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Denver,

CASA DIABLO G-E-M

RESOURCES AREA
(GRA NO. CA-06)
TECHNICAL REPORT
(WSA CA 010-082)

Contract YA-553-RFP2-1054

BLM Lib* a*? _ft

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Prepared By

Great Basin GEM Joint Venture
251 Ralston Street
Reno, Nevada 89503

For

Bureau of Land Management
Denver Service Center
Building 50, Mailroom
Denver Federal Center
Denver, Colorado 80225

I

Final Report
April 22, 1983

TABLE OF CONTENTS

Page
EXECUTIVE SUMMARY 1

I . INTRODUCTION 2

II . GEOLOGY 9

1 . PHYSIOGRAPHY 9

2. ROCK UNITS 10

3 . STRUCTURAL GEOLOGY AND TECTONICS 10

4 . PALEONTOLOGY 11

5 . HISTORICAL GEOLOGY H

III . ENERGY AND MINERAL RESOURCES 12

A. METALLIC MINERAL RESOURCES 12

1 . Known Mineral Deposits 12

2. Known Prospects, Mineral Occurrences and
Mineralized Areas 12

3 . Mining Claims 12

4. Mineral Deposit Types 13

5 . Mineral Economics 13

B . NONMETALLIC MINERAL RESOURCES 15

1 . Known Mineral Deposits 15

2. Known Prospects, Mineral Occurrences and
Mineralized Areas 15

3. Mining Claims, Leases and Material Sites 15

4. Mineral Deposit Types 15

5 . Mineral Economics 16

Table of Contents cont.

Page

C. ENERGY RESOURCES 17

Uranium and Thorium Resources 17

1 . Known Mineral Deposits 17

2. Known Prospects, Mineral Occurrences and
Mineralized Areas 17

3 . Mining Claims 17

4 . Mineral Deposit Types 17

5 . Mineral Economics 18

Oil and Gas Resources 19

Geothermal Resources 19

1 . Known Geothermal Deposits 19

2. Known Prospects, Geothermal Occurrences, and
Geothermal Areas 19

3 . Geothermal Leases 20

4. Geothermal Deposit Types 20

5. Geothermal Economics 20

D. OTHER GEOLOGICAL RESOURCES 21

E. STRATEGIC AND CRITICAL MINERALS AND METALS 21

IV. LAND CLASSIFICATION FOR G-E-M RESOURCES POTENTIAL ... 22

1 . LOCATABLE RESOURCES 23

a . Metallic Minerals 23

b . Uranium and Thorium 23

c. Nonmetallic Minerals 24

Table of Contents cont .

«

Page

2 . LEASABLE RESOURCES 24

a. Oil and Gas 24

b . Geothermal 24

c. Sodium and Potassium 25

3 . SALEABLE RESOURCES 25

V. RECOMMENDATIONS FOR ADDITIONAL WORK 26

VI . REFERENCES AND SELECTED BIBLIOGRAPHY 27

Table of Contents cont.

Page

LIST OF ILLUSTRATIONS

Figure 1 Index Map of Region 3 showing the

Location of the GRA 4

Figure 2 Topographic map of GRA, scale 1:250,000 5

Figure 3 Geologic map of GRA, scale 1:250,000 6

ATTACHMENTS
(At End of Report)

CLAIM AND LEASE MAPS

Patented/Unpatented

Geothermal

0 MINERAL OCCURRENCE AND LAND CLASSIFICATION MAPS (Attached)

Metallic Minerals
Uranium and Thorium
Nonmetallic Minerals
Geothermal

LEVEL OF CONFIDENCE SCHEME

CLASSIFICATION SCHEME

MAJOR STRATIGRAPHIC AND TIME DIVISIONS IN USE BY THE U.S.
GEOLOGICAL SURVEY

EXECUTIVE SUMMARY

The Casa Diablo Geology-Energy-Minerals (GEM) Resource Area (GRA)
is about ten miles north of Bishop, in Mono County, California,
covering the south end of the Benton Mountains and part of the
"volcanic tablelands". There is one Wilderness Study Area (WSA)
in it: CA 010-082.

In a small part of the GRA and a small part of the WSA
metamorphosed sedimentary rocks 200 million to 500 million years
old are exposed, together with granitic rocks intruded into them
about 100 million years ago. The remainder of the GRA and the WSA
are covered by volcanic ash rocks erupted a few hundred thousand
years ago, with some areas of very recent sand and gravels.

Part of the Chidago mining district lies in the northwestern
corner of this GRA. Two mines within the GRA have produced about
$100,000 in precious and base metals, while the district as a
whole has produced about $1 million in precious and base metals,
as well as at least 250,000 tons of tungsten ore averaging 0.5%
WO3 . Tungsten is a critical metal.

There are no patented mining claims in the GRA, and only a few
dozen unpatented claims. Most of the unpatented claims are a mile
or two west or north of WSA CA 010-082, but the W 1/2 Sec. 35, T 3
S, R 31 E, within the WSA, has unpatented claims. All of these
claims are probably on precious and metal-base metal occurrences
similar to those that have been mined. In the northeast corner of
the GRA there are claims that probably cover occurrences of a
fine, silty material that has been produced in the past as a
filler for specialty asphaltic mixes.

There are no oil and gas, geothermal, or sodium or potassium
leases in the GRA.

WSA CA 010-082 is classified throughout as moderately favorable
for metallic mineral resources, with a moderate level of
confidence. It is classified throughout as having low
favorability for both uranium/ thorium and nonmetallic minerals,
with low confidence. It is classified as having moderate
favorability for geothermal resources, with a low level of
confidence. There is very low favorability with high confidence
for oil and gas and for sodium and potassium resources.

Field work is recommended to determine whether there is alteration
in the rocks of WSA CA 010-082 that might indicate metallic
mineral resources, and to map alteration if it is present.

I. INTRODUCTION

The Casa Diablo G-E-M Resources Area (GRA No. CA-06) contains
approximately 102,000 acres (412 sq km) and includes the following
Wilderness Study Area (WSA) :

WSA Name WSA Number

Casa Diablo 010-082

The GRA is located in California in the Bureau of Land
Management's (BLM) Bishop Resource Area, Bakersfield district.
Figure 1 is an index map showing the location of the GRA. The
area encompassed is near 37°35" north latitude, 118°30' west
longitude and includes the following townships:

T 4 S, R 31,32 E T 5 S, R 31,32 E

The areas of the WSA are on the following U. S. Geological Survey
topographic map:

15-minute:

Casa Diablo

The nearest town is Bishop which is located approximately 10 miles
southeast of the GRA. Access to the area is via U.S. 6 to the
east, Watterson Canyon road to the west, and U.S. 395 to the
southwest. Access within the area is along various paved and
unimproved roads such as Red Rock Canyon and Fish Slough Roads.

Figure 2 outlines the boundaries of the GRA and the WSA on a
topographic base at a scale of 1:250,000.

Figure 3 is a geologic map of the GRA and vicinity, also at
1:250,000. At the end of the report, following the Land
Classification Maps, is a geologic time scale showing the various
geologic eras, periods and epochs by name as they are used in the
text, with the corresponding age in years. This is so that the
reader who is not familiar with geologic time subdivisions will
have a comprehensive reference for the geochronology of events.

This GRA Report is one of fifty-five reports on the Geology-
Energy-Minerals potential of Wilderness Study Areas in the Basin
and Range Province, prepared for the Bureau of Land Management by
the Great Basin GEM Joint Venture.

The principals of the Venture are Arthur Baker III, G. Martin

Booth III, and Dennis P. Bryan. The study is principally a
literature search supplemented by information provided by claim
owners, other individuals with knowledge of some areas, and both
specific and general experience of the authors. Brief field
verification work was conducted on approximately 25 percent of the
WSAs covered by the study.

The WSA in this GRA was not field checked.

One original copy of background data specifically applicable to
this GEM Resource Area Report has been provided to the BLM as the
GRA File. In the GRA File are items such as letters from or notes
on telephone conversations with claim owners in the GRA or the
WSA, plots of areas of Land Classification for Mineral Resources
on maps at larger scale than those that accompany this report if
such were made, original compilations of mining claim
distribution, any copies of journal articles or other documents
that were acquired during the research, and other notes as are
deemed applicable by the authors.

As a part of the contract that resulted in this report, a
background document was also written: Geological Environments of
Energy and Mineral Resources. A copy of this document is included
with the GRA File to this GRA report. There are some geological
environments that are known to be favorable for certain kinds of
mineral deposits, while other environments are known to be much
less favorable. In many instances conclusions as to the
favorability of areas for the accumulation of mineral resources,
drawn in these GRA Reports, have been influenced by the geology of
the areas, regardless of whether occurrences of valuable minerals
are known to be present. This document is provided to give the
reader some understanding of at least the most important aspects
of geological environments that were in the minds of the authors
when they wrote these reports.

i

Figure 1. GRA Index Hap of Region 3 1:3,168,000.

Mariposa Sheet

Casa Diablo GRA CA-06
Figure 2

m W\ KIP

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ass i v mmm «»

ogic Map llflPflSilf ! Sp^M

:25o,ooo mmmm mm

See next page for explanation ^^^%1^ fll

Geoli

1:250,000

Mariposa Sheet, Strand (1967)

Casa Diablo GRA CA-06
Figure 3

EXPLANATION

SEDIMENTARY AND METASEDI MENTAR Y ROCKS

IGNEOUS AND META-IGNEOUS ROCKS

Qs Dune sand

Qai Alluvium

Osc

oc

Stream channel
deposits

Fan deposits
Basin deposits

Oc,

Recent volcanic: Orvr — rhyolite;
Gr,° — andesite; Qm" —basalt:
Qrv" —pyroclastic rocks

Ost Salt deposits

01 Quaternary lake deposits

09 Glacial deposits

Gm

m

Quaternary nonmarinc
terrace deposits

Pleistocene marine and
marine terrace deposits

Pleistocene nonmarine

Oov

Pleistocene volcanic: Oov —rhyolite:
Cpv=-andesite; Qpv° —basalt;
0pvp —pyroclastic rocks

QP Plio-Pleistocene nonmarine

~5.i/^

7/r?

Quaternary and/or Pliocene
cinder cones

*

Pc Undivided Pliocene nonmarine

Poc Upper Pliocene nonmarine

Pu

Upper Pliocene marine

Middle and/or lower Pliocene
nonmarine

Pliocene volcanic: Pv' -rhyolite;
P;°— andesite; p ° —basalt;
Pv° —pyroclastic rocks

pmi [ Middle and/or lower Pliocene marine

Mc Undivided Miocene nonmarine

Muc Upper Miocene nonmarine

Upper Miocene marine

Mmc Middle Miocene nonmarine

~^~- 1 Miocene volcanic: Wvr —rhyolite;
Mv ] m.° -andesite; Mvb— basalt;
■ ■ -' MvD —pyroclastic rocks

Mm Middle Miocene marine

J

: S

»

2

mi Lower Miocene marine

©c I Oligocene nonmarine

© Oligocene marine

Ec Eocene nonmarine

E Eocene marine

".'.'■] Oligocene volcanic: ©v'— rhyolite:
Dv- J (Dv° —andesite : ejv6— basalt;
' "' i ©v» — pyroclastic rocks

j Eocene volcanic: £v' -rhyolite;

"■ | Ev° andcsitoiEv0 -basalt :

Ev° —pyroclastic rock?

Epc I Paleocene nonmarine

I

£p Paleocone marine

i <

Paleocene marine

Cenozoic nonmanne
I Tc Tertiary nonmarine

I ' Tertiary lake deposits

■ HIM I

u.lir Tertiary marine

EXPLANATION CONT

— ■ •- ■ Cenozoic v

6" QTv'--and

-*- QT„C -pyr

~t' Ternary granitic rocks

Cenozoic volcanic: c". —rhyolite:
andesite: qtvi- —basalt;
pyroclastic rocks

Undivided Cretaceous marine

Upper Cretaceous
marine

Lower Cretaceous
marine

ED

Knoxvillc Formation

Upper Jurassic
marine

Middle and/or Lower
Jurassic marine

Triassic marine

7.

o

ED

Pre-Cretaceous metamorphic
rocks (Is - limestone or dolomite)

Pre-Cretaceous metasedimentary
rocks

■ Paleozoic marine
Is I (Is = limestone or dolomite

ft Permian marine

C Undivided Carboniferous marine

Tertiary intrusive (hypabyssab
rocks Ti'- rhyolite; Ti° -andesite;
TiB -basalt

Tertiary volcanic: TV —rhyolite;
T,° —andesite; *v° —basalt:
tvd —pyroclastic rocks

Franciscan volcanic and
metavolcanic rocks

Me-ozoic granitic rocks : <Jr°-irranite
and adamellite:<J',-Kranodiorm;
9' ' -tonalite and dioritc

Mesozoic basic intrusive
rocks

Mesozoic ultrabasic
intrusive rocks

Jura-Trias metavolcanic rocks

Pre-Cretaceous metavolcanic
rocks

Pre-Cenozoic granitic and
metamorphic rocks

Paleozoic metavolcanic rocks

Sv Permian metavolcanic rocks

Cv Carboniferous metavolcanic rocks

CP Pennsylvanian marine

CM Mississippian marine

]

Devonian marine

Silurian marine

Pre-Silurian meta-
sedimentary rocks

Ordovician marine
Cambrian marine

Cambrian — Precambrian marine

1 Undivided Precambrian

PC metamorphic rocks
' cCq = gneiss, oCs = schist

Ov

Devonian metavolcanic rocks

0v? | Devonian and pre-Devonian?
metavolcanic rocks

Pre-Silurian

metamorphic "Sv
rocks '

Pre-Silurian
metavolcanic
rocks

GEJ

Precambrian igneous and
metamorphic rock complex

Undivided Precambrian
granitic rocks

Pt

Later Precambrian sedimentary
an^l metamorphic rocks

Earlier Precambrian metamorphir

oC 3n , Precambrian anorthositi

*

II. GEOLOGY

The Casa Diablo GRA in southern Mono County is situated within a
large graben on the western edge of the Basin and Range Province.
The northwestern portion of the study area is the southern end of
the Benton Range, a relatively uplifted block of Paleozoic
metamorphic rocks and Cretaceous intrusives. The remainder of the
area is predominantly volcanic tablelands formed by the deposition
of the Quaternary Bishop Tuff.

Northwest trending Pliocene Basin and Range faults have produced
the generally moderate topography especially in the Benton Range.
Recent fault activity is evidenced by smaller displacements in the
Bishop Tuff and recent alluvial deposits.

1. PHYSIOGRAPHY

The Casa Diablo GRA, located in southern Mono County, is on
the western edge of the Basin and Range Province near the
Sierra Nevada Province border. It lies within a large graben
bounded by the White Mountains to the east and the Sierra
Nevadas to the west. The study area contains the southern
portion of the north-south-trending, relatively uplifted,
Benton Range and the gently south-sloping "volcanic
tablelands" in the south (Rinehart and Ross, 1957).

The topography of much of the area is moderate with altitudes
ranging from 4500 feet in Hammil Valley on the east to about
7900 feet at the peak of Casa Diablo Mountain.

Chidago Canyon in the north and the Owens River Gorge in the
southwest have been cut into the Quaternary Bishop Tuff.

There are no year round flowing streams in the study area.
The Owens River in the southwest portion of the GRA is
periodically dry below the dam at Crowley Lake to the
northwest due to the diversion of water to power plants of the
Los Angeles Department of Water and Power. Two of these power
plants are located in the Owens River Gorge in the southwest
portion of the study area.

Late Pliocene Basin and Range faulting is responsible for much
of the present topography in the northwest portion of the
study area. The remainder of the surface is a gently sloping
volcanic terrane formed by the deposition of the Bishop Tuff.
Since the extrusion of the Bishop Tuff, recent fault activity
has modified the landscape to a minor degree. Fault scarps
are abundant in the Bishop Tuff and have an average throw of
100 feet.

*

i

2. ROCK UNITS

The oldest rocks in the study area are upper Precambrian or
lower Paleozoic marine sediments in the Benton Range which
have been metamorphosed by Cretaceous intrusions to biotite-
quartz hornfels, quartz-mica phyllite and quartz-sericite
hornfels (Rinehart and Ross, 1957). The sediments are the
hosts for tungsten deposits and some gold veins in the area.

Small bodies of diorite-gabbro were emplaced in the early
Cretaceous followed by the intrusion of the Benton Range
granodiorite, the Wheeler Crest quartz monzonite, the Casa
Diablo granite and isolated bodies of alaskite (Rinehart and
Ross, 1957). These intrusive bodies provided the mineralizing
solutions that formed base and precious metal deposits.

A swarm of porphyritic rhyolite and aplite dikes sills, and
small masses related to the cooling intrusions were emplaced
along regional northwest trending structures during the late
Cretaceous .

The next oldest formation in the study area is an unnamed flow
of Tertiary basalt which crops out in patches in the northwest
and along the Owens River Gorge (Putnam, 1952).

The Bishop Tuff, deposited during the Pleistocene, is the
youngest volcanic sequence in the area and covers a
predominant portion of the surface area (Dalrymple and
others, 1965). Where thick vertical sections are exposed, it
is possible to subdivide the tuff into five units based on
compaction, color and columnar jointing. Pumiceous units have
been mined for pumice.

3. STRUCTURAL GEOLOGY AND TECTONICS

The oldest structures preserved in the study area are pre-
batholith folds and faults in the Paleozoic metamorphic rocks
of the Benton Range. This deformation occurred during a
period of regional compression which probably took place
during the Triassic.

Most of the Benton Range is bounded by large north-northwest-
trending Pliocene Basin and Range faults. Movement along
these faults is still occurring as shown by local
displacements of the Quaternary Bishop Tuff along their trend
(Rinehart and others, 1956).

The more recent faults that are prominent in the Bishop Tuff
trend north and are mostly downthrown to the west. The
average throw of these faults is less than 100 feet. These
faults are similar in trend and direction of movement to most
of the older faults in the Benton Range, and may represent
renewed movement along pre-Tertiary faults in the underlying
basement rocks.

10

»

4. PALEONTOLOGY

The Casa Diablo GRA covers a terrane of predominantly
Pleistocene pyroclastics of the Bishop tuff, with small areas
of metamorphosed sediments, Mesozoic granitic rocks and
Quaternary alluvium, gravels, and dune sands. Fossils are not
to be expected in any of these units.

5. HISTORICAL GEOLOGY

During the late Precambrian or early Paleozoic, sequences of
marine clastic and carbonate rocks were deposited. These
sediments were folded and faulted by regional compressional
forces during the Triassic.

Intrusive bodies of diorite and granitic plutons related to
the Sierra Nevada batholith were emplaced during the
Cretaceous, metamorphosing the sediments to phyllites and
hornfels and introducing mineralizing solutions that formed
tungsten and gold deposits.

During the late Cretaceous swarms of aplite and rhyolite dikes
were intruded along north-northwest zones of weakness.

Volcanism began during the Tertiary with the extrusion of
basalt flows in the area. Basin and Range faulting began
after the extrusion of the basalt during the late Pliocene.
This faulting has been more or less continuous but on a
smaller scale to the present.

A period of erosion is evidenced by the irregular low relief
surface on which the Bishop Tuff was deposited during the
Quaternary. The Bishop Tuff has numerous small fault
displacements from recent tectonic activity (Dalrymple and
others, 1965), and pumice has been produced from it.

11

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fr

III. ENERGY AND MINERAL RESOURCES

A. METALLIC MINERAL RESOURCES

1. Known Mineral Deposits

The northwestern quarter of the Casa Diablo GRA covers the
southern end of the Chidago mining district. The district
consists of a dozen or more productive mines rather widely
scattered over T 3 S, R 31 E, and T 4 S, R 31 E. Rinehart
and Ross (1956) estimate total precious metal production
of the district as probably less than $1,000,000, while
the Black Rock mine, three miles north of the GRA,
produced at least 275,000 tons of tungsten ore averaging
about 0.5% W03 . Tungsten is a strategic and critical
metal.

Within the GRA are the Casa Diablo mine (Sec. 21, T 4 S, R
31 E), credited with something over $100,000 in gold,
silver and base metals, and the Beckman mine (Sec. 2, T 4
S, R 31 E) with somewhat less than $100,000 in the same
metals .

2. Known Prospects, Mineral Occurrences and Mineralized Areas

Rinehart and Ross (1956) show a dozen prospect pits and
shafts in an irregular line extending two miles south from
the Casa Diablo mine, half a mile west of WSA 010-082. No
information is available as to their nature, but since
they are in the same granitic body as the Casa Diablo mine
they probably are on similar occurrences of gold-silver-
base metal veins.

Near the Beckman mine are a couple of prospects, one
labelled the Chance mine by Rinehart and Ross (1956) and
indicated as having produced some lead and silver.

Near the west edge of Sec. 2, T 5 S, R 31 E on the Casa
Diablo Mountain topographic quadrangle, is a prospect
symbol within the WSA. In and near the northwest corner
of Sec. 14, T 4 S, R 32 E are prospect and adit symbols,
one of which may be within the WSA. All of these are in
granitic rocks and are probably on quartz veins similar to
those of the Casa Diablo mine.

3. Mining Claims

No patented claims were found in the GRA in our search of
the BLM records, but Tucker (1927) refers to two patented
claims at the Casa Diablo mine.

12

$

There are several dozen unpatented mining claims in the
GRA. Most of them are in the vicinity of the known
prospects — near the Beckman mine and near and south of
the Casa Diablo mine. There are claims in the western
one-half of Sec. 35, T 4 S, R 31 E, within WSA 010-082;
these are in an area underlain by the granite of the Casa
Diablo mine and probably are on occurrences of similar
mineralization .

4. Mineral Deposit Types

The two mines and the several scattered prospects in the
pre-Tertiary terrane are quartz veins that contain
precious and base metals. They are mesothermal, formed
during the final stages of the Mesozoic intrusive
activity. All descriptions indicate that they are narrow
and that the ore shoots in them are small.

No tungsten occurrences are known in the Casa Diablo GRA,
but the important Black Rock tungsten mine lies only a few
miles north of the GRA. The Black Rock deposit is
pyrometasomatic, scheelite-bearing tactite body in
metasediments of Paleozoic(?) age that have been intruded
by several bodies of generally granitic rocks of Mesozoic
age. Most of the same granitic rocks are exposed in the
small area of pre-Tertiary rocks in the northwest part of
the Casa Diablo GRA, and some metasediments also are
exposed although none of them are of the calcareous unit
that hosts the Black Rock deposit.

5. Mineral Economics

The mesothermal quartz veins with base and precious metals
are so narrow and have such small ore shoots that they do
not make attractive targets for most mining companies, but
during times of high metal prices may be mined by small
companies or individuals.

There is nothing to indicate the presence of tungsten
deposits in the GRA close enough to the surface to be
mined open-pit as the Black Rock deposit was. However,
such a deposit probably could be mined underground, given
high grade and a good tungsten price. If any such
deposits are found under the Tertiary and Quaternary
volcanic cover, they may be worth mining.

More than half of all tungsten used is in the form of
tungsten carbide, a hard and durable material used in
cutting tools, wear-resistant surfaces and hard-faced
welding rods. Lesser quantities are used in alloy steels,
in light bulb filaments, and in chemicals. World
production of tungsten is nearly 100 million pounds
annually, of which the United States produces somewhat

13

f

more than six million pounds, while using more than 21
million pounds. The shortfall is imported from Canada,
Bolivia, Thailand and Mainland China, as well as other
countries. Tungsten is a strategic and critical metal.
United States demand is projected to about double by the
year 2000, and most of the additional supply will probably
be imported, because large reserves are in countries in
which profitability is not a factor — they need foreign
exchange, and therefore sell at a price that few domestic
mines can match. Tungsten prices F.O.B. mine are quoted
for "short ton units", which are the equivalent of 20
pounds of contained tungsten. At the end of 1982 the
price of tungsten was about $80 per short ton unit.

The major use of gold is for storing wealth. It is no
longer used for coinage because of monetary problems, but
many gold "coins" are struck each year for sale simply as
known quantities of gold that the buyer can keep or
dispose of relatively easily. The greatest other use of
gold is in jewelry, another form of stored wealth. In
recent years industrial applications have become
increasingly important, especially as a conductor in
electronic instrumentation. In the United States and some
other countries gold is measured in troy ounces that weigh
31.1 grams — twelve of which make one troy pound. Annual
world production is about 40 million ounces per year, of
which the United States produces somewhat more than one
million ounces, less than one-fourth of its consumption,
while the Republic of South Africa is by far the largest
producer at more than 20 million ounces per year. World
production is expected to increase through the 1980s. For
many years the price was fixed by the United States at $3 5
per ounce, but after deregulation the price rose to a high
of more than $800 per ounce and then dropped to the
neighborhood of $400 per ounce. At the end of 1982 the
price was $460.50 per ounce.

The major uses of silver are in photographic film,
sterlingware, and increasingly in electrical contacts and
conductors. It is also widely used for storage of wealth
in the form of jewelry, "coins" or bullion. Like gold it
is commonly measured in troy ounces, which weigh 31.1
grand grams, twelve of which make one troy pound. World
production is about 350 million ounces per year, of which
the United States produces about one-tenth, while it uses
more than one-third of world production. About two-thirds
of all silver is produced as a byproduct in the mining of
other metals, so the supply cannot readily adjust to
demand. It is a strategic metal. Demand is expected to
increase in the next decades because of growing industrial
use. At the end of 1982 the price of silver was $11.70
per ounce.

The largest use for lead is in electrical storage

14

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batteries, the second being a gasoline antiknock additive.
It has many other uses, however, including radiation
shielding, solders, numerous chemical applications, and in
construction. About four million metric tons of lead are
produced in the world annually. The United States
produces about half a million tons per year, and recovers
about the same amount from scrap — much of it through the
recycling of old batteries. It imports about one-quarter
of a million tons. Lead is classified as a strategic
minerals. Demand is projected to increase somewhat in the
next couple of decades, but environmental concerns will
limit the increase. The United States has large ore
reserves that are expected to last well beyond the end of
this century at current production rates even without
major new discoveries. At the end of 1982 the price was
about 22 cents per pound.

B. NONMETALLIC MINERAL RESOURCES

1. Known Mineral Deposits

In the southwestern half of Sec. 12, T 4 S, R 32 E, at the
extreme eastern edge of the GRA, on the White Mountain
Peak 15-minute topographic quadrangle is a quarry symbol
labelled Sandpit. Since the late 1950* s fine silt, that
is predominantly the mineral pyrophyllite, has been mined
here. It is air separated to mostly minus 325 mesh and
shipped, under the trade name Siltex, to the Los Angeles
area as a filler in specialty asphalt mixes (A. Baker III,
personal communication.)

2. Known Prospects, Mineral Occurrences and Mineralized Areas

In the northwest 1/4 of Sec. 10, T 4 S, R 31 E Rinehart
and Ross (1956) show a quarry symbol indicated as being in
pumice. Rather suprisingly, considering the large
expanses of Bishop tuff exposed in the GRA, there seem to
be no other pumice pits.

3. Mining Claims, Leases and Material Sites

In the northeast corner of the GRA are a number of claims,
and it appears that much of Sec. 13, T 4 S, R 32 E is
claimed. This is the vicinity of the Siltex mine and the
claims may well be located to cover the known area of this
material .

4. Mineral Deposit Types

The Siltex deposit near the east border of the GRA

15

I

t

displays some bedding, and probably is a lakebed deposited
in an ephemeral lake that once occupied Hammil Valley. It
can be considered a clay. The operators of the deposit
believe that most of the material is finely-divided
pyrophyllite eroded from the canyons in the White
Mountains a very few miles to the east; the geography fits
with this interpretation.

One pumice quarry is known in the GRA, in Sec, 10, T 4 S,
R 31 E. The apparent lack of them elsewhere in the GRA,
despite the fact that they are common in the general
region, suggests that this part of the Bishop tuff is not
favorable for pumice deposits.

5. Mineral Economics

The Siltex deposit evidently is one of the rather special
industrial mineral deposits in the region that can stand
the high transportation cost to the Los Angeles market,
since it has been mined for at least twenty years.

There are several major varieties of clay, differing both
in their mineralogy and their uses, and some materials
that mineralogically are clay are called by other names,
while some that technically are not clay are called clay.
Large amounts of white clay (kaolin) are used as filler in
paper to produce the glossy sheen of magazine pages. Even
larger quantities of common clay are used in making
bricks, drain tile, and other construction products.
Certain clays are used extensively in ceramics and in
refractory materials. Minor uses include drilling muds,
foundry sands, purifying materials for oils, and a great
many more. The United States uses about 50 million tons
of clays annually, nearly all of it produced domestically.
Consumption is forecast to about double by the year 2000,
with production increasing in amount the same proportion.
The price of clay varies widely depending on the kind of
material: the average price is a little lower than $20
per ton, but common clay is valued at about $5 per ton
while the highest-priced clay, kaolin, averages about $65
per ton.

For statistical purposes pumice, volcanic cinder and
scoria are treated together because in most applications
they are interchangeable; the word "pumice" as used here
includes the other materials. Because of its porous
nature and resultant light weight (some pumice will float
on water) about 40% of all pumice production is used as
aggregate in making light-weight concrete for construction
purposes. An equal amount is used as aggregate in road
construction. A small amount is used in abrasives, while
the remainder is used, mostly in finely-ground form, in a
multitude of applications such as absorbents, carriers for
insecticides, decolorizers and purifying agents, fillers

16

and extenders for paints, and many others. United States
consumption is about 4.5 million short tons annually,
nearly all of which is produced domestically and most of
which is produced within a very few hundred miles of the
point of use because it is a high-volume, low-unit-price
material. A small quantity of pumice for specialized uses
is imported. United States demand for pumice is forecast
to more than double by the year 2000, with domestic
production keeping up with demand. In recent years the
F.O.B. mine price for pumice as such has been about $4 per
ton, while the price for the somewhat more common volcanic
cinders has been about $3 per ton.

C. ENERGY RESOURCES

Uranium and Thorium Resources

1. Known Mineral Deposits

There are no known uranium or thorium deposits within or
near the WSA or the GRA.

2. Known Prospects, Mineral Occurrences and Mineralized Areas

Radioactive occurrences are indicated on the Land
Classification and Mineral Occurrence Map included at the
back of the report.

There are no known uranium or thorium prospects or
occurrences within the WSA or the GRA. There are two
uranium occurrences north of the GRA though no production
has been recorded from these occurrences. Uranium is
associated with a quartz monzonite intrusion at the Banner
gold mine in Sec. 18, T 3 S, R 31 E and there is an
undescribed uranium occurrence at the Claw claim in T 2 S,
R 33 E on the west flank of the White Mountains (Minobras,
1978).

3. Mining Claims

There are no known uranium or thorium claims or leases
within the WSA or the GRA.

4. Mineral Deposit Types

The lack of known occurrences of uranium and thorium in
the area prevents a determination of the deposit types.

17

*

«-

5. Mineral Economics

Uranium and thorium would appear to be of little economic
importance within the WSA and the GRA as there are no
known occurrences of these minerals in the area.

Uranium in its enriched form is used primarily as fuel for
nuclear reactors, with lesser amounts being used in the
manufacture of atomic weapons and materials which are used
for medical radiation treatments. Annual western world
production of uranium concentrates totaled approximately
57,000 tons in 1981, and the United States was responsible
for about 30 percent of this total, making the United
States the largest single producer of uranium (American
Bureau of Metal Statistics, 1982). The United States
ranks second behind Australia in uranium resources based
on a production cost of $25/pound or less. United States
uranium demand is growing at a much slower rate than was
forecast in the late 1970s, because the number of new
reactors scheduled for construction has declined sharply
since the accident at the Three Mile Island Nuclear Plant
in March, 1979. Current and future supplies were seen to
exceed future demand by a significant margin and spot
prices of uranium fell from $40/pound to $25/pound from
January, 1980 to January, 1981 (Mining Journal, July 24,
1981). At present the outlook for the United States
uranium industry is bleak. Low prices and overproduction
in the industry have resulted in the closures of numerous
uranium mines and mills and reduced production at
properties which have remained in operation. The price of
uranium at the end of 1982 was $19.75/pound of
concentrate. Uranium and thorium would appear to be of
little economic importance within the WSA and the GRA as
there are no known occurrences of these minerals in the
area.

Thorium is used in the manufacture of incandescent gas
mantles, welding rods, refractories, as fuel for nuclear
power reactors and as an alloying agent. The principal
source of thorium is monazite which is recovered as a
byproduct of titanium, zirconium and rare earth recovery
from beach sands. Although monazite is produced from
Florida beach sands, thorium products are not produced
from monazite in the United States. Consequently, thorium
products used in the United States come from imports,
primarily from France and Canada, and industry and
government stocks. Estimated United States consumption of
thorium in 1980 was 33 tons, most of which was used in
incandescent lamp mantles and refractories (Kirk, 1980b) .
Use of thorium as nuclear fuel is relatively small at
present, because only two commercial thorium- fueled
reactors are in operation. Annual United States demand
for thorium is projected at 155 tons by 2000 (Kirk,
1980a). Most of this growth is forecast to occur in
nuclear power reactor usage, assuming that six to ten

18

f

•

thorium-fueled reactors are on line by that time. The
^ United States and the rest of the world are in a favorable

position with regard to adequacy of thorium reserves. The
United States has reserves estimated at 218,000 tons of
Th02 in stream and beach placers, veins and carbonatite
deposits (Kirk, 1982); and probable cumulative demand in
the United States as of 2000 is estimated at only 1800
tons (Kirk, 1980b) . The price of thorium oxide at the end
of 1981 was $16.45 per pound.

Oil and Gas Resources

There are no oil and gas fields, hydrocarbon shows in wells,
or surface seeps in the region; nor are there any Federal oil
and gas leases in the immediate region. Intrusive and
extrusive igneous rocks are the predominant strata present; no
source rocks are present which would favor the generation of
petroleum.

There is no oil and gas lease map, nor is there an oil and gas
occurrence and classification map in the report.

Geothermal Resources

0 1. Known Geothermal Resources

There are no known geothermal deposits within the Casa
Diablo GRA.

2. Known Prospects, Geothermal Occurrences, and Geothermal
Areas

The Casa Diablo GRA has no recorded thermal springs or
wells, but is less than five miles southeast of the Long
Valley geothermal resource area which is a collapsed
caldera underlain by a slowly cooling magma that is
presumed to be the heat source for numerous surface
thermal manifestations such as springs and fumeroles.
Long Valley is known or inferred to be underlain at
shallow (less than 1,000 meters) by thermal water of
sufficient temperature for direct heat application. In
the eastern portion of the caldera, closest to the Casa
Diablo GRA, three unnamed spring areas have waters of 22°
to 53 °C (NOAA, 1980). These thermal manifestations are
shown on the Geothermal Occurrence and Land Classification
Map at the back of the report.

On structural trend 15 miles to the south of the GRA in
^ Owens Valley, 51 °C Keough Hot Spring flows at 2000 1/min.,

and unnamed springs on the opposite side of the valley are
29 °C (NOAA, 1980).

19

•

Geothermal Leases

The only recorded Federal geothermal leasing in the area
is a 40 square mile lease block on the eastern rim of the
Long Valley caldera. These leases share a six mile long
common boundary with the Casa Diablo GRA, and are
contiguous with the eastern edge of the Mono-Long Valley
KGRA (see Geothermal Lease Map).

4. Geothermal Deposit Types

There are no geothermal deposits within the Casa Diablo
area.

5. Geothermal Economics

Because there are no geothermal deposits or other thermal
manifestations within the GRA, there is no direct basis on
which to base consideration of the mineral economics.

Geothermal resources are utilized in the form of hot water
or steam normally captured by means of drilling wells to a
depth of a few feet to over 10,000 feet in depth. The
fluid temperature, sustained flow rate and water chemistry
characteristics of a geothermal reservoir determine the
depth to which it will be economically feasible to drill
and develop each site.

Higher temperature resources (above 350 °F) are currently
being used to generate electrical power in Utah and
California, and in a number of foreign countries. As fuel
costs rise and technology improves, the lower temperature
limit for power will decrease appreciably — especially
for remote sites.

All thermal waters can be beneficially used in some way,
including fish farming (68°F), warm water for year around
mining in cold climates (86°F), residential space heating
(122°F), greenhouses by space heating (176°F), drying of
vegetables (212°F), extraction of salts by evaporation and
crystallization (266°F), and drying of diatomaceous earth
(338°F) .

Unlike most mineral commodities remoteness of resource
location is not a drawback. Domestic and commercial use
of natural thermal springs and shallow wells in the Basin
and Range province is a historical fact for over 100
years .

Development and maintenance of a resource for beneficial
use may mean no dollars or hundreds of millions of
dollars, depending on the resource characteristics, the
end use and the intensity or level of use.

20

1 D. OTHER GEOLOGICAL RESOURCES

No other geological resources have been recognized in the GRA.

E. STRAGETIC AND CRITICAL MINERALS AND METALS

A list of strategic and critical minerals and metals provided
by the BLM was used as a guideline for the discussion of
strategic and critical materials in this report.

The Stockpile Report to the Congress, October 1981-March 1982/
states that the term "strategic and critical materials" refers
to materials that would be needed to supply the industrial,
military and essential civilian needs of the United States
during a national emergency and are not found or produced in
the United States in sufficient quantities to meet such need.
The report does not define a distinction between strategic and
critical minerals.

No strategic or critical minerals or metals are known in WSA
CA 010-082. There is some potential for tungsten, a strategic
metal, in the older rocks beneath the cover of Tertiary
volcanic rocks and Quaternary alluvium.

21

*

IV. LAND CLASSIFICATION FOR GEM RESOURCES POTENTIAL

The Rinehart and Ross (1957) geologic map at 1:62,500 covers much
of the GRA and all of the WSA. The geological data here is
excellent except that hydrothermal alteration, if it is present,
was not mapped. The Rinehart and Ross (1956) map provides
excellent information on the distribution and nature of mineral
occurrences . The eastern part of the GRA is covered by the
geologic map at 1:62,500 of Crowder and Sheridan (1972). This map
provides excellent coverage of rock types and structure; it is
unlikely that there is alteration in this area that has
significance in regard to metallic resources. Specifically with
respect to the WSA and its environs, the quantity of geologic
coverage is ample, the quality is moderate, and data concerning
mineral occurrences is good but background data such as alteration
and geochemistry are lacking. Overall, our confidence level in
the information available is high.

Land classification areas are numbered starting with the number 1
in each category of resources. Metallic mineral land
classification areas have the prefix M, e.g. M1-4D. Uranium and
thorium areas have the prefix U. Nonmetallic mineral areas have
the prefix N. Oil and gas areas have the prefix OG. Geothermal
areas have the prefix G. Sodium and potassium areas have the
prefix S. The saleable resources are classified under the
nonmetallic mineral resource section. Both the Classification
Scheme, numbers 1 through 4, and the Level of Confidence Scheme,
letters A, B, C and D, as supplied by the BLM are included as
attachments to this report. These schemes were used as strict
guidelines in developing the mineral classification areas used in
this report.

Land classifications have been made here only for the areas that
encompass segments of the WSA. Where data outside a WSA has been
used in establishing a classification area within a WSA, then at
least a part of the surrounding area may also be included for
clarification. The classified areas are shown on the 1:250,000
mylars or the prints of those that accompany each copy of this
report.

In connection with nonmetallic mineral classification, it should
be noted that in all instances areas mapped as alluvium are
classified as having moderate favorability for sand and gravel,
with moderate confidence, since alluvium is by definition sand and
gravel. All areas mapped as principally limestone or dolomite
have a similar classification since these rocks are usable for
cement or lime production. All areas mapped as other rock, if
they do not have specific reason for a different classification,
are classified as having low favorability, with low confidence,
for nonmetallic mineral potential, since any mineral material can
at least be used in construction applications.

22

»

1. LOCATABLE RESOURCES
a. Metallic Minerals
WSA CA 010-082

M1-3C. This classification area covers all of the WSA.
Its boundary is largely defined by gravimetrics . Pakiser,
and others, (1964, Plate 1, Sheet 1) show a gravity low
just west of the WSA, which probably indicates a block of
pre-Tertiary rocks that has been dropped too deep for
mineral exploration in the near future. To the south and
east, however, the gentle gravity slope indicates thin
cover by Tertiary rocks. Within a mile west and north of
the WSA are the productive Casa Diablo, Beckman and Chance
gold mines, and a dozen or more prospects. All of these
are in the intrusive rocks or metasediments that are the
hosts for other mines in the Chidago district, and that
underlie the WSA (Rinehart and Ross, 1956). The fact that
the rocks are known to be favorable hosts for metallic
minerals, and the presence of mines and prospects just
outside the WSA are the reasons for the moderate
favorability classification and the moderate level of
confidence.

b. Uranium and Thorium

WSA CA 010-082

U1-2B. This land classification indicating low uranium
and thorium favorability at a low level of confidence
covers the WSA and nearly the entire GRA. Most of the
area is covered by the Pleistocene Bishop Tuff.
Cretaceous granitic rocks crop out on the western side of
the WSA. Rhyolite and aplite dikes and sills and isolated
alaskites associated with the granitic intrusion may
extend into the WSA. All of the above igneous rocks are
prospective uranium source and host rocks with the uranium
most prospective as vein-type and fracture fill deposits,
and as concentrated primary mineralization in the
alaskites . There are no uranium or thorium occurrences
within the GRA or the WSA though there are two uranium
occurrences to the north, one of which is associated with
quartz monzonite (Banner gold mine). There are also two
aerial radiometric uranium anomalies on the east and west
borders of the GRA, south of the WSA (High Life
Helicopters, 1980).

Thorium is also prospective in the WSA as primary
mineralization in the Cretaceous alaskites (pegmatites)
though there are no known thorium occurrences in or near
the WSA or the GRA.

23

t

c. Nonmetallic Minerals

WSA CA 010-082

N1-2B. This classification area covers all of the WSA.
There are no nonmetallic occurrences in the WSA or close
to it (except one pumice occurrence a couple of miles
away. However, all rocks can be used as construction
materials, and any mineral material can become an economic
nonmetallic mineral if someone can develop a use for its
particular physical and chemical properties.

2. LEASABLE RESOURCES

a. Oil and Gas

WSA CA 010-082

0G1-1D. There has been no serious oil and gas
exploration, nor are there any recorded occurrences of oil
and gas in this westernmost sector of the Basin and Range
province where it meets the Sierra Nevadas . The
geological environment — intrusive and intruded rocks and
volcanics — is not favorable for oil and gas
accumulations .

b. Geothermal

WSA CA 010-082

G1-3B. While there is no direct evidence of a geothermal
resource, the entire GRA is on the eastern edge of the
east-west trending Long Valley caldera. Under this
collapsed structure there is a slowly cooling magma which
is believed to provide the heat for the high temperature
resource. Except for the core of Casa Diablo Mountain,
the entire GRA is underlain by an intricately faulted
Pleistocene volcanic tableland. This volcanic series
extends continuously westward, and is found throughout the
Long Valley elliptical structure. In addition, the
leasing pattern indicates support for this continuity
eastward to at least the western edge of the Casa Diablo
GRA. The nearby heat source and the numerous faults
provide a moderately favorable environment for geothermal
resources, with a low level of confidence because no hot
springs are known in the area.

24

c. Sodium and Potassium

WSA CA 010-082

SI-ID. The geological environment has no favorability for
sodium or potassium resources.

3. SALEABLE RESOURCES

Saleable resources have been covered in connection with
nonmetallic minerals.

25

V. RECOMMENDATIONS FOR ADDITIONAL WORK

Classification area M1-3C should be reconnoitered to determine if
there is any hydrothermal alteration that might lead to
mineralized areas. If hydrothermal alteration is found, it should
be mapped. The existing geological mapping covers rock types
well, but it appears that alteration, if there is any, was not
addressed as part of the mapping.

26

VI. REFERENCES AND SELECTED BIBILOGRAPHY

American Bureau of Metal Statistics Inc., 1982, Non-ferrous metal
data - 1981, Park City Press, New York, New York, p. 133-134.

Anderson, G. G., 1937, Granitization, albitization, and related
phenomena in the northern Inyo Range of California-Nevada: Geol.
Soc. America Bull., v. 48, p. 1-74.

Bateman, P. C, 1965, Geology and tungsten mineralization of the
Bishop district, California: U.S. Geol. Survey Prof. Paper 470,
208 p.

Blackwelder, Eliot, 1931, Pleistocene glaciation in the Sierra
Nevada and Basin Ranges: Geol. Soc. America Bull., v. 42, p. 865-
922.

Crowder, D. F. , Robinson, P. T., and Harris, D.L., 1972, Geologic
map of the Benton quadrangle, Mono County, California, and
Esmeralda and Mineral Counties, Nevada: U.S. Geol. Survey Geol.
Quad. Map GQ-1013, scale 1:62,500.

Crowder, D. F., and Sheridan, F. F. , 1972, Geologic map of the
White Mountain Peak quadrangle, Mono County, California: U. S.
Geol. Survey Geol Quadrangle Map GQ 1012, Scale 1:62,500. Geology
of the eastern half of the GRA.

Dalrymple, G. B. , Cox, Allan, and Doell, R. R. , 1965, Potassium-
argon age and paleomagnetism of the Bishop Tuff, California: Geol.
Soc. America Bull., v. 76, p. 665-674.

Davis, J. F., 1983, Letter dated January 17, 1983 to Reginald
Reed, USBLM, from J. F. Davis, State Geologist, with comments on
Final Draft GRA Reports. In GRA File.

Gilbert, C. M. , 1941, Late Tertiary geology southeast of Mono
Lake, Calif.: Geol. Soc. America Bull., v. 52, p. 781-816.

High Life Helicopters, Inc., 1980, Airborne gamma ray spectrometer
and mangetometer survey, Mariposa Quadrangle: NURE report GJBX-
231(80) .

Kirk, William S., 1980a, Thorium in Mineral Facts and Problems,
1980ed., U. S. Bureau of Mines, Bull. 671, p. 937-945.

Kirk, William S., 1980b, Thorium in Minerals Yearbook, vol. I,
Metals and Minerals, U. S. Bureau of Mines, p. 821-826.

Kirk, William S., 1982, Thorium in Mineral Commodity Summaries -
1982, U. S. Bureau of Mines, p. 160-161.

27

Krauskopf/ K.B., 1971, Geologic map of the Mt. Barcroft
quadrangle, California-Nevada: U.S. Geol. Survey Geol. Quad. Map
GQ-960, scale 1:62,500.

Mayo, E. B. , 1934, Pleistocene Long Valley Lake in eastern
California: Science, n. s., v. 80, p. 95-96.

McKee , E. H. , Silberman, M. L., Marvin, R. E. , and Obradovich, J.
D., 1971, A summary of radiometric ages of Tertiary volcanic rocks
in Nevada and eastern California; part 1, central Nevada: Isochron
West, no. 2., p. 21-42.

Mining Journal, July 24, 1981, vol. 297, No. 7641.

Minobras, 1978, Uranium Deposits of Arizona, California, Nevada.

Moore, J. G., and Hopson, C. A., 1961, The Independence dike swarm
in eastern California: Am. Jour. Sci., v. 249, p. 241-259.

Muffler, L. J. P., ed., 1979, Assessment of geothermal resources
of the United States - 1978: U. S. Geol. Survey Circ. 790.

NOAA/National Oceanic and Atmospheric Administration, 1980,
Geothermal resources of California: Map prep, by Nat. Geophy. and
Solar-Terrestrial Data Center from data compiled by California
Division of Mines and Geology, California Geologic Data Map
Series, Map No. 4.

Pakiser, L. C, Kane, M. F., and Jackson, W. H., 1964, Structural
geology of the Owens Valley region, California - a geophysical
study: U.S. Geol Survey Prof. Paper 438. Gravity coverage of the
GRA, based on rather widely-spaced observations.

Putnam, W. C. , 1952, Origin of Rock Creek and Owens River gorges,
California (abs.): Geol. Soc. America Bull., v. 63, p. 1291-1292.

Reed, R. D., 1933, Geology of California: American Assoc. Petrol.
Geologists, 24:1-355.

Rinehart, C. D., and Ross, D. C. , 1956, Economic geology of the
Casa Diablo Mountain quadrangle, Calif.: Calif. State Mines and
Geology, Special Report 48. Mostly concerned with Black Rock
tungsten mine. Good locations for all other mines and prospects.

Rinehart, C. D., and Ross, D. C, 1957, Geologic map of the Casa
Diablo Mountain quadrangle, California: U.S. Geol. Survey Geol.
Quad. Map GQ-99, scale 1:62,500. Geology much more detailed than
in 1956 publication.

Rinehart, C. D., Ross, D. C, and Huber, N. K. , 1959, Paleozoic
and Mesozoic fossils in a thick stratigraphic section in the
eastern Sierra Nevada, California: Geol. Soc. America Bull., v.
70, p. 941-946.

28

Scholl/ D. W. , von Huene, R. , St . -Amand , P., and Ridlon, J. B. ,
1967, Age and origin of topography beneath Mono Lake, a remnant
Pleistocene lake, California: Geol. Soc . America Bull., v. 78, p.
583-600.

Sheridan, M. F. , 1970, Fumarolic mounds and ridges of the Bishop
Tuff, California: Geol. Soc. America Bull., v. 81, p. 851-868.

Silberman, M. L. and McKee, E. H. , 1972, A summary of radiometric
age determinations on Tertiary volcanic rocks from Nevada and
eastern California; part 2, western Nevada: Isochron West, no. 4,
p 7-28.

Strand, R. G., 1967, Geologic map of California, Mariposa sheet:
California Div. of Mines and Geology.

Tucker, W. B. , 1927, Mono County, California: California Min.
Bureau, 23rd Report.

29

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»

LEVEL OF CONFIDENCE SCHEME

A. THE AVAILABLE DATA ARE EITHER INSUFFICIENT AND/OR CANNOT
BE CONSIDERED AS DIRECT EVIDENCE TO SUPPORT OR REFUTE THE
POSSIBLE EXISTENCE OF MINERAL RESOURCES WITHIN THE
RESPECTIVE AREA.

B. THE AVAILABLE DATA PROVIDE INDIRECT EVIDENCE TO SUPPORT
OR REFUTE THE POSSIBLE EXISTENCE OF MINERAL RESOURCES.

C. THE AVAILABLE DATA PROVIDE DIRECT EVIDENCE, BUT ARE
QUANTITATIVELY MINIMAL TO SUPPORT TO REFUTE THE POSSIBLE
EXISTENCE OF MINERAL RESOURCES.

D. THE AVAILABLE DATA PROVIDE ABUNDANT DIRECT AND INDIRECT
EVIDENCE TO SUPPORT OR REFUTE THE POSSIBLE EXISTENCE OF
MINERAL RESOURCES.

CLASSIFICATION SCHEME

1. THE GEOLOGIC ENVIRONMENT AND THE INFERRED GEOLOGIC PROCESSES
DO NOT INDICATE FAVORABILITY FOR ACCUMULATION OF MINERAL
RESOURCES,

2. THE GEOLOGIC ENVIRONMENT AND THE INFERRED GEOLOGIC PROCESSES
INDICATE LOW FAVORABILITY FOR ACCUMULATION OF MINERAL
RESOURCES.

3. THE GEOLOGIC ENVIRONMENT, THE INFERRED GEOLOGIC PROCESSES,

AND THE REPORTED MINERAL OCCURRENCES INDICATE MODERATE FAVORABILITY
FOR ACCUMULATION OF MINERAL RESOURCES,

4. THE GEOLOGIC ENVIRONMENT, THE INFERRED GEOLOGIC PROCESSES,
THE REPORTED MINERAL OCCURRENCES, AND THE KNOWN MINES OR
DEPOSITS INDICATE HIGH FAVORABILITY FOR ACCUMULATION OF
MINERAL RESOURCES.

w

MAJOR STRATIGRAPHIC AND TIME DIVISIONS IN USE BY THE
U.S. GEOLOGICAL SURVEY

Erathem or
Era

Cenozoic

Mesozoic

System or Period

Series or Epoch

Quaternary

1 Hoi

ocene

Pleistocene

Pliocene

Miocene

Tertiary

Oligocene

Eocene

Paleocene

Cretaceous *

Upper (Late)
Lower ( Early)

Jurassic

Upper (Late)
Middle (Middle)
Lower ( Early)

Triassic

Upper (Late)
Middle (Middle)
Lower ( Early)

Permian *

Upper (Late)
Lower ( Early)

Paleozoic

3

2 »
«S £

Pennsylvanian '

Upper (Late)
Middle (Middle)
Lower (Early)

w i Mississippian '

Upper (Late)
Lower ( Early)

Devonian

Upper (Late)
Middle (Middle)
Lower ( Early)

Silurian

Upper (Late)
Middle (Middle)
Lower ( Early)

Ordovician '

Upper ( Late)
Middle (Middle)
Lower \ Early)

Cambrian '

Upper (Late)
Middle (Middle)
Lower ( Early)

Estimated ages of

time boundaries in

millions of year*

.2-3 '_
_12l_
_26'_

Precambrian

Informal subdivisions
Mjch as upper, middle,
and lower, or uppi-r
and lower, or young-
er and older may bo-
used locally.

.37-38.
.53-54.
_65_

.136.

.190-195.

_225.

.280.

.345.

-395.

.430-440.

.500.

i70.

3/.00 + '

1 ||"lmni. Arthur. I'JiiS, Principle* of physirsl u«-..l..*y 2d ed . New York. Honald I'rni, p 360-361. for
the Pliisto-ene and Pliocene; and Obrad.iv irh. J I) . I'jCi. Aire «,f mann« PUiaOieene of California: Am.
A-sK. IMruleum Cirulouiats, v. VJ. no 7. p l'«T f.,r the PI. istocrne of southern California.

■ (J.siloviral Society of l^mdon. I!)*4. The Phanrrtnoic tim<-«rale; a ijmpunum: Geol. Soe. London, Quart.
Jour., v. 120. nupp . p. 2til}-2h2. for the Mi.<ene thr.utfh the Cambrian.

'Stern. T. W., written emmun., PJbti. fur the Pir<«mbri«n

* include provincial «eri,-s accepted for u»e in U S. Geological Survey reports.

Term-. designating time are in parenthran Informal limr terms early, middle, and late may be used for
the rru. and for periods where there is no formal subdivision into Early. Middle, and Late, and for epochs.
Informal nvk urms lower, middle, and upper may be u«cd where there is no formal subdivision of a
ivntem or of a iinoa.

GF.Ot.OGIC NAMES COMMITTEE. 1970

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