Mineral Resources of the South Reveille 

Wilderness Study Area, Nye County, Nevada

U.S. GEOLOGICAL SURVEY BULLETIN 1731-C

<x

Chapter C

Mineral Resources of the South Reveille 

Wilderness Study Area, Nye County, Nevada

By MICHAEL F. DIGGLES, JAMES A. SAUNDERS, 

DAVID A. PONCE, and ELIZABETH A. ROCHETTE 

U.S. Geological Survey

JOHN T. NEUBERT 

U.S. Bureau of Mines

U.S. GEOLOGICAL SURVEY BULLETIN 1731-C

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

DONALD PAUL MODEL, Secretary

U.S. GEOLOGICAL SURVEY 

Dallas L. Peck, Director

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1986

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 South Reveille Wilderness Study 

Area, Nye County, Nevada.

(U.S. Geological Survey Bulletin 1731-C)

Bibliography

Supt. of Docs. No.: I 19.3:1731-C

1. Mines and mineral resources Nevada South Reveille

Wilderness. 2. Geology Nevada South Reveille

Wilderness. 3. South Reveille Wilderness (Nev.) I. Diggles,

M.F. II. Series: Geological Survey Bulletin 1731-C.

QE75.B9 No. 1731 C 557.3 s 86-600259

[TN24.N3] [553'.09793'44]
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 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 South 

Reveille (NV-060-112) Wilderness Study Area, Nye County, Nevada.

CONTENTS

Summary

Abstract Cl 

Character and setting 1

Identified mineral resources and mineral resource potential 1 

Introduction 1

Location and physiography 1 

Procedures and sources of data 3 

Acknowledgments 3 

Appraisal of identified resources 3

Mining and mineral exploration history 3 

Mines, prospects, and mineral occurrences 6 

Southern tip of the Reveille Range 6 

Industrial rocks and minerals 6 

Identified resources 6 

Assessment of mineral resource potential 6 

Geology 6

Oligocene rocks 6 

Miocene and Pliocene rocks 7 

Structure 7 

Geochemistry 7

Methods 7

Results and interpretation 8 

Geophysics 8

Aerial gamma-ray data 8 

Gravity data 8 

Aeromagnetic data 8 

Mineral resource potential 8 

References cited 9

Appendix 1. Definitions of levels of mineral resource potential and certainty 10 

Geologic time chart 11

FIGURES

1. Index map showing location of the South Reveille Wilderness Study Area, 

Nye County, Nevada C2

2. Generalized geologic map and areas of mineral resource potential in the 

South Reveille Wilderness Study Area, Nye County, Nevada 4

3. Major elements of mineral resource potential/certainty classification 10

MINERAL RESOURCES OF WILDERNESS STUDY AREAS: CENTRAL NEVADA

Mineral Resources of the South Reveille 

Wilderness Study Area, Nye County, Nevada

By Michael F. Diggles, James A. Saunders, 

David A. Ponce, and Elizabeth A. Rochette 

U.S. Geological Survey

John T. Neubert 

U.S. Bureau of Mines

SUMMARY 

Abstract

At the request of the U.S. Bureau of Land 

Management, 33,000 acres of the South Reveille 

Wilderness Study Area in the southern part of the 

Reveille Range in south-central Nevada were studied. 

In this report, the area studied is referred to as "the 

wilderness study area", or simply "the study area." 

Rhyolitic tuff and quartz latite intrusive rocks are the 

dominant rock types. There has been no mining within 

the wilderness study area; however, several mining 

camps, including Reveille and New Reveille in the 

Reveille mining district, lie close-by to the north. 

Near the southern boundary of the study area, a 30-ft 

shaft was sunk in a low-grade gold- and silver-bearing 

quartz vein. No resources were identified in the study 

area.

Field work and geochemical sampling revealed 

one mineralized area that lies astride the southern 

boundary of the study area. Most of the mineralized 

area has low mineral resource potential for gold and 

silver in vein deposits, except for the central core, 

which has moderate resource potential for the same 

metals.

Character and Setting

The study area includes approximately 33,000 

acres in a mountainous part of the southern half of 

the Reveille Range in south-central Nevada (fig. 1). 

The elevation ranges from 8,910 ft at Reveille Peak to 

about 5,160 ft along the eastern boundary of the study 

area. Because the climate in the region is semiarid, 

stream channels are characteristically dry and littered 

with unconsolidated silt- to boulder-sized material.

The Reveille Range, a north-northwest-trending 

uplifted fault block within the Basin and Range 

physiographic province, is bounded by the Reveille 

Valley graben on the west and by the Railroad Valley 

graben on the east. Rocks exposed in the range consist 

of Paleozoic (505 to 245 million years before present 

(Ma)) sedimentary strata and Tertiary (26.1 to 3.8 Ma) 

tuff and basalts (see Geologic Time Chart, last page of 

report). The study area contains only Tertiary rocks.

Identified Mineral Resources and Mineral Resource 

Potential

A single mineralized area was identified in the 

study area. Thte area is located within the 

southernmost 2 mi of the Reveille Range, mostly 

within the study area. It is defined by a gold- and 

silver-bearing quartz vein, highly fractured and 

bleached rhyolite, and a 3,000-ft-long by 1,800-ft-wide 

area of iron-stained rhyolite containing low 

concentrations of arsenic, an element commonly 

associated with gold in this geologic environment. The 

southern 2 mi of the Reveille Range has moderate 

resource potential for gold and silver. The surrounding 

6 mi have low resource potential for the same 

metals.

INTRODUCTION 

Location and Physiography

The South Reveille Wilderness Study Area (NV060-112) covers approximately 106,000 acres, of which 

the U.S. Geological Survey and the U.S. Bureau of 

Mines were asked to study 33,000 acres in the southern 

half of the Reveille Range in southern Nye County,

Cl
37°45' ~

SOUTH REVEILLE WILDERNESS 

STUDY AREA (NV-060-112)

Figure 1. Index map showing location of the South Reveille (NV-060-112) Wilderness Study Area, 

Nye County, Nevada.

C2
about 70 mi east of Tonopah, Nevada (fig. 1). 

Throughout this report, "wilderness study area" and 

"study area" refer only to the smaller area in which 

surveys were conducted. The study area is 

approximately 12 mi long and 5 mi wide. Its eastern, 

southern, and western boundaries coincide with the 

base of the Reveille Range. The northern boundary 

extends across the range about 3.5 mi north of Fang 

Ridge (fig. 2). The highest elevation in the study area 

is Reveille Peak at 8,910 ft (fig. 1); the lowest 

elevation is about 5,160 ft on the eastern boundary of 

the study area. Topography is rugged and 

mountainous. State Highway 375, beginning at Warm 

Springs about 25 mi to the northwest, runs parallel to 

and about 1 mi east of the eastern boundary of the 

study area. County-maintained gravel roads extend 

around the western and southern boundaries of the 

study area (fig. 1). Unmarked, unmaintained jeep 

trails branching from the county roads provide access 

to the base of the mountains. The Reveille Range, a 

north-northwest-trending uplifted fault block of the 

Basin and Range physiographic province, is bounded by 

the Reveille Valley graben on the west and by the 

Railroad Valley graben on the east. Exposed rocks in 

the range consist of Paleozoic sedimentary strata and 

Tertiary tuffs and basalts.

Previous geologic studies pertinent to the South 

study area consist of the following: (1) a geologic and 

mineral resources report of southern Nye County, map 

scale 1:250,000 (Cornwall, 1972); (2) the most recent 

work, a reconnaissance geologic map of the northern 

Kawich and southern Reveille ranges, 1:62,500 scale 

(Gardner and others, 1980); and (3) a report and map of 

the nearby Nellis Air Force base at a scale of 

1:125,000 (Ekren and others, 1971).

Acknowledgments

F.J. Kleinhampl provided geological advice 

during field work. Much assistance in the field was 

made possible by appointments based on 

recommendations of the National Association of 

Geology Teachers (NAGT). Students employed by the 

U.S. Geological Survey through the program were D.E. 

Clemens, Richard Graff, and E.A. Rochette. Others 

who provided assistance in the field were R.J. 

Fairfield, Jr., V.E. Langenheim, Donald Plouff, R.E. 

Tucker, and J.P. Tysl. J.T. Nash reviewed the 

geochemical interpretations in this report. R.F. 

Kness, C.M. Martin, and R.A. Welsh assisted with the 

U.S. Bureau of Mines field work.

Procedures and Sources of Data

In 1984, the U.S. Geological Survey and the U.S. 

Bureau of Mines conducted field work as part of a 

mineral resource investigation of the South Reveille 

Wilderness Study Area. The U.S. Geological Survey 

compiled existing geologic maps, mapped additional 

geologic detail where necessary, and conducted 

regional geophysical and geochemical surveys.

The U.S. Bureau of Mines sampled altered and 

mineralized rocks in and near the wilderness study 

area. Prior to the field work, published and 

unpublished reports and U.S. Bureau of Mines files 

were searched for data pertinent to the geology and 

mining history of the wilderness study area. U.S. 

Bureau of Land Management files and Nye County 

records were also searched for mining claim, oil and 

gas, and geothermal lease information.

Field studies conducted by the U.S. Bureau of 

Mines included a search for potentially mineralized 

areas and examination of the only known prospect near 

the study area, a 30-foot-deep shaft about 500 ft south 

of the southern study area boundary (fig. 2). A total of 

42 stream-sediment, 42 random chip, 8 continuous 

chip, 3 select, and 3 panned-concentrate samples were 

collected by the U.S. Bureau of Mines (Neubert, 

1985). All samples were analyzed for gold and silver 

by the fire-assay inductively coupled plasma technique 

and for 40 elements, including antimony, barium, 

cadmium, cobalt, chromium, copper, gold, iron, lead, 

lithium, magnesium, manganese, molybdenum, nickel, 

platinum, silver, tin, titanium, vanadium, and zinc by 

semiquantitative optical emission spectrography. 

Selected samples were analysed for arsenic and 

antimony by atomic absorption and for uranium by 

fluorimetry.

APPRAISAL OF IDENTIFIED RESOURCES

By John T. Neubert, U.S. Bureau of Mines

Mining and Mineral Exploration History

There has been no apparent mining within the 

study area, but the Reveille mining district lies about 

2 mi to the northwest and claim groups in that district 

extend across the northern boundary of the study 

area. The Reveille district was established in 1866, 

and mines within the district have been worked 

intermittently since that time. Most production 

occurred prior to 1920, by which time 8,261 tons of ore 

worth $610,982 were produced (Krai, 1951). 

Kleinhampl and Ziony (1984) indicated that the district 

has yielded at least $749,000 worth of ore. The 

district produced mostly silver, lead, and minor 

amounts of antimony, copper, and gold.

The study area is underlain by Tertiary rocks, 

whereas Paleozoic sedimentary rocks and Tertiary 

volcanic rocks crop out in the Reveille mining 

district. Most of the mineral deposits in the district 

are associated with Paleozoic strata or are near their 

contact with Tertiary rhyolitic tuff. Mineral 

occurrences are concentrated along the contacts with 

the sedimentary and volcanic rocks, and in faults 

within the Paleozoic and Tertiary rocks, with some 

replacement of sedimentary rocks in favorable beds 

(Krai, 1951).

In contrast to the Reveille mining district, no 

Paleozoic sedimentary rocks crop out in the study 

area. The depth to Paleozoic strata, if any are 

present, is unknown, although geophysical data 

indicate that either they are absent or at great 

depth.

C3
37»55' -

37°50' -

unpatented mining claims 

of Reveille mining district

APPROXIMATE BOUNDARY

OF X

\ SOUTH REVEILLE WILDERNESS 

\ STUDY AREA (NV-060-112) x

Figure 2. Generalized geologic map showing areas of mineral resource potential in the 

South Reveille Wilderness Study Area, Nevada.

C4
EXPLANATION

GEOLOGIC TERRANE HAVING MODERATE MINERAL RESOURCE POTENTIALcertainty level C (M, C). See appendix 1 and figure 3 for definition of levels of 

mineral resource potential and certainty of assessment.

GEOLOGIC TERRANE HAVING LOW MINERAL RESOURCE POTENTIAL, 

certainty level B (L/B)

COMMODITIES 

Ag Silver 

Au Gold

CORRELATION OF MAP UNITS

]- QUATERNARY AND TERTIARY

- Miocene

_ - Oligocene _

- TERTIARY

GEOLOGIC MAP UNITS

QTa Alluvium (Quaternary and Tertiary)

Tb Basalt (Miocene)

Tdr Dacite and Rhyolite (Miocene)

Tql Quartz latite (Miocene)

Tts Tuffaceous sedimentary rocks (Miocene)

Tt Tuff of Reveille Range (Miocene) and Monotony tuff, undivided (Oligocene)

MAP SYMBOLS

 CONTACT

' FAULT-Dotted where concealed, ball and bar on downthrown side

 DIRT ROAD 

B SHAFT

Figure 2. Continued.

C5
Mines, Prospects, and Mineral Occurrences

One mineralized area at the southern tip of the 

Reveille Range contains low gold and silver 

concentrations. The mineralized area lies mostly 

within the study area. Although all or part of the 3 

blocks of mining claims are located within the study 

area (fig. 2), no workings or surface evidence of 

mineralization were identified at the claims. Rock 

suitable for roadfill is present throughout the study 

area.

Southern Tip of the Reveille Range

o

The southern 2 mi of the Reveille Range, within 

and just outside the study area, is mineralized. 

Features described below that define the mineralized 

area consist of the following: 1) a silver- and goldbearing quartz vein, and 2) widespread fracturing and 

alteration.

A silver- and gold-bearing quartz vein within the 

mineralized area is exposed in a 30-ft shaft about 500 

ft south of the study area (fig. 2). This vein is 3 ft 

wide, strikes N. 60° W., and dips 85° SW. Selected 

material from the dump contains 41 parts per million 

(ppm) antimony, 69 ppm arsenic, 0.071 ppm gold, 230 

ppm lead, 25 ppm silver, and 0.06 percent zinc 

(Neubert, 1985). A chip sample collected at an 

outcrop of the vein 375 ft southeast of the shaft 

contains 72 ppm arsenic and 2.3 ppm silver (Neubert, 

1985). At the outcrop, the vein consists of quartz pods 

and stringers with inclusions of rhyolite country rock.

Rhyolite tuff in the mineralized area north of 

the shaft is highly fractured and bleached and contains 

partly kaolinized potassium feldspar. The fractures 

are subparallel and trend north to northeast. 

Northwest-trending lenses of iron-oxide-stained 

rhyolite as much as 40 ft wide are also present; some 

are silicified. The zone of iron-oxide-stained lenses 

extends from just north of the shaft to 3,000 ft to the 

north.

The Bellehelen lineament (a major regional 

structure discussed later in this report), the preciousmetal-bearing vein at the shaft, and the iron-oxidestained lenses and streaks are parallel to subparallel to 

one another, indicating a possible genetic relationship 

between structures and mineralization. Many 

fractures in the mineralized area are oriented 30° to 

90° from the general trend of the vein and the 

Bellehelen lineament.

Low concentrations of Arsenic, a common 

pathfinder element for gold deposits in the region, are 

present in the low-grade precious-metal vein at the 

shaft and in the bleached and fractured rhyolite inside 

the study area north of the shaft (fig. 2). The area 

containing low concentrations of arsenic is about 3,000 

ft long and 1,800 ft wide and is located within the 

southernmost 2 mi of the study area. Additionally, 

one sample from this area contains 0.017 ppm gold 

(Neubert, 1985).

Industrial Rocks and Minerals

Rhyolite tuff suitable for roadfill, construction,

and other industrial uses is present in the study area, 

but larger, more accessible deposits are available 

outside the area. The rocks of the study area have no 

unique industrial or decorative characteristics.

Identified Resources

o

The southernmost 2 mi of the Reveille Range is 

a mineralized area. A 3,000-ft-long by 1,800-ft-wide 

area of highly fractured and bleached rhyolite 

containing minor gold and silver and low 

concentrations of arsenic is situated in the mineralized 

area in the study area.

Rhyolite tuff, sand, and gravel suitable for 

common construction purposes are present in the study 

area, but development of these materials is unlikely 

because similar materials of equal or better quality 

are abundant closer to existing markets.

ASSESSMENT OF MINERAL RESOURCE POTENTIAL

By Michael F. Biggies, James A. Saunders, David A. 

Ponce, and Elizabeth A. Rochette, U.S. Geological 

Survey

Geology

Most of the rocks of the South Reveille 

Wilderness Study Area consist of areally extensive ashflow tuffs, local hypabyssal rocks, and basalt. Older 

rocks do not crop out in the study area, but to the 

north, these tuffs and all other Tertiary rocks overlie 

and (or) intrude shale, carbonate rocks, and quartzite 

of Ordovician to Permian age. Hypabyssal quartzlatitic rocks of middle(?) Miocene age intrude the tuff 

in the study area. The youngest rocks in the study 

area are olivine basalts that cap several high ridges.

Oligocene Rocks

The most widespread Tertiary unit in southern 

Nye County is the Monotony Tuff (Cornwall, 1972), a 

compound cooling unit composed of densely welded 

devitrified latite tuff that is as much as 1,000 ft 

thick. In this report, the Monotony Tuff is divided into 

an upper member, the coarsely devitrified tuff 

member (equivalent to the tuff of Goblin Knobs of 

Ekren and others, 1973), and a lower member, the 

quartz-latite tuff member. In its overall physical 

appearance, the Monotony Tuff is characterized by 

abundant large books of biotite and large quartz 

phenocrysts (Ekren and others, 1971). Pumice 

fragments are generally inconspicuous. The coarsely 

devitrified tuff member, an intracaldera facies of the 

Monotony Tuff, is the oldest exposed rock unit in the 

study area. The presence of this facies, which is 

coextensive with more widespread and possibly thicker 

tuff deposits (tuff of Goblin Knobs) to the north (Ekren 

and others, 1973), indicates that the Monotony caldera 

lies partly within the study area. This conclusion is 

based on the structural interpretation of the region

C6
(Ekren and others, 1973). Ekren and others (1973) 

described their tuff of Goblin Knobs as a compound 

cooling unit of densely welded, coarsely devitrified 

quartz latitic to rhyolitic welded tuff that is about 

5,000 ft thick. In general, the coarsely devitrified tuff 

member is pumice-rich and contains pumice fragments 

2-6 in long. This rock type is distinguished from 

lithologies more typical of the Monotony Tuff by fewer 

phenocrysts, the presence of sedimentary lithic 

fragments, a higher alkali feldspar-to-plagioclase 

ratio, and less biotite (Ekren and others, 1973). The 

age of the coarsely devitrified tuff member (of the 

Monotony Tuff) is 26.1 ± 0.7 Ma (Ekren and others, 

1973; Kleinhampl and Ziony, 1985).

Miocene and Pliocene Rocks

Miocene tuffaceous sedimentary rocks are found 

within and north of the study area. These rocks 

consist of thin-bedded, tuffaceous fluvial and 

lacustrine sandstone and siltstone that are commonly 

intensely silicified. These strata, totaling as much as 

100 ft in their overall thickness, are interbedded with 

tuff in the Reveille Range and are intruded by quartz 

latite at Fang Ridge.

The tuff of Reveille Range (Ekren and others, 

1973) is as much as 2,000 ft thick within the study 

area. It is made up of at least two cooling units 

composed mostly of densely welded, crystal-rich ashflow tuff containing quartz, plagioclase, and local 

biotite phenocrysts. A well-defined vitrophyre occurs 

at the base of the formation. The tuff of Reveille 

Range is commonly hydrothermally altered at the 

southern end of the study area. A potassium-argon age 

of 20.4 ± 0.3 Ma was determined on sanidine from this 

unit (this report).

Several quartz-latite intrusions are present 

within and north of the study area. The most 

conspicuous of these are at Fang Ridge, where the 

quartz latite is light-gray to buff colored, flow 

layered, and mildly contorted. The quartz latite's 

border zones are glassy and its interior is devitrified 

and coarsely crystalline. A potassium-argon age 

determination of 18.7 Ma was made on biotite from a 

sample of the quartz latite collected north of the 

study area (Ekren and others, 1973).

Extensive Miocene and Pliocene basalt flows cap 

areas of the west piedmont, west flank, and crest of 

the Reveille Range. These flows, each associated with 

a discrete vent, are individually as much as 200 ft 

thick and consist of black to bluish-gray porphyritic 

olivine basalt that contains scattered phenocrysts of 

labradorite. Potassium-argon ages obtained from 12 

whole-rock basalt samples indicate that they occur in 

two age groups with the ranges of 5.8 ± 0.3 to 5.6 ± 0.3 

Ma and 3.9 ± 0.2 to 3.87 ± 0.3 Ma (Dohrenwend and 

others, 1985). Preliminary data indicate that the older 

basalt may include rocks as young as 5.2 ± 0.1 Ma 

(M.F. Diggles, unpub. data, 1986). One of the youngest 

basalt flows conceals one of the range-front faults on 

the west flank of the study area, thus postdating the 

uplift of the range at that location. Elsewhere, rangefront faults cut the basaltic lava flows.

Structure

Structural features in the Reveille Range consist 

of folds and associated thrust faults, strike-slip faults, 

faults related to volcanic activity (such as caldera 

subsidence) and Basin and Range high-angle faults 

(Cornwall, 1972). Basin and Range faulting led to the 

uplift and eastward tilting of the Reveille Range 

during Miocene and Pliocene time. Faults on the west 

side of the range are assigned a minimum age of 4.2 

Ma on the basis of age dates obtained from unfaulted 

basaltic lava flows found there.

It is possible that the 350-mi-long northwesttrending Bellehelen lineament truncates the southern 

end of the Reveille Range where Gardner and others 

(1980) described a dacitic-andesitic lava field south of 

the lineament that is apparently downdropped with 

respect to the Reveille Range. Here the lineament 

coincides with an apparent fault along which the latest 

movement postdates the Basin and Range faulting.

Potassium-argon dates obtained from the basalt 

in the Reveille Range indicate that maximum erosion 

occurred along the crest and upper flank areas of the 

range, and that approximate equilibrium existed in 

midpiedmont areas. Rapid erosion during early phases 

of range dissection was followed by significantly less 

erosion (Dohrenwend and others, 1985).

Bleached and iron-stained rocks are common at 

the southern tip of the Reveille Range, where 

alteration apparently was concentrated along fracture 

zones. There, lava flows and domes of intermediate 

composition characteristically contain feldspar 

phenocrysts partially altered to kaolinite, and the 

altered rocks are locally silicified.

Geochemistry

Methods

In 1984, the U.S. Geological Survey collected 

stream-sediment samples at 26 sites in the study 

area. The sampling and analytical procedures used 

and the data obtained appear in Saunders and Siems 

(1985).

Geochemical analyses of stream-sediment 

samples reflect the chemistry of the rocks that 

underlie the drainage basin upstream from the sample 

site. For this study, we used the nonmagnetic heavymineral concentrate derived from stream-sediment 

samples because this fraction concentrates minerals 

that may be related to mineralizing processes or 

accompanying alteration. Therefore, analyses of the 

concentrates can be used to identify areas with 

unusual geochemistry.

All samples were analyzed for 31 elements, 

including antimony, barium, cadmium, cobalt, 

chromium, copper, gold, iron, lead, magnesium, 

manganese, molybdenum, nickel, silver, thorium, tin, 

titanium, tungsten, vanadium, and zinc, using a sixstep semiquantitative emission spectrographic method 

(Grimes and Marranzino, 1968).

C7
Results and Interpretation

Data from U.S. Geological Survey geochemical 

studies in the adjacent Tonopah 1° by 2° quadrangle, 

that include analyses of more than 2,000 samples of 

mineralized rocks from mines and prospects, more 

than 1,200 samples of stream sediments collected from 

well-distributed sampling sites, and an equal number of 

nonmagnetic heavy-mineral concentrates, provide the 

framework for this geochemical interpretation 

(Fairfield and others, 1985; Siems and others, 1986). 

Thus, we interpret the geochemical results from the 

study area in a regional context by comparison with 

the typical geochemical signatures expressed in stream 

sediments derived from known mineral deposits and 

from mining areas in the region for which we have 

similar geochemical data. This evaluation is focused 

on anomalous concentrations of one or more trace 

elements associated with mineral deposits. In 

addition, multiple-element associations consistent with 

standard geochemical principles or elemental suites 

recognized in known ore deposits in the region are 

considered to be the most diagnostic and reliable for 

mineral assessment.

Rock and stream-sediment geochemical data for 

the study area do not indicate large or significant 

areas of alteration or anomalous concentrations of 

minerals. High concentrations of metallic elements 

were measured in two heavy-mineral concentrate 

samples: 700 ppm zinc in one and 2,000 ppm lead in 

another. According to the regional geochemical 

studies, these are anomalous concentrations. Streamsediment and rock samples were collected from the 

Reveille and New Reveille mining camps to the north 

(Fairfield and others, 1985; Siems and others, 1986). 

These samples were highly enriched in antimony, 

arsenic, copper, and silver. However, no samples from 

within the study area contained these elements.

Geophysics

Aerial Gamma-ray Data

Examination by J.S. Duval (written commun., 

1985) of aerial gamma-ray maps, which include 

composite-color maps (Duval, 1983), provided 

estimates of concentrations of the radioelements 

potassium, equivalent uranium, and equivalent 

thorium. The maps were compiled at a scale of 

1:1,000,000 as part of the National Uranium Resource 

Evaluation program. The study area has a moderate 

overall radioactivity with concentrations of 2.0 to 2.6 

percent potassium, 2.0 to 3.5 ppm equivalent uranium, 

and 9 to 14 ppm equivalent thorium. There are no 

uranium or thorium anomalies within or near the study 

area. A moderate potassium anomaly occurs along the 

east side of the study area (J.S. Duval written 

commun., 1985.).

Gravity Data

D.A. Ponce and J.B. Spielman collected gravity 

data and compiled a regional Bouguer gravity map at a

scale of 1:62,500 (D.A. Ponce, unpub. data, 1985). 

Data coverage is sparse within the study area, 

particularly along the southern Reveille Range. In the 

southeast part of the study area, a gravity low of 

about 2 to 3 milligals (mGal) is associated with a 

prominent magnetic low. Because data coverage is 

sparse and the amplitude of the anomaly is small, 

possible thickening of volcanic rocks or the existence 

of a caldera cannot be confirmed using gravity data.

Aeromagnetic Data

In 1985, a total intensity aeromagnetic survey 

was flown at an altitude of 1,000 ft above terrain 

along east-trending flightlines spaced 0.5 mi apart 

(U.S. Geological Survey, 1985). Although the nominal 

flight altitude was 1,000 ft, the actual flight altitude 

may have varied from about 500 ft to 2,200 ft above 

the ground surface; but variations in flight altitude do 

not significantly correlate with magnetic anomalies, 

indicating that the anomalies are related to rock 

distribution. A previous aeromagnetic survey was 

flown at a constant barometric elevation of 8,000 ft 

above sea level along east-trending flightlines spaced 2 

mi apart (Philbin and White, 1965). The low-level and 

high-level aeromagnetic surveys correlate well, with 

the low-level survey showing greater detail and 

enhanced anomaly resolution.

In the central part of the study area, quartzlatite dikes exposed along Fang Ridge are expressed by 

an elongate east-trending magnetic high.

In the southern part of the Reveille Range, a 3- 

by 4-mi elliptical magnetic low is probably related to 

the tuff of the Reveille Range. A large-amplitude 

magnetic low of about 500 nanoTeslas (nT) is present 

within the larger circular low and is probably caused 

by a combination of the tuff being reversely 

magnetized, the topographic relief, and the abrupt 

termination of magnetic rocks along a fault. Farther 

southeast, a 2- by 2-mi sub-circular magnetic low 

coincides with a poorly defined 2- to 3-mGal gravity 

low. This magnetic anomaly has an amplitude of about 

600 nT and may also be caused by reversely 

magnetized rocks.

Mineral Resource Potential

The South Reveille Wilderness Study Area is 

located south of the Reveille mining district where 

silver and lead were mined. However, the geology of 

the study area differs from that of the mining district 

in that there are neither outcrops nor geophysical 

evidence of Paleozoic rocks, which generally host the 

metal deposits. The lack of a flat magnetic signature 

extending south into the study area indicates that the 

Paleozoic rocks are either absent or are buried at 

great depths.

In the southern 2 mi2 of the Reveille Range, a 

mineralized zone exhibiting widespread alteration and 

fracturing of the host rocks extends into the study 

area. A gold- and silver-bearing quartz vein in the 

mineralized zone is explored by a shaft that is 30-ft 

deep and is situated about 500 ft south of the study

C8
area boundary. Samples collected from its dump by 

the U.S. Bureau of Mines contain anomalous 

concentrations of antimony, gold, lead, silver, and 

zinc, as well as low concentrations of arsenic. The 

southern 2 mi of the Reveille Range contain an area 

of moderate mineral resource potential for gold and 

silver with a certainty level of C. The surrounding 

area has low mineral resource potential for the same 

metals with a certainty level of B. See appendix 1 and 

figure 3 for definitions of levels of mineral resource 

potential and certainty of assessment.

Nearly all of Railroad Valley and much of 

Reveille Valley are leased for oil and gas. Some of 

these leases extend into the northern part of the study 

area, although the closest producing oil field lies about 

55 mi to the north in Railroad Valley. In a report on 

the petroleum potential of wilderness lands in Nevada, 

Sandberg (1983) assigned the South Reveille Wilderness 

Study Area a zero potential for oil and gas because of 

the thick pile of Tertiary volcanic rocks, including 

dikes, and because of the study area's proximity to 

Tertiary calderas in the northern Reveille, Kawich, 

and Quinn Canyon Ranges.

Geothermal resources are not evident in or near 

the study area. Although hot springs are present in 

adjacent ranges, none were observed in the Reveille 

Range. No current geothermal leases exist in the 

South Reveille Wilderness Study Area.

REFERENCES CITED

Cornwall, H.R., 1972, Geology and mineral deposits of 

southern Nye County, Nevada: Nevada Bureau of 

Mines and Geology, Bulletin 77, 49 p.

Dohrenwend, J.C., Turrin, B.D., and Biggies, M.F., 

1985, Topographic distribution of dated basaltic 

lava flows in the Reveille Range, Nye County, 

Nevada: implication for Late Cenozoic erosion 

of upland areas in the Great Basin abs : 

Geological Society of America Abstracts with 

Programs, v. 17, no. 6, p. 352.

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

gamma-ray spectrometric data: Geophysics, v. 

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

Ekren, E.B., Anderson, R.E., Rogers, C.L., and Noble, 

B.C., 1971, Geology of northern Nellis Air Force 

Base Bombing and Gunnery Range, Nye County, 

Nevada: U.S. Geological Survey Professional 

Paper 651, 91 p.

Ekren, E.B., Rogers, C.L., and Bixon, G.L., 1973, 

Geologic and Bouguer gravity map of the 

Reveille quadrangle, Nye County, Nevada: U.S. 

Geological Survey Miscellaneous Geologic 

Investigations, Map 1-806, scale 1:62,500.

Fair field, R.J., Jr., Siems, B.F., Zuker, J.S., Hill, R.H.,

Nash, J.T., and Budge, Susanne, 1985, Analytical 

results and sample locality map of streamsediment samples from the Tonopah 1° x 2° 

quadrangle, Nevada: U.S. Geological Survey 

Open-File Report 85-376, 85 p.

Gardner, J.N., Eddy, A.C., Goff, F.E., Grafft, K.S., 

1980, Reconnaissance geologic map of the 

northern Kawich and southern Reveille ranges, 

Nye County, Nevada: Los Alamos Scientific 

Laboratory and University of California-Bavis, 

LA-8390-MAP or UC-51, scale 1:62,500.

Grimes, B.J., and Marranzino, A.P., 1968, Birectcurrent arc and alternating-current spark 

emission spectrographic field methods for the 

semiquantitative analysis of geologic materials: 

U.S. Geological Survey Circular 591, 6 p.

Neubert, J.T., 1985, Mineral investigation of the South 

Reveille Wilderness Study Area, Nye County, 

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

MLA 37-85, 30 p.

Kleinhampl, F.J., and Ziony, J.I., 1984, Mineral 

resources of northern Nye County, Nevada: 

Nevada Bureau of Mines and Geology Bulletin 

99B, 243 p.

___1985, Geology of northern Nye County, Nevada: 

Nevada Bureau of Mines and Geology Bulletin 

99A, 172 p.

Krai, V.E., 1951, Mineral resources of Nye County, 

Nevada: Nevada Bureau of Mines and Geology, 

Bulletin 45 50 , 223 p.

Philbin, P.W., and White, B.L., Jr., 1965, Aeromagnetic 

map of parts of the Kawich Peak and Reveille 

Peak quadrangles, Nye County, Nevada: U.S. 

Geological Survey Geophysical Investigations 

Map GP-516, scale 1:62,500.

Sandberg, C.A., 1983, Petroleum potential of 

wilderness lands in Nevada: U.S. Geological 

Survey Miscellaneous Investigations Series Map I1542, scale 1:1,000,000.

Saunders, J.A., and Siems, B.F., 1985, Analytical 

results and sample locality map for nonmagnetic 

heavy-mineral concentrates from stream 

sediments from the South Reveille Wilderness 

Study Area (NV-060-112), Nye County, Nevada: 

U.S. Geological Survey Open-File Report 86-95, 

12 p.

Siems, B.F., Marchitti, M.L., and Nash, J.T., 1986, 

Analytical results and sample locality map for 

nonmagnetic heavy-mineral concentrate samples 

from the Tonopah 1° x 2° quadrangle, Nevada, 

U.S. Geological Survey Open-File Report 86-213 

in press .

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

the Reveille Range and vicinity, southern 

Nevada: U.S. Geological Survey Open-File 

Report, scale 1:62,000.

C9
APPENDIX 1. Definition of levels of mineral resource 

potential and certainty of assessment

Mineral resource potential is defined as the 

likelihood of the presence of mineral resources in a 

defined area; it is not a measure of the amount of 

resources or their profitability.

Mineral resources are concentrations of naturally 

occurring solid, liquid, or gaseous materials in such 

form and amount that economic extraction of a commodity from the concentration is currently or potentially feasible.

Low mineral resource potential is assigned to 

areas where geologic, geochemical, and geophysical 

characteristics indicate a geologic environment where 

the existence of resources is unlikely. This level of 

potential embraces areas of dispersed mineralized rock 

as well as areas having few or no indications of 

mineralization. Assignment of low potential requires 

specific positive knowledge; it is not used as a catchall 

for areas where adequate data are lacking.

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 chance for resource 

accumulation, and where an application of genetic and 

(or) occurrence models indicates favorable ground.

High mineral resource potential is assigned to 

areas where geologic, geochemical, and geophysical 

characteristics indicate a geologic environment 

favorable for resources, where interpretations of data 

indicate a high likelihood for resource accumulation, 

where data support occurrence and (or) genetic models 

indicating presence of resources, and where evidence 

indicates that mineral concentration has taken place. 

Assignment of high resource potential requires positive 

knowledge that resource-forming processes have been 

active in at least part of the area; it does not require 

that occurrences or deposits be identified.

Unknown mineral resource potential is assigned 

to areas where the level of knowledge is so inadequate 

that classification of the area as high, moderate, or

low would be misleading. The phrase "no mineral 

resource potential" applies only to a specific resource 

type in a well-defined area. This phrase is not used if 

there is the slightest possibility of resource 

occurrence; it is not appropriate as the summary 

rating for any area.

Expression of the certainty of the mineral 

resource assessment incorporates a consideration of (1) 

the adequacy of the geologic, geochemical, geophysical, and resource data base available at the time of 

the assessment, (2) the adequacy of the occurrence or 

the genetic model used as the basis for a specific 

evaluation, and (3) an evaluation of the likelihood that 

the expected mineral endowment of the area is, or 

could be, economically extractable.

Levels of certainty of assessment are denoted by 

letters, A-D (fig. 3).

A. The available data are not adequate to 

determine the level of mineral resource potential. 

Level A is used with an assignment of unknown mineral 

resource potential.

B. The available data are adequate to suggest 

the geologic environment and the level of mineral 

resource potential, but either evidence is insufficient 

to establish precisely the likelihood of resource occurrence, or occurrence and (or) genetic models are not 

known well enough for predictive resource assessment.

C. The available data give a good indication of 

the geologic environment and the level of mineral 

resource potential, but additional evidence is needed 

to establish precisely the likelihood of resource occurrence, the activity of resource-forming processes, or 

available occurrence and (or) genetic models are 

minimal for predictive applications.

D. The available data clearly define the geologic 

environment and the level of mineral resource 

potential, and indicate the activity of resourceforming processes. Key evidence to interpret the 

presence or absence of specified types of resources is 

available, and occurrence and (or) genetic models are 

adequate for predictive resource assessment.

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

LEVEL OF CERTAINTY

Figure 3. Major elements of mineral resource potential/certainty classification

CIO
GEOLOGIC TIME CHART 

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

EON

Phanerozoic

Proterozoic

Archean 

pre- Ar

ERA

Cenozoic

Mesozoic

Paleozoic

Late Proterozoic

Middle Proterozoic

Early Proterozoic

Late Archean

Middle Archean

Early Archean 

:hean 2

PERIOD

Quaternary

Neogene 

Subperiod

Tertiary 

Paleogene 

Subperiod

Cretaceous

Jurassic

Triassic

Permian

Pennsylvanian 

Carboniferous

Mississippian

Devonian

Si urian

Ordovician

Cambrian

 -(3800?)- -

EPOCH

Holocene

Pleistocene

Pliocene

Miocene

Oligocene

Eocene

Paleocene

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

- 24

*JO

 tid

- 96 

_ no

one

- 9Qfi

«J«JV/

- 410

- 500

 j/ \j

jv/v/

Mi(\(\

- 2500

<j\j\j\j

- 3400

I AKKn 

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

Informal time term without specific rank.

Cll


GPO 785-048/48013