Mineral Resources of the

South Warner Contiguous Wilderness

Study Area, Modoc County, California

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Chapter F

Mineral Resources of the

South Warner Contiguous Wilderness

Study Area, Modoc County, California

By MICHAEL G. SAWLAN and JAMES G. FRISKEN 

U.S. Geological Survey

MICHAEL S. MILLER 

U.S. Bureau of Mines

U.S. GEOLOGICAL SURVEY BULLETIN 1706

MINERAL RESOURCES OF WILDERNESS STUDY AREAS:

NORTHEASTERN CALIFORNIA AND PART OF ADJACENT WASHOE COUNTY, NEVADA
DEPARTMENT OF THE INTERIOR 

MANUEL LUJAN, JR., Secretary

U.S. GEOLOGICAL SURVEY 

Dallas L. Peck, Director

Any use of trade, product, or firm names

in this publication is for descriptive purposes only

and does not imply endorsement by the U.S. Government

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1989

For sale by the

Books and Open-File Reports Section

U.S. Geological Survey

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Library of Congress Cataloging-in-Publication Data

Sawlan, Michael G.

Mineral resources of the South Wamer Contiguous Wilderness Study Area, 

Modoc County, California / by Michael G. Sawlan and James G. Frisken, 

Michael S. Miller

p. cm. (Mineral resources of wilderness study areas 

northeastern California and part of adjacent Washoe County, Nevada ; ch. 

F)(U.S. Geological Survey bulletin ; 1706-F)

Bibliography: p.

Supt. of Docs. no. : I 19.3:1706-F

1. Mines and mineral resources California South Wamer Contiguous 

Wilderness. 2. South Wamer Contiguous Wilderness (Calif.) I. Frisken, James 

G. II. Miller, Michael S. III. Title. IV. Series. V. Series: U.S. Geological 

Survey bulletin ; 1706-F.

QE75.B9 no. 1706-F 557.3 s dc20 88-600133 

UN24.C2] [553'.09794'23] CIP
STUDIES RELATED TO WILDERNESS

Bureau of Land Management Wilderness Study Areas

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

1976) requires the U.S. Geological Survey and the U.S. Bureau of Mines to conduct mineral surveys on certain areas to determine the mineral values, if any, that may be present. 

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

Congress. This report presents the results of a mineral survey of the South Warner 

Contiguous Wilderness Study Area (CA-02Q-708), Modoc County, California.

CONTENTS

Summary Fl 

Abstract Fl 

Character and setting Fl 

Identified resources F3 

Mineral resource potential F3 

Introduction F3

Location and physiography F3 

Access F3 

Previous investigations F3 

Present investigations F5 

Acknowledgments F5 

Appraisal of identified resources F5 

Mining and exploration history F5 

Prospects, claims, and mineral occurrences F6 

Gold F6

Nonmetallic commodities F6 

Perlite F6 

Pozzolan F6 

Sand and gravel F7 

Zeolites F7 

Energy resources F7

Geothermal energy resources F7 

Oil and gas F10 

Coal F10

Assessment of mineral resource potential F10 

Geology F10

Description of stratigraphic units F10

Andesitic volcaniclastic and sedimentary rocks Fll 

Composite volcanic rocks Fll 

Basalt flows Fll 

Tephra Fll 

Mafic lava flows Fll 

Rhyolite Fll 

Surficial deposits Fll 

Intrusive rocks F12 

Structure F12

Alteration and mineralization F12 

Geochemical studies F14

Methods and background F14 

Results and interpretations F14 

Geophysical studies F15 

Mineral and energy resource potential F16 

Mineral resources F16 

Geothermal energy resources F16 

Oil and gas F16 

References cited FIT 

Appendixes

Definition of levels of mineral resource potential and certainty of assessment F20 

Resource/reserve classification F21 

Geologic time chart F22

Contents
FIGURES

1. Index map showing location of South Warner Contiguous Wilderness Study Area, Modoc 

County, California F2

2. Map showing generalized geology and mineral resource potential of the South Warner 

Contiguous Wilderness Study Area, Modoc County, California F4

TABLE

1. Mines, prospects, claims, and mineralized areas in and near the South Warner Contiguous 

Wilderness Study Area, Modoc County, Calif. F8

VI Contents
Mineral Resources of the South Warner 

Contiguous Wilderness Study Area, 

Modoc County, California

By Michael G. Sawlan and James G. Frisken 

U.S. Geological Survey

Michael S. Miller 

U.S. Bureau of Mines

SUMMARY 

Abstract

The South Warner Contiguous Wilderness Study Area 

(CA-020-708) is located along the east flank of the South 

Warner Mountains in northeastern California. At the request 

of the U.S. Bureau of Land Management, 4,330 acres of the 

South Warner Contiguous Wilderness Study Area was evaluated for mineral resources; (known) and mineral resource 

potential (undiscovered). In this report, the area studied is 

referred to as the "South Warner Contiguous Wilderness 

Study Area" or the "study area."

Approximately 35 mining claims have been located in or 

near the study area but no claims are current; there are no 

mineral leases. The study area contains identified resources 

of geothermal energy, and sand and gravel. The Barber 

parcel contains a small, marginally economic, geothermal 

resource suitable for space heating. Sand and gravel, similar 

to that found in the study area within the Eagle and Barber 

parcels, are currently excavated from small pits located east 

of the study area. Uneconomic occurrences of gold, perlite, 

pozzolan, zeolites, carbonaceous rock, and hydrocarbons are 

also present. The Granger, Cottonwood, Hornback, Eagle, 

Barber, and Van Riper parcels contain low-grade, uneconomic gold occurrences in rock. Traces of alluvial gold are 

also found in the Granger and Eagle parcels.

The entire study area has low potential for epithermal 

(low-temperature) gold and silver resources. Evidence of 

epithermal mineralization consists of rock and stream-sediment geochemical anomalies of gold or elements associated 

with gold in present-day mineralized hot springs and related 

epithermal gold deposits, and alteration characterized by 

silicification. The Barber and Van Riper parcels in the southern part of the study area have low potential for geothermal 

energy resources. The entire study area has no potential for 

oil and gas.

Manuscript approved for publication, March 28, 1989.

Character and Setting

The South Warner Contiguous Wilderness Study Area 

(CA-020-708) is located along the east flank of the South 

Warner Mountains in Modoc County, Calif., on land 

administered by the U.S. Bureau of Land Management (fig. 

1). The study area comprises nine individual parcels distributed along 18 miles (mi) of the east boundary of the 

South Warner Wilderness, which lies within the Modoc 

National Forest. These parcels are located 3 to 21 mi south 

of Cedarville, Calif. From north to south the names of 

these parcels are the Granger, Milk, Cottonwood, Owl, 

Hornback, Eagle, Emerson, Barber and Van Riper parcels. 

All parcels are located on the rugged, steep, east slope of 

the Warner Mountains along the west side of the Surprise 

Valley fault zone. Elevations of the parcels range from 

about 4,600 to 6,700 ft (feet).

The study area is underlain by Oligocene (see appendixes for geologic time chart) to middle Miocene volcanic 

rocks which form a gently west-dipping (20°-25°) homocline west of the Surprise Valley fault zone (fig. 2). 

These volcanic rocks include andesitic volcaniclastic 

breccia, volcanic conglomerate and sandstone, basalt, andesite, and rhyolite lava, rhyolite ignimbrite, and andesite 

dikes. Volcanic conglomerate and volcaniclastic breccia 

are most abundant in the northernmost parcels. Rhyolite 

lava and ignimbrite occurs in the southern parcels, from the 

Eagle parcel south to the Barber parcel. These volcanic 

rocks are cut by two major fault sets. Tertiary volcanic 

strata are displaced by northeast- trending faults that were 

active during post-middle Miocene time prior to inception 

of faulting along the Surprise Valley fault zone. The northtrending Surprise Valley fault zone has been active in 

Quaternary time and truncates the northeast-trending fault 

set Quaternary deltaic gravel deposits occur along the 

Surprise Valley fault zone.

Mineral Resources of the South Warner Contiguous Wilderness Study Area, California F1
120° 15' 120°00'

41°30' -

EXPLANATION

Contiguous Wilderness Study Area 

(CA-020-708)

Granger parcel I

Cottonwood parcel 

Owlparce

Hornback parcel SOUTH WARNER 

WILDERNESS

.

\" « <""*

Emerson parcel

Lower Lake

Van Riper parcel

West Valley Reservoir

Sworinger 

C \ Reservoir

MODOC COUNTY 

LASSEN COUNTY

01234 MILES

Figure 1. Index map showing location of South Warner Contiguous Wilderness Study Area, Modoc County, Calif.

F2 Mineral Resources of Wilderness Study Areas: Northeastern California and Washoe County, Nevada
Identified Resources

The South Warner Contiguous Wilderness Study Area 

contains a small, low-temperature, marginally economic 

geothermal resource in and near the Barber parcel. Identified sand and gravel resources are located in and adjacent 

to the Eagle and Barber parcels. Gravels are currently 

excavated from small pits located east of the study area. 

County mining records show that more than 35 mining 

claims have been located in or near the study area. However, none of these claims is current and there are no 

mineral leases. No mineral exploration is presently occurring in or adjacent to the study area.

Mineral Resource Potential

The study area has low potential for gold and silver 

resources in epithermal veins. Gold mineralization and 

related alteration and (or) geochemical anomalies are found 

in all parcels in the study area (fig. 2). Mineralization and 

alteration are strongly fracture-controlled and do not extend 

significantly into the wall rock outside of planar silicified 

zones. Mineralized areas are typically narrow (2- to 10-ftwide), subvertical, planar to broadly lensoidal, silicified 

zones along north- and northeast-trending faults and (or) 

fractures. Locally these zones contain sulfides, limonite, 

and veins of barite and calcite.

Rocks containing anomalous gold concentrations are 

commonly silicified. The higher gold anomalies typically 

occur in rocks containing visible sulfide and (or) strong 

limonitic staining and boxwork after sulfide. Mineralized 

rocks contain anomalous concentrations of gold, mercury, 

antimony, arsenic, molybdenum, silver, cadmium, copper, 

boron, barium, and lead. All samples collected from the 

study area contain only low concentrations of gold.

The Barber and Van Riper parcels have low potential 

for geothermal energy resources. Warm springs are located 

in or adjacent to these two parcels. Although these warm 

springs are considered insufficient for geothermal energy 

development, they may be suitable for local space heating 

applications. The study area lies southwest of the Lake 

City Known Geothermal Resource Area (KGRA). No 

geothermal energy development has occurred in this 

KGRA, although 11 exploratory wells have been drilled. 

The entire study area has no potential for oil and gas.

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 modified from that described by McKelvey (1972) 

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

(1980). Studies by the U.S. Geological Survey 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 South Warner Contiguous Wilderness Study Area 

(CA-020-708) is located in Modoc County, Calif., and 

contains nine parcels located 3 to 21 miles south of Cedarville, Calif, (fig. 1). From north to south, the nine 

parcels are named the Granger, Milk, Cottonwood, Owl, 

Hornback, Eagle, Emerson, Barber, and Van Riper parcels. 

These parcels encompass 4,330 acres on the lower east 

flanks of the Warner Mountains. The study area, administered by the U.S. Bureau of Land Management, lies along 

the east boundary of the South Warner Wilderness, which 

is part of the Modoc National Forest.

The east flank of the Warner Mountains forms a steep, 

rugged terrain dissected by deep, narrow canyons. Much of 

the study area is exposed bedrock that is locally covered by 

slope wash, grasses, or juniper. Foot travel in the study 

area is treacherous due to loose surficial gravel on mostly 

barren rock as well as numerous cliffs and box canyons. 

Vegetation in the study area is sparse except along the 

wider creeks, which are lined by poplars.

Access

All parcels of the study area lie within 1.5 mi of 

Surprise Valley Road, a paved, county-maintained road that 

runs north-south along the west side of Surprise Valley (fig. 

1). Graded gravel roads provide additional access to the 

Granger, Emerson, and Barber parcels, and several jeep 

trails traverse the Barber parcel. Other parcels are accessed 

by jeep trails across private ranch lands.

Previous Investigations

Russell (1928) described the physiography, regional 

geology, and stratigraphy of the Warner Range. More

Mineral Resources of the South Warner Contiguous Wilderness Study Area, California F3
120° 10' 120°05'

41 "251

41°20'

L / C goldsilver

CH

EXPLANATION

Area having low mineral resource 

potential (L) for commodities indicated 

(gold, silver, and/or gcothermal)

Level of certainly of assessment 

Data give good indication of level of potential

South Warner Contiguous Wilderness Study Area 

(CA-020-708) - Approximate boundary

CORRELATION OF MAP UNITS

I per parcel

Tvm Tvb 

L / C gold, silver

Alluvium (Holoccnc and Pleistocene)

Gravel (Holocene and Pleistocene)

Rhyolilc (Miocene)

Mafic lava flows (Miocene)

Tephra (Miocene)

Rasalt flows (Miocene)

Composite volcanic rocks (Miocene and Oligoccnc)

Andcsitic volcaniclaslic and sedimentary rocks (Oligoccnc)

Contact

Fault - Dashed where uncertain or concealed

Ball and bar on downthrown side 

Lode Mine

Sand and Gravel Pit _ 

Prospect 

Letter identifying prospects, mines and mincrali/cd

Barber parcel

2 MILES 

J

Figure 2. Mineral resource potential and generalized geology of the South Warner Contiguous Wilderness Study Area, Modoc 

County, Calif. Geology modified from Duffield and Weldin (1976) and Hedel (1980, 1981).

F4 Mineral Resources of Wilderness Study Areas: Northeastern California and Washoe County, Nevada
recently, Duffield and Weldin (1976) mapped the geology 

and evaluated the mineral resources of the South Warner 

Wilderness located adjacent to and west of the study area 

parcels. Duffield and McKee (1986) presented potassiumargon (K-Ar) ages and described the structure of volcanic 

rocks of the Warner Range. Hedel (1980, 1981) described 

and mapped in detail the structure of the Surprise Valley 

fault zone and the Quaternary geology of Surprise Valley. 

Gedthermal resources of the Warner Mountains-Surprise 

Valley area have been described and evaluated by Duffield 

and Foumier (1974), and Hedel (1981). Tunnel (1972) has 

discussed the geochemistry and mineralogy of the Menlo 

Hot Springs located about 4 mi south of Eagleville, adjacent to and east of the Barber parcel. A gamma-ray and 

magnetometer survey of the Alturas 2° sheet (Aero Service 

Division, 1981) included the study area.

Present Investigations

In 1986 and 1987 the U.S. Geological Survey (USGS) 

conducted field investigations in the study area, which 

consisted of checking, refining, and augmenting earlier 

geologic mapping, searching for altered or mineralized 

areas, and collecting geochemical samples. In all, 174 

outcrop rock samples, 25 stream-sediment samples, 24 

heavy-mineral-concentrate samples panned from stream 

sediment, and 10 cobble and float-rock samples collected at 

stream-sediment sample sites were analyzed to reveal areas 

having anomalous concentrations of elements of interest. 

All analyses were performed at U.S. Geological Survey 

laboratories.

Work by the U.S. Bureau of Mines (USBM) included 

perusal of available literature on the geology, mines, and 

prospects in the vicinity of the study area. Federal, state, 

and county records were examined to ascertain the location 

of mines or mineral claims in the study area. Field studies, 

conducted in 1987, included the examination, mapping, and 

geochemical sampling of prospects, claims, and mineralized areas in and adjacent to the study area; 31 alluvial and 

134 rock samples were collected. The alluvial samples 

were concentrated and examined for economic minerals. 

Mineralized rock samples were analyzed for a suite of 

elements related to formation of mineral deposits. Samples 

from nonmetallic sources with likely industrial uses were 

analyzed with respect to their pertinent physical properties. 

Sampling procedures and results of the USBM investigations of the study area are described by Miller (1988). 

Sample data are available at the Western Field Operations 

Center, E. 360 Third Ave., Spokane, WA 99202.

Acknowledgments

Terry J. Close, William N. Hale and John R. Benham 

(U.S. Bureau of Mines, Western Field Operations Center, 

Spokane, WA), and Joseph McFarlan (U.S. Bureau of Land

Management, Cedarville, CA) assisted M.S. Miller in the 

field. Logistic support from the U.S. Bureau of Land 

Management and the U.S. Forest Service is gratefully 

acknowledged.

APPRAISAL OF IDENTIFIED RESOURCES

By Michael S. Miller 

U.S. Bureau of Mines

Mining and Exploration History

There is no record of mineral production within the 

South Warner Contiguous Wilderness Study Area. Approximately 35 mining claims have been located in or near 

the study area, but none of these are currently active. 

These claims were nearly all staked in the late 1800's and 

early 1900's. At least six of these claims were oil and gas 

placers, and at least one was a coal placer claim1 . Mines, 

prospects, mineralized areas, and industrial mineral occurrences located in or near the study area are shown in figure 

2 and described in table 1. Sample localities and analytical 

results are presented in Miller (1988).

The nearest mine with recorded production is the 

Bagley mine (fig. 2, area G). About 1,000 oz of Iceland 

spar (optical-grade calcite) was mined at the Bagley mine 

in 1920-1921; an unrecorded amount was mined during the 

early 1940's, and 1,000 Ib of calcite was mined during the 

late 1940's (Gay, 1966; Duffield and Weldin, 1976). The 

calcite deposit at the Bagley mine does not extend into the 

study area.

Total sand and gravel production from borrow pits 

along the highway between Cedarville and Eagleville (fig. 

2) is unknown, but 4,000-10,000 yd3 (cubic yards) per year 

was the estimated production rate in 1987 (Dale Goodwin, 

Goodwin Sand and Gravel, Cedarville, Calif., oral commun., 1987).

Other nearby mining or prospecting has been from 

mercury, obsidian, pumice, perlite, peat, and some salt 

deposits (Duffield and Weldin, 1976; Gay, 1966). Placers 

were mined along Eagle Creek (fig. 2, area J) in the late 

1800's and early 1900's. An estimated 40,000 yd3 of 

gravel was excavated, presumably for gold; it is not known 

how much, if any, gold was recovered. An unnamed, 

abandoned mercury prospect, located about 2 mi north of 

the Granger parcel between North Deep Creek and South 

Deep Creek, is marked by several shallow pits and the 

rusted remains of a retort. It was probably worked in the 

1950's during a period of federal price supports for mercury.

'The oil and gas placer claims were not for alluvial materials; prior 

to the Mineral Leasing Act of 1920, certain mineral commodities such as 

gas and coal were claimed as placer locations.

Mineral Resources of the South Warner Contiguous Wilderness Study Area, California F5
In Surprise Valley, geothermal energy resources located 5 to 35 mi east and north of the study area are gradually being developed for space heating and aquaculture 

(Joseph McFarlan, BLM, Cedarville, Calif., oral commun., 

1987). Hot springs adjacent to the study area at Menlo 

Baths are currently used sporadically for bathing. Warm 

springs, with temperatures of 64°-65° F, (fig. 2, area Q) 

flow within and near the study area, north of Barber Creek, 

but are not currently utilized.

Several widely scattered, volcanic-hosted epithermal 

gold mines and prospects occur in the region surrounding 

the study area. These include the Hayden Hill, Winters, 

and High Grade mines and districts in northeastern California, which produced about $3.5 million in gold and silver 

in the late 1800's and early 1900's (Duffield and Weldin, 

1976), and the Hog Ranch mine in Nevada, which has 

recently been developed. These mines are located 30-50 

mi from the study area. Only the Hayden Hill and Hog 

Ranch properties are currently operating. Within the past 

several years, exploration companies have been reevaluating the High Grade district, located 35 mi north of Cedarville, which has remained inactive since the turn of the 

century following selective mining of high-grade zones.

Prospects, Claims and Mineral Occurrences

The study area contains a small, low-temperature, 

identified geothermal resource in and near the Barber parcel and identified sand and gravel resources located mainly 

in or near the Barber and Eagle parcels. Metallic mineral 

occurrences in the study area are related to uneconomic 

occurrences of gold. Nonmetallic commodities include 

uneconomic occurrences of perlite, pozzolan, and zeolites. 

Low-quality, noncommercial perlite and pozzolan occurrences are located in the Emerson and Barber parcels. 

Zeolites exist in all parcels in small veins; the largest 

occurrence of zeolite is in amygdules in basalt lava in the 

Emerson, Barber and Van Riper parcels. None of the 

occurrences of zeolite are suitable for commercial development and use. Trace amounts of hydrocarbon are found in 

sparse occurrences of weakly carbonaceous volcaniclastic 

rocks.

parcel (fig. 2, area A) contain small amounts of gold, as 

much as 170 ppb. A sample of silicified rock from the 

northeast corner of the Granger parcel (fig. 2 area B) 

contains calcite veins having 9 ppb gold. Some samples of 

volcanic rock from sites in or near the Cottonwood, Eagle, 

Barber, and Van Riper parcels contain as much as 6 ppb 

gold. All areas are too weakly mineralized, by factors of 

at least ten, to be economic.

Alluvium in and near the study area contains a trace of 

free gold: a single microscopic flake of gold estimated to 

weigh less than 0.005 mg was found in each of two 0.3 ft3 

(cubic feet) alluvial samples (fig. 2, areas A and J) from the 

Granger and Eagle parcels. Alluvium at these two sites is 

estimated to contain less than 0.00002 troy oz of gold per 

yd3, worth about 1 cent per yd3 at a gold price of $450 per 

troy oz (ounce). The alluvium has no economic value as a 

gold placer.

Nonmetallic Commodities

Perlite

Perlite occurs in small outcrops (10-100 ft across) of 

rhyolite in the Barber parcel. Perlite is hydrous obsidian 

that can be heated to near-molten temperatures and expanded into a lightweight, glassy foam. Expanded perlite 

is commonly used in the manufacture of insulation and low 

density construction materials. Two perlite occurrences 

(fig. 2, area Q) are each estimated to be about 100 ft long, 

25 ft wide, and 25 ft thick. Using a weight factor of 150 

lb/ft3 (pounds per cubic feet), 10,000 tons of perlite may 

exist in the study area.

Perlite from the Barber parcel has substandard expansion and brightness properties. Expanded density of the 

perlite is 10.44 lb/ft3, marginal when compared to the 

expanded density of standards, about 3 lb/ft3. Brightness is 

also low, about 51.6 percent, compared to brightness of 

67.1 to 69.4 percent for the standards. Furthermore, the 

size of the occurrence is too small to be economic. Perlite 

from the Barber parcel is therefore unsuitable for use as 

commercial perlite and the perlite localities are classified as 

uneconomic occurrences.

Gold

Gold occurrences in samples collected by the U.S. 

Bureau of Mines from silicified zones and altered volcanic 

rocks within the Granger, Cottonwood, Eagle, Barber, and 

Van Riper parcels were determined to be uneconomic. 

Samples were analyzed for gold by a commercial laboratory using an instrumental neutron-activation method having a detection limit of 5 ppb (parts per billion). Five of 

eight rock samples adjacent ID and north of the Granger

Pozzolan

Light-colored, rhyolitic, welded and unwelded tuffs in 

the southern part of the study area (fig. 2, area O) have the 

general chemical characteristics of pozzolans (American 

Society for Testing and Materials, 1985), natural materials 

that can be used as extenders or modifiers with portland or 

other mineral cements. Most rhyolitic tuff in the study area 

is located in the Barber parcel and can be traced over an 

area of about 2 mi2 (square miles) extending northwest into 

the Emerson parcel. Tuff in the Barber parcel is unsuitable

F6 Mineral Resources of Wilderness Study Areas: Northeastern California and Washoe County, Nevada
for pozzolan because it is mostly strongly indurated welded 

tuff having a hardness equivalent to lava; the hardness of 

this rock would present difficulties in mining and processing. In addition, tuff in the study area has no special 

physical or chemical properties compared to tuff that covers vast tracts of land throughout the Great Basin in Nevada 

and Oregon.

Sand and Gravel

Identified sand and gravel resources of the study area 

are located in deltaic gravel deposits along the east boundaries of the parcels. Most gravel deposits are located outside 

the study area; only a small fraction of these deposits is 

included inside the study area. For example, a terrace near 

the mouth of Eagle Creek (fig. 2, area K) includes an estimated 36 million yd3 of sand and gravel, of which only 

2.5 million yd3 lie inside the Eagle parcel. Near the mouth 

of Emerson Creek (fig. 2, area M), deltaic gravel deposits 

encompass an inferred 31 million yd3 of sand and gravel, of 

which only 6 million yd3 lie inside the Barber parcel. More 

than 100 million yd3 of terrace sand and gravel are estimated to exist adjacent to the Granger and Milk parcels, but 

less than 1 million yd3 may exist inside the study area at 

scattered sites. Small occurrences of sand and gravel (less 

than 10,000 yd3) also occur in the narrow, steep drainages 

of the study area, but these materials are poorly sorted and 

inferior in quality to the deltaic gravels.

The terrace sand and gravel are cleaner (have a lower 

silt and clay content) than alluvium in Surprise Valley. 

This terrace sand and gravel contains less than about 5 

percent silt or clay, although washing, sizing, and removal 

of some undesirable material may be necessary (Dale 

Goodwin, Goodwin Sand and Gravel, Cedarville, Calif., 

and Gene Cooper, Whitepine Ranch, Eagleville, Calif., oral 

commun., 1987).

Deltaic terrace sand and gravel deposits inside and 

adjacent to the study area are probably similar in quality to 

sand and gravel currently mined nearby at several pits 

along Surprise Valley Road. However, access to the deposits within the study area is poor and, in some cases, is 

restricted by enclosure within private lands. It is unlikely 

that the study area deposits would be mined in preference 

to other deposits along the highway within the foreseeable 

future. Therefore, the estimated 8.5 million yd3 of sand and 

gravel within the Eagle and Barber parcels are classified as 

an inferred subeconomic reserve.

Zeolites

Zeolite in the study area occurs as fine- to coarsegrained aggregates that form amygdules in lava and narrow 

veins along fractures in the volcaniclastic rocks. Amygdular basalt lavas underlie an estimated 2 mi2 of the study area 

in the Emerson, Barber, and Van Riper parcels. In area N,

(fig.2) the amygdules contain the zeolites phillipsite, thomsonite, analcime, chabazite, stilbite, and natrolite. Zeolites 

typically comprise about 5-15 percent of the lavas; some 

select samples may contain 30-40 percent zeolite. The 

amygdules are mostly less than 0.25 in. (inch) across although some exceed 1 in. in diameter. The zeolite veins 

commonly occur with calcite and are typically less than 2 

in. thick.

Certain natural zeolites are used as chemical sieves for 

their ability to selectively absorb and release cations or 

anions. Zeolitic rocks occurring in the study area have 

cation exchange capacities of less than 0.61 millimole 

equivalents per gram. This exchange capacity is lower than 

that of commercially mined zeolites that do not require 

beneficiation, as would zeolites in the study area. Ammonium cation exchange capacity of 2 millimole equivalents 

per gram of sample is desirable, and 1.0 to 1.5 millimole 

equivalents per gram are commonly the lowest acceptable 

values. The zeolites in the study area are classified as 

small, low-grade occurrences because they have a low 

cation exchange capacity, and their occurrence in veins and 

amygdules requires beneficiation. No amygdular zeolite 

occurrences in basalt have ever been mined commercially.

Energy Resources

Geothermal Energy Resources

The study area is located near the Lake City-Surprise 

Valley Known Geothermal Resource Area (KGRA) (Hedel, 

1981). No commercial development of geothermal energy 

resources has taken place in this KGRA. The study area 

has neither geothermal leases nor applications and has not 

been explored for geothermal energy resources. An exploratory geothermal well drilled about 3.5 mi east of the 

Milk parcel (sec. 11, T. 41N., R. 16E.; 7,000 ft depth) did 

not lead to commercial development of geothermal energy 

resources and was abandoned. Ten other exploratory wells 

drilled in Surprise Valley north and northeast of the study 

area are either idle or abandoned (Hedel, 1981).

There are several warm springs in and near the Barber 

parcel, and many hot springs lie outside the study area in 

Surprise Valley (Slosson, 1974; Woods, 1974; Hedel, 1981; 

Majmundar, 1983, 1984). Surface temperatures of two 

warm springs in the Barber parcel were measured during 

this study. The warm spring located in the study area about 

700 ft north of Barber Creek (fig. 2, area Q) is 64 °F, and 

the warm spring located on the north bank of Barber Creek 

about 1,100 ft west of the study area is 65 °F. The area of 

influence of these warm springs is estimated to be at least 

0.06 mi2, about one-half of which is in the study area. 

Estimates of temperatures at depth could not be made for 

the warm springs. Flow rates of the two warm springs were 

visually estimated at between 5 and 50 gallons per minute.

Mineral Resources of the South Warner Contiguous Wilderness Study Area, California F7
Table 1. Mines, prospects, claims, and mineralized areas in and near the South Warner Contiguous Wilderness Study Area, 

Modoc County, Calif.

Map 

letter 

(fig. 2)

Name Summary Workings and production Sample and resource data

D

Granger claim 

group

Captain, 

Canteene, 

Surprise claims

Mammoth Cave, 

Bismark, Acma, 

Cosmopolitan 

claims

Rouse Rock, 

White Metal 

Queen lode 

claims; Deep 

Creek, Sylvia, 

Galdia oil 

placers

Hedgepath and 

Summit Slide 

lode claims; 

Granger, 

Monarch, and 

Dolphin oil 

placers

Spar 1-2 claims

Bagley mine 

(Ocheo, Big 

Molley, Iceberg 

Spar groups)

Andesitic tuff-breccia cut by quartz 

veins along faults and shear zones. 

North to northeast trending, highangle, lenticular veins, as much as 

10 ft wide and 500 ft long contain 

20 pet to 90 pet fine-grained white 

quartz and angular silicified 

fragments of wallrock. Some 

limonite staining and some vuggy 

quartz. Calcite, barite and zeolites 

are minor constituents. Wallrock 

between major veins infused by 

quartz veinlets and lightly stained by 

limonite.

Quartz-calcite-zeolite vein as much as 

4 ft thick, nearly vertical, striking 

N40°-50°E.; hosted by andesitic 

tuff-breccia. Minor limonite and 

chlorite along vein and in wallrock.

Andesitic tuff breccia cut by calcitequartz-zeolite veins and limonitic 

shear zones. Mudstone hostrock is 

limonitic and may have been a soil 

horizon for small petrified logs.

Andesitic tuff breccia and basaltic 

dikes and sills; veins and veinlets of 

zeolites, quartz, and calcite. 

Limonite staining is widespread.

Limonitic, sheared, andesitic tuff 

breccia.

Sheared, limonitic zone in andesitic 

tuff breccia.

Calcite-rich veins in andesitic tuff 

breccia. Possible optical-grade 

calcite crystals and cleavage 

fragments. Some limonite staining 

and alteration on wallrocks.

Two small pits or 

trenches.

Small trench.

Small pits.

None.

None.

None.

Two trenches about SO ft 

long and at least four 

small pits or trenches. 

About 1000 oz of 

optical calcite were 

produced in 1920 and 

1921. An unknown 

amount was produced in 

the early 1940's and 

about 1,000 Ib of 

chemical grade calcite 

was produced in the late 

1940's.

Seven chip samples, one grab sample, 

and one alluvial sample were taken. 

Maximum gold content was 170 ppb 

(parts per billion). Other samples with 

detectable gold contained 6, 9, 21, and 

24 ppb. The alluvial sample contained 

a trace of gold, about 0.00002 oz/yd3 

(troy ounces per cubic yard), worth 

about 1 cent per yd3 *. No economic 

amounts of any element were detected.

Three chip samples and one alluvial 

sample were taken. One rock sample 

contained 9 ppb gold, the rest <5 ppb. 

The alluvial sample contained no 

detectable gold. No economic amounts 

of any element were detected in any of 

the samples. One of the rock samples 

contained traces of hydrocarbons.

Seven chip and two alluvial sample were 

taken. No economic amounts of any 

element were detected in any of the 

samples. Three rock samples 

contained traces of hydocarbons.

Three chip samples and one alluvial 

sample were taken. No economic 

amounts of any element were detected. 

One rock sample contained traces of 

hydrocarbons.

Six chip samples, one grab sample, and 

one alluvial sample were taken; no 

economic amounts of any element were 

detected. One rock sample contained 

traces of hydrocarbons.

A chip sample was taken; no economic 

amounts of any element were detected.

Two chip samples and one grab sample 

were taken; no economic amounts of 

any element were detected. No optical 

calcite was found.

F8 Mineral Resources of Wilderness Study Areas: Northeastern California and Washoe County, Nevada
Table 1. Mines, prospects, claims, and mineralized areas in and near the South Warner Contiguous Wilderness Study Area, 

Modoc County, Calif. Continued

Map 

letter 

(fig- 2)

Name Summary Workings and production Sample and resource data

H Lazarus claim

Rattlesnake, 

McCulley, 

Mabel claims

Eagle, Cornucopia 1-2, Silver 

Eagle claims

K Eagle Creek sand 

and gravel

Holden Dick, 

Lorel claims

M

N

Barber Creek 

sand and gravel

Zeolite 

occurrences

O Pozzolan

occurrences

One-hundred 

claims

Jasper and Agate 

claims

Andesitic tuff breccia with andesite 

and basalt dikes. Some sheared 

zeolitic and calcitic veins.

Andesitic tuff breccia; some mafic 

dikes. Much calcite, zeolite, and 

quartz vein material along dikes and 

fractures. Abundant limonite 

staining.

Andesite lava and rhyolite ignimbrite; 

basaltic dikes and sills, some 

sheared. Limonitic staining locally 

abundant Some local chloride and 

argillic (?) alteration.

Bench gravel in the southeast part of 

the Eagle Creek parcel contains 

rounded to subangular cobbly, 

pebbly, sandy gravel from volcanic 

source rocks.

Basalt lava, dikes and sills, and 

rhyolite ignimbrite. Much zeolite, 

calcite, and quartz filling in vesicles 

and fractures. Some moss agate.

Bench gravel in the Barber Creek 

parcel contains sand and gravel 

derived from volcanic source rocks.

Amygdular basalt locally contains at 

least SO pet zeolites, mainly 

phillipsite, thomsonite, analcite, and 

chabazite; accompanying minerals 

are calcite, quartz, chlorite, and 

epidote.

Hard to friable rhyolite ignimbrite and 

pumiceous tuff.

Rhyolite tuff with some limonite 

staining and si]icification(?). Some 

knobby, rounded, siliceous nodules 

in the rhyolite.

Rhyolite lava, banded and nodular, 

with silicification and limonite 

staining. Some obsidian and perlite. 

Warm springs with temperatures of 

64°-65°F are inside the study area 

and adjacent to the west Other 

springs nearby flow at 47°-55°F.

None

None

Two areas of placer 

mining; at least 20,000 

yd3 mined within the 

study area, and 20,000 

yd3 outside and adjacent 

to the east

None within study area; 

sand and gravel pit in 

extension of same 

deposit at Eagleville.

None

None

None

Small pits

Pit 9 ft by 7 ft by 3 ft.

Small pits and trenches, at 

least one short adit

Ten chip samples and one alluvial sample 

were taken; no economic amounts of any 

element were detected.

Six chip samples and one alluvial sample 

were taken ; no economic amounts of any 

element were detected.

Eight alluvial samples were taken; one had 

a trace of gold, about 0.00002 oz/yd3 , 

worth an estimated 1 cent per yd3 *. 

Eleven chip samples and four grab 

samples were also taken. One sample 

had 6 ppb gold. No economic amounts 

of any element were found.

An estimated 2.5 million yd3 of sand and 

gravel within the study area and 33.5 

million yd3 adjacent and to the northeast

Six chip samples, two grab samples, and 

four alluvial samples were taken; no 

economic amounts of any element were 

detected.

An inferred 6 million yd3 of sand and 

gravel within the study area and 25 

million yd3 adjacent to the north and 

east.

Zeolitic rock underlies about 2 mi2 (square 

miles) of the Emerson, Barber, and Van 

Riper parcels. Cation exchange capacity 

of 31 whole-rock samples is uneconomically low, less than 0.61 millimole 

equivalents per gram.

Four samples contained an average of 62 

pet SiO2, 15 pet AljOj, and 4 pet Fe2O,, 

and had an average loss on ignition of 8 

pet . The tuffs crop out over about 2 mi2 

of the Barber parcel and extend into the 

Emerson Parcel.

Three chip samples were taken. One 

contained 6 ppb gold. No economic 

amounts of any element were detected.

Seven chip samples, three grab samples and 

two alluvial samples were analyzed. No 

economic amounts of any element were 

detected. Perlite occurrences total about 

10,000 tons in the study area.

*Gold assumed 1,000 fine, and gravel assumed to expand 25 pet on excavation. Gold price assumed $450/ troy ounce.

Mineral Resources of the South Warner Contiguous Wilderness Study Area, California F9
Warm springs in and near the Barber parcel may be suitable 

for small-scale, low-temperature space heating. The Barber 

parcel contains a small, marginally economic, geothermal 

resource suitable for space heating.

Hot springs outside the study area at Menlo Baths, 

located about 1,200 ft east of the Barber parcel, have surface temperatures of 127°-138 °F and flow at rates of several thousand gallons per minute (Hedel, 1981). The surface temperatures of most of the other springs in or near the 

Barber Creek and Van Riper parcels are between 50 and 55 

°F, close to the mean annual temperature of 49.7 °F recorded for Cedarville, Calif. (National Oceanic and Atmospheric Administration, 1974).

Oil and Gas

No oil and gas resources are identified. No surficial 

indications of oil and gas resources are present in the study 

area. No oil slicks on water, gas bubbles in water, or other 

visual evidence of hydrocarbons were noted (see Emmons, 

1921). Traces (less than 0.5 weight percent) of hydrocarbons were extracted from some samples in the Granger, 

Milk, and Cottonwood parcels by solvent leaching (see 

Emmons, 1921, p. 28). Possible source beds for hydrocarbons include lignite beds reported in and near the study 

area by Russell (1928).

There are no oil and gas leases in the study area, and 

there has been no exploratory drilling for oil and gas in the 

study area. An exploratory geothermal well, 7,000 ft deep 

and located about 3.5 mi east of the Milk parcel (sec. 11, 

T. 4IN., R. 16E.), showed no indications of oil and gas 

resources. Another drill hole, located 0.4 mi northeast of 

the Granger parcel (sec. 29, T. 42N., R. 16E.), likewise 

provided no evidence of oil and gas resources.

Traces of solvent-extractable hydrocarbons were detected in some rock samples, and organic-rich source rocks 

have been postulated to occur at depth in this region 

(Russell, 1928; Alldredge and Meigs, 1984). Should such 

source rocks exist, they would most likely be nonmarine in 

depositional environment and would generate natural gas 

but not oil. Scott (1983) considered the region including 

the study area to have low to zero potential for oil and gas.

Coal

Layers of lignite, mostly 1 in. or less thick, have been 

reported in a carbonaceous zone about 300 ft thick in the 

andesitic tuff breccias and conglomerates in or near the 

study area (Russell, 1928). Although some weakly carbonaceous tuff was observed in the north half of the study 

area during this study, no coal was identified. Lignite coal 

that reportedly occurs near the study area was considered 

no-economic by Russsell (1928). The few carbonaceous 

beds observed during this study are uneconomic occurrences.

ASSESSMENT OF MINERAL RESOURCE 

POTENTIAL

By Michael C. Sawlan and James G. Frisken 

U.S. Geological Survey

Geology

The South Warner Contiguous Wilderness Study Area 

lies along the west margin of the Basin and Range province, an area characterized by north-trending ranges and 

intervening basins bounded by normal faults. The study 

area is underlain by Oligocene and Miocene volcanic rocks 

which form a gently west-dipping (20°-25°) homocline at 

least 10,000 ft thick. A variant in the structure occurs in 

the southern part of the study area in the Barber parcel 

where basalt and tuff dip to the east approximately 

25°-35°. This area is separated from the west-dipping 

homocline by a fault. A generalized geologic map of the 

study area is shown in figure 2.

The homocline of the Warner Mountains is bounded 

on the east by the Surprise Valley fault zone. East of this 

fault zone, the Oligocene and Miocene strata have been 

downdropped at least 11,800 ft relative to strata in the 

Warner Mountains. Data from a drill hole in Surprise 

Valley indicate that these strata are buried by a minimum 

of 6,900 ft of alluvial and lacustrine deposits (Duffield and 

Foumier, 1974; Duffield and Weldin, 1976; Duffield and 

McKee, 1986).

Description of Stratigraphic Units

The Oligocene and Miocene strata are assigned to six 

units shown in figure 2. Some descriptive names of units 

are changed as noted. From oldest to youngest, these are: 

(1) andesitic volcaniclastic and sedimentary rocks (sedimentary rocks unit of Duffield and Weldin, 1976), (2) 

composite volcanic rocks, (3) basalt flows, (4) tephra , (5) 

mafic lava flows, and (6) rhyolite (volcanic rocks unit of 

Duffield and Weldin, 1976). These rocks range in age from 

about 34 to 14 Ma (million years) based on K-Ar ages reported by Duffield and McKee (1986). The andesitic 

volcaniclastic rocks unit is about 34 to 27 Ma in age. The 

composite volcanic rocks unit, which includes andesite 

lavas and ignimbrite, ranges in age from about 26 to 17 Ma. 

The four youngest units (basalt flows, mafic lava flows, 

tephra, and rhyolite) erupted in a relatively short time 

period, between 16 and 14 Ma.

Andesitic Volcaniclastic and Sedimentary Rocks

The oldest rocks in the study area are andesitic volcaniclastic rocks that underlie the five northernmost parcels 

(fig. 2). These rocks include andesite tuff breccia and 

conglomerate, subordinate sandstone, and minor andesite

F10 Mineral Resources of Wilderness Study Areas: Northeastern California and Washoe County, Nevada
or green, pervasively fractured beds, typically 20-80 ft 

thick, of unsorted, angular andesite clasts in a matrix of 

lithic fragments and ash. Clasts in the tuff breccia are 

characteristically matrix-supported. Lithic fragments range 

in size from millimeters to several meters and are dominantly porphyritic pyroxene and hornblende andesite and 

aphyric basaltic andesite. Subordinate clast lithologies 

include subrounded ovoid clasts of hornblende and (or) 

biotite granodiorite, and plagioclase-rich basalt composed 

of large (as much as 0.4 in. across), densely crowded, 

aligned, tabular, plagioclase phenocrysts. The matrix of the 

tuff breccia is composed of comminuted lithic fragments, 

ash which is largely altered to clay, and broken phenocrysts. The tuff breccia commonly contains petrified or 

charred wood ranging from small twigs to logs several 

yards in length. The charred wood suggests that some tuff 

breccia formed as hot volcanic debris flows.

The andesitic tuff breccia is a rock type commonly 

attributed to lahars or mudflows deposited on the distal 

flanks of andesitic stratovolcanoes. Duffield and Fournier 

(1974) identified two vent complexes, 7 and 10 mi north of 

the study area, which may have been the source for some 

of the andesite volcaniclastic rocks. K-Ar ages on andesite 

from these eruptive centers are 26.6±1.1 Ma and 28.7±1.1 

Ma, respectively (Duffield and McKee, 1986).

Conglomerate and sandstone contain clasts similar to 

those that occur in the andesitic tuff breccia; these rocks 

generally increase in proportion from south to north within 

the study area. In contrast to the tuff breccia, these clastic 

rocks are distinctly clast-supported. Hornblende-bearing 

andesite ash beds are a volumetrically minor constituent of 

this unit. Dates on andesite ash beds from three localities 

range from 28.8+1.0 Ma to 33.9±2.7 Ma (Duffield and 

McKee, 1986). The 34-29 Ma age range of andesite ash 

beds suggests that older sources for the andesite volcaniclastic rocks are required in addition to the younger (26.6 

and 28.7 Ma) sources identified by Duffield and Fournier 

(1974).

K-Ar ages on biotite from ignimbrites located stratigraphically below and above andesitic lavas. K-Ar ages of 

25.411.0 and 26.3±1.0 Ma are reported for ignimbrite near 

the base of the unit; and an age of 17.3±0.6 Ma is reported 

for ignimbrite located near the top of this unit (Duffield and 

McKee, 1986). No K-Ar ages have been reported for the 

lavas from this unit.

Basalt Flows

The basalt flows unit occurs in only the southermost 

parts of the study area, in the Emerson, Barber and Van 

Riper parcels. This unit includes black, typically vesicular 

and amygdaloidal, aphyric basalt and sparsely porphyritic 

oh'vine basalt Vesicles are typically partially filled with 

zeolites. Basalt from the northeast part of the Emerson 

parcel has been dated at 15.8±0.5 Ma; six K-Ar ages on 

basalt from elsewhere in the South Warner Mountains 

range from about 16 to 14 Ma (Duffield and McKee, 1986).

Tephra

The tephra unit occurs in spatial association with rhyolite lavas in the southern part of the study area, largely in 

the Barber parcel. This poorly exposed unit includes 

bedded rhyolitic lithic pumice tuff locally intercalated with 

basalt flows.

Mafic Lava Flows

Mafic lava flows occur adjacent to the Van Riper 

Parcel in the southern part of the study area. This unit 

includes porphyritic basalt lava flows, 10-20 ft thick, and 

porphyritic andesite lava that typically forms massive to 

platy-jointed flows as much as 200 ft thick. No K-Ar ages 

are available for this unit

Composite Volcanic Rocks

The composite volcanic unit comprises late Oligocene 

and early Miocene rhyolite ignimbrite and andesite and 

dacite(?) lavas. This composite volcanic unit underlies the 

Eagle and parts of the Barber parcels. The rhyolite ignimbrite is typically white, partly welded, lithic-bearing, biotite-quartz-feldspar rhyolite ash-flow tuff with abundant 

flattened pumice lumps, typically 0.2-0.8 in. across. The 

lavas are dominantly gray and greenish-gray porphyritic 

andesite containing plagioclase, and pyroxene and (or) 

hornblende phenocrysts. At the Eagle parcel, the section 

includes ignimbrite which is underlain by andesite lava and 

overlain by thick (as much as 200 ft) andesite and dacite 

lava. Further south, in the Barber parcel, only the ignimbrite is exposed. The age range of this unit is bracketed by

Rhyolite

The rhyolite unit occurs in the study area only in and 

around the Barber parcel. This unit includes flow-banded, 

locally hematite-stained, porphyritic biotite feldspar rhyolite flows. Rhyolite from within and adjacent to the 

Barber parcel is about 16 Ma old on the basis of K-Ar ages 

of 15.5±0.5 Ma and 15.9±0.5 Ma reported by Duffield and 

McKee (1986).

Surficial Deposits

Two types of Quaternary surficial deposits are distinguished in the geologic map shown in figure 2: alluvium 

and gravel. In the study area, alluvium comprises unsorted

Mineral Resources of the South Warner Contiguous Wilderness Study Area, California F11
to poorly sorted silt, sand and gravel. Farther east, this unit 

also includes lacustrine deposits, rare, thin tephra beds, and 

stream channel deposits. Gravels form deltaic fans deposited in large Surprise Valley lake(s) during high lake levels 

in Quaternary time. These deltaic fans are 0.5-2 mi across 

and 15-40 ft thick and are located along the east slope of 

the Warner Mountains adjacent to the Surprise Valley fault 

zone. Most of the gravel deposits occur outside of the 

study area; small parts of these deltaic fans are included in 

parts of the Eagle and Barber parcels. These gravels typically exhibit better sorting with a higher proportion of sand 

and gravel relative to silt than most alluvial fill in Surprise 

Valley.

Intrusive Rocks

Dikes and sills of andesitic composition intrude tuff 

breccia and conglomerate of the andesitic volcaniclastic 

and sedimentary rocks unit, and ignimbrite and andesite 

lava flows of the composite volcanic unit. Dikes are locally abundant, particularly in the area west of Eagleville 

where a set of light gray, subvertical, generally east-trending dikes several hundred feet in height are exposed in the 

range-front scarp. The dikes include aphyric microcrystalline andesite as well as andesite with hornblende or 

pyroxene phenocrysts. These dikes are not shown on the 

generalized geologic map of figure 2.

Structure

The most prominent structure in the study area is the 

Surprise Valley Fault zone, which has been active in the 

Pleistocene and Holocene (Hedel, 1980, 1981). This fault 

zone is marked by abundant geomorphic evidence of youth 

including the abrupt, steep, prominent range-front scarp, 

faceted spurs, perched stream terraces, small young alluvial 

cones, and offset surficial deposits within 2-3 mi of the 

main scarp. All parcels are located on the footwall (the 

relatively upthrown side of the fault) immediately west of 

the Surprise Valley fault zone. East of the Surprise Valley 

fault zone, this volcanic section is buried by at least 6,900 

ft of alluvium in the Surprise Valley basin (Duffield and 

McKee, 1986). At least 11,800 ft of vertical offset is 

indicated along the Surprise Valley fault zone (Duffield and 

McKee, 1986). The age of the inception of faulting on the 

Surprise Valley fault zone is not well constrained.

In addition to the major north-northwest-trending basin 

and range faulting exemplified by the Surprise Valley fault, 

an earlier period of faulting is indicated by several major 

northeast-trending faults. These faults exhibit significant 

vertical displacement of Tertiary volcanic strata as young 

as 14 Ma (fig. 2) and are truncated by the Surprise Valley 

fault zone. The earliest age of activity on the northeasttrending faults is not known.

Tuff breccia of the andesitic volcaniclastic and sedimentary rock unit characteristically is pervasively fractured. North- and northeast-trending fracture sets, with a 

spacing of 2 to 12 in., are particularly common; their genesis and relation to mapped faults is unknown.

Oligocene and Miocene strata form a gently west-dipping (20°-25°) homocline throughout the Warner Mountains except in the southern part of the study area, in the 

Barber parcel, where basalt and tuff strata dip to the east 

approximately 25°-35°. This area is separated from the 

west-dipping homocline by a fault.

Alteration and Mineralization

Two principal types of alteration and mineralization 

are observed in and adjacent to the study area. These 

include a weak epithermal gold mineralization and a regional alteration resulting in precipitation of zeolite, zeolite 

and calcite, calcite, or zeolite with minor grayish-brown 

chalcedony or milky white opal. Some calcite veining may 

be related to the epithermal mineralization. Both alteration 

types are strongly fracture controlled, resulting in planar 

alteration zones. The relative timing of the alteration types 

is not well constrained. At least some zeolite-related alteration post-dates the epithermal alteration, as evidenced by 

zeolites lining vugs in silicified rock, but earlier zeoliterelated alteration cannot be ruled out Epithermal mineralization and (or) alteration is observed in the Granger, 

Homback, Eagle, and Barber parcels. In the following 

discussion on alteration, geochemical anomalies are noted; 

these geochemical data are more fully discussed in a later 

section.

Mineralized zones in the Granger Creek area, most of 

which are located north of the Granger parcel, are narrow 

(2- to 10-ft-wide), subvertical to steeply dipping, planar to 

broadly lensoidal, strongly silicified zones along north- and 

northeast-trending faults and (or) fractures. These zones 

cut gently west-dipping andesitic tuff breccia, and volcanic 

conglomerate and sandstone. Alteration zones range in 

length from several tens of feet to about 500 feet Silicified 

zones are characterized by quartz veins and vein breccias 

and (or) dark reddish-brown to dark gray pervasively silicified volcaniclastic rock. The silicified areas may include 

sulfide and (or) limonite. The larger quartz veins range 

from white and pale yellowish-white, massive, thick (as 

much as 5 ft), finely crystalline quartz to translucent microcrystalline druse along fractures. Pervasively silicified 

rock ranges in color from gray to dark reddish-brown, 

depending on whether sulfides have been oxidized. These 

silicified zones characteristically form narrow ridges 2-8 ft 

high. The silicified zones may also include calcite, ferruginous calcite, and barite veins, and clay alteration dominated 

by kaolinite. Alteration envelopes adjacent to the strongly 

silicified zones are typically narrow, 3-10 ft wide. Broader 

alteration zones, as much as 50 ft wide, locally occur in 

volcanic sandstone and are characterized by rust-brown to 

reddish-brown limonite staining along fractures. Within 

the silicified zones, vugs and fractures may be lined with

F12 Mineral Resources of Wilderness Study Areas: Northeastern California and Washoe County, Nevada
platy, crystalline, pale pink to colorless, translucent zeolite; 

zeolite also occurs outside of the zones related to silicification and, as noted above, may be unrelated to the silicification and mineralization.

Slickenslides generated by fault movement are observed along parts of some planar alteration zones. Fault 

displacements are difficult to define due to the absence of 

distinctive, continuous stratigraphic marker beds. Displacements along the silicified zones appear to be minor, 

however, as the major lithologic units are not offset significantly and the faults cannot be traced much beyond the 

silicified zones.

Rocks containing anomalous gold concentrations occur 

largely in the silicified zones. The higher gold anomalies 

most commonly are found in silicified rocks and vein 

breccia containing visible sulfide and (or) strong limonitic 

staining and boxwork after sulfide. Mineralized and altered 

rocks also yield geochemical anomalies, most notably of 

mercury, antimony, arsenic, molybdenum, copper, lead, 

silver, and cadmium. The maximum gold abundance in 

USGS rock samples collected from the mineralized area at 

Granger Creek is 64 ppb.

Volumes of gold-bearing rock are generally very limited because mineralization is strongly fracture controlled 

and does not extend significantly into the adjacent country 

rock. The volcaniclastic rocks appear to be an unfavorable 

host for replacement mineralization. Limonite-veined volcaniclastic rocks adjacent to the fracture-controlled alteration zones have anomalous concentrations of mercury, 

arsenic, and associated elements, possibly due to secondary 

remobilization, but only low levels of gold (<5 ppb) were 

detected in these rocks.

Alteration observed in the central part of the Eagle 

parcel comprises a narrow (2- to 5-ft-wide), subvertical, 

northeast-trending, silicified, limonitic shear zone that 

forms a discontinuous (2- to 5-ft-high) ridge within ashflow tuff. This area is located on the main northeast-trending ridge in the parcel (SWV4, sec. 26, T. 40N., R. 16E.). 

This alteration zone locally exhibits fault Slickenslides and 

can be traced for approximately 150-200 ft. A sample 

from this zone yielded anomalous concentrations of mercury, arsenic and lead. At the mouth of Eagle Creek, alteration occurs along a north-northwest-trending fracture 

zone or fault. Here, the alteration is characterized by minor 

quartz, chalcedony, and calcite veinlets, barite and zeolite 

in vugs, ochre-colored limonite, red hematitic and (or) 

cinnabar staining along fractures, and weak clay alteration 

of andesite lava. A sample of quartz and limonite-veined, 

partly clay altered andesite from this area contains anomalous concentrations of gold (9 ppb), as well as mercury and 

arsenic. About 0.15 mi southeast along strike from this 

altered area, fractured andesite containing minor calcite has 

anomalous concentrations of mercury and molybdenum.

In the Hornback parcel, sparse localized alteration has 

produced partial clay alteration of andesite, as well as thin 

(<0.2 in.), finely crystalline quartz veinlets and abundant limonite-coated fractures within the andesite. Mercury and 

arsenic anomalies are associated with the limonitic fractures. Alteration was also noted in stream cobbles of altered tuff and chalcedony. The tuff is partly kaolinized and 

contains thin quartz veins, limonite, and small pockets of 

calcite. The chalcedony is gray and includes pervasive 

veinlets of yellow-brown limonite. Both the altered tuff 

and veined chalcedony have anomalous concentrations of 

mercury, arsenic, and molybdenum.

In the Barber parcel, vesicular basalt flows located in 

the northeast part of the parcel contain abundant zeolites in 

vugs. Fractured, locally iron-stained basalt lava contains 

anomalous concentrations of gold (7 ppb) and copper (200 

ppm). Rhyolitic lithic pumice tuff exposed in a roadcut 

along the south margin of the parcel contains thin (<0.4 

in.), soft, brown clay-rich veins along fractures; these veins 

have anomalous concentrations of mercury and arsenic 

compared to the host tuff. Rhyolite lava and ignimbrite 

exposed in the northeast part of the parcel exhibit alteration 

or weathering of the glassy groundmass to green and yellow-white clays, respectively, but biotite and feldspar 

phenocrysts appear to be fresh. These rocks have relatively 

high concentrations of silver (10 ppm). Rhyolites are 

known elsewhere to contain similar concentrations of silver 

in unaltered rock. It is not clear whether the silver anomalies here are related to a widespread, subtle alteration or 

reflect relatively high magmatic silver concentrations. 

Minor silicification and clay alteration along Slickenslides 

in faulted rhyolite ignimbrite were noted in the northeastern 

part of the parcel but yielded no geochemical anomalies. In 

the southeastern part of the parcel, a clay and chalcedony 

vein cutting pumice lapilli tuff show anomalous concentrations of gold (3 ppb), mercury (100 ppm), and arsenic (6 

ppm); these veins did not appear to be common. Rhyolite 

lava in the southwest part of the Barber parcel is commonly 

stained with hematite along fractures, and locally contains 

pockets of silicification: two samples show minor gold 

anomalies (4 and 12 ppb).

Alteration at mercury prospect pits located about 2 mi 

north of Granger Creek, (between North Deep Creek and 

South Deep Creek) occurs along north- and northeasttrending fractures and (or) faults. Here, mercury mineralization is concentrated in dark reddish-brown, narrow, silicified zones, 2-6 ft wide, that locally contain barite veins and 

limonite. Adjacent country rocks are stained by limonite, 

hematite, and cinnabar along fractures, are locally altered to 

kaolinite, and have anomalous concentrations of mercury. 

Although samples from the Deep Creek area have high 

mercury concentrations (to 230 ppm), they are virtually 

devoid of gold; of the 12 samples from the prospect pits 

and nearby rocks, only one sample of green tuff contain 

detectable gold (2 ppb). Anomalous arsenic (<42 ppm), 

antimony (^24 ppm), boron (<100 ppm), barium (>5,000 

ppm), lead (<70 ppm), molybdenum (^10 ppm), and copper 

(<150 ppm) are also observed in various samples from this 

area.

Mineral Resources of the South Warner Contiguous Wilderness Study Area, California F13
Geochemical Studies

Methods and Background

A reconnaissance geochemical study conducted by the 

USGS in and near the study area consisted of the collection, analysis, and evaluation of rock, stream-sediment, and 

heavy-mineral-concentrate samples.

The rock samples provide direct information on rock 

geochemistry. Samples that appeared fresh and unaltered 

were collected to provide information on geochemical 

background values, and those deemed altered or mineralized were collected to determine the suite of elements that 

characterize the alteration or mineralization. In all, 174 

rocks were sampled from outcrops and an additional 10 

rocks were collected as stream float.

The stream-sediment, and nonmagnetic heavy-mineral 

panned-concentrate samples (herein referred to as heavymineral concentrates) are collected primarily for their ability to reveal metal anomalies within drainage basins. 

Stream sediments represent a composite of rock and soil 

exposed upstream from the sample site. The processing of 

heavy-mineral concentrates tends to remove common rockforming minerals and to concentrate ore and ore-related 

minerals. Analysis of this heavy-mineral concentrate provides data for some elements of interest that are not easily 

detected in bulk stream sediments. Twenty-five sites along 

stream channels containing recent alluvium were sampled 

for stream sediments. Heavy-mineral concentrates were 

obtained at 24 of these sites. Because of the small size of 

the parcels, the drainage basins from which the streamsediment samples are derived in most instances extend 

beyond the surface area of the study area parcels into the 

adjacent South Warner Wilderness (within the Modoc 

National Forest). Less commonly, samples from small 

tributary drainages were derived from areas largely within 

the study area parcels. One water sample was collected 

from Van Riper Spring and analyzed for uranium (0.2 ppb).

Several analytical methods were employed, depending 

on the elements of interest. The rock, stream-sediment, and 

heavy-mineral-concentrate samples were analyzed for 31 

elements (silver, arsenic, gold, barium, beryllium, bismuth, 

boron, cadmium, calcium, cobalt, chromium, copper, iron, 

lanthanum, magnesium, manganese, molybdenum, niobium, nickel, lead, scandium, antimony, tin, strontium, 

thorium, titanium, vanadium, tungsten, yttrium, zinc, and 

zirconium) by a six-step semiquantitative emission-spectroscopy method routinely used by the USGS (Grimes and 

Marranzino, 1968). Germanium, gallium, sodium, and 

phosphorus contents were also determined by this method 

on most of the rocks. Several elements of special interest 

were also analyzed by more sensitive techniques. Gold 

concentrations were determined in the rocks and stream 

sediments by a graphite furnace atomic-absorption method 

having a detection limit of 2 ppb (Meier, 1980). Gold 

analyses obtained by this method largely represent the gold 

introduced into the rock by mineralization and not the total

gold concentrations in the rock; the common rock-forming 

silicates, which may contain trace amounts (<5 ppb) of 

gold, are not decomposed by the method used in gold 

analysis sample preparation. Mercury was detected by a 

cold vapor atomic-absorption method having a detection 

limit of 20 ppb (Koirtyohann and Khalil, 1976). Low-level 

antimony, arsenic, bismuth, cadmium, and zinc concentrations were determined by inductively coupled, argonplasma atomic-emission spectroscopy (Crock and others, 

1987). Detection limits for these elements are shown in 

parentheses as follows, in ppm units: antimony (2), arsenic 

(5), bismuth (2), cadmium (0.1), and zinc (2). In addition, 

the stream-sediment samples were analyzed for thorium 

and uranium by a delayed neutron technique (Millard, 

1976). Anomalous values were determined by statistical 

methods, by comparison of mineralized and altered samples 

with their unaltered equivalents, and by comparison with 

published data for common rock types. Analytical data, 

sample-location maps, and a detailed description of the 

sampling and analytical techniques are presented by 

Adrian, B.M (written common., 1988).

In addition to samples collected during the present 

study, the geochemical data from the study of the South 

Warner Wilderness (Duffield and Weldin, 1976) were 

examined. Data for 37 stream-sediment and 50 rock 

samples collected within or near the nine study area parcels 

were compiled and included in the present interpretations. 

These samples were analyzed by the same spectrographic 

method for 30 elements (as above less thorium), for gold 

with a detection limit of 50 ppb, and for mercury. During 

the 1976 study, the USBM collected nine reconnaissance 

placer samples from streams draining the east slope at the 

South Warner Mountains including Milk Creek, Steamboat 

Canyon, Cottonwood Creek, Jackson Canyon, Owl Creek, 

Raider Creek, Eagle Creek, Kaiser Canyon, and Emerson 

Creek. No gold was detected in these concentrates nor in 

any of the 24 heavy-mineral concentrates collected by the 

USGS during the present study. Only two low-level gold 

concentrations were found in the 553 rock samples and the 

315 stream-sediment samples collected during the study of 

the entire South Warner Wilderness (Duffield and Weldin, 

1976). It should be noted, however, that the analytical 

detection limit for gold in the present study is much lower 

lower than that of the 1976 study: 2 ppb versus 50 ppb.

Results and Interpretation

Geochemical anomalies, alteration patterns, mineralogy, and some favorable geologic factors suggest that all 

nine parcels in the South Warner Contiguous Wilderness 

Study Area have been subjected to mineralizing processes 

similar to those that have produced epithermal preciousmetal deposits elsewhere. The anomalous concentrations 

of elements form an element suite characteristic of presentday mineralized hot springs and related epithermal gold 

deposits. The geochemical data do not suggest the presF14 Mineral Resources of Wilderness Study Areas: Northeastern California and Washoe County, Nevada
ence of mineral occurrences of types other than epithermal 

precious-metal mineralization. Anomalous concentrations 

of metals such as copper, molybdenum, lead, arsenic, antimony, and mercury, as well as some non-metals, are small 

and characteristic of a precious-metal geochemical association. In addition, no indications of occurrences of radioactive elements are present; sensitive analytical techniques 

used for detecting uranium failed to show any anomalous 

concentrations in the stream-sediment samples.

Anomalous concentrations of elements in samples 

from all three sample media (rocks, stream sediment, and 

heavy-mineral concentrates) occur throughout the study 

area. However, most of the multi-element anomalies and 

all of the pyrite (FeS2), powellite (CaMoO^ and barite 

(BaSO4) seen in the heavy-mineral concentrates occur in 

samples collected from the six northern parcels (Granger, 

Milk, Cottonwood, Owl, Hornback, and Eagle parcels). In 

the stream sediments and heavy-mineral concentrates, the 

anomalous element suite consists, in part, of gold (5-17 

ppb in stream sediment), silver (2-7 ppm in heavy-mineral 

concentrate), arsenic (5-10 ppm in stream sediment), antimony (3 ppm in stream sediment), molybdenum (10-700 

ppm in heavy-mineral concentrate), copper (200-10,000 

ppm in heavy-mineral concentrate), lead (100-1,500 ppm 

in heavy-mineral concentrate), tin (20-100 ppm in heavymineral concentrate), barium (5,000 to greater than 10,000 

ppm in heavy-mineral concentrate), and boron (200 to 

greater than 5,000 ppm in heavy-mineral concentrate). Not 

all elements of this suite are present in all samples exhibiting anomalies; typically, anomalies of two to six elements 

are present in any particular sample.

Gold anomalies (2-17 ppb) were detected in 13 

stream-sediment samples from the Granger (4 of 5 

samples), Milk (1 of 2 samples), Cottonwood (2 of 2 

samples), Hornback (3 of 4 samples), Barber (1 of 6 

samples), and Van Riper (2 of 3 samples) parcels. The gold 

anomalies are less than 8 ppb except for one sample from 

the mouth of Hornback Creek (17 ppb). Compared to gold 

anomalies in stream-sediment samples taken near an active 

gold mine, gold anomalies in the study area are relatively 

small. Stream-sediment samples collected during the present study, taken adjacent to and about 1 mi downstream 

from the volcanic-hosted Hayden Hill gold mine, contain 

2,200 and 50 ppb gold, respectively. Despite detection of 

gold in stream-sediment samples from the study area, 

heavy-mineral concentrates of these stream-sediment 

samples show no gold. This indicates that the gold is very 

fine grained and suggests that economic precious-metal 

deposits are not exposed at the surface and that gold placers 

are not present Duffield and Weldin (1976) found no gold 

anomalies in stream-sediment samples from the South 

Warner Wilderness, but the sediment and rock samples 

collected for this earlier study were analyzed by a less 

sensitive method. Gold was not seen or detected in any of 

the heavy-mineral concentrates. This indicates that the 

gold is either very fine grained and (or) incorporated in

silicate minerals, and that placer-gold deposits most likely 

do not exist in or near the study area. Although no heavymineral concentrate was obtained by the USGS for the 

Eagle parcel, a concentrate obtained by the USBM contained a trace of gold. Silver anomalies were identified in 

three heavy-mineral-concentrate samples from the Granger, 

Owl, and Cottonwood parcels.

Fifty-two of the 234 rock samples have detectable gold 

ranging in value from 2 to 65 ppb. Thirteen of these 

samples have gold values >5 ppb; nine of these are from 

the Granger Creek area, two are from the Eagle parcel, and 

one each is from the Hornback and Barber parcels.

Rock geochemical anomalies in the six northernmost 

parcels correspond with areas in which stream-sediment 

and heavy-mineral-concentrate anomalies are identified, 

and with the areas exhibiting alteration noted above. The 

composite geochemistry of mineralized rocks defines a 

geochemical-anomaly suite that includes gold (<64 ppb), 

silver (<0.5 ppm), mercury (<1.9 ppm), arsenic (<670 

ppm), antimony (<12 ppm), barium (sometimes in excess 

of 5000 ppm), lead (< 50 ppm), molybdenum (20-100 

ppm), and copper (100-500 ppm). Mineralized samples 

have multi-element anomalies, but, as with the streamsediment samples, rock samples are not anomalous in all 

elements of the suite. Rocks containing the largest geochemical anomalies occur in or adjacent to alteration zones 

along north- and northeast-trending structures.

The higher gold, antimony, arsenic, and mercury concentrations in rocks are from the area located immediately 

north of the Granger parcel, on the south-facing slope north 

of Granger Creek. A small planar zone of silicification and 

kaolinization also occurs within the northeast tip of the 

Granger parcel where rock samples are weakly anomalous 

in gold (less than 10 ppb). In the Granger Creek area, all 

gold anomalies greater than 5 ppb occur in the silicified 

zones. Andesite tuff breccia and conglomerate wallrock 

collected adjacent to silicified zones characteristically 

contain only very low gold levels (<5 ppb). Pod-shaped 

volumes of limonitic volcaniclastic rocks that abut silicified 

zones contain weakly anomalous concentrations of mercury, arsenic, or cadmium.

Volcanic sandstone from the Granger and Owl parcels 

has many limonite-stained fractures and contains anomalous concentrations of mercury, arsenic, cadmium, and 

molybdenum. In the Owl parcel, thin sandstone beds 

contain anomalous concentrations of these elements despite 

a lack of apparent alteration and geochemical anomalies in 

overlying and underlying rocks.

Geophysical Studies

Geophysical evaluation of the mineral resources of the 

study area was based on interpretations of previously acquired aerial gamma-ray and aeromagnetic surveys. No 

new geophysical data were collected during the present 

study.

Mineral Resources of the South Warner Contiguous Wilderness Study Area, California F15
Regional aeromagnetic surveys were flown over the 

study area at a constant barometric elevation of 10,000 ft 

above sea level with east-west flightline spacings of about 

1 mi (Duffield and Weldin, 1976). Along the east flank of 

the South Warner Mountains in the vicinity of the study 

area parcels, the magnetic contours define a gentle gradient 

with contours subparallel to the range front along the Surprise Valley fault zone. The magnetic data in this area 

result from the combined effects of the 5,000 ft decrease in 

elevation along the range front (increased distance to the 

magnetometer) and the lower magnetic susceptibility of the 

volcaniclastic rocks along the range front and the alluvium 

in Surprise Valley.

The airborne gamma-ray survey (Aero Service Division, 1981) was flown in east-west lines with a 6-mi spacing, and north-south lines with an 18-mi spacing, at a 

nominal terrain clearance of 400 ft. The radiometric spectra did not indicate any anomalous radioactivity in or near 

the study area.

Neither the aeromagnetic nor aerial radiometric data 

provide constraints on the distribution of mineralization in 

the study area. As noted above, areas exhibiting alteration 

related to gold mineralization are typically only 2-10 ft 

wide; these features are not resolved with geophysical data 

based on widely spaced flighflines.

MINERAL AND ENERGY RESOURCE POTENTIAL 

Mineral Resources

The mineral resource potential of the South Warner 

Contiguous Wilderness Study Area was assessed on the 

basis of geologic investigations, geochemical and geophysical studies, and a study of prospects and claims in the 

area of reported mineral occurrences and deposits in the 

region. The entire study area is assigned a low potential for 

epithermal gold and silver resources, with a certainty level 

of C. This assignment is based on the widespread occurrence of alteration and geochemical anomalies associated 

with or directly indicating precious-metal mineralization.

Results of the present study show that geologic and 

(or) geochemical evidence of precious-metal epithermal 

alteration and mineralization is present throughout the 

study area. Mineralization is most pronounced in the 

Granger Creek area and was probably caused by the circulation of hydrothermal fluids enriched in gold, silver, 

mercury, arsenic, antimony, molybdenum, copper, lead, 

boron, barium, and cadmium through faults and fractures. 

The mineralized areas have alteration and geochemical 

attributes broadly similar to a Sado-type epithermal gold 

deposit characterized by fracture-controlled silicification in 

a volcanic host (Mosier and others, 1986).

Gold occurrences found to date are restricted to small 

volumes of rock along faults and fractures. The mapping

and intensive rock sampling in the most favorable areas for 

gold indicate that gold deposits are not presently exposed in 

the study area. The lack of ore-grade gold concentrations 

in the study area may be explained in several ways. The 

mineralization may represent the base of ore bodies now 

largely removed by erosion, the uppermost expression of a 

deeper system, the periphery of ore bodies displaced by 

faulting, or a weak mineralization event.

Geochemical anomalies in base metals (copper, lead, 

and zinc) and other elements such as mercury, arsenic, antimony, and cadmium do not indicate potential resources for 

deposits of these elements. Concentrations of these elements are far below economic levels, and they are best 

viewed as accessory constituents of the element suite related to epithermal gold-related mineralization.

Although the present study indicates that gold deposits 

are unlikely to be found in the study area, additional geologic and alteration mapping and geochemical studies may 

provide information that could lead to identifying target 

areas in the general region. The objectives of this research 

should focus on establishing the timing of mineralization 

relative to development of pre- and post-mineralization 

structures and identifying favorable host rocks and structural traps.

Geothermal Energy Resources

The Barber and Van Riper parcels have low potential 

for geothermal energy resources, certainty level C, on the 

basis of hot springs located 0.2 mi east of the study area 

(the Menlo Baths) and warm springs within the Barber and 

Van Riper parcels. These resources may be suitable for 

small-scale, low-temperature space heating. In the Lake 

City-Surprise Valley KGRA, which lies north and east of 

the study area, no geothermal leases or applications have 

been taken.

Oil and Gas

Geologic data indicate the absence of oil and gas resources in or near the study area. Although organic-rich 

source rocks have been postulated to occur at depth in this 

region (Russell, 1928; Alldredge and Meigs, 1984, p. 

83-87), they would most likely be nonmarine in origin and 

may possibly generate natural gas but not oil, if they exist 

at all. The Tertiary volcanic and volcaniclastic sequence 

contains only local, thin, and discontinuous layers of sedimentary rock that might act as hydrocarbon reservoirs. 

Rocks that underlie the study area are relatively impermeable as suggested by the apparent confinement of hydrothermal fluids to fractures and faults. There are no active oil 

and gas leases, no exploratory drilling, and no producing 

wells in the study area. Two drill holes located less than 

1 mi northeast of the Granger parcel and about 3 mi east of 

the Milk parcel yielded no evidence of oil or gas resources.

F16 Mineral Resources of Wilderness Study Areas: Northeastern California and Washoe County, Nevada
In a previous assessment of oil and gas potential of wilderness lands, Scott (1983) considered this region to have zero 

to low potential. This report concurs with Scott's (1983) 

earlier finding and the study area is here considered to have 

no potential, certainty level D, for oil and gas resources.

REFERENCES CITED

Aero Service Division, Western Geophysical Company of America, 1981, Airborne gamma-ray spectrometer and magnetometer survey, Alturas quadrangle, California: prepared for the 

U.S. Department of Energy as part of the National Uranium 

Resource Evaluation program under contract no. 

DE-AC13-76GJ01664 and Bendix Field Engineering Corporation subcontract no. 80-460, project no. IG0205, 

GJBX-406/81; final report v. 1, 127 p., and final report v. 2, 

unnumbered.

Alldredge, M.H., and Meigs, J.V., 1984, N.E. California area 

drawing interest: Oil and Gas Journal, v. 82, no. 23, p. 83-87.

American Society for Testing and Materials, 1985, Fly ash and 

raw or calcined natural pozzolan for use as a mineral admixture in portland cement concrete: 1985 annual book of ASTM 

Standards, part 10, section 4, construction; concrete and 

mineral aggregates: Philadelphia, Pennsylvania, American 

Society for Testing and Materials, designation C 618-85.

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.

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.

Duffield W.A., and Fournier, R.O., 1974, Reconnaissance of the 

geothermal resources of Modoc County, California: U.S. 

Geological Survey Open-File Report, 19 p.

Duffield W.A., and McKee, E.H., 1986, Geochronology, structure, and basin-range tectonism of the Warner Range, northeastern California: Geological Society of America Bulletin, p. 

142-146.

Duffield, W.A. and Weldin, R.D., 1976, Mineral resources of the 

South Warner Wilderness, Modoc County, California: U.S. 

Geological Survey Bulletin 1385-D, 31 p.

Emmons, W.H., 1921, Geology of petroleum: New York, 

McGraw-Hill, 610 p.

Gay, T.E., Jr., 1966, Economic mineral deposits of the Cascade 

Range, Modoc Plateau, and Great Basin region of northeastern California, in Bailey, E.H., ed., Geology of northern 

California: California Division of Mines and Geology, Bulletin 190, p. 97-104.

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.

Hedel, C.W., 1980, Late Quaternary faulting in western Surprise 

Valley, Modoc County, California: San Jose, California, 

California State University, M.S. thesis, 113 p.

Hedel, C.W., 1981, Map showing geothermal resources of the 

Lake City-Surprise Valley Known Geothermal Resource 

Area, Modoc County, California: U.S. Geological Survey 

Map MF-1299, scale 1:62,500.

Koirtyohann, S.R., and Khalil, Moheb, 1976, Variables in the 

determination of mercury by cold-vapor atomic absorption: 

Analytical Chemistry, v. 48, no. 1, p. 136-139.

Majmundar, H.H., 1983, Technical map of the geothermal resources of California: California Division of Mines and 

Geology, Geologic Data Map no. 5, scale 1: 750,000.

Majmundar, H.H., 1984, Text for the technical map of the geothermal resources of California geologic data map no. 5: 

California Division of Mines and Geology, 45 p.

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

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

Meier, A.L., 1980, Flameless atomic absorption determination of 

gold in geologic material: Journal of Geochemical Exploration, v. 13, no. 1, p. 77-85.

Millard, H.T., Jr., 1976, Determination of uranium and thorium 

in U.S. Geological Survey standard rocks by the delayed 

neutron technique: U.S. Geological Survey Professional 

Paper 840, p. 61-65.

Miller, M.S., 1988, Mineral resources of the South Warner Contiguous Wilderness Study area, Modoc County, California: 

U.S. Bureau of Mines Minerals Land Assessment Open-File 

Report MLA 20-88.

Mosier, D.L, Berger, B.R., and Singer, D.A., 1986, Descriptive 

model of Sado epithermal veins, in Cox, D.P., and Singer 

D.A., eds., Mineral deposit models: U.S. Geological Survey 

Bulletin 1693, p 155-157.

National Oceanic and Atmospheric Administration, 1974, Climates of the states, vol. 2, western states including Alaska and 

Hawaii: Port Washington, N.Y., Water Information Center, 

Inc., p. 481-975.

Russell, R.J., 1928, Basin and Range structure and stratigraphy of 

the Warner Range, northeastern California: University of 

California Publications in Geological Sciences, v. 17, no. 11, 

p. 387^96.

Scott, E.W., 1983, Petroleum potential of wilderness lands in 

California, in Miller, B.M., ed., Petroleum potential of wilderness lands in the western United States: U.S. Geological 

Survey Circular 902-A-P, p. D1-D12.

Slosson, J.E., 1974, Surprise Valley Fault: California Division of 

Mines and Geology, California Geology, v. 27, p. 267-270.

Tunnel, George, 1972, Mercury, in Wedepohl, K.H., ed., Handbook of Geochemistry, Berlin, Springer-Verlag, v. 2, chapter 

80, p. F3-20.

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.

Woods, M.C.,1974, Geothermal activity in Surprise Valley: California Division of Mines and Geology, California Geology, v. 

27, p. 271-273.

Mineral Resources of the South Warner Contiguous Wilderness Study Area, California F17

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.

Z

UJ

9LU

on

LU 

LU

A

U/A

UNKNOWN POTENTIAL

B

H/B

HIGH POTENTIAL

M/B

MODERATE POTENTIAL

L7B

LOW POTENTIAL

C

H/C

HIGH POTENTIAL

M/C

MODERATE POTENTIAL

HC

LOW POTENTIAL

D

H/D

HIGH POTENTIAL

M/D

MODERATE POTENTIAL

L7D

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.

F20 Mineral Resources of Wilderness Study Areas: Northeastern California and Washoe County, Nevada
RESOURCE/RESERVE CLASSIFICATION

ECONOMIC

MARGINALLY 

ECONOMIC

SUBECONOMIC

IDENTIFIED RESOURCES

Demonstrated

Measured

Rese

Indicated

jrves

Marginal 

Reserves

Demonstrated 

Subeconomic

Resources

i

Inferred

Inferred 

Reserves

Inferred 

Marginal 

Reserves

Inferred 

Subeconomic 

Resources

UNDISCOVERED RESOURCES

Probability Range

Hypothetical Speculative

1

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 South Warner Contiguous Wilderness Study Area, California F21
GEOLOGIC TIME CHART

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

EON

Phanerozoic

Proterozoic

pre-Archean2

ERA

Cenozoic

Mesozoic

Paleozoic

Late Proterozoic

Middle Proterozoic

Early Proterozoic

Late Archean

Middle Archean

Early Archean

PERIOD

Neogene

Subperiod

Tertiary

Paleogene

Jurassic

Triassic

Permian

Pennsylvanian 

Carboniferous

Mississippian

Devonian

Silurian

Ordovician

Cambrian

__________ ttflOO?}- -

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

1A

 10

55

 66

yo

i ta

1f\C

r/MD

£*J\J

 -330

-IbU

 410

 435

 500

 '-570

IbUU

 2500

J\J\J\J

 J"tW

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

informal time term without specific rank.

F22 Mineral Resources of Wilderness Study Areas: Northeastern California and Washoe County, Nevada
Mineral Resources of Wilderness Study Areas: 

Northeastern California and Part of Adjacent 

Washoe County, Nevada

This volume was published as separate chapters A-F

U.S. GEOLOGICAL SURVEY BULLETIN 1706
DEPARTMENT OF THE INTERIOR 

MANUEL LUJAN, JR., Secretary

U.S. GEOLOGICAL SURVEY 

Dallas L. Peck, Director
CONTENTS

[Letters designate the separately published chapters]

(A) Mineral Resources of the Twin Peaks Wilderness Study Area, Washoe County, 

Nevada, and Lassen County, California, by Thomas L. Vercoutere, 

Martin L. Sorensen, James G. Frisken, Donald Plouff, and Michael S. Miller.

(B) Mineral Resources of the Tunnison Mountain Wilderness Study Area, Lassen 

County, California, by Jocellyn A. Peterson, James G. Frisken, Donald Plouff, 

Carolyn A. Goeldner, and Steven R. Munts.

(C) Mineral Resources of the Skedaddle Mountain Wilderness Study Area, Lassen 

County, California, and Washoe County, Nevada, by Michael F. Diggles, 

James G. Frisken, Donald Plouff, Steven R. Munts, and Thomas J. Peters.

(D) Mineral Resources of the Dry Valley Rim Wilderness Study Area, Washoe 

County, Nevada, and Lassen County, California, by Michael F. Diggles, 

James G. Frisken, Donald Plouff, and J. Mitchell Linne.

(E) Mineral Resources of the Pit River Canyon Wilderness Study Area, Lassen 

County, California, by Maureen G. Sherlock, and Harry W. Campbell.

(F) Mineral Resources of the South Warner Contiguous Wilderness Study Area, 

Modoc County, California, by Michael G. Sawlan, James G. Frisken, and 

Michael S. Miller.

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