Mineral Resources of the Palisade Mesa 

and The Wall Wilderness Study Areas, 

Nye County, Nevada

U.S. GEOLOGICAL SURVEY BULLETIN 1731-B

Chapter B

Mineral Resources of the Palisade Mesa 

and The Wall Wilderness Study Areas, 

Nye County, Nevada

By MICHAEL F. DIGGLES, J. THOMAS NASH, 

DAVID A. PONCE, and DONALD PLOUFF 

U.S. Geological Survey

RICHARD F. KNESS 

U.S. Bureau of Mines

U.S. GEOLOGICAL SURVEY BULLETIN 1731-B

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 Palisade Mesa and The Wall 

Wilderness Study Areas, Nye County, Nevada

U.S. Geological Survey Bulletin 1731-B

Bibliography

Supt. of Docs. No.: I 19.1731-B

1. Mines and mineral resources Nevada Palisade

Mesa Wilderness. 2. Mines and mineral resources 

Nevada Wall Wilderness. 3. Geology Nevada Palisade

Mesa Wilderness. 4 Geology Nevada Wall Wilderness.

5. Palisade Mesa Wilderness (Nev.) 6. Wall

Wilderness (Nev.) I. Diggles, M.F. II. Series.

QE75.B9 No. 1731-B 557.3 s 86-600239

[TN24.C2] [553'09793'34]
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 parts of the Palisade 

Mesa (NV-060-142/162) and The Wall (NV-060-163) Wilderness Study Areas, Nye County, 

Nevada.

Ill

CONTENTS

Summary Bl

Abstract 1

Character and setting 1 

Identified mineral resources 1 

Mineral resource potential 3 

Introduction 3

Location and physiography 3 

Sources of data 3 

Acknowledgments 4 

Appraisal of Identified Resources 4

Mining and mineral exploration history 4 

Mines, prospects, and mineral occurrences 4 

Appraisal of identified resources 4 

Energy resources 4 

Results of field investigation 5 

Assessment of Mineral Resource Potential 5 

Geology 5 

Geochemistry 8 

Methods 8

Results and interpretation 9 

Geophysics 9

Aerial gamma-ray data 9 

Gravity data 9 

Aeromagnetic data 9 

Mineral resource potential 9 

References cited 10 

Appendix 1. Definitions of levels of mineral resource potential and certainty 12

FIGURES

1. Index map showing location of the Palisade Mesa and The Wall Wilderness Study Areas, 

Nye County, Nevada B2

2. Generalized geologic map and areas of mineral resource potential in the Palisade Mesa and The Wall 

Wilderness Study Areas, Nye County, Nevada 6

3. Major elements of mineral resource potential/certainty classification 12

MINERAL RESOURCES OF WILDERNESS STUDY AREAS: CENTRAL NEVADA

Mineral Resources of the Palisade Mesa 

and The Wall Wilderness Study Areas, 

Nye County, Nevada

#y Michael F. Diggles, J. Thomas Nash, David A. Ponce, and Donald Plouff 

U.S. Geological Survey

Richard F. Kness 

U.S. Bureau of Mines

SUMMARY 

Abstract

The parts of the Palisade Mesa (NV-060-142/162) 

and The Wall (NV-060-163) Wilderness Study Areas 

designated as suitable for mineral surveys are 

contiguous Bureau of Land Management Wilderness 

Study Areas in south-central Nevada. Although the 

wilderness study areas are larger, the U.S. Geological 

Survey and the U.S. Bureau of Mines were asked to 

study 66,110 and 30,320 acres, respectively. 

Throughout this report, "wilderness study area" and 

"study area" refer only to those acreages.

No mining activity has occurred within the 

wilderness study areas, or within 2 mi of their 

boundaries. There are no mining claims or identified 

metallic mineral resources present in the study areas. 

The areas around inferred caldera boundaries have low 

resource potential for gold, silver, copper, lead, and 

manganese.

Both the Palisade Mesa and The Wall Wilderness 

Study Areas have low resource potential for petroleum 

and natural gas. An area near the northeast part of 

The Wall Wilderness Study Area has low resource 

potential for geothermal resources. In this report, any 

reference to the Palisade Mesa and The Wall 

Wilderness Study Areas refers only to those parts of 

the wilderness study areas designated by the U.S. 

Bureau of Land Management as suitable for mineral 

surveys.

Character and Setting

The Palisade Mesa and The Wall Wilderness Study 

Areas are contiguous areas in south-central Nevada, 

about 65 mi northeast of Tonopah and about 15 mi east 

of Warm Springs (fig. 1). The part of the Palisade

Mesa Wilderness Study Area designated suitable for 

mineral surveys covers about 66,110 acres and the part 

of The Wall Wilderness Study Area designated suitable 

for mineral surveys covers about 30,320 acres.

The region in which the wilderness study areas 

are located is in the Basin and Range physiographic 

province, which is characterized by subparallel northtrending mountain ranges separated by broad 

alluviated valleys. The study areas are in the southern 

part of the Pancake Range, and are bounded on the 

east by Railroad Valley and on the west by Hot Creek 

Valley. Elevations above sea level range from 

approximately 5,200 to 7,500 ft. A 7-mi-long series of 

northeast-trending dissected mesas named The Wall 

(fig. 1) forms the northwestern border of The Wall 

Wilderness Study Area. Lunar Crater (fig. 1), a 

National Natural Landmark in the northeast Palisade 

Mesa Wilderness Study Area, is an inactive volcanic 

crater.

Rainfall in the region is sparse and streams flow 

intermittently. Lunar Lake (fig. 1), north of The Wall 

Wilderness Study Area, is a playa, a shallow dry-lake 

basin, that is dry for most of the year.

Dirt roads provide access to the wilderness study 

areas from U.S. Highway 6, Nevada State Highway 

375, and the Nyala Road (fig. 1). A dirt road from 

Highway 6 extends south to Lunar Crater and 

continues southward to Buttes Well, forming the 

boundary between the two wilderness study areas.

Identified Mineral Resources

No mineralized areas were identified and no 

evidence of past mining activity or prospecting was 

found in or within 2 mi of the Palisade Mesa and The 

Wall Wilderness Study Areas during field 

reconnaissance in 1984. There has been no recent 

prospecting in either wilderness study area. (The mine

Bl
PALISADE MESA WILDERNESS 

STUDY AREA(NV-060-142/162)

x _ -jo'Storm thermal springs 

{^Coyote Hole thermal springs

THE WALL WILDERNESS 

STUDY AREA (NV-060-163)

Arrowhead 

mining district

Reveille 

Reveille o mining district

Figure 1. Index map showing location of Palisade Mesa (NV-060-142/162) and The Wall 

(NV-060-163) Wilderness Study Areas, Nye County, Nevada.

B2
and spring symbol shown on the l:62,500-scale Lunar 

Crater topographic map inside the northeastern 

Palisade Mesa Wilderness Study Area boundary is a 

hand-dug water well, not a mine). Rock, sand, and 

gravel are present in the wilderness study areas, but 

development of these materials is unlikely because 

similar materials of equal or better quality are 

abundant closer to existing markets.

Mineral Resource Potential

The Palisade Mesa and The Wall Wilderness Study 

Areas have low mineral resource potential for gold, 

silver, copper, lead, and manganese. These base and 

precious metals are not common in rhyolite ash-flow 

sheets anywhere. Where alteration or mineralization 

is associated with caldera collapse, it is a product of 

hydrothermal systems that post-date caldera collapse 

(McKee, 1979). Eruption of Tertiary (about 2 to 6 

million years before present) and Quaternary (about 0 

to 2.2 million years before present) basalts and cinders 

in the study areas occurred during a post-caldera 

igneous event, but it is unlikely that mineralizing 

hydrothermal systems would be associated with 

basaltic volcanism. There is no evidence to indicate 

that alteration or mineralization of older collapse 

structures in the study areas has taken place, although 

the geologic environment is permissive for such 

mineralization. Two caldera-collapse structures are 

inferred to exist near the wilderness study areas, the 

Lunar Lake and the Pancake Range/Williams RidgeHot Creek Valley caldera boundaries. Hence, these 

localities are assigned a low resource potential for 

gold, sliver, copper, lead, and manganese.

Because of the proximity of geothermal 

resources east of The Wall Wilderness Study Area in 

Railroad Valley (fig. 2), geothermal resources may also 

be present beneath the wilderness study areas, 

although no evidence of their existence has been 

discovered. The area near the eastern edge of the 

Pancake Range on the northeast side of The Wall 

Wilderness Study Area has low resource potential for 

geothermal resources.

As of December, 1984, 5,500 acres in the 

Palisade Mesa Wilderness Study Area and 8,000 acres 

in The Wall Wilderness Study Area are under lease for 

oil and gas exploration. A dry borehole 9 mi northeast 

of The Wall Wilderness Study Area represents the only 

known exploration for hydrocarbons near the 

wilderness study areas. However, because possible 

source rocks may be of favorable maturity and because 

of their proximity to existing oil fields, both 

wilderness study areas have low resource potential for 

petroleum and natural gas.

Industrial grade rock, sand, and gravel are 

present in the wilderness study areas, although their 

development is unlikely because of remoteness from 

markets.

INTRODUCTION 

Location and Physiography

The contiguous Palisade Mesa and The Wall 

Wilderness Study Areas are located in south-central

Nevada, about 65 mi northeast of Tonopah and about 

15 mi east of Warm Springs (fig. 1). The parts of the 

Palisade Mesa Wilderness Study Area studied covers 

about 66,110 acres and the part of The Wall Wilderness 

Study Area studied covers about 30,320 acres. 

Unimproved roads that lead from U.S. Highway 6, 

Nevada State Highway 375, and the Nyala Road 

provide access to the study areas. An unimproved road 

that extends south from Highway 6 to Lunar Crater 

continues south to Buttes Well, forming the boundary 

between the two wilderness study areas.

The wilderness study areas are located in the 

Basin and Range physiographic province, which is 

characterized by north-trending subparallel mountain 

ranges separated by broad alluviated valleys. The 

study areas are in the southern part of the Pancake 

Range and are bounded on the east by Railroad Valley 

and on the west by Hot Creek Valley. Elevations range 

from about 5,200 ft in Railroad Valley to 7,503 ft at 

Citadel Mountain near the western boundary of the 

Palisade Mesa Wilderness Study Area; the latter is 

named for a large mesa at its northern end. The Wall 

Wilderness Study Area derives its name from, and is 

bounded in part by, a prominent 20-mi-long northeasttrending series of mesas ranging in elevation from 

6,450 to 6,750 ft.

Lunar Crater (figs. 1 and 2), a low, inactive 

volcanic crater inside the northeast boundary of the 

Palisade Mesa Wilderness Study Area, is designated as 

a National Natural Landmark. Lunar Lake (figs. 1 and 

2) is a shallow dry-lake basin, or playa, located along 

the northwest boundary of The Wall Wilderness Study 

Area.

The climate in the region is semiarid to arid, 

rainfall averaging about 7 in./year (Scott, 1969); 

streams flow intermittently.

Sources of Data

Studies of the general geology of the region 

include those by Kleinhampl and Ziony (1967 and 1985), 

Scott and Trask (1971), Bergman (1982), Turrin and 

Dohrenwend (1984), and Turrin and others (1985). 

Geologic maps that cover the wilderness study areas 

include those by Ekren and others (1973) and Snyder 

and others (1972). Studies by Krai (1951) and 

Kleinhampl and Ziony (1984) provide mineral resource 

data.

A literature search was conducted by the authors 

for additional geologic and mining information 

pertinent to the wilderness study areas. National 

Uranium Resource Evaluation (NURE) reports, 

published by the U.S. Department of Energy (Geodata 

International, 1979), were studied in order to locate 

uranium occurrences and radiometric anomalies. Nye 

County records in Tonopah, Nevada, and records on 

file with the U.S. Bureau of Land Management in 

Reno, Nevada, were examined to determine the 

location of mining claims. In addition, U.S. Bureau of 

Land Management records were examined for 

geothermal, petroleum, and natural gas leases.

In 1984, the U.S. Geological Survey collected 

samples of rocks, stream sediment, and nonmagnetic 

heavy-mineral concentrates from 106 sites within the 

two wilderness study areas. The U.S. Bureau of Mines 

took 57 additional rock samples. Chemical analyses of

B3
the minus-sixty-mesh and the panned-concentrate 

fractions of stream sediment were used to help 

identify areas with mineral resource potential.

Acknowledgments

Frank J. Kleinhampl provided geological advice 

during field work.

Appointments of field assistants were based on 

recommendations by the National Association of 

Geology Teachers. Students employed through the 

program were Diane E. Clemens, Richard Graff, and 

Elizabeth Rochette. Others who provided assistance in 

the field are James A. Saunders, Robert J. Fair field, 

Jr., Victoria E. Langenheim, and Robert E. Tucker. 

U.S. Bureau of Mines field work was carried out with 

the assistance of John T. Neubert and Robert A. 

Welsh.

APPRAISAL OF IDENTIFIED RESOURCES

By Richard F. Kness, U.S. Bureau of Mines

Mining and Mineral Exploration History

No mining has occurred in, or within 2 mi of 

either wilderness study area, but antimony, copper, 

gold, lead, silver, and zinc have been mined or 

prospected about 15 mi to the north.

Mines, Prospects, and Mineral Occurrences

No mining claims are located in the wilderness 

study areas. The nearest mining claims are 2.5 mi 

southwest of the Palisade Mesa Wilderness Study Area 

and 2.5 mi northeast of The Wall Wilderness Study 

Area. The Arrowhead, Reveille, Silverton, and Tybo 

mining districts (fig. 1) are located 10 to 15 mi from 

the wilderness study areas and contain the only known 

mineral deposits in the region (Schilling, 1976). Mining 

began in 1865 when gold and silver were discovered 

near Tybo. In 1867, silver and lead were discovered 

near the site of Reveille. Mineralization in the 

Arrowhead district was discovered in 1919. 

Information on history and production in these nearby 

mining districts was reported by Krai (1951) and 

Kleinhampl and Ziony (1984).

The Arrowhead and Reveille mining districts (9 

and 12 mi south of the wilderness study areas, 

respectively) are geologically similar. In the 

Arrowhead district, silver was mined from argentiteand pyrargyrite-bearing veins within fault zones that 

crosscut Tertiary volcanic rocks. Recorded production 

from both districts between 1920 and 1939 was 225 

tons valued at $4,755 (Krai, 1951). Mineral 

occurrences are in veins along faults and in 

replacement bodies near the contacts between 

Paleozoic sedimentary rocks and Tertiary volcanic 

rocks. Ore minerals within the Reveille district are 

argentiferous galena (PbS), cerargyrite (AgCl), 

cerussite (PbCOo), and stibnite (Sb2 So). Production 

records for the Reveille district are incomplete, but

from 1866 to 1946 recorded production (Au, Ag, Cu, 

Pb, Sb, and Zn) was 8,261 tons of ore valued at 

approximately $613,000 (Krai, 1951).

In the Silverton district, about 12 mi northeast of 

the wilderness study areas, silver occurs in 

replacement bodies in Paleozoic limestones near the 

contact with Tertiary rhyolitic dikes and sills. Small 

shipments of ore assayed at 10 to 30 oz of silver per 

ton were made during the 1930's (Krai, 1951).

In the Tybo district, about 12 mi west of the 

wilderness study areas, mineralized veins have 

replaced Tertiary quartz-latite-porphyry dikes that 

occurred within faults in Paleozoic sedimentary 

rocks. Veins contain calcite, chalcopyrite, pyrite, 

quartz, sphalerite, and argentiferous galena. From 

1874 to 1944, total recorded production was about 

600,000 tons valued at about $9,800,000 (Krai, 195).

Although several borrow pits are located in 

alluvium and basalt cinders that are present along U.S. 

Highway 6 and Nevada State Highway 375, no such 

workings were found within the wilderness study 

areas.

Appraisal of Identified Resources

No mineralized areas were identified and no 

evidence of past mining activity or prospecting is 

evident in or within 2 mi of the Palisade Mesa and The 

Wall Wilderness Study Areas. The mine and spring 

symbol shown on the 1:62,500 scale Lunar Crater 

topographic quadrangle (U.S. Geological Survey, 1967), 

at the northeastern edge of the Palisade Mesa 

Wilderness Study Area, is a hand-dug water well, not a 

mine.

Petroleum and natural gas exploration is not 

known to have occurred in either wilderness study 

area; however, a borehole drilled to a depth of 1,711 ft 

about 9 mi northeast of The Wall Wilderness Study 

Area boundary in Railroad Valley came up dry. As of 

December, 1984, 5,500 acres in the Palisade Mesa 

Wilderness Study Area and 8,000 acres in The Wall 

Wilderness Study Area are under lease for oil and gas 

exploration (Kness, 1985).

Energy Resources

Sandberg (1983) evaluated the petroleum and 

natural gas resources of wilderness lands in Nevada 

using the presence of source and reservoir rocks, the 

maturation history, and the presence of structural and 

stratigraphic traps as the major parameters governing 

the accumulation of petroleum and natural gas. 

Although this report initially rated the wilderness 

study areas as having no potentialfor petroleum and 

natural gas, C.A. Sandberg (oral commun., 1986) 

subsequently revised the rating to that of low 

potential.

Railroad Valley, to the east of The Wall 

Wilderness Study Area, is the major oil producing area 

in Nevada. The Trap Spring field is the nearest oil 

field, about 22 mi northeast of the wilderness study 

area. Production occurs in a structural and 

stratigraphic trap in ash-flow tuff reservoir rock 

consisting of the Tertiary Pritchards Station

B4
Formation (Duey, 1979). Structure is controlled by the 

down-thrown side of the fault that bounds Railroad 

Valley (Duey, 1979). Other fields in Railroad Valley 

consist of the Current, Eagle Springs, and the recently 

discovered Grant Canyon field.

The Railroad Valley geothermal area is 0.25 mi 

outside the eastern boundary of The Wall Wilderness 

Study Area; however, no geothermal leases or lease 

applications are located within either wilderness study 

area. Thermal springs and wells in Railroad Valley 

occur mainly along the margins of the valley, either 

coincident with, or basinward from Basin and Range 

faults. Abel, Chimney Springs, Coyote Hole, and 

Storm Springs are thermal springs that occur along the 

trend of a northeast-striking fault outside The Wall 

Wilderness Study Area. The temperatures of the 

thermal springs range from 84° to 160° F. (Garside and 

Schilling, 1979). No thermal springs, travertine, or 

similar deposits were observed during the field study in 

the wilderness study areas.

Results of Field Investigation

U.S. Bureau of Mines field studies included 

ground reconnaissance and a helicopter overflight of 

the wilderness study areas. A total of 57 rock samples 

were collected. Twenty-six chip and grab samples, 6 

panned-concentrate samples, and 13 stream-sediment 

samples were collected in and near the Palisade Mesa 

Wilderness Study Area; 4 panned-concentrate and 8 

stream-sediment samples were collected in and near 

The Wall Wilderness Study Area. Chip samples were 

collected across suspected mineralized structures. 

Panned-concentrate samples of black sands were 

collected in stream beds. Stream-sediment samples 

collected from larger drainages were assessed for tin 

or mineralized rock related to mapped faults. 

Sampling sites and analytical data are shown by Kness 

(1985).

Analyses for gold, silver, and tin were done by 

fire assay and atomic-absorption methods. 

Semiquantitative spectrographic analyses 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 were 

performed on all samples. Results of the U.S. Bureau 

of Mines1 analyses are available for public inspection 

at the Bureau of Mines, Intermountain Field 

Operations Center, Denver, Colo.

A reconnaissance study of Tertiary volcanic 

centers in Nevada (Albers and Kleinhampl, 1970) 

suggests that the two calderas in the area, the 

Pancake Range/Williams Ridge-Hot Creek Valley 

caldera and the Lunar Lake caldera, contain no 

significant mineral deposit; our field investigation 

confirms this.

Granite throughout the world contains an 

average concentration of 3 parts per million (ppm) tin, 

and values of 20 ppm may indicate tin-mineralized 

granites (Levinson, 1980). Ash-flow tuff exposed in 

the wilderness study areas is rhyolitic to quartz-latitic 

(the fine-grained equivalent of granite) in 

composition. Eighteen rock samples contained 

between 5 and 14 ppm tin. Tin concentrations were

not detected in the other rock samples. The highest 

concentration is 36 ppm tin. The sample with greater 

than 20 ppm tin is not significant because it is a 

single-point anomaly.

Epithermal gold-silver veins in faults related to 

calderas and tin-bearing rhyolites are the deposit types 

that occasionally form in geologic environments 

similar to those of the wilderness study areas. Surface 

indicators of epithermal mineralization may include 

silicified fault zones, stock work quartz veins, silicified 

and pyritized vent breccia, and propylitic alteration 

(chlorite, calcite, and pyrite). None of these 

indicators were observed along the fault traces in 

Monocline Canyon in the Palisade Mesa Wilderness 

Study Area. The N. 50° E.-striking Monocline Canyon 

fault and a N. 10° E.-striking fault can be traced on 

the surface for approximately 1.25 and 0.75 mi, 

respectively. Except for small patches of silica crust 

just outside the Palisade Mesa Wilderness Study Area 

(Kness, 1985), no surface indicators of epithermal 

mineralization were noted in either wilderness study 

area.

Pathfinder (mobile) elements may be closely 

associated with, and may assist in finding, mineral 

occurrences or deposits. Analytical data (Kness, 1985) 

show no anomalous concentrations of pathfinder or 

precious metals in the areas studied. Pathfinder 

elements for epithermal gold-silver veins are 

antimony, arsenic, bismuth, and silver (Rose and 

others, 1979; Levinson, 1980). Other elements 

associated with epithermal gold-silver veins, but not 

observed in this study, are copper, gold, lead, mercury, 

tellurium, thallium, uranium, and zinc (Berger, 1982).

Ten panned-concentrate samples of stream 

gravels and 21 stream-sediment samples were 

collected from drainages in and near the wilderness 

study areas to determine if pathfinder elements are 

related to possibly mineralized faults. Analytical data 

(Kness, 1985) did not indicate the presence of any of 

these elements in the areas studied.

Antimony, bismuth, copper, gold, lead, and silver 

were not detected. Although arsenic, tellurium, and 

zinc are present, the concentration and distribution of 

these elements is not indicative of the presence of 

near-surface mineral deposits.

Basalt and cinders in the Lunar Crater volcanic 

field are sources of aggregate and crushed stone. 

Construction materials have a high bulk-to-value ratio 

that restricts the use or market area. Transportation 

costs generally limit use of such deposits to under 

30 mi.

Rock, sand, and gravel are present in the 

wilderness study areas, 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 M.F. Diggles, J. Thomas Nash, David A. Ponce, and 

Donald Plouf f, U.S. Geological Survey

Geology

Silicic volcanic rocks of Tertiary age, basaltic

B5
38°30

116°00'

38° 15

7 

1 Big Sand Springs Valley

L/B Petroleum

and 

natural gas

THE WALL WILDERNESS 

STUDY AREA (NV060-163)

^

PALISADE MESA \r^nMr^r*r* f* -r't T r\ * jFALlbAUh MhbA 

WILDERNESS STUDY 

AREA (NV-060-142/162)

Figure 2. Map showing genralized geology and mineral resource potential of the Palisade Mesa and The 

Wall Wilderness Study Areas. Nevada.

B6
EXPLANATION

AREA WITH LOW RESOURCE POTENTIAL-Commodities as shown. See

appendix 1 and figure 3 for definition of levels of mineral resource potential

COMMODITIES

Petroleum and natural gas

Geothermal 

Ag Silver 

Au Gold 

Cu Copper 

Mn Manganese 

Pb Lead

CORRELATION OF MAP UNITS 

T- Holocene

QTa QTb J- Pleistocene and Pliocene

Unconformity

t- Miocene and Oligoccnc

-QUATERNARY AND TERTIARY

- TERTIARY

DESCRIPTION OF MAP UNITS 

QTa Alluvium (Holocene, Pleistocene, and Pliocene) 

QTb Basalt (Pleistocene and Pliocene) 

Tt Tuff (Oligocene and Miocene)

MAP SYMBOLS

 Contact-Dashed where approximately located

-- Fault-Dashed where approximately located; 

dotted where concealed

Boundary of Railroad Valley geothermal area 

Inferred caldera boundary 

Dirt road

Geology from Ekren and others (1972) and 

Ekren and others (1973).

Figure 2. Continued.

B7
flows of Tertiary and Quaternary age, and sediments 

of Tertiary and Quaternary age are the dominant 

stratigraphic units of the Palisade Mesa and The Wall 

Wilderness Study Areas (fig. 2). The oldest rocks in 

the study areas are 27 to 7 Ma (Ekren and others, 1971) 

and comprise thick sequences of felsic ash-flow tuffs. 

These are overlain by basaltic flows of the Lunar 

Crater volcanic field that range in age from 3.8 to 

0.13 Ma (Turrin and others, 1985). About one third of 

both study areas are covered with alluvium and 

colluvium deposited on pediment surfaces and valleyfill, lake, and landslide deposits.

Nine ash-flow tuff units in the Pancake Range 

were mapped by Ekren and others (1972; 1973) and 

Snyder and others (1972). The oldest is the tuff of 

Halligan Mesa, a massive, light-gray rhyolitic welded 

tuff that weathers pale buff. The tuff of Palisade 

Mesa is a medium-gray rhyolitic welded tuff that 

weathers reddish-gray to brown and has prominent 

vertical columnar jointing. The Monotony Tuff (Ekren 

and others, 1971) is a medium-purplish-gray devitrified 

rhyodacitic to quartz-latitic welded tuff that weathers 

brown to rust brown. It contains abundant plagioclase, 

quartz, and biotite phenocrysts. The tuff of Shingle 

Pass consists of a reddish-gray devitrified rhyolitic 

welded tuff that weathers red and contains fewer 

phenocrysts than other tuffs in the area. The tuff of 

Lunar Cuesta is a bluish-gray vitric to mostly 

devitrified quartz-latitic welded tuff that weathers 

light brown to buff. The tuff of Buckskin Point is a 

gray dacitic to quartz-latitic welded tuff that 

weathers brownish gray. The tuff of Buckskin Rim 

consists of partially to densely welded light-gray to 

brown rhyolitic to quartz latitic ash-flow tuff and 

vitric nonwelded tuff that weather brown to buff. The 

tuff of Black Beauty Mesa is a densely welded quartzlatitic to rhyodacitic tuff that is black where 

vitrophyric, and red-brown where devitrified. It forms 

cliffs with steps of tuff ace ous sandstone. The 

youngest tuff unit in the area is reddish gray graniteweathering tuff that is partly to densely welded 

devitrified rhyolitic tuff that weathers dark brown to 

reddish brown. All the tuff units are exposed in fault 

blocks tilted generally eastward; their cumulative 

thickness in the wilderness study areas is about 8,000 

ft (Scott and Trask, 1971).

The ash-flow tuffs, dated at 5.8 to 0.13 Ma, are 

overlain by basaltic flows of the Lunar Crater volcanic 

field (Turrin and Dohrenwend, 1984), which show a 

regular and continuous compositional evolution (Turrin 

and others, 1985). Little or no tilting or uplift 

occurred in the Pancake Range during Quaternary time 

(Turrin and Dohrenwend, 1984). Structures in the area 

consist of mild folds, generally eastward-trending preQuaternary tilted layers of Tertiary rocks, some 

northeast-trending faults, and inferred caldera 

structures.

There are two inferred caldera boundaries within 

and near the wilderness study areas: the Pancake 

Range/Williams Ridge-Hot Creek Valley caldera 

boundary (Ekren and others, 1976), which lies outside 

of and encircles the wilderness study areas; and the 

more striking structure known as The Wall, which 

Scott (1969) mapped as the edge of the Lunar Lake 

caldera. This geologic environment is permissive for 

epi thermal gold-sliver-copper-lead-manganese

mineralization similar to that occasionally associated 

with caldera fracture systems elsewhere in Nevada. 

However, McKee (1979) points out that such 

mineralization is usually the result of later 

hydrothermal-fluid circulation taking place along the 

pre-existing structure.

Geochemistry

Methods

Rock, stream-sediment, and nonmagnetic heavymineral samples were collected at 106 sites in the 

conterminous Palisade Mesa and the Wall Wilderness 

Study Areas in 1984 by U.S. Geological Survey 

personnel. The sampling and analytical procedures are 

described and the analytical data are listed in Siems 

and others (1986b).

Geochemical analyses of stream-sediment 

samples reflect the mineral content of rocks 

underlying the drainage basin upstream from the 

sample site. Two media were analyzed for each 

sample collected from recently active stream 

sediment: the minus-sixty-mesh (less than 0.25 mm) 

fraction and the unsieved nonmagnetic heavy-mineral 

fraction. The heavy-mineral fraction is used because 

it concentrates minerals that are associated with 

alteration and mineralization processes. Results of 

these analyses are used to identify areas with unusual 

geochemistry, an important step in identifying areas 

with mineral resource potential.

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). When using the 

spectrographic method, antimony, arsenic, bismuth, 

cadmium, and zinc have high lower limits of 

detection. Therefore, an atomic absorption analytical 

technique (modified from Viets, 1978) was used to 

search for these elements in rock and stream-sediment 

samples. The locations of sampling sites and the 

analytical data were presented by Siems and others 

(1986b).

The interpretation of the geochemical data from 

the wilderness study areas is done in a regional context 

by comparison with the geochemical signatures of 

known deposits and mining areas in the region in which 

similar geochemical techniques were used. The 

regional context for this interpretation is provided by 

U.S. Geological Survey geochemical studies in the 

Tonopah 1° by 2° quadrangle (Fairfield and others, 

1985; Siems and others, 1986a) that include analysis of 

more than 1,200 samples of stream sediments, an equal 

number of heavy-mineral concentrates, and more than 

2,000 samples of mineralized rocks from mines and 

prospects. Sites characterized by anomalous 

concentrations of one or more elements in both sample 

media are considered especially useful. Sites 

characterized by multiple-element associations that 

are consistent with geochemical theory or have been 

recognized in known ore deposits in the region are 

considered the most reliable indicators for mineral

B8
resource assessment.

Results and Interpretation

Geochemical data for the study areas, after 

making the above comparison, show no unusual 

concentrations of elements; they reveal no significant 

areas of alteration or mineralization. Although seven 

sites characterized by zinc concentrations greater 

than 200 ppm in the stream sediments were found, no 

unusual concentrations of other elements were found 

in either the stream-sediment or panned-concentrate 

samples. Such zinc concentrations are not unusual, 

however, and experience has shown that the anomalous 

values probably reflect silicate minerals derived from 

the volcanic rocks and are not indicative of the 

presence of mineralized rock.

Geophysics

Aerial Gamma-ray Data

The U.S. Department of Energy conducted a 

regional aerial gamma-ray spectrometric survey of the 

two wilderness study areas as part of the NURE 

program. Four flight lines, one running north-south 

and three east-west, spaced at 3-mi intervals and 

flown 400 ft above terrain, traversed the area 

(Geodata International, Inc., 1979). Evaluation of data 

acquired by the survey was made by J.S. Duval 

(written commun., 1985) utilizing techniques described 

by Duval (1983). Concentrations encountered in the 

wilderness study areas are 1.5 to 3.0 percent 

potassium, 2.4 to 3.3 ppm equivalent uranium, and 10 

to 15 ppm equivalent thorium. A moderately strong 

potassium anomaly occurs in the eastern part of the 

wilderness study areas and a moderately strong 

thorium anomaly occurs north of the study areas, but 

there are no uranium anomalies in or near the two 

wilderness study areas.

Gravity Data

D.A. Ponce prepared a regional Bouguer gravity 

map of the wilderness study areas at a scale of 

1:62,500 (D.A. Ponce, unpub. data, 1985) using existing 

data (Healey and others, 1981; Snyder and others, 

1984) at a reduction density of 2.67 mg/m . Gravity 

data coverage is excellent throughout the study areas; 

measurements were spaced at intervals of about 1 mi 

or less along many of the traverses. A conspicuous 

feature on the map is an elongate, north-northeasttrending gravity low centered east of Lunar Crater. 

This low (amplitude about 6 mGal) is about 3 mi wide 

and 8 mi long. A Bouguer gravity-anomaly map 

prepared at a reduction density of 2.30 mg/m (D.A. 

Ponce, unpub. data, 1985) indicates that this low has a 

roughly circular shape and is about 5 mi in diameter. 

The gravity low near Lunar Crater only overlies the 

southern part of the Lunar Lake caldera, suggesting 

that Tertiary volcanic rocks are thicker and the 

caldera deeper near its southern boundary. Other 

subcircular gravity lows near Lunar Crater probably

reflect low-density volcanic rocks and sediments 

within the central Nevada caldera complex (Ekren and 

others, 1974). For example, a 4-mGal gravity low at 

Black Beauty Mesa may be part of a separate 

caldera.

A 5-mi-diameter gravity high is located near the 

southern tip of The Wall Wilderness Study Area. 

Although the amplitude of the closed contour of the 

gravity high is 5 mGal, it forms the northernmost nose 

of a north-trending high that is 10 to 15 mGal higher 

than the surrounding region. A steep gravity gradient 

that separates the gravity high from the Pancake 

Range in the wilderness study areas, indicates the 

existence of a steep contact between near-surface 

pre-Tertiary basement rocks beneath the thick 

Tertiary volcanic rocks of the caldera complex to the 

north.

Aeromagnetic Data

Aeromagnetic data include a survey flown at 500 

ft above ground level over both wilderness study areas 

with east-trending flightlines spaced about 1 mi apart 

(U.S. Geological Survey, 1968) and a survey in the 

eastern part of the study areas flown at 1,000 ft above 

ground level with east-trending flightlines spaced at 

0.5 mi intervals (U.S. Geological Survey, 1978). The 

aeromagnetic map of the study areas is generally 

complex, and anomalies are associated with variations 

in relatively magnetic Tertiary volcanic rocks. 

Anomalies are generally of low amplitude and 

correlate with mapped geologic units. The irregular 

pattern of the aeromagnetic map reflects topography 

and sharp changes of rock magnetization of 

moderately to intensely magnetized Tertiary volcanic 

rocks over short distances. The anomaly pattern is 

irregular because some of the volcanic rocks are 

reversely magnetized (Ekren and others, 1974), 

creating intense local lows that interrupt the combined 

positive effects of magnetic susceptibility and normal 

remnant magnetization in rocks of the surrounding 

volcanic terrane.

A prominent feature of the aeromagnetic map is 

a 4-mi-wide belt of elongate north-northeast-trending 

magnetic anomalies extending from Lunar Crater to 

the southwest edge of the Palisade Mesa Wilderness 

Study Area. This pattern correlates with a chain of 

cinder cones, vents, faults, and joints along fault zones 

(Scott and Trask, 1971; Ekren and others, 1974).

Another prominent feature of the aeromagnetic 

map is an anomaly that coincides with the arcuate 

trend of The Wall. This anomaly correlates with the 

eastern boundary of the inferred Lunar Lake caldera 

and thus delineates a major structural boundary. 

Farther east, a broad, featureless magnetic pattern 

coincides with the location of a 20-mGal gravity high 

and reflects the low magnetization of exposed 

Paleozoic rocks.

Mineral Resource Potential

The geology, geochemistry, and geophysics of the 

Palisade Mesa and The Wall Wilderness Study Areas 

indicate a relatively simple and unaltered volcanic pile

B9
with no indications of exposed or buried mineral 

deposits. Concentrations of base (copper and lead) and 

precious (gold and silver) metals are uncommon in 

rhyolite ash-flow tuffs. Where ore deposits are 

associated with caldera collapse, they are usually a 

product of younger hydrothermal systems (McKee, 

1979). Eruption of the Tertiary and Quaternary basalts 

in the two study areas represents a later thermal 

event, but no evidence exists that alteration along the 

older collapse structures occurred. In addition, 

basaltic magmas are unlikely sources of significant 

mineralizing hydrothermal systems. Metals known to 

occur in flows, tuff, breccias, and agglomerates 

include gold, silver, copper, lead, and manganese and 

are considered in a subaerial volcanogenic mineral 

deposit model developed by Cox (1983). 

Concentrations of these metals, however, tend to 

occur in rocks emplaced at greater depth where 

secondary alteration of existing collapse structures has 

taken place (McKee, 1979). Although the geologic 

environment in the two study areas is permissive for 

mineralization, evidence is insufficient to establish 

precisely the likelihood of resource occurrence. The 

areas along the inferred boundaries of the Lunar Lake 

and Pancake Range/Williams Ridge/Hot Creek Valley 

calderas are therefore assigned a low resource 

potential for gold, silver, copper, lead, and manganese 

with a certainty of B. See Appendix 1 and figure 3 for 

the definition of levels of mineral resource potential 

and certainty of assessment.

Geothermal resources exist outside The Wall 

Wilderness Study Area in Railroad Valley where 

thermal springs and wells are present along or 

basinward of major Basin and Range faults. 

Geothermal resources may occur at depth within the 

wilderness study areas. The area near the range front 

to the northeast of The Wall Wilderness Study Area has 

low resource potential for geothermal resources with a 

certainty of C.

The Palisade Mesa and The Wall Wilderness Study 

Areas have low potential for petroleum and natural gas 

resources. The two wilderness study areas are located 

in a "cold spot" (Sandberg and Gutschick, 1977), an 

area without excessive heating. Therefore, the source 

rocks are considered to be at optimum maturation for 

petroleum and natural gas generation (Sandberg, 

1983). According to Picard (1960), the source beds in 

existing fields in Railroad Valley may consist of 

Paleozoic rocks and (or) Cretaceous or Paleogene 

lacustrine rocks. These rocks may also be present at 

depth in the wilderness study areas. The only known 

drilling for hydrocarbons in close proximity to either 

wilderness study area resulted in a dry hole 9 mi 

northeast of The Wall Wilderness Study Area. Because 

of the optimum maturity of source rocks and proximity 

to producing oil fields, the wilderness study areas have 

low resource potential with a certainty of B for 

petroleum and natural gas (C.A. Sandberg, oral 

commun., 1986).

Rock, sand, and gravel are present in the 

wilderness study areas but development of these 

materials is unlikely because similar materials of equal 

or better quality are abundant closer to existing 

markets.

REFERENCES CITED

Albers, J.P., and Kleinhampl, F.J., 1970, Spatial 

relation of mineral deposits to Tertiary volcanic 

centers in Nevada: U.S. Geological Survey 

Professional Paper 700-C, p. C1-C10.

Berger, B.R., 1982, The geological attributes of AuAg-base metal epithermal deposits in Erickson, 

R.L., ed., Characteristics of mineral deposit 

occurrences: U.S. Geological Survey Open-File 

Report 82-795, p. 119-126.

Bergman, S.C., 1982, Petrogenetic aspects of the 

alkali basaltic lavas and included megacrysts and 

nodules from the Lunar Crater volcanic field, 

Nevada, USA: unpublished Ph.D. thesis, 

Prince ton University, 432 p.

Cox, D.P., ed., 1983, U.S. Geological SurveyIngeominas mineral resource assessment of 

Colombia: additional deposit models: U.S. 

Geological Survey Open-File Report 83-901, 31

PDuey, H.D., 1979, Trap Spring oil field, Nye County, 

Nevada, in Newman, G.W., and Goode, H.D., 

eds., Basin and Range symposium and Great 

Basin field conference: Rocky Mountain 

Association Geologists and Utah Geological 

Association, p. 469-476.

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 Nobel, 

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., Bucknam, R.C., Carr, W.J., Dixon, G.L., 

and Quinlivan, W.D., 1976, East-trending 

structural lineaments in central Nevada: U.S. 

Geological Survey Professional Paper 986, 16 p.

Ekren, E.B., Hinricks, E.N., and Dixon, G.L., 1972, 

Geologic map of the Wall Quadrangle, Nye 

County, Nevada: U.S. Geological Survey 

Miscellaneous Geologic Investigations Map 1-719, 

scale 1:48,000.

Ekren, E.B., Quinlivan, W.D., Snyder, R.P., and 

Kleinhampl, F.J., 1974, Stratigraphy, structure, 

and geologic history, of the Lunar Lake caldera 

of northern Nye County, Nevada: U.S. 

Geological Survey Journal of Research, v. 2, no. 

5, p. 599-608.

Ekren, E.B., Rogers, C.L., and Dixon, 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 1:48,000.

Fairfield, R.J., Jr., Siems, D.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.

Garside, L.J., and Schilling, J.H., 1979, Thermal 

waters of Nevada: Nevada Bureau of Mines and 

Geology, Bulletin 91, Mackay School of Mines

BIO
and University of Nevada, Reno, 163 p.

Geodata International, Inc., 1979, Aerial radiometric 

and magnetic survey, Tonopah national 

topographic map, Nevada: U.S. Department of 

Energy Open-File Report GJBX-104 (79), v. 2.

Grimes, D.J., and Marranzino, A.P. 1968, Directcurrent arc and alternating current spark 

emission spectrographic field methods for the 

semiquantitative analysis of geologic materials: 

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

Healey, D.L., Snyder, D.B., and Wahl, R.R., 1981, 

Bouguer gravity map of Nevada, Tonopah sheet: 

Nevada Bureau of Mines and Geology Map 73, 

scale 1:250,000, 1 sheet.

Kleinhampl, F.J., and Ziony, J.L, 1967, Preliminary 

geologic map of northern Nye County, Nevada: 

U.S. Geological Survey Open-File Report 67-129, 

scale 1:200,000, 2 sheets.

____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. 

Kness, R.F., 1985, Mineral investigation of Palisade

Mesa and The Wall Wilderness Study Areas, Nye

County, Nevada: U.S. Bureau of Mines Open-File

Report MLA 26-85, 27 p. 

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

Nevada: University Nevada Bulletin 45, no. 3,

Nevada State Bureau of Mines and Mackay

School of Mines, 223 p. 

Levinson, A. A., 1980, Introduction to exploration

geochemistry: Applied Publishing, Wilmette, HI.,

924 p. 

McKee, E.H., 1979, Ash-flow sheets and calderas:

their genetic relationship to ore deposits in

Nevada, in_ Chapin, C.E., and Elston, W.E., eds.,

Ash-flow tuffs: Geological Society America

Special Paper 180, p. 205-211. 

Picard, M.D., I960, On the origin of oil, Eagle Springs

field, Nye County, Nevada, in Geology of east

central Nevada: Intermountain Association of

Petroleum Geologists, llth Annual Field

Conference Guidebook, p. 237-244. 

Rose, A.W., Hawkes, H.E., and Webb, J.S., 1979,

Geochemistry in mineral exploration: London,

Academic Press, 657 p. 

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

wilderness lands in Nevada: U.S. Geological

Survey Circular 902-H, p. H1-H11. 

Sandberg, C.A., and Gutschick, R.C., 1977,

Paleotec tonic, biostratigraphic, and economic

significance of Osagean to early Meramecian

starved basin in Utah: U.S. Geological Survey

Open-File Report 77-121, 16 p. 

Schilling, J.H., 1976, Metal mining districts of Nevada,

Nevada Bureau of Mines and Geology, Map 37,

scale 1:1,000,000, 3rd edition.

Scott, D.H., 1969, Geology of the southern Pancake 

Range and Lunar Crater volcanic field, Nye 

County, Nevada: unpublished Ph.D. thesis, 

University California-Los Angeles, 128 p.

Scott, D.H., and Trask, N.J., 1971, Geology of the 

Lunar Crater volcanic field, Nye County, 

Nevada: U.S. Geological Survey Professional 

Paper 599-1, 22 p.

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

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 .

Siems, D.F., Sharkey, J.D., and Tucker, R.E., 1986b, 

Analytical results and sample locality map for 

stream-sediment and panned-concentrate 

samples from the Palisade Mesa and The Wall 

Wilderness Study Areas (NV-060-142/162 and NV060-163), Nye County, Nevada: U.S. Geological 

Survey Open-File Report 86-113, 22 p.

Snyder, R.P., Ekren, E.B., and Dixon, G.L., 1972, 

Geologic map of the Lunar Crater Quadrangle, 

Nye County, Nevada: U.S. Geological Survey 

Miscellaneous Geologic Investigation Map 1-700, 

scale 1:48,000.

Snyder, D.B., Healey, D.L., and Saltus, R.W., 1984, 

Bouguer gravity map of Nevada, Lund sheet: 

Nevada Bureau of Mines and Geology Map 80, 

scale 1:250,000, 1 sheet.

Turrin, B.D., and Dohrenwend, J.C., 1984, K-Ar ages 

of basaltic volcanism in the Lunar Crater 

volcanic field, northern Nye County, Nevada: 

implications for Quaternary tectonism in the 

central Great Basin: abs Geological Society of 

America Abstracts with Programs, v. 16, n. 6, 

p. 79.

Turrin, B.D., Renne, P.R., and Dohrenwend, J.C., 1985, 

Temporal trends in the chemical evolution of 

megacryst-bearing, subalkaline-alkaline basaltic 

lavas from the Lunar Crater volcanic field, Nye 

County, Nevada: abs Geological Society of 

America Abstracts with Programs, v. 17, n. 6, 

p. 14.

U.S. Geological Survey, 1967, Lunar Crater, Nevada 

quadrangle: U.S. Geological Survey 15 Minute 

Series Topographic Map, scale 1:62,500.

___1968, Aeromagnetic map of the Hot Creek Range 

region, south-central Nevada: U.S. Geological 

Survey Geophysical Investigations Map GP-637, 

scale 1:250,000, 1 plate.

___1978, Aeromagnetic map of Quinn Canyon Range, 

Nevada: U.S. Geological Survey Open-File 

Report 78-1457, scale 1:62,500, 2 plates.

Viets, J.G., 1978, Determination of silver, bismuth, 

cadmium, copper, lead, and zinc in geologic 

materials by atomic absorption spectrometry 

with tricaprylmethylammonium chloride: 

Analytical Chemistry, v. 50 p. 1,097-1,101.

Bll
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

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 oy 

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.

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