Mineral Resources of the High Rock Lake 

Wilderness Study Area, 

Humboldt County, Nevada

U.S. GEOLOGICAL SURVEY BULLETIN 1707-A

Chapter A

Mineral Resources of the

High Rock Lake Wilderness Study Area,

Humboldt County, Nevada

By DONALD C. NOBLE, DONALD PLOUFF, and JOEL R. BERGQUIST 

U.S. Geological Survey

TERRY R. NEUMANN and TERRY J. CLOSE 

U.S. Bureau of Mines

U.S GEOLOGICAL SURVEY BULLETIN 1707

MINERAL RESOURCES OF WILDERNESS STUDY AREAS: NORTHWESTERN NEVADA
DEPARTMENT OF THE INTERIOR 

DONALD PAUL MODEL, Secretary

U.S. GEOLOGICAL SURVEY 

Dallas L. Peck, Director

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1987

For sale by the

Books and Open-File Reports Section

U.S. Geological Survey

Federal Center, Box 25425

Denver, CO 80225

Library of Congress Cataloging-in-Publication Data

Mineral resources of the High Rock Lake Wilderness 

Study Area, Humboldt County, Nevada.

U.S. Geological Survey Bulletin 1707-A

Bibliography

Supt. of Docs. No.: 119.3:1707-A

1. Mines and mineral resources Nevada High Rock

Lake Wilderness. 2. High Rock Lake Wilderness (Nev.)

I. Noble, Donald C. II. Series: U.S. Geological Survey

Bulletin 1707-A

QE75.B9 No. 1707-A 557.3s 87-600157

[TN24.N3] [557.93*54]
STUDIES RELATED TO WILDERNESS

Bureau of Land Management Wilderness Study Area

The Federal Land Policy and Management Act (Public Law 94-579, October 21, 

1976) requires the U.S. Geological Survey and the U.S. Bureau of Mines to conduct 

mineral surveys on certain areas to determine the mineral values, if any, that may be 

present. Results must be made available to the public and be submitted to the President 

and the Congress. This report presents the results of a mineral survey of part of the 

High Rock Lake Wilderness Study Area (NV-020-007), Humboldt County, Nevada.

CONTENTS

Summary Al

Abstract 1

Character and setting 1

Identified resources and mineral resource potential 1 

Introduction 1

Area description 1

Previous investigations 1

Present investigations 3 

Appraisal of identified resources 3 

Assessment of mineral resource potential 3

Geology 3

Geochemical studies 5

Geophysical studies 5 

Conclusions 6 

References cited 6 

Appendix

Definition of levels of mineral resource potential and certainty of assessment 8

Geologic time chart 9

FIGURES

1. Index map showing location of the High Rock Lake Wilderness Study Area, Humboldt 

County Nevada A2

2. Map showing mineral resource potential and generalized geology of the High Rock 

Lake Wilderness Study Area, Humboldt County, Nevada 4

MINERAL RESOURCES OF WILDERNESS STUDY AREAS: NORTHWESTERN NEVADA

Mineral Resources of the

High Rock Lake Wilderness Study Area,

Humboldt County, Nevada

By Donald C. Noble, Donald Plouff, and Joel R. Bergquist 

U.S. Geological Survey

Terry R. Neumann anc/Terry J. Close 

U.S. Bureau of Mines

SUMMARY

Abstract

The part of the High Rock Lake Wilderness Study 

Area (NV-020-007) requested for mineral surveys 

encompasses 14,000 acres in the northern part of the 

Calico Mountains. Field work for this report was 

carried out in 1984 and 1985. The study area is 

underlain predominantly by slightly tilted volcanic 

rocks (rhyolitic ash-flow tuffs). No resources were 

identified within the study area. A low potential 

exists throughout the study area for undiscovered 

volcanic-hosted resources of mercury, uranium, and 

disseminated gold. The northern part of the study area 

has low potential for undiscovered geothermal energy 

resources. In this report, references to the study area 

refer only to that part of the High Rock Lake 

Wilderness Study Area requested by the U.S. Bureau of 

Land Management for mineral surveys.

Character and Setting

The High Rock Lake Wilderness Study Area is 

located in the northern part of the Calico Mountains 

about 45 mi north of Gerlach, Nev. (fig. 1). A major 

active normal fault system bounds the west margin of 

the range. The study area is underlain by slightly 

tilted Miocene (see appendix for geologic time scale) 

rhyolitic volcanic rocks. Rocks in the northwestern 

part of the study area locally exhibit weak 

hydrothermal alteration.

Identified Resources and Mineral Resource Potential

There are no identified mineral resources in the 

High Rock Lake Wilderness Study Area. The study

area has a low potential for undiscovered volcanichosted resources of mercury, uranium, and 

disseminated gold (fig. 2). There is low potential for 

undiscovered geothermal resources in the northern 

part of the study area.

INTRODUCTION

Area Description

The High Rock Lake Wilderness Study Area (NV020-007) covers 14,000 acres in the northern part of 

the Calico Mountains in western Humboldt County, 

Nev., about 45 mi north of Gerlach, Nev. (fig. 1). The 

study area includes parts of the Mud Meadow, High 

Rock Lake, and Wagner Springs 7.5-minute 

quadrangles. The terrain is relatively gentle in much 

of the study area, although steep cliffs are present in 

Box Canyon, Fly Canyon, and along the east side of 

High Rock Lake. The climate is arid to semiarid, and 

vegetation is sparse with greasewood, sagebrush, and 

cheatgrass the dominant species.

The best access to the study area is from 

Gerlach via the Soldier Meadow County Road (HU 217) 

(fig. 1). The study area can also be reached from the 

southwest by an unimproved dirt road through Smokey 

Canyon.

Previous Investigations

Willden (1964) published a geologic map of 

Humboldt County that differentiates Cenozoic and 

pre-Cenozoic rocks, but provides little detail of the 

Cenozoic stratigraphy. Unpublished reconnaissance 

geologic mapping of the Cenozoic rocks of the western 

part of Humboldt County by B.C. Noble, incorporated 

into the Geologic map of Nevada (Stewart and Carlson,

Al
119°00'

41°00'

HIGH ROCK LAKE 

WILDERNESS 

STUDY AREA 

(NV-020-007)

Figure 1. Index map showing location of High Rock Lake Wilderness Study Area, Humboldt County, Nevada. 

Known geothermal resource area (KGRA) boundaries from Muffler (1979).

A2
1978), was the foundation for the geologic mapping 

completed in 1985 for this study.

Present Investigations

This mineral resource study is the result of a 

cooperative effort by the U.S. Geological Survey 

(USGS) and the U.S. Bureau of Mines (USBM) to 

evaluate the mineral resources and mineral resource 

potential of the High Rock Lake Wilderness Study 

Area. Mineral assessment methodology and terminology are discussed by Goudarzi (1984). Studies by the 

USGS are designed to provide a reasonable scientific 

basis for assessing the potential for undiscovered 

mineral resources by determining geologic units and 

structures, possible environments of mineral 

deposition, and the presence of geochemical and 

geophysical anomalies. The USBM evaluates identified 

resources at individual mines and known mineralized 

areas by collecting data on current and past mining 

activities and through field examination of mines, 

prospects, and mineralized areas.

U.S. Bureau of Mines personnel conducted a 

mineral survey of the High Rock Lake Wilderness 

Study Area. All available data on geology, mining, and 

mineral resources of this area, including federal and 

county mining claim records, were reviewed prior to 

field work. Mapping and sampling of mines, prospects, 

and mineralized zones were carried out in the summer 

of 1984.

The geochemical evaluation of the study area 

was based on data from the evaluation of study areas 

in the Winnemucca district by Barringer Resources, 

Inc. (1982), and on fire-assay and optical emissionspectrographic analyses of samples by the U.S. Bureau 

of Mines (Neumann and Close, 1985).

APPRAISAL OF IDENTIFIED RESOURCES

By_ Terry R. Neumann and Terry J. Close 

U.S. Bureau of Mines

No identified mineral resources were delineated 

in the High Rock Lake Wilderness Study Area, and no 

mineral properties or mineralized zones are located 

within the study area. A belt of opalized rocks that 

extends about 2 mi south-southeast from the mouth of 

Willow Canyon (fig. 1) outside the study area has been 

prospected for gemstone opal. The opal occurs within 

vesicles in basalt, and must be extracted by hand. 

Almost all the opal is common variety, but milk opal, 

hyalite, moss opal, and precious fire opal are present 

locally. The opal dehydrates within several weeks of 

extraction, and thus is not gem quality. Moreover, 

basalt flows that host the opal are present in only a 

very small area in the southeastern part of the study 

area (fig. 2).

Finely bedded tuffaceous volcaniclastic 

sedimentary rocks exposed 8 mi south of the study 

area near Donnelly Creek (fig. 1) contain about 50 

percent clinoptilolite, a zeolite mineral (Neumann and 

Close, 1985). However, the rock unit that contains the 

zeolite is not exposed in the study area.

Although geochemical sampling of stream 

sediments conducted by Barringer Resources, Inc. 

(1982), disclosed localized low-level anomalies of 

mercury, fire-assay and optical-emission 

spectrographic analyses of rock-chip samples from the 

study area failed to reveal anomalous concentrations 

of metals.

The Soldier Meadow Known Geothermal 

Resource Area (KGRA) adjoins and includes a small 

section of the northern part of the study area (fig. 1). 

No hot springs are present in the study area, although 

several hot springs are found in Soldier Meadow, 1 mi 

north of the study area. Surface temperatures of 

these springs are about 129 °F, and subsurface 

temperatures are about 239 °F (White and Williams, 

1975; Brook and others, 1979).

ASSESSMENT OF MINERAL RESOURCE POTENTIAL

By Donald C. Noble, Donald Plouff, and 

Joel R. Bergquist, U.S. Geological Survey

Geology

The High Rock Lake Wilderness Study Area is 

underlain by volcanic rocks mostly of middle Miocene 

age and alluvium, colluvium, and other surficial 

deposits of Quaternary age. The principal rocks 

exposed are densely welded comenditic (peralkaline 

rhyolite) ash-flow tuffs of the Soldier Meadow Tuff 

(Noble and others, 1970), which cap an eastward-tilted 

mesa that comprises most of the study area. These 

tuffs were erupted from vents located several miles 

north of Soldier Meadow (Korringa, 1973; Greene and 

Plouff, 1981; Park and others, 1983) and perhaps 

directly north and (or) northwest of the study area. 

Near the mouth of Box Canyon, the Soldier Meadow 

Tuff overlies basalt and rhyolitic ash-flow and air-fall 

tuffs of the tuff of Trough Mountain and the Summit 

Lake Tuff (Noble and others, 1970; Korringa, 1973) 

(fig. 2). East of High Rock Lake and in the upper part 

of Box Canyon, the Soldier Meadow Tuff overlies 

peralkaline rhyolite (comendite) flows that probably 

are younger than the Summit Lake Tuff. Bedded and 

reworked tuffs, largely of rhyolitic composition, 

contain vertebrate fossils and overlie the Soldier 

Meadow Tuff north of High Rock Lake and in Fly 

Canyon. With the exception of the basalts, which 

could be late Oligocene to middle Miocene in age, all 

the volcanic rocks within the study area are middle 

Miocene (15 to 16 million years before present (Ma)) 

(Noble and others, 1970, 1987; Hart and Carlson, 

1985).

A major north-trending normal fault with an 

offset of greater than 1,000 ft is located a few 

hundred yards east of High Rock Lake. Related faults 

to the east offset the Soldier Meadow Tuff. A system 

of normal faults, down dropped on the east side, bound 

the Calico Mountains on the east. A few landslides are 

present in the upper and middle parts of Box Canyon.

Lacustrine deposits related to late Quaternary 

Lake Lahontan are exposed in the eastern part of the 

study area, and lacustrine deposits related to High 

Rock Lake are exposed on the west side of the area.

A3
L/B GEOTHERMAL[1]

APPROXIMATE BOUNDARY OF

HIGH ROCK LAKE 

WILDERNESS STUDY AREA 

(NV-020-007)

L/B Au,Hg,U 

[2]

Figure 2. Mineral resource potential and generalized geology of the High Rock Lake Wilderness Study Area, 

Humboldt County, Nevada. Geologic mapping by D.C. Noble (unpub. data, 1985).

A4
EXPLANATION

Area with low mineral resource potential See 

appendix for definition of levels of mineral resource 

potential and certainty of assessment

Commodities

Au Gold 

Hg Mercury 

U Uranium

Geothermal

Types of deposits

1 Geothermal energy

2 Volcanic-hosted hydrothermal deposits

Geologic map units

Qac Alluvium and colluvium (Quaternary)

Ql Landslide deposits (Quaternary)

Qls Lake sediments (Quaternary)

Tbt Bedded tuff (Middle Miocene)

Ts Soldier Meadow Tuff (Middle Miocene)

Tr Rhyolite (Middle Miocene)

Tst Summit Lake Tuff and tuff of Trough Mountain (Middle

	Miocene) 

Tb Basalt (Middle Miocene to Upper Oligocene)

 - Contact Dashed where approximately located;dotted where 

concealed

_1_ .. Fault Dashed where approximately located or inferred; 

dotted where concealed; bar and ball on downthrown side

 * Hot spring

Figure 2. Continued.

No evidence of hydrothermal alteration was 

observed within the study area except for local 

opalization of the Soldier Meadow Tuff adjacent to a 

normal fault about 0.5 mi north-northeast of High 

Rock Lake.

Geochemical Studies

A geochemical-geostatistical study of the High 

Rock Lake Wilderness Study Area was contracted with 

Barringer Resources, Inc., of Golden, Colo. by the U.S. 

Bureau of Land Management. Twenty-three streamsediment samples were collected within the study area 

and analyzed for 33 major and minor elements using 

induction coupled argon plasma emission (ICP), 

fluorimetric analysis, colorimetric methods, and 

atomic absorption spectroscopy (Barringer Resources, 

Inc., 1982).

Stream sediments derived largely from the 

Soldier Meadow Tuff contain relatively high 

concentrations of fluorine (averaging about 700 ppm)

and mercury (averaging about 15 ppb) (Barringer 

Resources, Inc., 1982). However, these values 

probably reflect the high background concentrations of 

fluorine and mercury that are characteristic of the 

Soldier Meadow Tuff (Korringa, 1973; Stuart and 

others, 1983). Concentrations in the samples of 

uranium, gold, silver, and other elements diagnostic of 

precious- or base-metal mineralization are within 

background values.

U.S. Bureau of Mines personnel collected 28 

rock-chip samples from unclaimed areas in and near 

the study area (Neumann and Close, 1985). Most of 

the samples were taken along faults in Cenozoic 

volcanic rocks. The samples were analyzed for gold 

and silver by fire-assay methods and for 29 other 

elements by semiquantitative optical emission 

spectrography. None of the samples contain 

anomalous concentrations of ore-related or pathfinder 

elements.

Geophysical Studies

J.S. Duval (written commun., 1985) determined 

concentrations of potassium, equivalent uranium, and 

equivalent thorium by examining unpublished 

composite-color maps of gamma-ray spectrometric 

data. The maps were prepared at a scale of 

1:1,000,000 from radiometric data acquired in regional 

surveys contracted by the U.S. Department of Energy 

as part of the National Uranium Resource Evaluation 

(NURE) Program. East-west flightlines were flown at 

altitudes of about 400 ft above mean terrain with a 

three-mile spacing (Geodata International, Inc., 

1979). The study area has moderate radioactivity with 

values of 1.5 to 2.5 weight percent potassium, 2.5 to 

4.0 ppm equivalent uranium, and 6 to 12 ppm 

equivalent thorium based on criteria discussed by 

Duval (1983). There are no identified radioelement 

anomalies in or near the study area.

An aeromagnetic survey of the region was flown 

to provide detailed magnetic data for evaluation of the 

resource potential of the study area (U.S. Geological 

Survey, 1985). North-south flightlines at intervals of 

0.5 mi were flown at altitudes of about 1,000 ft above 

the mean terrain. The aeromagnetic map has rather 

uniformly spaced, east-trending, magnetic-intensity 

contours over most of the study area. The volcanic 

rocks near the surface throughout the study area 

apparently have low magnetization because the 

pattern of the magnetic contours is not correlated 

with prominent topographic scarps that occur within 

and along the boundary of the study area. The 

magnetic patterns may reflect the fact that 

peralkaline rhyelites commonly have low magnetic 

susceptibilities and low intensities of thermoremanent 

magnetization. The most prominent feature of the 

aeromagnetic map is a 1-mi-wide belt of east-trending 

magnetic contours near the center of the study area 

that curves northward before reaching High Rock 

Lake. The change of magnetic amplitude across the 

belt is a fairly constant 100 to 120 nanoteslas (nT). 

The belt may reflect the south and west edges of a

A5
large magnetic body concealed less than 1 mi beneath 

the surface, or it may reflect a step along the edge of 

a body concealed at a greater depth. The gradient 

along this belt forms part of a 600-nT magnetic high 

that is 7 by 14 mi and centered in the Black Rock 

Range about 4 mi east of Mud Meadow Lake (fig. 1) 

(Nevada Bureau of Mines and Geology, 1974). The 

broad magnetic high centered in the Black Rock Range 

and extending into the study area may indicate an 

underlying pluton with moderate to high 

magnetization.

Donald Plouff and C.F. Erdman established two 

gravity stations in the study area and three stations 

along the northwest edge of the study area to 

supplement gravity data from the National 

Geophysical Data Center (1984). The preliminary 

Bouguer gravity anomaly map by Plouff (unpub. data) 

shows a 5- by 8-mi gravity high with an amplitude of 8 

to 15 milligals (mGal), centered about 4 mi east of 

Mud Meadow Lake. This gravity high nearly coincides 

with the central part of the broad magnetic high.

A. small north-south-elongated, 3- by 5-mi 

gravity high is centered south of Mud Meadow Lake 

and overlies the east boundary of the study area. This 

local high may be part of the broad gravity high 

centered east of the study area (U.S. Geological 

Survey, 1972), because the two are separated by a 

narrow gravity low of less than 2 mGal. The gradient 

along the west edge of the local gravity high curves 

northeast to merge with the west edge of the broad 

gravity high near the northern part of Mud Meadow 

Lake.

North- to northwest-elongated gravity and 

magnetic lows reflect thickened sediments beneath 

and to the south of High Rock Lake. A gravity low 

centered on Fly Creek with an amplitude of 4 to 7 

mGal and a width of about 4 mi probably indicates a 

thick sequence of sediments centered between Fly 

Creek and the hot springs outside the northwest corner 

of the study area (fig. 2). For example, assuming that 

the sediments are 0.4 g/cm less dense than 

surrounding volcanic rocks and that the sedimentary 

basin has the shape of a 4-mi-diameter vertical 

cylinder, the sediments must be about 1,250 ft thick to 

produce a gravity low with an amplitude of 6 mGal. 

The maximum thickness of the sediments would be 

greater if the depression had a more realistic bowl 

shape.

CONCLUSIONS

The evaluation of mineral resource potential is 

based on a variety of data that include geologic, 

geochemical, and geophysical features, a survey of 

mines and prospects, and the mineral resources present 

in the surrounding regions.

Economically viable volcanic-hosted gold 

deposits of late Cenozoic age are present in 

northwestern Nevada, for example, the Hog Ranch 

mine, located about 15 mi southwest of the study area 

(fig. 1) in the northern part of the Leadville district. 

Scattered gold and (or) silver anomalies have been 

recognized in similar volcanic rocks of essentially the 

same age as the Soldier Meadow and Summit Lake 

Tuffs (D.C. Noble and E.H. McKee, unpub. data,

1985). Although no anomalous concentrations of gold 

or silver were recognized within the study area, on the 

basis of geologic setting, the study area has low 

potential, certainty level B, for disseminated gold in 

hydrothermal deposits.

Mercury deposits are known in northwestern 

Nevada (Williams and Compton, 1953; WiUden, 1964; 

Bonham, 1969). The slightly elevated concentrations 

of mercury within the study area probably are related 

to a high background level typical of the Soldier 

Meadow Tuff and not to mineral deposits. The study 

area has low potential, certainty level B, for mercury 

in hydrothermal deposits.

The Soldier Meadow Tuff contains higher 

concentrations of uranium than do most rhyolites 

(Korringa, 1973; Stuart and others, 1983), and 

peralkaline rhyolites are known to be associated with 

potentially economic uranium mineralization 

elsewhere in northwestern Nevada (Wallace and others, 

1980; Wallace and Roper, 1981). However, the aerial 

gamma-ray spectrometric survey, discussed above, 

disclosed no anomalous equivalent uranium 

concentrations, and geological surveys revealed no 

surface manifestations of uranium resources. The 

study area has a low potential, certainty level B, for 

uranium in volcanic-hosted deposits.

Opal is locally mined from basalt for gem stones 

in the Calico Mountains south of the study area 

(Neumann and Close, 1985). Similar basalt is exposed 

only in a very small area in the southeastern part of 

the study area. Because of the rapid dehydration of 

opal found in the basalt, the study area is not 

considered to have potential for undiscovered 

resources of gemstone opal. The opal may, however, 

be of interest to hobbyists.

The Soldier Meadow Known Geothermal 

Resource Area (KGRA) includes the northern part of 

the study area (fig. 1). The subsurface reservoir 

temperature of this area has been estimated to be 

about 239 °F (White and Williams, 1975; Brook and 

others, 1979). No deep drilling has been done. 

Geothermal waters of such temperature have potential 

for industrial processing applications. The 

northeastern part of the High Rock Lake Wilderness 

Study Area has low potential, certainty level B, for 

geothermal energy.

REFERENCES CITED

Barringer Resources, Inc., 1982, Geochemical and 

geostatistical evaluation wilderness study areas, 

Winnemucca District, northwest Nevada, prepared 

for United States Bureau of Land Management: 

Golden, Colo., 5 v., 24 pi., scale 1:250,000.

Bonham, H.F., 1969, Geology and mineral deposits of 

Washoe and Storey Counties, Nevada, with a 

section on Industrial minerals by K.G. Papke: 

Nevada Bureau of Mines and Geology Bulletin 70, 

140 p.

Brook, C.A., Mariner, R.H., Mabey, D.R., Swanson, 

J.R., Guffanti, Marianne, and Muffler, L.J.P., 

1979, Hydrothermal convection systems with 

reservoir temperatures >90° C., in Muffler, 

L.J.P., ed., Assessment of Geothermal Resources 

of the United States 1978: U.S. Geological

A6
Survey Circular 790, p. 18-85.

Duval, J.S., 1983, Composite color images of aerial 

gamma-ray spectrometric data: Geophysics, v. 

48, no. 6, p. 722-735.

Geodata International, Inc., 1979, Aerial radiometric 

and magnetic survey, Vya national topographic 

map, Nevada: U.S. Department of Energy OpenFile Report GJBX-136 (79), v. 2.

Goudarzi, G.H., 1984, Guide to preparation of mineral 

reports on public lands: U.S. Geological Survey 

Open-File Report 84-787, 42 p.

Greene, R.C., and Plouff, Donald, 1981, Location of a 

caldera source for the Soldier Meadow Tuff, 

northwestern Nevada, indicated by gravity and 

aeromagnetic data: Geological Society of 

America Bulletin, v. 92, no. 1, p. 39-56.

Hart, W.K., and Carlson, R.W., 1985, Distribution and 

geochronology of Steens Mountain-type basalts 

from the northwestern Great Basin: 

Isochron/West, no. 43, p. 5-10.

Korringa, M.K., 1973, Linear vent area of the Soldier 

Meadow Tuff, an ash-flow sheet in northwestern 

Nevada: Geological Society of America Bulletin, 

v. 84, p. 3849-3866.

Muffler, L.J.P., ed., 1979, Assessment of geothermal 

resources of the United States 1978: U.S. 

Geological Survey Circular 790, map 1, scale 

1:2,500,000.

National Geophysical Data Center, 1984, DMA gravity 

file of the United States: Boulder, Colo., National 

Oceanic and Atmospheric Administration, 

2 magnetic tapes.

Neumann, T.R., and Close, T.J., 1985, Mineral 

resources of the High Rock Lake Wilderness Study 

Area (BLM No. NV-020-007), Humboldt County, 

Nevada: U.S. Bureau of Mines Open-File Report 

MLA 38-85, 14 p.

Nevada Bureau of Mines and Geology, 1974, 

Aeromagnetic map of Nevada Vya sheet: Nevada 

Bureau of Mines and Geology Map 48, 1 pi., scale 

1:250,000.

Noble, D.C., McKee, E.H., Smith, J.G., and Korringa, 

M.K., 1970, Stratigraphy and geochronology of 

Miocene rocks in northwestern Nevada: U.S. 

Geological Survey Professional Paper 700-D, p. 

D23-D32.

Noble, D.C., Plouff, Donald, Bergquist, J.R., and 

Barton, H.N., 1987, Mineral resources of the 

Pahute Peak Wilderness Study Area, Humboldt

County, Nevada: U.S. Geological Survey Bulletin 

1726-C in press .

Park, S.L., Erwin, J.W., Noble, D.C., and McKee, E.H., 

1983, Paleomagnetic stratigraphy, geochemistry, 

and source areas of Miocene ash-flow tuffs and 

lavas of the Badger Mountain area, northwestern 

Nevada [abs.]: Geological Society of America 

Abstracts with Programs, v. 15, p. 281.

Stewart, J.H., and Carlson, J.E., 1978, Geologic map 

of Nevada: U.S. Geological Survey in cooperation 

with the Nevada Bureau of Mines and Geology, 

scale 1:500,000.

Stuart, E.J., Bornhorst, T.J., Rose, W.L, Jr., and 

Noble, D.C., 1983, Distribution and mobility of 

uranium and thorium in the Soldier Meadow Tuff, 

northwestern Nevada: Economic Geology, v. 78, 

p. 353-358.

U.S. Geological Survey, 1972, Aeromagnetic map of 

the Vya and part of the McDermitt 1° by 2° 

quadrangles, Nevada: U.S. Geological Survey 

Open-File Report, scale 1:250,000.

U.S. Geological Survey, 1985, Aeromagnetic map of 

the High Rock Lake area, northwestern Nevada: 

U.S. Geological Survey Open-File Report 85-751, 

scale 1:62,500.

Wallace, A.B., Drexler, J.W., Grant, N.K., and Noble, 

D.C., 1980, Icelandite and aenigmatite-bearing 

pantellerite from the McDermitt Caldera 

complex, Nevada-Or eg on: Geology, v. 8, p. 380- 

384.

Wallace, A.B., and Roper, M.W., 1981, Geology and 

uranium deposits along the northeastern margin, 

McDermitt Caldera complex, Oregon: in Goodell, 

P.C., and Waters, A.C., eds., Uranium in volcanic 

and volcaniclastic rocks: American Association of 

Petroleum Geologists, Studies in Geology No. 13, 

p. 73-79.

White, D.E., and Williams, D.L., eds., 1975, 

Assessment of geothermal resources of the United 

States: U.S. Geological Survey Circular 726, 

155 p.

Willden, Ronald, 1964, Geology and mineral deposits of 

Humboldt County, Nevada: Nevada Bureau of 

Mines Bulletin 59, 154 p.

Williams, Howel, and Compton, R.R., 1953, Quicksilver 

deposits of Steens Mountain and Pueblo 

Mountains, southeast Oregon: U.S. Geological 

Survey Bulletin 995-B, p. 19-77.

A7
APPENDIX. Definition of levels of mineral resource potential and 

certainty of assessment

Definitions of Mineral Resource Potential

LOW mineral resource potential is assigned to areas where geologic, geochemical, and geophysical characteristics define a geologic environment in which the existence of resources is unlikely. This broad 

category embraces areas with dispersed but insignificantly mineralized rock as well as areas with few 

or no indications of having been mineralized.

MODERATE mineral resource potential is assigned to areas where geologic, geochemical, and geophysical 

characteristics indicate a geologic environment favorable for resource occurrence, where interpretations 

of data indicate a reasonable likelihood of resource accumulation, and (or) where an application of 

mineral-deposit models indicates favorable ground for the specified type(s) of deposits.

HIGH mineral resource potential is assigned to areas where geologic, geochemical, and geophysical characteristics indicate a geologic environment favorable for resource occurrence, where interpretations of 

data indicate a high degree of likelihood for resource accumulation, where data support mineral-deposit 

models indicating presence of resources, and where evidence indicates that mineral concentration has 

taken place. Assignment of high resource potential to an area requires some positive knowledge that 

mineral-forming processes have been active in at least part of the area.

UNKNOWN mineral resource potential is assigned to areas where information is inadequate to assign low, 

moderate, or high levels of resource potential.

NO mineral resource potential is a category reserved for a specific type of resource in a well-defined 

area.

Levels of Certainty

U/A

UNKNOWN

POTENTIAL

H/B

HIGH POTENTIAL

M/B 

MODERATE POTENTIAL

L/B

LOW

POTENTIAL

H/C

HIGH POTENTIAL

M/C 

MODERATE POTENTIAL

L/C

LOW

POTENTIAL

H/D

HIGH POTENTIAL

M/D

MODERATE POTENTIAL

L/D

LOW POTENTIAL

N/D

NO POTENTIAL

o

cc

o

V)

uu 

cc

A. 

B. 

C. 

D.

B C 

LEVEL OF CERTAINTY

Available information is not adequate for determination of the level of mineral resource potential. 

Available information suggests the level of mineral resource potential. 

Available information gives a good indication of the level of mineral resource potential. 

Available information clearly defines the level of mineral resource potential.

Abstracted with minor modifications from:

Taylor, R. B., and Steven, T. A., 1983, Definition of mineral resource potential: Economic Geology,

v. 78, no. 6, p. 1268-1270. 

Taylor, R. B., Stoneman, R. J., and Marsh, S. P., 1984, An assessment of the mineral resource potential

of the San Isabel National Forest, south-central Colorado: U.S. Geological Survey Bulletin 1638, p.

40-42. 

Goudarzi, G. H., compiler, 1984, Guide to preparation of mineral survey reports on public lands: U.S.

Geological Survey Open-File Report 84-0787, p. 7, 8.

A8
GEOLOGIC TIME CHART 

Terms and boundary ages used by the U.S. Geological Survey in this report

EON

Phanerozoic

Proterozoic

Archean 

pre- Arc

ERA

Cenozoic

Mesozoic

Paleozoic

Late Proterozoic

Middle Proterozoic

Early Proterozoic

Late Archean

Middle Archean

Early Archean 

:hean 2

PERIOD

Quaternary

Tertiary

Neogene 

Subperiod

Paleogene 

Subperiod

Cretaceous

Jurassic

Triassic

Permian

Carboniferous 

Periods

Pennsylvanian

Mississippian

Devonian

Silurian

Ordovician

Cambrian

 -(3800?)- -

EPOCH

Holocene

Pleistocene

Pliocene

Miocene

Oligocene

Eocene

Pateocene

Late 

Early

Late 

Middle 

Early

Late 

Middle 

Early

Late 

Early

Late 

Middle 

Early

Late 

Early

Late 

Middle 

Early

Late 

Middle 

Early

Late 

Middle 

Early

Late 

Middle 

Early

 -

AGE ESTIMATES 

OF BOUNDARIES 

(in Ma)

- 0.010

- 1.7

- R

O A

_ op

v/s/

cc

- 96

.. no

one

- ~240

- 290

OOVJ

_ ocn

- 410

- 4*3R

- 500

_ ~c"7ni

- 900

- 1600

- 2500

JUUU

- 3400

 AKKn 

'Rocks older than 570 Ma also called Precambrian, a time term without specific rank. 

Informal time term without specific rank.

A9
GPO 785-048/48051