7A8.002 ± 0.04 Ma biotite8.053 ± 0.02 Ma plagioclase

39509-3K8.169 ± 0.013 Ma alunite

39509-108.070 ± 0.017 Ma plagioclase

077-7B8.124 ± 0.03 Ma b8.094 ± 0.03 Ma plagioclase8.073 ± 0.02 Ma hornblende

077-7C5.48 ± 0.02 Maplagioclase

CC09-9D28.68 ± 0.02 Ma alunite

CC09-9D18.82 ± 0.29 Ma alunite

08-BA-518.305 ± 0.017 Maplagioclase

~8.2 Ma alunite

↓

↓~8.0 Ma biotite; plagioclase

~8.0 Ma biotite; plagioclase

↓

~8.1 Ma biotite; plagioclase; hornblende

↓

~8.7; 8.8 Ma alunite

Base modified from U.S. Geological SurveyBig Alkali, Calif., 1989, 1:24,000

N

119°15' 1

38°25'38°15'38°05'

Mono 

Bridgeport

East

Walker

River

Masonic

B

Area of map
Cinnabar Canyon-US 395 Alteration Zone 73

35

40

EXPLANATION

Colluvium

Rhyolite of Big Alkali

Dacite of Hot Springs Canyon

Trachyandesite of Willow Springs (dacite of Chesterman and 

Gray, 1975)

Trachydacite of Cinnabar Canyon

Trachyandesite of Mount Biedeman

Sedimentary rocks and debris flows of Mount 

Biedeman—Includes volcaniclastic deposits, pyroclastic 

deposits, and porphyritic andesite (Twt and Twd of 

Chesterman and Gray, 1975); pervasively altered to quartz, 

opaline silica (red polygons), clay minerals, pyrite and 

alunite (line-pattern)

Qc

Tbar |ms

Ths

Twa

Tdcc

Tamb

Tsmb

Paleozoic rocks

Paleozoic metasedimentary rocks—Hornfels and 

quartzite (unit SOa of Chesterman and Gray, 1975)

Contact

Color air photo (CAP) lineament

Bedding

Foliation

Horizontal

Mine shaft

Analytic sample site and number

40Ar/39Ar sample site—Number, age, mineral

Figure 34. (Facing page) Geologic map and schematic stratigraphic section of the Cinnabar Canyon-US 395 alteration 

zone, Mono County, California, in part modified after Chesterman and Gray (1975) and John and others (2012).
74 Gold-Silver Mining Districts, Alteration Zones, and Paleolandforms in the Miocene Bodie Hills Volcanic Field

Figure 35. Images showing volcaniclastic deposits 

from the Cinnabar Canyon-US 395 alteration zone. 

A, Volcaniclastic deposits on clay-cut hill, Cinnabar 

Canyon, altered to montmorillonite, kaolinite, and 

lesser illite. B, Sorted and bedded volcaniclastic 

deposits in a drainage 1 km west of Cinnabar 

Canyon, 0.2 km north of Clearwater Creek, altered to 

montmorillonite and kaolinite; beds strike N-S, dip 

65°E; attitude of indistinctly bedded overlying debris 

flows 30 m (~100 ft) uphill is ~W-E, 0–20°S. C, Debris 

flows exposed in a layback along US 395, ~8 km 

(~5 mi) south of Bridgeport, California, altered mostly 

to alunite, kaolinite, and quartz; vertical face is ~4 m.

A

B

C
Cinnabar Canyon-US 395 Alteration Zone 75

NORTHWEST SOUTHEAST

Cinnabar Hill

?

?

EXPLANATION

A A'

7,600

7,500

7,400

7,300

7,200

7,100

7,000

6,900

6,800

7,600

7,500

7,400

7,300

7,200

7,100

7,000

6,900

6,800

Fig. 36

FEET FEET

Qc

Tsmb Tsmb

Tsmb

Colluvium

Sedimentary rocks and debris flows of Mount Biedeman

Alteration

Finely crystalline quartz

Bleached; clay-opaline

>10 volume percent pyrite

Finely crystalline quartz; >10 volume percent pyrite

Weakly argillized

>5 volume percent sulfur

Contact—Dashed where approximated

Fault—Dashed where approximated, queried where 

uncertain

Drill hole

Qc

Tsmb

Figure 36. Cross section (northwest-southeast) through the Cinnabar Canyon elemental sulfur resource (after Ward, 1992), 

Cinnabar Canyon-US 395 alteration zone, Mono County, California. Location of section is shown on figure 34.

in variable proportions. Narrow veins, millimeters wide, 

consist of the same minerals as the breccia matrix. Similar 

brecciated rocks within the volcaniclastic-flow sequence in the 

north-south drainage, about 2 km west-southwest of Cinnabar 

Hill, contain small amounts of sulfur in leached clasts.

Vegetation contrasts partially delineate the alteration 

zone. Pervasively and intensely altered volcaniclastic 

deposits support piñon pine but relatively little ground cover. 

Ponderosa pine trees near Cinnabar Hill grow in soils derived 

from opaline silica-clay-alunite-altered volcaniclastic strata, 

but are rare elsewhere in the Bodie Hills except in the Red 

Wash-East Walker River alteration zone. Unaltered trachyandesite of Willow Springs that partially overlies the altered 

volcaniclastic-flow sequence is relatively densely covered by 

piñon pine.

Minor Elements in Rocks

Thirty-eight samples of altered rocks and core scraps 

from the sulfur resource drill sites (table 1-10) contain 

variably elevated concentrations of Hg (1–337 ppm), Ag 

(2–20 ppm), As (92–396 ppm), Bi (~11–216 ppm), Pb 

(~71–7,510 ppm), Sb (~14–231 ppm), and Te (1–8.7 ppm). A 

few samples contain elevated Co, Ni, and Sr concentrations. 

The highest Au concentration is 0.084 ppm; Au concentrations in most samples are at or below the ~0.005 ppm 

detection limit. Barium concentrations exceed 1,000 ppm in 

many samples; a number of samples contain several percent 

S, apparently reflecting the presence of barite, alunite and 

other sulfate minerals, and sulfur. Elevated As, Bi, Pb, and 

Sb concentrations also allow for the presence of metallic 

sulfide minerals.
76 Gold-Silver Mining Districts, Alteration Zones, and Paleolandforms in the Miocene Bodie Hills Volcanic Field

Sulfur Isotope Compositions

Sulfur isotope (δ34S) values of sulfur, cinnabar, and pyrite 

in altered sequence strata (encountered in drill holes) that 

contain the sulfur resource, vary from −5.2 to −4.7 ‰, −0.7 to 

−0.2 ‰, and −9.8 to −8.0 ‰, respectively (table 2; Vikre and 

Henry, 2011). The δ34S value of barite in drill core is 1.1 ‰. 

Alunite in an altered sequence sample from the drainage 

~2 km west of Cinnabar Hill has a δ34S value of 2.5 ‰. These 

sulfur isotope compositions are difficult to interpret because 

of paragenetic and age differences among analyzed minerals, 

and possible sample impurity. Disproportionation of magmatic 

SO2 most likely caused alteration of sequence strata, but the 

δ34S values allow variable parent sulfur isotope compositions 

and (or) equilibrium temperatures. Further, the ~0.65 m.y. 

spread of 40Ar/39Ar ages of alunite implies that several separate 

magmatic-hydrothermal events altered sequence strata. 

Interpretation of sulfur isotope chemistry requires additional, 

paragenetically controlled analyses of minerals throughout the 

CC-395 AZ.

ASTER Imagery

ASTER imagery (Rockwell, 2010) of the CC-395 AZ 

shows spatial associations of alunite, kaolinite, illite, montmorillonite, and quartz. The distribution of these minerals is 

discontinuous because of spectral resolution, colluvium, trees, 

and unaltered trachyandesite of Willow Springs that cover 

altered sequence strata. Surficial deposits in low relief parts of 

the alteration zone overlie clay-alunite-altered sequence rocks; 

spectral reflectance of altered colluvial clasts mimics that of 

altered sequence rocks.

Alteration mineral abundances and associations are 

variable within the CC-395 AZ. Breccias and sequence 

strata that underlie Cinnabar Hill and the low-relief hills 

south of the Calmono Hg Mine and east of Cinnabar Canyon 

contain alunite, kaolinite, montmorillonite, and lesser illite. 

Alteration minerals on the east slope of Cinnabar Hill and on 

hills underlain by porphyritic flows west of Cinnabar Hill are 

mostly kaolinite and montmorillonite. Alteration minerals in 

the drainage parallel to and ~2 km west of Cinnabar Canyon, 

on the south slope of the clay-cut hill, and in volcaniclastic 

strata south of this hill, are mostly kaolinite and montmorillonite with lesser illite and alunite. Cinnabar Hill, which 

consists of fine-grained quartz and chalcedony, and the sulfur 

resource to the northwest that is covered by surficial deposits, 

are coincident with spectral responses indicative of very sparse 

illite and montmorillonite. These variable alteration mineral 

associations, coupled with alunite ages and sulfur isotope 

analyses, are consistent with several alteration events in the 

CC-395 AZ.

SWIR Spectra

Based on SWIR analyses, hydrous minerals in hand 

samples of altered volcaniclastic strata and porphyritic 

flows in the CC-395 AZ include montmorillonite, illite, 

kaolinite, alunite, and opal, supporting field observations and 

ASTER imagery.

XRD Mineralogy

Two samples of core scraps from drill sites over the 

Cinnabar Canyon sulfur deposit consist of quartz, pyrite, 

sulfur, and trace amounts of anatase.

Hydrothermal Mineral Ages

The 40Ar/39Ar dates of alunite in the matrix of brecciated 

porphyritic rocks within the volcaniclastic-flow rock sequence 

~1 km northwest of the sulfur resource, and of alunite in 

veins cutting porphyritic rocks (NW1⁄4NE1⁄4NW1⁄4 sec. 24, and 

SE1⁄4SW1⁄4SW1⁄4 sec. 13, T. 4 N., R. 25 E.; fig. 34), are 

8.82 ± 0.29 Ma and 8.68 ± 0.02 Ma, respectively (fig. 34; 

table 1). Alunite that has partly replaced fragments in 

volcaniclastic strata in the US 395 layback ~8 km south of 

Bridgeport, California, is 8.17 ± 0.01 Ma (fig. 34; table 1). 

Although no sulfur isotope analyses are available, the 

alunite dates are consistent with stratigraphic ages (table 1), 

and the dated alunites are considered hypogene. The range in 

alunite dates indicates that sequence strata were altered two or 

more times. The alunite dates are broadly contemporaneous 

with magmatism represented by 8.6–8.0 Ma trachyandesite of 

Willow Springs (table 1).
Bodie Mining District 77

Bodie Mining District

Location

Secs. 9, 10, 16, 17, 20, 21, 28, 29, T. 4 N., R. 27 E., Mono 

County, California (fig. 1)

History and Production

The Bodie Mining District has a storied history because 

of very rich Au-Ag ore and a citizenry that often was indifferent to law. The district and town that provided services 

were named by companions of one of the discoverers, W.S. 

Bodey, who died in 1860, the year following discovery. A 

later intentional misspelling, Bodie, was permanently adopted 

for both.

Bodie history has been recounted by Browne (1865), 

Wasson (1878), Burchard (1881), Wedertz (1969), and Piatt 

(2003). Placer Au, discovered in 1859 in the shallow drainage 

east of the Red Cloud Mine dump, led to the location of 

Au-Ag veins shortly thereafter. In the early 1860s, veins on 

Standard Hill (earlier named Bunker Hill and High Peak 

Hill) and Bodie Bluff were mined seasonally because of 

inaccessibility during winter, summer, and fall water shortages, and perception that the Aurora Mining District was 

more prospective, even though Bodie veins were extolled by 

mining notables B. Silliman and W.P. Blake (Wasson, 1878). 

The small amounts of ore produced from these veins were 

initially hauled kilometers west for processing in perennial 

Rough Creek, and some ore was processed at Aurora. The 

Empire (stamp) mill, constructed in 1864 at the base of the 

north slope of Bodie Bluff, processed ore from veins that 

became the Syndicate Mine, and from the Bullion née Bunker 

Hill vein on Standard Hill, which in 1877 was renamed the 

Standard vein of the Standard Mine (figs. 37, 38). In that year, 

1,000 tons of Standard vein ore, processed at the Empire mill, 

averaged $45 per ton (~2.3 opt Au at the prevailing price of 

~$20/oz); a subsequent lot of 10,000 tons netted $428 per ton 

(~21.4 opt Au). Rapid development of the Standard and other 

veins ensued in late 1877, and the Standard mill was built. 

In 1878, the high-grade Fortuna, Burgess, and Bruce veins 

were discovered in the adjacent Bodie Mine. Some ores from 

these veins averaged $600 per ton (~30 opt Au) and electrum 

clogged stamps in the Empire mill. Over the next three 

years, large volumes of very rich ore were produced from the 

Standard vein, which became the largest source of ore in the 

district, and from veins in the Bodie Mine. In the early 1880s 

the population of Bodie was an estimated 8,000.

From 1877 to 1882, numerous additional mines were 

developed on veins on Bodie Bluff, Silver Hill, and Queen 

Bee Hill, and in lower ground between these hills. Despite 

locally high assays and higher expectations (for example, 

Burchard, 1881; 1882; 1884), little to no ore was found in 

most mines. Insufficient milling capacity or water shortages 

delayed ore processing, which led to owner impatience, 

investor pressure, and construction of numerous mills, most of 

which were idled within one year. Optimism, neighbor envy, 

stock manipulation, and assessments also empowered mining 

companies to excavate shafts and exploration crosscuts well 

below the water table, which was encountered at ~400–780 ft. 

The costs of water control and deep exploration turned most 

mining companies into assessment companies whose main 

legacies were multicompartment shafts, mammoth Comstock 

Lode-scale pumping and hoisting facilities, and fleeced 

investors. Small amounts of ore were recovered from the 

dewatered Fortuna vein on the 700, 800, and 1,000 levels of 

the Lent shaft (fig. 37), but most nonproductive mines had 

ceased operating by the end of 1884. The Lent and another 

deep water-control shaft, the Red Cloud (fig. 37), were 

deepened and dewatered several times during the 1880s, but 

little to no ore was found at depth. The virtual absence of ore 

~600 ft below the surface on Bodie Bluff and Standard Hill is 

attributed to relatively low Au-Ag grades, narrow vein widths, 

and the high cost of mining in water at depth.

In the 1890s, mining was revived when electricity 

replaced wood-fueled steam power, and gravity-Washoe pan 

processing was converted to cyanidation. Efficiencies and 

lower operating costs derived from these technologies enabled 

profitable reworking of tailings and dumps, and production 

from low-grade narrow veins (1–4 inches) above the 500 level 

of the Standard Mine until 1913, when narrow-vein ore was 

depleted. After closure of the Standard Mine, cyanidation 

of mine waste and leasing (Eakle and McLaughlin, 1919) 

resulted in episodic production through the 1930s, including 

a short-lived attempt by the Treadwell-Yukon Company, Ltd. 

in 1929–32, to mill dumps and dewatered sulfide veins in the 

connected Red Cloud-Noonday-Oro Mines. From 1936 to 

1942, the Roseklip Mining Company processed 346,000 tons 

of dumps from the Bulwer Tunnel (used to access the Standard 

Mine; fig. 37), Standard and Bodie Mine dumps, and tailings 

from Silver Hill mills. The company also mined ~55,000 tons 

of narrow veins from surface excavations in the vicinity of 

the Standard, Bodie, and Con Pacific shafts, and produced 

~21,170 oz Au and ~562,000 oz Ag (estimated from bullion 

value at gold=$35/oz, and silver=$0.70/oz; tables 6 and 7; 

Chesterman and others, 1986).

Based on bullion value and weight of Au and Ag 

produced from 1877 to 1882, ore grades in mines on Standard 

Hill and Bodie Bluff varied from ~1 to several opt Au, and 

contained several opt Ag. During this period, parts of veins 

that contained less than ~1 opt Au were often not mined. Gold 

grades in ore produced from mines near Silver Hill were in the 

same range, but Ag grades were tens or more opt. However, 

Silver Hill vein ore was seldom defined by Ag values, in part 

because some to most Ag was in sulfide minerals and not 

economically recoverable. Most ore mined after the mid-1890s 

was lower grade because electrification, cyanidation, and 

surface mining decreased extraction and processing costs, and 

because high-grade ore had been depleted.
78 Gold-Silver Mining Districts, Alteration Zones, and Paleolandforms in the Miocene Bodie Hills Volcanic Field

Rhyolite 

on dump

MONO FAULT

TIOGA FAULT

60

40

75

75 45

60

v

80-v

60

80

60

v

Booker 

vein?

BODIE CREEK FAULT

Maybelle

Red 

Cloud

Old 

Standard

Upper 

Hobart

Tunnel

Bulwer

Tunnel

Bodie

Tunnel

Tioga

Bechtel

Bechtel 

incline

New 

Standard

McClinton

Old

Belvidere

Con

Pacific

Lent

Mono

Syndicate

Jupiter

Bulwer

Milk Ranch Canyon

Cupon

Old 

Bodie?

Davis

Tunnel

water

tower

Harrington 

Tunnel

Security

Tunnel

New

Belvidere

Summit

S. 

Bulwer

Whitney

Tunnel

Addenda

Contention

STANDARD VEIN FAULT

A'

B'

B

A

2

8; 9; 11

10; 18

19

13; 14

12; 21 20

17

15 16

0 0.5

0 0.5

1 MILE

1 KILOMETER

Base modified from U.S. Geological Survey

Bodie, Calif., 1998, and Kirkwood Spring, 

Calif.-Nev. 1989, 1:24,000

Bodie

Bodie

Bodie

Creek

BODB06-4A

Silver Hill series veins

Incline series veins

Burgess series veins

Approximate projection

 of Fortuna vein, 460 level

7 site 

~250 m W

4 

(actual sample 

site is ~200 m 

south of symbol)

Standard 

Hill

Bodie 

Bluff

Silver 

Hill

Sinter; silicified 

volcaniclastic 

deposits

Mill tailings

Qc

Qc

Qc

Tev on dump

Tev on

dump

Tsdi

Tsdi

Tsd

Tpp

Tpp

Tev

Tdm

Tpp

Tpp

Tev

Tev

Tsd

Tsd

Tsd

Tsdi

Tsdi

Tsdi

Tsdi

Tsd

Tsd

Tsdbx

Tsdbx

Tsdbx

MOYLE 

FAULT

University

Maryland

Queen Bee Hill

Approximate projection

 of Silver Hill series veins

Boston 

Consolidated?

Spaulding

Noonday

Oro

Dudley

Defiance

Dudley Air

N

Fig. 37

EXPLANATION

35

40

Colluvium and tailings

Trachydacite of Potato Peak

Eureka Valley Tuff

Trachyandesite of Del Monte

Dacite of Silver Hill

Intrusions and intrusion breccias

Heterolithic volcaniclastic rocks 

of Bodie Bluff

Lava and debris flows

Contact

Fault—Dashed where 

approximated, dotted where 

concealed

High-angle normal fault—Bar and 

ball on downthrown block

Bedding

Foliation

Mine shaft

Adit

Veins

40Ar/39Ar sample site and index 

number (table 1)

Qc

Tpp

Tev

Tdm

Tsdi

Tsd

Tsdbx

119°15' 119° 118°45'

38°25'

38°15'

38°05'

CALIFORNIA

NEVADA

Mono Lake

Mono Valley

Bridgeport

Fletcher Valley

East

Walker

River

Masonic

Bodie

Aurora

Area of map
Bodie Mining District 79

Figure 37. (Facing page) Geologic map of the Bodie Mining District, 

Mono County, California, modified from Chesterman and others (1986), 

and John and others (2012). Cross section sections A–A’ and B–B’ 

shown in figure 38A,B, respectively.

Figure 38. Geologic cross sections of the Bodie Mining District. A, West-northwest to east-southeast cross section through the 

Standard Mine, modified from Chesterman and others (1986), Whiting (1888), Brown (1908), and Piatt (2003), showing distribution 

of Incline and Burgess series veins, and the Fortuna vein. Eureka Valley Tuff on the Bodie Mine dump (fig. 37) indicates that the 

stratigraphy on the west side of the section is incompletely represented. B, Approximately west-northwest to east-southeast cross 

section through the Red Cloud shaft, modified from sections in the Bodie Consolidated Mining Company Collection (2003; University of 

Nevada Reno, Special Collections), showing distribution of Silver Hill series veins. Mine workings, veins, and faults are approximately 

positioned because of inconsistencies among source sections. Section locations are shown in figure 37. Vertical and horizontal scales 

are equivalent. Proj., projected.

9,000

8,800

8,600

8,400

8,200

8,000

7,800

8,800

8,600

8,400

8,200

8,000

7,800

FEET

FEET

1200 level 

1000 level

700 level

500 level

385 level

Bulwer Tunnel

Moyle Fault

Standard

new shaft Standard

old shaft

Bodie 

Creek

200 level

Lent 707 level

Incline series veins

Standard vein

Beehive vein

Red vein fault

Burgess series veins

Standard Hill

212 level

512 level

312 level Concordia vein

Base vein

Noonday vein

Red Cloud vein

Oro shaft

Noonday (projected)

shaft (projected) Red Cloud

shaft

Silver Hill series veins

A

A A'

B B'

B

EXPLANATION

Standard Vein Fault

Tsdbx

Tsdi Tsdi

Tsd Tsd

Tsd

Qc

Qc

Tsbx

Tsd

Tsdi

Colluvium

Dacite of Silver Hill

Intrusions and intrusion breccias

Heterolithic volcaniclastic rocks of Bodie Bluff

Lava and debris flows

Contact—Dashed where approximated

Fault—Dashed where approximate. Arrows show relative movement. Triangle 

pattern between faults shows fault-breccia zone.

Veins

Mine workings
80 Gold-Silver Mining Districts, Alteration Zones, and Paleolandforms in the Miocene Bodie Hills Volcanic Field

Recorded production from 1859 to 1955 is 1.456 Moz 

Au, and 7.280 Moz Ag recovered from 1.5 Mt of ore (Long 

and others, 1998). Significant amounts of ore (>10,000 oz 

Au) were produced from the Standard, Bodie, Noonday, and 

Bulwer Mines. Smaller production (tens to several thousand 

ounces of Au, estimated from production values in Burchard, 

1881) came from the Bechtel, Red Cloud, Syndicate, 

Belvidere, Bodie Tunnel, and Oro Mines. The Tioga, Mono, 

and Lent Mines produced no or small amounts of ore despite 

extensive workings and large dumps. Primary functions of 

the Lent and Red Cloud Mines were to dewater and provide 

access to productive neighboring mines. Based on maps of 

underground workings (Chesterman and others, 1986), other 

sizeable mines on and near Silver Hill, including the Contention, Addenda, and Maybelle, accessed veins encountered in 

the Noonday and Oro Mines. No production has been verified 

for mines south of the Noonday Mine (fig. 37).

A resource of ~24.6 Mt @ 0.07 opt Au and 0.42 opt 

Ag was identified in the 1980s (Long and others, 1998) by 

drilling on Standard Hill and Bodie Bluff. A larger but lower 

grade resource estimate of 75 Mt @ 0.037 opt Au and 0.08 opt 

Ag is reported by Hollister and Silberman (1995a). This 

resource includes ~25 Mt @ 0.04–0.05 opt Au in oxidized 

rocks (Chesterman and others, 1986; Hollister and Silberman, 

1995a) that could be mined by open pit and processed by 

heap leaching. These resources consist of closely spaced 

narrow veins, vein stockworks, and breccias between and 

branching from larger veins that were mined from ~1877 to 

1942 (Hollister and Silberman, 1995a). In 1997, the mining 

claims that include the resources and nearly all old mines were 

added to the Bodie State Historic Park (Bodie Consolidated 

Mining Company Collection, 2003), which is managed by the 

California Department of Parks and Recreation.

Stratigraphy

Veins are nearly entirely within dacitic to andesitic 

intrusions, flows, debris flows, block-and-ash flows, and 

other volcaniclastic deposits (Silver Hill volcanic series of 

Chesterman and others, 1986; dacite of Silver Hill of John 

and others, 2012; other stratigraphic units are described by 

Gumble and others, 1991); these host rocks are collectively 

referred to hereinafter as dacite of Silver Hill. According to 

Brown (1908), wall-rock fragments internal to veins that were 

encountered during mining include a fine-grained, coal-black 

lithology. These fragments are likely Eureka Valley Tuff, 

which comprises some of the Bodie and Dudley Mine dumps 

on the south slope of Standard Hill and northeast of Silver 

Hill, respectively (fig. 37). The 9.5–9.3 Ma Eureka Valley 

Tuff (John and others, 2012) on these dumps is cut by quartzadularia veins and breccias that are ~8.9–8.1 Ma elsewhere in 

the district (table 1). Eureka Valley Tuff on Standard Hill and 

Bodie Bluff is entirely concealed by flows, debris flows, and 

talus adjacent to domes of dacite of Silver Hill that comprise 

these landforms.

Domical intrusions and associated debris flows of dacite 

of Silver Hill were emplaced over a short time interval, 

9.1–8.9 Ma (table 1). Bodie Bluff, Standard Hill, Queen Bee 

Hill (fig. 37), and Sugarloaf (Sugarloaf is ~ 0.1 km south of 

fig. 37) are cored by flow-banded dacite intrusions (dacite 

plugs of Chesterman and others, 1986); the most productive 

veins occur in these intrusions on Standard Hill and Bodie 

Bluff. Veins on Silver Hill, and other veins between Standard 

Hill, Queen Bee Hill, and Silver Hill, occur in biotitehornblende dacite flows, associated block-and-ash flows, and 

debris flows. Biotite-hornblende flows also are exposed on the 

south slopes of Bodie Bluff and Standard Hill, and south of 

Queen Bee Hill. In mine workings, endogenous flow-domes 

are reportedly as much as 700 ft thick (Chesterman and 

others, 1986).

The dacite of Silver Hill is medium-light-gray to 

light-brownish-gray, moderately porphyritic, and commonly 

massive but locally flow laminated. It contains 15–30 percent 

phenocrysts of plagioclase, hornblende, and biotite, and trace 

amounts of quartz and (or) sanidine in a moderately devitrified 

(rarely glassy) groundmass. Regionally, the dacite forms a 

series of lava domes that coalesce to a roughly circular area. 

Debris flows associated with the dacite of Silver Hill are lightgray to very pale-orange, recessive-weathering, poorly sorted, 

matrix-supported deposits that were shed during the lateral 

collapse of lava domes. Clast populations are dominated 

by dacite of Silver Hill blocks as much as several meters in 

diameter that commonly are prismatically jointed, but include 

clasts of older volcanic rocks of the Bodie Hills volcanic 

field, especially trachyandesite of Mount Biedeman. A weakly 

consolidated ash and clay-rich matrix is present in isolated 

outcrops, yielding residual surfaces strewn with large-boulder 

lag deposits.

Heterolithic volcaniclastic deposits on the top and south 

slope of Bodie Bluff are bounded to the west and east by 

northeast-trending, graben-forming faults, which both offset 

and contain mineralized veins. These deposits, as much as 

60 m thick, are composed of subangular, altered clasts of 

dacite, mostly centimeters in dimension, and other, uncorrelated volcanic rocks in a fine-grained matrix of comminuted 

rock fragments and ash (figs. 37, 38). On the summit of 

Bodie Bluff, the deposits include a dismembered sinter 

terrace and local sinter fragments. Adjacent to, between, 

and above veins, dacite intrusions, dacite flows, and volcaniclastic deposits have been altered to zoned associations of 

hydrothermal minerals.

Porphyritic lavas and block-and-ash flows of trachydacite 

of Potato Peak (9.1 to 8.8 Ma; John and others, 2012) overlie 

dacite of Silver Hill to the north and west of the district. 

Eureka Valley Tuff is exposed ~1 km northeast of Bodie Bluff 

and in Milk Ranch Canyon west of Bodie Bluff where it 

underlies dacite of Silver Hill and trachydacite of Potato Peak 

(fig. 37). Based on exposures of Eureka Valley Tuff in Milk 

Ranch Canyon, Eureka Valley Tuff in the Bodie and Dudley 

Mines is ~5–8 m thick.
Bodie Mining District 81

Structure

In the Bodie Mining District, flows and volcaniclastic 

strata of dacite of Silver Hill originated from, and were domed 

by, three or more dacite intrusions, creating a north-northeasttrending landform that extends from Bodie Bluff south to 

Sugarloaf (Wisser, 1960; Chesterman and others, 1986). 

Tensional fissures and fan-pattern sheeting created by flexure 

are thought to have localized veins (Whiting, 1888; Wisser, 

1960; Chesterman and others, 1986), at least on Bodie Bluff.

The landform is segmented by northeast-striking and 

west-northwest-striking fault sets (Whiting, 1888; McLaughlin, 1907; Brown, 1908; Chesterman and others, 1986; fig. 37). 

Two northeast-striking faults with opposing dips, the Moyle 

and Standard vein faults, define the graben on Bodie Bluff. 

The graben contains volcaniclastic deposits that cover much of 

the summit and south slope of Bodie Bluff. The normal Moyle 

Fault strikes N38°E, dips 60–70°SE, is 0.6 m wide according 

to Chesterman and others (1986), and had combined pre and 

postmineralization displacement of at least 60 m based on the 

thickness of volcaniclastic deposits in the graben. According 

to Brown (1908), the Moyle Fault is 10 – 40 ft wide and is 

represented on the surface by a northeast-striking, 3 – 4.5 m 

high scarp west of the Standard Mine shaft. The Standard Vein 

Fault strikes ~N10–20°E, dips 60–70°NW, and apparently 

had pre and postmineralization displacement similar to the 

Moyle Fault (Chesterman and others, 1986). These synmineral 

faults contain and displace mineralized veins; they also offset 

sinter in volcaniclastic deposits and veins in the subsurface 

from adjacent veins in dacite of Silver Hill (figs. 37, 38). 

Atop Bodie Bluff, volcaniclastic deposits include a small, 

dismembered sinter terrace, small pool sinters, and angular 

clasts of sinter (fig. 39G). These structural and stratigraphic 

relationships attest to at least two periods of vein and sinter 

deposition, and demonstrate that volcaniclastic deposits on 

Bodie Bluff accumulated during hydrothermal events.

The west-northwest-striking, near-vertical Tioga and 

Mono Faults, on and south of Bodie Bluff, respectively, are 

also marked by topographic depressions. Normal, downto-the-south displacement of as much as 150 m along the 

Tioga Fault occurred prior to mineralization (Chesterman and 

others, 1986). Along the Mono Fault, flows and volcaniclastic 

deposits of dacite of Silver Hill have been displaced 150 m 

right-laterally and down-to-the-south. The Mono Fault is 

~30 m wide and altered to montmorillonite near the Bodie 

State Park water tower (Chesterman and others, 1986). 

Distribution of altered rocks and absence of the Fortuna and 

other veins on Standard Hill and Bodie Bluff south of the 

Mono Fault, suggested to Chesterman and others (1986) that 

displacement on the Mono Fault predates mineralization. 

However, temporal relationships among vein types and 

associated wall-rock alteration, do not clearly constrain timing 

and magnitude of fault displacements. Other unnamed faults, 

including a northwest-striking, 60°E-dipping, premineralization fault that extends from Queen Bee Hill to the Spaulding 

Mine, offset stratigraphy of dacite of Silver Hill (Chesterman 

and others, 1986).

North-northeast-trending normal faults, one of which 

projects through the Bodie town site (Bodie Creek Fault, 

fig. 37), may offset trachydacite of Potato Peak and Eureka 

Valley Tuff from dacite of Silver Hill. Although the elevations 

of Eureka Valley Tuff in the Bodie and Dudley Mines, and of 

possible Eureka Valley Tuff fragments in veins (Brown, 1908), 

are unknown, Eureka Valley Tuff encountered underground 

is apparently above 8,200 ft, the lowest elevation of stoping 

in nearly all mines. Displacement of Eureka Valley Tuff in 

mines relative to Eureka Valley Tuff in Milk Ranch Canyon 

at 8,500–8,400 ft cannot be verified, but is probably not more 

than tens of meters.

Forms of Silver-Gold Deposits

All precious metal production was derived from 

veins, vein stockworks, and fault breccias that were mined 

underground prior to ~1936, and from small open cuts in the 

late 1930s and early 1940s. Different vein types were initially 

recognized by Whiting (1888), and further characterized by 

Brown (1908), Chesterman and others (1986), and Hollister 

and Silberman (1995b). Three vein types, distinguished by 

mineralogy, textures, Au/Ag, distribution, and to an extent, 

age, have been termed the Incline, Burgess, and Silver Hill 

series veins (figs. 37, 38). Brown (1908) classified a fourth 

vein type, based in part on attitudes and relative ages, that 

is represented by the Fortuna vein, although differences 

between Burgess series veins and the Fortuna vein, based on 

mine dump and archival specimens, are not straightforward. 

Incline series veins are prominently exposed on Bodie Bluff 

and Standard Hill, whereas Silver Hill series veins, which 

mostly occur south of the Mono Fault, rarely crop out. Some 

Incline and Burgess series veins are exposed in stopes, and 

in (1930s) open cuts on the south slope of Standard Hill. 

However, most Burgess veins and the Fortuna vein were 

encountered underground and do not crop out, or are covered 

by detritus and mine waste. Characteristics of these four vein 

types, synthesized from incomplete exposure, dump samples, 

archival specimens, adularia ages (table 1), and published 

descriptions, reveal marked to subtle differences among the 

vein types, summarized in table 4.

A small group of veins in the vicinity of Queen Bee Hill 

(fig. 37) was extensively developed, produced little to no 

ore, and appears to be entirely oxidized by weathering. The 

relationship, other than spatial, of these veins to other vein 

types is incompletely known, and published descriptions are 

limited; dump samples provide some vein characteristics that 

are briefly described. 

Based on textures of mineral assemblages, adularia 

dates, sulfur isotope compositions, and the absence of copper 

and other oxide minerals, the sulfide, selenide, telluride, and 

silicate minerals, and electrum, described below and imaged, 

are nearly entirely hypogene. Iron oxide minerals that marginally replace pyrite are interpreted to have formed during 

weathering, and mineral assemblages in veins that formed 

during weathering are not described.
82 Gold-Silver Mining Districts, Alteration Zones, and Paleolandforms in the Miocene Bodie Hills Volcanic Field

Fortuna vein, 

Mono Mine

Standard Mine

C. Fortuna Vein, Standard Mine D. Red Cloud Mine

E. Oro Mine, 520 level F. Addenda Mine, 560 level

G. Sinter clast in volcaniclastic 

deposits, Bodie Bluff 

A. Bodie Tunnel Dump B. Belvedere Mine 

5 cm

5 cm

2 cm 2 cm

4 cm

5 cm

3 cm

5 cm

5 cm

5 cm

Fig. 39
Bodie Mining District 83

Figure 39. (Facing page) Images of veins in the Bodie Mining District. A, Incline series veins, Bodie Tunnel dump, and 

Standard Mine (inset image; California State Mining and Mineral Museum collection specimen 660). B, Burgess series vein, 

Belvidere Mine (California State Mining and Mineral Museum collection specimen 7638). C, Fortuna vein, Standard Mine, 

528 level (Mackay-Stanford collection specimen OD 7604) and Mono Mine (inset image; California State Mining and Mineral 

Museum collection specimen 7045). D, Silver Hill series veins, Red Cloud Mine dump, east of Silver Hill. E, Silver Hill series 

vein (Oro vein), Oro Mine, 520 level (California State Mining and Mineral Museum collection specimen 5304). F, Silver Hill 

series vein (Oro vein), Addenda Mine, 560 level (California State Mining and Mineral Museum collection specimen 2009). 

G, Sinter fragments in volcaniclastic deposits, Bodie Bluff summit. Mine locations and veins shown on figures 37 and 38.

Table 4. Characteristics of Incline, Burgess, and Silver Hill series veins in the Bodie Mining District. Distribution of vein series is 

shown on figures 37 and 38.

[Ag, silver; Ag, gold; As, arsenic; Cu, copper; Fe, iron; S, sulfur; Sb, antimony; Se, selenium; Sn, tin; Te, tellurium; FeOx, iron oxides; wt, weight; v, vertical]

Vein 

series Distribution Attitude; width Au/Ag (wt) Textures and minerals Wall-rock alteration Age (Ma)

Incline Bodie Bluff; 

Standard Hill; 

Noonday Mine

Mostly N–N20±5°E,

v–40°W and E; 

mostly ≤1.2 m

≥0.4 Tens to hundreds of ≤1 mmthick, planar to slightly undulating layers of fine-grained 

quartz, lesser adularia, and 

less than 1 percent electrum, 

acanthite, and other sulfide 

minerals; minor paragenetically late calcite (mostly 

quartz perimorphs)

9,000–8,600 ft: centimeters-thick selvages of 

quartz, K-feldspar, illite, 

minor pyrite (FeOx); 

distal illite, chlorite, 

montmorillonite, calcite

~8.3–8.1

Burgess South slope of 

Standard Hill 

and Bodie Bluff 

below 8,700 ft 

elevation and 

north of Mono 

Fault

N25°E, v–70°E;

 ~4–0.1 m

>0.5(?) Pronounced to indistinct, 

several to tens of submillimeter to centimeter-thick 

layers of quartz, adularia 

(often quartz perimorphs), 

and lesser calcite (mostly 

quartz perimorphs), and as 

much as several percent electrum, sphalerite, galena, and 

Ag-Au-Cu-As-S-Se phases 

mostly in quartz layers; some 

layers consist of millimeter to 

centimeter euhedrons/subhedrons of quartz, adularia, and 

calcite (quartz perimorphs) 

8,700–8,400 ft: centimeters-thick selvages of 

K-feldspar, quartz, clinochlore, pyrite (FeOx); 

distal illite, chlorite, 

montmorillonite, calcite

8.5–8.4

Silver 

Hill

Vicinity of Silver 

Hill; north to 

Bodie Bluff 

below ~8,500 ft; 

south to Queen 

Bee Hill

Mostly N–N20°E, 

~50°E; 

<2 m

≤0.04 Fault breccia fragments 

replaced by quartz and 

minor sulfide minerals, and 

cemented by fine-grained 

to vuggy quartz, adularia, 

several to greater than 10 percent opaque minerals, clay 

minerals, barite, and calcite; 

opaque minerals include 

electrum, sphalerite, galena, 

pyrite, acanthite, tetrahedrite, 

chalcopyrite, bornite, hessite, 

and numerous Ag-Au-Sb-AsS-Te-Se and Cu-Fe-Sn-S-AgAs phases 

8,500–8,400 ft: metersthick selvages of quartz, 

illite, kaolinite, montmorillonite, pyrite

8.9–8.5
84 Gold-Silver Mining Districts, Alteration Zones, and Paleolandforms in the Miocene Bodie Hills Volcanic Field

Incline Series Veins

Incline series veins include the main Standard vein, the 

most productive vein in the district, and other productive veins 

in the Standard, Bodie, Bulwer, Bechtel, and Syndicate Mines 

on Standard Hill and Bodie Bluff (Whiting, 1888; Brown, 

1908; figs. 37, 38). Based on vein texture, Au/Ag, adularia 

dates, and mineralogy, some veins on the Noonday and Oro 

Mine dumps south of Silver Hill are similar to Incline series 

veins. However, Silver Hill series veins were also developed 

in the Noonday Mine, and variable Au/Ag (weight; table 5A) 

may reflect mining economics and different vein types. 

From 1877 to 1881, ore was produced from several tens of 

individual Incline series veins, or segments thereof. By 1908, 

more than 100 narrow and low-grade veins had been identified 

between wider, stoped veins (Brown, 1908); some of these 

veins were mined prior to closure of the Standard Mine in 

1913. On Standard Hill and Bodie Bluff, Incline series veins 

are distributed from the Moyle Fault, where they occur only in 

the hanging wall, to east of the Standard vein Fault, whereas 

spatially associated but older Burgess series veins are largely 

confined to the footwall of the Moyle Fault in Standard Hill 

according to Brown (1908; fig. 38). Incline series veins 

apparently accounted for most district Au and Ag production, 

although Burgess series veins were also highly productive. 

Ore produced simultaneously from both vein series in mines 

on Standard Hill was not recorded separately.

Incline series veins predominantly strike N20 ± 5°E, most 

are vertical or dip steeply east and southeast on the west side 

of Bodie Bluff and on Standard Hill, and most dip steeply to 

moderately (85– 40°) west and northwest on the east side of 

Bodie Bluff (figs. 37, 38; table 6). The Standard vein on the 

section in Chesterman and others (1986) dips ~20°W; other 

sources assign dips of ~ 40–80°W, and the vein as portrayed 

(fig. 38) may consist of closely spaced, more steeply dipping 

vein segments. In the early years of mining, these inwardly 

opposing dips engendered the concept of a central Veta Madre 

(Mother Vein; promoted by B. Silliman and W.P. Blake), the 

mythical large vein at depth from which narrower, nearersurface veins branch. A Veta Madre was never found but 

became a rationale for deep exploration.

The Standard vein and other high-grade Incline and 

Burgess series veins stoped in the Standard and adjacent 

mines extend for as much as 900 m along strike, but were 

mined no deeper than ~150 m below the surface (90 m in the 

Bodie Mine). Incline series veins that were mined during the 

most productive period, 1877–81, varied in width from <1 to 

27 m (McLaughlin, 1907; Brown, 1908; figs. 37, 38; table 5). 

Multiple closely spaced veins, and brecciated and mineralized 

wall rock on both sides of some veins, or segments thereof, 

often enabled mining (Whiting, 1888). Two or more parallel 

to subparallel veins as much as 1 m wide and separated by 

centimeter- to meter-thick wall-rock septa are commonly 

exposed in shaft collars and stopes. “Enrichers” or small veins 

that crossed thicker veins or branched into the footwall and 

contained high-grade Au, also enhanced minability; however, 

enrichers generally followed larger veins, were not spatially 

associated with intramineralization faults, and may represent a 

younger vein series. Based on surface stopes and mine dumps, 

Incline series veins in dacite of Silver Hill on Bodie Bluff 

and Standard Hill are competent with sharp, planar, and often 

unsheared wall-rock contacts. Mining of these veins required 

little timbering, except where veins and vein sets exceeded 

several meters in width (for example, the Standard vein).

South of the Standard Mine, Incline series veins were 

stoped in the Bodie Mine, but farther south on Standard Hill, 

and at depths below ~150 meters, veins narrowed to unmineable low-grade or unmineralized fissures and seams. Productive Incline series veins also declined in width and grade north 

and northeast of the Standard Mine where they were stoped in 

the Bechtel, Upper Hobart, Syndicate, and other mines near 

the summit and on the north and northwest slopes of Bodie 

Bluff (fig. 37). Combined production of these mines was small 

(several tens of thousands of ounces of Au).

Many Incline series veins on Bodie Bluff and Standard 

Hill were covered by colluvium. Other veins represented by 

thin seams at the surface were identified first by subsurface 

mining. Upward stoping of Incline series veins terminated 

at the contact of dacite and volcaniclastic deposits because 

relatively wide veins in dacite below the contact branched into 

unmineable, thin veins and seams in volcaniclastic deposits, 

or could not be followed into volcaniclastic deposits (Whiting, 

1888; fig. 38). The stratigraphic control of hydrothermal 

mineral assemblages by physical properties of host rocks has 

been documented elsewhere in the Great Basin (for example, 

Vikre, 2007; Vikre and Henry, 2011). The restricted vertical 

interval of ore in Incline series veins, and smaller grain size of 

quartz in veins on the summit of Bodie Bluff relative to grain 

size of quartz in veins encountered in the Bodie and Bulwer 

Tunnels ~180 m deeper (fig. 38), are cited as evidence for 

vertical zonation of vein mineral assemblages (Silberman and 

Chesterman, 1991; Wisser, 1960; Gumble and others, 1991).

Incline series veins are composed predominantly of 

fine-grained quartz, variable amounts of adularia, and minor 

metallic minerals (mostly <1 volume percent) in planar to 

slightly undulating layers (millimeters wide) that parallel wallrock contacts (fig. 39A). Narrow veins (millimeters to a few 

centimeters wide) consist of several parallel and symmetrical 

layers, whereas wider veins consist of tens to >100 layers; the 

frequency of layers containing metallic minerals determined 

minability of veins. Central quartz layers in some veins 

enclose lenticular vugs lined with quartz pseudomorphs and 

perimorphs that replace or encrust bladed calcite. Less commonly, central layers (millimeters to centimeters thick) consist 

of relatively coarse-grained calcite that locally constitutes 

several to tens of volume percent of veins. These calcite layers 

are mostly, if not entirely, paragenetically later than quartz 

(± adularia ± sulfide mineral) layers.

Metallic minerals include electrum, acanthite, and other 

sulfide minerals; iron and manganese oxides in weathered 

veins mark sites of sulfide minerals and attest to former 

calcite. Anhedral electrum and sulfide minerals occur in 
Bodie Mining District 85

Table 5. Gold and silver production and precious metal grades for mines and veins 

in the Bodie Mining District from 1875 to 1942, and relative value of gold and silver in 

bullion from 1878 to 1881.

[Gold and silver production and precious metal grades converted, in part, from gold and silver bullion values using $20.67/oz gold (Au) and $1.29/oz silver (Ag) (average or single assay values from 

Addenda, Jupiter and Noonday Mines; Burchard, 1882; 1884; Whiting, 1888; Eakle and McLaughlin, 

1919; Chesterman and others,1986; University of Nevada Reno library special collections NC323). 

Some vein type assignments are based on mine location and dump/archival vein sample characteristics. 

Relative value of gold and silver in bullion, 1878–1881 is as reported in Burchard (1881) and King and 

others (1885). Au, gold; Ag, silver; e, estimated; oz, ounce]

Gold and silver production and precious metal grades from 1875 to 1942

Period/

year

Mine, vein Au Ag Au/Ag 

Incline series veins

1875–76 Syndicate Mine 1,788 oz 4,332 oz 0.41

1879 Noonday Mine, Keystone vein 543 oz 1,349 oz 0.40

1883 Syndicate Mine 4,143 oz 4,940 oz 0.84

1883 Standard main vein 49,100 oz 258,937 oz 0.45

1883 Standard main vein 1.65 oz/ton 3.14 oz/ton 0.53

1900 Standard Mine, above 500 level e20,160 oz e28,160 oz 0.72

1912 Standard Mine 5.43 oz/ton 0.35 oz/ton 15.5

Burgess series veins

1879 Bulwer Mine 737 oz 1,089 oz 0.68

1879 Bodie Mine 656 oz 1,269 0.52

1936–42 Roseklip cuts, tailings and dumps 21,171 oz 561,904 oz 0.04

Fortuna vein

1883 Bodie Mine, Fortuna vein 5,085 oz 109,800 oz 0.05

Silver Hill series veins

1881 Noonday Mine, Concordia vein 2.3 oz/ton 361 oz/ton 0.006

1881 Noonday Mine, Concordia vein 6 oz/ton 53 oz/ton 0.11

1881 Red Cloud Mine, Concordia vein 13.5 oz/ton 2,679 oz/ton 0.005

1881 Red Cloud Mine, Red Cloud vein 1 oz/ton 32.3 oz/ton 0.03

1881 Addenda Mine 5.4 oz/ton 130 oz/ton 0.04

1881 Jupiter Mine 7.25 oz/ton 3,333 oz/ton 0.002

Relative value of gold and silver in bullion from 1878 to 1881

Year Mine, vein Au % Ag % Au/Ag 

Incline and Burgess series veins

1878 Standard main vein 92.3 7.5 12.3

1879 Standard 92 8 11.5

1880 Standard 93 7 13.3

1879 Syndicate 93 7 13.3

1880 Syndicate 93 7 13.3

Burgess series veins

1879 Bulwer 92 8 11.5

1880 Bulwer 93 7 13.3

1880 Belvidere 37? 63? 0.59?

Fortuna vein

1879 Bodie 85 15 5.7

1880 Bodie 59.5 41.5 [sic] 1.4

Silver Hill series veins

1879 Noonday 70 30 2.3

1880 North Noonday 41 59 0.6

Queen Bee Hill veins

1881 Boston Consolidated 75 25 3
86 Gold-Silver Mining Districts, Alteration Zones, and Paleolandforms in the Miocene Bodie Hills Volcanic Field

Table 6. Vein attitudes and widths derived from surface mapping and published descriptions.

[Burchard, 1881, 1882, 1884; Whiting, 1888; Brown, 1908; Wedertz, 1969; Chesterman and others, 1986; Piatt, 

2003). Some veins are shown on figures 37 and 38. ave., average; ft, feet; v, vertical; —, no data; <, less than]

Mine Vein Level Strike (°) Dip (°) Width (ft) 

Incline series veins

Standard Main vein Surface N20E±5 60W 4

200 — 78W 15–25

385 — 40W <90

— — — ave. 20

700 — — 8

North Standard — — — — 3.5–6

Bechtel — 440 — — 3–5

512 — steep W 3–12

Bodie Tunnel — — — — 6

Burgess series veins

Bodie Burgess; Bruce — N25E 75–85E; v —

Belvedere — 600 — — 14

Con Pacific — 400 — — 5

Bulwer Ralston; Stonewall 400 — — 2–4

South Bulwer — 550 — steep E–v. 6

Fortuna vein

Bodie Fortuna 300 N10–20W 20–30E 0.2–12

600 — 45E ave. 20

Silver Hill series veins

Jupiter — 500 — — 2

Goodshaw — 600 — — 4

Red Cloud Red Cloud; Packard 

&Morton

— N20E steep E —

400 — — 2–10

Concordia 600 — — 6

Noonday Keystone — N10–40E 80E 2–5

— — 500 — — 5–20

Addenda/Contention — 500 — — 7–8

Queen Bee Hill veins

Boston Consolidated — 200 — — 2–5

400 — — 2–4

University — 382 — — 2–22

Champion — 400 — — ave. 5

discrete crystals and in submillimeter aggregates that appear 

to be texturally coeval with quartz. In low-grade samples of 

multilayer veins, these crystals and aggregates form small 

dark specks that are sparsely distributed in one or a few 

layers of fine-grained white quartz. In samples with elevated 

Au and Ag grades, larger clots (millimeters to centimeters 

in size) and small dendrites of electrum and sulfide minerals 

accentuate quartz layers (fig. 39A, inset image). Metallic 

minerals identified and semiquantified by optical and scanning electron microscopy include electrum with subequal 

proportions of Au and Ag, Ag-Au-S-Se minerals (including 

possible uytenbogaardtite, Ag3

AuSSe2, and AuAgS (Barton 

and others, 1978; Barton, 1980), acanthite with minor Se, 

and chalcopyrite (fig. 40). A few bulk vein samples contain 

elevated concentrations of As and Sb (table 1-11), suggesting 

the local presence of Ag-As-Sb-S minerals. Vein minerals, 

including molybdenite and scheelite, previously identified 

on mine dumps on Bodie Bluff and Standard Hill (Hollister 

and Silberman, 1995a; 1995b), were not found during this 

investigation.

Gold/silver by weight and value in Incline (and Burgess) 

series veins are relatively high (≥0.40 and >11, respectively) 

compared to Silver Hill series veins and the Fortuna vein 

(mostly <0.1 and <6, respectively; table 5). The Au and Ag 

contents of veins correspond spatially to associated placer 

deposits in that high Au/Ag placers were mined on the slopes 

of Bodie Bluff and Standard Hill, whereas low Au/Ag placers 

were recovered from Silver Hill slopes (Whiting, 1888).
Bodie Mining District 87

quartz

200 μm

Ag6Au1.4Se0.7S2

adularia

adularia Au.46Ag.54

Au.48Ag.52

Au.48Ag.52

Ag5.5Au1.4Se0.6S2

Ag7.1Se0.6S3

C. Upper Hobart Tunnel dump D. Upper Hobart Tunnel dump

-

quartz

adularia

Au.47Ag.53

Ag2S

Ag2S

Ag2S

Ag2S

Au.47Ag.53

Au.45Ag.55

Fe oxide

Ag2.5Se0.2S

Ag2.7Se0.3S

Ag2Se0.2S

quartz

E. Noonday Mine F. Noonday Mine

~Ag2.6AuS2

~Ag2.2Au0.8S2

Ag2S

Au0.50Ag0.50

Au0.50Ag0.50

~Ag1.8AuS2

~Ag1.8AuS2

~Ag0.6Hg0.4; minor Se

~Ag0.8Hg0.5S

○●

~Au0.46Ag0.54 ○●

~Ag3.4Au1.2S2

○●

~AuAgS

~Au0.46Ag0.54 ●

adularia

A. Standard Mine B. Standard Mine

~Ag3.6AuS2

○●

~Ag ~Ag2.6 2.6AuS AuS22

~Ag3.6AuS2 ○●

~Ag2S; minor Se

~Ag2S; minor Se

quartz

500 μm

200 μm

Fig. 40

5 μm 20 μm

5 μm

Figure 40. Secondary and backscatter electron images of samples representative of Incline series veins on Bodie Bluff, and of vein 

samples from the Noonday Mine near Silver Hill, Bodie Mining District. Mineral identifications and approximate atomic proportions for 

these images, and for images in figures 41, 42, 43, 44, and 45, were determined petrographically and by scanning electron microscopy 

algorithms. A and B correspond to specimen CSMMM-660, Standard Mine (California State Mining and Mineral Museum collection; 

fig. 38). C and D correspond to sample 11-BA-26B, Upper Hobart Tunnel dump (fig. 37). E and F correspond to specimens 5074 and 

KM-952, respectively, Noonday Mine (Keck museum collection, University of Nevada, Reno; fig. 37). Imaged phases include quartz, 

adularia, acanthite (some with minor Se), electrum with subequal Au and Ag, Ag-Au-S minerals (~Ag3AuS2 , possibly uytenbogaardtite; 

~AuAgS; ~Ag2AuS2 ), Ag-S-Se minerals (~Ag7.1Se0.6S3 ; ~Ag2.5Se0.2S; ~Ag2.7Se0.3S), and Ag-Hg-S-Se minerals. Mine locations are shown 

on figure 37.
88 Gold-Silver Mining Districts, Alteration Zones, and Paleolandforms in the Miocene Bodie Hills Volcanic Field

Incline series veins are, in part, parallel to northeaststriking tabular breccias that offset the Fortuna vein and may 

constitute intrusive breccias or decomposed dikes (Whiting, 

1888; Brown, 1908; Gumble and others, 1991; for example, 

Red vein Fault, also known as “Red ledge”, or “Red vein” 

fig. 38). These high-angle, meter-wide, iron oxide-rich 

breccias, encountered in the Standard, Bodie, Bulwer, and 

other mines on Standard Hill and Bodie Bluff, may be coeval 

with overlying volcaniclastic deposits. Based on composition 

(Turner, 1908), the Red ledge/vein could be altered rhyolite 

in which K2O has been added (potassic alteration) and CaO 

and Na2O were reduced by hydrolysis of plagioclase. Spatial 

relationships among breccias encountered underground and 

potassically altered breccias that cut dacite, described by 

Silberman and Berger (1985), Silberman and Chesterman 

(1991), Gumble and others (1991), and Herrera and others 

(1993), are uncertain. These latter breccias consist of rock 

fragments partially replaced by K-feldspar, and matrices 

composed of quartz, adularia, and hematite. Matrices of other 

breccias at higher elevations consist of quartz, adularia, illite, 

calcite, and zeolites. Some of these breccias are parallel and 

adjacent to veins, and locally include mineralized quartzadularia vein clasts (Silberman and Berger, 1985; Silberman 

and Chesterman, 1991; Gumble and others, 1991; Herrera and 

others, 1993); however, paragenetic relationships among these 

breccias and specific vein series are also uncertain.

Burgess Series Veins

Burgess series veins, based on underground exposures, 

were originally thought to exist exclusively on the south and 

west slopes of Standard Hill west of the Moyle Fault (Brown, 

1908; Chesterman and others, 1986). However, samples of 

veins similar to Burgess series veins occur on mine dumps 

on the south slope of Bodie Bluff north of the Mono Fault, 

suggesting wider distribution (figs. 37, 38). Burgess series 

veins were stoped in the Standard, Bodie, Belvidere, Con 

Pacific, Bulwer, and other mines where they are cut by Incline 

series veins. Burgess series veins (individually named Bruce, 

Burgess, Incline, Gildea, Bullion, Ralston, and Cook) strike 

N25°E, dip steeply southeast or are vertical, and extend as 

much as 900 m along strike, although profitable segments 

had strike lengths of 180 m or less (Brown, 1908). They were 

stoped no deeper than ~180 m below the summit of Standard 

Hill (fig. 38). Burgess series veins exposed in the open cut on 

the south slope of Standard Hill are mostly centimeters wide, 

and many veins contained sufficient Au to be mineable at 

widths of ~2 cm. Gold in some veins occurred in “hard quartz” 

cohesive with wall rock, or in shaley clay-sand partings 

(Whiting, 1888; Brown, 1908), increasing ore widths as much 

as ~ 4.2 m (table 6).

Most Burgess series veins consist of relatively coarsegrained quartz and adularia (compared to Incline series vein 

minerals) in indistinct to pronounced layers that parallel 

wall-rock contacts and that may be defined by thin seams 

and septa (<1 mm) of micaceous minerals (fig. 39B). Some 

layers contain as much as several volume percent of relatively 

coarse-grained metallic minerals and “axial comb-textured” 

quartz layers (Brown, 1908; Chesterman and others, 1986). Vein 

interstices of dump samples on upper elevations of Standard 

Hill are commonly vuggy, and some are encrusted by quartz and 

(or) euhedral adularia crystals with dimensions of as much as 

several centimeters. These euhedral crystals further distinguish 

Burgess series veins from Incline and Silver Hill series veins.

Vein minerals identified and semiquantified optically and 

by SEM include quartz, adularia, an euhedral to subhedral 

Mg-Fe-Al-Si-O mineral (possibly clinochlore), Au-rich electrum, low Fe- and low-Cd sphalerite, and galena—all of which 

are intergrown in apparent textural equilibrium (fig. 41A, B, 

C ). Other metallic minerals, some in submicrometer mineral 

aggregates, include electrum with subequal proportions of 

Au and Ag, acanthite with minor Se and Zn, and mixed 

Ag-Au-S-Se and Au-S-Cu-As phases (fig. 41D, E, F ). A few 

bulk vein samples contain elevated abundances of As, Sb, and 

other elements (table 1-11), suggesting the local presence of 

Ag-As-Sb-S and other minerals.

The Fortuna vein, which was the source of most 

production from the Bodie Mine and likely the only source of 

production from the Mono Mine, is not exposed at the surface. 

In mine workings it is cut by numerous faults (described 

in previous section “Incline Series Veins”) and by Incline 

and Burgess series veins (fig. 38). The Fortuna vein strikes 

N10–20°W, dips 20–30°NE on the 300 level of the Bodie 

Mine, and ~45°NE on the 600 level (table 6). It varies in 

width from centimeters to ~6 m, as brecciated and mineralized 

wall rocks often enabled thin vein segments to be mined. It 

was stoped for as much as ~110 m along strike and ~300 m 

downdip, but below the 600 level it was mostly unmineable. 

On the 600 level of the Bodie Mine, the centimeter-wide, 

Ag-rich Beehive vein splits from the Fortuna vein (fig. 38). 

The Beehive vein was mined for ~ 45 vertical meters, and 

apparently is the deepest stoped vein in the northern part 

of the district. About 230 m below the surface, the Beehive 

vein narrowed to seams and thin veins of weakly mineralized 

quartz enclosed by wall rocks more decomposed than at higher 

levels (Brown, 1908).

To the southeast, the Fortuna vein was intersected on 

the 1000 level of the Standard Mine, and in the Lent (707 

and 1200 levels) and Dudley Mines (figs. 37, 38). Deep vein 

segments consisted of isolated bunches and narrow veins of 

quartz in sheeted zones of clay-altered, pyritic wall rocks 

(Brown, 1908). Although Au-Ag minerals and relatively 

abundant sphalerite were encountered locally, few of the deep 

segments contained sufficient Au and Ag to warrant mining. 

Wall rocks of the Fortuna vein are described as pyritic and 

“much decomposed” compared to wall rocks adjacent to 

Incline series veins (Brown, 1908).

Archival specimens of the Fortuna vein from the 

Standard and Mono Mines (fig. 39C ) include two texturally 

distinct zones. A 5-cm-wide zone in the Standard Mine 

specimen consists of wall-rock fragments (centimeters to 

millimeters in size) cemented by very fine-grained adularia, 
Bodie Mining District 89

ZnFe0.04S

Ag.17Au.83

Zn0.9Cd0.01Fe0.04S

Ag.17Au.83

Mg-Fe-Al-Si-O

Mg-Fe-Al-Si-O

quartz

A. Con Pacific Mine

200 μm

Mg-Fe-Al-Si-O Mg-Fe-Al-Si-O

Ag.15Au.85

quartz

Zn0.9Fe0.06S

Zn0.9Fe0.04S Mg-Fe-K-Al-Si-O

Pb0.9S

quartz

B. Con Pacific Mine 

500 μm

Ag.17Au.83

quartz

quartz

quartz

Zn0.9Fe0.01S

galena

galena

C. Con Pacific Mine 

600 μm

quartz

Ag1.2Zn0.2Se0.1S

Ag.48Au.52

Ag1.6Se0.1S

Ag-Au-S-Se

ZnFe0.01S

quartz

quartz

Ag.48Au.52

D. Belvidere Mine

200 μm

quartz

ZnFe0.01S

Ag1.6Se0.1S

Au-Ag-S-Se

Ag-S-Se

Au-S-Cu-As

Zn-Cd-S

Au-S-Cu-As

E. Belvidere Mine

50 μm

Au.72Ag.28

Au.73Ag.27

Au.72Ag.28

Au-Ag-O

F. Bodie Mine

50 μm

Fig. 41

Figure 41. Secondary electron images of samples representative of Burgess series veins on Standard Hill, Bodie Mining District. 

A, B, and C correspond to specimen 4260, Con Pacific Mine (Keck museum collection, University of Nevada, Reno). D and E correspond 

to sample BOD11-4A, Belvidere Mine dump. F corresponds to sample BOD11-13, Bodie Mine dump. Imaged phases include quartz, 

electrum with variable Au and Ag, sphalerite with minor Fe and Cd, a Mg-Fe-Al-Si-O mineral (possibly clinochlore), galena, a Ag-S-Se 

mineral (~Ag1.6Se0.1S), and a Ag-Au-S-Se mineral or mineral intergrowth. Mine locations are shown on figure 37.
90 Gold-Silver Mining Districts, Alteration Zones, and Paleolandforms in the Miocene Bodie Hills Volcanic Field

quartz, and minor pyrite. This zone sharply borders a complex 

zone of similar width (represented in both specimens) that 

consists of distinct layers of fine-grained quartz (millimeters 

to centimeters thick), euhedral quartz crystals, adularia, finely 

dispersed electrum and Ag sulfide minerals, and wavy layers 

of chalcedonic quartz (millimeters to centimeters wide). 

An irregular, centimeter-wide layer of brown and white 

chalcedonic quartz borders the zone of brecciated wall-rock 

fragments. In addition to the observed minerals, reported 

metallic minerals include magnetite, chalcopyrite, pyrargyrite, 

Ag, kerargyrite [sic], iron oxides, and copper oxides (Brown, 

1908), some of which were apparently produced by weathering. Argentite was described as occurring, in part, in thin films 

between apices of quartz crystals in druses.

Silver Hill Series Veins

Silver Hill series veins include veins on and near Silver 

Hill (fig. 37), only a few of which crop out. Maps and sections 

of underground workings (Chesterman and others, 1986; 

Bodie Consolidated Mining Company Collection, 2003) 

indicate that most Silver Hill series veins trend N–N20°E, and 

dip 50°E (fig. 38), although the near-vertical Booker (?) vein 

exposed in workings of the Spaulding Mine south of Silver 

Hill trends N15°W. Silver Hill series veins were extensively 

developed in the Noonday, Oro, Contention, Maybelle, 

Addenda, Dudley, and Red Cloud Mines. Small amounts 

of ore were recovered in the Oro, Addenda and Red Cloud 

Mines, but only the Noonday Mine had significant production. 

However, some Noonday Mine production apparently was 

derived from Incline series veins. Based on mine dumps, 

Silver Hill series veins may have been mined at the south 

base of Bodie Bluff several hundred meters north of the Mono 

Fault. If this interpretation is correct, then significant displacement along the Mono Fault apparently predates formation of 

Silver Hill series veins.

Compared to Incline and Burgess series veins, Silver 

Hill series veins are distinctly Ag-rich. Gold/silver by weight 

and value in Silver Hill veins are ≤ 0.04 and ≤3, respectively, 

although ratios are based mostly on ore grades and small 

production (table 5). Gold/silver and other characteristics 

(including adularia dates) of veins on the Noonday Mine dump 

suggest that ore mined in 1879 (Keystone vein) was derived 

from veins similar to Incline series veins, whereas ore mined 

in 1880–81 (Concordia vein) was derived from Silver Hill 

series veins (table 5). Alternatively, high Au/Ag in ore mined 

prior to 1880 and lower Au/Ag in ore mined 1–2 in later years 

may attest to ore selectively mined for high gold content, 

because mills were not designed to recover silver in sulfide 

minerals, or to possible supergene enrichment. 

Ore in Silver Hill series veins was mostly recovered from 

a >1-m-wide segment of the Concordia vein (fig. 38; table 4). 

Reported stope dimensions between the 450 and 700 levels are 

~120 meters along strike, and ~75 meters downdip (Chesterman, and others, 1986). Small amounts of ore were recovered 

from a 1.2-m-wide segment of the Red Cloud vein with 

reported stope dimensions between the 256 and 592 levels of 

~35 meters along strike and ~350 ft downdip (Chesterman, 

and others, 1986).

Vein textures and minerals in the Corcordia, Red Cloud, 

and Oro veins are described by Whiting (1888), Brown (1908), 

Chesterman and others (1986), and Hollister and Silberman 

(1995a). The Concordia vein consists of fragments of dacite 

cemented by fine-grained and vuggy white quartz, coarsegrained calcite, quartz pseudomorphs after calcite, clay gouge, 

tetrahedrite, pyrargyrite, and pyrite. The Red Cloud vein is 

mostly gouge and crushed quartz, but varies along strike from 

narrow, parallel, anastomosing veins to contiguous “ribbon” 

quartz and calcite a few centimeters to 1.2 m wide. On the 

700 ft level, the Red Cloud vein consists of quartz, quartz after 

calcite, coarse-grained calcite, and fine-grained adularia, tetrahedrite, pyrite, galena, pyrite, chalcopyrite, and minor amounts 

of sphalerite and pyrargyrite (fig. 39D). The Oro vein in the 

Oro and Addenda Mines consists of quartz, coarse-grained 

calcite, tetrahedrite, stephanite, pyrargyrite, pyrite, and galena, 

and minor barite (fig. 39E, F). Major oxides in bulk samples 

of Silver Hill series veins vary from 4.2 to 21.9 weight percent 

Al2O3, 1.2–11.3 weight percent K2O, 0.1–7.1 weight percent 

FeO, and <1 weight percent MgO, CaO, Na2O, and TiO2

(calculated from element concentrations, table 1-11).

Vein minerals identified and semiquantified by optical 

and SEM (fig. 42) include quartz, mica-clay minerals, 

adularia, and metallic minerals in aggregates of anhedral 

crystals. The mineralogy of the aggregates varies somewhat 

between mines and among samples from individual mines. 

Samples from the Oro Mine dump consist of quartz, adularia, 

minor amounts of barite, low Fe-sphalerite, galena, acanthite, 

Ag-Sb-As-S minerals, Cu-Fe-S-Ag-As minerals, and electrum 

with subequal proportions of Au and Ag. Silver minerals, 

some of which are euhedral, and electrum are paragenetically 

later than sphalerite and galena (fig. 42A, B). In an archival 

specimen from the Addenda Mine, anhedral intergrowths 

of hessite (Ag 2Te), electrum with subequal proportions of 

Au and Ag, tetrahedrite, chalcopyrite, bornite (not imaged), 

and an Ag-Te-Cu-S phase are intergrown with euhedral and 

subhedral quartz crystals (fig. 43A, B, C ). Samples from 

the Red Cloud and Contention Mine dumps (figs. 44A, B, 

C; 45A, B, C ) consist of assemblages that are similar to the 

Addenda Mine specimen, but also include galena, sphalerite, 

acanthite, and Ag-Au-Te, Cu-Fe-Sn-S, and Ag-S-Fe minerals. 

Sylvanite, acanthite, and bornite (not imaged) were identified 

in separate Red Cloud Mine samples. A dump sample from the 

Maybelle Mine consists of quartz, acanthite with minor Se, 

naumannite, an Ag-Sb-S mineral, an Ag-Sb-Se-Fe-S phase, 

and low Fe-sphalerite; silver minerals are paragenetically later 

than sphalerite and some fill spaces between euhedral quartz 

crystals (fig. 45D). Bulk samples of veins contain markedly 

elevated concentrations of elements of these minerals and 

phases as well as high concentrations of Hg, Bi, Cd and 

numerous other chalcophile elements (table 1-11). Tellurium 

concentrations are markedly anomalous in most samples.
Bodie Mining District 91

Ag1.6As0.2S

~Ag2S

quartz

Pb0.9S

ZnFe0.02S

~Ag7AsS5

Ag1.6As0.1S

Ag.48Au.52

A

quartz

quartz

~Ag7As S5

B

Cu-Fe-S-Ag

Ag-S-Cu-As Ag-Sb-As-S

Ag-S-Cu-As

200 μm

200 μm

Fig. 42

Figure 42. Secondary electron images of samples representative 

of Silver Hill series veins on and near Silver Hill, Bodie Mining 

District. A and B correspond to samples BOD11-1D and BOD11-1H, 

respectively, Oro Mine dump. Imaged phases include quartz, 

galena, sphalerite, acanthite, electrum with subequal Au and Ag, 

Ag-As-S minerals (~Ag1.6As0.2S; ~Ag7AsS5 ), and several Ag-SbAs-Fe-Cu-S minerals or mineral intergrowths. Mine locations are 

shown on figure 37.

In addition to low Au/Ag and textures, vein mineralogy 

clearly distinguishes Silver Hill series veins from all other 

vein types. Dump samples of Silver Hill veins with elevated 

Au and Ag concentrations typically contain several percent to 

>10 percent sulfide minerals, predominantly sphalerite, galena, 

tetrahedrite, and chalcopyrite, whereas other vein types rarely 

contain more than 1 percent metallic minerals. Other common 

and distinguishing minerals in Silver Hill series veins are 

electrum, pyrite, acanthite, bornite, hessite, and sylvanite. 

Hessite and other Te minerals, tetrahedrite and other Cu-AgSb-As-S sulfosalt minerals, bornite, and possibly barite occur 

exclusively in Silver Hill series veins.

Veins On and Near Queen Bee Hill

No production is recorded for veins in the vicinity of 

Queen Bee Hill in the southern part of the district (fig. 37). 

Small amounts of $30–150 per ton ore were found on the 300 

and 500 levels of the Maryland Consolidated Mine (Queen 

Bee Hill), but quantities apparently were insufficient to mill 

(Chesterman and others, 1986). Limited Au and Ag data 

suggest that Au/Ag in these veins is similar to Au/Ag of Silver 

Hill series veins (table 5; Hollister and Silberman, 1995b). The 

Booker (?) vein, between Queen Bee Hill and the Noonday 

Mine, and vein pieces on the University, Maryland, and 

Boston Consolidated Mine dumps, consist of quartz, calcite, 

quartz pseudomorphs after calcite, and pyrite. Veins on Queen 

Bee Hill are <1 m wide and extend to at least 800 ft below the 

surface, but at depth are mostly composed of calcite, based on 

the prevalence of calcite in pieces of vein on dumps.

Wall-Rock Alteration

Alteration of volcanic rocks varies with elevation, 

latitude, vein series, and proximity to veins. It is, in part, 

lithologically controlled. Matrix of lag blocks of volcaniclastic 

deposits on the summit of Bodie Bluff (9,000 ft) has been 

pervasively replaced by very fine-grained quartz and lesser 

pyrite (iron oxides). Small embayments in some blocks are 

filled with thin deposits of finely layered, microcrystalline 

quartz, some of which are draped over rock fragments. The 

blocks are adjacent to partially excavated clasts of sinter 

(probably the sinter with reed casts described by Herrera and 

others, 1993). They represent silicification of volcaniclastic 

matrices and pool sinter subjacent to a small sinter terrace 

that subsequently has been dismembered by deflation and 

frost heaving. Clasts in volcaniclastic deposits include dacite 

of Silver Hill, uncorrelated porphyritic volcanic rocks, and 

small (centimeter-sized) angular to tabular, layered fragments 

of very fine-grained white quartz. Although the white quartz 

fragments resemble layered Incline series veins at the same 

elevation (fig. 37, 39A), they contain concentrations of Au, Ag, 

As, Sb, Rb, and Sr that are indistinguishable from those in terrace sinter, but differ distinctly from those in adjacent Incline 

series veins (fig. 39; table 1-11). The silicified volcaniclastic 
92 Gold-Silver Mining Districts, Alteration Zones, and Paleolandforms in the Miocene Bodie Hills Volcanic Field

Ag1.9Te

chalcopyrite

Ag.33Au.66

chalcopyrite

quartz

quartz

CuCu10.9 10.9SbSb3.13.1ZnZn2.12.1SS1313

Ag1.9Te

Ag2.1Te; minor S

Ag.44Au.56

chalcopyrite

Ag1.9Te

Cu-Fe-Ag-S

chalcopyrite

quartz

AgAg1.9 1.9CuCu0.30.3SS0.10.1TeTe

quart

Cu10.7Sb2.9Zn2.3AsS13

Ag2Te

Ag2Te

chalcopyrite

Ag2Te

Ag.43Au.57

200 μm 200 μm

200 μm

A B

C

Fig. 43

Figure 43. Secondary electron images of samples 

representative of Silver Hill series veins on and near Silver 

Hill, Bodie Mining District. A, B, and C correspond to 

specimen K016, Addenda Mine (Keck museum collection, 

University of Nevada, Reno). Imaged phases include quartz, 

electrum with subequal Au and Ag, hessite, chalcopyrite, 

tetrahedrite, a Cu-Fe-Ag-S mineral, and a Ag-Te-Cu-S mineral 

(~Ag1.9Cu0.3S0.1Te). Location of the Addenda Mine is shown on 

figure 37.

deposits and sinter are the upper strata of the ~60-m-thick 

sequence of volcaniclastic deposits that accumulated in the 

graben on Bodie Bluff (fig. 38; Chesterman and others, 1986; 

Silberman and Berger, 1985; Silberman and Chesterman, 

1991; Herrera and others, 1993).

Volcaniclastic deposits in near-surface mine workings 

on Bodie Bluff, including the upper 100 ft of the old Standard 

shaft, were reportedly soft and decomposed, and covered veins 

in underlying dacite (Whiting, 1888; Brown, 1908). Brown 

(1908) described “dead zones” of fractured and decomposed 

(“pulpy”) andesite on Bodie Bluff that predated veins but 

did not maintain open conduits for mineralizing fluids. It is 

unclear from Brown’s descriptions whether “dead zones” 

included decomposed volcaniclastic deposits. Matrix, and to a 

lesser extent, clasts of volcaniclastic deposits on mine dumps 

at lower elevations on the south slope of Bodie Bluff have 

been altered to K-feldspar, illite, and montmorillonite, but 

primary clastic textures are preserved.

A few meters east and tens of meters west of the blocks 

of silicified volcaniclastic deposits and sinter, dacite, at 

approximately the same elevation, contains Incline series veins 

(centimeters to tens of centimeters thick). The veins consist of 

layers of very fine-grained quartz and lesser adularia. Some 

narrow veins contain internal voids lined with euhedral quartz 

and lesser adularia crystals. Adjacent to veins, centimeter-thick 

selvages of altered dacite consist of quartz, subequal amounts 

of illite and K-feldspar, and several percent iron oxide that 

have replaced phenocrysts and matrix without substantially 

modifying primary texture. 

At elevations several hundreds of meters below the 

summit of Bodie Bluff, vein selvages and brecciated dacite 

adjacent to Incline and Burgess series veins on the south slope 

of Standard Hill (8,588 ft) consist of aggregates of quartz and 

K-feldspar in which grain sizes approach 1 mm. Adjacent 

to Incline series veins, illite partially replaces K-feldspar 

in some aggregates, occurs in small seams between quartz 
Bodie Mining District 93

galena

Ag1.7Au8.3

quartz

quartz

quartz

Cu10.4Fe3.4Sn1.6S13

chalcopyrite

Ag1.9Te

chalcopyrite

Cu10.9Sb3.9Zn0.5S13

Ag1.5Au0.5Te

Cu10.9Sb3.9Fe0.3Zn2.1S13

Cu10.4Sb3.9Zn2.3S13; minor Ag

Pb0.9S

ZnS

Pb0.9S

quartz

quartz

quartz

quartz

chalcopyrite

Cu10.4Sb3.9Zn2.3S13; minor Ag

ZnS

ZnS

Pb0.9S

A

C

B

200 μm 500 μm

200 μm

Fig. 44

Figure 44. Secondary electron images of samples

representative of Silver Hill series veins on and near 

Silver Hill, Bodie Mining District. A corresponds to sample 

BOD11-5A, Red Cloud Mine dump. B and C correspond to 

sample BOD11-5C, Red Cloud Mine dump. Imaged phases 

include quartz, hessite, an Ag-Au-Te mineral (~Ag1.5Au0.5Te), 

tetrahedrite, chalcopyrite, a Cu-Fe-Sn-S mineral, galena, 

and sphalerite. Location of the Red Cloud Mine is shown on 

figure 37.

layers in veins, and with quartz, K-feldspar, and pyrite, 

partially replaces dacite fragments in veins and breccias. 

Centimeter-thick wall-rock selvages adjacent to Burgess 

series veins consist predominantly of K-feldspar, subequal to 

lesser amounts of quartz and clinochlore (XRD analysis), and 

< 2 volume percent pyrite (weathered to iron oxide minerals 

or jarosite). These minerals also cement brecciated dacite near 

veins. An archival sample of dacite adjacent to the Fortuna 

vein on the 526 level of the Standard Mine consists mostly of 

K-feldspar, with lesser quartz and ~2 volume percent pyrite.

Vertical zonation of alteration mineral assemblages has 

been described by O’Neil and others (1973) and Herrara 

and others (1993). Pervasive K-feldspar-dominant alteration 

assemblages extend about 100–150 m beneath Bodie Bluff. 

Mass balance calculations based on major oxide and minor 

element analyses of unaltered and altered rocks (O’Neil 

and others, 1973) demonstrate enrichment of K and Rb and 

depletion of Na, Ca, Mg, and Sr in dacite adjacent to veins 

on Bodie Bluff; Si and Al abundances were not changed 

significantly by alteration processes at these high elevations. 

Wall-rock selvages of altered dacite adjacent to veins narrow 

with increasing depth. At depth, selvages include sericite that 

has replaced K-feldspar, and below ~8,500 ft may include 

kaolinite in addition to quartz and pyrite. Distal to veins, 

feldspar and mafic phenocrysts in dacite are variably altered to 

chlorite, illite, montmorillonite, calcite, and lesser pyrite and 

zeolite minerals. Epidote is uncommon and spatially unrelated 

to veins, but may be coeval with these distal propylitic 

alteration minerals.

Alteration mineral associations in dacite spatially 

associated with Silver Hill series veins consist of quartz, illite, 

kaolinite, montmorillonite, and pyrite (iron oxides). Variable 

proportions of these minerals have replaced phenocrysts and 

matrices as much as tens of meters from veins. Although few 

veins are exposed near Silver Hill, wall rocks on mine dumps 

display more pervasive clay-mica alteration than altered 
94 Gold-Silver Mining Districts, Alteration Zones, and Paleolandforms in the Miocene Bodie Hills Volcanic Field

quartz chalcopyrite

Ag1.6S

quartz

Ag2S Ag-Fe-S

galena

galena

Ag-Fe-S ZnS

Ag1.6S

quartz

quartz Ag1.7Te; minor Cu, S

ZnS

quartz

quartz

Ag1.5Zn0.2S; minor Se

Ag5.5Sb1.1S4

Ag6.9Sb0.7Se0.6Fe0.3S4

Ag1.6S; minor Se

Ag5.6SbS4

ZnFe0.02S

Ag-S-Se

C. Contention Mine D. Maybelle Mine

A. Red Cloud Mine B. Red Cloud Mine

200 μm 200 μm

600 μm 500 μm

Fig. 45

Figure 45. Secondary electron images of samples representative of Silver Hill series veins on and near Silver Hill, Bodie Mining 

District. A and B correspond to sample BOD09-3C, Red Cloud Mine dump. C corresponds to sample BOD09-4A, Contention Mine dump. 

D corresponds to sample BOD09-6, Maybelle Mine dump. Imaged phases include quartz, acanthite with minor Se, chalcopyrite, galena, 

sphalerite, hessite, a Ag-Fe-S mineral, Ag-Sb-S minerals, a Ag-Zn-S mineral, a Ag-S-Se mineral, and a Ag-Sb-Se-Fe-S mineral or 

mineral intergrowth. Mine locations are shown on figure 37.
Bodie Mining District 95

wall rocks associated with other vein series. The smooth, 

beige-colored dumps in the vicinity of Silver Hill contrast 

sharply with dumps on Standard Hill and Bodie Bluff, which 

are dominated by reddish-brown to green, angular blocks of 

K-feldspar- and illite-altered dacite. 

Absolute and Relative Vein and Sinter Ages

Based on 40Ar/39Ar adularia dates, Incline series veins 

vary in age from ~8.3–8.1 Ma (table 1). They are exposed 

mostly on Bodie Bluff and Standard Hill (fig. 37), but also are 

represented on the Noonday Mine and Oro Mine dumps which 

are linked by underground workings. Burgess series veins and 

Silver Hill series veins, which are distinguished from Incline 

series veins by textures, vein mineral assemblages, and wallrock alteration, vary in age from ~8.5 to 8.4 Ma and ~8.9 to 

8.5 Ma, respectively (table 1). However, there are no exposures from which the relative vein ages assigned by Brown 

(1908), or those determined by 40Ar/39Ar geochronology, can 

be verified. Based on adularia dates, contrasting minor element 

concentrations (fig. 46; table 1-11), and common elevations 

(fig. 37), Incline series veins postdate sinter atop Bodie Bluff, 

and sinter may be temporally equivalent to Burgess or Silver 

Hill series veins. The Fortuna vein has not been dated. If the 

crosscutting relationships among veins shown on figure 38 are 

valid, then the Fortuna vein is older than Incline and Burgess 

series veins.

Narrow veins (millimeters to centimeters wide) on 

Bodie Bluff that are juxtaposed with mined Incline and 

Burgess series veins consist of quartz and adularia layers 

with internal lenticular vugs containing millimeter quartz 

and adularia crystals. Adularia dates of 8.4 Ma and 8.2 Ma 

(table 1, uncorrelated veins), and to an extent, wall-rock 

alteration suggest that these veins are temporally associated with Burgess and Incline series veins, respectively, 

although there are no metallic minerals that might confirm 

associations. The narrow vein ages, coupled with the spread 

in adularia dates within vein series, imply that a succession of 

hydrothermal events followed eruption of dacite of Silver Hill 

at ~9.1–8.9 Ma (table 1). The ~8.9–8.1 span of hydrothermal 

events in the Bodie Mining District is partly contemporaneous 

with ~8.6–8.0 Ma trachydacite of Willow Springs, and with 

the Cinnabar Canyon-US 395 alteration zone (~8.8–8.2 Ma; 

table 1), ~8 km or more west of the district (fig. 1).

Minor Elements in Veins and Wall Rocks

The distribution of minor elements and oxygen isotope 

values in veins and wall rocks has been determined in numerous investigations (Silberman and Berger, 1985; O’Neil and 

others, 1973; Silberman, 1991; Silberman and Chesterman, 

1991; Herrera and others, 1993; Hollister and Silberman, 

1995a; 1995b). Concentrations of As, Zn, Sb, Mn, Ba, and Sr 

in veins vary from low parts per million to hundreds of parts 

per million, whereas Au, Hg, Ag, Tl, B, Co, Cu, Ni, and Pb 

concentrations vary from low parts per million to tens of parts 

per million. Many published analytical data sets overlap and 

spatial gradients among element concentrations are mostly 

inconsistent or difficult to recognize. Minor element distributions from numerous sources are synthesized as follows.

The vertical distribution of minor elements in sinter 

and Incline series veins from the top (~9,000 ft) to the 

base (~8,400 ft) of Bodie Bluff shows both variation and 

relative constancy. Sinter (9,000 ft) contains <1 ppm Au, 

Hg, and Tl, ~180 ppm As, ~280 ppm Sb, and low ppm 

concentrations of Cu, Pb, and Zn. At ~8,720 ft (Upper Hobart 

Tunnel), Au and Ag concentrations in Incline series veins 

(~0.1–100 ppm) are 10 or more times higher than at 8,400 ft 

(Bodie Tunnel), whereas concentrations of Sb (1–~ 60 ppm), 

Hg (0.01–~11 ppm), Tl (<7.5 ppm), Cu (~2–70 ppm), 

Zn (~10–100 ppm), and Sr (~100–800 ppm) are broadly 

similar. Arsenic (~2–490 ppm), Mn (~8–10,000 ppm), Pb 

(~2–80 ppm), and Ba (10–1,100 ppm) concentrations are 

generally elevated in Bodie Tunnel samples relative to samples 

from higher elevations.

Gradients in the vertical distribution of minor elements 

in altered dacite are more difficult to interpret because all 

high-elevation samples contain quartz veins, whereas samples 

from lower elevations do not. Elements that display relatively 

consistent concentrations at 9,000 and 8,400 ft include As 

(190 to 6 ppm, respectively), Zn (low to 110 ppm), and Sb 

(130 to low ppm). Gold, Ag, Tl, and Hg concentrations vary 

little with elevation. Other minor element concentrations are 

elevated locally, but variations show minimal or no correlation 

with elevation.

Lateral distribution of Sr, Rb, Au, and oxygen isotopes in 

dacite wall rocks and a 0.6-m-wide Incline series vein in the 

Upper Hobart Tunnel show higher Sr (~100–700 ppm) and 

Rb (~130 – 400 ppm) concentrations, and higher 18O values 

(~− 0.1 to −2.1 ‰) in dacite, and higher Au concentrations 

(0.04 – 4.2 ppm) in the vein. Slight gradients are implied by 

decreasing Sr and Rb and increasing 18O values with distance 

from the vein, although sample density is inadequate to 

substantiate trends. Concentrations of Zn, Ag, As, and Tl in 

dacite either decrease abruptly with distance from the dacitevein contact (Ag, Tl), or display no systematic trend (Zn, As). 

δ18O values in other whole rock and phenocryst samples from 

Bodie Bluff and Standard Hill indicate variable exchange 

between dacite and meteoric water.

Concentrations of Au, Ag, Cu and other elements in 

veins on Bodie Bluff and Standard Hill, in Silver Hill series 

(“polymetallic”) veins, in veins on Queen Bee Hill, and in 

wall rocks have been compared by Hollister and Silberman 

(1995b). Silver-gold ratios in veins and wall rocks at 9,000 ft 

on Bodie Bluff (presumably Incline series veins) are 2.3 and 

21, respectively, and at 8,400 ft are 19 and 31. Silver-gold 

ratios in Silver Hill series veins and wall rocks are 244 and 

43, respectively, and in veins and wall rocks on Queen Bee 

Hill are 6.6 and 104, respectively. Cu-Au ratios in Silver 

Hill series veins are several orders of magnitude higher than 

in Bodie Bluff and Queen Bee Hill veins. These element 
1 cm Counts/second Counts/second Counts/second Counts/second 102 102 104 104 106 102 104 106 102 104 106 106

Line of traverse

Au Ag As <Hg Sb 53S <Tl <Fe Bi <Se <Te <

A B Bodie Bluff sinter (BODB06-4A)

C

Bulk c(ppm; 

107Ag

202Hg

197Au

209Bi

121Sb

27Al

39K

137Ba

69Ga

88Sr

44Ca

23Na

63Cu

208Pb

66Zn

118Sn

75As

57Fe

34S

34S

31P

232Th

238U

Figure 46. A, Image showing oriented consecutive sections of sinter from Bodie Bluff summit, Bodie Mining District (BODB06-4A; fig. 37). B, G

element concentrations in sinter measured in counts per second (counts/second) by laser ablation inductively couple plasma-mass spectromesample element concentrations determined by inductively coupled plasma-atomic emission spectrometry-mass spectrometry (ICP-AES-MS). Lscale) element concentrations include Au, Ag, Hg, S, Sb, Cu, As, Fe, Sn, Bi, Zn, Pb, and Ba, most of which are not elevated in the bulk sample.
Bodie Mining District 97

concentrations and ratios in veins, at least, are corroborated 

by vein mineralogy described previously, and by production 

records (table 5).

Minor element concentrations in sinter atop Bodie Bluff 

(9,000 ft; fig. 37) were determined for possible element 

correlations between sinter and veins (Vikre, 2007). Element 

concentrations, determined by LA ICP-MS along a continuous 

traverse orthogonal to sinter beds, include local (submillimeter 

scale) enrichment of Ag, Sb, Hg, S, Bi, As, Fe, Cu, Pb, Ba, and 

other elements (fig. 46). Bulk analyses of the traversed sinter 

beds, and of other sinter samples (table 1-11), show elevated 

concentrations of Sb, Hg, As, Tl, and Se, but some elevated 

concentrations at the millimeter scale (for example, Ag, Bi) 

are not elevated in bulk samples. Based on these analyses, 

sinter cannot be correlated unequivocally with any specific 

vein series (table 1-11).

Elevated concentrations of Sb, Hg, As, and Pb in some 

bulk sinter samples and in Silver Hill series veins broadly 

correspond, whereas Au, Ag, Bi, Cu, Se, Sn, Te, and Zn are 

enriched in Silver Hill series veins but not in sinter. Element 

concentration correlations between Incline and Burgess series 

veins and sinter are fewer and include similar As, Pb, and Sb 

concentrations in some samples (table 1-11). Sinter and Incline 

series veins at the same elevation on the summit of Bodie 

Bluff contain, in part, similar As, Sr, and Sb concentrations, 

but Au and Ag concentrations in sinter are as much as two 

orders of magnitude lower than those in veins (fig. 47).

Fluid Inclusion Microthermometry

Limited fluid inclusion microthermometric analyses 

and petrographic descriptions of fluid inclusions have been 

published. A fluid inclusion “filling temperature” of 245 °C 

and salinity of 0.3 weight percent NaCl equivalent in a sample 

of vein quartz from the McClinton Mine dump (atop Standard 

Hill, ~8,720 ft; presumably an Incline series vein), were 

determined by J.T. Nash and reported by O’Neil and others 

(1973). Hollister and Silberman (1995b) described saturated 

fluid inclusions (containing as many as four daughter minerals) in a polymetallic vein sample from the vicinity of Silver 

Hill (presumably a Silver Hill series vein), but provided no 

microthermometric data.

Oxygen and Hydrogen Isotope Compositions of 

Vein Minerals and Fluid Inclusion Water

Oxygen isotope values of vein quartz ± adularia, and 

hydrogen isotope values of fluid inclusion water in vein 

quartz ± adularia, were determined by O’Neil and others 

(1973) and O’Neil and Silberman (1974) for samples from 

the McClinton Mine dump and Upper Hobart Tunnel (fig. 37; 

presumably Incline series veins), Red Cloud Mine dump 

(presumably Silver Hill series veins), and of the Fortuna vein 

(fig. 38). The δ18O values of water in equilibrium with quartz, 

calculated at an assumed fractionation temperature of 250 °C, 

vary from −3.0 to −0.1 ‰; the δD values of water vary from 

−108.1 to −97.6 ‰. These isotope values imply that vein 

components were transported by, and deposited from, meteoric 

water-dominated fluid, and very high water-rock ratios during 

hydrothermal events. The δD values of kaolinite and K-mica, 

−133.2 and −127.3 ‰, respectively, are also compatible with 

meteoric water-mineral equilibration. Lower equilibrium 

temperatures of 228 °C and 123 °C were calculated for 

coexisting quartz and calcite in a vein sample from the Red 

Cloud Mine dump; the temperature differences reflect different 

experimentally determined quartz-water fractionations (O’Neil 

and others, 1973; O’Neil and Silberman, 1974).

Sulfur Isotope Compositions of Vein Minerals

The δ34S values of sulfide minerals in Bodie district veins 

were determined for comparison with those of hydrothermal 

minerals in other mining districts and alteration zones in the 

Bodie Hills volcanic field (table 2). In Bodie district veins, 

δ34S values vary by ~ 6 ‰ (−4.7 to 1.4 ‰) with a mode 

of ~ 0 ‰, indicative of a reduced and fairly isotopically 

homogenous source; the values are broadly similar to values 

of sulfide melt inclusions in mantle rocks (Chaussidon and 

others, 1989) and are consistent with a magmatic source of 

sulfur. The ~ 0 ‰ mode and near absence of hypogene sulfate 

minerals distinguish Bodie district veins from sulfide-sulfate 

mineral assemblages in the Masonic Mining District, and in 

the Red Wash-East Walker River, Sawtooth Ridge, Potato 

Au (ppb); Sb, Rb (ppm)

1 10 100 1,000 10,000 100,000

Ag, As, Sr (ppm)

0.1

1

10

100

1,000

Sr-Rb in 

sinter and 

sinter 

fragments

As-Sb in 

sinter and 

sinter 

fragments

Ag-Au in sinter 

and sinter 

fragments

Ag-Au, As-Sb, and Sr-Rb in 

Incline series veins

Bodie Bluff Summit

EXPLANATION

Sinter (dismembered sinter terrace)

Sinter fragments (in volcaniclastic deposits

Incline series veins

Figure 47. Graph of Ag, As, Sr concentrations versus Au, Sb, 

Rb concentrations in sinter from the dismembered sinter terrace, 

sinter fragments in volcaniclastic deposits, and Incline series 

veins, Bodie Mining District, Bodie Bluff summit. Elevation of all 

samples is 8,960±20 ft.
98 Gold-Silver Mining Districts, Alteration Zones, and Paleolandforms in the Miocene Bodie Hills Volcanic Field

Peak, and Cinnabar Canyon-US 395 alteration zones. The δ34S 

values of sulfide and sulfate minerals at Masonic and most 

alteration zones reflect disproportionation of magmatic SO2

(Rye, 2005). The δ34S values of Bodie district veins have much 

less variance than those of Aurora district veins. The larger 

range in values at Aurora may reflect unrecognized sulfate 

minerals, or more than one sulfur source. 

ASTER Imagery

ASTER imagery of the Bodie Mining District (Rockwell, 

2010) shows a fairly contiguous cluster of pixels in the area 

between the Mono Fault and Silver Hill that corresponds to 

kaolinite, smectite, smectite/montmorillonite, and quartz. Less 

dense pixel clusters, coincident with Standard Hill and Bodie 

Bluff, correspond to illite, smectite/montmorillonite, and 

quartz. Diffuse pixels, coincident with the area between Bodie 

Bluff and Queen Bee Hill, correspond to illite.

SWIR Spectra; XRD Analyses

SWIR and XRD analyses of hand samples and subsamples show that altered dacite, adjacent to Incline series 

veins on Standard Hill, contains illite, K-feldspar, quartz, 

and small amounts of pyrite (iron oxides). Dacite adjacent 

to Burgess series veins contains clinochlore, and possible 

montmorillonite, in addition to quartz, K-feldspar, and small 

amounts of pyrite (iron oxides). Altered volcaniclastic strata 

and dacite on Bodie Bluff (Tioga Mine dump) contain illite/

smectite, and montmorillonite. Hydrothermal minerals in 

dump samples of Silver Hill series veins include adularia and 

illite in addition to quartz.

Spring Peak Sinter

Location

Sec. 34, T. 5 N., R. 28 E., Mineral County, Nevada (fig. 1)

Definition

The Spring Peak sinter consists of a partially dissected 

sinter terrace with west-east and north-south dimensions of 

~ 0.2 and 0.1 km, respectively (0.02 km2; fig. 48). The terrace 

overlies altered volcaniclastic deposits and Cretaceous granitic 

and Mesozoic metamorphic rocks on a low west-east ridge. 

The ridge is near the eastern margin of an area of erratically 

altered trachyandesite of Aurora, Pliocene volcanic rocks, and 

Cretaceous granitic rocks that extends south and east from the 

Aurora Mining District and East Brawley Peak (figs. 16, 48). 

Temporal relationships between the Aurora Mining District, 

the East Brawley Peak alteration zone, Spring Peak sinter, and 

the west-east zone of altered rocks that underlie the Spring 

Peak sinter have not been completely determined.

History and Production

No production is recorded from the Spring Peak sinter 

terrace or subjacent rocks. Small prospect pits were excavated 

in altered volcanic and pre-Tertiary rocks west, northwest, 

and east of the terrace, and a small prospect pit in the terrace 

exposes opaline silica with minor amounts of cinnabar. Cinnabar also occurs in chalcedonic and opaline sinter at the eastern 

edge of the terrace. Small pieces (centimeters in dimension) 

of layered vein, some of which contain elevated gold and 

silver values, lie on the south slope of the sinter-capped, 

west-east ridge. Nineteen, relatively shallow holes (≤ 505 ft 

deep; Kinetic Gold Corp., 2013) were drilled in the 1980s to 

determine if precious metal deposits occur beneath or lateral 

to the sinter terrace. Recent geological mapping, geochemical 

analyses, and geophysical interpretation have been used to 

correlate layered vein float with sinter and other alteration 

mineral assemblages (Kinetic Gold Corp., 2013). The Spring 

Peak sinter and subjacent rocks represent a relatively intact 

sinter-vein system that contains elevated concentrations of Au, 

Ag, Hg, Sb, and As.

Stratigraphy

The oldest rocks in the vicinity of the Spring Peak sinter 

are Cretaceous granitic rocks, and Mesozoic metamorphic 

rocks, presumably correlative with rocks of the Excelsior 

Formation (Al-Rawi, 1969; Silberman and others, 1995; 

Breit, 2000; divided by Speed, 1977 into the Mina, Gold 

Range, and Black Dyke formations). Thin (meters-thick) 

altered volcaniclastic strata underlie the sinter terrace and 

unconformably overlie pre-Tertiary rocks on the west end of 

a small hill tens of meters (>100 ft) east of the terrace. The 

terrace has a maximum thickness of ~5 m at its northeastern 

edge, but is <1 m thick elsewhere where it is largely 

dismembered into meter-sized blocks and smaller clasts of 

float. Much of the northeastern terrace margin consists of 

large to small blocks (meters in dimension) that are slightly 

tilted (fig. 48). The gray- to brown-weathering volcaniclastic 

substrate is moderately well-sorted and bedded, sand and 

silt. Larger feldspar and quartz fragments (centimeter-sized) 

in sand beds were apparently derived from subjacent Cretaceous granitic rocks.

Cretaceous granitic rocks consist of very light-gray to 

yellowish-gray hypidiomorphic granular, porphyritic quartz 

monzodiorite with prominent, euhedral, perthitic, pink 

potassium feldspar megacrysts 2–3 cm long. The mediumgrained quartz monzodiorite contains about two percent 

tan- to greenish-brown biotite, mostly replaced by chlorite. 

Mesozoic metamorphic rocks intruded by quartz monzodiorite 

in the Spring Peak sinter area are similar to those in the 

Masonic Mining District.
Spring Peak Sinter 99

}mv

Trsp

Trsp

Trsp

Tvc

Tvc

Tvc

KJqmd

Tach

Tf

Tf

Trsp

Trsp

Taa Qc

Qc

Tach

Trsp

Trsp

Trsp

Qc

Qc

Qc

Qc

SPK11-2

SPK10-1

SPK11-1

SPK11-4

SPK11-7

SPK11-6

SPK11-5

SPK11-4A SPK11-3

SPK06-2

Hg 

prospect

SPK06-1

N

EXPLANATION

}mv

Photograph location

Colluvium

Aurora Volcanic Field

Trachyandesite of Mount 

Hicks (Pleistocene)

Rhyolite of Spring Peak 

(Pliocene)

Trachyandesite of Cedar Hill 

(Pliocene)

Sinter

Silicified volcaniclastic 

rocks (Tvc) and silicified 

fanglomerate (Tf)

Bodie Hills Volcanic Field

Trachyandesite of Aurora 

(Miocene)

Granitic and metamorphic 

rocks

Quartz monzodiorite of 

Aurora (Cretaceous or 

Jurassic)—Quartz veined 

and altered to kaolinite 

near sinter (line-pattern 

on map) Trachyandesite of 

Cedar Hill (Pleistocene)

Metavolcanic rocks 

(Mesozoic)

Contact—Dashed where 

approximated

Bedding

Color air photo (CAP) lineament

Analytic sample site and 

number

5

5

0 0.5

0 0.5

1 MILE

1 KILOMETER

Base modified from U.S. Geological Survey

Mount Hicks, Nev., 1989, Aurora, Nev.-Calif., 1989, 

Cedar Hill, Calif.-Nev., 1994, and Kirkwood Spring, Calif.-Nev., 1989, 1:24,000

B

A

Fig48

Qc

Qmh

Tach

Trsp

Tsi

Taa

KJqmd

Tvc Tf

119°15' 119° 118°45'

38°25'

38°15'

38°05'

CALIFORNIA

NEVADA

Mono Lake

Mono Valley

Bridgeport

Fletcher Valley

East

Walker

River

Masonic

Bodie

Aurora Area of map

Figure 48. A, Geologic map of the Spring Peak sinter, Mineral County, Nevada, modified from Breit (2000) and John and others (2012). 

B, Image showing nearly intact sinter beds from the northern margin of the terrace.
100 Gold-Silver Mining Districts, Alteration Zones, and Paleolandforms in the Miocene Bodie Hills Volcanic Field

Structure

No obvious structures control the morphology of the 

Spring Peak sinter terrace. A prominent west-east lineament on 

color air photos (CAP lineament; fig. 48) borders the terrace 

to the south. This lineament extends to the west through 

the southern part of the East Brawley Peak alteration zone 

(fig. 16), and may have regionally displaced veins in the 

Aurora Mining District.

Hydrothermal Alteration

Sinter consists of bedded chalcedonic quartz, opaline 

silica, and hackly voids (former rock fragments and bioherms) 

that contain small amounts of illite and montmorillonite. 

Minor cinnabar and a dark-green mineral, possibly nontronite 

(Na0.3Fe3+

2

Si3AlO10(OH)2•4(H2O)), occur locally in bedding 

planes and along fractures, and are finely dispersed in chalcedonic silica. Volcaniclastic strata beneath the sinter have been 

pervasively silicified, and contain as much as several percent 

pyrite, small amounts of kaolinite, and a few <1 mm-thick 

quartz veins.

Quartz monzodiorite, along the western part of the low 

west-east ridge that is partially covered by the sinter terrace, 

has been altered to opaline silica and kaolinite. Local exposures of quartz monzodiorite with disrupted texture apparently 

represent a weathering surface that predates hydrothermal 

alteration. Layered quartz veins (centimeters wide) occur in 

float at sub-sinter elevations on the south side of the ridge 

of quartz monzodiorite. These veins consist of fine-grained 

quartz, K-feldspar, and minor sericite.

Samples of sinter and subjacent rocks contain as much 

as 27 ppm Hg, tens to >1,000 ppm As, and hundreds to 

>1,000 ppm Sb (table 1-12). A few samples contain elevated 

concentrations of Au (tens to >126 ppb), Ag, Ba, Mo, and W. 

Higher Au concentrations (several parts per million) were 

encountered in drill holes and in samples of layered vein float 

(Kinetic Gold Corp., 2013). Minor element concentrations, 

determined by LA ICP-MS, along continuous traverses 

orthogonal to sinter beds (figs. 49, 50, 51) define local 

(submillimeter) enrichments of Au, Ag, Hg, S, As, Bi, Tl, 

Fe, and other elements. Bulk analyses of the traversed beds 

indicate slightly to markedly elevated concentrations of Au, 

Sb, Hg, and Fe, but many elements with elevated concentrations at the millimeter scale (for example, As, Bi, Tl, and Ag) 

are not anomalously concentrated in bulk samples.

Hydrothermal Mineral Ages

Spring Peak sinter has not been dated directly, but its age 

is somewhat constrained stratigraphically. Altered rhyolite 

(possibly Pliocene rhyolite of Spring Peak) and silicified 

Tertiary fanglomerate in the west-east zone of altered rocks 

that includes the sinter terrace (fig. 48) imply that the sinter is 

Pliocene or younger.

Evolution of Landforms During Assembly 

and Alteration of the Miocene Bodie Hills 

Volcanic Field

Characteristics of mining districts and alteration zones, 

coupled with volcanic stratigraphy and geochronology, can 

be used to reconstruct Miocene landform evolution during the 

assembly, alteration, and erosion of the Bodie Hills volcanic 

field. Detailed mapping and dating of volcanic rocks, Au-AgCu deposits, and alteration zones has enabled identification of 

erosional paleosurfaces (lithologic contacts between volcanic 

flows and volcaniclastic deposits) closest in age to the hydrothermal systems. In several mining districts and alteration 

zones, hydrologic paleosurfaces (surfaces during hydrothermal 

activity) are marked by remnant terrace and pool sinters. In 

eroded mineralized and altered areas, the relative elevations of 

paleopotentiometric surfaces (groundwater saturation surfaces) 

can be estimated from vein fluid inclusion microthermometry, 

vein sulfur isotope equilibrium temperatures, and more 

generally, alteration mineral assemblages. Based on climatic 

evidence (Aldrich Station flora), potentiometric surfaces 

in the Bodie Hills during the middle Miocene were largely 

equivalent to hydrologic surfaces. Comparison among present 

elevations of erosional paleosurfaces, hydrologic paleosurfaces, and paleopotentiometric surfaces above exposed veins 

can be used to estimate (1) thicknesses of host rocks, veins, 

and mineralized and altered rocks that have been eroded; 

(2) postmineralization fault displacements; and (3) depths 

at which high-grade sections of veins and mineral deposits 

formed. The restoration of paleosurfaces and paleotopography 

within mining districts and alteration zones, based on fluid 

dynamics, volcanic stratigraphy, and geochronology, enables 

larger scale reconstruction of landforms as they evolved the 

during assembly and alteration of the entire volcanic field 

(fig. 52). Key datums for this reconstruction are the Aldrich 

Station flora and Eureka Valley Tuff.

Aldrich Station Flora and Fossils in the 

Bodie Hills

The ~11 Ma Aldrich Station flora (Axelrod, 1956; Evernden and James, 1964; Gilbert and Reynolds, 1973; Millar, 

1996), ~22.5 km north of the Aurora Mining District, occurs 

in tuffaceous shales that accumulated during Bodie Hills 

volcanism (fig. 52B). The flora consists of riparian species that 

grew in fluviolacustrine basins, and species representative of 

conifer forests and live oak woodlands that grew on bordering 

volcanic uplands with hundreds of feet or relief. The prevailing subhumid climate was more equable than present climate 

with ~64 cm or more of winter and summer precipitation. In 

basins, groundwater saturation was at or above land surface, 

whereas in volcanic uplands, groundwater saturation was 

apparently within meters below the surface.
Counts/second Counts/second

102 104 106 102 104

1 cm

Line of traverse

34S

205Ti

209Bi

57Fe

Au Ag <As <3Hg Sb 83S <Tl <Fe Bi <

A B

C

Bulk co

(ppm; I

107Ag

121Sb

202Hg

75As

197Au

Spring Peak sinter I. (SPK06-2)

Fig. 49

Figure 49. A, Image of sample of Spring Peak sinter from the Hg prospect in the sinter terrace, Spring Peak alteration zone (fig. 48). B, Gr

relative element concentrations in sinter measured in counts per second (counts/second) by laser ablation inductively coupled plasma-ma(LA ICP-MS). C, Bulk sample element concentrations determined by inductively coupled plasma-atomic emission spectrometry-mass specAES-MS). Locally elevated (millimeter-scale) element concentrations include Au, Hg, Ag, Sb, Fe, and S.
35Cl 27Al 23Na31P 63Cu 95Mo 208P

66Z

118Sn 12C39K 44Ca 103 103 105 105 107 

Counts/second Counts/second 1 cm

Line of traverse

A B

Spring Peak sinter II. (SPK06-2)

Figure 50. A, Image of sample of Spring Peak sinter from the Hg prospect in the sinter terrace, Spring Peak alteration zone (fig. 48). B, Graphs 

element concentrations in sinter measured in counts per second (counts/second) by laser ablation inductively coupled plasma-mass spectromC, Bulk sample element concentrations determined by inductively coupled plasma-atomic emission spectrometry-mass spectrometry (ICP-AESsection as in figure 49 showing additional elements. Locally elevated (millimeter-scale) element concentrations include Sn, Mo, Cu, Zn, Pb, K, A
1 cm

Line of traverse

A B

Counts/second Counts/second Counts/second

102 104 106 102 104 104 106 106 108

Spring Peak sinter III. (SPK06-3)

107Ag

202Hg

34S

197Au 209Bi

206Ti

75As

57Fe

23Na

27Al

44Ca

35Cl

12C

39K

Figure 51. A, Image of oriented consecutive sections of sinter from the northern edge of the Spring Peak sinter terrace (fig. 48). B, Graphs sho

element concentrations in sinter measured in counts per second (counts/second) by laser ablation inductively coupled plasma-mass spectromC, Bulk sample element concentrations determined by inductively coupled plasma-atomic emission spectrometry-mass spectrometry (ICP-AESelevated (millimeter-scale) element concentrations include Au, Ag, Hg, S, As, Bi, Tl, Fe, K, Al, Na, and Ca.
Red Wash-East Walker River alteration zone Masonic district 38°10' 0 5 0 5 10 MILES 10 KILOMETERS 38°25'119°15' 119° Bodie Bodie Aurora River Walker East Ancestral Masonic Mountain Bridgeport Valley Bridgeport Reservoir Masonic Volcanic Center 15–13 Ma MINERAL COUNTY MONO COUNTY 

MINERAL COUNTY MONO COUNTY 

Pre-Tertiary Rocks

Aldric

~

119°15' 119°

Ancestral 

Masonic 

Mountain

Bridgeport Valley

River Walker

East

Willow Springs

Paramount Basin 9.7–9.3 Ma

Sawtooth Ridge 

Alteration Zone

East Altera

Auro

Ancestral 

Bald Peak

Ancestral 

Bald Peak

Ance

Large- and East 

small-volume

volcanic centers 

11–10 Ma

38°10'

38°25'

Bridgeport Valley

River Walker

East

Paleodrainages

Eureka Valley Tuff

9.3 Ma

Willow Springs

Willow Springs

Bridgeport Valley

River Walker

East

Cinnabar CanyonUS395 

Alteration Zone

Large-volume 

volcanoes 10–8 Ma

Bodie

Potato Peak(10,237)

Auror

Bridgeport

Bridgeport

Bridgeport Bridgeport

Aurora

Silver Hill

Bodie district

Mount Biedeman (8,962)

Fletcher Valley Fletcher Valley

Fletcher Valley

WillowSprings

C D

A B
Spring Peak Sinter 105

Figure 52. (Facing page) Maps showing assembly of the Miocene Bodie Hills volcanic field, California and Nevada, from 15 to 8 Ma 

based on volcanic stratigraphy (John and others, 2012), mineral deposits, alteration zones, and geochronology. A, Northwestern part of 

the field, 15–13 Ma, consisting of the Masonic volcanic center (green-gray), which includes 15–14 Ma trachyandesite of Masonic and 

associated volcaniclastic strata, 13.5–12.9 Ma trachyandesite domes, 13.4–13.3 and 13 Ma Au-Ag-Cu deposits of the Masonic Mining 

District (horizontal line pattern), and the 13.3 Ma Red Wash-East Walker River alteration zone (cross-hatch pattern). Pre-Tertiary rocks 

are uncolored. B, Eastern, central, southwestern, and northeastern parts of the field, 13–9.3 Ma, and the Masonic volcanic center 

(from A; subdued green-gray). The Aurora volcanic center (yellow-green) includes 13–12 Ma trachyandesite of Aurora, ~12 Ma East 

Brawley Peak alteration zone (cross-hatch pattern), and ~10.5 Ma Au-Ag vein deposits of the Aurora Mining District (horizontal line 

pattern). The 11.1 Ma Sawtooth Ridge alteration zone (cross-hatch pattern) is adjacent to the Aurora volcanic center to the northwest. 

Central and southwestern parts of the field (uncolored) include ~11–10 Ma large- to small-volume flows and domes of trachyandesite, 

rhyolite, and trachydacite (dashed-line enclosures), some of which cover rocks of the Masonic and Aurora volcanic centers, and 

~9.7–9.3 Ma Paramount basin (Paramount-Bald Peak alteration zone; blue). Basin-fill deposits of ancestral Fletcher Valley (brown) 

north of the Aurora volcanic center, and covering parts of the Masonic volcanic center are ~≤11 Ma. C, Northwestern, central, and 

southwestern parts of the field at 9.3 Ma, and the Masonic volcanic center (subdued green-gray), Aurora volcanic center (subdued 

yellow-green), large- to small-volume flows and domes (subdued dashed line enclosures), the Paramount basin (subdued blue,) and 

ancestral Fletcher Valley (brown; from A and B). Eureka Valley Tuff (Eureka Valley Tuff; 9.5–9.3 Ma; red with dot pattern), derived 

from the Little Walker caldera ~20 km to the west of Bridgeport, filled depressions and paleochannels (dark, short dashed lines), 

defined by semialigned Eureka Valley Tuff remnants, in the Masonic volcanic center, and among large- and small-volume flows and 

domes. D, Southeastern part of the field, 10–8 Ma, older volcanic and sedimentary strata (from A, B, and C, subdued), and <9.3 Ma 

normal faults. Large-volume stratovolcano and flow-dome complexes include 10–9 Ma trachyandesite of Mount Biedeman (green), 

~9 Ma trachydacite of Potato Peak (red), ~9 Ma dacite of Silver Hill (orange), and 8.6–8 Ma trachyandesite of Willow Springs (blue), 

and contain the 8.8–8.2 Ma Cinnabar Canyon alteration zone (and S° resource; cross-hatch pattern), and the 8.5–8.1 Ma Au-Ag vein 

deposits of the Bodie Mining District (horizontal line pattern).
106 Gold-Silver Mining Districts, Alteration Zones, and Paleolandforms in the Miocene Bodie Hills Volcanic Field

Although Aldrich Station sediments and flora may not 

have been derived directly from Bodie Hills volcanism and 

vegetation, they broadly reflect climate and geography of 

the region as evidenced by stratigraphic relationships and by 

three occurrences of plant litter in the northern part of the 

Bodie Hills. (1) North and northwest of the Aurora Mining 

District, at elevations of ~7,900 ft (~2.39 km), petrified wood 

fragments in sedimentary rocks of Fletcher Valley (Tfv of 

John and others, 2015), deposited on ~11 Ma trachyandesite 

of Del Monte and beneath 9.3 Ma Eureka Valley Tuff, are 

contemporaneous with Aldrich Station flora. (2) A cored drill 

hole ~6.4 km north of the Aurora townsite (fig. 20) encountered gold-bearing sand and gravel beneath ~ 0.5– 0.1 Ma trachyandesite of Aurora Crater (Lange and others, 1993; Lange 

and Carmichael, 1996), and overlying altered lacustrine 

sediments that contain carbonized plant fragments (Nevada 

Exploration Inc., 2013). The cored stratigraphy, which ranges 

in elevation from 5,470 to ~ 6,100 ft (<1.66 to ~1.85 km), 

corresponds to sedimentary rocks of Fletcher Valley; the goldbearing sand and gravel apparently record erosion of Aurora 

Mining District Au-Ag veins, and the altered sediments may 

be similar in age to those veins (~10.5 Ma). (3) In the Bodie 

Mining District, a 14-in.-diameter silicified tree trunk was 

found in the drainage west of the Bulwer shaft at ~8,400 ft 

(~2.45 km; Brown, 1908; fig. 37).

Bodie Hills fossils attest to the presence of woody 

plants and near-surface groundwater saturation from ~11 Ma, 

the initial sedimentation of Fletcher Valley, to ~8.5 Ma, the 

formation of the youngest veins in the Bodie Mining District. 

Fossil elevations indicate either (1) hundreds to more than 

2,000 ft of relief in the Bodie Hills during this period, or 

(2) differential displacement of fossil-bearing strata since 

~11 Ma by magmatic inflation and (or) faults. Paleoelevation 

estimates of the Aldrich Station flora, which vary by method, 

are 2,000 to 2,500 ft (~ 0.6 to 0.8 km; Axelrod, 1956) and 

~ 4,300 to 6,900 ft (~1.3 to 2.1 km; Wolfe, 1995; Wolfe and 

others, 1997), implying that paleoelevations in the Bodie Hills 

during flora accumulation, and initial Fletcher Valley sedimentation, were either entirely lower than present elevations, or 

near present elevations.

Eureka Valley Tuff in the Bodie Hills

There are few stratigraphic markers among the domes, 

lavas, debris flows, and sedimentary strata that make up the 

Bodie Hills volcanic field, and none is regionally distributed. 

Remnants of externally sourced, ~9.5–9.3 Ma Eureka Valley 

Tuff in the western and central parts of the field (fig. 52) 

provide critical stratigraphic, structural, and age datums. 

Dense to moderate welding, high glass content, confinement 

of thickest exposures (tens of meters) to the deeply incised 

East Walker River drainage, and distance from source vents 

(20–40 km) east of the Little Walker caldera; Pluhar and others, 2009), attest to the low viscosity (high fluidity) of the ash 

flows. Although fluidal ash flows can be deposited on slopes 

(Fisher and Schmincke, 1984), Eureka Valley Tuff exposures 

in the Bodie Hills are the farthest east from their source, and 

waning momentum mostly confined deposition to drainages 

and depressions. Meandering alignments of thinner remnants 

at higher elevations likely reflect paleotributaries, and isolated 

remnants mark depressions or eroded channels. Coarse gravel 

deposits beneath some Eureka Valley Tuff remnants suggest 

locally steep pre-Eureka Valley Tuff drainage gradients. Therefore, it is assumed that Eureka Valley Tuff filled drainages and 

depressions to an approximately common elevation, and that 

basal contacts of Eureka Valley Tuff provide a broad, 9.3 Ma 

elevation datum. Present elevations of remnants span ~3,550 ft 

from the East Walker River west of the Elbow (~5,600 ft; 

fig. 1) to the north slope of Potato Peak (~9,150 ft). This relief 

was imposed since 9.3 Ma, and indicates that most present 

relief in the Bodie Hills was caused by magmatic inflation and 

(or) fault displacement since 9.3 Ma.

Landforms in Mining Districts and 

Alteration Zones

Masonic Mining District

The Au-Ag-Cu deposits at Masonic occur in a sequence 

of Miocene volcaniclastic deposits and trachyandesite lavas 

(trachyandesite of Masonic), and in Mesozoic rocks. Deposit 

ages comprise two groups, one ~13.4–13.3 Ma, and the other 

~13 Ma. Both groups of deposits are younger than trachyandesite lavas (~15–14 Ma, fig. 2; table 1) but are similar to 

the ages of nearby trachyandesite intrusions (~13.5–13.4 and 

12.9 Ma, table 1), demonstrating that the deposits formed 

nearly simultaneously with emplacement of intrusions.

Eureka Valley Tuff (9.5–9.3 Ma) overlies Mesozoic 

rocks and trachyandesite of Masonic in the southwestern 

and northwestern parts of the district, and constrains relative 

elevations of erosional paleosurfaces and fault displacements 

in the northwestern part of the Bodie Hills. Eureka Valley Tuff 

lies on granodiorite and metavolcanic rocks on the northwest 

and south slopes of Masonic Mountain at ~8,600 and 8,775 ft, 

respectively (fig. 2). It lies on trachyandesite of Masonic at 

7,000 to 7,100 ft near the 13.5–13.4 Ma trachyandesite domes 

(fig. 14). These contacts, which represent a common 9.3 Ma 

erosional paleosurface, imply ~1,800 ft of down-to-the north 

displacement of the domes since ~9.3 Ma, relative to Eureka 

Valley Tuff on Masonic Mountain. This displacement can be 

attributed to mapped (figs. 2, 14) and unrecognized, downto-the-north faults, and (or) to domical uplift of the southern 

part of the district. About 600–800 ft of normal displacement 

occurred along a northeast-striking fault that extends through 

the Chemung Mine and across Masonic Gulch at the site of 

Masonic middle town (fig. 2). This fault separates Eureka 

Valley Tuff at 8,600 and 8,775 ft on Masonic Mountain east 

and southeast of the Chemung Mine from Eureka Valley 

Tuff at 8,000 ft, 0.8 km (0.5 mi) north-northwest of the 

Chemung Mine.
Spring Peak Sinter 107

Movement on west-east-striking faults on the north side 

of the 13.5–13.4 Ma trachyandesite domes has displaced 

trachyandesite of Masonic several hundreds of feet down-tothe-north (fig. 14). This estimate is based on the difference in 

elevation of moderately extensive exposures of Eureka Valley 

Tuff near the domes (7,000 to 7,100 ft) and a small exposure 

of Eureka Valley Tuff in the Red Wash-East Walker River 

alteration zone (6,695 ft). Therefore, post-9.3 Ma displacement 

of the Red Wash-East Walker Rive alteration zone relative 

to Masonic Mountain could exceed 2,100 ft (fig. 14). This 

cumulative estimate of post-Eureka Valley Tuff displacement 

is comparable to the elevation differences between Eureka 

Valley Tuff on Masonic Mountain and Eureka Valley Tuff at 

6,400 to 6,600 ft along the East Walker River west of Masonic 

Mountain. The deposition of Eureka Valley Tuff on Mesozoic 

granodiorite indicates that pre-Tertiary rocks of Masonic 

Mountain were exposed at 9.3 Ma and possibly earlier. 

However, granitic and metamorphic clasts have not been 

recognized in 15–14 Ma altered volcaniclastic-flow sequences 

in the Masonic Mining District.

In the southwestern part of the district, a hydrologic 

paleosurface is represented by 13.4–13.3 Ma volcaniclasticpool sinter deposits at the Sarita Mine (fig. 5). The present 

elevation of these sinters, ~8,400 ft, is as much as 200 ft 

higher than altered volcaniclastic strata at the Red Rock, 

Lakeview, and Chemung Mines, ~400 ft higher than the 

intrusive contact of 12.9 Ma Lakeview Spring domes and 

trachyandesite of Masonic, and ~400 ft higher than the 9.3 Ma 

erosional paleosurface at 8,000 ft represented by Eureka 

Valley Tuff on trachyandesite of Masonic, 0.5 km west of the 

domes (fig. 2). Although the dome-trachyandesite contact is 

intrusive, the nearby 9.3 Ma erosional paleosurface implies 

little erosion of domes and adjacent trachyandesite of Masonic 

between 12.9 and 9.3 Ma. The elevation differences among 

the volcaniclastic-pool sinter deposits, volcaniclastic strata, 

and slightly younger domes have several possible explanations 

(1) displacement of the Lakeview Spring domes and volcaniclastic strata at the Red Rock, Lakeview, and Chemung Mines 

relative to the volcaniclastic-pool sinter deposits at the Sarita 

Mine by faulting; (2) emplacement of Lakeview Spring domes 

after displacement of the volcaniclastic-pool sinter deposits 

by faulting; and (3) volcaniclastic-pool sinter landforms 

with hundreds of feet of relief. Several lines of evidence, 

including temporal and elevational relationships among 

Lakeview Spring domes and Eureka Valley Tuff, and sulfur 

isotope equilibrium temperatures of hydrothermal mineral 

assemblages, suggest that fault displacement, explanation (1), 

accounts best for the elevation differences.

Sulfur isotope equilibrium temperatures of coexisting 

pyrite and alunite at four mines range from 188 to 231 °C 

(table 2). These temperatures equate to minimum hydrologic 

paleodepths of ~ 430–1,000 ft, respectively (estimated 

graphically from figure 2 in Haas, 1971), assuming that pyrite 

and alunite precipitated simultaneously in low-salinity water. 

Relative to the Sarita Mine hydrologic paleosurface, present 

elevations of mineral pairs at the Pittsburgh-Liberty Mine 

(−720 ft), aspen grove prospect (−840 ft), and Perini Mine 

(−1,040 ft), are broadly similar to estimated paleodepths 

regardless of alunite age, implying that deposits north and east 

of the Sarita Mine have not been greatly displaced relative to 

the Sarita Mine since ~13 Ma, the age of the youngest alunite. 

However, if the relative hydrologic paleodepth (~1,000 ft) 

based on the Red Rock Mine isotope equilibrium temperature 

(231°C) is accurate, then the Sarita Mine sinters (elev 

~8,400 ft) have been displaced down-to-the-northeast as much 

as 250 m (~800 ft), relative to volcaniclastic strata at the Red 

Rock Mine (elev 8,200 ft), since ~13.3 Ma.

The terraces of landslide debris and fanglomerate 

~0.5 km northwest of the Lakeview Mine (Tls, fig. 2) include 

weathered clasts of Eureka Valley Tuff (at least on present 

surfaces), indicating that some, if not all, mass wasting 

represented by landslide debris has taken place since 9.3 Ma. 

Deformation and mass wasting are also recorded by relatively 

steep and variable west-southwest dips (>40°) of originally 

near-horizontal, 13.4–13.3 Ma volcaniclastic-pool sinter 

deposits at the Sarita Mine, and by large slide blocks and slope 

wash of altered volcaniclastic strata immediately north of the 

Sarita Mine (fig. 2). Although the timing of mass wasting at 

Sarita relative to the displacement and erosion of Eureka Valley Tuff is unconstrained, these catastrophic erosion features 

reflect unstable edifices of altered, volcaniclastic, pool sinter 

deposits that were episodically(?) created by uplift. Based 

on displacement of Eureka Valley Tuff, uplift of Masonic 

Mountain relative to volcaniclastic strata at the Red Rock, 

Lakeview, Chemung, and Sarita Mines primarily occurred 

since 9.3 Ma along the normal, northeast-striking fault on 

the northwest side of Masonic Mountain. However, between 

12.9 and 9.3 Ma, Sarita Mine sinters may have been displaced 

downward relative to Lakeview Spring domes and volcaniclastic strata at the Red Rock, Lakeview, and Chemung Mines 

along a north-trending fault provisionally located between the 

domes and the Sarita Mine (fig. 2). This fault could account 

for the disparity among hydrologic paleodepths derived from 

sulfur isotope equilibrium temperatures.

Synthesis

Paleosurfaces, stratigraphy, structure, and ages of 

hydrothermal and igneous minerals enable conditional 

reconstruction of the geologic and geomorphic evolution 

of the Masonic Mining District. The volcaniclastic rocks 

and lavas (trachyandesite of Masonic) that accumulated in 

depressions or on slopes northwest of Masonic Mountain 

from ~15 to 14 Ma were altered and Au-Ag-Cu-mineralized at 

13.4 –13.3 Ma. These strata were bordered to the southeast by 

an upland of Mesozoic granodiorite and metamorphic rocks, 

and to the west, northwest, and south by trachyandesite lavas 

and domes, the sources of volcaniclastic detritus that filled 

depressions. At 13 Ma, similar Au-Ag-Cu mineralization 

formed in high-angle fault zones north of Masonic Mountain. 

The vertical extent of mineable deposits range from the 
108 Gold-Silver Mining Districts, Alteration Zones, and Paleolandforms in the Miocene Bodie Hills Volcanic Field

paleosurface (marked by the volcaniclastic-pool sinter 

deposits at the Sarita Mine) to ~300 m (~1,000 ft) below the 

surface in the Pittsburg-Liberty Mine. Uplift of the Masonic 

Mountain landform by fault displacement may have begun at 

~13 Ma, but present relief largely reflects uplift since 9.3 Ma. 

Post-9.3 Ma differential displacement of volcaniclastic rocks 

and lavas (trachyandesite of Masonic), volcaniclastic-pool 

sinter deposits, trachyandesite intrusions, and Eureka Valley 

Tuff in the district relative to Eureka Valley Tuff along the 

East Walker River north and west of Masonic Mountain, 

cumulatively totals at least 640 m (~2,100 ft).

Aurora Mining District

The ~10.5 Ma Au-Ag veins at Aurora are nearly entirely 

in ~13.1–12.6 Ma trachyandesite of Aurora; a few veins are in 

11.2 Ma rhyolite of Aurora Creek (table 1). Other premineralization eruptive rocks that overlie trachyandesite of Aurora 

on the north and west sides of the district are 11.5–11.0 Ma 

trachyandesite of West Brawley Peak and 11 Ma trachyandesite of Del Monte. Rhyolite of Bodie Creek (10.2–9.7 Ma), 

which partly coincides in age with veins, unconformably 

overlies trachyandesite of Del Monte ~5 km west of the 

district. Pliocene and Pleistocene eruptive rocks (3.4–0.1 Ma) 

unconformably overlie trachyandesite of Aurora and Mesozoic 

rocks on the northeast, east, and south sides of the district.

Pre and postmineralization landform aspect and relief 

can be broadly estimated from (1) paleohydrology implied by 

vein textures, dimensions, and abundance, and by wall-rock 

alteration; (2) fluid inclusion microthermometry of vein 

quartz; (3) comparison among several erosional paleosurface 

elevations (contacts) during vein mineralization and present 

elevations of premineralization rocks; and (4) postmineralization fault displacement. Vein textures represent open-space 

filling of tabular conduits that, based on present vein elevations of ~7,200 to 8,400 ft, may have had vertical dimensions 

of >360 m (>1,200 ft). Vertical dimensions of veins, high vein 

density, pervasive alteration between veins, and large water/

rock volumes implied by quartz δ18O and fluid inclusion δD 

values (O’Neil and Silberman, 1974), collectively imply water 

saturation of trachyandesite of Aurora hundreds of meters 

below the paleosurface during mineralization.

Low-salinity fluid inclusion populations in veins are 

interpreted to represent boiling at ~230 °C (and lower 

temperatures; Osborne, 1985; Knudsen and Prenn, 2002), 

which requires a potentiometric surface ~300 m (~1,000 ft) 

above fluid inclusion sample elevations (Haas, 1971). 

Although elevations of some fluid inclusion samples are not 

well documented, the paleopotentiometric surface elevation 

above located Juniata vein samples in the northeastern part 

of the district (present elevation ~7,400 ft; fig. 20), relative to 

present vein elevations, was ~8,400 ft. If the trachyandesite 

of Aurora was water-saturated at the surface, as implied by 

paleohydrologic evidence and Miocene climate, then potentiometric surfaces and erosional paleosurfaces were at the 

same elevation during mineralization. If similar fluids formed 

the Esmeralda-Radical vein, with a present upper elevation 

of ~8,400 ft, then paleosurface elevations in the southwestern 

part of the district would have exceeded 9,000 ft. Present 

maximum elevations of ~11 Ma premineralization volcanic 

rocks (rhyolite of Aurora Creek; trachyandesite of Del Monte; 

trachyandesite of West Brawley Peak), those rocks closest in 

age to vein age (John and others, 2012), vary from ~7,800 to 

9,400 ft. The premineralization trachyandesite of Aurora that 

underlies East Brawley Peak (9,400 ft) was altered to resistant 

quartz ± alunite assemblages at ~12 Ma. If premineralization 

volcanic rocks were not displaced by postmineralization faults, 

and if resistant rocks atop East Brawley Peak were not eroded 

significantly, then paleosurface elevations above veins ranged 

from ~180 m (~ 600 ft) higher than volcanic landforms north 

and west of the district to the approximate elevation of East 

Brawley Peak in the southwest part of the district.

These lines of evidence and assumptions imply that 

Aurora district veins formed in a prominent northeast-trending 

ridge of trachyandesite of Aurora. The ridge extended 

northeast from East Brawley Peak at least 14 km to the New 

Esmeralda veins. Adjacent volcanic landforms to the west 

and northwest were as much as 180 m (~600 ft) lower than 

ridge elevations. To the north, northeast, and east of the ridge, 

terrain sloped downward to the lower elevations in Fletcher 

Valley, which began filling with detritus at ~11 Ma (table 1). 

The upper elevation of gold-bearing sand and gravel beneath 

0.5–0.1 Ma trachyandesite of Aurora Crater (~6,100 ft; 

Nevada Exploration, Inc. 2013) is similar to elevations in 

Fletcher Valley 2 km north of Aurora Crater. These colluvial 

deposits are interpreted to postdate ~10.5 Ma Aurora veins, 

and support relatively low elevation surfaces north of Aurora 

during vein erosion.

Oncoidal thermal vents in altered rhyolite of Aurora 

Creek (fig. 17) ~ 0.5 km northwest of the Aurora town site 

(fig. 20), also support the existence of a ridgelike landform 

during vein formation. These vents, at ~7,600 ft elevation, are 

~120 m (~ 400 ft) above, and presumably coeval with, steamheated 11.1 Ma alunite (SAW11-9; table 1). They are ~60 m 

(~200 ft) below the highest present elevation of rhyolite of 

Aurora Creek. The vents mark a hydrologic paleosurface along 

the northwest margin of the district that existed ~0.6 m.y. 

before vein formation. The Juniata vein system potentiometric 

surface (interpreted as equivalent to the paleosurface; present elevation ~8,400 ft) on the northeast-trending Aurora 

paleoridge was ~240 m (~800 ft) higher than the oncoidal 

thermal vents, and at least 120 m (400 ft) higher than rhyolite 

of Aurora Creek. 

Although the extent and orientation of an Aurora 

paleoridge are constrained by vein distribution and paleohydrology, the proposed relief among 11–10 Ma volcanic 

landforms is less well constrained because of possible 

postmineralization fault displacement and erosion. No fluid 

inclusion microthermometry is available for the EsmeraldaRadical and other Silver Hill veins; these veins may have 

been displaced upward relative to veins to the northeast by 

one or more faults. A west-east lineament, prominent on color 
Spring Peak Sinter 109

air photography and marked by topographic gradients and 

stream course deflections on Silver, Middle, and Last Chance 

Hills (CAP lineament, fig. 20), may correspond to a fault that 

extends west from the district to Beauty Peak. The lineament 

apparently offsets ~2.5 Ma (?) sedimentary rocks of Martinez 

Hill that are exposed north of Martinez Hill and in mine open 

pits from rhyolite of Martinez Hill (Osborne, 1991; Knudsen 

and Prenn, 2002; fig. 20). Down-to-the-north displacement 

along this inferred fault may have offset vein systems on 

Humboldt Hill and Last Chance Hill to elevations lower than 

those of veins on Silver Hill and Middle Hill. Therefore, 

the original vertical extent of veins may have been <360 m 

(<1,200 ft). Right-lateral displacement along this prospective 

fault also may have displaced veins to the northeast, increasing 

areal vein distribution, although other west-east faults in the 

Bodie Hills have left-lateral displacement. A second, prominent west-east air-photo lineament south of Brawley Peaks 

coincides with the stream course south of Spring Peak sinter 

(fig. 48). This inferred fault may mark the southern margin 

of a postmineralization, fault-elevated structural block that 

contains East Brawley Peak and Silver and Middle Hill veins. 

Restoration of displacement on the west-east faults would 

decrease elevation differences between the Aurora paleoridge 

and adjacent premineralization volcanic rocks as well as 

among veins. Accounting for postmineralization erosion could 

further reduce the estimated 11–10 Ma relief at Aurora by tens 

to more than one hundred meters.

The absence of significant placer gold in the district 

suggests that the present level of erosion, or as much as 300 m 

(~1,000 ft) below the paleosurface, approximately coincides 

with the top of high-grade (Au-Ag) vein mineral assemblages. 

Most ore was mined from within ~150 m (~500 ft) below the 

present surface, indicating that the vertical interval of elevated 

Au-Ag grades was ~300 – 450 m (~1,000–1,500 ft) below the 

paleosurface. Alternatively, gold in veins was too fine-grained 

to form mineable placer deposits, and the absence of placer 

has little relationship to depths of ore formation.

Synthesis

Landforms in the Aurora Mining District at 10.5 Ma during Au-Ag vein formation consisted of a northeast-elongate, 

~14 km ridge of 13.1–12.6 Ma trachyandesite of Aurora. 

Based on characteristics of veins and altered wall rocks, and 

relative elevations of contacts, hydrologic paleosurfaces, and 

paleopotentiometric surfaces among trachyandesite of Aurora 

and adjacent volcanic rocks, the ridge stood as much as 

several hundreds of meters above flow-domes of 11.5–11.0 Ma 

rhyolite and trachyandesite to the west, north, and east. Present 

relief, the distribution and elevation of veins, and the absence 

of Au placer deposits, may be partly attributed to antithetical 

displacement along two west-east faults that elevated ancestral 

West and East Brawley Peaks, and caused ~300 m (~1,000 ft) 

of erosion of the trachyandesite paleoridge and veins to the 

tops of high-grade Au-Ag mineral assemblages.

Bodie Mining District

The 8.9–8.1 Ma Au-Ag veins at Bodie are ~1.0 – 0.4 Ma 

younger than dacite of Silver Hill (9.1–8.9 Ma; table 1), the 

host rock of all Bodie veins. Dacite of Silver Hill is overlain 

by slightly younger trachydacite of Potato Peak (9.1–8.7 Ma) 

within 1 km west, north, and northeast of the district (fig. 37). 

Trachydacite of Potato Peak is unaltered, lacks veins, and 

is not known to cover veins. Veins and remnant sinter are 

exposed at the top of Bodie Bluff at ~9,000 ft. Trachydacite 

of Potato Peak exposures near Bodie vary in elevation from 

~8,200 to 10,168 ft, on the summit of Bodie Mountain. 

These elevations are ~800 ft lower and nearly 1,200 ft higher 

than the highest veins on Bodie Bluff. Eureka Valley Tuff 

(9.5–9.3 Ma) in Milk Ranch Canyon, ~1 km north of the town 

of Bodie, underlies dacite of Silver Hill, although the substrate 

is not exposed. Approximately 1 km northeast of Bodie Bluff, 

it overlies 11 Ma trachyandesite of Del Monte, indicating that 

dacite of Silver Hill does not extend very far north of Bodie 

Bluff. At both locations, Eureka Valley Tuff is overlain by 

trachydacite of Potato Peak.

Sinter atop Bodie Bluff formed on, and possibly 

within, a 60 m-thick sequence of volcaniclastic deposits that 

accumulated in a graben between north-northeast-striking, 

antithetically dipping faults (figs. 37, 38). Open tensional 

fractures with opposing dips, flanking and beneath the graben, 

were filled by Incline series and Burgess series veins. Incline 

series veins occur in dacite of Silver Hill on both sides of the 

graben at the same elevation as sinter. If sinter is coeval with 

adjacent veins, then it has been displaced downward relative to 

veins along the graben faults, and Incline series veins formed 

within ~60 m (the thickness of volcaniclastic deposits) of 

the paleosurface marked by the sinter. Alternatively, if sinter 

is younger than Incline series veins, then sinter and grabenfilling volcaniclastic rocks are ~<8.2 Ma, the youngest age of 

adularia in Incline series veins on Bodie Bluff (table 1). This 

latter interpretation requires that Incline series veins on Bodie 

Bluff have been significantly eroded, sinter is temporally 

associated with Silver Hill series veins (~≤8.2 Ma) or a 

younger hydrothermal event, and the graben formed between 

8.2 and <8.1 Ma.

Regardless of relative and absolute ages of veins and 

sinter atop Bodie Bluff, the association of sinter and veins, and 

nearly identical ages of dacite of Silver Hill and trachydacite 

of Potato Peak, require that Potato Peak rocks either (1) thinly 

covered dacite of Silver Hill on Bodie Bluff and were eroded 

prior to sinter deposition, or (2) never covered Bodie Bluff. 

These possible stratigraphic relationships, and the absence of 

dacite of Silver Hill north of the district, imply that present 

relief of the Bodie Bluff landform, considered an intrusion 

by Chesterman and others (1986), ostensibly reflects eruptive 

topology. On a regional scale, the Bodie Mining District 

formed near the northwestern edge of the dacite of Silver Hill 

dome field where the field is partly onlapped by the eastern 

extent of Potato Peak flows. Faulting may have elevated 

Bodie Bluff somewhat along hypothesized bounding faults 
110 Gold-Silver Mining Districts, Alteration Zones, and Paleolandforms in the Miocene Bodie Hills Volcanic Field

(for example, Bodie Creek and Mono faults; fig. 37) but fault 

displacement, other than graben-forming faults, has not been 

quantified. Incline series veins occur on both side of the Tioga 

Fault, and Silver Hill series veins occur on both sides of the 

Mono Fault, suggesting that displacement along these faults 

was small.

Domal uplift has been proposed to explain Bodie Bluff 

relief (Wisser, 1960); episodic doming could account for 

both tensional fractures filled by Incline series veins, and 

the apical graben. However, the attitudes of the Fortuna vein 

and Silver Hill series veins, which consist mostly of replaced 

fault breccia and gouge and lesser open-space filling, are not 

plausibly explained by tensional strain. The Fortuna vein may 

be related to a transtensional structural regime that preceded 

doming, although a relatively abrupt stress field transition is 

required given the small differences in vein ages.

High-grade (Au-Ag) Incline series veins on Standard 

Hill (elev ~8,840 ft) are ~50 m (~160 ft) lower than veins 

and sinter atop Bodie Bluff. Although temporal relationships 

between veins and sinter are imprecisely known, the vertical 

distance between sinter and ore-grade veins in other Tertiary 

vein districts varies considerably (compare Sherlock, 2005; 

Vikre, 2007). If sinter atop Bodie Bluff postdates Incline 

series veins and older Burgess series veins, then vein ore on 

Standard Hill formed >50 m (>165 ft) below the paleosurface. 

Since little ore was mined deeper than ~150 m (~500 ft), 

the vertical range of ore in Incline series and Burgess series 

veins (fig. 38) was >50–200 m (>165–660 ft) below the 

paleosurface. Silver Hill series veins, with the exception of 

veins mined in the Noonday Mine, contained small quantities 

of ore, and archival samples from the Noonday, Addenda, Oro, 

and Red Cloud Mines (fig. 40) were all obtained within 600 ft 

of the surface. If vein samples on the Jupiter, Cupon, and other 

mine dumps on the south slope of Bodie Bluff (fig. 37) are the 

same age as Silver Hill series veins, then ore-grade mineralization in Silver Hill series veins formed at least 200–360 m 

(~ 660–1,200 ft) below the paleosurface (fig. 38). Fluid 

inclusion microthermometry could provide paleoelevational 

control among vein types that would constrain (1) temporal 

and spatial relationships of sinter to veins, (2) paleodepths of 

ore deposition, and (3) quantification of postmineralization 

erosion and fault displacement.

Synthesis

Time-space relations among volcanic stratigraphy, 

vein types, and sinter support the following succession of 

magmatic and hydrothermal events in the Bodie Mining 

District (1) eruption of dacite flows that covered the southern 

part of the district; (2) intrusion of dacite into older dacite 

flows to form Bodie Bluff and other topographically high 

domes; (3) fracture-filling along the southern margin of 

the dacite intrusion at Bodie Bluff by Burgess series veins; 

(4) doming of the dacite intrusion by magmatic inflation, 

creating tensional fractures that were filled by Incline series 

veins; (5) transtensional faulting of dacite flows; some faults 

became Silver Hill series veins; and (6) further doming of 

Bodie Bluff, creating an extensional depression that filled with 

volcaniclastic deposits and sinter. Magmas younger than dacite 

of Silver Hill that could have domed Bodie Bluff prior to, and 

after deposition of Incline series veins are not represented in 

the Bodie Mining District. The nearest volcanic rocks coeval 

with veins are flows and domes of 8.6–8.0 Ma trachyandesite 

of Willow Springs, ~10 km to the west. Igneous rocks that are 

somewhat older than veins include 9.9–8.9 Ma trachyandesite 

of Mount Biedeman, ~10 km (~ 6.3 mi) to the southwest, 

and 9.1–8.7 Ma trachydacite of Potato Peak that borders the 

western side of the district.

Alteration Zones

Variable evidence within alteration zones constrains 

paleosurfaces, paleolandforms, fault displacements, and 

erosion depths. The relationship of a paleosurface in the 

Sawtooth Ridge alteration zone to paleolandforms in the 

Aurora Mining District is described in previous sections of 

this report. Paleolandforms and postalteration evolution of the 

Red Wash-East Walker River, Four Corners, Paramount-Bald 

Peak, Aurora Canyon, Potato Peak, and Cinnabar CanyonUS 395 alteration zones can be reconstructed broadly from 

stratigraphy, geochronology, and characteristics of hydrothermal mineral assemblages.

The Red Wash-East Walker River alteration zone includes 

two temporal markers and hydrothermal mineral assemblages 

that somewhat constrain landforms. The zone formed at 

~13.3 Ma, based on alunite ages, mostly in a volcaniclasticflow sequence within ~15–14 Ma trachyandesite of Masonic 

(table 1). Altered volcaniclastic-flow rocks were partially 

covered at 9.5–9.3 Ma by Eureka Valley Tuff, a remnant of 

which is on the top east side of hill 6,696 (elevation 6,696 ft; 

fig. 14). Pervasive lateral silicification of permeable volcaniclastic strata presumably minimized erosion of these rocks 

during the ~3.7 m.y. of exposure prior to deposition of Eureka 

Valley Tuff. Landforms at 9.3 Ma are envisioned as a series of 

low hills and shallow depressions aligned in a ~20 km westeast zone with north-south dimensions of 2–5 km (Rockwell, 

2010). These low hills were underlain by debris and lavas 

flows that were variably leached and clay-altered by steam 

and other gases that condensed in matrices and discontinuous 

fissures. Depressions among hills consisted of bleached and 

unvegetated flows that were saturated with groundwater acidified by gas condensation. Fissures (fluid conduits) were most 

prevalent in the central part of the zone, where lateral permeability in volcaniclastic strata led to pervasive precipitation of 

silica minerals in leached rocks and fissures, and in subsurface 

water-saturated flows. Adjacent, less-fractured lavas were 

variably altered to clay-mica minerals and lesser pyrite.

Variable permeability in the Red Wash-East Walker River 

alteration zone is reflected by present inverse topography of 

the resistant, flat-topped hills of quartz-alunite-clay-altered 

debris flows that have deflected drainages. The resistant hills 

are flanked by recessively weathering, clay-altered lavas 

partially covered by gravel terraces (fig. 14). The erosional 
Spring Peak Sinter 111

surface represented by the Eureka Valley Tuff contact 

(~ 6,650 ft elevation) on hill 6,696 is several hundreds of feet 

(tens to >100 m) higher than elevations of Eureka Valley 

Tuff (5,600 to 6,200 feet; John and others, 2015) along 

the East Walker River north of the alteration zone. These 

elevation differences (at least 135 m; ~ 450 ft) imply that 

the present elevation of the alteration zone, and incisement 

by the north-trending Masonic Gulch, Sonoma Canyon, and 

Red Wash drainages, occurred since ~9.3 Ma. Dissection of 

fluviolacustrine sediments that overlie the northwestern part 

of the alteration zone, and gravel terraces south of the resistant 

central part of the zone (fig. 14), demonstrate that the Fletcher 

Valley basin was well established by 9.3 Ma.

Paleolandforms in the Paramount-Bald Peak alteration 

zone can be provisionally reconstructed from groups of subaerial terrace and pool sinters in the southwestern, central, and 

northeastern parts of the alteration zone. These sinter groups 

occur among upper strata of the ~9.7–9.3 Ma sedimentary 

rocks and tuff of Paramount (Tpst; fig. 27), which is constrained in age by overlying 9.3 Ma Eureka Valley Tuff and by 

blocks of 9.7 Ma rhyolite of Bald Peak (John and others, 2012) 

within the strata. In the southwestern part of the alteration 

zone, sinters on Paramount Mine hill and hills to the southwest 

and southeast (Paramount Mine area sinter group; fig. 28) 

have present elevations of 9,040–8,400 ft. The sinter terrace 

at Atastra Creek, ~4.2 km southeast of Paramount Mine hill, 

is at 8,000 ft. Sinters near Hilton Springs in the central part of 

the alteration zone (Hilton Spring sinters; fig. 28) are at ~7,800 

ft. The group of sinters ~2.5 km north-northeast of Bald Peak 

have present elevations of ~7,200–7,080 ft. Locally, as on 

Paramount Mine hill, sinter terraces protruded from slopes and 

do not necessarily represent maximum local paleoelevations. 

Furthermore, the elevationally tiered sinter groups may not 

be coeval or represent common paleoelevations. However, 

the groups formed within several hundreds of thousands of 

years, they occur at or near the top of sedimentary rocks and 

tuff of Paramount, and they likely represent a small range in 

paleoelevation.

Present elevation differences among sinter groups may 

partially reflect downward displacement to the northeast along 

faults. Several mapped faults offset sinter groups (fig. 27) but 

fault displacement may not entirely account for the nearly 

2,000 ft of elevation range among sinter groups. Alternatively, 

elevation differences may reflect magmatic inflation centered 

on Potato Peak, ~5.5 km south-southwest of Paramount Mine 

hill, during voluminous Potato Peak trachydacite volcanism at 

~9 Ma. The ~1,500 ft elevation difference between the nearly 

simultaneously formed Potato Peak and Aurora Canyon alteration zones (10.8 and 10.7 Ma, respectively; table 1), ~1.2 km 

and ~4.2 km northwest, respectively, of Potato Peak, also is 

not clearly related to fault displacement. Therefore, elevation 

differences among sinter groups and coeval altered rocks on 

the north and northwest sides of Potato Peak are provisionally 

attributed both to fault displacement and landform inflation 

associated with Potato Peak magmatism. If this interpretation 

is correct, then much of the present relief of the southern part 

of the Bodie Hills volcanic field was attained by ~9 Ma.

The Four Corners alteration zone contains small pockets 

of chemical and clastic sediments that fill depressions in 

silicified breccia (fig. 20) and resemble similar deposits at the 

Sarita Mine. Although undated, this small alteration zone is on 

the range divide at an elevation of 8,600 ft and its preservation 

supports a young age relative to the ages of larger alteration 

zones at lower elevations, which are >8 Ma. Exposures in 

the Four Corners alteration zone apparently have not been 

modified significantly by erosion or fault displacement.

In the Cinnabar Canyon-US 395 alteration zone, a 

>8 Ma volcaniclastic-flow sequence was altered to quartz, 

alunite, kaolinite, and pyrite at 8.8–8.2 Ma (table 1). The 

altered sequence strata are ~ 60 m thick where they overlie 

pre-Tertiary rocks along Clearwater Creek near the mouth 

of Cinnabar Canyon, but could be somewhat thicker to the 

north and northwest (possibly 400 ft in the Cinnabar Canyon 

sulfur resource; fig. 36). Trachyandesite of Willow Springs 

(~8.6–8.0 Ma;) overlies altered sequence strata in numerous 

places including Cinnabar Canyon (clay-cut hill) and Hot 

Springs Canyon (fig. 34). Although sequence strata are 

correlated with 9.9–8.9 Ma sedimentary rocks and debris 

flows of Mount Biedeman, the slightly younger and similar 

age ranges of alunite in altered sequence strata (8.8–8.2 Ma; 

table 1) and unaltered trachyandesite of Willow Springs 

indicate that exposed sequence surfaces represent a marginally 

eroded paleosurface. Landforms prevailing during this time 

resembled those of the Red Wash-East Walker River alteration 

zone, which consisted of lowlands and depressions of soggy, 

steaming ground, amidst low hills of variably leached and 

silicified sequence strata. Cyclic leaching and silicification 

in parts of the alteration zone reflect a hydrologic regime of 

fluctuating groundwater saturation levels into which gases 

derived from cooling magma(s) condensed and oxidized. The 

Cinnabar Canyon S° resource formed in this dynamic environment subjacent to silicified volcaniclastic strata that underlie 

Cinnabar Hill (Vikre and Henry, 2011). Similar to the Red 

Wash-East Walker River alteration zone, significant erosion 

of the Cinnabar Canyon alteration zone was confined to larger 

drainages (Cinnabar Canyon; Hot Springs Canyon; fig. 34).

Evolution of Landforms in the Bodie Hills Volcanic Field, 

15–3.9 Ma

Evolution of landforms can be broadly reconstructed 

from several lines of evidence variously described in previous 

sections of this report (1) paleotopography of the Aldrich 

Station flora north of the Bodie Hills and provisional correlation of the flora with older sedimentary deposits of Fletcher 

Valley; (2) paleolandforms and paleosurfaces in mining 

districts and alteration zones; (3) distribution and elevations 

of 9.5–9.3 Ma Eureka Valley Tuff; and (4) distribution, 

elevations, and ages of volcanoes and associated sedimentary 

rocks that are older and younger than Eureka Valley Tuff.

Faults demonstrably older than Eureka Valley Tuff are those 

filled with 13.3–10.5 Ma veins and altered breccias in the 

Masonic and Aurora Mining Districts. Common hangingwall 
112 Gold-Silver Mining Districts, Alteration Zones, and Paleolandforms in the Miocene Bodie Hills Volcanic Field

and footwall strata in these districts preclude estimation of 

displacement along these structures. Veins and faults in the 

Bodie Mining District, which are younger than Eureka Valley 

Tuff, have measured and suspected displacements of tens of 

meters or less. Most mapped or proposed faults that offset 

Eureka Valley Tuff also have common wall rocks. Estimates 

of displacement, tens of meters, are derived from elevations of 

contacts of Eureka Valley Tuff and underlying strata. Because 

of the structural and stratigraphic significance of Eureka 

Valley Tuff, which is distributed throughout much of the Bodie 

Hills, landform evolution has been reconstructed here relative 

to this marker.

Northwestern Bodie Hills, 15–9.3 Ma

Based on paleosurfaces and paleolandforms in the 

Masonic Mining District and Red Wash-East Walker River 

alteration zone, the northwestern part of the Bodie Hills volcanic field at 12.9 Ma consisted of a broad upland (~500 km2

) 

of 15–12.9 Ma trachyandesite flows, volcaniclastic strata, 

and domes (Masonic volcanic center; fig. 52A). The domes 

(15–14, 13.5–13.4, and 12.9 Ma), included a prominent edifice 

south of Masonic Mountain, and protrusions of Mesozoic 

granitic and metamorphic rocks (ancestral Masonic Mountain) 

punctuated by relatively subdued upland topography. Basin-fill 

deposits, which contain 11–10 Ma tephra, partly cover strata 

of the Masonic volcanic center (fig. 52B), indicating that a 

depression (ancestral Fletcher Valley) existed north and northeast of Masonic Mountain by 11 Ma. By 9.5 Ma, numerous 

water courses incised the upland, some of which drained north 

to northeast toward ancestral Fletcher Valley. Paleodrainages, 

including the present East Walker River, subparallel water 

courses, and depressions west, southwest, and northwest of 

ancestral Masonic Mountain, are now marked by relatively 

thick and contiguous deposits of 9.5–9.3 Ma Eureka Valley 

Tuff (fig. 52C). The lowest elevation exposure of Eureka 

Valley Tuff, ~5,600 ft along the East Walker River north of the 

Masonic volcanic center, implies that detritus in the western 

part of Fletcher Valley was derived from uplands in the vicinity of Masonic Mountain. Present elevations of domes and 

Masonic Mountain relative to the highest elevation of Eureka 

Valley Tuff suggest that relief in the northwestern Bodie Hills 

at 9.5 Ma was tens to hundreds of meters (hundreds of feet), 

and probably ≤ 20 percent of present relief.

Eastern Bodie Hills, 13–9.5 Ma

In the eastern part of the Bodie Hills volcanic field, 

the prominent paleolandform in the Aurora Mining District 

and East Brawley Peak alteration zone at ~10.5 Ma was an 

elongate ridge of 13.1–12.6 Ma trachyandesite of Aurora 

(Aurora volcanic center; ~ 130 km2

; 51 mi2; fig. 52B). The 

ridge extended ~14 km northeast from ancestral East Brawley 

Peak, and was flanked to the north and west by relatively 

small-volume trachyandesite and rhyolite flow-dome fields 

(~≤ 50 km2) at similar to lower elevations. No Eureka Valley 

Tuff exists near Aurora to mark drainages and depressions 

that developed by 9.5 Ma. Basin-fill deposits that overlie 

13–11 Ma eruptive rocks north of Aurora, coupled with the 

11.1 Ma age of unwelded tuff in Fletcher Valley sedimentary 

strata (table 1), confirm that Fletcher Valley bordered the 

volcanic field to the north by 11 Ma. Gold-bearing sand and 

gravel deposits that overlie altered lacustrine strata beneath 

Holocene trachyandesite of Aurora Crater (Nevada Exploration Inc., 2013) also support low elevations north of the 

Aurora Mining District by 10.5 Ma. Relative to the basin-fill 

deposits, relief in the eastern Bodie Hills at 9.5 Ma was tens to 

hundreds of meters (hundreds of feet), probably ≤ 25 percent 

of present relief.

Central and Southern Bodie Hills, 15–9.5 Ma

From ~15 to 12 Ma, Mesozoic rocks were apparently 

exposed between the Masonic and Aurora volcanic centers 

because only small-volume (~13 km2) trachydacite of Rough 

Creek was erupted between those centers. From ~ 11 to 10 Ma, 

numerous large- (~30–50 km2) to small-volume (< 20 km2) 

flows and domes of trachyandesite, rhyolite, and trachydacite 

erupted between, north, and south of the Masonic and Aurora 

centers. Several large-volume flow sequences and lava domes 

partly covered the Masonic and Aurora centers, and contributed detritus and tuff to a central depression, the 9.7–9.3 Ma 

Paramount basin (fig. 52B). These permeable volcaniclastic 

strata were pervasively altered (Paramount-Bald Peak alteration zone) by artesian hydrothermal fluids that built numerous 

sinter terraces (fig. 27), several of which are associated with 

the Hg deposit at the Paramount Mine (fig. 28). Fluid circulation may have been driven by a concealed intrusion spatially 

related to ~9.7 Ma Bald Peak rhyolite.

Eureka Valley Tuff, 9.5–9.3 Ma

By 9.3 Ma, drainages and depressions among 15–10 Ma 

eruptive rocks and Mesozoic rocks in the central and western 

parts of the Bodie Hills volcanic field had been at least partly 

filled with ash flows and reworked tephra deposits of the 

externally sourced Eureka Valley Tuff (fig. 52C). Semialigned 

remnants and elongate exposures of Eureka Valley Tuff 

mark paleochannels, several of which are subparallel to the 

East Walker River. Present elevations of Eureka Valley Tuff 

exposures, contiguous with large- and small-volume volcanic 

centers, indicate relief of tens of meters (tens to hundreds of 

feet) at the time of Eureka Valley Tuff eruption.

Southeastern Bodie Hills, 10–8 Ma

Four large-volume, coalesced volcanic centers 

(~150–70 km2) were emplaced in the southern Bodie Hills 

at 10–8 Ma (fig. 52D). From 10–9 Ma, trachydacite and 

associated volcaniclastic deposits formed a large flow-dome 

complex centered on Potato Peak while trachyandesite lava 

and associated debris flows were erupted from the Mount 

Biedeman stratovolcano, in part simultaneously with eruption 

of Eureka Valley Tuff. Rocks from these volcanic centers 
Spring Peak Sinter 113

partly covered strata of the Masonic volcanic center, and 

11–10 Ma large- and small-volume volcanoes. From 9 to 

8 Ma, extensive flow-dome complexes were emplaced east 

(dacite of Silver Hill) and west (trachyandesite of Willow 

Springs) of Potato Peak. These volcanic edifices were partly 

altered by hydrothermal systems that formed Bodie district 

Au-Ag veins (8.5–8.1 Ma), the extensive Cinnabar Canyon 

alteration zone (8.8–8.2 Ma; fig. 52D), and the S° resource in 

the Cinnabar Canyon alteration zone.

Bodie Hills Landforms, 8–3.9 Ma

At 8 Ma, landforms in the central and southern parts of 

the Bodie Hills volcanic field were dominated by the 10–8 Ma 

volcanoes centered on Potato Peak and Mount Biedeman, 

and by adjacent, small-volume volcanoes. Since 8 Ma, only 

a few small-volume landforms (~6.2–5.4 Ma rhyolite and 

dacite flow-domes; John and others, 2012) have been added 

to the Bodie Hills volcanic field. Since 8 Ma, the 10–8 Ma 

volcanoes have been marginally eroded, and vent-filling 

plugs of trachydacite on Potato Peak (10,237 ft) and Mount 

Biedeman (8,962 ft) are among the highest elevations in the 

Bodie Hills. At ~8 Ma, the elevation difference between the 

top of the Potato Peak volcano and Eureka Valley Tuff beneath 

trachydacite of Potato Peak lava flows in the Bodie Mining 

District (~8,500 ft, fig. 37), was at least 1,737 ft, discounting 

unquantified post-8 Ma erosion of ancestral Potato Peak. The 

difference in elevation between the Potato Peak volcano and 

Fletcher Valley at 8 Ma, assuming a common paleoelevation 

for Eureka Valley Tuff at Bodie, along the East Walker River, 

and in Fletcher Valley, would also have been 1,737 ft (or 

more). The present elevation difference between Potato Peak, 

East Walker River, and Fletcher Valley, ~ 4,600 – 4,200 ft, 

suggests that most prevailing relief (>60 percent) in the Bodie 

Hills has developed since 8 Ma. Given the absence of significant faults in the southern part of the volcanic field (John and 

others, 2012), this relief largely reflects magmatic inflation 

during growth of 10–8 Ma volcanoes in the southern part of 

the volcanic field.

Small increments of relief have been added to northwestern and eastern parts of the field by displacement along 

west-east, and north-northeast-striking normal faults that have 

been mapped or are expressed by lineaments on color air photographs (fig. 52D), although stratigraphic displacement along 

lineaments is not always evident. A north-northwest-trending 

fault that apparently borders the east side of Bridgeport Valley 

also contributed to relief of the volcanic field. The west-east 

and northeast-striking faults have displaced trachyandesite 

north of Masonic (fig. 14) and at Aurora (fig. 20), mostly 

by down-to-the-north movement of tens of meters. North 

of Masonic, displacement along west-east faults perched 

fluviolacustrine deposits relative to Fletcher Valley basin-fill. 

Elevations of sinter groups in the Paramount basin differ by 

tens to hundreds of meters (<2,000 ft; fig. 27). These elevation 

differences reflect both post-9.3 Ma, down-to-the-east displacement along north-striking faults (fig. 52D), and magmatic 

inflation during construction of the 9 Ma Potato Peak volcano. 

The volcanic centers at Masonic and Aurora also may have 

acquired additional relief by magmatic inflation during construction of the 10–8 Ma Mount Biedeman stratovolcano, and 

by flow-dome complex development in the southern part of 

the volcanic field. Distribution of Pliocene-Holocene volcanic 

rocks of the Aurora volcanic field in the eastern Bodie Hills 

does not appear to have been significantly modified by faults, 

although these rocks are cut by numerous northeast-striking 

faults in the eastern and southeastern parts of the Bodie Hills 

(John and others, 2015). Other landform modifications since 

8 Ma include incision by drainages that mostly originated in 

the trachyandesite uplands at Masonic, Aurora, Potato Peak, 

and Mount Biedeman.

Relief and Absolute Paleoelevations

Pre-Eureka Valley Tuff relief in the 15–10 Ma Masonic 

and Aurora volcanic centers is estimated at tens to hundreds 

of meters (tens to >1,000 ft). The highest and lowest remnants 

of Eureka Valley Tuff, on Potato Peak (~9,150 ft) and near the 

confluence of the East Walker River and Red Wash (~5,600 ft), 

respectively, differ in elevation by ~3,550 ft. Potato Peak, 

which formed after emplacement of Eureka Valley Tuff, is 

at least 4,600 ft higher than the lowest Eureka Valley Tuff, 

and ~ 4,200 ft higher than Fletcher Valley (present elevation 

~ 6,100 – 6,000 ft). The smaller elevation difference between 

Potato Peak and Fletcher Valley, ~ 4,200 ft, apparently reflects 

~ 400 ft of basin fill added since 9.3 Ma. This estimate is supported by ~600 ft (~180 m) of gold-bearing sand and gravel 

deposits in drill holes beneath Holocene trachyandesite of 

Aurora Crater (Nevada Exploration Inc., 2013). The colluvial 

deposits overlie altered lacustrine strata that may be the same 

age as, or older than, ~10.5 Ma Aurora district veins ~4 km 

to the south. Therefore, relief within the Bodie Hills volcanic 

field, created by volcano construction, magmatic inflation, 

fault displacement, and erosion since 15 Ma, totaled at least 

4,200 ft and likely exceeded 4,600 ft.

Absolute elevations during landform evolution in the 

Bodie Hills volcanic field can be estimated from paleoelevations of the 11 Ma Aldrich Station flora. If elevations in the 

Masonic and Aurora volcanic centers at 11 Ma were 2,500–

2,000 ft (Axelrod, 1956), then elevations have increased by 

at least 6,100 ft (~1,850 m) in the northwestern and eastern 

parts of the volcanic field (present elevation of Eureka Valley 

Tuff remnants on Masonic Mountain are 8,600 and 8,775 ft), 

and elevations have been increased by ~8,000 ft (~2,425 m) to 

account for the present elevation of Potato Peak. If paleoelevations of Aldrich Station flora were 4,300–6,900 ft (Wolfe, 

1995; Wolfe and others, 1997), then elevations at Masonic 

increased by ~1,700–4,300 ft (~515–1,300 m), and at Potato 

Peak by ~3,300–5,900 ft (~1,000–1,790 m) since 11 Ma. If 

~11 Ma sediments containing fossils in the northern Bodie 

Hills are stratigraphically equivalent to Aldrich Station flora, 

then the Bodie Hills have been elevated an additional 1,700 ft 

(515 m), or ~3,400–7,600 ft (~1,030–2,300 m), since 11 Ma. 
114 Gold-Silver Mining Districts, Alteration Zones, and Paleolandforms in the Miocene Bodie Hills Volcanic Field

Therefore, based on present elevations of Eureka Valley 

Tuff remnants, Potato Peak, Fletcher Valley, and fossilbearing sediments, the higher paleoelevation range estimate 

(4,300–6,900 ft) for Aldrich Station flora is more consistent 

with relief developed in the Bodie Hills since 9.3 Ma (at least 

4,200–4,600 ft; ~1,279–1,400 m). Relative to Aldrich Station 

flora, elevations in the northwestern part of the Bodie Hills 

volcanic field at 9.3 Ma were ~4,300–6,900 ft, and possibly 

hundreds to more than 1,000 feet higher in the eastern part 

of the volcanic field. At 8 Ma, after eruption of large-volume 

stratovolcanoes and flow-dome complexes in the southern 

part of the Bodie Hills volcanic field, maximum elevations 

exceeded 8,500 ft, and could have approached 10,000 ft 

(ancestral Potato Peak).

Summary

Significant conclusions of this investigation are summarized as follows:

1. The 15–6 Ma Bodie Hills volcanic field consists of 

coalescing stratovolcanoes and lava domes that were 

assembled on an irregular pre-Tertiary surface of Paleozoic and Mesozoic metamorphic and Cretaceous granitic 

rocks. The field is part of a subduction-related alignment 

of predominantly andesitic eruptive rocks that parallels 

the western margin of North America. Volcanic rocks are 

predominantly trachyandesite, lesser trachydacite, and 

subordinate rhyolite that commonly contain phenocrysts 

of plagioclase, pyroxene, hornblende, biotite, sanidine, 

and quartz, and have compositions similar to subduction 

magmas elsewhere. Three Au-Ag-Cu mining districts 

and nine aerially extensive alteration zones, one of 

which contains a significant sulfur (S°) resource, occur 

mostly in the volcanic rocks. 

2. The Masonic Au-Ag-Cu Mining District (production of 

0.056 Moz Au, 0.04 Moz Ag, and minor Cu) includes 

two styles of mineralization, ~13 Ma fault breccia and 

vein deposits, and ~13.3 Ma clastic and hydrothermal 

sedimentary deposits. Deposits occur in ~15–14 Ma trachyandesite of Masonic and pre-Tertiary rocks, and are 

temporally associated with ~13.5 and ~13 Ma trachyandesite and andesite domes. Both types consist of quartz, 

alunite, lesser kaolinite, pyrophyllite and sericite, pyrite, 

enargite, Au-rich electrum, and numerous Cu-As-Sb-FeBi-Au-Ag-S-Se-Te minerals.

3. The Aurora Au-Ag Mining District (estimated production of 1.91 Moz Au and 21 Moz Ag production) 

includes ~10.5 Ma layered quartz-adularia-sericiteelectrum-sulfide veins in ~13.1–12.6 Ma trachyandesite 

of Aurora that is altered to sericite, K-feldspar, pyrite, 

chlorite, albite, calcite, and montmorillonite.

4. The Bodie Au-Ag Mining District (production of 

1.46 Moz Au and 7.3 Moz Ag) includes at least three, 

~8.9–8.1 Ma quartz-adularia-sericite-sulfide-telluride 

vein series that are distinguished by textures, ages, and 

mineralogy. The vein series occur in ~9 Ma dacite of 

Silver Hill.

5. Alteration zones include quartz-alunite-pyrite(iron 

oxide)-dominant assemblages that vary in age from 

~13.3 to 8.2 Ma, and quartz-kaolinite-montmorillonitedominant assemblages that are ~9.7–9.3 Ma and include 

sinter. The alteration zones occur in rocks that are the 

same age to ~2 m.y. older than hydrothermal minerals. 

Small amounts of Hg were recovered from deposits in 

several alteration zones (Potato Peak; Paramount-Bald 

Peak; Cinnabar Canyon-US 395; Spring Peak), a sulfur 

resource occurs in the Cinnabar Canyon-US 395 alteration zone.

6. The evolution of landforms during the assembly, alteration, and erosion of the volcanic field, based on volcanic 

stratigraphy, geochronology, and hydrothermal mineral assemblages, began with construction of the large 

15–13 Ma Masonic and 13–12 Ma Aurora volcanic 

centers that mark the northwestern and northeastern parts 

of the field. Smaller volcanoes erupted at ~11–10 Ma in, 

between, and south of these centers as erosional detritus accumulated north of the field in Fletcher Valley. 

Distally sourced, 9.7–9.3 Ma Eureka Valley Tuff filled 

drainages and depressions among older volcanoes and 

was partly covered by nearly synchronous eruptives during construction of four large 10–8 Ma volcanoes, which 

comprise the southern part of the field. The scarcity of 

significant internal fault displacement, distribution of 

Eureka Valley Tuff, and elevation estimates derived from 

floras, suggest that the Bodie Hills volcanic field attained 

present elevations mostly through volcano construction 

and magmatic inflation, and that maximum paleoelevations (>8,500 ft) at the end of large volume eruptions at 

~8 Ma are similar to present elevations.

Acknowledgments

Numerous individuals and institutions provided maps, 

reports, specimens, and site access that greatly enhanced 

description of mining districts and alteration zones, and 

characterization of ores. Unpublished mine maps, geologic 

maps, and reports from the Masonic, Aurora, and Bodie 

Mining Districts by Page Blakemore, Robert Hatch, C. Hogge, 

Richard Kern, Peter Knudsen, Edmond Lawrence, N. Lehman, 

Anthony Payne, Neil Prenn, William Rehrig, David Shaddrick, 

Miles Silberman, Amer Smailbogevic, Scott Tregaskis, and 

Robert Wilson significantly supplemented published accounts. 

Archival mining district files maintained on-line by the 
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Nevada Bureau of Mines and Geology were the source of 

some of these unpublished reports and maps. Simon Poulson 

provided some sulfur isotope analyses, Larry Snee provided 

several 40Ar/39Ar dates, and Jim Rytuba provided some 

geochemical analyses. LA ICP-MS traverses of sinter and 

vein sections were done under the guidance of Alan Koenig in 

his laboratory. Discussions and field tours of several districts 

and alteration zones with Ken Brook, Tony Eng, and Greg 

Kouzma led to productive sharing of geologic information 

and perspectives. Rachel Dolbier and D.D. LaPointe of the 

Keck Museum, University of Nevada Reno (Reno, Nevada), 

and Darci Moore of the California State Mining and Mineral 

Museum (Mariposa, California) graciously loaned archival 

specimens from the Aurora and Bodie Mining Districts. Mark 

Langner, Thomas Gunther, Joshua Heitzmann, and Tamara 

Sasaki of the Department of Parks and Recreation, State of 

California, provided ready access to Bodie State Historic Park 

and permission to collect samples. Thorough reviews of a draft 

manuscript by John Slack and Jeff Mauk led to many improvements in the final version.

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Appendixes

1-1. Minor element concentrations in rock samples from the Masonic Mining District.

1-2. Minor element concentrations in rock samples from the Red Wash-East Walker River alteration zone.

1-3. Minor element concentrations in rock samples from the East Brawley Peak alteration zone.

1-4. Minor element concentrations in rock samples from the Sawtooth Ridge alteration zone.

1-5. Minor element concentrations in rock samples from the Aurora Canyon alteration zone.

1-6. Minor element concentrations in rock samples from the Potato Peak alteration zone.

1-7. Minor element concentrations in rock samples from the Aurora Mining District.

1-8. Minor element concentrations in rock samples from the Four Corners alteration zone.

1-9. Minor element concentrations in rock samples from the Paramount-Bald Peak 

alteration zone.

1-10. Minor element concentrations in rock samples from the Cinnabar Canyon-US 395 alteration zone.

1-11. Minor element concentrations in rock samples from the Bodie Mining District.

1-12. Minor element concentrations in rock samples of Spring Peak sinter.
Table 1-1. Minor element concentrations in rock samples from the Masonic Mining District. [—, no data] Sample number Description Latitude Longitude Au ppm Hg ppm Al % Ca% Fe% K% Mg% Na% 

2007–12 samples MAS09-3 Quartz-enargite matrix breccia; upper Pittsburgh-Liberty Mine dump 38.35711 –119.11837 27.6 14.7 0.22 0.03 0.28 0.03 0.01 <0

MAS09-3A Quartz-enargite matrix breccia; upper Pittsburgh-Liberty Mine dump 38.35744 –119.12021 53.9 70 0.39 0.14 1.24 0.03 0.01 0

07-BA-39A Open cut dump, Sarita Mine 38.36008821 –119.1258767 25.2 4.92 1.88 0.03 3.51 0.34 <0.01 0

07-BA-39B Open cut dump, Sarita Mine 38.36008821 –119.1258767 9.21 1.76 3.22 0.06 1.71 0.66 <0.01 0

12-BA-21A Sarita Mine, banded sulfide sediments 38.36093606 –119.1260979 4.57 85.7 0.35 0.19 1.5 0.05 0.04 0

12-BA-21B Sarita Mine, banded sulfide sediments 38.36093606 –119.1260979 82.3 27 0.18 0.01 0.66 0.02 <0.01 <0

07-BA-35 Success Mine dump 38.34030246 –119.1558718 0.209 14.3 3.22 0.07 1.07 0.37 <0.01 0

07-BA-35B Pyrite-rich alteration, Success Mine dump 38.34030246 –119.1558718 0.246 8.02 5.87 0.02 0.55 2.73 <0.01 007-BA-36 Chemung Mine dump 38.3500062 –119.1470806 0.059 8.65 3.43 0.04 1.09 1.52 <0.01 0

07-BA-37 Bladed alunite in vuggy silica, Chemung Mine 38.3500062 –119.1470806 0.164 20.1 2.91 0.03 0.76 0.47 0.01 0

07-BA-40 Coarse alunite, Pittsburgh-Liberty Mine dump 38.36546144 –119.1160664 0.052 0.26 9.77 0.02 0.27 2.73 <0.01 007-BA-41 Quartz-pyrite alteration, Pittsburgh-Liberty Mine dump 38.36546144 –119.1160664 0.048 2.14 6.01 0.02 2.52 2.78 <0.01 0

07MS5 Breccia, Chemung Mine 38.34973 –119.14801 2.55 22.9 0.75 0.06 0.55 0.05 0.03 007MS3 Vuggy silica breccia, Chemung Mine 38.3499 –119.14761 0.241 22.8 0.39 0.06 0.35 0.04 <0.01 <0

07MS2 Tan and black chalcedony, Chemung Mine 38.34945 –119.14761 0.221 3.51 2.99 0.02 0.91 0.17 <0.01 0

MAS11-11 Gray-black multigenerational sulfidic breccia 38.34021 –119.15672 0.178 1.59 3.49 0.08 1.8 1.06 <0.01 0

MAS11-11A Brecciated sedimentary rocks with banded quartz-sulfide-alunite matrix 38.356679 –119.11899 1.96 15.7 7.73 0.09 0.64 3.18 <0.01 0

Au ppm Hg ppm 

1988 samples MD88-1 Chemung Mine dump 38.34955 –119.14959 6.36 28.7 

MD88-1C Chemung Mine dump 38.34955 –119.14959 2.92 31.9 

MD88-3C Success Mine dump 38.34019 –119.15659 0.34 18.7 MD88-4 Sarita Mine dump 38.36052 –119.12716 6.15 27.6 MD88-4A Sarita Mine dump 38.36052 –119.12716 11.56 43.1 

MD88-4C Sarita Mine dump 38.36052 –119.12716 11.66 16.3 

MD88-5A Masonic mill dump 38.36705 –119.11901 40.09 17.5 

MD88-5B Masonic mill dump 38.36705 –119.11901 36.79 31.9 
Table 1-1. Minor element concentrations in rock samples from the Masonic Mining District.—Continued[—, no data]

Sample 

number

As

ppm

Ba

ppm

Be

ppm

Bi

ppm

Cd

ppm

Ce

ppm

Co

ppm

Cr

ppm

Cs

ppm

Cu

ppm

Ga

ppm

In

ppm

La

ppm

Li

ppm

2007–12 samples

MAS09-3 1,040 1,530 1.1 1,050 0.6 5.18 0.3 3 <5 3,140 3.49 0.35 2.8 2 

MAS09-3A >10,000 242 <0.1 4,310 0.7 5.54 0.6 2 <5 >50,000 3.68 0.49 3.5 3 

07-BA-39A 145 478 0.6 189 <0.1 8.53 6 7 <5 179 11.8 0.08 4.4 16 

07-BA-39B 146 548 0.2 57.1 <0.1 12.8 0.4 8 <5 72.8 22.6 0.17 7 12 

12-BA-21A 549 652 0.7 2,780 0.5 7.05 3.3 6 <5 1,310 4.83 0.27 3.8 7 

12-BA-21B 315 562 0.8 2,610 0.5 4.31 0.6 5 <5 325 3.91 0.17 2.3 4 

07-BA-35 256 1,230 0.4 0.06 0.3 35.1 6.1 8 <5 25.1 10.4 0.07 18 18 

07-BA-35B 81 547 0.2 0.1 0.2 27.5 2.4 9 <5 15.9 13.7 0.02 16.1 1 

07-BA-36 50 2,750 0.4 0.56 <0.1 30.4 0.8 15 <5 16.9 29 0.1 16.7 4 

07-BA-37 40 1,940 0.4 1.25 <0.1 11.5 0.8 7 <5 11.2 8.98 <0.02 6.7 7 

07-BA-40 12 535 0.3 0.92 <0.1 9.74 0.3 2 <5 4.8 20.9 0.31 4.9 11 

07-BA-41 66 693 <0.1 7.06 0.3 12.1 5.5 8 <5 49.5 53.2 0.46 7.7 3 

07MS5 59 1,020 0.6 15.8 <0.1 18 0.6 5 <5 15.8 2.18 0.04 8.9 4 

07MS3 35 6,120 0.3 24.7 <0.1 17.8 0.7 5 <5 7.9 1.28 0.02 10 2 

07MS2 67 244 0.4 0.06 <0.1 22.5 4.2 6 <5 11 11 <0.02 10.6 4 

MAS11-11 46 209 0.2 13.3 <0.1 32.9 3.3 7 <5 68.8 31.8 0.06 17.4 5 

MAS11-11A 788 97 0.3 4,340 0.3 49.8 0.3 15 <5 191 66.5 0.31 26 3 

As

ppm

Bi

ppm

Cu

ppm

1988 samples

MD88-1 592 1 1,270MD88-1C 588 24.8 2,700MD88-3C 526 0.3 56MD88-4 680 0.034 163MD88-4A 3,107 0.093 2,900MD88-4C 174 916 600MD88-5A 265 2,900 3,500MD88-5B 370 3,110 1,230
Table 1-1. Minor element concentrations in rock samples from the Masonic Mining District.—Continued [—, no data] Sample number Ni ppm Pppm Pb ppm Rb ppm Sb ppm Sc ppm Se ppm Sn ppm Sr ppm Te ppm Th ppm Tl ppm Uppm Vppm 

2007–12 samples MAS09-3 <0.5 60 92.1 0.8 1,120 2.6 — 26.9 106 >500 3.5 0.5 2.8 13 

MAS09-3A <0.5 490 149 0.8 >10,000 1.2 — 461 429 >500 1.1 4.2 3.1 8 

07-BA-39A 4.9 270 132 1.4 99.9 1.3 17.5 0.9 162 296 1.2 0.2 1 46 

07-BA-39B 1.3 630 216 2.2 114 2.5 5.9 0.3 625 166 1.7 0.2 1.5 85 

12-BA-21A 8.5 100 97.6 1.4 479 2.3 198 1.9 168 >500 4.3 1.1 2.9 20 

12-BA-21B 0.7 <50 115 0.9 857 3.6 43.2 4.7 32.6 >500 5.6 0.4 2.8 21 

07-BA-35 6.4 1,150 93.3 2.2 71.9 4.4 5.3 0.6 1,080 3.1 6.4 2.9 6.6 45 

07-BA-35B 3.2 300 25 2.7 51.3 4.4 8.1 0.9 304 2.1 6.2 10.4 3.2 66 

07-BA-36 2.7 790 278 1.9 45 5.5 2.5 1 592 2.6 5 0.3 10.3 132 

07-BA-37 1.7 310 61.6 2.3 11.3 1.9 3.4 1 258 2.2 2.6 0.2 2.7 45 

07-BA-40 2.2 210 131 3.6 5.57 4.2 0.8 0.8 219 1.7 12 0.1 1.7 39 

07-BA-41 13.7 960 1,640 1.8 76.3 3 17.6 0.8 641 4.8 4.7 1.5 0.9 113 

07MS5 1.7 370 80.7 3.6 97.9 2.8 — 1.8 306 200 3.1 0.5 6.6 12 

07MS3 1.7 350 116 2.3 96.7 2.5 — 1.2 335 25 4.2 0.4 8.6 13 

07MS2 2.9 310 14.2 2 63.4 1.9 — 0.8 303 3.7 3.5 1.2 1.7 42 

MAS11-11 3.9 1,800 308 4.5 42.9 4.3 28.9 1.6 2,850 10.1 4.1 0.2 7.5 77 

MAS11-11A <0.5 2,000 1,070 3 3,180 6.3 43.9 74.3 1,520 287 5 0.6 2.1 143 

Sb ppm Sn ppm Te ppm 1988 samples MD88-1 3,500 10 0.8 MD88-1C 780 16 300 MD88-3C 20 10 2.5 MD88-4 4,600 57 3,220 MD88-4A 1,710 3 483 MD88-4C 480 3 547

MD88-5A 119 48 346MD88-5B 550 52 617
Table 1-2. Minor element concentrations in rock samples from the Red Wash-East Walker River alteration zone.[Fe, iron; FeOx, iron oxide; —, no data]

Sample 

number Description Latitude Longitude Au ppm Hg ppm Al % Ca% Fe% K% Mg% Na% 

09-E02 — — — — 1.42 4 — — 0.03 0.01 0.02 

09-E04 — — — — 2.7 4.86 — — 0.05 0.02 0.02 

09-E09 Silicified with quartz veins — — <0.005 0.35 7.15 0.23 4 2.04 0.02 0.67 

09-E10 — — — — 0.4 2.14 — — 0.35 0.1 0.08 09-E11 Vuggy, silica-cut quartz veins — — <0.005 0.07 5.86 0.17 0.44 1.39 <0.01 0.67 

09-E12 Clastic sediment; Fe-cemented — — <0.005 0.2 0.62 0.19 12 0.08 0.03 0.02 

09-E13 Volcaniclastic silicified rib with Fe — — 0.006 0.09 0.36 0.16 12 0.02 0.03 <0.01 

09-E14 — — — — 0.45 0.19 — — 0.02 0.01 0.01 

09-E015 — — — — 1.68 0.14 — — 0.01 0.01 <0.01 09-E16 Fe-rich volcaniclastic sediment; silicified — — 0.01 0.01 0.42 0.18 2.21 0.05 0.01 0.01 

09-E18 Fe on fractures in volcaniclastic; sediment 

silicified

— — <0.005 0.07 4.99 0.45 13 1.05 0.01 0.56 

09-E19 Breccia with silicified quartz vein — — <0.005 <0.01 8.43 7.76 4.34 1.13 1.69 2.05 

09-E20 Breccia with silicified quartz vein — — <0.005 0.82 2.27 0.08 1.35 0.3 <0.01 0.34 

09-E23 Silicified tuff cut by Fe on fractures — — <0.005 0.38 5.55 0.16 8.85 0.31 0.02 0.1 

09-E24 Vuggy silica float cut by Fe-stained quartz 

veins

38.40844 –119.09776 0.006 0.14 4.76 0.14 7.93 1.35 0.02 0.25 

09-E25 Vuggy silica cut by Fe-stained quartz veins 38.40843 –119.09809 <0.005 0.05 3.81 0.12 5.9 0.71 0.01 0.44 

09-E27 Silica core of alteration cut by Fe veinlets 38.41013 –119.10394 0.03 5.19 2.3 0.09 >15 0.59 <0.01 0.12 

Latitude Longitude Au ppb Pd ppb Pt ppb Al % Ca% Fe% K% Mg% 

RW11-1 Brick-red (FeOx), soft, variably leached volcaniclastic deposits 38.40473 –119.06708 21 2 1.6 0.73 0.15 0.63 0.07 0.07 

RW11-2ME Silicified, FeOx-stained volcaniclastics, variably leached, resistant 38.407 –119.07178 4 <1 0.5 5.53 0.39 0.73 1.33 0.01 

RW11-3ME Silicified, FeOx-stained Masonic andesite with 

clay-altered phenocrysts 

38.40191 –119.06982 3 <1 <0.5 7.48 0.27 3.77 0.9 0.02 

RW11-4ME Beige-brick-red, clay-altered, partly silicified 

volcaniclastics

38.40318 –119.07082 6 <1 0.5 4.81 0.26 3.22 1.4 0.02 

RW11-5ME Silicified, clay-alunite-altered, variably sorted 

volcaniclastics, some FeOx

38.4006 –119.06973 4 <1 <0.5 6.82 0.16 4.33 2.15 0.02 
Table 1-2. Minor element concentrations in rock samples from the Red Wash-East Walker River alteration zone.—Continued [Fe, iron; FeOx, iron oxide; —, no data] Sample number As ppm Ba ppm Be ppm Bi ppm Cd ppm Ce ppm Co ppm Cr ppm Cs ppm Cu ppm Ga ppm In ppm La ppm Li ppm Mn ppm 

09-E02 9 560 <0.5 7 0.05 <0.5 2 21 44 0.63 20 — 20 — 11 

09-E04 8 130 <0.5 4 0.08 <0.5 3 23 107 2.08 20 — 20 — 41 

09-E09 28 181 0.3 1.8 <0.1 42.7 0.9 9 <5 34.7 27.7 0.06 22.5 <1 39 

09-E10 65 1,120 0.7 <2 0.27 0.5 <1 76 62 25 20 — 10 — 126 

09-E11 8 346 0.5 4.36 <0.1 97.2 0.4 6 <5 7.9 22.2 <0.02 44.3 <1 33 

09-E12 47 1,240 0.4 0.69 <0.1 20.6 1.4 10 <5 33.2 2.02 <0.02 11 2 182 

09-E13 42 1,160 0.3 0.66 0.2 4.94 2 8 <5 42.5 4.94 0.03 2.2 1 168 

09-E14 12 2,410 <0.5 2 0.04 <0.5 <1 15 16 0.21 <10 — <10 — 12 

09-E015 8 360 <0.5 2 0.01 <0.5 1 20 9 0.27 <10 — <10 — 21 

09-E16 34 1,240 0.2 0.59 <0.1 14.8 1.4 3 <5 17.1 2.07 <0.02 7.8 9 109 

09-E18 477 385 0.2 0.9 <0.1 82.4 1.2 14 <5 33.4 22.9 0.06 43.8 <1 59 

09-E19 <1 1,320 1.4 <0.04 <0.1 50.6 30.1 146 <5 33.2 20.3 0.05 30.3 5 789 

09-E20 11 1,120 0.1 0.96 <0.1 25.8 0.6 5 <5 14.4 4.31 0.04 15.3 <1 25 

09-E23 41 1,100 0.3 0.52 <0.1 31.8 0.9 22 <5 148 22.6 0.07 17.6 13 33 

09-E24 50 512 0.8 1.29 <0.1 80.9 1 30 <5 70.3 26.9 0.12 43.8 2 88 

09-E25 43 869 0.5 0.43 0.1 35 2 11 <5 87.7 18.1 0.06 19.6 <1 70 

09-E27 205 731 0.2 0.82 0.2 39.5 5.5 93 <5 189 52.1 0.12 23 3 42 

Ag ppm As ppm Ba ppm Be ppm Bi ppm Cd ppm Ce ppm Co ppm Cr ppm Cs ppm Cu ppm Ga ppm Hg ppm In ppm La ppm 

RW11-1 <1 10 1,000 0.2 0.18 0.1 12 1.2 4 <5 20.7 2.03 0.04 <0.02 6.5 

RW11-2ME <1 16 109 0.6 0.2 <0.1 41.3 0.9 15 <5 8 14.9 0.01 0.04 19.9 

RW11-3ME <1 31 134 0.3 1.37 <0.1 64.1 0.3 20 <5 39.3 23.5 0.13 0.07 32.6 

RW11-4ME <1 21 89 0.2 1.57 <0.1 31.5 0.7 9 <5 6.5 12.7 0.06 0.02 15.3 

RW11-5ME <1 36 82 0.4 0.6 <0.1 51.4 0.2 22 <5 24.8 22.8 0.09 0.05 26.3 
Table 1-2. Minor element concentrations in rock samples from the Red Wash-East Walker River alteration zone.—Continued[Fe, iron, FeOx, iron oxide; —, no data]

Sample 

number

P

ppm

Pb

ppm

Rb

ppm

Sb

ppm

Sc

ppm

Sn

ppm

Sr

ppm

Te

ppm

Th

ppm

Tl

ppm

U

ppm

V

ppm

W

ppm

Y

ppm

Zn

ppm

09-E02 680 258 — 11 4 — 881 — <20 <10 <10 76 <10 — 3 

09-E04 910 136 — 15 5 — 990 — <20 <10 <10 77 10 — 15 

09-E09 1,840 16.3 11.3 1.07 4 0.9 815 1 4.9 0.8 0.9 163 0.2 4.1 6 

09-E10 2,430 21 — <5 3 — 849 — <20 <10 10 104 <10 — 47 

09-E11 2,030 17.7 2.8 1.28 5.5 1.5 1,090 0.4 10.5 <0.1 1 151 0.3 2.9 6 

09-E12 1,810 7.2 2.4 0.31 1.4 0.4 379 0.1 2.7 <0.1 1.5 31 0.2 2.1 20 

09-E13 660 5.2 1.1 0.37 0.9 0.8 42.2 0.4 1.6 <0.1 1.1 73 0.3 2.5 16 

09-E14 40 7 — 7 1 — 38 — <20 <10 <10 6 <10 — <2 

09-E015 30 4 — 8 <1 — 19 — <20 <10 <10 4 <10 — <2 

09-E16 870 23.4 1.5 2.35 0.5 0.6 190 1 4.6 0.2 1.3 38 0.6 1.7 4 

09-E18 2,290 23.2 3.3 2.67 2.7 0.7 1,390 5.4 10 0.2 1.2 286 0.3 2 7 

09-E19 1,340 12.3 11 0.16 19.4 0.8 1,060 <0.1 3.1 <0.1 0.9 112 <0.1 13.1 79 

09-E20 870 15.4 1.4 1.29 2.8 0.7 1,010 0.3 3.2 0.2 1.1 38 0.7 2.9 5 

09-E23 1,910 66 0.9 0.61 2.7 2.4 2,570 2.3 2 <0.1 0.6 125 0.7 2 22 

09-E24 2,300 43.1 4.7 1.43 7.4 1.1 1,190 6.6 14.7 <0.1 3.5 137 1.3 6.2 23 

09-E25 1,260 34.4 2.5 0.55 3.5 0.9 1,120 0.3 3.8 0.2 1.7 122 0.6 3.2 11 

09-E27 1,670 34.2 0.7 1.85 5.3 1.1 1,210 6.2 3.8 <0.1 0.4 508 47.5 1.6 7 

Nb

ppm

Ni

ppm

P

ppm

Pb

ppm

Rb

ppm

Sb

ppm

Sc

ppm

Se

ppm

Sn

ppm

Sr

ppm

Te

ppm

Th

ppm

Tl

ppm

U

ppm

V

ppm

RW11-1 4.5 1.8 490 8.5 2.4 10.7 0.6 0.3 1 139 0.7 2.4 0.2 0.7 20 

RW11-2ME 7.8 0.9 1,260 20.5 4 3.86 7.3 1 1.5 816 1.1 8.1 0.2 2.4 111 

RW11-3ME 5.2 0.6 1,960 15.1 3.2 1.22 5.5 6.6 1.6 1,260 1.6 6.6 0.2 2.2 199 

RW11-4ME 2.1 1 1,800 22.7 8.5 2.52 3.3 1.2 2.3 348 0.7 5.6 0.5 0.9 70 

RW11-5ME 4.9 <0.5 1,630 16.1 5.6 1.36 6.5 7 1.2 952 2.1 8.8 2 1.4 200 
Table 1-3. Minor element concentrations in rock samples from the East Brawley Peak alteration zone. [—, no data] Sample number Description Latitude Longitude Au ppm Hg ppm Al % Ca% Fe% K% Mg% Na% S% Ti % 

08-BA-4 Andesite altered to kaolinite 38.25567 –118.90875 <0.005 0.34 5.32 0.17 2.56 0.06 0.02 0.02 0.29 0

10-BA-23 Quartz-dickite altered rhyolite 38.27127 –118.91707 <0.005 1.8 <0.01 <0.01 <0.01 <0.01 <0.01 <0.01 <0.01 <0

10-BA-24 Quartz-dickite alteration 38.27114 –118.91754 0.009 1.11 5.73 0.01 0.09 0.02 <0.01 <0.01 0.03 0.

10-BA-25 Quartz-dickite alteration, head of landslide 38.26963 –118.91960 0.017 0.37 0.91 0.03 0.68 0.03 <0.01 <0.01 0.12 0.

Table 1-3. Minor element concentrations in rock samples from the East Brawley Peak alteration zone.—Continued [—, no data] Sample number Be ppm Bi ppm Cd oon Ce ppm Co ppm Cr ppm Cs ppm Cu ppm Ga ppm In ppm La ppm Li ppm Mn ppm 

08-BA-4 0.3 0.53 <0.1 86.2 0.2 9 <5 28.5 22.5 <0.02 49.6 19 26 

10-BA-23 0.9 0.14 <0.1 46.3 0.1 <1 <5 <0.5 10.1 <0.02 30.7 <1 <5 

10-BA-24 0.2 0.52 <0.1 38.9 0.2 1 <5 3 14 <0.02 24.2 12 8 

10-BA-25 0.6 0.12 <0.1 24.9 0.2 3 <5 9.6 4.15 <0.02 16.2 5 9 

Table 1-3. Minor element concentrations in rock samples from the East Brawley Peak alteration zone.—Continued [—, no data] Sample number Pppm Pb ppm Rb ppm Sb ppm Sc ppm Sn ppm Sr ppm Te ppm Th ppm Tl ppm Uppm Vppm Wppm 

08-BA-4 1,780 49.4 1.4 6.43 3.4 0.8 1,290 1.8 11.1 <0.1 2.1 74 10 

10-BA-23 <50 11.2 2.1 16 2.1 0.6 <0.5 <0.1 19 0.1 8.6 <1 5.9 

10-BA-24 110 7.4 1.2 13 2.4 1 59.3 <0.1 28.6 0.1 10.2 28 4.8 

10-BA-25 340 19.5 1.2 20.6 1.9 1.3 297 <0.1 4.9 0.1 1.1 38 42.6 
Table 1-4. Minor element concentrations in rock samples from the Sawtooth Ridge alteration zone.[FeOx, iron oxide; bxd, brecciated; alt, altered; chal, chalcedony; lim, limonite; bx, breccia; hem, hematite; —, no data]

Sample 

number Latitude Longitude Description Au ppb Pd ppb Pt ppb Al % Ca% Fe% K% Mg% N

% 

SAW11-1ME 38.29305 –118.90932 Brecciated, FeOx-stained white 

rhyolite

16 <1 <0.5 5.96 0.08 0.43 0.11 0.07 0

SAW11-2ME 38.29442 –118.91269 Bxd FeOx-stained (limonite) rhyolite alt to chal, opal 16 <1 <0.5 6.03 0.05 0.11 0.08 0.02 0

SAW11-3ME 38.29452 –118.91475 White-beige bxd rhyolite, alt to 

chal, opal

6 <1 <0.5 7.42 0.09 0.18 0.19 0.02 0

SAW11-4ME 38.29772 –118.91724 White-beige bxd rhyolite, minor 

FeOx (lim+hem)

3 <1 <0.5 11.9 0.16 0.7 3.31 0.06 0

SAW11-5ME 38.30095 –118.91615 Dump; angular rhyolite clasts in 

heavy FeOx (lim+hem) matrix

9 <1 <0.5 2.33 0.09 21 0.87 0.01 0

SAW11-7ME 38.29756 –118.91457 White-beige bxd rhyolite, minor 

FeOx (lim+hem)

3 <1 0.5 9.3 0.1 0.27 0.24 0.04 0

SAW11-8ME 38.29097 –118.90810 Beige rhyolite flow and flow bx, 

minor FeOx

7 <1 <0.5 4.92 0.21 0.77 3.47 0.09 0

SAW11-9ME 38.29036 –118.91657 White bxd rhyolite with chal, opal, 

alunite matrix and veins

2 <1 <0.5 6.51 0.06 0.1 1.87 0.02 0

SAW11-10ME 38.29010 –118.91155 Beige-red rhyolite and bxd rhyolite 3 <1 <0.5 5.93 0.07 0.35 0.07 0.01 0SAW11-11ME 38.28904 –118.90930 Bxd rhyolite, FeOx-stained 3 <1 <0.5 6.24 0.31 2.14 1.92 0.3 307-BA-33 38.29023 –118.91201 Argillized tuff with secondary silica, 

Aurora Mine Road

<0.005 — — 4.38 0.07 0.62 0.06 <0.01 0
Table 1-4. Minor element concentrations in rock samples from the Sawtooth Ridge alteration zone.—Continued [FeOx, iron oxide; bxd, brecciated; alt, altered; chal, chalcedony; lim, limonite; bx, breccia; hem, hematite; —, no data] Sample number As ppm Ba ppm Be ppm Bi ppm Cd ppm Ce ppm Co ppm Cr ppm Cs ppm Cu ppm Ga ppm Hg ppm In ppm La ppm Li ppm 

SAW11-1ME 42 503 0.9 0.37 <0.1 16.6 0.7 2 7 27.8 14.4 2.11 <0.02 12.5 157 

SAW11-2ME 22 298 0.6 0.49 <0.1 16.3 0.2 1 11 18.3 15.4 0.61 <0.02 14.6 70 

SAW11-3ME 8 720 0.3 0.42 <0.1 31.7 0.3 3 7 15.6 16.6 0.3 0.02 19.8 51 

SAW11-4ME 12 156 0.7 0.38 <0.1 85.2 0.8 45 6 18.3 76.8 0.07 0.03 63.3 44 

SAW11-5ME 354 504 2.6 0.3 <0.1 33.3 0.6 8 7 21.6 11.3 0.51 <0.02 21.5 3 

SAW11-7ME 25 631 0.3 0.49 <0.1 43.2 0.2 4 8 10 18.2 0.12 0.03 27.6 78 

SAW11-8ME 289 901 1.4 0.09 0.1 45 0.6 2 12 10 12.3 1.63 <0.02 25.4 37 

SAW11-9ME 9 190 0.3 0.36 <0.1 14.3 0.2 3 8 3.5 17.8 1.61 <0.02 10.6 18 

SAW11-10ME 17 299 1.6 0.1 <0.1 43.9 0.8 <1 <5 5.9 10.3 0.75 <0.02 26.4 53 

SAW11-11ME 17 1,060 0.9 <0.04 <0.1 13.7 4.8 20 5 28.2 17.7 0.74 0.03 7.1 26 

07-BA-33 33 300 1.9 0.08 <0.1 21.7 0.5 3 <5 7.5 7.88 7.88 <0.02 11 41 

Table 1-4. Minor element concentrations in rock samples from the Sawtooth Ridge alteration zone.—Continued [FeOx, iron oxide; bxd, brecciated; alt, altered; chal, chalcedony; lim, limonite; bx, breccia; hem, hematite; —, no data] Sample number Ni ppm Pppm Pb ppm Rb ppm Sb ppm Sc ppm Se ppm Sn ppm Sr ppm Te ppm Th ppm Tl ppm Uppm Vppm 

SAW11-1ME 1.6 270 31.3 7.1 85.3 1.1 0.7 1.2 217 1.6 11.4 0.1 9 31 

SAW11-2ME <0.5 150 46.4 5 24.4 1.2 0.4 1.3 120 3.8 16.3 0.2 7 14 

SAW11-3ME 1.1 740 30.5 4.9 9.45 1.3 <0.2 1.2 199 0.5 16.6 0.1 9.2 37 

SAW11-4ME 3.1 1,680 25.8 7.6 7 2.1 <0.2 0.9 1,740 0.4 41.9 0.1 7.6 131 

SAW11-5ME 0.6 1,590 27.1 6.4 25.8 1.7 1 0.7 259 0.2 21.3 <0.1 9.1 190 

SAW11-7ME 0.8 550 33.2 4.7 6.08 2 0.4 1.1 417 0.2 23 0.4 12.8 78 

SAW11-8ME 1.2 380 32.1 138 97.7 0.7 <0.2 0.7 241 0.1 24.8 1.3 7.9 33 

SAW11-9ME <0.5 210 34.2 6.7 9.24 1.8 <0.2 0.9 113 0.1 9.9 0.1 7.4 30 

SAW11-10ME 2.5 410 34.2 3.2 10.5 2.7 0.5 0.9 295 1.4 25.6 <0.1 11.7 57 

SAW11-11ME 19.7 570 9.8 53.6 15.4 9.8 0.3 1.1 531 1 2.9 0.3 1.2 83 

07-BA-33 0.8 120 12.2 2 5.18 1.1 1.8 0.6 56.2 <0.1 32.1 <0.1 10.3 17 
Table 1-5. Minor element concentrations in rock samples from the Aurora Canyon alteration zone.

Sample 

number Latitude Longitude Description Au ppm Hg ppm Al % Ca% Fe% K% Mg% Na% S% T

% 

PP09-20 38.25336 –119.13584 Quartz-alunite-clay-altered andesite <0.005 10 3.22 0.07 6.87 1.13 <0.01 0.12 2.55 0PP09-21 38.26387 –119.12638 Silicified and brecciated andesite <0.005 3.11 6.63 0.16 4.64 1.71 0.03 0.73 >5 0

PP09-22 38.257 –119.13689 Quartz-alunite-altered andesite <0.005 0.8 0.44 0.13 0.1 0.04 0.01 <0.01 0.06 0

PP09-23 38.25974 –119.13051 Quartz-clay-altered andesite <0.005 20.6 0.48 0.03 0.57 0.03 0.01 <0.01 0.09 0

08-BA-43 38.25330 –119.13567 Silicified andesite with alunite veins <0.005 0.23 6.68 0.13 0.3 2.75 <0.01 0.18 >5 008-BA-44 38.256910 –119.13795 Quartz-alunite-altered andesite <0.005 0.59 10.2 0.54 1.32 1.22 0.03 2.19 >5 0

08-BA-45 38.256325 –119.13673 Fine-grained alunite <0.005 0.09 6.22 0.08 0.53 2.21 0.01 0.36 4.71 0

09-BA-45 38.270139 –119.13000 Silicified hematitic breccia 0.018 1.9 0.22 0.02 0.75 0.01 <0.01 <0.01 0.23 0

Table 1-5. Minor element concentrations in rock samples from the Aurora Canyon alteration zone.—Continued

Sample 

number

Be

ppm

Bi

ppm

Cd

ppm

Ce

ppm

Co

ppm

Cr

ppm

Cs

ppm

Cu

ppm

Ga

ppm

In

ppm

La

ppm

Li

ppm

Mn

ppm

PP09-20 0.3 2.15 <0.1 49.1 0.9 16 <5 35.1 9.62 0.03 27.9 3 23 

PP09-21 0.4 2.18 <0.1 32.6 1 14 <5 19.3 20.9 0.05 17.7 5 64 

PP09-22 0.3 1.37 <0.1 7 0.3 3 <5 8.4 0.65 <0.02 3.7 7 28 

PP09-23 0.1 4.52 <0.1 10.7 0.5 5 <5 19.6 2.28 0.03 5.9 26 13 

08-BA-43 0.4 2.23 <0.1 108 0.6 22 <5 7.7 13.8 0.04 56.7 2 20 

08-BA-44 0.4 2.34 0.2 90.4 0.6 37 <5 31.7 26 <0.02 46.2 4 151 

08-BA-45 0.2 0.61 <0.1 23.9 0.3 33 <5 2.6 11.7 <0.02 15.3 1 30 

09-BA-45 0.1 2.37 <0.1 2.51 2 2 <5 15.2 0.58 <0.02 2 <1 73 

Table 1-5. Minor element concentrations in rock samples from the Aurora Canyon alteration zone.—Continued

Sample 

number

P

ppm

Pb

ppm

Rb

ppm

Sb

ppm

Sc

ppm

Sn

ppm

Sr

ppm

Te

ppm

Th

ppm

Tl

ppm

U

ppm

V

ppm

W

ppm

PP09-20 1,640 23.5 3 2.39 2.2 0.8 533 0.5 10 0.3 1.5 102 0.5 

PP09-21 1,290 13.9 5.6 13.5 3 0.7 827 3.7 3.9 0.2 0.8 164 2.5 

PP09-22 2,240 1.8 1.4 83 1.2 0.4 53.5 0.6 1.5 <0.1 0.7 5 0.6 

PP09-23 270 30.5 2.1 33.2 2.8 0.9 205 1.9 3 0.7 2.2 17 6 

08-BA-43 2,490 58.2 6.8 2.97 4.9 1 1,020 0.2 18.5 2.2 3.3 104 1 

08-BA-44 3,310 17.6 6.8 4.42 6.4 1.8 458 0.5 10.9 0.8 2.5 93 1.7 

08-BA-45 570 10.5 4 7.91 4.1 0.9 561 0.4 3.1 <0.1 0.5 67 1.2 

09-BA-45 170 3.8 1.1 4.93 1.6 0.6 77.6 4.1 1.8 0.1 1.3 11 0.3 
Table 1-6. Minor element concentrations in rock samples from the Potato Peak alteration zone. Sample number Latitude Longitude Description Au ppm Hg ppm Al % Ca% Fe% K% Mg% Na% S% 

POTPK08-1 38.24439 –119.10512 Silicified volcaniclastic breccia; vuggy quartz, cinnabar, barite matrix 0.903 171,339 0.62 0.02 2.29 0.12 0.01 <0.01 3.74 

POTPK09-20 38.24398 –119.10379 Volcaniclastic deposits replaced by fine-grained quartz and kaolinite <0.005 17.4 8.08 0.21 7.58 0.27 0.05 0.02 0.28 

08-BA-46 38.244298 –119.10385 Silicified volcaniclastic deposits with alunite matrix <0.005 0.71 3.99 0.11 3.83 1.16 <0.01 0.29 3.22 

08-BA-47 38.244298 –119.10385 Silicified breccia with cinnabar matrix 0.064 19,400 0.26 0.02 0.54 0.03 <0.01 <0.01 0.27 

08-BA-48 38.244298 –119.10385 Volcaniclastic deposits altered to dickite <0.005 9.97 8.89 0.14 0.3 0.08 0.02 <0.01 0.31 

08-BA-49 38.246409 –119.09876 Volcaniclastic deposits altered to dickite and pyrite 0.093 5.15 5.19 0.04 1.79 0.02 <0.01 <0.01 2.09 

Table 1-6. Minor element concentrations in rock samples from the Potato Peak alteration zone.—Continued Sample number Be ppm Bi ppm Cd ppm Ce ppm Co ppm Cr ppm Cs ppm Cu ppm Ga ppm In ppm La ppm Li ppm Mn ppm 

POTPK08-1 0.4 1.32 0.3 37.5 5.9 12 <5 30 2.01 0.12 16.6 22 8 

POTPK09-20 1 0.27 <0.1 81.8 0.3 99 <5 29.4 21.1 0.13 41.5 52 9 

08-BA-46 0.3 18.5 <0.1 87.7 0.6 26 <5 13.2 21.7 0.05 39.4 1 6 

08-BA-47 0.2 5.17 <0.1 9.5 0.7 4 <5 27.6 0.7 <0.02 4.5 10 8 

08-BA-48 0.4 8.32 <0.1 75.4 0.2 24 <5 6.9 28.4 0.03 35 82 10 

08-BA-49 0.3 3.85 <0.1 49.9 4.8 18 <5 17.1 15.7 <0.02 24.6 73 <5 

Table 1-6. Minor element concentrations in rock samples from the Potato Peak alteration zone.—Continued Sample number Pppm Pb ppm Rb ppm Sb ppm Sc ppm Sn ppm Sr ppm Te ppm Th ppm Tl ppm Uppm Vppm Wppm 

POTPK08-1 250 61.4 4.6 98.4 5.3 0.9 172 2.6 10.4 3.8 5.6 14 13.5 

POTPK09-20 3,000 59 11.6 10.3 12.4 1.8 1,220 0.8 21 0.8 3.9 265 6.1 

08-BA-46 2310 33 4 6.96 8.9 0.9 1,040 0.4 21.4 0.2 2 81 2.5 

08-BA-47 230 4.7 1.2 20.3 0.8 1.3 148 0.3 3.2 0.3 1.6 9 1.3 

08-BA-48 1,960 17.2 2.4 14.5 6.7 1.7 1,120 1 17.9 0.2 3.6 166 10.1 

08-BA-49 850 22.5 1 7.75 2.3 0.7 875 0.8 13.2 0.5 1.2 60 1.9 
Table 1-7. Minor element concentrations in rock samples from the Aurora Mining District.[K, potassium; —, no data]

Sample 

number Latitude Longitude Description1 Au ppm Hg ppm Al % Ca% Fe% K% Mg% Na% S% T

% 

AUR10-1 38.27118 –118.89644 Dream adit dump; Bald Eagle vein? 0.005 0.73 2.77 0.03 0.12 0.93 <0.01 0.17 1.98 0

AUR11-10ME 38.27321 –118.90045 Iregularly banded quartz vein with 

sulfide streaks, clots; Cortez-Utah

0.121 0.02 0.84 0.06 0.28 0.32 0.05 0.01 0.17 0

AUR11-12 38.27019 –118.9017 Irregularly banded quartz vein, 

minor sulfides; Seminole

2 0.43 0.68 0.03 0.54 0.26 0.04 <0.01 0.57 <0

AUR11-15 38.27321 –118.89905 Quartz vein, minor sulfides; 

Gladiator

0.505 0.61 1.69 0.09 0.39 0.68 0.1 0.02 0.34 0

AUR11-16 38.28483 –118.8924 Pyritic quartz stockwork, dump; 

Wide West

1.62 0.06 1.27 0.04 1.96 0.88 0.08 0.02 1.63 0

AUR11-17A 38.27727 –118.88483 Quartz-sulfide vein, mine dump; 

drainage between Middle-Martinez Hills

8.16 0.03 1.31 0.07 0.67 0.63 0.04 0.02 0.39 0

AUR11-19ME 38.29572 –118.89484 Quartz-K-mica vein, open cut, rhyolite of Aurora 0.026 0.16 3.07 0.08 0.1 0.17 0.02 <0.01 0.01 0

12-BA-19A 38.26533 –118.90017 Esmeralda vein, sulfide dump 

sample

84.8 0.29 1.26 0.05 0.44 0.44 0.06 0.02 0.51 0

12-BA-19B 38.26533 –118.90017 Esmeralda vein, sulfide dump 

sample

65.1 0.2 0.99 0.05 0.43 0.35 0.06 0.01 0.29 0

NE-1 38.30685 –118.84810 New Esmeralda Mine, quartz vein 

with black sulfides

3.42 1.18 0.55 0.09 0.1 0.1 0.03 0.01 0.02 <0

NE-2 38.30685 –118.84810 New Esmeralda Mine, quartz vein 

with black sulfides

0.658 0.23 0.32 0.1 0.09 0.05 0.04 0.01 <0.01 <0.

11-BA-52C 38.30685 –118.84810 New Esmeralda Mine, quartz vein 

with black sulfides

0.102 0.09 0.68 0.06 0.21 0.15 0.03 0.02 <0.01 0.

11-BA-52D 38.30685 –118.84810 New Esmeralda Mine, quartz vein 

with black sulfides

0.224 0.1 0.89 0.07 0.25 0.2 0.04 0.01 <0.01 0.
Table 1-7. Minor element concentrations in rock samples from the Aurora Mining District.—Continued [K, potassium; —, no data] Sample number Be ppm Bi ppm Cd ppm Ce ppm Co ppm Cr ppm Cs ppm Cu ppm Ga ppm In ppm La ppm Li ppm Mn ppm Mo ppm Nb ppm 

AUR10-1 <0.1 1.3 <0.1 9.16 0.2 7 <5 4.2 15.5 <0.02 7.7 <1 <5 0.83 3 AUR11-10ME 1.1 0.89 0.3 6.77 0.4 1 <5 36.9 2.39 <0.02 3.5 73 27 111 0.7 

AUR11-12 0.7 0.46 <0.1 2.91 0.1 1 <5 26.4 1.43 <0.02 2.1 66 80 57.8 <0.1 AUR11-15 1.6 1.16 0.5 13.1 1 1 13 29.1 6.53 <0.02 5.9 89 39 1,310 1.4 

AUR11-16 1.4 3.58 0.5 20 0.5 3 7 131 4.06 <0.02 13 150 40 924 0.5 

AUR11-17A 1.9 0.17 <0.1 14 0.2 2 <5 13.6 2.36 <0.02 9.4 99 40 129 1.1 

AUR11-19ME 0.9 0.31 <0.1 13 0.2 1 <5 9.6 7.73 <0.02 8.3 107 16 13.5 4.2 

12-BA-19A 0.8 0.04 3.3 5.06 0.5 1 <5 1,090 2.02 <0.02 2.8 85 51 53.4 0.8 

12-BA-19B 0.7 0.08 1.8 1.95 0.4 <1 <5 367 1.77 <0.02 1.2 92 49 94.6 0.3 

NE-1 2 37.4 <0.1 0.48 0.2 <1 8 13.9 1.4 <0.02 <0.5 119 24 12.1 0.1 

NE-2 2 13.8 <0.1 0.7 1 <1 <5 7.7 3.92 <0.02 <0.5 63 167 1.1 0.1 

11-BA-52C 1.4 1.85 0.2 2.64 28.7 2 6 10.9 1.52 <0.02 1 130 826 11.1 0.3 11-BA-52D 1.3 1.34 0.2 3.23 44 2 5 12.9 1.78 <0.02 1.2 123 1,100 17.6 0.3 

Table 1-7. Minor element concentrations in rock samples from the Aurora Mining District.—Continued [K, potassium; —, no data] Sample number Rb ppm Sb ppm Sc ppm Se ppm Sn ppm Sr ppm Te ppm Th ppm Tl ppm Uppm Vppm Wpp

AUR10-1 0.6 8.84 0.8 — 3.4 404 0.6 2.4 <0.1 0.2 18 

AUR11-10ME 24 18.6 0.4 0.4 0.2 23.4 1.1 0.4 0.5 0.7 11 

AUR11-12 20.5 25.8 0.1 2.9 0.7 14.2 0.4 <0.2 0.3 0.5 9 

AUR11-15 52.9 79 0.6 1 0.4 49.4 1.3 0.7 12.3 1.1 24 

AUR11-16 62.8 64.1 1.3 1.9 0.3 138 3.7 0.2 3.6 0.2 52 1

AUR11-17A 34.3 69.8 0.3 2.2 0.3 44.4 0.2 0.6 0.8 0.3 5 

AUR11-19ME 15.3 20.8 1 0.7 0.4 54.1 <0.1 9.3 0.2 4.4 43 

12-BA-19A 20.9 264 0.3 203 0.2 21.8 15.7 0.4 0.3 0.1 8 

12-BA-19B 20.7 275 0.2 198 0.2 20 7.5 <0.2 0.2 <0.1 8 

NE-1 10.8 267 <0.1 3.7 0.1 35.5 13 <0.2 0.6 <0.1 3 

NE-2 4.9 226 <0.1 0.8 <0.1 47.7 6.6 <0.2 0.6 <0.1 2 

11-BA-52C 12.2 88.7 0.3 0.2 0.1 45.3 0.4 0.2 6 0.1 5 

11-BA-52D 15.3 67.5 0.3 <0.2 0.2 42.6 0.6 0.3 9.4 0.1 7 

1Locations of veins (Bald Eagle, Cortez-Utah, Seminole, Gladiator, Wide West) are on figure 20.
Table 1-8. Minor element concentrations in rock samples from the Four Corners alteration zone.[Fe, iron; Mn, manganese]

Sample 

number Latitude Longitude Description Au ppm Hg ppm Al % Ca% Fe% K% Mg% Na% S% T

% 

08HC1 38.28055 –119.10158 Red mud layer 0.005 0.84 0.77 0.35 1.56 0.07 0.02 0.02 0.2 

08HC2 38.28055 –119.10158 Silt/sand sediment below mud <0.005 0.08 0.34 0.1 0.39 0.04 <0.01 0.02 0.06 

08HC3 38.28055 –119.10158 Red sand below mud <0.005 0.65 1.4 0.29 0.52 0.11 0.03 0.03 0.23 

08HC4 38.28067 –119.10175 Coarse pebble/sand <0.005 0.22 0.2 0.15 1.65 0.02 <0.01 0.01 0.12 

08HC5 38.28046 –119.10162 Fe and Mn oxide breccia 0.006 6.2 0.51 0.08 12.9 0.05 <0.01 0.02 0.06 

08HC6 38.28049 –119.10157 White opalite breccia <0.005 0.39 0.2 0.44 0.19 0.08 0.01 0.02 0.26 

08HC7 38.28049 –119.10157 Black massive benatile <0.005 15.1 0.39 0.08 12.5 0.06 <0.01 0.02 0.04 

08HC8 38.28094 –119.09985 Knob of Fe oxide breccia <0.005 9.9 1.22 0.44 4.32 0.48 0.05 0.03 0.66 

08-BA-30 38.28048 –119.10142 Red hematitc silicified breccia with 

fragments of white silica

<0.005 0.49 0.23 0.02 1.09 0.03 <0.01 0.02 <0.01 

08-BA-31 38.28062 –119.09941 Silicified jarosite-rich breccia with 

blocks of flow-banded andesite?

0.061 0.17 1.33 0.12 2.27 0.47 0.07 0.02 0.45 

Table 1-8. Minor element concentrations in rock samples from the Four Corners alteration zone.—Continued[Fe, iron; Mn, manganese]

Sample 

number

Be

ppm

Bi

ppm

Cd

ppm

Ce

ppm

Co

ppm

Cr

ppm

Cs

ppm

Cu

ppm

Ga

ppm

In

ppm

La

ppm

Li

ppm

Mn

ppm

08HC1 0.8 1.97 0.7 11.1 6.5 19 8 13.3 1.68 0.02 5.5 86 772 

08HC2 0.5 0.63 <0.1 3.77 0.4 11 6 5.3 1.2 <0.02 1.8 77 27 

08HC3 0.6 0.59 <0.1 9.42 1.1 18 8 13.7 2.56 <0.02 4.9 81 86 

08HC4 0.2 0.93 <0.1 2.33 0.7 11 <5 3.8 1.52 <0.02 1.6 57 43 

08HC5 0.6 9.13 <0.1 16.6 2.2 33 7 16.8 4.06 0.98 6.6 68 129 

08HC6 0.2 1.54 <0.1 1.85 1.2 8 <5 32.5 0.86 <0.02 0.7 15 82 

08HC7 0.8 135 <0.1 14.6 1.4 21 5 25.4 5.48 0.49 6.6 52 75 

08HC8 1.4 0.2 0.3 21.8 2.1 47 8 6.9 21.9 0.06 15.8 83 279 

08-BA-30 0.3 1.6 <0.1 0.77 0.2 3 <5 7.2 1.6 <0.02 <0.5 42 44 

08-BA-31 0.7 0.27 0.1 35 0.6 9 9 20.4 17.6 0.09 20.9 28 46 
Table 1-8. Minor element concentrations in rock samples from the Four Corners alteration zone.—Continued [Fe, iron; Mn, manganese] Sample number Pppm Pb ppm Rb ppm Sb ppm Sc ppm Sn ppm Sr ppm Te ppm Th ppm Tl ppm Uppm Vppm Wpp

08HC1 1,080 21.7 6.6 52.1 1.8 1 135 2 1.4 0.3 0.7 38 24

08HC2 130 7.1 4.2 42.6 1.2 0.6 33.3 0.6 0.5 0.2 0.2 13 4

08HC3 950 10.8 8.5 53.3 2.3 0.7 186 1.3 1.2 0.2 0.6 26 3

08HC4 120 2.9 1.9 48.4 0.7 1.4 25.9 0.8 0.3 <0.1 0.4 22 24

08HC5 760 201 4.8 20.6 2.9 2 150 3.3 3.7 0.3 1.3 56 5

08HC6 2,080 4.5 2 30.5 0.9 1.2 32.2 1.4 0.3 <0.1 0.3 6 2 

08HC7 1,020 421 3.9 109 3.8 3.3 76.9 18.1 3.4 0.3 1.7 24 25

08HC8 2,720 84.7 32.3 69.2 9.8 1 559 <0.1 16.6 1.3 1 166 74

08-BA-30 <50 3.6 3.2 51 0.5 0.5 8.7 0.2 <0.2 0.1 0.2 22 7

08-BA-31 3,850 795 32.5 152 27.6 1.5 826 0.9 41.8 0.7 1.5 28 18
Table 1-9. Minor element concentrations in rock samples from the Paramount-Bald Peak alteration zone.[Hg, mercury; HgS, mercury sulfide; mm, millimeter; cb, cinnabar; py, pyrite; —, no data]

Sample 

number Latitude Longitude Description Location Au ppm Hg ppm 

ATAS06-1 38.26255 –119.01192 Sinter with mm-thick black layers, intact terrace, Atastra Creek Atastra Creek 0.004 1.56 

06-BA-5 38.2621 –119.0125 Silicified fault underlying sinter terrace; Atastra Creek Atastra Creek 0.009 0.85 06-BA-6 38.2621 –119.0125 Banded sinter with black bands; Atastra Creek Atastra Creek 0.005 0.12 06-BA-7 38.2643 –119.0074 Chalcedony veins cutting tuff of Paramount; Atastra Creek Atastra Creek <0.005 13.4 06-BA-8 38.2643 –119.0074 Chalcedony veins cutting tuff of Paramount; Atastra Creek Atastra Creek <0.005 4.65 11-BA-43 38.26169 –119.00869 Fe-oxide-silica altered lower Eureka Valley Tuff overlying strongly argillized 

Paramount tuff and sediments

Atastra Creek 0.01 5.94 

11-BA-33A 38.34568 –118.98167 Chalcedony-pyrite vein cutting silicified Paramount tuff and sediments Hilton Springs 2.64 3.94 11-BA-33B 38.34568 –118.98167 Silicified pyritic wall rock from 11-BA-33A Hilton Springs 1.62 44.1 11-BA-34A 38.29883 –118.99753 Silicified finely laminated sediments in Paramount tuff and sediment sequence Hilton Springs 0.023 0.23 11-BA-34B 38.29883 –118.99753 Silicified finely laminated sediments in Paramount tuff and sediment sequence Hilton Springs 0.542 2.25 11-BA-35A 38.29805 –118.99864 Silicified finely laminated sediments in Paramount tuff and sediment sequence Hilton Springs 0.026 2.06 

11-BA-35B 38.29805 –118.99864 Silicified finely laminated sediments in Paramount tuff and sediment sequence Hilton Springs 0.061 4.17 

PMT06-1 38.27787 –119.05766 5-foot chalcedonic quartz vein with white clay pockets, long dozer cut, 

Paramount Mine

Paramount Mine hill 0.007 137 

PMT06-1A 38.27787 –119.05766 5-foot chalcedonic quartz vein with white clay pockets, long dozer cut, 

Paramount Mine

Paramount Mine hill 0.034 71.5 

PMT06-2 38.27823 –119.05859 Dense 7-foot chalcedonic quartz vein with minor cb, py; upper adit, Paramount Mine Paramount Mine hill 0.061 1,600 PMT06-3 38.27729 –119.06083 Sinter blocks, west dismembered terrace, Paramount Mine hill Paramount Mine hill 0.018 1.35 07PM1 38.2773 –119.0595 Sinter Paramount Mine hill 0.017 0.53 07PM2 38.2773 –119.0595 Quartz carbonate breccia Paramount Mine hill 0.237 1.23 07PM4 38.2777 –119.0577 Chalcedony vein cutting breccia Paramount Mine hill 0.495 94.2 07PM6 38.2759 –119.0539 Silicified tuff cut by quartz veins Paramount Mine hill 0.209 16.4 07PM8 38.2779 –119.0566 White to tan chalcedonic sinter Paramount Mine hill 0.017 2.45 07PM9 38.2778 –119.0566 Sinter cut by red chalcedony Paramount Mine hill 0.032 1.48 07PM10 38.2778 –119.0566 Red chalcedony in sinter breccia Paramount Mine hill 0.067 2.71 07PM11 38.2778 –119.0566 White sinter clasts in breccia Paramount Mine hill 0.011 0.24 

07PM14 38.2792 –119.0598 Calcines from Paramount Hg Mine Paramount Mine hill 0.103 17.4 

07PM12 38.2789 –119.0592 HgS in silicified tuff Paramount Mine hill 0.063 516 

07-BA-20 38.2769 –119.0569 Laminated gray silica, possible pool sinter near Paramount Mine Paramount Mine hill 0.917 1.51 

07-BA-20A 38.2769 –119.0569 Laminated gray silica, possible pool sinter near Paramount Mine Paramount Mine hill 3.57 4.28 
Table 1-9. Minor element concentrations in rock samples from the Paramount-Bald Peak alteration zone.—Continued [Hg, mercury; HgS, mercury sulfide; mm, millimeter; cb, cinnabar; py, pyrite; —, no data] Sample number K% Mg% Na% S% Ti % Ag ppm As ppm Ba ppm Be ppm Bi ppm Cd ppm Ce ppm Co ppm 

ATAS06-1 0.04 <0.01 <0.01 0.02 0.07 <1 80 1,050 <5 <0.1 <0.2 16.2 <0.5 

06-BA-5 0.07 0.02 0.01 0.39 0.12 <1 67 687 7.1 0.13 <0.1 19.6 0.4 

06-BA-6 0.06 0.01 0.01 0.07 0.07 <1 93 1,060 6.7 0.08 <0.1 13.8 0.2 

06-BA-7 1.15 0.08 0.21 1.7 0.16 <1 122 340 3.8 <0.04 0.1 51.1 21.3 

06-BA-8 0.27 0.06 0.05 0.12 0.2 <1 47 1,910 4.5 <0.04 <0.1 37.7 2.1 

11-BA-43 0.11 0.02 0.02 0.01 0.14 <1 61 407 5.9 0.13 <0.1 69.7 1.2 

11-BA-33A 1.99 0.02 0.03 1.15 0.04 18 643 602 1.4 0.13 <0.1 15.2 0.6 

11-BA-33B 2.97 0.02 0.03 0.1 0.05 7 288 2,810 1.4 0.17 <0.1 30.5 0.5 

11-BA-34A 0.18 0.02 0.01 0.08 0.02 1 37 203 3.5 0.15 <0.1 5.01 0.8 

11-BA-34B 0.33 0.04 <0.01 0.39 0.04 8 377 2,310 4.5 0.13 <0.1 20.9 0.8 

11-BA-35A 0.18 0.02 0.01 0.28 0.03 3 236 2,530 6.1 0.1 <0.1 5.72 1.4 

11-BA-35B 0.12 0.01 0.02 0.24 0.03 1 205 145 4.1 0.06 <0.1 7.31 7.2 

PMT06-1 0.09 <0.01 <0.01 <0.01 0.02 <1 40 758 9 <0.1 <0.2 1.5 <0.5 PMT06-1A 0.06 <0.01 <0.01 <0.01 0.02 <1 <30 217 8 <0.1 <0.2 1.7 <0.5 PMT06-2 0.06 <0.01 <0.01 <0.01 0.02 <1 <30 863 6 <0.1 <0.2 2.9 0.6 PMT06-3 0.02 <0.01 <0.01 <0.01 <0.01 <1 <30 41.5 25 <0.1 <0.2 0.4 <0.5 

07PM1 0.03 <0.01 0.01 0.03 <0.01 <1 17 115 9.5 <0.04 <0.1 0.97 0.2 07PM2 1.37 0.03 0.03 0.02 0.04 <1 40 268 6.1 0.16 0.1 29.4 0.9 07PM4 0.11 <0.01 0.01 0.1 0.06 5 170 931 6.7 0.09 <0.1 26.3 0.2 07PM6 1.63 0.02 0.02 0.37 0.11 2 580 621 8.4 <0.04 0.2 23.3 1.3 

07PM8 0.06 <0.01 0.01 0.02 <0.01 <1 28 412 9.5 <0.04 <0.1 2.12 0.6 

07PM9 0.08 <0.01 0.01 0.05 0.05 <1 72 506 9.3 <0.04 <0.1 10.7 0.9 07PM10 0.16 0.03 0.01 0.04 0.06 <1 90 357 6.5 0.05 <0.1 18.1 0.8 07PM11 0.03 <0.01 0.01 <0.01 <0.01 <1 18 56 13.9 <0.04 <0.1 1.09 0.5 07PM14 0.17 0.04 0.07 0.03 0.22 <1 55 586 3.6 0.13 <0.1 40.5 2.3 

07PM12 0.06 <0.01 0.01 0.03 0.24 <1 5 584 2.9 <0.04 <0.1 3.91 0.3 

07-BA-20 0.78 <0.01 0.02 0.03 <0.01 6 19 559 11.3 0.13 <0.1 2.35 0.8 

07-BA-20A 2.61 0.06 0.05 0.04 0.04 3 38 883 7.7 0.04 <0.1 7.43 0.4 
Table 1-9. Minor element concentrations in rock samples from the Paramount-Bald Peak alteration zone.—Continued[Hg, mercury; HgS, mercury sulfide; mm, millimeter; cb, cinnabar; py, pyrite; —, no data]

Sample 

number

Cs

ppm

Cu

ppm

Ga

ppm

In

ppm

La

ppm

Li

ppm

Mn

ppm

Mo

ppm

Nb

ppm

Ni

ppm

P

ppm

Pb

ppm

ATAS06-1 7.9 <5 27 <0.2 9.2 30 — 3 3 <5 — 7 

06-BA-5 10 3.6 57.2 <0.02 9.8 34 45 5.82 4.1 12.7 330 9.8 

06-BA-6 10 4.9 45.7 <0.02 7 32 32 3.29 2.6 12.5 190 6.8 

06-BA-7 28 23.8 9.01 <0.02 24.3 79 52 2.87 6.1 12.1 140 18.5 

06-BA-8 20 12.6 9.27 <0.02 19.4 84 46 1.1 6.7 7.5 140 23.6 

11-BA-43 25 25.4 2.95 <0.02 33.7 62 56 1.18 7.1 1.6 200 28.1 

11-BA-33A 9 12 3.07 <0.02 8.7 124 14 1 2.9 1.1 300 12 

11-BA-33B 9 9.8 3.93 <0.02 20.3 100 17 0.84 5.9 1.2 720 19.4 

11-BA-34A 39 7.9 4.7 <0.02 2.6 49 71 0.6 0.8 1.5 60 3.5 

11-BA-34B 20 10.6 5.03 <0.02 15.5 65 35 1.43 2.5 1.7 680 25 

11-BA-35A 24 8.9 4.01 <0.02 3.6 54 23 1.26 1.2 1.9 90 10.5 

11-BA-35B 25 3.2 5.84 <0.02 3.9 65 18 0.82 0.9 9.8 70 4.9 

PMT06-1 15.8 7 8 <0.2 1.5 40 — <2 <1 8 — <5 

PMT06-1A 14.8 <5 15 <0.2 1.3 50 — <2 <1 11 — <5 

PMT06-2 11.8 8 12 <0.2 3.3 80 — <2 <1 6 — 7 

PMT06-3 6.1 8 12 <0.2 0.3 60 — <2 <1 12 — <5 

07PM1 6 0.9 9.99 <0.02 0.7 18 69 0.6 0.2 0.5 60 0.9 

07PM2 10 2.6 7.64 <0.02 16.9 82 67 0.38 1.6 1.8 140 5.7 

07PM4 11 22.7 6.27 <0.02 13.4 11 29 0.43 2.8 <0.5 240 9.5 

07PM6 13 5.3 7.33 <0.02 13.8 70 117 3.65 0.6 1 200 5.9 

07PM8 10 1.3 7.07 <0.02 1.1 122 99 0.45 0.1 1.1 <50 1.4 

07PM9 12 5.3 6.27 <0.02 5.4 81 98 0.82 1.7 1.3 90 3.4 

07PM10 15 6.7 5.06 <0.02 11.4 162 76 0.82 1.8 1.4 380 4.7 

07PM11 6 1.5 8.93 <0.02 0.6 18 186 1.22 <0.1 1.1 <50 1.2 

07PM14 9 6.5 12.5 <0.02 22.7 106 54 0.92 6 3.2 340 38.9 

07PM12 9 1.1 1.51 <0.02 2.1 96 124 1.85 6.6 0.8 <50 3.8 

07-BA-20 18 4.9 6.02 <0.02 1.1 53 140 0.95 0.2 1.6 60 4.9 

07-BA20A 34 10.4 8.85 <0.02 5.4 83 48 0.19 0.7 3.7 80 5.2 
Table 1-9. Minor element concentrations in rock samples from the Paramount-Bald Peak alteration zone.—Continued [Hg, mercury; HgS, mercury sulfide; mm, millimeter; cb, cinnabar; py, pyrite; —, no data] Sample number Sc ppm Sn ppm Sr ppm Te ppm Th ppm Tl ppm Uppm Vppm Wppm Yppm Zn ppm 

ATAS06-1 <5 <1 340 <0.5 3.3 1.8 0.79 11 19 1.5 6 

06-BA-5 0.9 0.5 456 <0.1 5.7 0.8 0.7 18 125 1 3 

06-BA-6 0.5 0.4 257 <0.1 4.1 1.6 0.5 11 20.9 0.7 5 

06-BA-7 2.7 0.9 155 <0.1 6.9 2.1 8.7 47 123 4.5 9 

06-BA-8 2.7 1.3 72.6 <0.1 9 0.3 4.9 28 69.7 3.5 6 

11-BA-43 2.1 0.7 45.8 <0.1 14.2 0.3 5.4 83 147 6.3 13 

11-BA-33A 1 0.4 194 0.1 6.1 3.4 3.1 6 5 2.8 2 

11-BA-33B 1.8 0.5 491 <0.1 9.5 4.7 4.7 14 15.9 6.2 10 

11-BA-34A 0.8 0.3 106 0.2 2.5 0.7 0.9 9 2.9 1 3 

11-BA-34B 1.6 0.4 361 <0.1 4.9 0.9 3.1 23 21.6 4.1 9 

11-BA-35A 1 0.3 209 <0.1 2.7 0.8 2.2 19 7.8 1.8 6 

11-BA-35B 1.5 0.3 102 <0.1 2.5 1.9 6.1 20 5.9 2.5 14 

PMT06-1 <5 2 80.4 <0.5 0.3 0.7 0.27 <5 16 0.9 <5 

PMT06-1A <5 <1 49.6 <0.5 0.4 <0.5 0.35 <5 7 0.8 <5 

PMT06-2 <5 1 59.6 <0.5 0.6 <0.5 0.36 <5 10 1 6 

PMT06-3 8 <1 25.8 <0.5 <0.1 <0.5 0.06 8 2 <0.5 9 

07PM1 0.2 <0.1 20.2 0.1 <0.2 0.4 0.1 1 1.1 0.2 <1 

07PM2 2.3 0.5 114 0.1 3.1 1.2 1.1 18 6.1 2.8 5 

07PM4 1.7 0.5 181 <0.1 4.2 0.3 1.7 15 10.7 2.7 2 

07PM6 2.3 0.5 135 <0.1 3.7 6 1.8 21 7.5 4.2 8 

07PM8 0.3 <0.1 45.5 <0.1 0.4 0.3 0.1 1 0.6 0.4 3 

07PM9 2.3 0.3 114 <0.1 2.2 0.5 0.8 10 8.5 2.9 3 

07PM10 2.5 0.4 104 0.1 2.5 0.7 0.8 14 14.4 2 11 

07PM11 0.2 <0.1 19.2 <0.1 <0.2 0.2 <0.1 1 0.7 0.2 <1 

07PM14 3.4 1.2 285 <0.1 8.3 0.5 2.2 25 59.4 5.4 9 

07PM12 2 0.8 45.6 <0.1 3.2 0.4 1.6 6 28.9 2.6 2 

07-BA-20 0.5 0.2 129 0.1 0.4 1.8 0.2 5 0.7 0.3 6 

07-BA-20A 1.2 0.4 116 <0.1 2 4.7 0.8 13 2.6 1.6 6 
Table 1-9. Minor element concentrations in rock samples from the Paramount-Bald Peak alteration zone.—Continued[Hg, mercury; HgS, mercury sulfide; mm, millimeter; cb, cinnabar; py, pyrite; —, no data]

Sample 

number Latitude Longitude Description1 Location Au ppm Hg ppm 

07-BA-21 38.2767 –119.0567 Altered tuff, Paramount Mine Paramount Mine hill 0.015 0.12 

07-BA-22 38.2767 –119.0567 Banded chalcedony vein with local bladed texture, Paramount Mine Paramount Mine hill 0.741 5.03 

07-BA-24 38.2778 –119.0577 Chalcedony vein in open cut, Paramount Mine Paramount Mine hill 0.057 16.3 

07-BA-25 38.2788 –119.0591 Leached, silicified pumiceous tuff, Paramount Mine dump Paramount Mine hill 0.054 213 

08-BA-13 38.27807 –119.05771 Leached pumice-rich tuff Paramount Mine hill 0.017 0.24 

08PT1 38.2675 –119.0642 Quartz-carbonate SW Paramount hill 0.017 0.57 

08PT2 38.2675 –119.0642 Argillically-altered, unwelded tuff SW Paramount hill <0.005 1.77 

08PT3 38.2679 –119.0640 Breccia with silicified quartz vein SW Paramount hill 0.089 1.42 

08PT4 38.2682 –119.0634 Chalcedony-quartz veins SW Paramount hill 1.99 4.16 

08PT6 38.2688 –119.0615 Black silicified tuff SW Paramount hill 0.033 1.37 

08PT9 38.2686 –119.0593 Quartz vein adjacent to waste pile SW Paramount hill 0.422 34.4 

08PT11 38.2683 –119.0564 Porphyritic block of dacite breccia SW Paramount hill 0.022 0.02 

08PT13 38.2680 –119.0667 Banded chalcedony vein with sulfides in dacite breccia SW Paramount hill 0.21 14.4 

08PT14 38.2701 –119.0666 Chalcedonic banded vein cutting breccia SW Paramount hill 0.2 0.26 

08PT15 38.2713 –119.0686 Tuff with red-brown matrix SW Paramount hill 0.03 2.63 

09-BA-59 38.2682 –119.0606 Silicified tuff locally with cinnabar SW Paramount hill 0.125 10.2 

09-BA-60 38.2682 –119.0627 3-inch banded white quartz vein with carbonate pseudomorphs; local finegrained pyrite SW Paramount hill 1.68 2.85 

09-BA-60A 38.2682 –119.0627 3-inch banded white quartz vein with carbonate pseudomorphs; local finegrained pyrite SW Paramount hill 2.05 0.75 

08PT16 38.2699 –119.0515 Silicified tuff breccia with black matrix South Paramount Mine 

hill

<0.005 0.01 

08PT7C 38.2731 –119.0570 Quartz vein with carbonate pseudomorphs South Paramount Mine 

hill

<0.005 0.24 

09-BA-51 38.26194 –119.04214 Hydrothermally brecciated silicified tuff; possible vent for laminated sinter? SW Paramount basin 0.016 0.12 

09-BA-52 38.2651 –119.0449 Silicified conglomeratic breccia; locally hematite rich SW Paramount basin 0.125 0.37 

08-BA-17 38.27596 –119.03622 Silicified breccia SW Paramount basin <0.005 3.83 

08-BA-18 38.27651 –119.03602 Prospect pit in silicified breccia with cinnabar + barite(?) SW Paramount basin <0.005 1,290 

10-BA-32 38.26275 –119.03353 Silicified knob with strong E-W jointing SW Paramount basin <0.005 0.99 

10-BA-33 38.26275 –119.03353 Pumice-rich tuff SW Paramount basin <0.005 0.26 
Table 1-9. Minor element concentrations in rock samples from the Paramount-Bald Peak alteration zone.—Continued [Hg, mercury; HgS, mercury sulfide; mm, millimeter; cb, cinnabar; py, pyrite; —, no data] Sample number K% Mg% Na% S% Ti % Ag ppm As ppm Ba ppm Be ppm Bi ppm Cd ppm Ce ppm 

07-BA-21 4.2 0.02 0.04 0.02 0.07 <1 22 941 3.6 0.05 <0.1 42

07-BA-22 1 0.02 0.03 0.04 0.03 13 89 657 19.6 <0.04 0.2 7

07-BA-24 0.12 <0.01 0.03 0.03 0.03 <1 89 1,530 10.3 <0.04 <0.1 6

07-BA-25 0.08 <0.01 0.02 0.03 0.22 <1 7 1,030 4.6 <0.04 <0.1 7

08-BA-13 0.1 0.03 0.02 0.04 0.13 <1 63 413 2.7 0.16 0.2 43 

08PT1 1.86 0.03 0.05 0.02 0.08 <1 324 436 5.3 0.06 0.2 28

08PT2 4.15 0.12 0.08 0.04 0.33 <1 387 907 2.6 0.07 <0.1 27

08PT3 0.27 0.05 0.02 0.05 0.03 <1 57 339 7.6 <0.04 <0.1 14

08PT4 1.6 0.02 0.03 0.06 0.05 7 116 714 6.2 <0.04 <0.1 11 

08PT6 5.65 0.03 0.07 0.05 0.1 <1 270 1,830 2.8 0.08 <0.1 53

08PT9 0.15 0.01 0.01 0.14 <0.01 <1 896 1,460 12.6 0.09 <0.1 4

08PT11 5.58 0.09 0.46 0.01 0.19 <1 73 1,820 1.8 <0.04 <0.1 48 

08PT13 0.91 0.02 0.03 0.65 0.04 1 133 291 2 <0.04 <0.1 6

08PT14 2.01 0.02 0.03 0.12 0.08 <1 128 373 3.4 <0.04 <0.1 16

08PT15 5.81 0.09 0.08 0.11 0.24 <1 13 1,460 3.1 0.06 0.1 54

09-BA-59 1.41 0.06 0.02 0.58 0.1 <1 4,000 2,540 4.2 <0.04 <0.1 17

09-BA-60 0.71 0.01 <0.01 0.3 0.04 5 696 605 3.3 <0.04 <0.1 8

09-BA-60A 0.38 <0.01 <0.01 <0.01 0.02 1 79 150 3.6 <0.04 <0.1 3

08PT16 0.17 0.01 0.12 0.09 0.7 <1 15 1,490 0.2 0.45 <0.1 9

08PT7C 3.75 0.45 0.04 0.03 0.31 <1 222 740 3.7 0.1 <0.1 80

09-BA-51 0.1 0.02 0.01 0.07 0.48 <1 23 367 0.7 0.24 0.2 14

09-BA-52 0.08 0.02 0.02 0.1 0.46 <1 151 957 0.8 0.16 <0.1 14

08-BA-17 0.04 0.01 <0.01 0.15 0.62 <1 219 4,440 0.5 0.51 0.1 5

08-BA-18 0.03 <0.01 <0.01 0.04 0.26 <1 14 1,180 0.5 0.22 <0.1 2

10-BA-32 0.06 <0.01 0.01 0.07 0.29 <1 66 758 0.7 0.06 <0.1 53

10-BA-33 0.08 0.01 <0.01 0.19 0.07 <1 133 223 0.6 0.38 <0.1 30
Table 1-9. Minor element concentrations in rock samples from the Paramount-Bald Peak alteration zone.—Continued[Hg, mercury; HgS, mercury sulfide; mm, millimeter; cb, cinnabar; py, pyrite; —, no data]

Sample 

number

Cs

ppm

Cu

ppm

Ga

ppm

In

ppm

La

ppm

Li

ppm

Mn

ppm

Mo

ppm

Nb

ppm

Ni

ppm

P

ppm

Pb

ppm

07-BA-21 18 2 7.6 <0.02 22.5 83 72 0.2 2.5 0.6 150 14.3 

07-BA-22 29 6 21.2 <0.02 4.2 79 41 0.36 0.8 2.4 70 4 

07-BA-24 22 5.4 12.3 <0.02 4 39 27 0.21 0.1 1.7 <50 2.7 

07-BA-25 11 4.6 2.27 <0.02 4.1 79 67 0.27 1.5 1.3 <50 6.8 

08-BA-13 6 6.3 11.8 0.03 24.3 49 170 0.62 8.5 2.3 330 13.3 08PT1 7 18.4 4.44 <0.02 18.8 111 175 0.93 1.3 7.5 1,080 6.3 

08PT2 21 11.9 11.7 0.03 15 90 31 0.35 7 0.5 140 9.2 

08PT3 30 4.3 2.71 <0.02 6.7 121 22 1.57 0.3 1.2 130 2.4 08PT4 10 6.7 4.02 <0.02 6.1 101 59 0.88 0.6 2.5 380 4.1 08PT6 11 6.2 11 0.03 32.1 58 39 0.67 2.9 1.2 590 11.7 

08PT9 <5 8.2 3.47 <0.02 1.5 48 28 2 <0.1 1.3 280 1.3 

08PT11 11 13 18 0.03 26.9 16 96 0.48 3.5 2.7 920 15.8 

08PT13 12 7.2 2.03 <0.02 4.2 139 33 0.4 0.6 <0.5 540 8.4 08PT14 15 4.3 6.48 <0.02 8.7 59 23 0.41 1.8 1.1 210 4.2 08PT15 15 13.3 11.4 0.03 32.3 90 97 0.41 6.2 3.8 470 12.1 09-BA-59 24 105 4.4 <0.02 8.8 90 35 0.93 2.4 0.5 490 5.4 

09-BA-60 8 3.7 4.98 <0.02 3.7 81 28 2.34 0.3 <0.5 80 3.4 

09-BA-60A <5 3 4.77 <0.02 1.8 84 54 0.48 0.1 1.1 80 2.4 

08PT16 32 5.2 1.02 <0.02 5.6 1 12 2.29 18.5 6.2 150 17.4 

08PT7C 56 3.5 16.4 0.04 41 36 93 0.6 12 1.2 1,640 19.7 

09-BA-51 6 18.4 3.1 <0.02 7.8 45 161 2.44 8.5 1.6 940 15.4 

09-BA-52 <5 12.5 4.01 <0.02 7 33 98 4.38 9.7 1.1 250 15.7 

08-BA-17 <5 11.2 0.98 <0.02 4.3 25 74 2.38 23.8 2.9 360 6.2 

08-BA-18 <5 4.9 0.89 <0.02 2 17 36 0.61 9 0.8 <50 5 

10-BA-32 6 5.4 10.8 <0.02 29.6 42 25 4.23 8 0.7 170 8.7 

10-BA-33 6 7.7 11.4 <0.02 16.3 48 31 1.98 13.8 0.6 150 17.9 
Table 1-9. Minor element concentrations in rock samples from the Paramount-Bald Peak alteration zone.—Continued [Hg, mercury; HgS, mercury sulfide; mm, millimeter; cb, cinnabar; py, pyrite; —, no data] Sample number Sc ppm Sn ppm Sr ppm Te ppm Th ppm Tl ppm Uppm Vppm Wppm Yppm Zn ppm 

07-BA-21 1.3 0.7 54.8 <0.1 6.3 1.9 2.1 25 2 4.1 9 

07-BA-22 1 0.3 121 <0.1 1.2 1.7 0.5 72 2.6 1.5 20 

07-BA-24 0.9 0.2 74.4 <0.1 1.3 0.4 0.8 18 9.8 0.9 4 

07-BA-25 2.2 0.5 50.6 <0.1 4.1 0.2 1.8 5 2.3 2.5 2 

08-BA-13 2.7 1.1 69.9 0.1 13.2 0.1 4.3 29 16.6 10.1 19 

08PT1 3.2 0.3 114 <0.1 2.5 1.7 1.7 33 3.3 5.3 83 

08PT2 7 1.3 62.2 <0.1 8 5.4 2.8 70 10.6 6.8 6 

08PT3 1.3 0.3 92.7 <0.1 1.2 1.1 0.4 16 1.3 1.6 3 

08PT4 1.5 0.3 102 <0.1 1.3 1.6 0.6 12 2.4 1.5 9 

08PT6 3.2 0.9 195 <0.1 5.4 7.3 1.8 37 3.5 5.7 22 

08PT9 0.9 <0.1 67.7 <0.1 0.2 13.7 0.5 8 16.7 2.2 14 

08PT11 5.9 0.8 356 <0.1 8.1 10.8 2.6 55 13.3 5.1 21 

08PT13 1.8 0.3 87.1 <0.1 0.9 3.7 1 17 2.5 0.9 2 

08PT14 2.3 0.3 106 <0.1 2.1 2.1 0.9 25 4.8 2.2 5 

08PT15 5.2 1.2 314 <0.1 8.4 8 3.1 49 7.4 14.7 53 

09-BA-59 2.1 0.7 240 <0.1 3.2 6.8 1.7 17 4.3 3.4 3 

09-BA-60 0.8 0.8 77.6 <0.1 1 3.8 0.4 6 1.1 1.6 1 

09-BA-60A 0.5 0.3 41 <0.1 0.5 0.4 0.2 5 0.7 0.7 3 

08PT16 3.5 3.3 101 0.1 6 1.7 3.8 10 1.3 2.4 3 

08PT7C 6.9 1.9 60.7 <0.1 14.2 5.5 4.9 30 13.7 11.9 22 

09-BA-51 1.5 2 82.9 0.3 4.9 0.2 4.3 27 37.2 3.3 9 

09-BA-52 1.4 1.4 70.3 <0.1 7.7 0.2 3.4 53 83.3 4.2 6 

08-BA-17 5.7 2.5 123 0.2 5.4 <0.1 6.2 38 27.7 9.4 13 

08-BA-18 2.2 0.8 44.5 0.2 4 <0.1 3.5 5 5.4 3 15 

10-BA-32 4.4 1.1 79.5 0.1 14.2 5.5 4.1 62 21.9 7.4 3 

10-BA-33 1.7 0.7 65.8 0.2 20.9 1.2 4 16 6.4 4.5 4 
Table 1-10. Minor element concentrations in rocks samples from the Cinnabar Canyon-US 395 alteration zone.[alt, alteration; DDH, diamond drill hole; Fe, iron; FeOx, iron oxide; HgS, mercury sulfide; K, potassium; RDH, rotary drill hole; S, sulfur]

Sample 

number Description Latitude Longitude Au ppm Hg ppm Al % Ca% Fe% 

CCD7 Cinnabar Canyon S resource DDH 38.19268 –119.1597 0.084 28.9 0.07 0.02 1.62 CCD8B Cinnabar Canyon S resource DDH 38.19087 –119.1597 0.018 42.6 0.07 0.05 2.16 CCD16 Cinnabar Canyon S resource DDH 38.19317 –119.16045 0.014 84.1 0.14 0.05 3.96 07-BA-10 S resource RDH cuttings, opal-montmorillonite-altered 

porphyritic dacite

38.18924 –119.15404 <0.005 0.24 0.44 0.03 0.58 

07-BA-11 Silicified volcaniclastic breccia 38.18967 –119.15578 <0.005 0.14 0.08 0.02 0.05 

07CC1 Calmono Hg Mine; HgS in altered andesite 38.18625 –119.15728 0.037 92 8.62 0.22 0.97 07CC2 Calmono Hg Mine; HgS in altered andesite opal 38.18625 –119.15728 <0.005 337 8.18 0.16 2.14 

07CC5 Calmono Hg Mine; calcines from Hg mine 38.18625 –119.15728 0.006 21.6 8.67 0.58 4.99 07CC6 Calmono Hg Mine; sulfide in white opal 38.18625 –119.15728 <0.005 0.71 0.26 0.06 0.54 

07-BA-8 Cinnabar Canyon, argillized/opal-altered porphyritic dacite 38.2765 –119.16040 0.03 0.11 9.12 0.13 0.42 

07-BA-9 Silicified, Fe-oxide-rich breccia, Cinnabar Canyon 38.2736 –119.13960 0.009 66.5 0.36 0.04 6.14 

07-BA-14 Argillized andesite with opal pods, Cinnabar Canyon 38.2907 –119.1406 <0.005 181 7.81 0.12 3.63 07-BA-16 Quarry in acid-leached breccia, mouth of Cinnabar Canyon 38.2984 –119.1387 <0.005 0.55 0.44 0.05 0.23 08CC3 Argillic-leached lithic tuff 38.17418 –119.1523 <0.005 0.03 9.59 0.1 1.33 08CC4 Biotite rhyolite porphyry flow 38.17166 –119.15484 <0.005 0.01 7.42 1.35 1.23 08CC5 Plagioclase-K-feldspar dacite porphyry 38.17445 –119.15487 <0.005 <0.01 7.68 3.04 3.12 08CC6 Porphyritic andesite with fractures 38.17403 –119.15355 <0.005 0.03 0.51 0.06 2.16 

08CC7 Fault zone in dacite breccia 38.18449 –119.15257 <0.005 0.04 3.42 0.14 2.12 08CC8 Andesite porphyry with plagioclase phenocrysts 38.18832 –119.14996 <0.005 0.21 0.13 0.02 2.76 

08CC9 Knob of opalized porphyritic andesite 38.18931 –119.14887 <0.005 0.07 0.27 0.05 0.31 08CC10 Partially leached dacite porphyry 38.19052 –119.14950 <0.005 0.01 7.19 0.69 2.29 

08CC11 Opalized andesite 38.18790 –119.14996 <0.005 0.15 0.18 0.03 0.63 

08CC12 South end of opalite hill 38.18754 –119.14703 <0.005 0.15 1.38 0.09 0.43 

08CC13 White opal cutting opalized porphyritic andesite 38.18605 –119.15802 <0.005 0.05 6.02 0.1 1.02 

08CC14 Hematite and goethite cemented breccia 38.19149 –119.15797 <0.005 10.2 1.26 0.06 23.6 

08CC15B Altered 38.19207 –119.15808 <0.005 57.7 0.2 0.03 2.09 

08CC16 Massive chalcedony breccia 38.19147 –119.15773 <0.005 0.13 0.13 <0.01 0.06 

08CC17 Andesite with fractures filled by opal 38.19324 –119.15959 0.008 15.6 0.13 0.03 3.34 

08CC21 Andesite with plagioclase phenocrysts 38.19104 –119.15895 <0.005 106 0.06 <0.01 4.19 

08CC22 Kaolinite north of road with some pyrite 38.19871 –119.17207 <0.005 0.08 6.34 0.39 1.01 

08CC23 Tan opalite/porphyritic dacite 38.18489 –119.17728 <0.005 0.04 0.34 0.1 0.82 

08CC24 Opalite-chalcedony 38.18813 –119.17698 <0.005 0.48 0.08 0.02 0.08 

08CC25 Opalite brecciated chalcedony with sulfides 38.18680 –119.17733 0.028 0.67 0.33 0.02 0.19 

39509-3 White-beige, quartz-clay-alunite-altered volcaniclastics, US 395 

layback

38.20793 –119.22751 <0.005 1.28 2.11 0.08 0.84 

39509-6 Quartz-clay-alunite-altered porphyritic volcanic rock, Hot Springs 

Canyon

38.22064 –119.19188 <0.005 1.41 8.23 0.36 3.18 

39509-8 Quartz-clay-altered porphyritic volcanic rock, Hot Springs Canyon 38.21008 –119.1871 <0.005 1.97 5.63 0.14 3.29 39509-9 Brown, coarse volcaniclastics, minor FeOx, upper Hot Springs 

Canyon

38.2056 –119.18252 <0.005 4.96 7.94 0.93 2.63 
Table 1-10. Minor element concentrations in rocks samples from the Cinnabar Canyon-US 395 alteration zone.—Continued [alt, alteration; DDH, diamond drill hole; Fe, iron; FeOx, iron oxide; HgS, mercury sulfide; K, potassium; RDH, rotary drill hole; S, sulfur] Sample number S% Ti % Ag ppm As ppm Ba ppm Be ppm Bi ppm Cd ppm Ce ppm Co ppm Cr ppm Cs ppm Cu ppm 

CCD7 1.87 0.39 17 50 428 <0.1 50.6 0.2 2.59 32.1 9 <5 53.3 

CCD8B 2.42 0.71 2 32 164 <0.1 67.3 0.2 0.72 35.7 7 <5 31.7 

CCD16 4.58 1.08 20 68 49 <0.1 125 0.6 2.47 25.3 16 <5 111 

07-BA-10 0.75 0.76 <1 53 1,650 <0.1 1.62 0.4 5.49 4.4 4 <5 20.2 

07-BA-11 0.02 0.41 <1 3 584 <0.1 12 <0.1 0.47 0.1 2 <5 4.1 

07CC1 0.08 0.67 <1 16 1,630 2.3 0.11 <0.1 101 0.6 43 <5 5.7 

07CC2 0.32 0.62 1 30 1,180 2.2 0.1 <0.1 92.3 1.1 39 <5 40.6 

07CC5 0.13 0.57 <1 92 1,240 1.7 1.55 0.1 67.3 3.3 65 <5 43.4 

07CC6 0.2 0.46 3 129 407 0.1 0.85 0.2 4.63 1.8 6 <5 4.2 

07-BA-8 0.42 0.39 2 3 1,810 0.5 0.35 0.5 57.1 0.9 96 <5 48.2 

07-BA-9 0.06 0.9 <1 33 995 0.5 87.7 0.2 5.68 9.4 23 <5 67.8 

07-BA-14 1 0.55 <1 49 1,640 1.5 0.34 <0.1 71.1 1.1 54 <5 52.7 

07-BA-16 0.13 0.47 <1 32 3,920 <0.1 0.21 <0.1 6.18 0.2 8 9 4.1 

08CC3 7.14 0.28 <1 252 306 0.2 0.13 <0.1 43.4 0.2 23 14 7.6 

08CC4 0.04 0.14 <1 6 1,970 2.3 0.16 <0.1 39.1 3 2 <5 9.6 

08CC5 0.03 0.35 <1 2 1,300 2.7 0.06 <0.1 71 15.5 75 <5 17.3 

08CC6 0.08 0.36 <1 396 504 <0.1 0.17 0.1 9.17 0.7 10 12 17.7 

08CC7 0.1 0.53 <1 190 542 0.5 0.29 0.3 8.96 2.5 38 5 23.9 

08CC8 1.79 0.62 <1 298 1,870 <0.1 44.7 1.3 1 24.2 24 <5 12.2 

08CC9 0.31 0.48 <1 14 2,460 <0.1 10.8 0.1 3.88 11 7 <5 7.2 

08CC10 0.14 0.46 <1 9 2,200 1.4 0.16 <0.1 86.7 3.3 100 5 15.8 

08CC11 0.35 0.7 <1 124 3,490 <0.1 30 0.2 2.46 13 16 <5 11.5 

08CC12 0.3 1.04 <1 28 1,630 0.3 52.3 <0.1 34.9 0.9 18 <5 5.4 

08CC13 4.23 0.62 <1 84 1,510 0.5 0.12 <0.1 44.2 0.7 28 <5 69.5 

08CC14 0.27 1.47 <1 38 1,810 1.7 14.7 0.3 22.5 3.1 77 <5 174 

08CC15B 2.75 0.47 8 74 438 0.1 216 0.2 1.77 19.2 19 <5 14.2 

08CC16 0.02 0.48 <1 <1 296 0.1 0.64 <0.1 2.17 0.2 12 <5 2.3 

08CC17 3.78 1.26 10 31 273 0.3 32.8 0.1 3.86 15 10 <5 45.4 

08CC21 4.47 0.91 7 37 242 0.1 101 0.3 2.38 44.4 17 <5 27.9 

08CC22 0.19 0.39 <1 15 1,770 1.4 0.26 <0.1 61.6 0.7 21 <5 8.5 

08CC23 0.18 1.01 <1 78 5,880 0.1 0.2 <0.1 1.75 0.5 13 <5 6.9 

08CC24 0.06 0.15 <1 1 1,200 <0.1 0.06 <0.1 1.25 0.4 1 <5 1.8 

08CC25 0.4 3.47 <1 3 8,120 <0.1 0.06 <0.1 1.72 0.1 44 <5 6.2 

39509-3 1.85 0.26 <1 15 632 0.2 0.28 <0.1 20.9 0.2 10 <5 3.9 

39509-6 0.74 0.4 <1 31 1,450 1.6 0.53 <0.1 85.2 0.6 12 7 15.2 

39509-8 2.4 0.38 <1 28 346 0.7 0.79 <0.1 50.7 1.4 6 <5 16.7 

39509-9 1 0.48 <1 14 1,260 2.2 0.45 <0.1 53.6 1.9 25 6 16.6 
Table 1-10. Minor element concentrations in rocks samples from the Cinnabar Canyon-US 395 alteration zone.—Continued[alt, alteration; DDH, diamond drill hole; Fe, iron; FeOx, iron oxide; HgS, mercury sulfide; K, potassium; RDH, rotary drill hole; S, sulfur]

Sample 

number

In

ppm

La

ppm

Li

ppm

Mn

ppm

Mo

ppm

Nb

ppm

Ni

ppm

P

ppm

Pb

ppm

Rb

ppm

Sb

ppm

Se

ppm

CCD7 0.03 1 5 23 2.42 11.3 43.6 <50 63.2 0.4 63.6 —

CCD8B <0.02 <0.5 4 25 2.4 14.3 42.3 <50 88.8 0.5 72.5 —

CCD16 0.08 1.5 3 81 2.24 24.7 32.3 60 185 1.1 84.7 —

07-BA-10 0.03 2.9 2 9 2.03 17.3 15.5 120 266 1.8 22.2 —

07-BA-11 <0.02 <0.5 12 9 0.65 8.7 1 60 3.5 0.4 8.65 —

07CC1 <0.02 47.3 24 23 3.44 13.9 1.7 1,560 20.2 82.3 3.73 —

07CC2 0.04 44.2 17 38 3.19 11.3 2.4 1,520 21.3 30.4 3.39 —

07CC5 0.06 33.4 11 64 3.23 11.6 6.3 1,050 7,510 41.5 53.3 —

07CC6 0.02 3 <1 12 1.42 6.2 2.7 180 71.3 3.6 4.17 —

07-BA-8 0.06 31 11 17 1.44 9.4 5.1 1,790 82.6 3.3 19.2 —

07-BA-9 0.04 3.8 3 96 4.25 14.1 15.5 760 82.3 3.9 106 25.7

07-BA-14 0.07 38.9 22 25 2.52 10.2 3 1,050 29.5 33.6 4.39 <0.2

07-BA-16 <0.02 3.2 <1 15 3.21 9 1.6 150 16.1 10.6 0.83 —

08CC3 0.1 19.2 1 5 8.41 8.8 1.2 1,840 30.6 106 0.73 —

08CC4 <0.02 21.2 23 262 1.59 5.5 2.5 510 36.3 85.5 1.01 —

08CC5 0.03 36.4 16 416 0.91 9.9 71.5 1,540 20.2 102 0.56 —

08CC6 0.07 5.6 <1 6 4.55 10.7 5.4 330 45.9 12.7 0.76 —

08CC7 0.09 5.7 2 70 8.36 12.5 20.6 640 136 7.5 1.3 —

08CC8 0.1 0.8 <1 6 2.31 15.3 19.6 130 239 1.6 162 —

08CC9 <0.02 2.1 <1 7 1.82 8.7 15.7 230 25.6 2.5 14.1 —

08CC10 0.04 44.3 3 73 7.82 10.9 16.1 1,550 21 91.6 1.15 —

08CC11 <0.02 1.8 <1 6 31.4 7.1 30.3 950 107 1.8 67.8 —

08CC12 0.04 22.1 3 23 6.45 22.8 2.4 1,070 140 9.7 34.7 —

08CC13 0.15 30.9 2 19 2.47 10.4 2.4 1,320 81.1 8.7 0.83 —

08CC14 0.16 16.1 3 103 16 31 5.7 2,180 171 2 43.6 —

08CC15B <0.02 1.2 3 9 2.1 9.9 34.9 80 174 3.1 231 —

08CC16 <0.02 1.4 4 6 0.7 10.5 0.6 160 3.4 0.4 3.71 —

08CC17 <0.02 2.2 3 22 1.74 24.1 17.3 <50 107 1.5 59.1 —

08CC21 <0.02 0.9 6 65 1.99 13.1 46.5 50 237 0.6 111 —

08CC22 0.03 36 4 28 1.74 13.1 1.5 1,020 25.4 78.2 0.83 —

08CC23 <0.02 1.3 <1 23 5.33 18.2 1.3 140 67.4 3.7 8.31 —

08CC24 <0.02 0.9 <1 18 0.82 2.7 0.9 <50 2.7 0.8 0.44 —

08CC25 <0.02 1.9 <1 6 15.3 64.7 0.7 110 11.9 1.1 1.02 —

39509-3 <0.02 9.7 <1 <5 1.24 4.3 0.8 430 6.1 5.3 1.93 —

39509-6 0.05 39.6 9 25 2.23 11.5 2.4 2,870 21.9 52 3.74 —

39509-8 0.05 29.1 5 24 1.79 10.9 2.7 1,340 23.1 22.8 2.19 —

39509-9 0.04 31 4 102 1.99 13.5 2.8 1,200 21.5 109 1.69 —
Table 1-10. Minor element concentrations in rocks samples from the Cinnabar Canyon-US 395 alteration zone.—Continued [alt, alteration; DDH, diamond drill hole; Fe, iron; FeOx, iron oxide; HgS, mercury sulfide; K, potassium; RDH, rotary drill hole; S, sulfur] Sample number Sc ppm Sn ppm Sr ppm Te ppm Th ppm Tl ppm Uppm Vppm Wppm Yppm Zn ppm CCD7 1.4 4.8 29.7 4.3 0.9 2 2.2 4 2.5 1.2 9 CCD8B 0.7 9.3 16.8 1.8 1 3.4 1.4 5 2.9 0.6 3 CCD16 3.1 6.5 42.2 2.2 1.5 6.4 4.3 9 7.2 3.4 12 07-BA-10 4.2 2.8 64.4 1.9 3.3 5.9 5.9 16 7.2 7 6 07-BA-11 0.6 3.2 4.6 0.2 0.3 <0.1 1.3 4 1.1 0.2 1 07CC1 14 2.5 719 <0.1 12.4 0.6 4.7 153 3.6 18.8 7 07CC2 16.2 2.1 657 <0.1 16.4 0.8 4.7 153 2.5 21 8 07CC5 16.6 2 388 0.2 17.1 0.9 4.4 173 3.4 9.2 30 07CC6 1.9 2.1 112 2.8 1.4 2.7 2.9 10 2.7 0.4 1 07-BA-8 17.3 1.2 1,180 1 12.9 0.1 2.8 167 1.4 3.2 43 07-BA-9 4 13.9 51.4 7 3.7 0.1 5.1 15 1.3 3.4 17 07-BA-14 15.5 1.8 420 0.2 24.5 1.3 4.9 192 1.9 11.4 12 07-BA-16 1.2 1 71.8 0.1 3.1 1.1 1.8 14 1.7 0.7 4 08CC3 8.7 1.1 1,640 0.5 12 20.1 1.8 149 1.3 2.1 5 08CC4 3 0.8 869 <0.1 6 0.5 2.2 28 2.3 5.9 44 08CC5 12.1 1.2 829 <0.1 14.8 0.7 5.3 107 0.9 14.4 62 08CC6 2.1 2.2 144 0.3 3.3 3.7 3.6 14 1.7 0.6 3 08CC7 3.3 2 77.8 0.2 3.5 1.4 5.2 66 1.9 2.5 23 08CC8 3.1 8.1 17.8 6.1 0.7 9.8 3.4 7 2.5 0.1 4 08CC9 2 4 193 1.8 1.4 1.7 1.5 6 1.1 0.9 2 08CC10 18.7 1.2 945 <0.1 14.6 0.4 6.6 155 2.3 12.3 23 08CC11 8.9 18.7 57.6 5.6 0.8 3 6.1 5 12 0.2 7 08CC12 5.8 5 1,070 8.7 31.1 1.5 5.8 23 12.2 3 10 08CC13 9.5 1.8 794 <0.1 11.1 0.5 8 94 1.8 4.3 10 08CC14 4.9 27.2 1,330 0.7 5.7 <0.1 6 90 5 3.8 43 08CC15B 1.5 7.8 50.1 4.8 0.8 10.9 1.4 5 9.3 0.6 6 08CC16 1 6.2 12.2 <0.1 0.3 <0.1 0.8 4 0.8 0.3 1 08CC17 2 4.4 60 0.8 1.7 1.3 2.6 14 6.1 1.4 4 08CC21 0.8 8.4 37.4 3.4 0.7 5.6 1 5 2.3 0.6 8 08CC22 8.4 1.6 342 1.1 16.3 1.4 5.5 64 1.5 7.8 10 08CC23 3.1 2 58.9 3.7 2.3 1.3 8.3 33 2.2 2.5 3 08CC24 0.4 0.2 48.7 <0.1 <0.2 <0.1 0.1 3 0.4 0.3 <1 08CC25 1.9 2.5 89.9 <0.1 0.9 <0.1 0.9 16 3.8 0.3 2 39509-3 2.3 0.7 186 0.7 2.9 0.1 0.9 40 1.1 1.3 3

39509-6 7.7 1.6 1,380 0.4 13.6 0.3 4.4 101 1.8 7.3 24

39509-8 5.5 1.4 885 0.7 10.7 0.7 3.4 51 1.2 1.9 15

39509-9 12.6 1.4 730 1.3 15 0.8 5.3 118 1.7 9.2 23
Table 1-11. Minor element concentrations in rock samples from the Bodie Mining District.[cm, centimeter; K, potassium; Kspar, potassium feldspar; —, no data]

Sample 

number Description, Location Latitude Longitude Au ppm Hg ppm Al % Ca% Fe% 

% 

Sinter

BODB06-4A Sinter, silicified volcaniclastics, Bodie Bluff 38.21883 –119.99921 0.011 0.44 0.36 0.04 0.07 0

BODB06-4B1 Sinter, silicified volcaniclastics, Bodie Bluff 38.21883 –119.99921 0.014 0.23 0.45 0.08 0.18 0

BODB06-4B2 Sinter, silicified volcaniclastics, Bodie Bluff 38.21883 –119.99921 0.01 0.42 0.44 0.07 0.17 0

07-BA-3A Sinter block, Bodie Bluff 38.21923 –118.99823 0.007 0.15 0.35 0.04 0.15 0

07-BA-3B Sinter block, Bodie Bluff 38.21923 –118.99823 0.008 0.09 0.16 0.02 0.05 0

BB13-SINA Dismembered sinter, Bodie Bluff summit 38.21924 –118.99822 0.051 0.06 0.38 0.02 0.11 0

BB13-SINB Dismembered sinter, Bodie Bluff summit 38.21924 –118.99822 0.004 0.01 0.15 0.02 0.07 0

BB13-CLD Sinter clast in volcaniclastic deposits, Bodie Bluff summit 38.21883 –119.99921 0.008 0.01 0.1 0.01 0.07 0

BB13-CLH Sinter clast in volcaniclastic deposits, Bodie Bluff summit 38.21881 –119.9992 0.051 <0.01 0.16 0.07 0.05 0

BB13-CLI Sinter clast in volcaniclastic deposits, Bodie Bluff summit 38.21841 –119.99921 0.018 <0.01 0.08 0.04 0.05 0

BB13-CLK Sinter clast in volcaniclastic deposits, Bodie Bluff summit 38.21883 –119.99919 0.002 <0.01 0.11 0.05 0.05 0BB13-CLL Sinter clast in volcaniclastic deposits, Bodie Bluff summit 38.21884 –119.99921 0.002 <0.01 0.12 0.03 0.11 0

Incline series veins

BB13-VEINA Incline veins next to sinter, Bodie Bluff summit 38.21975 –118.99942 0.965 0.02 1.41 0.04 0.1 2

BB13-VEINB Incline veins next to sinter, Bodie Bluff summit 38.22047 –118.99931 >10 0.07 1.13 0.05 0.06 1

BODB06-3 Banded quartz vein, dump, Bodie Bluff 38.21783 –119.99832 5 0.54 0.15 <0.01 0.02 0

11-BA-26A Vein, Upper Hobart Tunnel dump, Bodie Bluff 38.21968 –119.00265 5.93 0.08 2.61 0.09 0.38 2

11-BA-26B Vein, Upper Hobart Tunnel dump, Bodie Bluff 38.21968 –119.00265 146 2.97 1.91 0.04 0.04 2

11-BA-26C Vein, Upper Hobart Tunnel dump, Bodie Bluff 38.21968 –119.00265 107 0.1 3.55 0.06 0.79 4

BOD11-11D Banded quartz-Kspar vein, minor sulfides 38.21497 –119.00273 1.84 1.39 0.81 0.07 0.17 0

BOD11-12 Banded quartz-Kspar vein, minor sulfides 38.21591 –119.003 0.061 0.39 4.08 0.03 0.12 4

BOD11-13 Banded quartz-Kspar vein, minor sulfides 38.21497 –119.00356 12.9 0.1 4.09 0.07 0.99 4

BOD11-14 Banded quartz-K-mica vein, minor fluorite 38.21725 –119.00039 10.1 0.55 1.99 0.04 0.18 2

BOD11-18A Quartz vein, minor sulfide 38.21434 –119.00523 21.2 0.06 1.63 0.03 0.34 1

BOD11-19 Banded quartz-Kspar vein, minor sulfides 38.21872 –119.00031 46 1.96 2.65 0.04 0.07 3

BOD13-1A SW summit Standard Hill 38.21482 –119.00456 4,860 0.12 1.36 0.04 0.14 1

BOD13-2B SW slope Standard Hill 38.21568 –119.00385 2,740 0.09 0.63 <0.01 0.09 0

BOD13-5B Upper Hobart Tunnel dump 38.21971 –119.00266 2,280 0.11 5.52 0.08 2.13 4

BOD13-5C Upper Hobart Tunnel dump 38.21971 –119.00266 >10,000 2.81 5.34 0.02 0.49 2
Table 1-11. Minor element concentrations in rock samples from the Bodie Mining District.—Continued [cm, centimeter; K, potassium; Kspar, potassium feldspar; —, no data] Sample number S% Ti % Ag ppm As ppm Ba ppm Be ppm Bi ppm Cd ppm Ce ppm Co ppm Cr ppm Cs ppm 

Sinter BODB06-4A <0.01 0.01 1 <30 150 <5 <0.1 <0.2 1.6 0.5 <10 25

BODB06-4B1 <0.01 0.02 <1 100 315 <5 <0.1 <0.2 2.7 <0.5 <10 34

BODB06-4B2 <0.01 0.02 <1 90 211 <5 <0.1 <0.2 2.7 <0.5 <10 37

07-BA-3A 0.02 0.02 <1 35 278 1.1 <0.04 <0.1 4.12 0.4 5 23 

07-BA-3B <0.01 <0.01 <1 20 33 0.6 0.04 0.5 2.19 0.2 3 20 

BB13-SINA 0.02 <0.01 <1 22 39 1.6 <0.04 <0.1 3.03 0.6 4 25 

BB13-SINB <0.01 <0.01 <1 16 33 0.6 0.06 <0.1 0.81 0.1 5 21 

BB13-CLD <0.01 <0.01 <1 17 52 0.3 0.09 <0.1 0.33 <0.1 3 6 

BB13-CLH 0.03 <0.01 <1 12 52 2.3 0.14 <0.1 0.73 0.1 4 16 BB13-CLI 0.02 <0.01 <1 15 67 0.4 0.19 <0.1 0.57 <0.1 4 <5 BB13-CLK 0.02 <0.01 <1 12 59 0.2 <0.04 <0.1 0.58 0.2 4 5 BB13-CLL 0.02 <0.01 <1 29 88 0.3 <0.04 <0.1 1.35 0.1 6 9 

Incline series veins BB13-VEINA <0.01 <0.01 37 4 28 0.7 0.05 <0.1 0.88 0.6 2 12 

BB13-VEINB <0.01 <0.01 135 5 27 1.6 0.06 <0.1 0.34 0.7 1 14 

BODB06-3 <0.01 <0.01 <1 <30 31.9 <5 <0.1 <0.2 0.7 <0.5 <10 15

11-BA-26A 0.07 0.09 41 104 1,290 4.4 0.31 <0.1 13.7 0.3 2 23 

11-BA-26B <0.01 <0.01 268 8 86 1.5 0.04 <0.1 0.36 1.2 1 8 

11-BA-26C <0.01 0.06 122 27 250 2.5 0.07 <0.1 7.41 22.6 8 15 

BOD11-11D 0.11 <0.01 17 41 330 4.3 80.8 <0.1 2.74 0.3 1 13 BOD11-12 0.01 <0.01 4 11 497 2.7 8.52 <0.1 8.75 7.6 1 10 

BOD11-13 0.1 0.1 53 71 479 3.1 1.08 <0.1 10.8 3.2 4 9 

BOD11-14 0.01 <0.01 51 17 93 2.8 2.39 <0.1 2.3 0.4 1 11 BOD11-18A 0.23 0.05 800 286 269 1.2 0.39 <0.1 8.37 0.3 2 6 BOD11-19 <0.01 <0.01 153 11 44 5.5 1.93 <0.1 1.24 0.2 <1 11 

BOD13-1A 0.02 <0.01 23 9 78 1.1 0.08 <0.1 3.34 23.1 2 6 

BOD13-2B <0.01 <0.01 11 8 42 0.9 0.07 <0.1 2.02 9.2 2 <5 

BOD13-5B 1.93 0.1 71 949 578 1.5 0.12 <0.1 24.3 2.8 8 18 BOD13-5C 0.01 0.03 254 108 199 1.6 0.07 <0.1 4.53 0.4 3 15 
Table 1-11. Minor element concentrations in rock samples from the Bodie Mining District.—Continued[cm, centimeter; K, potassium; Kspar, potassium feldspar; —, no data]

Sample 

number

In

ppm

La

ppm

Li

ppm

Mn

ppm

Mo

ppm

Nb

ppm

Ni

ppm

P

ppm

Pb

ppm

Rb

ppm

Sinter

BODB06-4A <0.2 1.5 70 — 4 <1 6 — <5 10.1 

BODB06-4B1 <0.2 2.2 100 — 7 <1 13 — <5 19.1 

BODB06-4B2 <0.2 1.9 120 — 7 <1 8 — 8 20.5 

07-BA-3A <0.02 3.1 57 127 2.64 0.3 0.9 <50 1.8 24.5 

07-BA-3B <0.02 5 45 24 3.21 <0.1 1.1 <50 56.5 7.7 

BB13-SINA <0.02 1.6 43 45 4.83 0.1 3.5 <50 1.1 7.5 

BB13-SINB <0.02 <0.5 37 42 4.3 <0.1 1.9 <50 <0.5 5.8 

BB13-CLD <0.02 <0.5 20 34 5.82 <0.1 1.8 <50 <0.5 1.4 

BB13-CLH <0.02 <0.5 36 19 2.55 <0.1 2 <50 1 6.8 

BB13-CLI <0.02 <0.5 9 15 3.11 <0.1 2 <50 <0.5 1.3 

BB13-CLK <0.02 0.6 18 22 3.92 <0.1 2.4 <50 <0.5 1.4 

BB13-CLL <0.02 0.7 17 28 4.12 <0.1 5.8 <50 0.8 2.1 

Incline series veins

BB13-VEINA <0.02 <0.5 88 42 3.47 <0.1 7.7 <50 1.4 116 

BB13-VEINB <0.02 <0.5 87 41 2.77 <0.1 1.9 <50 1.6 77.7 

BODB06-3 <0.2 1 30 — 5 <1 7 — <5 5.3 

11-BA-26A <0.02 6.9 64 17 11.9 2.2 0.6 220 11.8 166 

11-BA-26B <0.02 <0.5 130 24 0.28 <0.1 <0.5 <50 3.5 133 

11-BA-26C <0.02 3.2 128 564 6.07 1.6 14 120 5.8 317 

BOD11-11D <0.02 1.1 101 41 1.63 <0.1 3.1 120 18.6 34.7 

BOD11-12 <0.02 1.9 123 471 1.27 0.2 15.2 <50 10.3 247 

BOD11-13 <0.02 5.8 132 268 0.52 2.2 10 310 7.8 275 

BOD11-14 <0.02 1.3 55 94 5.85 0.1 1.3 70 3.9 161 

BOD11-18A <0.02 5.1 153 24 3.82 1 1 140 13.7 108 

BOD11-19 <0.02 0.8 56 30 0.53 <0.1 0.8 60 5.3 214 

BOD13-1A <0.02 0.9 206 875 1.43 <0.1 12.2 <50 1.9 71.7 

BOD13-2B <0.02 0.6 15 447 0.62 <0.1 8.2 <50 1.3 51.1 

BOD13-5B 0.02 13.5 45 41 6.12 3.3 6.9 430 13.8 373 

BOD13-5C <0.02 3.4 71 24 2.15 0.7 2.2 120 4.5 373 
Table 1-11. Minor element concentrations in rock samples from the Bodie Mining District.—Continued [cm, centimeter; K, potassium; Kspar, potassium feldspar; —, no data] Sample number Se ppm Sn ppm Sr ppm Te ppm Th ppm Tl ppm Uppm Vppm Wppm Yppm Zn ppm 

Sinter BODB06-4A <0.2 <1 43.5 <0.5 0.2 <0.5 0.14 <5 5 0.5 <5 

BODB06-4B1 0.5 <1 66.5 <0.5 0.2 0.9 0.16 10 16 0.9 7 

BODB06-4B2 0.4 <1 70 <0.5 0.2 1.2 0.16 12 16 0.7 8 

07-BA-3A <0.2 0.1 46.7 <0.1 0.7 0.4 0.2 6 4.5 0.7 <1 

07-BA-3B <0.2 <0.1 13.8 0.4 0.3 0.3 0.1 3 3.3 0.7 8 

BB13-SINA <0.2 0.5 20.6 <0.1 0.3 0.3 0.1 5 3.6 0.4 4 

BB13-SINB <0.2 0.2 10.8 <0.1 <0.2 0.1 <0.1 2 2.4 0.3 1 

BB13-CLD <0.2 0.2 6.9 <0.1 <0.2 <0.1 <0.1 3 0.5 0.1 2 

BB13-CLH <0.2 0.5 15.6 <0.1 <0.2 <0.1 <0.1 2 1.8 0.2 5 

BB13-CLI <0.2 0.3 6.6 <0.1 <0.2 <0.1 <0.1 2 0.7 0.2 2 

BB13-CLK <0.2 0.4 10.1 <0.1 <0.2 <0.1 <0.1 2 0.2 0.3 2 

BB13-CLL <0.2 0.3 11.7 <0.1 0.2 <0.1 0.1 5 0.8 0.3 2 

Incline series veins BB13-VEINA 1.9 0.2 86 <0.1 <0.2 1.2 <0.1 2 0.4 0.2 19 

BB13-VEINB 2.2 0.4 101 <0.1 <0.2 1 <0.1 1 0.3 <0.1 10 

BODB06-3 0.2 <1 11.1 <0.5 <0.1 <0.5 <0.05 <5 10 <0.5 9 

11-BA-26A — 0.5 191 0.9 2.1 1.8 0.8 16 4.9 2.4 10 

11-BA-26B — <0.1 101 <0.1 <0.2 1.8 <0.1 <1 <0.1 <0.1 4 

11-BA-26C — 0.6 104 <0.1 1.4 4.9 0.8 13 4.6 2 43 

BOD11-11D 0.9 1.2 143 4.4 <0.2 0.5 5.9 5 1.6 8.8 12 

BOD11-12 <0.2 0.5 120 0.7 0.3 4.4 0.3 4 4.6 2.3 11 

BOD11-13 0.3 0.4 186 <0.1 2.2 4.2 1.9 23 2.5 4.1 37 

BOD11-14 0.3 0.3 132 0.2 <0.2 1.9 0.5 2 1.7 3.7 2 

BOD11-18A 8.9 0.4 78 <0.1 1.9 1.9 3.2 664 1.7 8.1 5 

BOD11-19 1.6 0.2 145 0.2 <0.2 2.8 0.7 3 0.2 5.8 4 

BOD13-1A <0.2 0.2 70.7 <0.1 0.2 2.2 <0.1 2 0.8 0.7 21 

BOD13-2B <0.2 0.2 28.3 <0.1 <0.2 1.2 <0.1 2 0.7 0.7 9 

BOD13-5B 1.5 1.1 131 <0.1 3.3 8.8 1.3 23 8.3 4.2 11 

BOD13-5C 5.3 0.8 150 <0.1 0.8 6 0.4 6 1.9 1 11 
Table 1-11. Minor element concentrations in rock samples from the Bodie Mining District.—Continued[cm, centimeter; K, potassium; Kspar, potassium feldspar; —, no data]

Sample 

number Description, Location Latitude Longitude Au ppm Hg ppm Al % Ca% Fe% K% 

Burgess series veins

11-BA-22A Bodie Mine dump, Standard Hill 38.21257 –119.00402 10.7 0.14 1.67 0.07 0.1 1

11-BA-22B Bodie Mine dump, Standard Hill 38.21257 –119.00402 4.62 0.08 1.64 0.03 0.05 111-BA-22C Bodie Mine dump, Standard Hill 38.21257 –119.00402 65 0.27 3.86 0.14 0.52 511-BA-22D Bodie Mine dump, Standard Hill 38.21257 –119.00402 1.69 0.09 1.62 0.08 0.54 111-BA-22E Bodie Mine dump, Standard Hill 38.21257 –119.00402 19.8 0.07 1.33 0.1 0.39 0

07-BA-2 Quartz vein bladed texture south of Bodie Bluff 38.21595 –119.00299 1.34 7.72 4.1 0.15 1.88 499-DJ-71A Banded quartz vein, Bulwer Mine dump, Standard Hill 38.21452 –119.00385 20 0.103 1.41 0.13 0.57 199-DJ-71B Pyritic quartz vein, Bulwer Mine dump, Standard Hill 38.21452 –119.00385 1 <0.096 4.84 0.36 1.54 699-DJ-71C Pyritic quartz vein, Bulwer Mine dump, Standard Hill 38.21452 –119.00385 1.55 <0.095 6.58 0.31 1.38 999-DJ-71D Silicified wall rock(?) with pyrite, Bulwer Mine dump 38.21452 –119.00385 0.11 <0.091 5.52 0.26 2.11 7

Silver Hill series veins

BODB07-8 Quartz-sulfide-K-mica breccia, Contention dump 38.20524 –119.0056 >10 1.43 2.12 0.21 0.66 0

09-BA-28A Red Cloud Mine dump 38.20151 –119.00363 3.85 1.6 2.16 0.34 0.39 009-BA-28B Red Cloud Mine dump 38.20151 –119.00363 37.9 0.72 1.08 0.1 1.99 009-BA-28C Red Cloud Mine dump 38.20151 –119.00363 23.3 2.05 1.38 0.31 0.3 009-BA-28H Red Cloud Mine dump 38.20151 –119.00363 0.61 0.14 2.73 0.11 0.88 109-BA-28I Red Cloud Mine dump 38.20151 –119.00363 2.05 0.1 3.14 0.15 3.72 307-BA-5A Silver Hill dump samples, Bodie 38.20517 –119.00479 6.81 2.76 1.54 0.11 0.92 007-BA-5B Silver Hill dump samples, Bodie 38.20517 –119.00479 13.3 0.77 1.43 0.22 0.48 099-DJ-70A sulfide-rich vein, Silver Hill 38.20517 –119.00479 0.03 0.759 1.07 0.71 1.87 099-DJ-70B 1-cm-wide quartz vein, Silver Hill 38.20517 –119.00479 0.027 0.967 1.22 0.65 1.76 099-DJ-72A Sulfide-rich quartz vein, Red Cloud Mine 38.20151 –119.00363 13 0.34 1.94 0.29 2.62 0

99-DJ-72B Sulfide-rich quartz vein, Red Cloud Mine 38.20151 –119.00363 0.403 0.213 3.27 0.22 1.25 1

11-BA-6E Red Cloud Mine dump 38.20130 –119.00460 42.8 0.12 2.31 0.04 0.17 1

11-BA-7A Oro Mine dump 38.20420 –119.00649 1.71 1.35 1.46 0.18 2.77 1

11-BA-7E Oro Mine dump 38.20420 –119.00649 0.052 0.22 4.03 0.16 0.68 4

11-BA-7F Oro Mine dump 38.20420 –119.00649 7.8 1.12 2.21 0.19 1.69 0

11-BA-9A Contention Mine dump 38.20547 –119.00472 2.04 0.4 1.08 0.23 0.51 0

11-BA-9B Contention Mine dump 38.20547 –119.00472 16.9 0.44 2.77 0.15 0.99 1
Table 1-11. Minor element concentrations in rock samples from the Bodie Mining District.—Continued [cm, centimeter; K, potassium; Kspar, potassium feldspar; —, no data] Sample number S% Ti % Ag ppm As ppm Ba ppm Be ppm Bi ppm Cd ppm Ce ppm Co ppm Cr ppm C

pp

Burgess series veins 11-BA-22A 0.04 <0.01 327 5 60 0.7 0.69 0.1 0.88 1.1 <1 

11-BA-22B 0.03 <0.01 212 <1 58 0.4 0.3 <0.1 0.54 0.6 <1 

11-BA-22C 0.41 0.05 243 129 424 0.6 0.29 0.3 11.8 1.9 2 

11-BA-22D 0.33 0.08 164 51 309 0.9 0.32 0.1 15.1 1.9 3 

11-BA-22E 0.24 0.04 171 7 52 0.8 1.46 3 8.22 0.9 2 

07-BA-2 1.86 0.1 13 335 736 0.6 0.12 <0.1 12.5 1.4 4 

99-DJ-71A — 0.05 41.6 12.6 154 1 <0.244 <0.097 — 2 — — 

99-DJ-71B — 0.39 20.8 45.1 164 1 0.743 <0.096 — 2 — — 

99-DJ-71C — 0.36 23.2 45.5 240 1 0.665 <0.095 — < 2 — — 

99-DJ-71D — 0.25 3.68 21.4 183 1 <0.229 <0.091 — 5 — — 

Silver Hill series veins BODB07-8 0.09 0.04 312 250 173 <5 72 29.6 15 1.8 <10 

09-BA-28A 0.48 0.01 430 573 464 0.4 9.57 1.2 4.94 0.7 2 

09-BA-28B 2.46 0.05 3,090 196 119 0.2 309 57.4 9.51 3.8 3 

09-BA-28C 0.9 0.02 837 534 195 0.3 106 36.3 11.8 1.5 2 

09-BA-28H 1.01 0.08 26 33 307 0.4 3.63 0.1 13.2 1.7 3 

09-BA-28I 4.8 0.24 115 84 75 0.5 21.1 1.9 14.2 11 8 

07-BA-5A 3.38 0.04 72 62 122 0.3 37.6 406 14.4 1.9 3 

07-BA-5B 0.86 0.01 56 185 153 0.5 38.6 16.9 8.46 1.6 2 

99-DJ-70A — 0.27 4.75 56.5 296 1 0.797 <0.097 — 6 — — 

99-DJ-70B — 0.31 5.21 47.2 244 1 1.07 <0.094 — 6 — — 

99-DJ-72A — 0.09 298 127 182 <1 29.4 9.76 — 4 — — 

99-DJ-72B — 0.13 18.1 27.5 252 1 2.96 0.261 — 3 — — 

11-BA-6E 0.13 0.02 352 68 120 0.5 1.48 0.7 4.23 0.4 1 

11-BA-7A >5 0.08 171 49 225 0.3 82.1 258 28.3 7 3 

11-BA-7E 0.78 0.1 9 23 818 0.7 0.58 0.6 18.5 2 3 

11-BA-7F 2.55 0.09 432 248 126 0.3 41.8 42.5 12.7 5.9 5 

11-BA-9A 0.85 0.03 249 124 114 0.3 28.7 7.5 14.7 1.2 2 

11-BA-9B 1.72 0.07 305 36 163 0.4 65.8 9.4 14.8 1.8 3 
Table 1-11. Minor element concentrations in rock samples from the Bodie Mining District.—Continued[cm, centimeter; K, potassium; Kspar, potassium feldspar; —, no data]

Sample 

number

In

ppm

La

ppm

Li

ppm

Mn

ppm

Mo

ppm

Nb

ppm

Ni

ppm

P

ppm

Pb

ppm

Rb

ppm

Sb

ppm

Burgess series veins

11-BA-22A <0.02 <0.5 85 179 0.48 <0.1 2.5 <50 30.3 113 12.9 

11-BA-22B <0.02 <0.5 83 107 0.26 <0.1 1.8 <50 10.3 97.7 8.21 

11-BA-22C 0.03 6.6 56 272 8.87 2.1 4.7 190 59.8 241 23.5 

11-BA-22D <0.02 8.3 84 67 13.7 2.8 2.1 180 36.1 85.1 26.3 

11-BA-22E 0.06 4.9 51 99 1.34 1.3 0.8 120 239 42.5 6.06 

07-BA-2 <0.02 8.6 38 20 7.23 2.4 3.1 260 27.8 254 56.8 

99-DJ-71A — 2 — 153 2.48 3 15 80 2.93 — 1.02 

99-DJ-71B — 19 — 75 56.3 14 8 350 30.5 — 2.83 

99-DJ-71C — 17 — 61 54.1 9 5 280 29.5 — 2.61 

99-DJ-71D — 19 — 147 2.62 6 17 790 12.5 — 2.4 

Sample 

number

In

ppm

La

ppm

Li

ppm

Mn

ppm

Mo

ppm

Nb

ppm

Ni

ppm

P

ppm

Pb

ppm

Rb

ppm

Sb

ppm

Silver Hill series veins

BODB07-8 1.6 8.3 50 — 14 1 7 — 2,630 43.9 >1,000 

09-BA-28A 0.35 2.6 38 84 8.89 0.4 1.6 730 1,520 41.3 126 

09-BA-28B 4.06 5.8 24 28 48.6 1.5 1.4 370 2,260 20.3 3,080 

09-BA-28C 3.08 6.1 32 39 14 0.4 <0.5 1,470 2,870 27 6,380 

09-BA-28H 0.1 7.8 40 35 6.12 2.5 2.7 500 549 56.5 37.3 

09-BA-28I 0.4 8.5 23 48 16.7 4.8 15.1 460 1,880 148 22.5 

07-BA-5A 10.7 6.6 43 55 8.15 1.1 2.3 450 <0.5 28.7 510 

07-BA-5B 0.7 4.4 34 56 6.85 0.3 1.7 960 2,170 32.3 3,910 

99-DJ-70A — 19 — 76 119 8 13 730 26.7 — 4.64 

99-DJ-70B — 25 — 68 162 9 16 1,360 31.9 — 6.91 

99-DJ-72A — 10 — 51 13.7 3 17 860 1,112 — 1,457 

99-DJ-72B — 9 — 77 7.76 5 8 250 145 — 33.2 

11-BA-6E 0.05 2.3 52 54 1.46 0.9 1 140 96.4 65.5 149 

11-BA-7A 13.2 15.1 23 57 37.3 3.3 7.7 530 19,000 53.6 394 

11-BA-7E 0.06 10.3 52 61 7.85 4.8 2.9 340 62.6 231 23.1 

11-BA-7F 3.31 6.7 52 37 78.5 2 5 570 1,280 45.1 4,830 

11-BA-9A 0.37 7.1 33 21 5.9 1.1 1.4 680 1,190 27 758 

11-BA-9B 0.78 8.3 34 35 13.7 2.5 2 380 778 58.2 880 
Table 1-11. Minor element concentrations in rock samples from the Bodie Mining District.—Continued [cm, centimeter; K, potassium; Kspar, potassium feldspar; —, no data] Sample number Sc ppm Sn ppm Sr ppm Te ppm Th ppm Tl ppm Uppm Vppm Wppm Yppm Zn ppm 

Burgess series veins 11-BA-22A <0.1 0.4 39.1 3 <0.2 1.4 <0.1 4 0.5 0.2 34 

11-BA-22B <0.1 0.2 36.2 1.3 <0.2 1.2 <0.1 3 0.3 0.1 20 

11-BA-22C 0.9 0.3 170 3 2.3 3.6 0.8 7 6.1 2 100 

11-BA-22D 1.2 0.5 68.4 0.3 3.2 1.5 1.1 19 4.7 2.4 11 

11-BA-22E 0.6 0.3 43.3 0.9 1.6 0.7 0.7 22 18.6 1.1 464 

07-BA-2 0.7 0.4 147 0.2 2.9 7.7 0.8 13 2.1 1.4 6 

99-DJ-71A <0.975 <2 79 <0.487 — <0.487 — 9 <4 <2 23 

99-DJ-71B 1.36 2 154 <0.48 — 0.554 — 50 17 5 6.82 

99-DJ-71C 2.05 <2 205 <0.477 — <0.477 — 48 13 4 7.99 

99-DJ-71D <0.914 <2 331 <0.457 — 0.667 — 44 <4 5 24.4 

Sample number Se ppm Sn ppm Sr ppm Te ppm Th ppm Tl ppm Uppm Vppm Wppm Yppm Zn ppm 

Silver Hill series veins BODB07-8 4.6 67 40.4 181 2 0.7 1 24 3 2.1 1,870 

09-BA-28A — 67.1 35.4 19.8 0.6 0.9 0.1 17 1.1 0.3 31 

09-BA-28B — 183 12.2 >500 1.6 0.4 0.4 14 2.4 0.7 3,530 

09-BA-28C — 205 26.9 234 1.1 1.2 0.3 18 1.2 0.5 2,600 

09-BA-28H — 15.2 33.8 8.4 3.3 0.9 1.2 22 6.1 1.3 9 

09-BA-28I — 0.7 78 8.5 2.3 3.1 1.2 38 22 3.2 210 

07-BA-5A 85.4 2.7 25 280 1.7 0.6 0.5 19 1.9 1.1 27,900 

07-BA-5B 7.9 36.5 28.9 86.9 0.8 0.5 0.2 18 1 1.1 1,380 

99-DJ-70A <0.969 <2 24 <0.484 — 0.569 — 26 21 4 10.8 

99-DJ-70B <0.94 <2 19 <0.47 — 0.615 — 33 30 4 9.79 

99-DJ-72A 13.5 54 64 110 — <0.492 — 25 <4 <2 618 

99-DJ-72B 1.64 12 34 4.94 — <0.491 — 48 9 2 14.8 

11-BA-6E — 3.7 5.5 34.1 1 0.7 0.3 13 1.7 0.5 49 

11-BA-7A — 17.9 48 135 7.2 1.5 0.7 12 2.5 2 20,700 

11-BA-7E — 0.8 157 2.4 4 3.2 1.2 17 6.1 2.5 41 

11-BA-7F — 47.8 52.7 191 3.2 1 1 21 4 1.5 1,470 

11-BA-9A — 10.5 18 41.7 1.7 0.4 0.5 9 1.2 2.7 479 

11-BA-9B — 70.7 18.6 230 2.7 0.9 0.8 29 4.5 1.5 674 
Table 1-11. Minor element concentrations in rock samples from the Bodie Mining District.—Continued[cm, centimeter; K, potassium; Kspar, potassium feldspar; —, no data]

Sample 

number Description, Location Latitude Longitude Au ppm Hg ppm Pd ppb Pt ppb Al % Ca% Fe% 

Silver Hill series veins

11-BA-10A Addenda Mine dump 38.20556 –119.00543 1,150 0.38 — — 2.65 0.25 1

11-BA-10B Addenda Mine dump 38.20556 –119.00543 579 0.91 — — 2.66 0.25 1

BOD11-1ME Quartz-sulfide, minor K-mica vein, Oro dump 38.20432 –119.00746 77 0.82 1 2.3 2.25 0.27 5

BOD11-2ME Banded quartz-Kspar, minor sulfide vein, Noonday dump 38.20023 –119.00991 >10 0.22 <1 <0.5 5.83 <0.01 0

BOD11-2AME Quartz-sulfide-K-mica breccia, Contention dump 38.20524 –119.0056 29 3.24 3 2.4 1.42 0.21 1

BOD11-5ABCME Quartz-sulfide breccia, Red Cloud dump 38.20133 –119.00588 >10 1.34 <1 <0.5 1.81 0.14 0

BOD11-22A Quartz vein with chalcopyrite, pyrite 38.21209 –119.00122 6.75 1.46 — — 1.13 0.02 0

BOD11-22B Quartz vein with chalcopyrite, pyrite 38.21209 –119.00122 1.23 1.24 — — 3.83 0.1 0

Sample 

number Description, Location Latitude Longitude Au ppm Hg ppm Al % Ca% Fe% K% M

% 

Uncorrelated veins

11-BA-21A Noonday Mine dump 38.20037 –119.00919 5.81 0.06 1.13 23.4 0.02 1.6 0

Table 1-11. Minor element concentrations in rock samples from the Bodie Mining District.—Continued[cm, centimeter; K, potassium; Kspar, potassium feldspar; —, no data]

Sample 

number

S

%

Ti

%

Ag

ppm

As

ppm

Ba

ppm

Be

ppm

Bi

ppm

Cd

ppm

Ce

ppm

Co

ppm

Cr

ppm

Cs

ppm

Silver Hill series veins

11-BA-10A 2.11 0.08 335 507 163 0.3 552 46.4 12.7 3.1 5 7 

11-BA-10B 2.58 0.07 250 858 163 0.3 478 70.5 11.1 2.6 4 6 

BOD11-1ME >5 0.09 1,080 206 160 0.3 61.5 181 21.8 5.9 4 <5 

BOD11-2ME 0.02 <0.01 180 11 92 1.1 0.33 0.2 1.81 1.1 <1 14 

BOD11-2AME 3.27 0.06 497 1,210 91 0.2 156 101 11.4 5.3 5 <5 

BOD11-5ABCME 0.59 0.04 1,030 416 311 0.3 34.5 15.8 11.8 0.8 3 7 

BOD11-22A 0.64 0.03 2,900 236 27 0.4 169 22.6 14.1 17.3 2 <5 

BOD11-22B 0.4 0.12 326 31 49 0.9 30.9 2.8 25.1 12.6 2 5 

Sample 

number

Ag

ppm

As

ppm

Ba

ppm

Be

ppm

Bi

ppm

Cd

ppm

Ce

ppm

Co

ppm

Cr

ppm

Cs

ppm

Cu

ppm

Ga

ppm

Uncorrelated veins

11-BA-21A 137 <1 22 20.2 1.36 0.2 0.35 0.4 <1 <5 68.2 1.04 
Table 1-11. Minor element concentrations in rock samples from the Bodie Mining District.—Continued [cm, centimeter; K, potassium; Kspar, potassium feldspar; —, no data] Sample number In ppm La ppm Li ppm Mn ppm Mo ppm Nb ppm Ni ppm Pppm Pb ppm Rb ppm Sb ppm 

Silver Hill series veins 11-BA-10A 4.05 7.3 36 20 38 2.6 <0.5 1,160 2,180 52.8 6,780 

11-BA-10B 5.14 6.8 28 24 44.1 1.8 <0.5 1,080 2,970 55.6 >10,000 BOD11-1ME 13.2 10.9 26 75 28.7 1.1 5.9 750 4,890 76.8 3,580 BOD11-2ME <0.02 1.1 71 83 0.63 1.3 <0.5 <50 17.6 273 39.5 

BOD11-2AME 5.01 6.7 33 38 28.8 1.1 <0.5 1,180 2,710 24.8 >10,000 

BOD11-5ABCME 1.51 6.3 51 37 16.5 1.2 0.8 600 1,600 52.1 983 BOD11-22A 1.49 8.2 43 25 7.62 0.8 9 150 329 38.5 962 BOD11-22B 0.35 15.4 49 42 3.84 4 9.9 310 225 94.7 191 

Sample number Li ppm Mn ppm Mo ppm Nb ppm Ni ppm Pppm Pb ppm Rb ppm Sb ppm Sc ppm Se ppm 

Uncorrelated veins 11-BA-21A 51 311 0.18 <0.1 <0.5 <50 12.7 89.9 26.4 <0.1 

Table 1-11. Minor element concentrations in rock samples from the Bodie Mining District.—Continued [cm, centimeter; K, potassium; Kspar, potassium feldspar; —, no data] Sample number Sn ppm Sr ppm Te ppm Th ppm Tl ppm Uppm Vppm Wppm Yppm Zn ppm Silver Hill series veins 11-BA-10A 192 52.1 >500 3.4 0.8 1.2 31 10.7 1.6 3,780 11-BA-10B 258 32.4 >500 2.9 0.8 0.9 36 7 1.9 6,870 BOD11-1ME 37.6 68 340 3.3 2.6 0.7 12 2.6 1.3 11,800 BOD11-2ME 1.1 139 4 <0.2 6.8 <0.1 <1 3.9 0.3 12 BOD11-2AME 68.4 39.1 340 2 0.7 0.7 18 3.8 1 5,760 BOD11-5ABCME 132 27.7 128 1.6 0.9 0.4 17 1.9 1 1,410 BOD11-22A 26.9 42.4 53.9 1.4 0.7 3 15 2.6 9 2,260 BOD11-22B 7.1 57 11.9 4.6 1.2 2 39 15.1 7.6 246

Sample 

number

Te

ppm

Th

ppm

Tl

ppm

U

ppm

V

ppm

W

ppm

Y

ppm

Zn

ppm

C

%

Uncorrelated veins

11-BA-21A 2.5 <0.2 1.1 <0.1 <1 2.1 0.2 16 —
Table 1-12. Minor element concentrations in rock samples of Spring Peak sinter and subjacent rocks.

Sample 

number Description Latitude Longitude Au ppm Hg ppm Pd ppb Pt ppb A% Ca% Fe% 

06-BA-2 Banded quartz vein beneath sinter 38.24908 –118.85782 0.026 0.19 — — 0.66 0.09 0.0

SPK06-1 Sinter, north edge of terrace 38.24928 –118.85268 0.042 0.84 — — 0.33 0.03 0.0

SPK06-2 Sinter, prospect pit 38.24868 –118.85293 0.0066 0.1 — — 0.18 0.04 0.0

SPK06-3 Sinter, north edge of terrace 38.24932 –118.85239 0.053 1.02 — — 0.2 0.03 0.0

SPK11-10 Silicified, pyritic clastic sediments, sub-sinter 38.24770 –118.85113 0.007 3.63 — — 5.38 0.37 1.8 

SPK11-1ME Silicified pyritic tuff beneath sinter 38.24853 –118.84904 0.004 1.28 3 <0.5 5.16 0.44 0.9

SPK11-4ME White-beige, granitic rock altered to quartz, clay 38.24960 –118.86053 0.003 6.05 <1 <0.5 6.3 0.09 0.9

SPK11-2ME Banded vein beneath sinter, in granitic rock 38.24876 –118.85513 0.126 26.5 <1 <0.5 0.66 0.14 0.

Table 1-12. Minor element concentrations in rock samples of Spring Peak sinter and subjacent rocks.—Continued

Sample 

number

Na

%

S

%

Ti

%

Ag

ppm

As

ppm

Ba

ppm

Be

ppm

Bi

ppm

Cd

ppm

Ce

ppm

Co

ppm

Cr

ppm

Cs

ppm

p

06-BA-2 0.02 <0.01 <0.01 2 28 52 1.9 <0.04 <0.1 1.16 0.3 5 24 

SPK06-1 <0.01 0.01 <0.01 1 <30 85 11 0.5 <0.2 1.7 0.8 <10 61.1 4

SPK06-2 <0.01 <0.01 <0.01 <1 <30 90 <5 <0.1 <0.2 0.4 <0.5 <10 12.2 

SPK06-3 <0.01 <0.01 <0.01 <1 — — — — — — — — — 

SPK11-10 0.54 1.45 0.22 <1 1,560 731 4.3 0.14 <0.1 29.3 9.7 4 44 11

SPK11-1ME 0.95 0.12 0.19 <1 252 815 2 0.62 <0.1 26.2 1.2 3 71 1

SPK11-4ME 0.08 0.26 0.15 <1 293 1,440 0.4 0.07 <0.1 46.6 0.3 2 115 1

SPK11-2ME 0.03 0.03 <0.01 <1 62 178 1.2 <0.04 <0.1 4.13 0.1 2 110 
Table 1-12. Minor element concentrations in rock samples of Spring Peak sinter and subjacent rocks.—Continued Sample number La ppm Li ppm Mn ppm Mo ppm Nb ppm Ni ppm Pppm Pb ppm Rb ppm Sb ppm 

06-BA-2 0.6 123 138 36.3 <0.1 1.1 70 1.5 22.1 272 

SPK06-1 0.9 20 — <2 <1 <5 — <5 13.2 664 

SPK06-2 0.3 20 — <2 <1 8 — <5 5.4 835 

SPK06-3 1 30 — <2 <1 6 — <5 7.6 >1,000 

SPK11-10 15.3 75 90 2.04 4.3 3.1 810 10.6 236 208 

SPK11-1ME 12.8 93 49 2.23 5.4 0.9 490 12.3 219 259 

SPK11-4ME 24.6 6 27 7.64 6.7 <0.5 320 11.9 75.7 242 

SPK11-2ME 2.5 36 21 2.79 0.4 <0.5 420 1.4 28.5 566 

Table 1-12. Minor element concentrations in rock samples of Spring Peak sinter and subjacent rocks.—Continued Sample number Sn ppm Sr ppm Te ppm Th ppm Tl ppm Uppm Vppm Wppm Yppm Zn ppm C% 06-BA-2 <0.1 97.9 <0.1 0.2 0.4 0.2 <1 0.5 1.4 <1 — SPK06-1 <1 39.9 <0.5 0.4 1.1 0.23 6 3 <0.5 8 0.01 SPK06-2 <1 21.3 <0.5 <0.1 <0.5 0.1 <5 1 <0.5 — 0.02 SPK06-3 <1 22.5 <0.5 <0.1 <0.5 0.22 <5 5 0.5 <5 0.05 SPK11-10 1.5 166 <0.1 5.6 14 2.3 124 42.4 11.5 27 — SPK11-1ME 0.9 271 <0.1 6.4 3.9 2.2 82 73.2 6.6 9 — SPK11-4ME 0.9 531 <0.1 13.2 2.7 6.2 28 37 3 6 — SPK11-2ME 0.2 122 <0.1 1.3 3.1 0.7 4 2.2 2.6 3 —
Menlo Park Publishing Service Center, California 

Manuscript approved for publication January 23, 2015

Edited by Sarah Nagorsen

Layout and design by Kay Naugle
Vikre and others—Gold-Silver Mining Districts, Alteration Zones, and Paleolandforms in the Miocene Bodie Hills Volcanic Field—Scientific Investigations Report 2015–5012

ISSN 2328-0328 (online)

http://dx.doi.org/10.3133/sir20155012