Mineral Resources of the Sawtooth 

Mountains and Carrizo Gorge/Eastern 

McCain Valley Wilderness Study Areas, 

San Diego County, California

U.S. GEOLOGICAL SURVEY BULLETIN 1711-B

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 be submitted to the President 

and the Congress. This report presents the results of mineral surveys for part of the 

Sawtooth Mountains (CA-060-024B) Wilderness Study Area, San Diego County, California 

and for the Carrizo Gorge/Eastern McCain Valley (CA-060-025A) Wilderness Study Area, 

San Diego County, California.

CONTENTS

Summary Bl

Abstract 1

Character and settingl

Mineral resources and mineral resource potential of the Sawtooth Mountains

Wilderness Study Area 3 

Mineral resources and mineral resource potential of the Carrizo Gorge/Eastern

McCain Valley Wilderness Study Area 3 

Introduction 3

Area descriptions 3 

Previous and present investigations 3 

Acknowledgments 5 

Regional geologic setting 5 

Appraisal of identified resources of the Sawtooth Mountains Wilderness Study

Area 6

Assessment of mineral resource potential of the Sawtooth Mountains Wilderness 

Study Area 6 

Geology 6

Geochemical studies 7 

Geophysical studies 8 

Conclusions 8 

Appraisal of identified resources of the Carrizo Gorge/Eastern McCain Valley

Wilderness Study Area 8

Assessment of mineral resource potential of the Carrizo Gorge/Eastern McCain 

Valley Wilderness Study Area 8 

Geology 8

Geochemical studies 11 

Geophysical studies 11 

Conclusions 12 

References cited 12 

Appendix. Definition of levels of mineral resource potential and certainty

of assessment 14 

Geologic time scale 15

FIGURES

1. Index map showing location of the Sawtooth Mountains and Carrizo Gorge/Eastern 

McCain Valley Wilderness Study Areas, San Diego County, California B2

2. Map showing generalized geology of the Sawtooth Mountains Wilderness Study 

Area, San Diego County, California 4

3. Map showing mineral resource potential and generalized geology of the Carrizo 

Gorge/Eastern McCain Valley Wilderness Study Area, San Diego County, 

California 10

TABLES

1. Prospects in the Sawtooth Mountains Wilderness Study Area B6

2. Mines and prospects in and adjacent to the Carrizo Gorge/Eastern McCain Valley 

Wilderness Study Area 9

MINERAL RESOURCES OF WILDERNESS STUDY AREAS: SOUTHERN CALIFORNIA AND 

CALIFORNIA DESERT CONSERVATION AREA

Mineral Resources of the Sawtooth Mountains and

Carrizo Gorge/Eastern McCain Valley

Wilderness Study Areas, San Diego County, California

By Victoria R. Todd, James E. Kilburn, David E. Detra, 

Andrew Griscom, Daniel H. Knepper, Jr., and Fred A. Kruse 

U.S. Geological Survey

Eric Gather and David A. Lipton 

U.S. Bureau of Mines

SUMMARY

Abstract

This report presents the results of mineral 

surveys of part of the Sawtooth Mountains (CA-060- 

024B) Wilderness Study Area and all of the Carrizo 

Gorge/Eastern McCain Valley (CA-060-025A) 

Wilderness Study Area. In this report, the areas 

studied are referred to as "the wilderness study areas", 

or simply "the study areas." The Sawtooth Mountains 

and Carrizo Gorge/Eastern McCain Valley study areas 

encompass approximately 24,696 and 14,573 acres, 

respectively, in eastern San Diego County, 

California. Field work for this report was carried out 

during 1983 and 1984. No mineral resources or 

resource potential have been identified in the 

Sawtooth Mountains Wilderness Study Area. The study 

area contains extensive sand and gravel occurrences, 

but these occurrences are not considered resources 

because similar ones are present closer to population 

centers such as San Diego and El Centro. The Carrizo 

Gorge/Eastern McCain Valley Wilderness Study Area 

has moderate potential for resources of undiscovered 

gem-grade minerals (kunzite, aquamarine) in 

pegmatite dikes in the vicinity of Mount Tule in the 

western part of the study area. No oil, gas, coal, or 

geothermal resources were identified in either of the 

study areas.

Character and Setting

The Sawtooth Mountains and Carrizo 

Gorge/Eastern McCain Valley Wilderness Study Areas 

have been combined into a single report because they 

are geographically close and have similar geologic 

settings. The Sawtooth Mountains and Carrizo 

Gorge/Eastern McCain Valley Wilderness Study Areas

occupy approximately 24,696 and 14,573 acres, 

respectively, in eastern San Diego County, Calif. They 

are located about 40 and 50 mi east of San Diego, 

respectively (fig. 1). The study areas lie within a 

transitional physiographic zone between the Peninsular 

Range province, the mountainous spine of Alta and 

Baja California to the west, and the Colorado Desert 

to the east. This zone is characterized by rugged 

topography and has a semiarid to arid climate. 

Conifer forests occupy the higher mountain ridges, and 

chapparal-desert plant communities are found at lower 

elevations. Topographic relief in the study areas 

ranges from about 3,800 to 4,100 ft.

The Sawtooth Mountains and Carrizo 

Gorge/Eastern McCain Valley Wilderness Study Areas 

are underlain by Cretaceous (63 to 138 million years 

before present (Ma); see appendix for geologic time 

scale) plutonic rocks of the Peninsular Ranges 

batholith that form much of the crystalline bedrock of 

the Peninsular Ranges. The batholith is composed of a 

variety of deformed Early Cretaceous plutons that 

were intruded by relatively undeformed younger 

Cretaceous plutons. These plutons intruded 

metamorphosed Paleozoic (240 to 570 Ma) and 

Mesozoic (63 to 240 Ma) sedimentary and volcanic 

rocks, remnants of which are exposed as steeply 

dipping tabular bodies, or screens, between the 

plutons. Patches of Cenozoic (63 Ma to present) 

alluvial deposits unconformably overlie the uplifted 

and deeply eroded batholith in both study areas. 

Faults of various ages cut the batholithic rocks. In the 

Sawtooth Mountains Wilderness Study Area, some 

faults cut Quaternary alluvium.

Small gold deposits are found in metasedimentary rocks in the Deer Park and Laguna Mountains 

mining districts, about 4 mi west of the Sawtooth 

Mountains Wilderness Study Area. There is no record 

of mining activity in similar metasedimentary rocks 

within the study area, and no gold or other mineral

B1
SAWTOOTH 

MOUNTAINS 

WILDERNESS 

STUDY AREA 

(CA-060-024B)

CARRIZO GORGE/EASTERN

MCCAIN VALLEY WILDERNESS

STUDY AREA (CA-060-025A)

5 MILES

Figure 1. Index map showing location of Sawtooth Mountains and Carrizo Gorge/Eastern 

McCain Valley Wilderness Study Areas, San Diego County, California.

B2
resources were found during this study. The Carrizo 

Gorge/Eastern McCain Valley Wilderness Study Area 

contains no mines, and no mineral resources were 

identified during this study. Two gem-producing mines 

are located in pegmatite dikes adjacent to the west 

boundary of the study area, and similar pegmatite 

dikes occur within the study area in the vicinity of 

Mount Tule.

Mineral Resources and Mineral Resource Potential of 

the Sawtooth Mountains Wilderness Study Area

No mineral resources or resource potential have 

been identified in the Sawtooth Mountains Wilderness 

Study Area although evidence of minor mineralization 

is present. Two prospects in the western part of the 

study area revealed pegmatite and quartz veins in 

pelitic schist (fig. 2), a geologic environment similar to 

that of gold-bearing mineralized zones about 4 mi west 

of the study area. Samples from the two prospects in 

the study area contained no significant metal 

concentrations. A reconnaissance geochemical survey 

of stream sediments revealed widespread tungsten and 

tin anomalies as well as localized silver, barium, 

copper, bismuth, and lead anomalies. These 

geochemical anomalies are probably related to the 

abundances of particular rock types within the study 

area and do not indicate resources. The above data, 

and the absence of mining activity in the area, 

indicate that there is no potential for undiscovered 

mineral resources. Sand and gravel occurrences exist 

but are not considered resources at this time because 

of the high cost of transporting these materials to 

population centers. No potential for undiscovered oil 

and gas or other energy resources was identified in the 

study area.

Mineral Resources and Mineral Resource Potential of 

the Carrizo Gorge/Eastern McCain Valley Wilderness 

Study Area

No mineral resources have been identified; 

however, available data suggest that the Carrizo 

Gorge/Eastern McCain Valley Wilderness Study Area 

has moderate potential for gem-grade minerals in 

pegmatite dikes near Mount Tule (fig. 3). Two active 

mines adjacent to the west boundary of the study area 

near Mount Tule have produced significant quantities 

of gem-grade aquamarine and kunzite from pegmatite 

dikes that cut a large screen consisting of gabbro, 

tonalite, and metasedimentary rocks. Many 

lithologically similar dikes are present within the study 

area in the Mount Tule area and detailed exploration 

of them might disclose gem-bearing pockets. 

Scattered exposures of manganiferous rocks in the 

study area are too small to be considered resources. A 

reconnaissance geochemical survey of stream 

sediments disclosed widespread tungsten and tin 

anomalies as well as locally high concentrations of 

boron, bismuth, molybdenum, and barium. In most 

cases, these anomalies are related to the abundances 

of specific rock types within the study area and do not 

indicate the existence of mineral resources. No 

mineral or sand and gravel resources were identified in

the study area. No potential for undiscovered oil and 

gas or other energy resources was determined in the 

study area.

INTRODUCTION 

Area Descriptions

This report presents the results of mineral 

surveys of part of the Sawtooth Mountains (CA-060- 

024B) Wilderness Study Area and all of the Carrizo 

Gorge/Eastern McCain Valley Wilderness Study Area. 

In this report, the areas studied are referred to as "the 

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

The Sawtooth Mountains and Carrizo Gorge/Eastern 

McCain Valley Wilderness Study Areas are located 

about 40 and 50 mi east, respectively, of San Diego, 

Calif., where they comprise approximately 24,696 and 

14,573 acres, respectively (fig. 1). In this region, a 

subdued upland surface that forms the crest of the 

Peninsular Ranges is succeeded to the east by rugged 

desert mountain ranges and alluviated valleys. The 

climate is semiarid to arid; vegetation varies from 

pinyon-juniper-mountain mahogany woodlands at 

higher elevations, through a mixed chaparral-sagedesert flora at intermediate elevations, to a true 

desert community that includes agave and cactus with 

isolated palm groves at the heads of canyons.

The Sawtooth Mountains Wilderness Study Area 

includes part of the deeply incised eastern escarpment 

of the Laguna Mountains; elevations range from about 

5,900 ft at the edge of the escarpment to about 1,800 

ft in the desert valley below. Sunrise Highway 

provides access to the western part of the study area 

and the northern part can be reached by unimproved 

dirt roads that lead up several large canyons. McCain 

Valley Road originates at California Highway 80 in 

Boulevard and provides access to the southern part of 

the area.

The Carrizo Gorge/Eastern McCain Valley 

Wilderness Study Area is located in the In-ko-pah 

Mountains and includes part of the McCain Valley 

National Cooperative Land and Wildlife Management 

Area on the west. The south boundary of the study 

area lies less than 1 mi north of Interstate 8. The 

study area encompasses part of the western wall of a 

spectacular gorge cut by northward-flowing Carrizo 

Creek. Elevations range from 4,647 ft on Mount Tule 

to about 800 ft in lower Carrizo Canyon; peaks named 

Grunt, Gasp, and Groan suggest the ruggedness of the 

terrain in and near the study area. The western part 

of the area can be reached from McCain Valley Road 

by an unimproved dirt road to Sacotone Spring (fig. 

3). Access to the northern part of the area is from 

County Road S-2, while the eastern part is accessible 

from Dubber Spur, a siding on the presently defunct 

San Diego and Arizona Eastern Railroad.

Previous and Present Investigations

This mineral resource study is a joint effort by 

the U.S. Geological Survey (USGS) and the U.S. Bureau 

of Mines (USBM). The history and philosophy of such 

joint mineral surveys of U.S. Bureau of Land

B3
116°25 116°20'

r-^ V^SL^^^

Kip/1/ JXZ? VaHecito~~^C^ek {r^f $

APPROXIMATE BOUNDARY OF

SAWTOOTH MOUNTAINS

WILDERNESS STUDY

AREA (CA-060-024B)

Figure 2. Map showing generalized geology of the Sawtooth Mountains Wilderness Study Area, San Diego County, 

California. Area contains no mineral or energy resource potential.

B4
EXPLANATION

Stream-sediment sample site

Unnamed prospect See table 1 for description

Surficial deposits (Quaternary and Tertiary) 

Late- tectonic to posttectonictonalite (Cretaceous)

Tonalite of Las Bancas (Cretaceous?) l-type 

pluton

Gneissic and migmatitic granitic rocks 

(Cretaceous?) S-type pluton

Cuyamaca Gabbro (Cretaceous)

Prebatholithic metasedimentary rocks (Jurassic and 

Triassic)

Contact

High-angle fault Dashed where approximately 

located or inferred; dotted where concealed; 

U on upthrown side; D on downthrown side

Low-angle fault Teeth on upper plate 

Shear zone

Figure 2. Continued.

Management (BLM) study areas are discussed by 

Beikman and others (1983). Mineral assessment 

methodology and terminology are discussed by 

Goudarzi (1984). Studies by the USGS are designed to 

provide a reasonable scientific basis for estimating the 

possibilities for the existence of undiscovered mineral 

resources by determining geologic units and structures, 

possible environments of mineral deposition, and 

presence of geochemical and geophysical anomalies. 

The USBM evaluates identified resources at individual 

mines and known mineralized areas by collecting data 

on current and past mining activites and through field 

examination of mines, prospects, and mineralized 

areas.

Published geologic maps of the Agua Caliente 

Springs (Todd, 1977), Monument Peak (Todd, 1978), and 

Mount Laguna (Todd, 1979) quadrangles describe the 

geology of most of the Sawtooth Mountains Wilderness 

Study Area. The northern part of the Carrizo 

Gorge/Eastern McCain Valley Wilderness Study Area 

was mapped by Hoggatt (1979), and a study by Minch 

and Abbott (1973) provided information on the postbatholithic geologic history south of the study area. 

The U.S. Geological Survey carried out field 

investigations in the study areas during 1983 and 

1984. The work included new mapping, whole rocR and 

stream sediment sampling for geochemical analysis 

and radiometric dating, and aeromagnetic and gravity 

surveys. A total of 98 panned heavy-mineral 

concentrates from stream sediment samples from both 

study areas were analyzed. The analytical data are 

given in Detra and Kilburn (1985a, b).

The U.S. Bureau of Mines conducted a library 

search for information on mines and prospects in and

adjacent to the study areas. These data were 

supplemented by information from claim owners and 

from San Diego County and U.S. Bureau of Land 

Management mining claim and lease records. Field 

studies by U.S. Bureau of Mines personnel were carried 

out in 1983. The study areas were searched on foot 

and by helicopter for evidence of mining activity or 

mineralized zones. During this time, 13 lode samples 

were collected from the two study areas for chemical 

analysis by fire assay, atomic absorption, inductively 

coupled plasma spectrographic, colorimetric, and Xray fluorescence methods. In addition, approximately 

40 elements were analyzed by semiquantitative 

spectrographic method. Analytical results are given in 

Gather (1984) and Lipton (1985).

Acknowledgments

The authors acknowledge Fred Stevens and Loren 

Beebe who supplied production data pertinent to their 

mining claims adjacent to the Carrizo Gorge/Eastern 

McCain Valley Wilderness Study Area. We also thank 

personnel of the El Centre and Riverside district 

offices of the Bureau of Land Management for advice 

on access to the study areas and for generously making 

their records available to us. The Anza-Borrego 

Desert State Park gave permission for helicopter 

landings in the state park adjacent to the study areas.

Regional Geologic Setting

The Sawtooth Mountains and Carrizo 

Gorge/Eastern McCain Valley Wilderness Study Areas 

lie within the Cretaceous Peninsular Ranges batholith 

of southern California, U.S.A., and Baja California, 

Mexico, and have similar geologic settings. In San 

Diego County, the batholith is overlapped by Upper 

Cretaceous to lower Pleistocene(?) sedimentary rocks.

Batholithic rocks in San Diego County have been 

divided into an older intrusive sequence that was 

contemporaneous with regional deformation and a 

younger sequence that largely postdated regional 

deformation (Todd and Shaw, 1979). Uranium-lead 

zircon ages from rocks that are considered to belong 

to the older sequence range from 120 to 105 Ma, 

whereas ages of the younger plutons range from 100 to 

95 Ma (Silver and others, 1979; Clinkenbeard and 

others, 1986). The older, deformed intrusive sequence 

was further subdivided into western I-type and eastern 

S-type granitic rocks (Todd and Shaw, 1979; 1985). 

This contrast in plutonic rock types is thought to 

reflect profound west-to-east differences in the source 

rocks of the batholith: western I-type plutons 

crystallized from partial melts of igneous source 

materials and eastern S-type plutons from partial 

melts of metasedimentary materials. The I- and Stype granitic rock classification is used in this report 

because it permits a large number of plutons to be 

divided into two groups, each including genetically 

related plutons. In San Diego County, these groups 

appear to be related to the presence or absence of 

mineral deposits, for example, S-type plutons are 

locally associated with gold in syntectonic quartz veins 

(Donnelly, 1934), while I-type granitic plutons show 

little mineralization.

B5
TABLE 1. Prospects in the Sawtooth Mountains Wilderness Study Area

Map No.

(fig. 2)

1

Name

Unnamed

prospect

Summary

A limonite-stained quartz v

Vein averages 1.0 ft thick

N. 30° E. and dips steeply

ein in schist.

, strikes

It can be

Workings

One shallow prospect pit

Sample data and

One sample of vein

significant metal

resource estimate

contained no

values.

traced about 25 ft along strike.

Unnamed A pegmatite dike and accompanying quartz vein 

prospect are concordant with foliation of biotite

schist and strike N. 15° E. and dip 72° SE. 

Strike length could not be determined due to 

poor exposure. Pegmatite is about 1.7 

ft thick and quartz vein averages 1.0 ft 

thick and is locally vuggy and limonitestained. A 4-ft diameter mass of silicified 

limonite-stained quartzite is within 50 ft 

of decline.

One 40-ft decline Three samples collected: a sample from 

200-lb stockpile of pegmatite 

contained 0.03 oz/ton gold; two 

samples of pegmatite and vein quartz 

contained no significant metal values.

Prebatholithic rocks that form the western wall 

of the Peninsular Ranges batholith are composed of 

metamorphosed volcanic and volcaniclastic rocks of 

Late Jurassic and Early Cretaceous age (Silver and 

others, 1963; Fife and others, 1967; Gastil and others, 

1975; Schoellhamer and others, 1981). Inclusions of 

metavolcanic rocks in the batholith in the western part 

of San Diego County are undated, but are generally 

correlated with the Upper Jurassic and Lower 

Cretaceous wallrocks. Wallrock inclusions in eastern 

San Diego County are composed of metasedimentary 

rocks that contain minor metavolcanic layers. 

Possibly related metasedimentary rocks outside the 

study area have yielded Middle Jurassic, probable 

Triassic, and Early Ordovician fossils (Gastil and 

others, 1981; Miller and Dockum, 1983). Although 

some of the prebatholithic metasedimentary rocks in 

eastern San Diego County may have been coeval with 

the western metavolcanic rocks, it is likely that 

Paleozoic and older Mesozoic strata are present.

Intrusion of the younger plutons, which largely 

post-dates deformation, was followed by uplift, 

erosion, sedimentation, and volcanism. Sedimentary 

and volcanic rocks include the Lusardi Formation, a 

locally derived continental fanglomerate of Late 

Cretaceous age, which overlies the eroded batholith in 

San Diego County (Kennedy and Peterson, 1975), the 

Eocene Poway Group (Kennedy and Peterson, 1975), 

and Miocene andesite and basalt (Minch and Abbott, 

1973). These volcanic rocks were uplifted by 

predominantly normal displacements on late Tertiary 

and Quaternary faults of the Elsinore fault zone, which 

forms the east margin of the Laguna and In-ko-pah 

Mountains of the Peninsular Ranges, and these rocks 

now occupy a position near the crest of the range. 

Faults of this system are still active, and have 

displaced batholithic contacts laterally as much as 2 

mi (Todd, 1977; 1978; 1979).

APPRAISAL OF IDENTIFIED RESOURCES OF THE 

SAWTOOTH MOUNTAINS WILDERNESS STUDY 

AREA

By Eric Gather

U.S. Bureau of Mines

No resources were identified in the Sawtooth 

Mountains Wilderness Study Area, and no record of 

mining activity was encountered during the literature

search. Two unnamed prospects in the western part of 

the study area (fig. 2) are in a geologic environment 

similar to that of mines in the nearby Julian, Deer 

Park, and Laguna Mountains mining districts, which 

have yielded gold. Lode gold mines in the Julian 

district, located 9 mi northwest of the study area, 

were operated principally from 1870 to the early 

1900's, and on a small scale during the 1930's; the 

mines yielded about $5 million in gold (Weber, 1963). 

Mineralized zones in the district are primarily in a 

large inclusion of Triassic and Jurassic(?) 

metasedimentary rocks that extends to the southeast. 

These rocks host small gold deposits in the Deer Park 

and adjacent Laguna Mountains districts about 4 mi 

west of the study area. The gold in all three districts 

is found in discontinuous quartz veins that are 

generally concordant with schistosity.

Four samples were taken at the two unnamed 

prospects in the study area. A sample of pegmatite 

from a 200-lb stockpile contained 0.03 oz/ton (troy 

ounce per ton) gold (table 1). The three remaining 

samples were from pegmatite and quartz veins and 

contained no significant metal values (Gather, 1984).

Sand and gravel occurrences in the study area 

are extensive, but these commodities are more 

accessible closer to population centers such as San 

Diego and El Centro. No oil, gas, coal, or geothermal 

resources were identified in the study area.

ASSESSMENT OF MINERAL RESOURCE POTENTIAL 

OF THE SAWTOOTH MOUNTAINS WILDERNESS 

STUDY AREA

By Victoria R. Todd, James E. Kilburn, David E. Detra,

Andrew Griscom, Daniel H. Knepper, Jr., and Fred A.

Kruse

U.S. Geological Survey

Geology

The western half of the Sawtooth Mountains 

Wilderness Study Area is underlain by Early 

Cretaceous I- and S-type plutons that were emplaced 

during regional deformation. I-type plutons consist of 

pyroxene tonalite and gabbro, while S-type plutons 

consist of tonalite and granodiorite. Large inclusions 

of prebatholithic rocks and numerous small inclusions 

were caught up in, and between, these plutons. All 

contacts dip steeply to the east. The pervasive northB6
northwest fabric of the batholith in the west half of 

the study area is manifested by the parallel alignment 

of elongated and flattened plutons, wallrocks, mineral 

foliation, and the axial planes of isoclinal folds. 

Lineations and fold axes in both plutons and wallrocks 

are coaxial and plunge steeply down the dip of 

foliation. The S-type plutons and wallrocks were 

folded together into a large south-pointing fold prior 

to intrusion of the I-type pyroxene tonalite. 

Moderately deformed pyroxene tonalite apparently 

intruded the hinge area of the fold and was drawn up 

north-northwestward along the fold limbs.

The east half of the study area is underlain by 

part of a large leucocratic tonalite pluton that 

intruded the I- and S-type plutons; it yields uraniumlead zircon ages of 95, 97, and 98 Ma in the southern 

part of San Diego County (L.T. Silver, personal 

commun., 1979; Clinkenbeard and others, 1986). This 

pluton is moderately deformed along the west margin 

but is essentially massive in its interior. Swarms of 

large leucocratic and pegmatite dikes emanate from 

this pluton and extend for many miles into the older 

plutonic terrane.

The prebatholithic rocks within and between the 

plutons consist of calcsilicate-bearing, feldspathic 

metaquartzite, pelitic schist, minor amphibolite, and 

scarce marble. The metasedimentary rocks are thinbedded and contain turbidite structures, suggesting 

deposition in a deep-water marine marginal basin. 

Limestone, metamorphosed to marble, is scarce and is 

found as small lenses. Skarns are present locally 

where small limestone bodies are intruded by granitic 

dikes. These prebatholithic rocks are undated but are 

presumed on regional evidence to be Triassic and 

Jurassic(?) in age.

Cenozoic deposits in the study area consist of 

eroded remnants of Pliocene and Pleistocene 

interfingering marine and continental sedimentary 

deposits that are overlain by Pleistocene and Holocene 

alluvial fan deposits on the flanks of the uplifted 

Laguna and Tierra Blanca Mountains.

At least four episodes of deformation are 

recorded in the study area. The earliest episode was 

deep-seated metamorphic folding of the prebatholithic 

rocks accompanied and followed by intrusion of Early 

Cretaceous plutons. The second episode involved Late 

Cretaceous and (or) early Tertiary low-angle faulting 

at depths of a few miles (Sharp, 1979). Low-angle 

imbricate faults resulting from this event cut the large 

pluton in the northeastern part of the study area. 

During Pleistocene time, sedimentary deposits in the 

northern part of the study area were folded broadly 

and eroded. These deposits are cut by the Neogene 

and Holocene Elsinore fault zone, which crosses the 

northern part of the study area (Todd, 1977, 1978). 

Faults in the study area have undergone chiefly dipslip movement and are not associated with significant 

alteration.

Geochemical Studies

A reconnaissance geochemical survey of stream 

sediments was conducted in the Sawtooth Mountains 

Wilderness Study Area in 1984. Nonmagnetic heavymineral concentrates from stream sediments have 

proven most effective in delineating mineralized

systems in the arid environs of the western United 

States and were accordingly selected as the sample 

medium for the geochemical survey. Forty-four 

samples were collected near range fronts from stream 

beds that drain areas of less than one to several square 

miles (fig. 2).

The nonmagnetic heavy-mineral concentrate, 

henceforth referred to as simply the concentrate, is in 

essence a modified stream sediment. Each sample was 

composited from active alluvium and sieved through a 

minus-10-mesh screen to remove the coarsest 

material. The concentrate was further reduced by 

bromoform separation and electromagnetic separation 

and analyzed for 30 elements by a semiquantitative 

emission spectrographic method (Grimes and 

Marranzino, 1968). The concentrates were also 

examined by optical methods to determine the mineral 

species present in the stream sediments. A complete 

listing of the analytical results can be found in Detra 

and Kilburn (198 5a).

Geochemical anomalies in the study area were 

limited to widespread tungsten and tin anomalies in 

addition to localized silver, barium, copper, bismuth, 

and lead concentrations. Most concentrates contain 

scheelite and barite but lack other ore-forming sulfide 

and oxide minerals. The widespread tin and tungsten 

anomalies in conjunction with scattered copper, lead, 

bismuth, and silver concentrations are not surprising. 

The geologic environment within the study area is 

similar to that of the large northwest-trending 

mineralized belt that lies immediately west of the 

study area (described in an earlier section) in which 

small skarns are present locally at contacts between 

metasedimentary rocks and granitic bodies. This belt 

contains scheelite, gold, and local lead and silver 

deposits. Considering the substantial amount of 

scheelite found in the samples from the study area, it 

would seem reasonable that the area contains 

scattered tungsten-bearing skarns in which tin, silver, 

bismuth, copper, and lead may be common constituents. Although no skarn deposits were seen within the 

study area, undetected small skarn deposits may be 

present in the series of wallrock screens that underlie 

steep, brushy slopes along the west side of the study 

area. The prominent tungsten, copper, and lead 

anomalies probably originated in these screens. The 

scattered tungsten anomalies located in the eastern 

part of the study area, specifically in Canebrake Wash 

and the Inner Pasture, may be associated with small 

metasedimentary inclusions within the granitic rocks. 

Most of the tin probably is derived from an accessory 

mineral or minerals disseminated throughout the large 

leucocratic tonalite pluton. Skarns may also have 

made some contribution to the tin anomalies. Barite, 

probably derived from minor veins and replacement 

bodies in the surrounding granitic and metamorphic 

rocks, was detected in minor amounts in most of the 

concentrates. Due to the pervasive character of the 

barite, it is interesting that the only barium anomalies 

are found near the junction of the Tierra Blanca and 

Sawtooth Mountains in the northeastern part of the 

study area. The barium anomalies coincide with the 

Elsinore fault zone, which may have provided natural 

conduits for migrating hydrothermal solutions. 

However, evidence associating the barite and 

anomalous barium to specific mineralized systems of 

economic interest is lacking in the study area.

B7
Geophysical Studies

Three aeromagnetic and gamma-ray spectrometer profiles (High Life Helicopters, Inc., and QEB, 

Inc., 1980) cross the study area with a flightline 

spacing of approximately 3 mi. The data were 

collected along east-west traverses by helicopter at a 

height of 400 ft above ground. The magnetic data 

collected near the study area are nearly featureless 

because none of the rocks are particularly magnetic. 

A major magnetic boundary between magnetic I-type 

plutonic rocks to the west and nonmagnetic S-type 

rocks to the east is located 1 to 2 mi west of the study 

area and there strikes approximately N. 45° W. The 

radioactivity data for the study area indicate no 

significant amounts of uranium or thorium.

The limonite mineral group has unique spectral 

reflectance characteristics that can be detected on 

Landsat images using a color-ratio compositing 

technique described by Rowan and others (1974). This 

technique was applied in the Sawtooth Mountains 

Wilderness Study Area. The extensive lowland areas 

along lower Storm Canyon, the Potrero, Inner Pasture, 

and Canebrake Wash (fig. 2) are densely vegetated and 

thus could not be evaluated for anomalous 

concentrations of limonite using Landsat data. 

Elsewhere in the study area, only a few isolated 

patches of limonitic materials were observed. These 

limonitic areas are small and are not clustered into 

patterns suggestive of possible hydrothermal 

alteration. The only significant occurrence of 

anomalous limonite near the study area is in the Tierra 

Blanca Mountains 1.5 mi northeast of the study area 

boundary.

Gravity data for the Sawtooth Mountains 

Wilderness Study Area (Oliver and others, 1980; 

Roberts and others, 1981; Andrew Griscom, unpub. 

data, 1986) are sparse and do not provide significant 

information contributing to a mineral resource 

appraisal of the study area.

Conclusions

Geologic, geochemical, and geophysical 

investigations in the Sawtooth Mountains Wilderness 

Study Area indicate that the area lacks significant 

mineralization. No mineral resources are identified. 

Although the geologic setting of the study area is 

similar to those of the nearby Deer Park and Laguna 

Mountains mining districts, there is no mineral 

resource potential for gold or other metals in the study 

area. This is probably because the host rock for goldbearing quartz veins, pelitic schist, forms only a minor 

part of the bedrock in the study area.

Sand and gravel deposits in and near the study 

area are large, but similar deposits are present closer 

to population centers. There is no potential for oil, 

gas, or coal resources in the study area because such 

commodities would not be expected to occur in 

crystalline rocks. Hot springs are present at Agua 

Caliente Springs in the frontal fault zone of the Tierra 

Blanca Mountains outside the study area, but this 

locality is not considered a geothermal resource. 

There are no geothermal resources within the study 

area.

APPRAISAL OF MINERAL RESOURCES OF THE 

CARRIZO GORGE/EASTERN McCAIN VALLEY 

WILDERNESS STUDY AREA

By David A. Lip ton 

U.S. Bureau of Mines

The Carrizo Gorge/Eastern McCain Valley 

Wilderness Study Area contains no mines, and no 

mineral resources were identified in the area. 

Chemical analyses of nine lode samples from eight 

properties in and adjacent to the study area by the 

U.S. Bureau of Mines revealed no anomalous mineral 

concentrations (table 2) (Lipton, 1985). Two gemproducing mines are adjacent to the west boundary of 

the study area in the vicinity of Mount Tule (fig. 3). 

High-grade gem pockets containing kunzite and 

aquamarine in pegmatite dikes are currently being 

developed at the Pack Rat and Beebe Hole mines. The 

Beebe Hole mine has produced gem-quality kunzite 

valued at approximately $500,000 during the last 10 yr, 

and aquamarine valued at several thousand dollars in 

the last few years (Fred Stevens, oral commun., 

1984). Additional gem-bearing pockets are likely to 

exist at these claims, but remaining resources cannot 

be calculated because of the scattered nature of the 

deposits.

Pegmatite dikes at these claims dip away from 

and do not extend into the study area. However, more 

than two dozen similar pegmatite dikes are present in 

the area from Mount Tule to Carrizo Gorge and a few 

dikes are found in the Rockhouse Canyon area. The 

pegmatite dikes within the study area in the vicinity of 

Mount Tule contain several of the characteristic 

minerals used by prospectors to find pockets within the 

dikes, such as line rock, schorl, and abundant sheets of 

mica. Detailed exploration of the pegmatite dikes 

near Mount Tule might disclose gem-bearing pockets. 

The Rockhouse Canyon area lacks many of the 

minerals characteristic of gem-bearing pockets.

Small exposures of manganiferous rocks are 

scattered within the central part of the study area. 

However, these occurrences are not extensive enough 

to be considered resources. Occurrences of sand and 

gravel were not identified. There are no leases for oil 

and gas or geothermal energy.

ASSESSMENT OF MINERAL RESOURCE POTENTIAL 

OF THE CARRIZO GORGE/EASTERN McCAIN 

VALLEY WILDERNESS STUDY AREA

By Victoria R. Todd, James E. Kilburn, David E. Detra, 

Andrew Griscom, Daniel H. Knepper, Jr., 

and Fred A. Kruse 

U.S. Geological Survey

Geology

The Carrizo Gorge/Eastern McCain Valley 

Wilderness Study Area is underlain by deformed Early 

Cretaceous I- and S-type plutonic rocks and prebatholithic metasedimentary rocks (fig. 3). These rocks 

were intruded by a largely undeformed granitic pluton 

in part dated at 95 Ma by the uranium-lead method

B8
TABLE 2. Mines and prospects in and adjacent to the Carrizo Gorge/Eastern McCain Valley Wilderness Study Area

[*, outside study area]

Map No. 

(fig. 3) Summary Workings and production Sample data and resource estimate

Unnamed A pegmatite pod 50 by 30 ft in biotite schist 

prospect has trace amounts of black tourmaline.

 do An intermittent pegmatite dike as thick as 200 

ft strikes N. 19° E. and dips vertically 

in biotite schist. It is probably same 

dike located at map No. 3. Minor black 

tourmaline found in pegmatite.

 do An intermittent pegmatite dike as much as 50 

ft thick strikes N. 19° E. and dips 

vertically. Dike is in biotite schist.

 do Manganese oxide-coated schist, gneiss, and 

phyllite in area of about 20 ft .

 do An intermittent quartz vein in quartzite

contains manganese oxide as disseminations, 

blebs 6 in. by 3 in., and surface coatings. 

The vein is as much as 14 ft thick, trends 

northeast, and is exposed for approximately 

200 ft. Trace fragments of rhodonite 

present at contact with country rocks.

Beebe Hole mine A 12- to 15-ft-thick pegmatite dike strikes 

N. 22° W. and is exposed intermittently for 

about 1/2 mi in schist and quartzite. 

Faulting of dike has caused dip to 

range from 5° to 60° SW. Pockets within 

dike have gem minerals of quartz, heliodor, 

aquamarine, and kunzite. In addition to gem 

minerals, minor concentrations of lithiophilite, cassiterite, cleavelandite, 

columbite/tantalite, black tourmaline 

(schorl), and mica were observed. Most 

pockets are filled with montmorillonite clay. 

Pockets range in size from few in. to 

several ft; three to five pockets commonly 

in zones.

Pack Rat mine Several 10- to 20-ft-thick pegmatite dikes 

trend N. 6° W., dip 65° W., and extend as 

far as one-half mi in schist and quartzite. 

Pegmatite pockets contain microcline, green 

mica, black tourmaline (schorl), columbite/ 

tantalite, gem-grade beryl (heliodor), 

apatite, red garnet (spessartite), and 

quartz. Most pockets are filled with 

montmorillonite clay and range in size 

from few in. to several ft.

Unnamed Two 15- to 25-ft-thick pegmatite dikes strike 

prospect north, appear to dip 40° W., and are exposed 

intermittently for about 1 mi in granite 

that contains inclusions of schist and 

quartzite. Pockets in pegmatite contain 

black tourmaline (schorl), mica, cleavelandite, quartz, and microcline and range in 

size from few in. to several ft.

One prospect pit 4 ft in 

diameter.

One prospect pit 5 ft in 

diameter.

One prospect pit 4 ft in 

diameter.

Four prospect pits each 

approximately 3 to 6 ft 

in diameter.

Three adits, each less than 

20 ft long, and one open cut. 

According to co-partner Fred 

Stevens, SO.5 million 

dollars in gem quality 

kunzite recovered from 

gem pockets during 

last 10 years. He 

further stated that 

several thousand dollars 

worth of aquamarine has been 

recovered during last 

few years.

Eight open cuts. According to 

current claimant, several 

specimens of aquamarine and 

garnet have been sold.

Two open cuts

No samples were taken, 

were observed.

No gem minerals

One random chip sample of pegmatite 

contained no significant mineral values. 

No gem minerals were observed.

One select sample contained no significant 

mineral values.

Five chip samples across the vein contained 

1.8 pet, 1.3 pet, 1.2 pet, 0.4 pet, and 

0.02 pet manganese. A selected sample 

had 5.3 pet manganese.

It is highly probable that additional gembearing pockets will be found on this 

claim. No samples were taken. Four zones 

with multiple poekets within the pegmatite 

were observed to contain small quantities of 

gem-quality aquamarine, kunzite, and quartz. 

Although pegmatite dike dips away from, 

and is outside of, study area, dozens 

of similar dikes are found on Mount Tule 

within study area (fig. 3). The similar 

nature of pegmatite dikes within study 

area indicates exploration may reveal 

gem-bearing pockets.

One random chip sample of green mica 

contained 6.1 pet potassium, 0.15 pet 

fluorine, 0.00069 pet beryllium, 0.028 pet 

lithium, 0.016 pet magnesium, and 0.055 

pet manganese. Pockets within pegmatite 

were observed to contain several indicator 

minerals of gem-bearing zones. Pegmatite 

dikes are outside of, and dip away from, 

study area.

Although no gem minerals were observed, 

further excavation might yield minerals 

of grade found at the Pack Rat and 

Beebe Hole Mines. No samples were taken. 

Pockets within pegmatite contain 

several indicator minerals of gem-bearing 

zones. Pegmatites here are similar to 

to those worked at the Pack Rat and Beebe 

Hole mines.

(Clinkenbeard and others, 1986). The study area 

differs from the Sawtooth Mountains Wilderness Study 

Area in that the older rocks form a large screen that is 

surrounded by the unde formed granitic pluton. This 

pluton consists of tonalite on the west side of the 

study area and of garnetiferous muscovite-biotite 

granite in the Jacumba Mountains on the east and 

south sides of the study area. A steep-walled gabbropyroxene tonalite complex, the gabbro-tonalite 

complex of Mount Tule, underlies Mount Tule in the 

southwestern part of the study area. This complex 

includes numerous dikes of the unde formed granitic 

pluton. A second gabbro-pyroxene tonalite complex is 

present in the southeast part of the study area. 

Numerous screens and inclusions of prebatholithic 

rocks are present within the Mount Tule rocks. 

Contact relations outside the study area indicate that 

pyroxene tonalite of the Mount Tule complex intruded 

the S-type plutonic rocks, which consist of a mixture 

of S-type gneissic granodiorite, partly melted pelitic 

schist, and paragneiss. Undeformed garnetiferous twomica granite in the southern part of the study area has 

given rise to numerous large leucocratic and pegmatite 

dikes that extend for miles across the older plutons in 

the study area.

Upper amphibolite-grade metasedimentary rocks 

are caught up in both older and younger plutonic rocks 

in the study area and locally form extensive migmatite 

zones within the plutonic rocks. These 

metasedimentary rocks are generally more quartz-rich 

and, east of the study area, contain more marble than 

those in the Sawtooth Mountains Wilderness Study 

Area. Skarns are developed locally where I-type 

pyroxene tonalite intruded and engulfed marble beds.

A single outcrop of Miocene volcanic rocks, the 

Alverson Andesite (Dibblee, 1954), is present in the 

study area. Younger sedimentary deposits northeast of 

the study area include Pliocene and Pleistocene marine 

and continental deposits associated with an incursion 

by the Gulf of California. These deposits are 

unconformably overlain by Pleistocene and Holocene 

alluvial fan deposits in Carrizo Canyon to the north,

B9
;

APPROXIMATE BOUNDARY OF

CARRIZO GORGE/EASTERN 

McCAIN VALLEY 

WILDERNESS A/ILL)hKINtbb b STUDY J^ 

AREA (CA-060-025A)

\

Figure 3. Map showing mineral resource potential and generalized geology of the Carrizo Gorge/ 

Eastern McCain Valley Wilderness Study Area, San Diego County, California.

B10
EXPLANATION Geochemical Studies

Area with moderate mineral resource potential for

gem minerals See appendix for levels of certainty

Stream-sediment sample site

Prospect

Mine with recorded past production see table 2

for description

Unnamed prospect 

Unnamed prospect 

Unnamed prospect 

Unnamed prospect 

Unnamed prospect 

Beebe Hole mine 

Pack Rat mine 

Unnamed prospect

Surficial deposits (Quaternary and Tertiary) 

Alverson Andesite of Dibblee (1954) (Miocene)

Table Mountain Gravels of Minch and Abbott 

(1973) (Miocene?)

Late-tectonic to posttectonic granitic rocks 

(Cretaceous)

Gabbro-tonalite complex of Mount Tule 

(Cretaceous) l-type plutons

Gneissic and migmatitic granitic rocks 

(Cretaceous?) S-type plutons

Prebatholithic metasedimentary rocks (Mesozoic? 

and Paleozoic?)

Contact Dashed where approximately located 

or inferred

High-angle fault Dashed where approximately located or 

inferred; dotted where concealed. Arrows indicate relative 

horizontal movement. D, downthrown; U, upthrown

Shear zone 

Landslide 

, Pegmatite dike

Figure 3. Continued.

and by Holocene alluvium in Carrizo Gorge and Walker 

Canyon east and south, respectively, of the study area. 

Faults of the Neogene and Holocene Elsinore 

fault zone are present in the northern part of the study 

area. Right-lateral, north- and north-northweststriking faults in the southern part of the map area 

have displaced Early Cretaceous plutonic contacts, but 

the intrusive contact of the undeformed leucocratic 

granitic pluton is only slightly offset. Faults of this 

trend continued to be active in Tertiary time because 

they cut the Jacumba Volcanics south of the study 

area (Minch and Abbott, 1973). The west-striking 

Walker Canyon fault may have been active at about 

the same time.

A reconnaissance geochemical survey of stream 

sediments was conducted in the Carrizo Gorge/Eastern 

McCain Valley Wilderness Study Area in 1984. 

Sampling and analytical methods are described in an 

earlier section on geochemical investigations in the 

Sawtooth Mountains Wilderness Study Area. A 

complete listing of the analytical results can be found 

in Detra and Kilburn (1985b).

Spectrographic analysis revealed widespread 

tungsten and tin anomalies as well as locally high 

concentrations of boron, bismuth, molybdenum, and 

barium. Mineralogically, the study area is 

characterized by widespread scheelite and barite and 

an absence of ore-forming sulfide and oxide minerals. 

The study area contains numerous pegmatite dikes and 

skarns that contain the above elements as common 

constituents. The most prominent tungsten anomalies 

are present with the only boron and bismuth anomalies 

in drainages along the east flank of Mount Tule in the 

southern part of the study area. Locally, minor tin 

anomalies accompany the boron and tungsten. 

Molybdenum anomalies are chiefly confined to 

Carrizo, Rockhouse, and Bow Willow Canyons in the 

north half of the study area and are also associated 

with the widespread tin anomalies. Unfortunately, no 

parent mineral was determined for the tin anomalies, 

which appear to be a regional trait. Most of the tin 

anomalies probably come from an accessory mineral, 

or minerals, in the undeformed leucocratic granitic 

pluton. Various minerals in skarns and pegmatites may 

have contributed in some measure to the tin 

anomalies. Scheelite was identified by optical 

methods as a minor mineral component in about 80 

percent of the concentrates and tourmaline was found 

coincident with the Mount Tule boron anomalies.

The anomalous barium concentrations found in 

Rockhouse and Bow Willow Canyons probably represent 

minor barite veins and (or) replacement bodies in the 

surrounding metasedimentary and granitic rocks. 

Barite, identified by optical methods, is present in the 

majority of the samples but associated ore-related 

minerals were not located in the study area. Barite 

formation may be related to circulation of hydrothermal solutions in faults of the Elsinore fault zone.

Geophysical Studies

Four aeromagnetic and gamma-ray spectrometer 

profiles (High Life Helicopter, Inc., and QEB, Inc., 

1980) cross the study area with a flightline spacing of 

approximately 3 mi. The data were collected along 

east-west traverses by helicopter at a height of 400 ft 

above ground. The magnetic data are nearly 

featureless because none of the rocks within the study 

area are particularly magnetic. The radioactivity data 

for these profiles show no anomalous amounts of 

uranium or thorium within the study area.

The limonite mineral group has unique spectral 

reflectance characteristics that can be detected on 

Landsat images using a color-ratio compositing 

technique described by Rowan and others (1974). This 

technique was used to look for areas of limonite in the 

Carrizo Gorge/Eastern McCain Valley Wilderness

B11
Study Area. The spectral response to Landsat data of 

the study area is dominated by vegetation. 

Consequently, the presence of anomalous 

concentrations of limonite that might possibly be 

associated with hydrothermal alteration could not be 

evaluated in most of the study area. In the eastern 

part of the study area, between Carrizo Gorge and the 

less dissected uplands to the west, the data indicate 

scattered occurrences of limonitic materials at the 

surface, but these occurrences are small and are not 

clustered into patterns that suggest hydrothermal 

alteration.

Gravity data available for the study area (Oliver 

and others, 1980; Roberts and others, 1981; Andrew 

Griscom, unpub. data, 1986) represent only about 10 

stations and do not contribute significantly to the 

mineral resource appraisal of the area.

Conclusions

Geologic studies, geochemical sampling, 

examination of prospects, and the absence of 

producing mines in the Carrizo Gorge/Eastern McCain 

Valley Wilderness Study Area indicate that the area 

lacks significant mineralization. Gem-bearing 

pegmatite dikes have been mined for aquamarine and 

kunzite at two claims outside, and adjacent to, the 

west boundary of the study area. The host rock of the 

gem-bearing dikes is a large, predominantly metasedimentary screen near Mount Tule. Although the 

pegmatite dikes at these claims do not extend into the 

study area, similar pegmatite dikes are present within 

the area in the vicinity of Mount Tule. Available data 

suggest that the Carrizo Gorge/Eastern McCain Valley 

Wilderness Study Area has moderate potential 

(certainty level C) for gem-grade minerals in 

pegmatite dikes in the vicinity of Mount Tule. See 

appendix for definition of levels of mineral resource 

potential and certainty of assessment. No other 

mineral resources are indicated and there is no 

potential for sand and gravel resources. There is no 

potential for resources of oil and gas or geothermal 

energy in the study area because such commodities 

would not be expected to occur in crystalline rocks.

REFERENCES CITED

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

PGather, Eric, 1984, Mineral resources of the Sawtooth

Mountains B Wilderness Study Area (BLM No.

060-024B), San Diego County, California: U.S.

Bureau of Mines Open-File Report MLA 30-84,

13 p. 

Clinkenbeard, J.P., Walawender, M.J., Parrish, K.E.,

and Wardlaw, M.S., 1986, The geochemical and

isotopic composition of the La Posta

Granodiorite, San Diego County, California:

Geological Society of America Abstracts with

Programs, v. 18, no. 2, p. 95.

Detra, D.E., and Kilburn, J.E., 1985a, Analytical 

results and sample locality maps of heavymineral concentrate samples from the Sawtooth 

Mountains Wilderness Study Area (CA-060-024B), 

San Diego County, California: U.S. Geological 

Survey Open-File Report 85-748.

___1985b, Analytical results and sample locality maps 

of heavy-mineral concentrate samples from the 

Carrizo Gorge Wilderness Study Area (CA-060- 

025A), San Diego County, California: U.S. 

Geological Survey Open-File Report 85-716.

Dibblee, T.W., Jr., 1954, Geology of the Imperial 

Valley region, California, in Jahns, R.H., ed., 

Geology of southern California: California 

Division of Mines Bulletin 170, p. 21-28.

Donnelly, Maurice, 1934, Geology and mineral deposits 

of the Julian district, San Diego County, 

California: California Journal of Mines and 

Geology, v. 30, p. 331-370.

Fife, D.L., Minch, J.A., and Crampton, R.J., 1967, 

Late Jurassic age of the Santiago Peak 

Volcanics, California Division of Mines and 

Geology: Geological Society of America 

Bulletin, v. 78, p. 299-304.

Gastil, R.G., Morgan, G.J., and Krummenacher, D., 

1981, The tectonic history of Peninsular 

California and adjacent Mexico, in The 

Geotectonic Development of California, Rubey 

Volume I, Ernst, W.G., ed., Prentice-Hall, Inc., 

New Jersey, p. 284-306.

Gastil, R.G., Phillips, R.P., and Allison, E.C., 1975, 

Reconnaissance geology of the State of Baja 

California: Geological Society of America 

Memoir 140, 170 p., 1 sheet.

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, Directcurrent arc and alternating-current spark 

emission spectrographic field methods for the 

semiquantitative analysis of geologic materials: 

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

High Life Helicopters, Inc., and QEB, Inc., 1980, 

Airborne gamma-ray spectrometer and 

magnetometer survey, San Diego quadrangle, 

California (1° by 2° sheet; National Uranium 

Resource Evaluation program, GJBX (80)): 

Grand Junction, Colo., U.S. Department of 

Energy, variously paged.

Hoggatt, W.C., 1979? Geologic map of the Sweeney 

Pass quadrangle, San Diego County, California: 

U.S. Geological Survey Open-File Report 79-754, 

28 p.

Kennedy, M.P., and Peterson, G.L., 1975, Geology of 

the eastern San Diego metropolitan area, 

California: California Division of Mines and 

Geology Bulletin 200, p. 43-56.

Lipton, D.A., 1985, Mineral resources of the Carrizo 

Gorge Wilderness Study Area (BLM No. CA-060- 

025A), San Diego County, California: U.S. 

Bureau of Mines Open-File Report MLA 23-85, 

14 p.

Miller, R.H., and Dockum, M.S., 1983, Ordovician 

conodonts from metamorphosed carbonates of 

the Salton Trough, California: Geology, v. 11, p. 

410-412.

B12
Minch, J.A., and Abbott, P.L., 1973, Post batholithic 

geology of the Jacumba area, southeastern San 

Diego County, California: San Diego Society of 

Natural History, Transactions, v. 17, no. 11, p. 

129-135.

Oliver, H.W., Chapman, R.H., Biehler, S., Robbins, 

S.L., Hanna, W.F., Griscom, Andrew, Beyer, 

L.A., and Silver, E.A., 1980, Gravity map of 

California and its continental margin: California 

Division of Mines and Geology, scale 1:750,000, 2 

sheets.

Roberts, C.W., Jachens, R.C., and Oliver, H.W., 1981, 

Preliminary isostatic residual gravity map of 

California: U.S. Geological Survey Open-File 

Report 81-573, scale 1:750,000, 5 sheets.

Rowan, L.C., Wetlaufer, P.H., Goetz, A.F.H., 

Billingsley, F.C., and Stewart, J.H., 1974, 

Discrimination of rock types and detection of 

hydrothermally altered areas in south-central 

Nevada by the use of computer-enhanced ERTS 

images: U.S. Geological Survey Professional 

Paper 883, 35 p.

Schoellhamer, J.E., Vedder, J.G., Yerkes R.F., and 

Kinney, D.M., 1981, Geology of the northern 

Santa Ana Mountains, California: U.S. 

Geological Survey Professional Paper 4ZO-D, 109

PSharp, R.V., 1979, Some characteristics of the eastern

Peninsular Ranges mylonite zone, in Proceedings, 

Conference VIH, analysis of actual fault zones in 

bedrock: U.S. Geological Survey Open-File 

Report 79-1239, p. 258-267.

Silver, L.T., Stehli, F.G., and Alien, C.R., 1963, Lower 

Cretaceous prebatholithic rocks of northern Baja 

California, Mexico: American Association of

Petroleum Geologists Bulletin, v. 47, p. 2054- 

2059.

Silver, L.T., Taylor, H.P., Jr., and Chappell, B., 1979, 

Some petrological, geochemical, and 

geochronological observations of the Peninsular 

Ranges batholith near the International Border of 

the U.S.A., and Mexico, in Abbott, P.L., and 

Todd, V.R., eds., Mesozoic Crystalline Rocks: 

Guidebook for Geological Society of America 

Annual Meeting, San Diego, California, p. 83- 

110.

Todd, V.R., 1977, Geologic map of the Agua Caliente 

Springs quadrangle, San Diego County, 

California: U.S. Geological Survey Open-File 

Report 77-742.

____1978, Geologic map of the Monument Peak 

quadrangle, San Diego County, California: U.S. 

Geological Survey Open-File Report 78-697.

____1979, Geologic map of the Mount Laguna 

quadrangle, San Diego County, California: U.S. 

Geological Survey Open-File Report 79-862.

Todd, V.R., and Shaw, S.E., 1979, Structural, 

metamorphic and intrusive framework of the 

Peninsular Ranges batholith in southern San 

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Todd, V.R., eds., Mesozoic Crystalline Rocks: 

Guidebook for Geological Society of America 

Annual Meeting, San Diego, California, p. 177- 

231.

____1985, S-type granitoids and an I-S line in the 

Peninsular Ranges batholith, southern 

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San Diego County, California: California 

Division of Mines and Geology, County Report 3, 

109 p.

B13
APPENDIX. Definition of levels of mineral resource potential and 

certainty of assessment

Definitions of Mineral Resource Potential

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 unlikely. This broad 

category embraces areas with dispersed but insignificantly mineralized rock as well as areas with few 

or no indications of having been mineralized.

MODERATE mineral resource potential is assigned to areas where geologic, geochemical, and geophysical 

characteristics indicate a geologic environment favorable for resource occurrence, where interpretations 

of data indicate a reasonable likelihood of resource accumulation, and (or) where an application of 

mineral-deposit models indicates favorable ground for the specified type(s) of deposits.

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.

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

moderate, or high levels of resource potential.

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

area.

Levels of Certainty

U/A

UNKNOWN

POTENTIAL

H/B

HIGH POTENTIAL

M/B

MODERATE POTENTIAL

L/B

LOW

POTENTIAL

H/C

HIGH POTENTIAL

M/C 

MODERATE POTENTIAL

L/C

LOW

POTENTIAL

H/D

HIGH POTENTIAL

M/D

MODERATE POTENTIAL

L/D

LOW POTENTIAL

N/D

NO POTENTIAL

t

o

a.

o 

ac

O c/5

LU 

CC.

A. 

B. 

C. 

D.

B C 

LEVEL OF CERTAINTY

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

Available information suggests the level of mineral resource potential. 

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

Available information clearly defines the level of mineral resource potential.

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. ]., 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.

B14
GEOLOGIC TIME CHART 

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

EON

Phanerozoic

Proterozoic

Archean 

pre -Arc

ERA

Cenozoic

Mesozoic

Paleozoic

Late Proterozoic

Middle Proterozoic

Early Proterozoic

Late Archean

Middle Archean

Early Archean 

:hean 2

PERIOD

Quaternary

Tertiary

Neogene 

Subperiod

Paleogene 

Subperiod

Cretaceous

Jurassic

Triassic

Permian

Carboniferous 

Periods

Pennsylvanian

Mississippian

Devonian

Silurian

Ordovician

Cambrian

 -(3800?)- -

EPOCH

Holocene

Pleistocene

Pliocene

Miocene

Oligocene

Eocene

Paleocene

Late 

Early

Late 

Middle 

Early

Late 

Middle 

Early

Late 

Early

Late 

Middle 

Early

Late 

Early

Late 

Middle 

Early

Late 

Middle 

Early

Late 

Middle 

Early

Late 

Middle 

Early

_ -

AGE ESTIMATES 

OF BOUNDARIES 

(in Ma)

- 0.010

- 1.7

r* A

 oo

*j\j

 CC

- 96 

 100

_ one

£.*f\J

- 290 ^J\J

- ~330

oen

- 410

- 435

cnn

o/u 

- 900

- 1600 

 OKfifi

- 3000

O*TwV7

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

informal time term without specific rank.

B15


GPO 785-048/48050