ARIZONA 
Chapter A 

Mineral Resources of the 

Mount Wilson Wilderness Study Area, 

Mohave County, Arizona 

By ROBERT C. GREENE, ROBERT G. EPPINGER, 

JERRY R. HASSEMER, ROBERT C. JACHENS, and 

WILLIAM A. LAWSON 

U.S. Geological Survey 

GEORGE S. RYAN 

U.S. Bureau of Mines 

U.S. GEOLOGICAL SURVEY BULLETIN 1737 

MINERAL RESOURCES OF WILDERNESS STUDY AREAS: 

BLACK MOUNTAINS REGION, ARIZONA 
DEPARTMENT OF THE INTERIOR 

MANUEL LUJAN, JR., Secretary 

U.S. GEOLOGICAL SURVEY 

Dallas L. Peck, Director 

Any use of trade, product, or firm names 

in this publication is for descriptive purposes only 

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

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1989 

For sale by the 

Books and Open-File Reports Section 

U.S. Geological Survey 

Federal Center, Box 25425 

Denver, CO 80225 

Library of Congress Cataloging-in-Publication Data 

Mineral resources of the Mount Wilson Wilderness Study Area, Mohave 

County, Arizona I by Robert C. Greene . . . [et al.] 

p. em.- (Mineral resources of wilderness study areas-Black 

Mountains Region, Ariz~na ; ch. A)(U.S. Geological Survey bulletin ; 1737-A) 

Bibliography: p. 

Supt. of Docs. no. : I 19.3:1737-A 

1. Mines and mineral resources-Arizona-Mount Wilson Wilderness. 

2. Mount Wilson Wilderness (Ariz.) I. Greene, Robert C. II. Series. 

Ill. Series: U.S. Geological Survey bulletin ; 1737-A. 

QE75.S9 no. 1737-A 557.3 s-dc20 89-600190 

[fN24.A6] [5531.09791 159] CIP 
STUDIES RELATED TO WILDERNESS 

Bureau of land Management Wilderness Study Areas 

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

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

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

Congress. This report presents the results of a mineral survey of the Mount Wilson 

Wilderness Study Area (AZ-020-001A), Mohave County, Ariz. 

CONTENTS 

Summary 

Abstract 

Al 

Al 

Character and setting Al 

Identified resources and mineral resource potential Al 

Introduction Al 

Setting A3 

Previous work and present _study A3 

Appraisal of identified resources A3 

Summary statement A3 

Methods of investigation A3 

Mining history A4 

Appraisal of mineral sites examined A4 

Conclusions and recommendations A4 

Assessment of potential for undiscovered resources AS 

Geology AS 

Geochemistry AS 

Introduction and methods AS 

Results AS 

Interpretation AS 

Geophysics AlO 

Aeromagnetic data AlO 

Gravity data All 

Radiometric data All 

Mineral and energy resources All 

References cited Al2 

Appendixes 

Definition of levels of mineral resource potential and certainty of assessment Al6 

Resource/reserve classification Al7 

Geologic time chart AlS 

FIGURES 

1. Map showing location of Mount Wilson Wilderness Study Area, Mohave County, 

Arizona A2 

2. Map showing mineral resource potential and generalized geology of Mount Wilson 

Wilderness Study Area, Mohave County, Arizona A6 

TABLE 

1. Summary statistics for anomalous elements from the Mount Wilson Wilderness Study 

Area, Arizona A9 

Contents V 

Mineral Resources of the 

Mount Wilson Wilderness Study Area, 

Mohave County, Arizona 

By Robert C. Greene, Robert G. Eppinger, Jerry R. Hassemer, Robert C. Jachens, and 

William A. Lawson 

U.S. Geological Survey 

George S. Ryan 

U.S. Bureau of Mines 

SUMMARY 

Abstract 

The Mount Wilson Wilderness Study Area (AZ020--001 A) comprises 24,821 acres in Mohave County, Arizona. Reconnaissance surveys to determine identified 

(known) mineral resources and mineral resource potential 

(undiscovered) were carried out by the U.S. Bureau of Mines 

and the U.S. Geological Survey in 1984-87. There are no 

identified mineral resources in the wilderness study area. The 

western part of the area south of the summit of Mount Wilson 

has moderate mineral resource potential for lead, zinc, silver, 

and gold in epithermal vein deposits and low mineral resource potential for tungsten in vein deposits. A single locality within this area has a high potential for gold in vein 

deposits. The northern part of the study area, including the 

summit of Mount Wilson, has low mineral resource potential 

for copper, zinc, silver, and gold in epithermal vein deposits 

and low mineral resource potential for tungsten in vein 

deposits. An area just northwest of the study area has low 

mineral resource potential for thorium in pegmatites. The 

study area has no potential for geothermal energy, oil and 

gas, or sand and gravel resources. 

Character and Setting 

The Mount Wilson Wilderness Study Area lies in 

westernmost Arizona, directly southeast of Hoover Dam 

(fig. 1). It is in the Black Mountains, which are part of the 

Basin and Range province of western North America. The 

principal rock units underlying the study area ~e gneiss 

and schist of Precambrian age, overlain on the mountain 

Manuscript approved for publication May 10, 1989. 

flanks by fanglomerate, breccia, and basalt of Tertiary age. 

(See "Appendixes" for geologic time chart.) The northern 

part of the study area is underlain by granodiorite and 

granite of Tertiary age. 

Identified Resources and Mineral Resource 

Potential 

There are no identified mineral resources in the wilderness study area. The western part of the study area south 

of the summit of Mount Wilson (fig. 2) has moderate 

mineral resource potential for lead, zinc, silver, and gold in 

epithermal vein deposits and low mineral resource potential 

for tungsten in vein deposits. A single locality within this 

area has high potential for gold in vein deposits. The 

northern part of the study area, including the summit of 

Mount Wilson, has low · mineral resource potential for 

copper, zinc, silver, and gold in epithermal vein deposits 

and low mineral resource potential for tungsten in vein 

deposits. An area just northwest of the study area has low 

mineral resource potential for thorium in pegmatites. The 

area has no potential for geothermal energy, oil and gas, or 

sand and gravel resources. 

INTRODUCTION 

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

of Land Management (BLM) and is the result of a 

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

U.S. Bureau of Mines. An introduction to the wilderness 

review process, mineral survey methods, and agency 

responsibilities was provided by Beikman and others 

(1983). The U.S. Bureau of Mines evaluates identified 

Mineral Resources of the Mount Wilson Wilderness Study Area, Arizona A 1 
OF 

nl MOUNT WILSON 

c WILDERNESS L, 0 (") STUDY AREA 

I 0 (AZ-020-00 1 A) - 35° I nl 0 

45' / o-; I ,~ ~~ _.... White Hills / 

I ("') 

* rn 

::n 

I OJ AREA OF MAP 

l> 

I "0 mining -1 

nl district 

I Q) ; 

:2 0 

I c 35° z 30' I I -1 

l> 

I "l z 

I 

L.l 

I 

I OJ Q) 

~ ~ 

I ..,.. nl 35° ....1 15' I 

0 10 20 30 MILES 

Figure 1. Map showing location of Mount Wilson Wilderness Study Area, Mohave County, Arizona. 

A2 Mineral Resources of Wilderness Study Areas: Black Mountains Region, Arizona 
resources at individual mines and known mineralized areas 

by collecting data on curent and past mining activities and 

through field examination of mines, prospects, claims, and 

mineralized areas. Identified resources are classified 

according to a system that is a modification of that 

described by McKelvey (1972) and U.S. Bureau of Mines 

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

Survey studies are designed to provide a scientific basis for 

assessing the potential for undiscovered mineral resources 

by determining geologic units and structures, possible 

environments of mineral deposition, presence of 

geochemical and geophysical anomalies, and applicable 

ore-deposit models. Goudarzi (1984) discussed mineral 

assessment methodology and terminology as they apply to 

these surveys. See "Appendixes" for the definition of 

levels of mineral resource potential and certainty of 

assessment and for the resource/reserve classification. 

Setting 

The Mount Wilson Wilderness Study Area (AZ020-001A) is located in Mohave County, Ariz., east and 

south of the Colorado River and directly east of U.S. 

Highway 93 (fig. 1). The area is bounded on all but the 

southeast end by the Lake Mead National Recreation Area, 

and the northernmost part lies 7 mi due east of Hoover 

Dam. Mount Wilson (5,445 ft) is the culminating peak of 

Wilson Ridge, which is part of the Black Mountains, a 

loosely defined range that parallels the Colorado River and 

extends for 110 mi south from the Overton Arm of Lake 

Mead. From the base of Wilson Ridge at about 2,800 ft, 

the land slopes gently eastward to the axis of Detrital 

Valley and more steeply westward to the Colorado River, 

where the elevation is about 800 ft. 

Access to the wilderness study area from the east is by 

two unimproved roads from the Temple Bar road north of 

U.S. Highway 93. Several unimproved roads, mostly dry 

washes, provide proximate access to the western part of the 

wilderness study area. 

Previous Work and Present Study 

Previous geologic mapping in the Mount Wilson area 

consists of reconnaissance work that appears on the geologic maps of Arizona (Wilson and others, 1969; Reynolds, 

1988) and more detailed work on the geologic map of the 

Black Canyon 15-minute quadrangle (Anderson, 1978). 

Anderson's quadrangle map includes most of the wilderness study area, and the geology described in this report is 

largely based on that mapping. Before and during the 

construction of Hoover Dam, the U.S. Bureau of Reclamation commissioned several studies concerning rock structure near the dam site (U.S. Bureau of Reclamation, 1950). 

Previous mineral resources studies include those by 

Schrader (1909), Hewett and others (1936), Longwell 

(1963), and U.S. Bureau of Land Management (1983). 

Limited reconnaissance mapping for the present report 

was carried out in 1986 by W.A. Lawson and R.C. Greene, 

mostly in the northernmost part of the area, which is not 

within the Black Canyon quadrangle. Geochemical sampling and interpretation of results was done by R.G. Eppinger and J .R. Hassemer, and geophysics was done by R.C. 

Jachens. Appraisal of identified resources by G.S. Ryan 

included a review of the literature, investigation of mining 

claim information, and field examination of the study area. 

Final assembly and conclusions were done by R.C. Greene. 

APPRAISAL OF IDENTIFIED RESOURCES 

By George S. Ryan 

U.S. Bureau of Mines 

Summary Statement 

No mineral production has occurred, no mineral resources were identified, and no mineral leases or mining 

claims are present in the study area, although several prospected areas were found. Assays of 38 rock samples taken 

from prospected and mineralized sites during this survey 

indicate anomalous amounts of barium, copper, silver, and 

other elements. The structures in which they occur do not 

appear to be extensive. 

Methods of Investigation 

The U.S. Bureau of Mines investigation included a 

review of literature related to the mineral resources and 

mining activity in and near .the Mount Wilson Wilderness 

Study Area. Mining claim information was checked in the 

BLM claim recordation files; no mining claims are present 

within the study area. Land status plats were obtained from 

the BLM State Office in Phoenix, Ariz. 

Examination of the study area and vicinity by two U.S. 

Bureau of Mines geologists included reconnaissance by 

fixed-wing aircraft, four-wheel-drive vehicle, and foot traverses. Prospects and workings within and near (within 0.5 

mi) the wilderness study area were surveyed and sampled. 

During this study, 38 chip and grab samples were 

collected; 24 of them were fire assayed for gold and silver; 

27 were analyzed for barium, beryllium, and copper by 

inductively coupled plasma-atomic emission spectrometry 

or X-ray fluorescence methods, and 21 were analyzed for 

40 elements by the semiquantitative optical emission spectrographic method (Ryan, 1986). All testing was done by 

the U.S. Bureau of Mines Reno Research Center, Reno, 

Nev. 

Mineral Resources of the Mount Wilson Wilderness Study Area, Arizona A3 
Mining History 

Gold has been mined from Tertiary quartz-sulfide-gold 

veins in the Precambrian metamorphic rocks 10 to 30 mi 

south of the wilderness study area in the Gold Bug mining 

district (U.S. Geological Survey, .1968, p. A4). The highly 

productive Oatman mining district is in the southern part of 

the Black Mountains, 60 mi south of the wilderness study 

area. At Oatman, quartz-adularia-gold veins are found in 

Tertiary volcanic rocks overlying Precambrian metamorphic rocks (Bateman, 1951, p. 431). Most Tertiary volcanic rocks have been eroded from the wilderness study 

area, but Tertiary dikes are common. 

Several prospect pits were found within and near the 

wilderness study area; most are along the western boundary 

near a hypothetical major fault along the west side of 

Wilson Ridge. The prospects are in the granitic rocks 

underlying Mount Wilson in the northern part of the wilderness study area and in the Precambrian metamorphic 

rocks in the southern part. Except at the Two Bs mine, the 

workings consist of small pits, shafts, and adits. Although 

no record of mineral production was found in the literature, 

unpublished U.S. Bureau of Reclamation records show that 

the Two Bs mine was started in the 1930's and work 

continued into the 1950'-s. 

There 1has been no large-scale geophysical prospecting 

in the stutly area because of the restrictive exploration 

policies irdposed by the administration of the Lake Mead 

National Recreation Area. 

Appraisal of Mineral Sites Examined 

Samples were _taken at all of the small pits, shafts, and 

adits found in and adjacent to the study area. Malachite 

and chrysocolla were found in shear zones exposed in 

many prospects. Although copper minerals are readily 

apparent in the prospects, gold was probably the target of 

the early prospectors. Minor amounts of gold or silver are 

found in five of the samples. The highest concentrations 

are in a sample taken from a shaft located on a fault 1.5 mi 

west of Mount Wilson, outside the wilderness study area 

boundary (fig. 2, No. 6); the amounts are 4 parts per 

million (ppm) gold, 9 ppm silv_er, 2.13 percent barium, and 

1.6 percent copper. Anomalously high values of barium (to 

>5,000 ppm), copper (to 15,000 ppm), gold (to 1.25 ppm), 

manganese, and silver (to 2 ppm) are present in many of the 

samples, and beryllium, chromium, nickel, strontium, tin, 

vanadium, and zirconium contents are higher than average 

crustal concentrations (Levinson, 1980, p. 43). 

A 360-ft-long crosscut adit with a 184-ft-long drift is 

present at the Two Bs mine, 0.5 mi west of the wilderness 

study area (fig. 2, Nos. 19-33). The crosscut was evidently 

driven to intercept, at a depth-of about 150ft, a mineralized 

vein of variable width (2 to 10ft) observed on the surface. 

The drift at the end of the crosscut follows the structure that 

correlates up dip with the surface outcrop. Samples 19 to 

22 were taken in the crosscut adit; one sample contains 6.2 

ppm silver. Samples 23 to 31 were taken along the structure exposed in the drift; one sample contains 3.8 ppm gold 

and 6.2 ppm silver, and another contains 5.9 ppm gold and 

3.1 ppm silver. A heavy coating of copper sulfate on the 

walls, especially near the structure, represents the effects of 

the leaching of minerals frof!l the structure and subsequent 

redeposition. 

A 20-ft-deep shaft is located 1.5 mi east-southeast of 

the summit of Mount Wilson (fig. 2, Nos. 9-11). The shaft 

is in a highly magnetic, fine-grained igneous rock body 

about 200 ft2 in area, apparently a zenolith in the granitic 

rocks. Two of the three samples taken from the xenolith 

contain 10 to 29.9 percent iron and 6.2 ppm silver. The 

third sample, taken from a 2-ft-wide vein that is exposed 

over a distance of 35 ft, contains 22.3 percent barium, 0.31 

ppm gold, and 3.1 ppm silver. 

A gold -prospect in the south part of the study area (fig. 

2, No. 34) was being drilled in March 1989. Assays of 

three mineralized rocks collected at the surface in two 

claims show 22, 25, and 31 ppm gold. 

Additional mineral occurrences are aligned along the 

trend of a hypothetical basin-and-range fault lying immediately west of the study area (not shown on fig. 2). This 

alignment suggests that the mineralization could have been 

controlled by such a structure. An apparent extension of 

the fault bounds the east side of the Gold Bug mining 

district to the south (Anderson, 1978). Nearly all mineral 

deposits exploited within the Black Mountains have been in 

either plutonic or volcanic igneous rocks or in metamol]lhic 

rocks (Longwell, 1963, p. E43). Although most of the 

volcanic rocks have been eroded from the northern part of 

the Black Mountains, the underlying Precambrian metamorphic rocks and Tertiary intrusive rocks are similar to 

those found in the Gold Bug and Oatman mining districts. 

Analyses of samples from prospects along the west side of 

the wilderness study area indicate that precious- and basemetal mineralization including gold and silver has occurred. 

Conclusions and Recommendations 

No mineral resources were identified within the Mount 

Wilson Wilderness Study Area . . The mineral occurrences 

present are . discontinuous, small, and of low grade. Because geological conditions are similar to those in the Gold 

Bug and Oatman mining districts, advanced exploration 

techniques such as gravimeter, induced polarization, and 

very low frequency electromagnetic surveys should be used 

to identify any near-surface veins or any massive or disseminated mineral deposits. 

A4 Mineral Resources of Wilderness Study Areas: Black Mountains Region, Arizona 
ASSESSMENT OF POTENTIAL FOR 

UNDISCOVERED RESOURCES 

By Robert C. Greene, Robert G. Eppinger, Jerry R. Hassemer, 

Robert C. Jachens, and William A. Lawson 

U.S. Geological Survey 

Geology 

The Mount Wilson Wilderness Study Area includes 

most of Mount Wilson and Wilson Ridge. This range and 

the rest of the Black Mountains are part of the Basin and 

Range province of western North America, a region characterized by fault-block mountains with intervening alluvium-filled valleys. Wilson Ridge is underlain principally 

by gneiss and schist of Precambrian age, and its flanks are 

underlain by sedimentary and volcanic rocks of Tertiary 

age. Mount Wilson itself is underlain by granitic rocks of 

Tertiary age. 

Three Precambrian rock units are distinguished on 

figure 2. On the east flank of Wilson Ridge, the dominant 

rock is hornblende-biotite gneiss (p-Ch), with local amphibolite or granite pegmatite. Most of the ridge is underlain 

by gray granite gneiss and schist (p-Cm) in alternating 

bands with granite pegmatite and darker hornblende gneiss. 

Highly foliated biotite schist (p-Cs) is present in local fault 

slices. 

Granitic rocks underlying Mount Wilson (Tgr) include 

abundant hornblende-biotite granodiorite and less common 

biotite granite and pyroxene-biotite diorite, all of Tertiary 

age. Border zones are heterogeneous and contain mafic 

plutonic rocks, pegmatite, and aplite. Numerous felsic 

dikes intrude the Precambrian rocks. These are probably 

related to the granodiorite and may be related to mineralization. 

Small areas on the flanks of Wilson Ridge are underlain by the Mount Davis Volcanics of Miocene age. The 

two map units in the study area include mafic lavas and 

flow breccias (Tdm) and rhyodacite and dacite lava and 

flow breccia (Tdr). 

The principal rock unit flanking the sides of Wilson 

Ridge is the Miocene Muddy Creek Formation, which is 

divided into three units on figure 2. Most of the formation 

consists of coarse, poorly sorted fanglomerate (Tms) derived from the metamorphic and granitic rocks upslope. 

Exceptionally coarse debris is mapped as megabreccia 

(Tmm). Locally overlying or interlayered with the sedimentary rocks are flows of black olivine basalt of the 

Fortification Basalt Member (Tmf). 

Unsorted debris of Quaternary alluvial fans and sand 

and gravel in stream courses (Qa) are locally mapped. 

In common with most of the ranges in the Basin and 

Range province, Wilson Ridge is a complex horst, or uplifted block, bounded on both flanks by faults that are 

mostly concealed. According to Anderson (1978), the 

internal structure of the range is complicated by low-angle 

normal faults in the Precambrian rocks. 

Geochemistry 

Introduction and Methods 

In 1987, a reconnaissance stream-sediment geochemical survey of the region including the Mount Wilson Wilderness Study Area was conducted to aid in the mineral 

resource evaluation; 52 stream-sediment, 41 heavy-mineral-concentrate, and 11 altered rock samples were collected and prepared. A stream-sediment sample represents_ 

a composite of rock and soil exposed in the drainage basin, 

whereas a nonmagnetic fraction of the heavy-mineral concentrate (HMC) derived from it is especially useful in detecting mineralized areas because primary and secondary 

ore minerals are commonly concentrated in this fraction. 

The concentration of ore and ore-related minerals in the 

HMC sample facilitates determination of elements that are 

not easily detected in bulk stream sediments. Reconnaissance geochemical studies of this nature are designed for 

recognition of altered or mineralized areas but not for finding individual mineral deposits. A detailed follow-up geochemical study was not undertaken for this study. 

Stream-sediment samples were collected from active 

alluvial channels generally along first-order streams. The 

samples were sieved with 100-mesh screens, and the minus-100-mesh fractions were pulverized for chemical 

analysis. HMC samples were collected from active alluvial 

channels and panned until most quartz, feldspar, clay, and 

organic matter were removed. The HMC samples were 

then sieved with 16-mesh screens, and light minerals remaining in the minus-16-mesh fractions were removed by 

heavy-liquid flotation. The HMC samples were separated 

by an electromagnet into magnetic, slightly magnetic, and 

nonmagnetic fractions. The nonmagnetic fractions were 

examined by microscopic and X-ray diffraction methods to 

determine their mineral content and then were pulverized 

for chemical analysis. Magnetic and slightly magnetic 

fractions were not used in this study. Rocks collected from 

altered zones or prospects were examined microscopically 

and then pulverized for chemical analysis. 

All samples were analyzed for 31 elements (antimony, 

arsenic, boron, barium, beryllium, bismuth, cadmium, calcium, chromium, cobalt, copper, gold, iron, lanthanum, 

lead, magnesium, manganese, molybdenum, nickel, niobium, scandium, silver, strontium, thorium, tin, titanium, 

tungsten, vanadium, yttrium, zinc, and zirconium) by 

semiquantitative emission spectrography. The HMC and 

rock samples were also analyzed for gallium, germanium, 

palladium, phosphorous, platinum, and sodium by the same 

method. Stream sediments were analyzed for arsenic, bismuth, cadmillll!, antimony, and zinc, and rocks for gold, all 

by atomic-absorption methods. Analytical results and a 

Mineral Resources of the Mount Wilson Wilderness Study Area, Arizona AS 
0 

-:r 

" 

Area 3 

L/B Th [3] 

Tgr 

X6 

EXPLANATION 

• Locality having high mineral resource potential (H) for gold 

D Geologic terrane having moderate mineral resource potential (M), for lead, zinc, silver, 

and gold and low potential 

(L) for tungsten 

D Geologic terrane having low mineral resource potential (L) for 

commodities as noted 

Levels of certainty of assessment 

B Data only suggest level of potential 

rever 01 pVl~IIUOl 

[ I Type of occurrence 

1 Epithermal veins 

2 Veins 

3 Pegmatltes 

Commodities 

Ag Silver 

Au Gold 

Cu Copp€r 

Pb Lead 

Th Thorium 

W Tungsten 

Zn Zinc 

Correlation of map units 

ITms 

~ 

frmrTljTmf I 

Unconformity 

~ 

} QUATERNARY 

} TERTIARY 

lp£ml p£s I p£h j } PRECAMBRIAN 

Description of map units 

Oa Alluvium (Holocene) 

Muddy Creek Formation (Mio 

cene) 

Tms Sedimentary rocks, mostly 

fanglomerates Tmm Megabreccla 

Tmf Fortification Basalt Member 

Mount Davis Volcanics (Miocene) 

T dm Mafic lavas and flow breccias 

T d r Rhyodacite and dacite 

Tgr Granitic rocks (Miocene) 

Metamorphic rocks (Precambrian) 

p£m Gneiss, schist, and pegmatite 

p£s Schist 

p£h Hornblende-biotite gneiss 

-Contact 

-Fault 

Areas sampled by U.S. Bureau 

of Mines-Number refers 

to sample noted in text 

X 19-

33 Mine 

Prospect 

Tms 

Area 2 

UC Cu, Zn, Ag, Au, 

LJC W [2] 

114"35' 

Tmf 

Tms 

Figure 2. Mineral resource potential and generalized geology of Mount W ilson W ilderness Study Area, Mohave County, Arizona. 

( 

Qa I 

\ 

Oa 

Oa 

Oa 
description of sampling and analytical techniques were 

supplied by B.M. Adrian (written commun., 1988). 

Frequency distribution diagrams (histograms) were 

constructed for most elements, showing the general distribution and range of the data. Boundaries between background and anomalous element concentrations were chosen 

by inspection of histograms, percentiles, and average crustal abundances for elements given by Levinson (1980). 

Results 

Anomalous concentrations of several elements are 

locally found in samples derived from exposed crystalline 

rock in and adjacent to the wilderness study area. Summary statistics for these elements are provided in table 1. 

Three general areas, defined by clusters of samples having 

unique geochemical associations, are shown on figure 2. 

(1) Numerous samples from a large area extending from the 

west central to the southwestern part of the study area 

contain highly anomalous concentrations of lead, tungsten, 

zinc, and molybdenum. (2) Samples from an area in the 

northern part of the study area are weakly anomalous in 

copper, vanadium, tin, and molybdenum. (3) Samples from 

~mtside and immediately northwest of the wilderness study 

area have anomalous amounts of thorium. 

Area 1 contains 21 stream-sediment and HMC sample 

sites. Anomalous concentrations of elements are found in 

HMC samples as follows: lead (11 samples, 300 to 5,000 

ppm), tungsten (12 samples, 150 to 5,000 ppm), molybdenum (7 samples, 10 to 500 ppm), vanadium (2 samples, 500 

and 1,000 ppm), and antimony (1 sample, 300 ppm). Silver, gold, and bismuth occur in one HMC sample (70 ppm, 

greater than 1,000 ppm, and 700 ppm, respectively) from a 

site draining prospects in the southern part of the area. 

Two small isolated HMC sample sites along the eastern 

edge of the area contain single-element anomalies, one for 

silver (70 ppm) and the other for arsenic (1,000 ppm). 

Stream-sediment samples from area 1 have anomalous 

values of zinc (10 samples, 65 to 125 ppm), molybdenum 

(1 sample, 5 ppm), copper (1 sample, 100 ppm), and lead 

(1 sample, 100 ppm). The highest cadmium concentrations 

are in stream -sediment samples from area 1, but all are less 

than 1 ppm. Gold was detected in three rock samples (0.04, 

0.05, and 1.25 ppm) from the vicinity of the Two Bs mine. 

Other anomalous concentrations of elements in rock 

samples from area 1 include molybdenum, copper, tungsten, arsenic, vanadium, and barium. Trace amounts of 

several ore and ore-related minerals were observed in HMC 

samples from area 1, iiieltrdir(g scheelite, pyrite, malachite, 

wulfenite, vanadinite, cinnabar, gold, and possibly arsenopyrite. Native lead was also observed in four HMC 

samples. 

Eleven HMC samples from area 2 exhibit weakly 

anomalous concentrations of the following elements: 

copper (6 samples, 20 to 30 ppm), tin (6 samples, 30 to 50 

ppm), vanadium (3 samples, 300 ppm), and molybdenum 

(3 samples, 10 to 20 ppm). Anomalous elements in stream 

sediments from area 2 include vanadium (5 samples, 300 to 

500 ppm), zinc (2 samples, 60 ppm), and copper, tin, and 

silver (1 sample each; 200 ppm, 20 ppm, and 2 ppm, respectively. Rock samples from area 2 contain anomalous 

amounts of copper and barium and detectable amounts of 

tungsten, silver, arsenic, gold, molybdenum, and vanadium. 

No ore or ore-related minerals were observed in HMC 

samples from area 2. 

Area 3 encompasses five sample sites northwest of, but 

adjacent to, the wilderness study area boundary. All HMC 

samples_from the sites have anomalous thorium, concentrations ranging from 300 to 2,000 ppm. Thorite was observed in two of the HMC samples. Other anomalous elements in HMC samples include arsenic (1 sample, 2,000 

ppm), molybdenum (2 samples, 10 and 50 ppm), and tungsten (1 sample, 150 ppm). Two stream-sediment samples 

in area 3 contain detectable thorium. 

Anomalous lanthanum and barium are also found in 

numerous samples in the study area. Anomalous lanthanum is generally confined to areas exposing Tertiary plutonic rocks in the northern part of the study area, where 

HMC samples contain 1,500 ppm to greater than 2,000 

ppm. A strong correlation is found in HMC samples between anomalous lanthanum and the occurrence of yellow 

sphene, a rare-earth-element-bearing mineral (Deer and 

others, 1962) and an abundant accessory mineral in Tertiary plutonic rocks in the study area (Anderson, 1978). 

Anomalous amounts of niobium also occur in yellowsphene-bearing HMC samples from the study area. Deer 

and others (1962) report niobium substituting for titanium 

in the sphene lattice. 

In contrast to lanthanum, anomalous concentrations of 

barium are found throughout the study area in samples 

derived from rock types of diverse composition and age. 

_ Barium concentrations are greater than 1 percent in more 

than half of the HMC samples, and barite is commonly 

observed. Some of the barite in HMC samples from the 

central and northern parts of the study area appears to be 

vein fragments, exhibiting alternating bands of barite, 

quartz, and hematite. Barite, quartz, and specularite are 

found in and near veins and shear zones at the mine and 

prospects hosted by both Precambrian and Tertiary rocks in 

the study area (Ryan, 1986). If the barium in the study area 

is due largely to vein barite cutting Precambrian to Tertiary 

rocks, then the abundance of barite found in HMC samples 

suggests that barite veins are widespread throughout the 

study area. Conversely, the barite may come both from 

veins and from crystalline rocks, although barite is not 

mentioned as an accessory mineral in rock units in the 

study area (Anderson, 1978). 

Interpretation 

The lead-zinc-copper-molybdenum-antimony-gold-silver-bismuth-arsenic suite of elements identified in streamsediment, HMC, and rock samples from area 1 is a suite 

A8 Mineral Resources of Wilderness Study Areas: Black Mountains Region, Arizona 
·Table 1. Summary statistics for anomalous elements from the Mount Wilson Wilderness Study Area, Mohave County, 

Arizona 

[Analyses are by semiquantitative emission spectrography, except for elements with "-aa" suffix, which are by atomic-absorption methods. 

Analysts: B.M. Adrian and F.W. Tippitt. Lower limits of analytical determination are shown in parenthesis. Values are in parts per million. 

n, number of samples; N, not detected; L, detected but lower than determination limit] 

Number of 

Element Minimum Maximum 50th Anomalous times detected 

percentile threshold above threshold 

Heavy-mineral concentrates (n=41) 

Silver (1) N 70 N N 2 

Arsenic (500) N 2,000 N N 3 

Gold (20) N >1,000 N N 1 

Barium (50) 70 _>10,000 >10,000 1 

- 1 

-

Bismuth (20) N 700 N N 1 

Copper (10) L 30 L 15 7 

Lanthanum (1 00) L >2,000 300 1,000 15 

Molybdenum (10) N 500 N L 13 

Niobium (50) N 300 N 100 5 

Lead (20) N 5,000 N 150 12 

Antimony (200) N 300 N N 1 

. Tin (20) N 50 N 20 8 

Thorium (200) N 2,000 N 200 8 

Vanadium (20) L 1,000 100 200 5 

Tungsten (50) N 5,000 N 100 10 

Stream sediments (n=52) 

Silver (0.5) N 2 N N 1 

Copper (5) 7 200 30 70 2 

Molybdenum (5) N 5 N N 2 

Lead (10) 15 150 N 70 2 

Tin (10 N 20 N N 1 

Thorium (100) N 200 N :N 3 

Vanadium (10) 70 500 100 200 10 

Zinc (200) N 300 N N 4 

Zinc-aa (5) 10 125 45 60 9 

Rocks (n=ll) 

Silver (0.5) N 2 N N 1 

Arsenic (200) N L N N 2 

Gold-aa -co.02) L 1.25 L L 5 

Barium (20) 20 >5,000 150 3,000 3 

Copper (5) L 15,000 50 500 3 

Molybdenum (5) L 20 5 L 7 

Vanadium (10) 10 300 50 150 2 

Tungsten (20) N 50 L L 3 

1

Threshold not determined for barium; 27 samples contained >10,000 ppm barium 

expected for epithermal base-metal and precious-metal deposits, such as those described by Berger (1982). The 

presence of mercury (in cinnabar, a mercury sulfide), arsenic, and antimony in area 1 suggests low-temperature epithermal deposits. The mine and prospects in area 1 are 

commonly found along local barium-rich quartz veins 

occupying shear zones (Ryan, 1986). Thus, the anomalous 

metals found in this study may be derived from low-ternperature epithermal deposits of similar form. Wulfenite, a 

secondary lead-molybdenum mineral, and vanadinite, a 

secondary lead-vanadium mineral, suggest that oxidized 

parts of the deposits are exposed. Native lead identified in 

four HMC samples from area 1 may have a similar natural 

secondary origin or may be a man-made contaminant. 

Several of the HMC samples containing native lead were 

collected adjacent to an abandoned part of U.S. Highway 

Mineral Resources of the Mount Wilson Wilderness Study Area, Arizona A9 
93; they may be contaminated. Nevertheless, two of the 

samples containing native lead also contain wulfenite, and 

another contains pyrite. While native lead is reported to be 

extremely rare in nature (Palache and others, 1951, p. 102), 

it has appeared in numerous HMC samples from streams 

draining oxidized lead deposits in the southwestern United 

States (P.K. Theobald, written commun., 1988). 

The source of anomalous concentrations of tungsten 

and scheelite in samples from area 1 is unknown. Scheelite 

was found only in HMC samples from sites draining Precambrian metamorphic rocks that locally contain amphibolite and hornblende gneisses (Anderson, 1978). The 

scheelite and associated tungsten-anomalous samples may 

come from disseminated scheelite similar to that found in 

Precambrian amphibolite and calc-silicate gneisses in Colorado (Tweto, 1960), or they may be related to tungsten 

veins similar to those described by Cox and Bagby (1986, 

model 15a). The presence of anomalous concentrations of 

molybdenum is compatible with either possibility. 

Samples from area 2 contain weak concentrations of a 

suite of elements: copper-tin-vanadium-molybdenum, with 

local anomalous zinc, silver, arsenic, and tungsten. The 

low levels for the anomalous elements, coupled with the 

lack of ore or ore-related minerals in HMC samples from 

the area, make this suite difficult to evaluate. All HMC 

samples from the area contain abundant sphene. The 

substitution of some tin and appreciable vanadium for titanium in the sphene lattice (Deer and others, 1962) may 

account for the tin and vanadium anomalies in the area. 

Remaining elements in the suite from area 2 are similar to 

the precious-metal and base-metal epithermal suite identified in area 1. Mineralized quartz, drusy quartz, and chalcedony veins containing barium, copper, lead, zinc, silver, 

and gold, found along shear zones identified at prospects in 

area 2, lend support to epithermal base-metal deposits as 

sources for the metal suite in area 2. 

Because thorite occurs chiefly as a primary mineral in 

pegmatites (Fronde!, 1958), the high concentrations of 

thorium and the thorite identified in area 3 may be derived 

from pegmatites along the border of the Tertiary granitic 

rocks (Anderson, 1978). Arsenic and molybdenum in area 

3 may be related to the epithermal deposits described 

above. However, each of these elements is anomalous only 

in a single sample, and no associated mineral phases were 

identified in HMC samples; hence, assignment of these 

elements to a deposit type would be speculative. 

Geophysics 

Three types of geophysical data from western Arizona 

(magnetic, gravity, and radiometric) were compiled and 

examined to aid in assessment of the mineral resource 

potential of the Mount Wilson Wilderness Study Area. 

Detailed aeromagnetic and radiometric data are available 

along profiles spaced about 1 mi apart. Gravity data coverage is adequate for addressing the regional structural and 

tectonic setting of the study area but is too sparse to permit 

detailed interpretations about mineral resource potential at 

deposit scale. 

Aeromagnetic Data 

An aeromagnetic survey of the Kingman and Las 

Vegas 1° by 2° quadrangles, Calif., Nev., and Ariz., was 

flown in 1977 and compiled by Western Geophysical 

Company of America (1979) under contract to the U.S. 

Department of Energy as part of the National Uranium 

Resource Evaluation program. Data in the Kingman 

quadrangle were subsequently merged with aeromagnetic 

data in adjacent areas by Mariano and Grauch (1988). 

Total-field magnetic data over the study area and surrounding areas of Arizona were collected along east-west flightlines spaced approximately 1 mi apart in the Kingman 

quadrangle and 3 mi apart in the Las Vegas quadrangle, at 

a nominal height of 400 ft above the ground ~urface. 

Corrections were applied to the data to yield a residual 

magnetic field that reflects the distribution of magnetization in the underlying rocks. 

The magnetic field over the study area is characterized 

by a large elongate north-trending magnetic high of 300 to 

500 nanoteslas in amplitude and about 3 mi wide that is 

roughly centered over the crystalline basement rocks exposed in the west half of the study area. The magnetic high 

is well expressed along profiles that cross both the Tertiary 

granitic rocks (Tgr) exposed at the north end of the study 

area and the Precambrian rocks (p£h and p-Cm) exposed to 

the south. This high forms part of a major discontinuous 

linear magnetic high that lies adjacent to and follows the 

Colorado River trough southward for a distance of more 

than 125 mi (Mariano and Grauch, 1988). 

The source rocks for this magnetic anomaly are ambiguous, but three lines of evidence suggest that the high 

primarily reflects Tertiary granitic rocks (Tgr). First, the 

detailed form of the magnetic anomaly itself suggests a 

source in the Tertiary granitic rocks. Profiles that cross 

parts of the study area where the Tertiary granitic rocks 

crop out show, in addition to the broad magnetic high, 

many short-wavelength anomalies that can only be generated by magnetic sources that lie close to the sensor, effectively at the ground surface. Although the long-wavelength 

magnetic high persists on profiles to the south where only 

Precambrian rocks are exposed, the short-wavelength 

anomalies are progressively subdued with increasing distance southward. This behavior is consistent with a magnetic source exposed at the north end of the study area and 

becoming progressively more deeply buried toward the 

south. Second, measurements of the magnetic susceptibility of rock samples show that the average susceptibility of 

five samples of Tertiary granitic rocks is about twice as 

large as the average susceptibility of 30 specimens of 

A 1 0 Mineral Resources of Wilderness Study Areas: Black Mountains Region, Arizona 
Precambrian rock. Within each group, however, the values 

show considerable scatter, and each group contains individual specimens that have susceptibilities large enough to 

account for the anomaly. Third, the form of the geologic 

contact between the Precambrian rocks and Tertiary 

granitic rocks where this contact crosses ridges and canyons along the southwest edge of the exposed Tertiary 

body (Anderson, 1978) suggests that this body continues 

southward beneath the Precambrian rocks. 

On the basis of this evidence and the steepness of the 

gradients on the flanks of the broad magnetic high, we 

interpret the magnetic data to indicate that the entire study 

area is underlain by Tertiary granitic rocks, exposed at the 

north end and buried at a depth of a mile or more near the 

south end. 

Gravity Data 

Gravity data in the vicinity of the Mount Wilson Wilderness Study Area were obtained from Mariano and others 

(1986) and supplemented by 13 new observations collected 

during the spring of 1987. Fourteen gravity measurements 

are from localities within the study area, and detailed profiles exist along the roads that border the area to the east 

and west. The observed gravity data are based on the 

International Gravity Standardization Net datum formulas 

(Telford and others, 1976). Bouguer, curvature, and terrain 

corrections (to a distance of 103.6 mi from each station) at 

a standard reduction density of 2.67 grams per cubic centimeter (g/cm3

) were made at each station to determine 

complete Bouguer gravity anomalies. 

The Bouguer gravity field over the study area and 

surrounding regions reflects not only shallow density distributions but also deep sources that support the topography 

in a manner consistent with the concept of isostasy. To 

isolate that part of the gravity field that arises from nearsurface density distributions, an isostatic residual gravity 

map was constructed from the Bouguer gravity data by 

removing a regional gravity field computed from a model 

of the crustal-mantle interface assuming Airy-type isostatic 

compensation (Jachens and Griscom, 1985). 

The residual gravity field over the study area forms a 

large gravity high of about 20 milligals that has a shape, 

length, and width similar to the magnetic high discussed 

above. The elongate gravity high extends north-south the 

entire length of the study area. Like the corresponding 

magnetic anomaly, it forms part of an extensive linear 

gravity high that follows the Colorado River trough southward for a distance of more than 125 mi. However, the 

gravity anomaly is more continuous. 

The close spatial correlation between the magnetic and 

gravity anomalies, their similarity in shape, and their great 

length suggest that both anomalies have the same source or 

closely related sources. The highest gravity value occurs at 

a station on the exposed Tertiary granitic body, which is 

consistent with a Tertiary granitic source for the gravity 

anomaly as well as for the magnetic anomaly. However, 

the average density of five samples of the Tertiary pluton 

is 0.07 g/cm3 lower than the average density of 30 samples 

of the Precambrian rocks. This apparent contradiction 

could result if the small number of samples of the Tertiary 

pluton are not representative of the entire body, or it could 

be resolved if the Tertiary pluton increases in density with 

depth. Simpson and others (1986) identified mafic Tertiary 

igneous rocks as the source of the continuation of this 

gravity anomaly 90 mi farther south in the Mohave Mountains. 

Radiometric Data 

Radiometric data for the study area were collected at 

the same time and from the same aircraft as the magnetic 

data. Recordings were made of gamma-ray flux indicative 

of radioactive isotopes of potassium, thorium, and uranium. 

No consistent anomalies indicative of thorium or uranium 

having count rates exceeding one standard deviation above 

mean background fluctuations were detected along the 

profiles crossing the study area (Western Geophysical 

Company of America, 1979), thus suggesting that no large 

deposits of these elements exist in the very near surface 

beneath the profiles. However, because gamma rays are 

strongly attenuated during passage through Earth materials, 

these data do not preclude significant concentrations of 

these elements buried more than about 2 ft beneath the 

ground surface or between the 1-mi-spaced profiles. 

Mineral and Energy Resources 

Area 1 (fig. 2) along the western part of the study area 

contains strongly anomalous concentrations of lead, tungsten, molybdenum, and zinc in heavy-mineral concentrate 

and stream-sediment samples and weaker anomalous concentrations of other elements, including silver and gold, as 

indicated above. Area 1 is also located on the north-trending magnetic and gravity highs, features that suggest the 

presence of Tertiary intrusive rocks at shallow depths south 

of the exposures. Numerous Tertiary dikes probably are 

border phases of the shallow intrusive rocks and may be 

conduits for hydrothermal solutions. Veins containing 

copper-, silver-, and gold-bearing minerals are present at 

the Two Bs mine, and a large production of gold and silver 

has come from the Gold Bug and Oatman mining districts 

to the south. Therefore, area 1 has a moderate mineral resource potential, certainty level C, for lead, zinc, silver, and 

gold in epithermal deposits and a low mineral resource 

potential, certainty level C, for tungsten in vein deposits. 

Strongly anomalous concentrations of gold in rock 

samples collected in part of area 1 (fig. 2, No. 34) indicate 

that this locality has a high potential, certainty level C, for 

vein deposits of gold. 

Mineral Resources of the Mount Wilson Wilderness Study Area, Arizona A 11 
Area 2 contains weakly anomalous concentrations of 

copper, tin, vanadium, and molybdenum and some zinc, 

silver, arsenic, and tungsten. The magnetic and gravity 

highs of area 1 extend through area 2 also. Area 2 is 

underlain by Tertiary plutonic rocks with numerous dikes. 

It has a low mineral resource potential, certainty level C, 

for copper, zinc, silver, and gold in epithermal veins and a 

low mineral resource potential, certainty level C, for tungsten in vein deposits. 

Area 3 has yielded heavy-mineral concentrates containing anomalous amounts of thorium and grains of thorite, but it has no thorium radiometric anomaly. Area 3 has 

a low mineral resource potential, certainty level B, for 

thorium deposits in pegmatites. 

There are no known warm springs along Wilson Ridge 

and no volcanic or intrusive rocks of Quaternary age. 

However, there are several warm springs in the canyon of 

the Colorado River about 6 mi west of the study area. That 

area is underlain by the Patsy Mine Volcanics of Miocene 

age, a unit that does not extend into the study area. Because evidence for sufficiently high temperatures for geothermal power is lacking, even near warm springs, the 

study area has no resource potential for geothermal energy, 

certainty level D. 

Because the wilderness study area is underlain by 

high-grade metamorphic and intrusive rocks with a thin 

mantle of volcanic and continental sedimentary rocks on 

the flanks, the area has no mineral resource potential for oil 

and gas (Ryder, 1983, p. C19), certainty level D. 

Such deposits of sand and gravel as exist in stream 

courses on the flanks of Wilson Ridge are small, of poor 

quality, and far from potential markets. Therefore, the 

wilderness study area has· no mineral resource potential for 

sand and gravel, certainty level D. 

REFERENCES CITED 

Anderson, R.E., 1978, Geologic map of the Black Canyon 15-

minute quadrangle, Mohave County, Arizona, and Clark 

County, Nevada: U.S. Geological Survey Geologic Quadrangle Map GQ-1394, scale 1:62,500. 

Bateman, A.M., 1951, Economic mineral deposits, 2d ed.: New 

York, John Wiley, 916 p. 

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

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

Wilderness Study Areas: U.S. Geological Survey Circular 

901, 28 p. 

Berger, B.R., 1982, The geological attributes of Au-Ag-basemetal epithermal deposits, in Erickson, R.L., compiler, Characteristics of mineral deposit occurrences: U.S. Geological 

Survey Open-File Report 82-795, p. 119-126. 

Cox, D.P., and Bagby, W.C., 1986, Descriptive model ofW veins, 

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

U.S. Geological Survey Bulletin 1693, p. 64. 

Deer, W.A., Howie, R.A., and Zussman, J., 1962, Rock-forming 

minerals; v. 1, Ortho- and ring silicates: New York, John 

Wiley, 333 p. 

Fronde!, Clifford, 1958, Systematic mineralogy of uranium and 

thorium: U.S. Geological Survey Bulletin 1064, 400 p. 

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. 

Hewett, D.P., Callahan, Eugene, Moore, B.N., Nolan, T.B., 

Rubey, W.W., and Schaller, W.T., 1936, Mineral resources of 

the region around Boulder Dam: U.S. Geological Survey 

Bulletin 871, 197 p. 

Jachens, R.C., and Griscom, Andrew, 1985, An isostatic residual 

gravity map of California-a residual map for interpretation 

of anomalies from intracrustal sources, in Hinze, W.J., ed., 

The utility of regional gravity and magnetic anomaly maps: 

Tulsa, Okla., Society of Exploration Geophysicists, p. 

347-360. 

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

2d ed.: Wilmette, lll., Applied Publishing, 924 p. 

Longwell, C.R., 1963, Reconnaissance geology between Lake 

Mead and Davis Dam, Arizona-Nevada: U.S. Geological 

Survey Professional Paper 374-E, 51 p. 

Mariano, John, and Grauch, V.J.S., 1988, Aeromagnetic maps of 

the Colorado River region including the Kingman, Needles, 

Salton Sea, and El Centro 1° by 2° quadrangles, California, 

Arizona, and Nevada: U.S. Geological Survey Miscellaneous 

Field Studies Map MF-2023, 5 sheets, scale 1 :250,000; 1 

sheet, scale 1:750,000. 

Mariano, John, Helferty, M.G., and Gage, T.B., 1986, Bouguer 

and isostatic residual gravity maps of the Colorado River 

region, including the Kingman, Needles, Salton Sea, and El 

Centro quadrangles: U.S. Geological Survey Open-File 

Report 86-347, 6 sheets, scale 1:250,000; 1 sheet, scale 

1:750,000. 

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

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

Palache, Charles, Berman, Harry, and Frondel, Clifford, 1951, 

Dana's system of mineralogy, v. 2, 7th ed.: New York, John 

Wiley, 1124 p. 

Reynolds, S.J., 1988, Geologic map of Arizona: Arizona Geological Survey Map 26, scale 1:1,000,000. 

Ryan, G.S., 1986, Mineral investigation of the Mount Wilson 

Wilderness Study Area (AZ-020--00lA), Mohave County, 

Arizona: U.S. Bureau of Mines Open-File Report MLA 

66-86, 15 p. 

Ryder, R.T., 1983, Petroleum potential of wilderness lands in 

Arizona, in Miller, B.M., ed., Petroleum potential of wilderness lands in the Western United States: U.S. Geological Survey Circular 902-C, p. Cl--C22. 

Schrader, F.C., 1909, Mineral deposits of the Cerbat Range, Black 

Mountains, and Grand Wash Cliffs, Mohave County, Arizona: 

U.S. Geological Survey Bulletin 397, 226 p. 

Simpson, R.W., Jachens, R.C., Mariano, John, and Helferty, 

M.G., 1986, Gravity and magnetic studies of the Colorado 

River region, California and Arizona [abs.]: Geological 

Society of America Abstracts with Programs, v. 18, no. 5, p. 

414. 

Telford, W.M., Geldart, L.O., Sheriff, R.E., and Keyes, D.A., 

1976, Applied geophysics: New York, Cambridge University 

Press, 960 p. 

A 12 Mineral Resources of Wilderness Study Areas: Black Mountains Region, Arizona 
Tweto, Ogden, 1960, Scheelite in the Precambrian gneisses of 

Colorado: Economic Geology, v. 55, no. 7, p. 1406-1428. 

U.S. Bureau of Land Management, 1983, Mount Wilson G-E-M 

resources area: Technical Report GRA-A&01, 31 p. 

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

Geological Survey Circular 831, 5 p. 

U.S. Bureau of Reclamation, 1950, Geological investigations, in 

U.S. Bureau of Reclamation, Boulder Canyon Project final 

reports: Bull. 1, pt. 3, 231 p. 

U.S. Geological Survey, 1968, Geological Survey research 1968: 

Professional Paper 600-A, 371 p. 

Western Geophysical Company of America, Aero .Service Division, 1979, Airborne gamma-ray spectrometer and magnetometer survey, Las Vegas quadrangle (Arizona, California, 

Nevada), Williams quadrangle (Arizona), Prescott quadrangle 

(Arizona), and Kingman quadrangle (Arizona, California, Nevada), fmal report: U.S. Department of Energy Open-File 

Report GJBX 59(79), v. 2, variously paged. 

Wilson, E.D., Moore, R.T., and Cooper, J.R., 1969, Geologic map 

of Arizona: Arizona Bureau of Mines and U.S. Geological 

Survey, scale 1:500,000. 

Mineral Resources of the Mount Wilson Wilderness Study Area, Arizona A 13 

APPENDIXES 
DEFINITION OF LEVELS OF MINERAL RESOURCE POTENTIAL 

AND CERTAINTY OF ASSESSMENT 

LEVELS OF RESOURCE POTENTIAL 

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

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

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

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

have been active in at least part of the area. 

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

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

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

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

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

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

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

been mineralized. 

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

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

moderate, or high level of resource potential. 

LEVELS OF CERTAINTY 

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

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

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

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

i 

...J 

< 

~ 

z 

UJ 

1-

0 

c.. 

UJ 

u 

~ 

:::> 

0 

V) 

UJ 

~ 

LL. 

0 

...J 

UJ 

> UJ 

...J 

A 

U/A 

UNKNOWN POTENTIAL 

Abstracted with minor modifications from: 

B c 

H/B H/C 

HIGH POTENTIAL HIGH POTENTIAL 

M/B M/C 

MODERATE POTENTIAL MODERATE POTENTIAL 

UB uc 

LOW POTENTIAL LOW POTENTIAL 

LEVEL O.F CERTAINTY 

D 

H/D 

HIGH POTENTIAL 

M/D 

MODERATE POTENTIAL 

UD 

LOW POTENTIAL 

N/D 

NO POTENTIAL 

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

Taylor, R.B., Stoneman, R.j., and Marsh, S.~., 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. 

A 16 Mineral Resources of Wilderness Study Areas: Black Mountains Region Arizona 
RESOURCE/RESERVE CLASSIFICATION 

IDENTIFIED RESOURCES UNDISCOVERED RESOURCES 

Demonstrated Probability Range 

Inferred 

Measured Indicated Hypothetical Speculative 

I Inferred 

I 

ECONOMIC Reserves 

Reserves 

I I ----~---- ----------- -~-

MARGINALLY Marginal Inferred 

Marginal ECONOMIC Reserves Reserves ____ _l_ ____ I I ----------- -~-

SUB- Demonstrated Inferred 

Subeconomic Subeconomic 

ECONOMIC Resources Resources I I I 

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

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

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

Mineral Resources of the Mount Wilson Wilderness Study Area, Arizona A 17 
GEOLOGIC TIME CHART 

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

EON ERA PERIOD EPOCH 

Holocene 

Quaternary Pleistocene 

Neogene Pliocene 

Cenozoic Subperiod Miocene 

Tertiary Paleogene 

OliRocene 

Subperiod Eocene 

Paleocene 

Cretaceous Late 

Early 

Late 

Mesozoic jurassic Middle 

.Early 

Late 

Triassic Middle 

Early 

Permian Late 

Phanerozoic Early 

Late 

Pennsylvanian Middle 

Carboniferous Early Periods 

Mississippian late 

Early 

Late 

Devonian Middle 

Paleozoic Early 

Late 

Silurian Middle 

Early 

Late 

Ordovician Middle 

Early 

late 

Cambrian Middle 

Early 

Late Proterozoic 

Proterozoic Middle Proterozoic 

Early Proterozoic 

Late Archean 

Archean Middle Archean 

Early Archean 

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - (3800?)- - - - - - - - - - - - - - - - - -

pre-Archean2 

'Rocks older than 570 Ma also called Precambrian, a time term without specific rank. 21nformal time term without specific rank. 

A 18 Mineral Resources of Wilderness Study Areas: Black Mountains Region, Arizona 

AGE ESTIMATES OF 

BOUNDARIES IN 

Ml LLION YEARS (Ma) 

0.010 

1.7 

5 

24 

38 

55 

66 

------ 96 

138 

205 

! 

-240 

290 

-330 

360 

410 

435 

500 

1

-570 

900 

1600 

2500 

3000 

3400 

4550 
SELECTED SERIES OF U.S. GEOLOGICAL SUR EV PUBLICATIONS 

Periodicals 

Earthquakes & Volcanoes (issued bimonthly). 

Preliminary Determination of Epicenters (issued monthly). 

Technical Books and Reports 

Professional Papers are mainly comprehensive scientific reports of 

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

topographic, hydrologic, and geologic investigations. They also include 

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

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

geographic coverage than Professional Papers. They include the results 

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

as collections of short papers related to a specific topic. 

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

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

investigations in all phases of hydrology, including hydrogeology, 

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

Circulars present administrative information or important scientific 

information of wide popular interest in a format designed for distribution 

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

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

publications, and they are also available for public inspection at 

depositories indicated in USGS catalogs. 

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and other material that are made available for public consultation at 

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cited in other publications as sources of information. 

Maps 

Geologic Quadrangle Maps are multicolor geologic maps on 

topographic bases in 7 In- or 15-minute quadrangle formats (scales mainly 1 :24,000 or 1 :62,500) showing bedrock. surficial, or engineering geology. Maps generally include brief texts; some maps include structure 

and columnar sections only. 

Geophysical Investigations Maps are on topographic or planimetric 

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

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

reflect subsurface structures that are of economic or geologic significance. 

Many maps include correlations with the geology. 

Miscellaneous Investigations Series Maps are on planimetric or 

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

present a wide variety of format and subject matter. The series also includes 7 tn.-minute quadrangle photo geologic maps on planimetric bases 

which show geology as interpreted from aerial photographs. Series also 

includes maps of Mars and the Moon. 

Coal Investigations aps are geologic maps on topographic or 

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

Oil and Gas Investigations Charts show stratigraphic information 

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

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

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

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

environmental studies or wilderness mineral investigations. 

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

of geohydrologic data of both regular and irregular areas; principal scale 

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

Catalogs 

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

the conditions indicated below from the U.S. Geologi<:al Survey, Books 

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

CO 80225. (See latest Price and Availability List) 

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

set of microfiche. 

"Publications of the Geological Survey, 1962- ~)70" may be purchased by mail and over the counter in paperback book form and as a 

set of microfiche. 

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

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

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

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

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

over the counter in paperback book form. 

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

Water-SupplyReportsandMapsFor(State),"maybepurchasedbymail 

and over the counter in paperback booklet form only. 

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

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

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

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

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

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

National Center, Reston, VA 22092. 

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

announcements, and publications may be incorrect Therefore, the 

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

and publications.