Mineral Resources of the

Abert Rim Wilderness Study Area,

Lake County, Oregon

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Chapter C

Mineral Resources of the

Abert Rim Wilderness Study Area,

Lake County, Oregon

By MAUREEN G. SHERLOCK, MARK E. GETTINGS, and 

HARLEY D. KING 

U.S. Geological Survey

TERRY R. NEUMANN 

U.S. Bureau of Mines

U.S. GEOLOGICAL SURVEY BULLETIN 1738

MINERAL RESOURCES OF WILDERNESS STUDY AREAS: 

SOUTH-CENTRAL OREGON
DEPARTMENT OF THE INTERIOR 

DONALD PAUL MODEL, Secretary

U.S. GEOLOGICAL SURVEY 

Dallas L. Peck, Director

Any use of trade names and trademarks 

in this publication is for descriptive 

purposes only and does not constitute 

endorsement by the U.S. Geological Survey

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1988

For sale by the

Books and Open-File Reports Section

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Library of Congress Cataloging-in-Publication Data

Mineral resources of the Abert Rim Wilderness Study Area, 

Lake County, Oregon.

(U.S. Geological Survey bulletin ; 1738-C)

(Mineral resources of wilderness study areas southcentral Oregon ; ch. C)

Bibliography: p.

Supt. of Docs, no.: I 19.3:1738-C

1. Mines and mineral resources Oregon Abert Rim 

Wilderness. 2. Abert Rim Wilderness (Or.) I. Sherlock, 

Maureen G. II. Series. III. Series: Mineral resources of 

wilderness study areas south-central Oregon ; ch. C. 

QE75.B9 no. 1738-C 557.3 s 88-600268 

[TN24.07] [553'.09795'93]
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 the Abert Rim Wilderness Study Area 

(OR-001-101), Lake County, Oregon.

CONTENTS

Summary Cl

Abstract Cl 

Character and setting Cl 

Identified mineral resources Cl 

Mineral resource potential C2 

Introduction C3

Location and physiography C3 

Procedures and sources of data C3 

Acknowledgments C5 

Appraisal of identified resources C5

Mining and mineral exploration history C5 

Mines, prospects, mining claims, and leases C5 

Appraisal of identified resources C5 

Assessment of mineral resource potential C5 

Geology C5

Tertiary volcanic rocks C6

Tertiary and Quaternary volcanic and surficial deposits C6

Regional mineralization C7

Structure C7 

Geochemistry C7

Methods C7

Results and interpretations C8 

Geophysics C8

Aeromagnetic data C8

Gravity data C8

Remote sensing CIO 

Mineral and energy resource potential CIO

Epithermal precious-metal and energy mineral resource potential CIO

Oil and gas resource potential CIO

Geothermal resource potential CIO 

References cited Cll 

Appendixes

Definition of levels of mineral resource potential and certainty of assessment C14 

Resource/reserve classification CIS 

Geologic time chart C16

FIGURES

1. Index map showing the location of the Abert Rim Wilderness Study Area, Lake 

County, Oregon C2

2. Map showing mineral resource potential and generalized geology of the Abert Rim 

Wilderness Study Area, Lake County, Oregon C4

3. Aeromagnetic map of the Abert Rim Wilderness Study Area and surrounding area C9

Contents

Mineral Resources of the

Abert Rim Wilderness Study Area,

Lake County, Oregon

By Maureen G. Sherlock, Mark E. Gettings, and Harley D. King 

U.S. Geological Survey

Terry R. Neumann 

U.S. Bureau of Mines

SUMMARY 

Abstract

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

the 23,760-acre Abert Rim Wilderness Study Area 

(OR-001-101) was evaluated for identified mineral resources 

(known) and mineral resource potential (undiscovered). In 

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

study area" or simply "the study area." Fieldwork was conducted in late summer, 1986. No mineral resources were 

identified. A field reconnaissance of the study area revealed 

no areas of alteration that might be associated with mineralization. Results of geochemical analysis do not suggest 

mineralization. Rocks associated with gold, silver, mercury, 

and uranium mineralization are located in the surrounding 

region but do not crop out within the study area. Geophysical analysis suggests that these rock types may be located at 

shallow depths under parts of the Abert Rim Wilderness Study 

Area. Therefore, the northern and central parts of the study 

area have low potential for gold, silver, mercury, and uranium resources in epithermal deposits. The entire study area 

has moderate potential for geothermal energy resources and 

low potential for oil and gas resources. Basalt in the study 

area is suitable for local industrial use but does not currently 

constitute a resource.

Character and Setting

The Abert Rim Wilderness Study Area is located about 

20 mi north of Lakeview, Oregon (fig. 1). It is a long 

north-south tract located along the east margin of Lake

Manuscript approved for publication. August 9, 1988.

Abert. A total of 23,760 acres was evaluated for the study. 

Abert Rim is a 2,000-ft-high fault escarpment, popularly 

but erroneously termed the highest fault scarp in North 

America. Along the west margin of the study area, at Abert 

Rim, the terrain consists of steep talus-covered slopes below a near-vertical 400-ft-high cliff. East of Abert Rim, the 

study area forms a gently eastward-sloping plateau. Elevations in the study area rise from 4,255 ft at the shores of 

Lake Abert to 4,800 to 7,000 ft along the plateau rim. 

Access to the study area is provided by U.S. Highway 395 

and by jeep trails from Oregon Highway 140 leading to the 

plateau along the north and south ends of the study area. 

Abert Rim is a cliff and plateau composed predominantly of middle Tertiary basalt and andesite flows and 

minor lenses of interbedded tuffs and tuffaceous sedimentary rocks, which are capped by younger Tertiary basalt 

(fig. 2) (see appendixes for geologic time chart). Quaternary (Holocene) alluvium and playa deposits lie along the 

shores of Lake Abert and in small patches along the base 

of the Abert Rim escarpment. Adjacent to the wilderness 

study area, but not exposed within it, are Tertiary and 

Quaternary rhyolitic to dacitic plugs, dikes, domes, and 

intrusive breccias, which are associated with uranium, 

mercury, and gold mineralization in nearby mining districts.

Identified Mineral Resources

No metallic or nonmetallic resources were identified 

within the study area. Resources of gold, silver, mercury, 

diatomite, and bentonite were postulated in a 1985 U.S.

Mineral Resources of the Abert Rim Wilderness Study Area, Lake County, Oregon C1
Bureau of Land Management study of the area. Our study 

suggests that these resources do not exist within the study 

area. Two samples taken from tuffaceous rock units in the 

Rabbit Creek area contain anomalous zeolite concentrations.

U.S. Bureau of Land Management and Lake County 

records did not show any claim or lease activity in the 

study area. Field examinations did not reveal evidence of 

mines or claims within the study area.

Mineral Resource Potential

The Abert Rim Wilderness Study Area does not lie 

within any established mining district, nor does it contain 

mines, prospects, or occurrences of metallic or nonmetallic 

commodities. The study area, however, does lie within a 

region where Tertiary rhyolitic domes are associated with 

gold, silver, mercury, and uranium epithermal deposits. 

Furthermore, aeromagnetic studies suggest the possibility

121°00 120° 00'

APPROXIMATE BOUNDARY

OF

ABERT RIM

WILDERNESS STUDY AREA 

(OR-001-101)

HARNEY COUNTY /

LAKE COUNTY /

FREMONT

NATIONAL

FOREST

A 6740 

- .. COYOTE HILLS

QUARTZ BUTTE 

A 6279

Figure 1. Index map showing location of the Abert Rim Wilderness Study Area, Lake County, Oregon.

C2 Mineral Resources of Wilderness Study Areas: South-Central Oregon
of an intrusive body buried under the volcanic cover. 

Therefore, the northern and central parts of the Abert Rim 

Wilderness Study Area have a low potential for gold, silver, mercury, and uranium resources in epithermal deposits. 

The entire study area has moderate potential for geothermal 

energy resources and low potential for oil and gas resources. Industrial-grade rock, sand, and gravel are present 

in the wilderness study area, but their development is unlikely because of remoteness from markets.

INTRODUCTION

This mineral survey was requested by the U.S. Bureau 

of Land Management and is the result of a cooperative 

effort by the U.S. Geological Survey and the U.S. Bureau 

of Mines. An introduction to the wilderness review process, mineral survey methods, and agency responsibilities 

was provided by Beikman and others (1983). The U.S. 

Bureau of Mines evaluates identified resources at individual mines and known mineralized areas by collecting data 

on current and past mining activities and through field 

examination of mines, prospects, claims, and mineralized 

areas. Identified resources are classified according to the 

system that is a modification of that described by McKelvey (1972) and the U.S. Bureau of Mines and U.S. 

Geological Survey (1980). U.S. Geological Survey studies 

are designed to provide a reasonable scientific basis for 

assessing the potential for undiscovered mineral resources 

by determining geologic units and structures, possible 

environments of mineral deposition, presence of geochemical and geophysical anomalies, and applicable ore-deposit 

models. Goudarzi (1984) discussed mineral assessment 

methodology and terminology as they apply to these surveys. See appendixes for the definition of levels of mineral 

resource potential and certainty of assessment and for the 

resource/reserve classification.

Location and Physiography

The Abert Rim Wilderness Study Area comprises 

23,760 acres in the Basin and Range physiographic province and is situated in the central part of Lake County, 

Oregon, about 20 mi north of Lakeview. Abert Rim is the 

west margin of the Warner Mountains and is a steep, 

slightly eroded fault scarp of recent origin; movement 

along the fault may have begun in the Pliocene and continued intermittently into the Holocene (Baldwin, 1964). The 

terrain within the study area is dominated by a gently sloping plateau, the tilted fault block of the Warner Mountains, 

that is bounded on the west by the 2000-ft fault escarpment 

at Abert Rim. Elevations rise from 4,255 ft at the shores 

of Lake Abert to about 4,800 to 7,000 ft (north to south) 

along the crest of Abert Rim. The highest elevation within 

the study area, approximately 7,040 ft, is a low hill on the

plateau near the south boundary. The west boundary follows the east edge of U.S. Highway 395 along the east 

shore of Lake Abert. The other boundaries are a powerline 

road and U.S. Bureau of Land Management roads.

The region containing the study area is semiarid and 

contains several lakes, including Lake Abert, that occupy 

topographically closed basins between fault-scarp ridges 

(Phillips and Van Denburgh, 1971). Precipitation averages 

12 in. per year at Valley Falls, near the southwest corner of 

the study area. Vegetation is predominantly sagebrush, but 

one remnant stand of Ponderosa pine grows at Colvin 

Timbers, which is the northernmost timber in the Warner 

Mountains. Upland game birds and game mammals, including Big Horn Sheep, as well as raptorial birds, wild 

horses, and other species inhabit the area (U.S. Bureau of 

Land Management, 1985; 1987).

Procedures and Sources of Data

The U.S. Geological Survey conducted detailed field 

investigations of the Abert Rim Wilderness Study Area in 

the late summer of 1986. This work included field checking existing geologic maps, geochemical sampling, and examining outcrops for evidence of mineralization. The geologic map of the wilderness study area is taken from 

Walker (1963; 1977).

During the summer of 1986, the U.S. Bureau of Mines 

conducted field examinations of the study area. All available information on geology, mining, and mineral resources 

in the area, including U.S. Bureau of Land Management 

and Lake County mining claim records, was reviewed prior 

to fieldwork. Field studies consisted of a search for mineralized zones within the study area. Mineralized zones 

near the study area were investigated to determine if they 

extended into the wilderness study area and to better understand mineralization in the region. Scintillometers were 

used during all ground traverses.

Twenty-eight samples were collected during the U.S. 

Bureau of Mines' study (Neumann, 1987). Most were 

rock-chip samples of tuffaceous interbeds and of brecciated 

basalt and rhyolite (from outcrops outside the wilderness 

study area) at or near fault contacts. A description of 

sample types is given by Neumann (1987). Thirteen rock 

samples were analyzed by an inductively coupled plasma 

method for the following elements: silver, arsenic, gold, 

copper, mercury, molybdenum, lead, antimony, titanium, 

zinc, bismuth, cadmium, gallium, palladium, platinum, 

selenium, tin, and tellurium. Twelve samples were assayed 

for arsenic, gold, and silver. Detection levels for gold and 

silver were in the parts per billion (ppb) range, whereas the 

other elements were detected at parts per million (ppm) 

limits. Additionally, all tuffaceous samples were tested at 

the U.S. Bureau of Mines Western Field Operations Center 

for zeolite content using an ion-exchange capability method

Mineral Resources of the Abert Rim Wilderness Study Area, Lake County, Oregon C3
120°20' 120° 10'

'APPROXIMATE BOUNDARY 

OF

ABERT RIM

WILDERNESS STUDY AREA

(OR-001-101)

EXPLANATION

Area having moderate resource potential 

(M) for geothermal resources

Area having low mineral resource potential 

(L) for gold, silver, mercury, and uranium in epithermal deposits

Levels of certainty of assessment

Data only suggest level of potential 

Data give good indication of level of potential

Commodities

Gold

Silver

Mercury

Uranium

Geothermal

Oil and gas

Geologic map units

Surficial deposits (Holocene)

Pediment gravel (Quaternary and Tertiary)

Pyroclastic cinder mounds (Quaternary and 

Tertiary)

Olivine basalt (Pliocene)

Tuff (Pliocene) Semiconsolidated tuff includes lacustrine tuffaceous sandstone 

and siltstone, ash, diatomite, ash-flow 

tuff, lapilli tuff, and tuff breccia

Basalt of Abert Rim (late Miocene)

Tuff and tuffaceous sedimentary rocks 

(middle Miocene)

Porphyritic basalt and andesite flows of 

Abert Rim (middle Miocene)

Mafic vent rocks (Miocene)

Silicic vent rocks (Miocene(?) and Oligocene)

 Contact Dashed where approximate

 Fault Dashed where approximate or inferred; dotted where concealed; ball and 

bar on downthrown side

Figure 2. Mineral resource potential and generalized geology of the Abert Rim Wilderness Study Area, Lake County, Oregon. 

Geology from Walker (1963; 1977).

C4 Mineral Resources of Wilderness Study Areas: South-Central Oregon
(Helfferich, 1964); three samples contained zeolite and 

were further analyzed by X-ray diffraction. Further information and complete analytical results are available from 

the Bureau of Mines, Western Field Operations Center, 360 

E. Third Avenue, Spokane, WA 99202.

Other resource-related studies of the area include statewide studies of the mineral resources (Fern and Huber, 

1984), the geothermal resources (Oregon Department of 

Geology and Mineral Industries and National Oceanic and 

Atmospheric Administration, 1982), and the oil and gas 

potential of wilderness lands (Fouch, 1983). Erikson and 

Curry (1977) described the uranium favorability of Tertiary 

rocks in southeastern Oregon. In 1983, the study area was 

part of the U.S. Bureau of Land Management geology, 

energy, and minerals (GEM) inventory program (Mathcws 

and others, 1983).

Acknowledgments

M.I. Hornberger and J.A. Ach, geologists, U.S. Geological Survey, Menlo Park, Calif., assisted with the field 

checking of geologic maps and with rock geochemistry 

sampling. C.D. Taylor assisted in the stream-sediment 

geochemical sampling. D.A. Benjamin and S.L. Willett, 

geologists, Western Field Operations Center, Spokane, 

Wash., assisted the U.S. Bureau of Mines author with 

prefield work and field examination. The authors gratefully acknowledge the cooperation provided by personnel 

of the U.S. Bureau of Land Management, Lakeview, Oreg.

APPRAISAL OF IDENTIFIED RESOURCES

By Terry R. Neumann 

U.S. Bureau of Mines

Mining and Mineral Exploration History

Although there has been no mining-related activity 

within the Abert Rim Wilderness Study Area, gold and 

mercury have been mined in the Coyote Hills area, 8 mi to 

the east. In 1906, gold was discovered in the Coyote Hills, 

prompting a small prospecting and claim-staking rush and 

the establishment of the Lost Cabin mining district, also 

known as the Coyote Hills, Camp Loftus, and Windy Hill 

districts. Absence of production records suggests interest 

in the gold occurrences was short-lived. Prospecting in the 

district was revived when cinnabar (mercury sulfide) was 

discovered in 1934. Mercury mines in the area were in 

production during 1941-1943; conflicting reports indicate 

that between three and seven flasks of mercury (76 pounds 

per flask) were produced from ore with a tenor (grade) of 

0.15-0.95 percent (Thomas, 1981, p. 104). There was no 

mining activity in the district from the mid-1940's until 

1978. In 1978, numerous mining companies began exploration in the area targeting large tonnage, low-grade epithermal precious-metal deposits (David Troutman, U.S. Bureau of Land Management staff, oral commun., 1986). 

Ongoing drilling programs are being conducted to continue 

exploration of the area.

Rocks in the Lost Cabin district include andesitic to 

rhyolitic flows, tuffs, breccias, and a hypabyssal quartz 

monzonite intrusive body representing a complex volcanic 

center. Most mineralized rock in the district consists of 

stockwork veinlets and disseminated ore minerals in argillically altered silicic volcanic rocks (Thomas, 1981).

Similar mineralized zones are associated with brecciated rhyolite at the Hannah prospect 2 mi north of the study 

area (fig. 1). The Hannah prospect comprises six claims 

that are owned and operated by John Cremin and Donald 

Fitzgerald of Lakeview, Orcg. The claims appear to be a 

relocation of earlier claims owned by the Frontier Mining 

Company. The prospect has no record of production. No 

extensions of the Coyote Hills or Hannah prospect host 

rocks crop out in the wilderness study area.

Mines, Prospects, Mining Claims, and Leases

U.S. Bureau of Land Management and historical mining records indicate that no mining claims, geothermal 

leases, or oil and gas leases were present within the wilderness study area as of January 1, 1987. A field investigation 

failed to identify any evidence of exploration or mining 

activities.

Two geothermal leases, probably for the water rights 

of Juniper and Poison Creeks, lie just outside the west 

boundary of the wilderness study area. Additionally, a 

highway borrow pit is adjacent to the northwest edge of the 

wilderness study area along U.S. Highway 395.

Appraisal of Identified Resources

The Abert Rim Wilderness Study Area contains no 

identified mineral resources. Samples contain no anomalous amounts of precious or base metals. Preliminary testing for zeolites from the Rabbit Creek area suggested 

zeolite concentrations, but further testing by X-ray diffraction demonstrated that the zeolite content is too low to 

quantify.

ASSESSMENT OF MINERAL RESOURCE 

POTENTIAL

By Maurccn C. Sherlock, Mark E. Ceilings, and

Harley D. King

U.S. Geological Survey

Geology

The geology of the Abert Rim Wilderness Study Area 

is included on regional maps by Walker (1963; 1977) and

Mineral Resources of the Abert Rim Wilderness Study Area, Lake County, Oregon C5
is shown in figure 2. The oldest unit in the study area is 

middle Miocene in age and comprises basaltic and andesitic 

flows; these flows form the majority of the slopes of the 

Abert Rim scarp and most of the cliff below the late 

Miocene basalt that caps the rim. Middle Miocene tuffaceous rocks are interbedded with the basaltic and andesitic flows and occur underneath the capping basalt The 

younger map units include late Miocene, Pliocene, Pleistocene, and Holocene pyroclastic cinder mounds, gravel, 

alluvium, and playa sedimentary rock units. Mafic and 

silicic vent rocks are the oldest units in the area mapped, 

but they do not crop out within the study area. The silicic 

vent rocks are associated with mineralization in the general 

region.

Tertiary Volcanic Rocks

The middle Miocene basaltic and andesitic flows are 

distinctively plagioclase rich and porphyritic; they contain 

large white plagioclase laths in a dark, reddish-brown to 

black, vesicular matrix. Red scoriaceous basalt rubble 

marks the tops of some flows. Locally, at the base of the 

cliff, the vesicles follow planar horizontal cooling and 

shear planes. Minor sparsely porphyritic flows, which 

show flow alignment of plagioclase laths, crop out among 

the coarsely porphyritic plagioclase-rich basalts. The 

coarsely and sparsely porphyritic flows are both composed 

of calcic plagioclase, orthopyroxene, and partially to completely altered olivine phenocrysts in a dark matrix containing small plagioclase laths and many iron oxides. Vesicles 

are typically filled with radiating zeolite or calcite. These 

distinctive flows have been correlated with the Steens 

Basalt by Walker (1980) and are approximately 15 Ma in 

age (million years before present). McKee and others 

(1983) reported a potassium-argon age of 15.1±0.8 Ma 

from a basalt apparently just below the capping basalt in 

the southern part of the study area. Hart and Mertzman 

(1982) report a potassium-argon age of 14.62±0.72 Ma 

from an extremely porphyritic basalt in the central part of 

the study area. Exact stratigraphic location of neither 

sample is known.

Interbedded tuffs and tuffaceous sedimentary rocks of 

middle Miocene age form a persistent, thin unit below the 

capping basalt along the cliff rim in the southern part of the 

study area. The same unit crops out in large patches on the 

plateau top and along Rabbit Creek and Mule Lake near the 

east boundary of the study area. These tuffs and tuffaceous 

sedimentary rocks are rhyolitic and dacitic in composition 

and contain fresh glass shards, pumice lapilli, and locally 

abundant mammalian fossils. The fossils correlate with the 

middle Miocene fauna of the Mascall Formation of central 

Oregon. Small lenses of interbedded tuffs and tuffaceous 

sedimentary rocks crop out at a few localities in the northern part of the study area. These lenses that are exposed on

cliff faces are typically 5 to 15 ft in thickness and a few 

tens of feet in length; they are white and pink and thinly 

bedded. These tuffaceous rocks consist of crystal fragments of feldspar, pyroxene and biotite, lithic fragments of 

scoriaceous basalt, and altered glass shards and pumice. 

The interbedded tuff unit is widespread to the west and 

south of the study area; at a few localities, adjacent to 

range-front faults, the unit is brecciated and altered to 

clays, calcite, gypsum, and other white alkaline precipitates 

(Brown and others, 1980). Similar brecciation and alteration are not found within the study area.

Basalt of Abert Rim of late Miocene age is a regionally 

widespread unit that crops out poorly, frequently only as 

loose rubble, on sage-covered plateau tops. These basalts 

are dark gray, platy jointed, and flat lying. This capping 

unit includes both vesicular and nonvesicular flows that are 

characteristically fine grained and contain sparse small 

plagioclase and olivine phenocrysts. Ophitic texture is well 

developed. The rocks contain clinopyroxene, calcic plagioclase, sparse olivine crystals only slightly altered to iddingsite, and iron titanium oxide minerals throughout the 

groundmass. Hart and Mertzman (1982) reported one 

potassium-argon age of 6.07±0.66 Ma from a sample of 

basalt from the northern part of the wilderness study area.

The tuff unit of Pliocene age crops out only in a very 

small area in the northern part of the wilderness study area. 

It is widespread in the general region and consists of lacustrine tuffaceous sandstone and siltstone, ash and ashy diatomite, ash-flow tuff, lapilli tuff, and tuff breccia. Some tuffs 

within the unit are partly or densely welded. The tuffs 

exposed in and near the study area are a distal part of a 

welded tuff (G.W. Walker, oral commun., 1988).

The olivine basalt unit of Pliocene age shown on figure 

2 is not exposed in the study area.

Tertiary and Quaternary Volcanic and Surficial Deposits

Pyroclastic cinder mounds of Tertiary and Quaternary 

age were mapped by Walker (1963) in the study area. 

These mounds are highly modified by erosion. They have 

slopes of cindery red soil that contain sparse lava bombs 

and bomb fragments.

An unconsolidated unit of poorly sorted gravels and 

bouldery soil forms pediments above pluvial lake levels 

(fig. 2). This unit contains clasts composed mostly of 

basalt and andesite and is locally cemented by caliche. 

These pediment gravels are not within the study area.

Quaternary surficial deposits, composed of Holoceneage poorly sorted gravel, sand, and silt in stream-channel 

and flood-plain deposits, are part of an alluvial plain at the 

north end of the study area and the outlet channel at the 

south end. Sparse patches of rounded coarse gravel and 

cobbles were deposited along the shore of Lake Abert. 

Remnants of gravels from higher lake levels formed along

C6 Mineral Resources of Wilderness Study Areas: South-Central Oregon
strandlines of beaches a few tens of feet above the present 

lake level. The most distinct of these, 14.7 ft above the 

present lake level, probably formed about A.D. 1805 

(Phillips and Van Denburgh, 1971). Other higher and less 

distinct strandlines probably formed over the last few thousand years. Playa deposits composed of clay, silt, sand, and 

local evaporites are present at the north end of Lake Abert, 

outside the study area boundary.

Regional Mineralization

Tertiary volcanic rocks of a bimodal basalt and rhyolite association are common in southeastern Oregon. 

These volcanic rocks are both intrusive and extrusive and 

are interpreted as mafic and silicic vent complexes and 

shield volcanoes. Some of these rocks form plugs, dikes, 

small endogenous domes, and intrusive breccias and are associated with gold, silver, uranium, and mercury mineralization in southeastern Oregon (Brooks, 1963; Brooks and 

Ramp, 1968). These rocks do not crop out within the Abert 

Rim Wilderness Study Area but are exposed near the north, 

south, and east boundaries (fig. 2).

The mafic vent rocks consist of a heterogeneous mixture of basaltic and andesitic extrusive rocks; these rocks 

include agglomerates, breccias, flows, and tuffs, and intrusive rocks forming constructional volcanic features, mostly 

lava cones and small shield volcanoes (Walker, 1977). 

North of the study area, a road cut along U.S. Highway 395 

shows the heterogeneous nature of these mafic vent and 

flow rocks. Associated silicic vent rocks consist of intrusive rhyolites and dacites, rare soda rhyolite, and a few 

large masses of perlite that form small plugs, dikes, endogenous domes, and intrusive breccias. Three small silicic plugs that intrude the mafic vent rocks east of the 

highway have been prospected, presumably for gold and 

(or) mercury (Hannah prospect, fig. 1). Similar mafic and 

silicic rocks, apparently slightly older, which cover a much 

larger area, are exposed in the Coyote Hills 10 mi southeast. Two small silicic bodies, partly composed of a 

breccia containing subrounded to subangular volcanic 

clasts, are exposed 0.5 mi south of the study area.

Gold and mercury prospects of the Lost Cabin district 

in the Coyote Hills area are contained in intrusive silicic 

rocks, dated at about 26.5 to 28.5 Ma (Walker, 1981; 

Fiebelkorn and others, 1983), that are older than the Abert 

Rim basalt flows. Mineralization in the Lost Cabin district 

is associated with zones of shearing and brecciation in flatlying agglomerates, flows intruded by small dacitic plugs, 

and opalized tuffs. Fine-grained pyrite and cinnabar are 

disseminated through brecciated rocks, and cinnabar occurs 

as films along fractures (Brooks, 1963); gold and copper 

oxide minerals are deposited in altered seams of clay, 

limonite, and quartz, which fill small irregular fractures 

(Brooks and Ramp, 1968).

The Quartz Mountain volcanic-hosted hot-spring gold 

deposit is about 32 mi southwest of the study area (fig. 1). 

At Quartz Mountain, rhyolitic domes and intrusive rocks 

similar to those near Abert Rim crop out as a series of 

domes aligned along northwest-trending faults (M.G. 

Sawlan, written commun., 1987). These domes have been 

dated at about 7 Ma (Walker, 1981; McKee and others, 

1983). Prior to the recognition and development of the 

large-tonnage, low-grade disseminated gold deposit, Quartz 

Mountain produced minor amounts of mercury from altered 

rhyolitic volcanic rocks (Brooks, 1963).

Uranium mineralization is associated with rhyolitic 

domes and intrusive rocks of southeastern Oregon. The 

Lakeview uranium area, about 24 mi southwest of Abert 

Rim, produced about 145,000 tons of uranium ore having 

an average grade of 0.17 percent. The Lakeview uranium 

deposits are spatially related to areas of extensive silicification and clay alteration in rhyolitic intrusive rocks and in 

altered tuffs and tuffaceous sedimentary wall rocks along 

north west-trending fault zones (Walker, 1980).

Structure

Basin-and-range normal faulting is the dominant structural feature of the area. A major north-northeast-trending 

normal fault is mapped along Abert Rim for the length of 

the study area. Parallel subsidiary faults and northwesttrending faults create the topography we see today. The 

Abert Rim fault offset the Tertiary-age volcanic flows as 

much as 2,000 ft in the southern part of the study area; the 

northwest-trending faults may have offset sections of the 

volcanic sequence as much as 500 ft. In the northern part 

of the study area, the stratigraphic section normally found 

higher on the slopes is apparently repeated as a result of 

movement along northwest-trending faults.

The northwest-trending faults are spatially related to 

the ore deposits of the region; the hot-springs gold deposits 

at Quartz Mountain and the volcanogenic uranium deposits 

of the Lakeview uranium area are localized along northwest-trending faults.

Geochemistry

Methods

In the summer of 1986, the U.S. Geological Survey 

collected 27 samples of rock, 23 samples of minus-80-mesh 

stream sediments, and 22 samples of nonmagnetic heavymineral concentrate derived from stream sediments from 46 

sites in the Abert Rim Wilderness Study Area. Rock 

samples, which are representative of the lithologies present 

in the wilderness study area, were collected to determine 

geochemical background values. Hydrothermally altered or 

mineralized rocks were not observed in the study area 

during the reconnaissance survey. Two rock samples from

Mineral Resources of the Abert Rim Wilderness Study Area, Lake County, Oregon C7
Tertiary silicic vent units outside the wilderness study area 

were collected for comparison.

All samples were analyzed for 31 elements using a sixstep semiquantitative emission spectrographic method described by Grimes and Marranzino (1968). The rock and 

stream-sediment samples were analyzed for antimony, arsenic, bismuth, cadmium, and zinc by inductively coupled 

argon plasma-atomic emission spectroscopy and for gold 

and mercury by atomic absorption (methods described in 

Crock and others, 1987). M.S. Erickson (U.S. Geological 

Survey, unpub. data, 1988) provided tables of analytical 

data, descriptions of sampling, preparation, and analytical 

methods, and a map showing sample-collection sites.

Results and Interpretations

The geochemical analysis did not reveal significant 

anomalous concentrations of elements that suggest mineralization. A sediment sample collected at a site just downstream from a spring near the southern end of the study 

area contained slightly anomalous values of arsenic (37 

ppm) and zinc (300 ppm). The concentrate sample from 

the same site contained a slightly anomalous value of 

copper (300 ppm). Stream-bed sediments at the site are 

coated with limonite, suggesting that the enrichment of 

elements is probably due to coprecipitation and adsorption 

of the elements with the limonite. The anomaly probably 

does not represent mineralization. A sample of tuff from 

near the northern end of the study area contains slightly 

anomalous values of silver (0.5 ppm) and lead (50 ppm). 

The values may reflect enrichment along a fault in that 

area.

Geophysics 

Aeromagnetic Data

An acromagnetic survey including the Abert Rim Wilderness Study Area was flown and compiled in 1972 under 

contract to the U.S. Geological Survey (U.S. Geological 

Survey, 1972). Total-field magnetic data were collected in 

analog form along east-west flightlines spaced at approximately 2-mi intervals. The lines were flown at a constant 

barometric altitude of 9,000 ft. Corrections were applied to 

the data to compensate for diurnal variations of the Earth's 

magnetic field. A regional magnetic field of 8 nanoTeslas 

(nT)/mi in the direction N. 30° E. was subtracted from the 

data to produce a residual magnetic anomaly data set. 

Using the corrected digitized analog data, an aeromagnctic 

map of the wilderness study area (fig. 3) was prepared at a 

contour interval of 50 nT for comparison with geologic and 

topographic maps. The topographic expression of Abert 

Rim seems to cause about a 50-nT perturbation in the 

aeromagnetic anomaly contours, particularly in the northem half of the study area (fig. 3).

The southern half of the study area lies on the west 

edge of a positive aeromagnetic anomaly of about 700 nT 

amplitude (fig. 3). Horizontal extents of the steepest gradients of this anomaly suggest a burial depth of 1,000 to 

1,600 ft to the top of the magnetic anomaly source. The 

anomaly lies over a northwest-trending fault zone generally 

forming an uplifted fault block (Walker, 1963). The anomaly is interpreted to be due to an intrusive mass. The silicic 

volcanic rocks of the Coyote Hills to the east of the study 

area may be associated with the intrusion. Elsewhere in the 

area, intrusive domes and vents of silicic composition are 

spatially associated with positive magnetic anomalies, and 

the intrusions are generally located beneath the anomaly 

flanks or apophyses (fig. 3). These intrusive rocks are 

frequently emplaced along existing faults and are sometimes associated with mineralization. Thus the area within 

the north flank of the anomaly may have silicic intrusive 

rocks beneath it at depths of 1,600 ft or less. Anomalies 

having steep gradients are seldom associated with the silicic intrusive rocks (fig. 3), and thus the west side of the 

anomaly gradient does not suggest the presence of buried 

silicic intrusives.

The north end of the Abert Rim Wilderness Study Area 

is within a smaller positive acromagnetic anomaly (fig. 3), 

which has silicic intrusive rocks associated with it, north of 

the study area. The flank of this anomaly that is within the 

study area may have buried silicic intrusive rocks beneath 

it.

Magnetic anomaly relative minima characterize the 

areas to the west and south of the study area (fig. 3). These 

minima are probably due to an increase in depth to the 

magnetic basement that results from alluvial and sedimentary fill in fault-bounded depressions. East of the wilderness study area, trends of anomaly gradients in the aeromagnetic field correlate mainly with fault zones. The large 

magnetic-field relative minimum east of the northern half 

of the wilderness study area (fig. 3) suggests an area of 

local thickening of tuffaceous rocks underlying basalt flows 

on the surface (Walker, 1963).

Airborne radiomelric and magnetic data of the Klamath Falls quadrangle are also available from the National 

Uranium Resource Evaluation (Geo-Life, 1980). Eight 

east-west flightlines, spaced 3 mi apart and flown at a 

terrain clearance of approximately 400 ft, crossed the wilderness study area during that study. These radiometric 

measurements sampled X-ray flux, which indicates concentrations of uranium, thorium, and potassium in the rocks. 

The radiomelric profiles did not show any significant 

gamma-ray emission anomalies.

Gravity Data

Gravity survey data for the Abert Rim Wilderness 

Study Area are sparse, and only seven stations are in or 

near the wilderness study area (Defense Mapping Agency

C8 Mineral Resources of Wilderness Study Areas: South-Central Oregon
120° 30' 

1

120° 15' 120° 00'

42C 

45'

42° 

30'

PPROXIMATE BOUNDARY

ABERT\RIM

WlttDERNESS STUDY AR 

OR-OOIVIOI)

I A

5 MILES 

J

Aeromagnetic contour Contour interval 50 

nanoTesla. Datum is arbitrary

Intrusive and extrusive rocks of dacitic and 

rhyolitic composition

EXPLANATION

L Relative magnetic low

H Relative magnetic high 

I::::::: :| Area possibly underlain by silicic intrusive rocks

Figure 3. Aeromagnetic map of Abert Rim Wilderness Study Area and surrounding region.

Mineral Resources of the Abert Rim Wilderness Study Area, Lake County, Oregon C9
Aerospace Center, 1983). Of the seven stations, six are 

along U.S. Highway 395 on the west boundary of the study 

area. The remaining station is just outside the east boundary near the headwaters of Rabbit Creek. The Bouguer 

gravity anomaly field of the wilderness study area is a 

gentle northeast-trending gradient in which anomaly values 

increase to the northwest. Bouguer gravity anomaly values 

range from approximately -150 milliGal (mGal) in the 

northern part of the wilderness study area to about -165 

mGal in the south. The data suggest that a gravity anomaly 

is associated with the large aeromagnetic anomaly in the 

southern half of the area. However, the data are so sparse 

that the existence of such an anomaly and even the trend of 

the regional field would require verification by obtaining 

further gravity data within and around the study area.

Remote Sensing

Landsat multispectral scanner (MSS) images at a scale 

of 1:800,000 were examined for southeastern Oregon. In 

the general region of the Abert Rim Wilderness Study 

Area, linear features are not well expressed owing to the 

nature of the surface cover (D.L. Sawatzky, written commun., 1987).

Mineral and Energy Resource Potential

There are no known metallic or nonmetallic deposits in 

the Abert Rim Wilderness Study Area. Southeastern Oregon has long been known to contain small deposits of gold, 

mercury, and uranium. Recently, a large-tonnage, lowgrade gold deposit was discovered 32 mi southwest of the 

wilderness study area, but similar host rocks are not exposed within the study area. However, aeromagnetic studies suggest the possiblity that such rock types (i.e., silicic 

intrusive rocks) may exist at depth, possibly 1,000 to 1,600 

ft beneath the surface. Two thermal springs are located 

within the study area (fig. 1). The study area does not 

contain rocks that would be suitable host or reservoir rocks 

for oil and gas. Industrial-grade rock, sand, and gravel are 

present in the wilderness study area, but development of 

these materials is unlikely because similar materials of 

equal or better quality are abundant closer to existing 

markets.

Epithermal Precious-metal and 

Energy Mineral Resource Potential

Known epithermal gold, silver, mercury, and uranium 

mineralization near the study area is of the hot-spring gold, 

silver (Berger, 1986), hot-spring mercury (Rytuba, 1986), 

and volcanogenic uranium (Bagby, 1986) deposit model 

types described in Cox and Singer (1986). In southeastern 

Oregon, significant economic concentrations of gold and

uranium are known to occur in 7-Ma rhyolitic domes and 

intrusive rocks emplaced along northwest-trending faults in 

a near-surface environment. The surficial geology of the 

Abert Rim Wilderness Study Area and the results of geochemical rock and stream-sediment sampling do not suggest gold, silver, mercury, or uranium mineralization. 

However, the results of the aeromagnetic studies suggest a 

buried intrusive body at 1,000 to 1,600 ft that, by analogy 

with exposed intrusive bodies, is assumed to be rhyolitic in 

composition. These geophysically anomalous areas, in the 

northern and central parts of the wilderness study area, are 

assigned a low potential, with a certainty level of B, for 

gold, silver, mercury, and uranium resources (fig. 2). The 

lithology, age, and mineralization of the apparent intrusive 

rocks are unknown and could be determined only by sampling between 1,000 ft and 1,600 ft.

Oil and Gas Resource Potential

Fouch (1983) qualitatively assessed the High Plateau 

province of eastern Oregon as having a range of potential 

for oil and gas from zero to medium. He assigned a low 

potential for oil and gas to the Abert Rim Wilderness Study 

Area. He based this assessment on the presence of 

Neogene basalt, which is locally intercalated with nonmarine sedimentary rocks. In local basins formed during 

Neogene time, these nonmarine sedimentary rocks can 

include abundant coal beds and thus be a possible reservoir 

for gas. The interbedded tuffs and tuffaceous sedimentary 

rocks intercalated within the Miocene basalts of the Abert 

Rim Wilderness Study Area are both too thin and lacking 

in coal beds to be considered a potential reservoir for gas. 

The Abert Rim Wilderness Study Area has a low potential 

for oil and gas resources with a certainty level of C.

Geothermal Resource Potential

Two thermal springs are located within the Abert Rim 

Wilderness Study Area (approximate locations on fig. 1). 

Temperatures of the springs are warm and flow is moderate 

(Oregon Department of Geology and Mineral Industries 

and National Oceanic and Atomospheric Administration, 

1982). Three other, imprecisely located, thermal springs 

(which may or may not correspond to the two above) are 

listed in the compendium by Waring (1965, as revised by 

Blankenship and Bentall). The springs are in Pliocene lake 

beds near faulted Tertiary lava; are used as water supply for 

cattle; and have temperatures of 65, 68, and 80 °F and 

flows of 20, 10, and 30 gallons per minute, respectively. 

Any of these springs may correspond to the two geothermal 

leases, apparently for water rights, known to exist along the 

west boundary of the wilderness study area. Based on the 

available data, the potential for geothermal energy resources within the Abert Rim Wilderness Study Area is 

moderate, certainty level C.

C10 Mineral Resources of Wilderness Study Areas: South-Central Oregon
REFERENCES CITED

Bagby, W.C., 1986, Descriptive model of volcanogenic uranium, 

in Cox, D.P., and Singer, D.A., eds., Mineral deposit models: 

U.S. Geological Survey Bulletin 1693, p. 162.

Baldwin, E.M., 1964, Geology of Oregon: Dubuque, Iowa, 

Kendall/Hunt Publishing Company, 3rd. Ed., 1981, 170 p.

Beikman, H.M., Hinkle, M.E., Frieders, Twila, Marcus, S.M., and 

Edward, J.R., 1983, Mineral surveys by the Geological Survey and the Bureau of Mines of Bureau of Land Management 

Wilderness Study Areas: U.S. Geological Survey Circular 

901, 28 p.

Berger, B.R., 1986, Descriptive model of hot-spring Au-Ag, in 

Cox, D.P., and Singer, D.A., eds., Mineral deposit models: 

U.S. Geological Survey Bulletin 1693, p. 143-144.

Brooks, H.C., 1963, Quicksilver deposits of Oregon: Oregon 

Department of Geology and Mineral Industries Bulletin 55, 

223 p.

Brooks, H.C., and Ramp, Len, 1968, Gold and silver in Oregon: 

Oregon Department of Geology and Mineral Industries Bulletin 61, 337 p.

Brown, D.E., Peterson, N.V., and McLean, G.D., 1980, Preliminary geology and geothermal resource potential of the 

Lakeview area, Oregon: Oregon Department of Geology and 

Mineral Industries Open-file Report 0-80-9, 108 p.

Cox, D.P., and Singer, D.A., eds., 1986, Mineral deposit models: 

U.S. Geological Survey Bulletin 1693, 379 p.

Crock, J.G., Briggs, P.H., Jackson, L.L., and Lichte, F.E., 1987, 

Analytical methods for the analysis of stream sediments and 

rocks from wilderness study areas: U.S. Geological Survey 

Open-File Report 87-84, 35 p.

Defense Mapping Agency Aerospace Center, 1983, World relative gravity reference network, North America, 2 computer 

tapes.

Erikson, F.H., and Curry, W.E., 1977, Preliminary study of the 

uranium favorability of Tertiary rocks, southeastern Oregon: 

eastern Klamath, southern Lake, Hamey, and western 

Malheur Counties: U.S. Department of Energy, 

6JBX-92(77), 24 p.

Fern, Mark, and Huber, Don, 1984, Mineral resources map of 

Oregon: Oregon Department of Geology and Mineral Industries map, scale 1:500,000.

Fiebelkorn, R.B., Walker, G.W., MacLeod, N.S., McKee, E.H., 

and Smith, J.G., 1983, Index to K-Ar determinations for the 

State of Oregon: Isochron/west, no. 37, 60 p.

Fouch, T.D., 1983, Petroleum potential of wilderness lands, Oregon: U.S. Geological Survey Miscellaneous Investigations 

Series Map 1-1544, scale 1:1,000,000.

Geo-Life (A joint venture between High Life Helicopters, Inc. 

and Geodata International Inc.), 1980, Aerial radiometric and 

magnetic survey, Klamath Falls, National Topographic Map, 

California, Oregon: [Available from U.S. Department of 

Energy, Grand Junction, Colo. Office] GJBX 20-80.

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

reports on public lands: U.S. Geological Survey Open-File 

Report 84-787, 51 p.

Grimes, D.J., and Marranzino, A.P., 1968, Direct-current arc and 

alternating-current spark emission spectrographic field methods for the semiquantitative analysis of geologic materials:

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

Hart, W.K., and Mertzman, S.A., 1982, K-Ar ages of basalts from 

south-central and southeastern Oregon: Isochron/west, no. 33, 

p. 23-26.

Helfferich, Friedrich, 1964, A simple identification reaction for 

zeolites (molecular sieves): American Mineralogist, v. 49, p. 

1,752-1,754.

Lawrence, R.D., 1976, Strike-slip faulting terminates the Basin 

and Range province in Oregon: Geological Society of 

America Bulletin, v. 87, p. 846-850.

Mathews, G.W., Blackburn, W.H., and Chappel, D.L., 1983, 

Assessment of Geology, Energy, and Minerals (GEM) Resources: Abert Rim GRA (OR-010-26) Lake County, Oregon: Prepared for U.S. Bureau of Land Management, by 

Terradata, Lakewood, Colo., BLM Contract No. 

YA-553-CT2-1042.

McKee, E.H., Duffield, W.A., and Stern, R.J., 1983, Late Miocene and early Pliocene basaltic rocks and their implications 

for crustal structure, northeastern California and south-central 

Oregon: Geological Society of America Bulletin, v. 94, p. 

292-304.

McKelvey, V.E., 1972, Mineral resource estimates and public 

policy: American Scientist, v. 60, p. 32-40.

Neumann, T.R., 1987, Mineral resources of the Abert Rim Wilderness Study Area, Lake County, Oregon: U.S. Bureau of 

Mines Open-File Report MLA 54-87, 13 p.

Oregon Department of Geology and Mineral Industries and National Oceanic and Atmospheric Administration, 1982, Geothermal resources of Oregon: Oregon Department of Geology 

and Mineral Industries, scale 1:500,000.

Phillips, K.N., and Van Denburgh, A.S., 1971, Hydrology and 

geochemistry of Abert, Summer, and Goose Lakes, and other 

closed-basin lakes in south-central Oregon: U.S. Geological 

Survey Professional Paper 502-B, 86 p.

Rytuba, J.J., 1986, Descriptive model of hot-spring Hg, in Cox, 

D.P., and Singer, D.A., eds., Mineral deposit models: U.S. 

Geological Survey Bulletin 1693, p. 178.

Thomas, T.H., 1981, Geology and mineral deposits of the Coyote 

Hills mining district, Lake County, Oregon: Corvallis, Oreg., 

Oregon State University, M.S. thesis, 132 p.

U.S. Bureau of Land Management, 1985, Oregon Wilderness 

Environmental Impact Statement, v. 2, draft, p. 95-105.

 1987, Oregon Wilderness Environmental Impact Statement, v. 2, supp. to draft, p. 33-38.

U.S. Bureau of Mines and U.S. Geological Survey, 1980, Principles of a resource/reserve classification for minerals: U.S. 

Geological Survey Circular 831, 5 p.

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

Falls and part of the Crescent 1° by 2° quadrangles, Oregon: 

U.S. Geological Survey Open-File Report 72-392, scale 

1:250,000.

Walker, G.W., 1963, Reconnaissance geologic map of the eastern 

half of the Klamath Falls (AMS) quadrangle, Lake and Klamath Counties, Oregon: U.S. Geological Survey Mineral 

Investigations Field Studies Map MF-260, scale 1:250,0000.

 1977, Geologic map of Oregon east of the 121st meridian: 

U.S. Geological Survey Miscellaneous Investigations Series 

Map 1-902, scale 1:500,000.

 1980, Preliminary report on the geology of the Lakeview

Mineral Resources of the Abert Rim Wilderness Study Area, Lake County, Oregon C11
uranium area, Lake County, Oregon: U.S. Geological Survey 81-1920, 45 p.

Open-File Report 80-532, 33 p. Waring, G.A., 1965, Thermal springs of the United States and 

 1981, Uranium, thorium, and other metal associations in other countries of the world a summary, rev. by Reginald R. 

silicic volcanic complexes of the northern basin and range, a Blankenship and Ray Bentall: U.S. Geological Survey Propreliminary report: U.S. Geological Survey Open-File Report fessional Paper 492, 383 p.

C12 Mineral Resources of Wilderness Study Areas: South-Central Oregon
APPENDIXES
DEFINITION OF LEVELS OF MINERAL RESOURCE POTENTIAL 

AND CERTAINTY OF ASSESSMENT

LEVELS OF RESOURCE POTENTIAL

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

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

indicating presence of resources, and where evidence indicates that mineral concentration has taken place. 

Assignment of high resource potential to an area requires some positive knowledge that mineral-forming processes 

have been active in at least part of the area.

M 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 reasonable likelihood for resource accumulation, and (or) where an application of mineral-deposit models 

indicates favorable ground for the specified type(s) of deposits.

L LOW mineral resource potential is assigned to areas where geologic, geochemical, and geophysical characteristics 

define a geologic environment in which the existence of resources is permissive. This broad category embraces 

areas with dispersed but insignificantly mineralized rock, as well as areas with little or no indication of having 

been mineralized.

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

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

moderate, or high level of resource potential.

LEVELS OF CERTAINTY

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

B Available information only suggests the level of mineral resource potential.

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

D Available information clearly defines the level of mineral resource potential.

hZ

LLJ

o

Q_

LLJ 

U

C£

D

Oco

LLJ

o

_J

LLJ 

>

A

U/A

UNKNOWN POTENTIAL

B

H/B

HIGH POTENTIAL

M/B

MODERATE POTENTIAL

L/B

LOW POTENTIAL

C

H/C

HIGH POTENTIAL

M/C

MODERATE POTENTIAL

L/C

LOW POTENTIAL

D

H/D

HIGH POTENTIAL

M/D

MODERATE POTENTIAL

L/D

LOW POTENTIAL

N/D

NO POTENTIAL

LEVEL OF CERTAINTY

Abstracted with minor modifications from:

Taylor, R.B., and Steven, T.A., 1983, Definition of mineral resource potential: Economic Geology, v. 78, no. 6, p. 1268-1270.

Taylor, R.B., Stoneman, R.J., and Marsh, S.P., 1984, An assessment of the mineral resource potential of the San Isabel National Forest, south-central Colorado: U.S.

Geological Survey Bulletin 1638, p. 40-42. 

Goudarzi, G.H., compiler, 1984, Guide to preparation of mineral survey reports on public lands: U.S. Geological Survey Open-File Report 84-0787, p. 7, 8.

C14 Mineral Resources of Wilderness Study Areas: South-Central Oregon
RESOURCE/RESERVE CLASSIFICATION

ECONOMIC

MARGINALLY 

ECONOMIC

SUBECONOMIC

IDENTIFIED RESOURCES

Demonstrated

Measured

Rese

Indicated

;rves

Marginal 

Reserves

i 

Demonstrated

Subeconomic 

Resources

Inferred

Inferred 

Reserves

Inferred 

Marginal 

Reserves

Inferred 

Subeconomic 

Resources

UNDISCOVERED RESOURCES

Probability Range

Hypothetical Speculative

1

1

I

i

Major elements of mineral resource classification, excluding reserve base and inferred reserve base. Modified from McKelvey, V.E., 1972, Mineral 

resource estimates and public policy: American Scientist, v. 60, p. 32-40; and U.S. Bureau of Mines and U.S. Geological Survey, 1980, Principles 

of a resource/reserve classification for minerals: U.S. Geological Survey Circular 831, p. 5.

Mineral Resources of the Abert Rim Wilderness Study Area, Lake County, Oregon C15
GEOLOGIC TIME CHART

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

EON

Phanerozoic

Proterozoic

Archean

ERA

Cenozoic

Mesozoic

Paleozoic

Late Proterozoic

Middle Proterozoic

Early Proterozoic

Late Archean

Middle Archean

Early Archean

PERIOD

Quaternary

Tertiary

Neogene 

Subperiod

Paleogene 

Subperiod

Cretaceous

Jurassic

Triassic

Permian

Carboniferous 

Periods

Pennsyivanian

Mississippian

Devonian

Silurian

Ordovician

Cambrian

pre-Archean2

fitiflrft}

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 

MILLION YEARS (Ma)

0.010

1.7

5

24

ia

55

 66

96

1 la

205

-240

 290 

-330

 360 

 410

~ J/ U

J\J\J

 1600

jwwv/

 3400

 /iccr» 

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

informal time term without specific rank.

C16 Mineral Resources of Wilderness Study Areas: South-Central Oregon

GPO 585-045/9762


SELECTED SERIES OF U.S. GEOLOGICAL SURVEY PUBLICATIONS

Periodicals

Earthquakes & Volcanoes (issued bimonthly). 

Preliminary Determination of Epicenters (issued monthly).

Technical Books and Reports

Professional Papers are mainly comprehensive scientific reports of 

wide and lasting interest and importance to professional scientists and engineers. Included are reports on the results of resource studies and of 

topographic, hydrologic, and geologic investigations. They also include 

collections of related papers addressing different aspects of a single scientific topic.

Bulletins contain significant data and interpretations that are of lasting scientific interest but are generally more limited in scope or 

geographic coverage than Professional Papers. They include the results 

of resource studies and of geologic and topographic investigations; as well 

as collections of short papers related to a specific topic.

Water-Supply Papers are comprehensive reports that present significant interpretive results of hydrologic investigations of wide interest 

to professional geologists, hydrologists, and engineers. The series covers 

investigations in all phases of hydrology, including hydrogeology, 

availability of water, quality of water, and use of water.

Circulars present administrative information or important scientific 

information of wide popular interest in a format designed for distribution 

at no cost to the public. Information is usually of short-term interest.

Water-Resources Investigations Reports are papers of an interpretive nature made available to the public outside the formal USGS publications series. Copies are reproduced on request unlike formal USGS 

publications, and they are also available for public inspection at 

depositories indicated in USGS catalogs.

Open-File Reports include unpublished manuscript reports, maps, 

and other material that are made available for public consultation at 

depositories. They are a nonpermanent form of publication that may be 

cited in other publications as sources of information.

Maps

Geologic Quadrangle Maps are multicolor geologic maps on 

topographic bases in 71/2- or 15-minute quadrangle formats (scales mainly 1:24,000 or 1:62,500) showing bedrock, surficial, or engineering geology. Maps generally include brief texts; some maps include structure 

and columnar sections only.

Geophysical Investigations Maps are on topographic or planimetric 

bases at various scales; they show results of surveys using geophysical 

techniques, such as gravity, magnetic, seismic, or radioactivity, which 

reflect subsurface structures that are of economic or geologic significance. 

Many maps include correlations with the geology.

Miscellaneous Investigations Series Maps are on planimetric or 

topographic bases of regular and irregular areas at various scales; they 

present a wide variety of format and subject matter. The series also includes 71/2-minute quadrangle photogeologic maps on planimetric bases 

which show geology as interpreted from aerial photographs. Series also 

includes maps of Mars and the Moon.

Coal Investigations Maps are geologic maps on topographic or 

planimetric bases at various scales showing bedrock or surficial geology, stratigraphy, and structural relations in certain coal-resource areas.

Oil and Gas Investigations Charts show stratigraphic information 

for certain oil and gas fields and other areas having petroleum potential.

Miscellaneous Field Studies Maps are multicolor or black-andwhite maps on topographic or planimetric bases on quadrangle or irregular areas at various scales. Pre-1971 maps show bedrock geology 

in relation to specific mining or mineral-deposit problems; post-1971 

maps are primarily black-and-white maps on various subjects such as 

environmental studies or wilderness mineral investigations.

Hydrologic Investigations Atlases are multicolored or black-andwhite maps on topographic or planimetric bases presenting a wide range 

of geohydro logic data of both regular and irregular areas; principal scale 

is 1:24,000 and regional studies are at 1:250,000 scale or smaller.

Catalogs

Permanent catalogs, as well as some others, giving comprehensive listings of U.S. Geological Survey publications are available under 

the conditions indicated below from the U.S. Geological Survey, Books 

and Open-File Reports Section, Federal Center, Box 25425, Denver, 

CO 80225. (See latest Price and Availability List)

"Publications of the Geological Survey, 1879-1961" may be purchased by mail and over the counter in paperback book form and as a 

set of microfiche.

"Publications of the Geological Survey, 1962-1970" may be purchased by mail and over the counter in paperback book form and as a 

set of microfiche.

"Publications of the U.S. Geological Survey, 1971-1981" may be 

purchased by mail and over the counter in paperback book form (two 

volumes, publications listing and index) and as a set of microfiche.

Supplements for 1982,1983,1984,1985,1986, and for subsequent 

years since the last permanent catalog may be purchased by mail and 

over the counter in paperback book form.

State catalogs, "List of U.S. Geological Survey Geologic and 

Water-Supply Reports and Maps For (State)," may be purchased by mail 

and over the counter in paperback booklet form only.

"Price and Availability List of U.S. Geological Survey Publications," issued annually, is available free of charge in paperback booklet form only.

Selected copies of a monthly catalog "New Publications of the U.S. 

Geological Survey" available free of charge by mail or may be obtained 

over the counter in paperback booklet form only. Those wishing a free 

subscription to the monthly catalog "New Publications of the U.S. 

Geological Survey" should write to the U.S. Geological Survey, 582 

National Center, Reston, VA 22092.

Note.-Prices of Government publications listed in older catalogs, 

announcements, and publications may be incorrect. Therefore, the 

prices charged may differ from the prices in catalogs, announcements, 

and publications.