and Welches Canyon 

Distribution of Minor Elements 

in the Rodeo Creek NE 

and Welches Canyon Quadrangles, 

Eureka County, Nevada 

By JAMES G. EVANS and JOCELYN A. PETERSON 

U.S. GEOLOGICAL SURVEY BULLETIN 1657 
DEPARTMENT OF THE INTERIOR 

DONALD PAUL HODEL, Secretary 

U.S. GEOLOGICAL SURVEY 

Dallas L. Peck, Director 

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON: 1986 

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 

Evans, james George, 1938-

Distribution of minor elements in the Rodeo Creek 

NE and Welches Canyon quadrangles, Eureka County, 

Nevada 

(U.S. Geological Survey Bulletin 1657) 

Bibliography: 

Supt. of Docs. no.: 119.3:1657 

1. Geochemistry-Nevada-Eureka County. 

2. Geology-Nevada-Eureka County. 3. Geochemical 

prospecting-Nevada-Eureka County. I. Peterson, 

Jocelyn A. II. Title. Ill. Series. 

QE75.B9 no. 1657 557.3s 85-600168 

[QE515] s[553.4'09793;32] 85-600168 
CONTENTS 

Abstract 1 

Introduction 1 

Geologic summary 1 

Geology of the deposits 3 

Igneous rocks, aeromagnetic anomalies, and hydrothermal alteration 7 

Age of mineralization 7 

History 10 

Present study 10 

Distribution of elements 11 

Gold 11 

Arsenic 16 

Mercury 17 

Antimony 17 

Copper 18 

Lead 18 

Barium 18 

Barium-strontium relations 19 

Manganese 19 

Molybdenum 19 

Silver 20 

Tin 20 

Tungsten 20 

Zinc 21 

Discussion 21 

Conclusions 25 

References 26 

J!IGURES 

1. Location of Rodeo Creek NE and Welches Canyon quadrangles and adjacent areas 2 

2. Geology of Rodeo Creek NE and Welches Canyon quadrangles 4 

3. Aeromagnetic contours and areas of thermal metamorphism and hydrothermal alteration 8 

4. Locations of samples collected for analysis 12 

5. Sample density contours 14 

6. Locations of samples with gold concentrations greater than or equal to 0.05 ppm 30 

7. Locations of samples with arsenic concentrations greater than or equal to 200 ppm 32 

8. Locations of samples with mercury concentrations greater than or equal to 1 ppm 34 

9. Locations of samples with antimony concentrations greater than or equal to 70 ppm 36 

10. Locations of samples with copper concentrations greater than or equal to 200 ppm 38 

11. Locations of samples with lead concentrations greater than or equal to 100 ppm 40 

12. Locations of samples with barium concentrations greater than or equal to 1,000 ppm 42 

13. Locations of samples with manganese concentrations greater than or equal to 1,000 ppm 44 

14. Locations of samples with molybdenum concentrations greater than or equal to 50 ppm 46 

15. Locations of samples with silver concentrations greater than or equal to 0.5 ppm 48 

16. Locations of samples with tin concentrations greater than or equal to 10 ppm 50 

17. Locations of samples with tungsten concentrations greater than or equal to 50 ppm 52 

18. Locations of samples with zinc concentrations greater than or equal to 200 ppm 54 

19. Areas with anomalous concentrations of gold, arsenic, mercury, antimony, copper, and lead, and 

centers of aeromagnetic anomalies 56 

20. Areas with anomalous concentrations of silver, barium, molybdenum, manganese, tin, tungsten, and 

zinc, and centers of aeromagnetic anomalies 58 

TABLES 

1. Production of gold at the Carlin mine, 1965-1983 10 

2. Number of samples per rock unit 16 

3. Spearman correlation coefficients for the elements that are statistically correlated with one another 

directly or indirectly at a confidence level of 99 percent 16 

4. Distribution of gold in rock units 60 

5. Distribution of arsenic in rock units 60 

6. Distribution of mercury in rock units 61 

III 
7. Distribution of antimony in rock units 61 

8. Distribution of copper in rock units 62 

9. Distribution of lead in rock units 62 

10. Distribution of barium in rock units 63 

11. Distribution of manganese in rock units 63 

12. Distribution of molybdenum in rock units 64 

13. Distribution of silver in rock units 64 

14. Distribution of tin in rock units 65 

15. Distribution of tungsten in rock units 65 

16. Distribution of zinc in rock units 65 

IV 
Distribution of Minor Elements in the Rodeo Creek NE 

and Welches Canyon Quadrangles, Eureka County, 

Nevada 

By james G. Evans and jocelyn A. Peterson 

Abstract 

The Rodeo Creek NE and Welches Canyon quadrangles include the Lynn window of the Roberts 

Mountains thrust. This area is noted for the disseminated gold deposits at the Carlin mine, along the 

northeast margin of the window. The distribution of 

13 elements (Ag, As, Au, Ba, Cu, Hg, Mn, Mo, Pb, Sb, 

Sn, W, and Zn) in the two quadrangles based on 877 

rock samples was studied. Major gold deposits occur in 

a northwest-trending zone of hydrothermally altered 

rock, which may coincide with a Proterozoic or Paleozoic structure, near and along which Cretaceous and 

early Oligocene intrusions were emplaced. Hydrothermal activity associated with each of the intrusions 

may have had a part in development of the zone of 

hydrothermally altered rock, although gold mineralization may not have occurred during each period of 

alteration. 

The 13 elements studied seem to be segregated 

geographically into two groups: (1) Au, As, Hg, Sb, Cu, 

and Pb principally in the Rodeo Creek NE quadrangle 

around the Carlin deposit; and (Z) Ag, Ba, Mn, Mo, Sn, 

W, and Zn in both quadrangles, in the Carlin mine area 

and in the southern Lynn window. This element 

distribution may be due to one or more ore controls, 

including possible element zoning in a geothermal 

system. 

Mass-balance calculations indicate that the gold 

at the Carlin deposit could have been leached from the 

country rock, but magmatic sources cannot be ruled 

out. The gold could have been transported to the 

depositional site during the life of a single geothermal 

system. Geologic evidence, however, points to as 

many as three geothermal systems in the area, 

indicating that the hydrothermal processes for forming 

the deposit may have had low efficiency for 

concentrating metals. 

Gold-placer deposits, probably submarginal, may 

be present in Tertiary and Quaternary sediments east 

and west of the Carlin and Big Six lode deposits and 

downstream from gold-bearing quartz veins in the 

Hanson Creek Formation. 

Indicators for Carlin-type deposits include (1) a 

permeable lithology, especially, but not exclusively, 

the silty dolomitic limestone of the Roberts Mountains 

and Popovich Formations; (Z) broad intersecting fault 

zones, especially those of regional extent; (3) Mesozoic 

and Tertiary intrusions; (4) broad zones of hydrothermally altered rock, especially if these zones 

coincide with (Z); and (5} mercury anomalies in soil 

gas. 

INTRODUCTION 

The Rodeo Creek NE and Welches Canyon 

quadrangles are in the southern Tuscarora Mountains, 

northernmost Eureka County, Nev. (fig. 1). The 

complete autochthonous section of predominantly 

carbonate rocks of Cambrian to Late Devonian age 

exposed in the Lynn window of the Roberts Mountains 

thrust and the large low-grade disseminated-gold 

deposit at the Carlin mine in the northern end of the 

window make this area geologically significant 

(Hardie, 1966; Hausen, 1967; Hausen and Kerr, 1968; 

Akright and others, 1969). The regional geology of the 

area was described in detail by Evans (1974a, b; 1980); 

the geology of the Carlin mine, by Radtke (1973, 1974, 

1981), Radtke and Scheiner (1970), and Radtke and 

others (1980). In this report, significant geologic and 

aeromagnetic features associated with mineralization 

are reviewed and correlated with the distributions of 

13 elements from 877 rock samples in the study area. 

The distribution of the elements is significant in 

showing a pattern that may be explained by element 

zoning in one or more geothermal systems. Massbalance calculations are used to determine feasibility 

of leaching the gold from the country rock and 

concentrating_ it at the Carlin deposit. Mineralization 

guides for disseminated gold deposits are inferred from 

the geologic relations. 

GEOWGIC SUMMARY 

The juxtaposition of carbonate, siliceous, and 

transitional assemblages of rocks along the Roberts 

Mountains thrust in the study area occurred no earlier 

than Late Devonian and Early Mississippian time (fig. 

2). The autochthon exposed in the Lynn window (fig. 1) 

consists of 2,572 m of strata of the carbonate 

assemblage. This section includes the Hamburg 

Dolomite (246 m, Middle and Late Cambrian), the 

Pogonip Group (598 m, Early Ordovician), the Eureka 

Quartzite (508 m, Middle Ordovician), the Hanson 

Creek Formation (325 m, late Middle Ordovician and 

Early Silurian), the Roberts Mountains Formation (473 

m, Middle Silurian to Early Devonian), and the 

Popovich Formation (424 m, Early to Late Devonian). 

The Roberts Mountains and Popovich Formations are 

of particular interest as they host the gold ore at the 

Carlin mine (Radtke, 1981). The allochthon consists 

1 
predominantly of shale and chert with minor amounts 

of quartzite and carbonate rock. The predominantly 

siliceous strata in the allochthon are present in 

imbricate thrust slices, some of which contain more 

than 1,000 m of section. One section, at least 2,470 m 

thick, is north of the Lynn window. The siliceous 

assemblage includes the Ordovician Vinini Formation 

and unnamed Silurian strata. Rocks assigned to the 

transitional assemblage are imbricated with the 

siliceous assemblage in the Roberts Mountains 

allochthon south of the Lynn window. The transitional 

41000' 

I 

116030' 

SANTA RENIA FIELDS 

ROSSI MINE X 

Ba 

BOULDER REEK DEPOSIT 

X 

Au 

BOOTSTRAP MIN~;· 

____ I ___ .~::·Au_ +- )· Bootstrap window ~f· 

U) 

z 

c( 

.... 

z 

;::) 

0 

~ 

assemblage, at least 915 m thick, is mostly limestone 

with chert clasts and minor beds of chert and shale. 

These strata are Late Devonian in age. 

Igneous rocks intrude the Paleozoic sedimentary 

rocks. Some of the igneous rocks have been dated by 

the K-Ar method. Cretaceous granodiorite (121 +5 Ma, 

Hausen, 1967; 128 m.y., Radtke and others, 1980, p. 

644) and quartz monzonite (106+2 Ma, Evans, 1980, p. 

57) produced wide contact metamorphic aureoles (fig. 

3). The radiometric ages of these two intrusions may 

be minimum ages because the rocks near the sample 

ELKO COUNTY 

z 

0 

I;" 

"0 

rn 

116000' 

---------

z Swales 

0 Mountain 

rn window 

z 

0 

BIG SIX MINE rn v ...., 

::.v 

VEINS IN 

HANSON 

CREEK 

FORMATION 

RODEO CREEK NW 

EXPLANATION 

I c:J I Window of carbonate assemblage 

a: 

c( 

u 

U) 

;::) 

.... 

SWAL,ES MOUNTAN NW SWALES MOUNTAIN 

I 

~.ar~:~~. window I 

~OLD 1 

MAGGIE ~RRY' DEPOSIT 

CREEK I 

DEPOSIT I 

z 

(/) 

[\~))ffJ Hydrothermally altered rocks I 

4(1145'1 

WELCHES CANYON SCHROEDER MOJ.JTAIN 

I X Mine or deposit 

I 

Au Gold 

Ba Barium 

I 

I 5 KILOMETERS 

I I I I AREA OF MAP 

I! 

~ eCARLIN t1' 

rt I 

Au 

RAIN DEPOSIT X 

Figlue 1. Location of Rodeo Creek NE and Welches Canyon 7 1/2-minute quadrangles, Nevada, and adjacent 

areas. 

2 
sites are hydrothermally altered, and so the dated 

samples may have been affected by the alteration. 

The granodiorite could conceivably have been 

emplaced earlier than the Cretaceous (Jurassic?). 

Narrow contact aureoles were formed by 

granodiorite (37+0.8 Ma, Evans, 1980, p. 62) and quartz 

latite (36.62:_0. 7-Ma, McKee and others, 1971, p. 41) 

emplaced south of the Lynn window (figs. 1, 3) in the 

early Oligocene. Dikes of intrusive breccia contain 

fragments resembling quartz latite and may, 

therefore, be younger than quartz latite. Andesitic 

dikes of unknown age intrude the siliceous assemblage. 

Cretaceous and Tertiary strata and Qua ternary 

sediments were deposited on older rocks. Cretaceous 

or early Tertiary rhyodacite flows were deposited on 

the siliceous assemblage south of the Lynn window. 

Rhyolitic welded tuff (14.22:_3 Ma, McKee and others, 

1971, p. 41) was deposited just west of the window at 

about the same time as part of the Miocene and 

Pliocene Carlin Formation was deposited on the east 

side of the Tuscarora Mountains. Unnamed late 

Tertiary and Quaternary alluvial deposits are present 

on both sides of the mountains. 

The Antler orogeny, in Late Devonian and Early 

Mississippian time was, probably the earliest period. of 

deformation recorded in the study area (chert clasts in 

Upper Devonian limestone of the transitional 

assemblage). During this orogeny, the allochthonous 

siliceous and transitional assemblages, which were 

brought into the area from the west, were imbricated 

in the upper plate of the Roberts Mountains thrust. 

Major and minor folds, chiefly plunging at low angles 

north-northeast and south-southwest, developed in the 

allochthon during transport (Evans and Theodore, 

1978). The autochthonous carbonate assemblage 

underwent complex faulting, including thrusting. New 

interpretations of the geology of northern Nevada 

indicate that post-Paleozoic thrusting may also have 

had an impact on the structural development of the 

southern Tuscarora Range (Ketner and Smith, 1982; 

Coats and Riva, 1983). In late Paleozoic or Mesozoic 

time, the carbonate assemblage was folded into a 

broad asymmetric anticline plunging 20°, N. 15° W. 

The west limb of the anticline is overturned and thrust 

over the siliceous assemblage along the West Lynn 

thrust. Development of the large north-northwesttrending fold and elongation of the Lynn window in 

that direction may be associated with emplacement of 

Cretaceous granitic rocks. Steep relatively minor 

faults postdate the Antler orogeny, and faulting 

occurred throughout the Mesozoic and Tertiary. The 

longest post-Antler fault is the Tuscarora fault along 

the east side of the Tuscarora Mountains. This fault is 

partly Pliocene in age and may have been involved in 

the development of the basin in which the sediments of 

the Carlin Formation were deposited. 

GEOLOGY OF THE DEPOSITS 

The following geologic synopsis of the deposits is 

taken from the geologic map of the Rodeo Creek NE 

and Welches Canyon quadrangles (Evans, 1974a, b). 

More details of the Carlin and Blue Star deposits are 

available in geologic interpretations of those areas by 

Radtke (1973, 1974). Additional description of the 

Gold Strike deposit is in Morrow and Bettles (1982). 

The description of the nearby Bootstrap deposit is 

from Evans and Mullens (1976). 

The Carlin deposit is present along the northeast 

margin of the Lynn window where the north-northeaststriking Lynn fault intersects a zone of steep faults 

that strike northwest and northeast (fig. 2). The 

deposit lies in the predominantly silty laminated 

dolomitic limestone of the Roberts Mountains and 

Popovich Formations, just below the chert and shale of 

the upper plate of the Roberts Mountains thrust. The 

original sedimentary characteristics of much of the 

host rock have been destroyed by brecciation and 

hydrothermal alteration, which includes silicification 

of carbonate rock, leaching of carbonate minerals, 

argillic alteration, oxidation of carbonaceous material 

and sulfide minerals, and local enrichment of the rock 

in carbonaceous material. In places, as in some of the 

silicified rock, bedding laminae are preserved even 

though the mineralogy of the rock has been drastically 

altered by hydrothermal processes. Intensely altered 

dikes are present throughout the deposit. 

The Blue Star deposit is about 6 km northwest of 

the Carlin deposit, at the northern end of the Lynn 

window (figs. 1, 2). The ore body is along a steep 

north-striking fault that lies between intensively 

hydrothermally altered carbonate rocks presumed to 

have been originally part of the Roberts Mountains 

and (or) Popovich Formations and hydrothermally 

altered chert and shale of the siliceous assemblage. A 

thick zone of adularia-quartz-calc-silicate rock is 

present near the deposit. 

The Gold Strike mine is 3 km north of the Blue 

Star deposit (figs. 1, 2). In the mine area rocks of the 

siliceous assemblage are intruded by a Cretaceous 

granodiorite stock and by latite dikes. Pods of calcsilicate hornfels present along the border of the stock 

are probably pieces of the carbonate assemblage 

brought up during intrusion. The stock has a broad (3 

km) contact-metamorphic aureole. Hydrothermal 

alteration and gold mineralization are present in all 

the rock types in the mine area and are intensely 

developed along faults and breccia zones. 

The Bootstrap deposit is located about 15 km 

northwest of the Carlin mine, at the north end of the 

Bootstrap Window (fig. 1; Evans and Mullens, 1976). 

The Bootstrap window is a horst. The ore body occurs 

on the northeast side of the horst along a steep northstriking fault between brecciated siliceous rock on the 

east and undifferentiated Silurian and Devonian 

carbonate rock on the west. 

The Big Six group of deposits is about 3 km northnortheast of the Carlin deposit, in brecciated chert 

along and near the Lynn fault (figs. 1, 2). The goldquartz veins that constitute the lode deposits supplied 

gold to placer deposits in the area. The formation of 

the Big Six deposits is possibly due to leakage through 

the Roberts Mountains thrust and along the Lynn fault 

of the same mineralizing fluids that were involved in 

forming the Carlin deposit. 

The defunct Richmond camp, shown on a map by 

Emmons (1910, pl. 2), centers around the Cretaceous 

quartz monzonite in the southeastern Lynn window 

(figs. 1, 2). Prospect pits and tunnels are as much as 3 

3 
116"22'30" 

41°00' 

Ts 

SOc DSrm 

116"15' 

RODEO CREEK NE QUADRANGLE 

Of 

SOc 

Of 

~al 

Oal 

Op £h GEOLOGY BY J. G. EVANS 1968-71 

3 KILOMETERS 

Fipe 2. Geologic maps of Rodeo Creek NE and Welches Canyon quadrangles, Nevada. These maps used as base 

for figures 3-20. Explanation on p. 6. 

4 
11fl'l22'30" DSrm 116"15' 

4QG52'30" .-------~>4-~..hr---.---.+T"""''::--~::::....,_......,r-_---r-~__;_--......;.+.,.-~~~r------.----------------, 

> 

w 

.... 

.... 

C( 

> 

a: 

w 

0 

.... 

:) 

0 

CD 

Oal 

Figure Z. Continued. 

3 KILOMETERS 

WELCHES CANYON 

QUADRANGLE 

Oal 

Tc 

01 

SOc 

5 
EXPLANATION FOR FIGURE 2 

Tailings 

lol 

pond Mine 

~ 

~ 

dump at 

Carlin mine 

Alluvium 

~ 

Landslide ~ deposits 

0 

Fanglomerate 

~ Siltsone 

Carlin Formation ~ of Regnier (1960) 

0 

Rhyolitic welded tuff 

Intrusive ~ breccia 

Quartz ~ latite 

Granodiorite ~ 

I TKrd I 

Rhyodacite 

I Kqm I 

Quartz monzonite 

Granodiorite ~ 

} 

Pliocene 

and (or) 

Miocene 

}~lgoceM 

QUATERNARY 

TERTIARY 

} 

TERTIARY 

OR 

CRETACEOUS 

} CRETACEOUS 

SILICEOUS (WESTERN) ASSEMBLAGE TRANSITIONAL ASSEMBLAGE CARBONATE (EASTERN) ASSEMBLAGE 

fSOcl 

~ } SILURIAN AND 

Chert and shale ORDOVICIAN 

Figure Z. Continued. 

6 

• • 

X 

0 }upper Devonian 

Unnamed limestone 

CONTACT 

Brecciated 

~ 

and altered 

carbonate 

rocks 

Popovich Formation 

Undifferentiated ~~ limestone 

DSI, limestone 

DSa, hydrothermally altereCf limestone 

I DSrm I 

Roberts Mountains Formation 

}DEVONIAN 

DEVONIAN 

AND 

SILURIAN 

~ 

~ 

} SILURIAN 

AND 

Hanson Creek Formation ORDOVICIAN 

Eureka ~ Quartzite } ORDOVICIAN 

Pogonip ~ Group 

@] } CAMBRIAN 

Hamburg Dolomite 

FAULT-Dotted where concealed 

THRUST FAULT -Dotted where concealed 

Teeth on upper plate 

LOCATION OF MINE AND (OR) DEPOSIT 
km from exposures of the quartz-monzonite pluton. 

Analyses of rocks from the area indicate that silver 

was the chief exploration target (fig. 15). 

Tunnels and prospect pits dug prior to 1960 are 

present along quartz veins rich in orpiment and realgar 

that occur in the Hanson Creek Formation in the 

northwest Lynn window. Some of these workings may 

date from mining activity in the area early in this 

century. Analyses indicate high gold and silver 

concentrations in these veins. 

IGNEOUS ROCKS, AEROMAGNETIC ANOMALIES, 

AND HYDROTHERMAL ALTERATION 

Concealed granitic rocks underlying parts of the 

study area are inferred from the broad contactmetamorphic aureoles around the small Cretaceous 

intrusions and from the narrower aureoles around the 

Tertiary intrusions (Evans, 1974a, b, 1980). Visible 

contact-metamorphic effects include bleaching, 

recrystallization, and neomineralization. Three 

aeromagnetic highs are present over the inferred 

concealed intrusions (fig. 3): (1) over the Cretaceous 

granodiorite near the Gold Strike mine (1,944 gammas 

max); (2) over the Cretaceous quartz monzonite in the 

southeast Lynn window (2,072 gammas max); and (3) 

over the Tertiary granodiorite and quartz latite 

intrusions in the Welches Canyon area, south of the 

window (2,074 gammas max). The magnetic highs 

reflect concentrations of ferromagnetic minerals and 

strongly suggest that igneous rocks are far more 

widespread at depth than at the surface. 

The large aeromagnetic low along the northeast 

flank of the Lynn window is of interest because the 

Carlin gold deposit lies on its southern edge. The low 

coincides with part of the large northwest-trending 

zone of hydrothermally altered rock. Alteration 

effects are listed above in the description of the 

Carlin deposit. Possible explanations for the low 

include (1) the presence of rock less magnetic than the 

surrounding rock, (2) oxidation of ferromagnetic 

minerals, (3) a topological configuration between two 

aeromagnetic highs (1,944 and 2,072 gammas), or (4) 

magnetic rocks polarized in a reverse sense. Because 

the low is present over hydrothermally altered 

(oxidized) and unaltered sedimentary rock, hypotheses 

(1) and (2) are favored. The effect of hypothesis (3), 

however, cannot be ruled out. Magnetic properties of 

the rocks would have to be measured to determine the 

affect of rock magnetization in development of the 

aeromagnetic low. 

The broad northwest-trending zone of 

hydrothermally altered rock cuts across the southern 

edge of the contact-metamorphic aureole associated 

with the Cretaceous (or Jurassic?) granodiorite. The 

hydrothermal alteration is clearly younger than the 

contact-metamorphic affects because rock which has 

been bleached and recrystallized, apparently as a 

result of contact metamorphism, has been partly 

oxidized, leached of carbonate minerals, argillically 

altered, and silicified. Projected northwest, the zone 

of hydrothermally altered rock aligns with the 

hydrothermally altered Roberts Mountains Formation 

at the south end of the Bootstrap window (fig. 1; Evans 

and Mullens, 1976). The Bootstrap and Boulder Creek 

gold deposits lie close to this zone. Projected 

southeast, the zone aligns with hydrothermally altered 

Silurian and Devonian rocks in the Carlin window (fig. 

1; Evans and Cress, 1972), with the Gold Quarry and 

Maggie Creek gold deposits at the south edge of the 

Carlin window, and with the Rain deposit southeast of 

the town of Carlin (fig. 1). These relations suggest 

that the northwest-trending zone of hydrothermally 

altered rock is nearly continuous in the subsurface for 

about 50 km. This zone coincides with part of the 

Lynn-Pinyon Belt (of mineralization) proposed by 

Roberts (1960, p. B18-B19). Roberts extends the belt 

20 km farther southeast to include the Railroad 

district in the Pinyon window (outside area of figure 

1). 

The Cretaceous quartz monzonite and the 

Tertiary granodiorite intrude along steep northweststriking faults (fig. 2). The South Richmond fault, 

which is intruded by quartz monzonite, has a 

stratigraphic separation of a few thousand meters. 

The Cretaceous granodiorite lies north-northwest of 

the other two intrusions, but no steep northweststriking faults are mapped in its vicini~. The three 

intrusions lie near a line trending N. 25 W. that may 

reflect a major fault in the subsurface. Roberts and 

others (1971, p. 20) consider the northwest-trending 

Lynn-Railroad and other mineral belts in north-central 

Nevada as reflecting probable Proterozoic structures 

(faults?). These belts, however, are drawn trending N. 

45° W. The zone of hJdrothermally altered rock also 

has a trend of N. 45 W. This zone intersects the 

lineament defined by the intrusions at a point just 

northwest of the Blue Star mine. 

AGE OF MINERALIZATION 

Radtke and others (1980, p. 646) and Radtke 

(1981, p. 40) postulated that mineralization at the 

Carlin deposit was late Tertiary in age and suggested 

that the igneous activity responsible for the middle 

Miocene rhyolitic welded tuff (called rhyolite and 

rhyodacite flows by Radtke and others) may have been 

the heat source for the hydrothermal activity. The 

present study revealed no evidence of mineralization 

in the tuff. Geologic mapping (Evans, 1980, p. 70-71) 

indicates that the Carlin deposit is near the east edge 

of the welded tuffs, suggesting that the Miocene 

igneous activity is not close to the Carlin deposit and 

may have had no influence on the northwest-trending 

alteration zone. 

Analyses of rock samples in this study indicate 

that the latest mineralization affected the early 

Oligocene quartz latite; therefore, this mineralization 

must have been post-early Oligocene. However, this 

may have been only one stage of mineralization that 

affected the area. At least three other intrusions 

were emplaced in the study area, each of which could 

have supplied heat to drive a geothermal system 

capable of altering rock and resulting in gold 

deposition. 

A multiperiodic history of the kind we suggest for 

the Carlin deposit may be difficult or impossible to 

unravel by studying a small part of the zone of altered 

7 
3 KILOMETERS 

Figure 3. Aeromagnetic contours and areas of thermal metamorphism (heavy stipple) and hydrothermal alteration 

(light stipple) superposed on geologic map of Rodeo Creek NE and Welches Canyon quadrangles. See figure 2 for 

explanation of geologic symbols. Magnetic contours show total intensity magnetic field of the Earth in gammas 

relative to arbitrary datum (see U.S. Geological Survey, 1967). Contour interval is 10 gammas. Explanation on p. 

10. 

8 
3KILOMETERS 

Figure 3. Continued. 

9 
rock. Vigorous late stages of hydrothermal activity 

affecting previously hydrothermally altered rock may 

obliterate evidence of an earlier event. If the kinds of 

alteration in two or more events are similar, some of 

the effects of the earlier event (such as changes in 

mineralogy or stable isotope distributions) may be 

indistinguishable from the effects of the later event. 

Superposition of differing alteration phenomena could 

also yield intermediate values for some parameters 

(such as K-Ar ages of altered rock). Under such 

circumstances, evidence for the earlier alteration 

events may be found only in the areas away from the 

major altered zones and outside the area involved in 

the latest hydrothermal event. 

Mesozoic disseminated gold deposits are known in 

other parts of Nevada and a history of multistage 

intrusion and mineralization is not unique to the Lynn 

window. A Cretaceous age of mineralization has been 

inferred for the Gold Acres deposit (Wrucke and 

Armbrustmacher, 1975, p. 5), 70 km southwest of the 

Carlin mine, and for the Getchell deposit (Berger and 

Taylor, 1980, p. 597), 160 km southwest of the Carlin 

mine (both deposits outside figure 1 area). In the 

Cortez-Buckhorn area, also about 70 km southwest of 

the Carlin mine, the mineralization is complex. 

According to Wells and others (1971, p. C134), the 

mineralization can be explained in two ways: (1) three 

periods of mineralization coinciding with Jurassic, 

Oligocene, and Miocene periods of intrusion; or (2) 

formation of all deposits at one time, during the 

Miocene or later, with variations in mineralization 

associated with differences in host rocks and (or) depth 

of formation of the deposit. Multistage mineralization 

in the Cortez deposit may have occurred, as suggested 

by the presence of Oligocene quartz porphyry at the 

deposit and a Jurassic quartz monzonite and 

granodiorite intrusion projecting under the mine (Wells 

and others, 1971). Rye and others (1974) concluded 

that at Cortez stable isotopes point to mineralization 

during the Jurassic (galena; sulfur and lead isotopes) 

and Tertiary (gold; a D). 

HISTORY 

Gold was discovered in the Lynn district in 1907 in 

placers in intermittent stream channels draining 

terrain underlain by siliceous rocks immediately north 

of the Lynn window (Johnson, 1973, p. 27). Shortly 

thereafter, lode mining commenced in quartz veins in 

chert and shale of the siliceous assemblage in the 

source area. Total reported gold production of the 

EXPLANATION 

2078 mss Aeromagnetic contours. Contour interval = 10 gammas 

X shows location of measured maximum or minimun High Low intensity 

Areas in which the rocks exhibit low- to high-grade 

thermal metamorphic effects 

Areas in which the rocks exhibit intense hydrothermal 

alteration 

Areas in which the rocks exhibit both thermal metamorphic effects and later hydrothermal alteration 

Figure 3. Cbntinued. 

10 

Lynn district from 1932 to 1961 was 6,644 oz (Roberts 

and others, 1967, p. 93), principally from placer and 

lode deposits in the siliceous assemblage. 

In 1965 the Carlin gold mine, the most important 

mine of the district, began production from low-grade 

disseminated deposits in the intensely fractured 

Roberts Mountains and Popovich formations below the 

Roberts Mountains thrust at the northeast margin of 

the Lynn window. By 1975 production was obtained 

from the siliceous assemblage rocks in the Blue Star 

and Bootstrap areas. By 1982 gold was produced from 

the Maggie Creek deposit and from the Gold Quarry 

deposit in 1983. The Carlin ore body is expected to be 

depleted by 1989, and major gold production in the 

area will switch to the Gold Quarry deposit (fig. 1; 

Skillings, 1984). Gold production of 3,601,200 oz (or 

112 t) for the years 1965-83 (table 1) emphasizes the 

significance of the Carlin deposit. The Carlin deposit 

may be a satellite deposit to the even larger Gold 

Quarry deposit. Reserves at Gold Quarry are 

estimated at 183 million tons of ore averaging 0.043 oz 

of gold per ton, for a total of 244.7 t of gold, of which 

about 44.2 t may not be recoverable (Skillings, 1984, p. 

7). 

PRESENT STUDY 

During geologic mapping in the Lynn window and 

vicinity in 1968-71, 877 samples of mineralized 

hydrothermally altered and unaltered sedimentary, 

igneous, and metamorphic rocks ranging in age from 

Cambrian to Tertiary were collected for chemical 

analysis by J. G. Evans. The analyses were published 

by Evans and Peterson (1980). All the samples were 

analyzed for 29 elements (Ag, As, B, Ba, Be, Bi, Ca, 

~'~'~'~'h,L~M~~'~'~'~p~~' 

Sc, Sn, Sr, Ti, V, W, Y, Zn, and Zr) by spectrographic 

methods (Grimes and Marranzino, 1968) and for Au and 

Table 1 Production of gold at the Carlin mine, 1965-83 

Year 

Amount 

(troy ounces) 

1965------128' 500 

1966------261,000 

1967------337,000 

1968------280' 000 1969------212 ,ooo 

1970------201 ,ooo 

1971------199 '000 

1972------194 '000 

1973------150 '000 

197 4------160 '500 

1975------213 '000 1 

1976------208, ooo2 

1977------215' 1003 

1978------152 '400 

1979------133 '000 

1980------110 '000 1981------136 ,6oo4 

1982------145,1005 

1983------165 ,ooo5 

Total 3,601,200 

Reference 

Ryan, 1966, p. 435 

Ryan, 1968, p. 525 

Do. 

Ryan, 1969, p. 531 

Hoyt, 1971, p. 523 

Hoyt, 1972, p. 536 

West, 1973, p. 541 

West, 1974, p. 571 

West, 1975, p. 560 

West, 1976, p. 607 

West, 1977, p. 673 

West and Butterman, 1979, p. 594 

Butterman, 1980a, p. 429 

Butterman, 1980b, p. 387 

Do. 

Lucas, 1981, p. 358 

Lucas, 1982, p. 369 

Lucas, 1983, p. 375 Lucas, 1984, p. 385 

1Amount includes ore from the Carlin (194,657), 

Blue Star (7,570) and Bootstrap mines (10,773). 2Amount includes ore from the Carlin (183,222), Blue Star (12,716) and Bootstrap (12,062) mines. 

3Amount includes ore from the Carlin and Bootstrap mines. 4Amount includes ore from the Carlin, Maggie Creek, and Blue Star 

mines. 

5Amount includes ore from the Carlin, Maggie Creek, Blue Star and 

Gold Quarry mines. A total of 37,000 ounces came from Gold 

Quarry and ores from several test properties. 
Hg by atomic absorption methods (Vaughn and 

McCarthy, 1964; Thompson and others, 1968). 

Occurrences of Ag, As, Au, Sb, Sn, W, and Zn are 

considered significant in the study area because their 

concentrations are well above crustal abundance. 

Concentrations (in parts per million, ppm) at or above 

the following threshold values are also considered 

significant in the study area: Ba, 1,000 ppm; Cu, 200 

ppm; Hg, 1 ppm; Mo, 50 ppm; Mn, 1,000 ppm; and Pb, 

100 ppm. The distribution of these elements in 

relation to geologic features are described and 

discussed in this report. 

Locations of the sample sites are shown in figure 

4. The density of sample sites is contoured in figure 5 

using a counting circle with an area equal to 1 percent 

of the study area. The contours, in percent-per-1-

percent area, represent sampling densities of O, 1.5, 3, 

6, 9, 12, 15, 18, 21, 24, and 27 samples per square 

kilometer. Sample sites tend to cluster in areas of 

known gold deposits in the northern Lynn window and 

vicinity. The sampling density also reflects the 

abundance of natural and man-made exposures and the 

general visibility of alteration and mineralization. The 

southern and northern parts of the study area have a 

relatively low sample density, which reflects generally 

poor exposures and an absence of visibly altered and 

mineralized rock. Sample density in north-central 

Welches Canyon and west-central Rodeo Creek NE 

quadrangles are about the same (2 percent). Small 

isolated areas in the northeast and southeast corners 

of the study area have a relatively high sample density 

(1 percent) because there are more outcrops. 

Inferences regarding element distributions, as drawn 

from the analytical data, are concluded to be largely 

independent of the sample density because (1) 

geological field observations supply additional 

information bearing on continuity of element 

distributions, (2) the elements found and their 

concentration in the samples are independent of 

sample density, and (3) a hypothetical reduction in the 

number of sample sites in a uniform manner across the 

study area is judged to have little effect on 

determining locations of anomalous concentrations of 

the elements. If fewer samples had been taken, 

however, our confidence in the presence and in the 

size of areas of anomalous concentrations may have 

been reduced. If more samples had been taken, some 

additional areas of anomalous concentrations may have 

been found and, in some cases, some of the areas may 

have merged. 

The samples were divided for this report into 23 

rock units (table 2). Certain units have a greater 

sample density than others; for example, jasperoid and 

quartz latite have high sample densities, whereas shale 

of the siliceous assemblage has a very low sample 

density. 

Threshold values were determined by finding the 

nickpoints of log-log cumulative-frequency diagrams 

or by the analytical value of the 97.5 percentile of the 

sample population, where subpopulations were not 

determinable by the former method (Lepeltier, 1969, 

p. 544-546). 

Strengths of associations between elements were 

determined by Spearman's rank-correlation techniques 

(Siegel, 1956; Lovering, 1963). In this report, 

correlation coefficients greater than 0.50 are 

significant at a 99 percent confidence level. Elements 

having statistically significant correlations are given 

in table 3. 

DISTRIBU'nON OF ELEMENTS 

Gold 

The lower limits of detection used for gold in this 

study are 0.02 ppm for some groups of samples and 

0.05 ppm for other groups. For consistent treatment 

of the analytical data, a lower limit of 0.05 ppm is 

used here for all samples. Because crustal abundance 

of gold is estimated to be 0.003 to 0.005 ppm (Jones, 

1968, p. 3; Jones, 1969; Lee and Yao, 1970, p. 782), 

gold concentrations greater than or equal to 0.05 ppm 

are considered anomalous in this study. 

Gold concentrations greater than or equal to 0.05 

ppm are present in 176, or 20 percent, of the samples 

(table 4). Gold is most abundant in quartz veins in the 

Hanson Creek Formation, although the Carlin gold 

deposit is in hydrothermally altered rocks of the 

Roberts Mountains and Popovich formations; 75 

percent of these quartz vein samples, 25 percent of 

the samples of the Roberts Mountains Formation, and 

22 percent of the samples of the Popovich Formation 

contain concentrations greater than or equal to 0.05 

ppm gold. The proportion of samples with 

concentrations greater than or equal to 0.05 ppm gold 

in rocks from the siliceous assemblage is only slightly 

less than for the Roberts Mountains and Popovich 

Formations. Radtke (1981, p. 107) found that the 

average gold content of oxidized ore at the Carlin 

deposit is 9 ppm (rock units not differentiated). 

Gold is statistically associated with arsenic in 

quartz veins in the siliceous assemblage (0. 78) and the 

quartz veins in the Hanson Creek Formation (0. 73); 

with molybdenum in quartz veins in the Hanson Creek 

Formation (0. 75); with mercury in the Roberts 

Mountains Formation (0.69), and with scandium in the 

Popovich Formation (0. 70) (see table 3). The reason 

for the statistical association of gold and scandium in 

the Popovich Formation is not known. Scandium is not 

discussed further in this report because analytical 

values of the element range from less than 5 to 70 

ppm, consistent with its crustal abundance (Adams, 

1973, p. 567-568). 

According to the results of our sampling, gold is 

concentrated along the northeast edge of the Lynn 

window below a segment of the Roberts Mountains 

thrust and in the Big Six mine area north of the mine 

(fig. 6). Rocks near the northeast-striking Lynn fault 

(Mill fault of Radtke and others, 1980, fig. 3), which 

cuts through the Carlin and Big Six deposits, contain 

concentrations greater than or equal to 0.05 ppm 

gold. These relations suggest that the Lynn fault was 

a major conduit for mineralizing fluids for the two 

deposits. No gold was found in rocks near the fault 

north of the Big Six area. High gold concentrations 

(greater than or equal to 1 ppm) were found in a few 

quartz veins in the Hanson Creek Formation 2 to 3 km 

southwest of the Carlin mine. Relatively high grade 

gold-bearing quartz veins in the Hanson Creek 

Formation may underlie the Roberts Mountains 

11 
.... · 

. -

~--~ -- .. ,,-"~ ... ·· ...• 

. . . 

. . 

. . . 

. ... . ·. 

··. 

. . 

3 KILOMETERS 

Of 

Oat 

Pipe 4. Locations of samples collected for analysis. See figure 2. for explanation of geologic symbols. 

12 
Oa! 

>-

w / 

..J 

3KILOMETERS 

Figure 4. Continued. 

I 

I 

Ool~ 

~ 

~I 

i 

I 

• 

. . Dl 

GEOLOGY BY J. G EVAN~ 1968-71 

13 
3 KILOMETERS 

Pipe 5. Sample density contours superposed onto geologic map of Rodeo Creek NE and Welches Canyon 

quadrangles. Contours 0 (unlabeled), 1/2, 1, 2, 3, 4, 5, 6, 7, 8, and 9 percent per 1 percent area represent sample 

densities of O, 1.5, 3, 6, 9, 12, 15, 18, 21, 24, and 27 samples per square kilometer. See figure 2 for explanation of 

geologic symbols. 

14 
> 

w 

...I 

...I 

c:( 

> 

a: 

w 

0 

Figul-e 5. Continued. 

3 KILOMETERS 

116'15' ---.-...,--~--------

1c 

WELCHES CANYON I 

QUADRANGLE 1 Oal ~ 

-----------\__ ~ 

~ 

~~ 

Tc 

i 

Ool~ -1\ 

~ 

~ b1 

I 

I 

! 

15 
Table Z. Number of samples per rock unit 

Rock unit 

Siliceous assemblage 

Number of 

samples 

Chert ------------------------------ 255 

Quartzite -------------------------- 22 

Shale ------------------------------ 34 

Limestone -------------------------- 21 

Quartz veins ----------------------- 22 

Hamburg Dolomite ---------------------- 40 

Pogonip Group ------------------------- 18 

Eureka Quartzite ---------------------- 18 Hanson Creek Formation 

Dolomite --------------------------- 40 

Quartz veins ----------------------- 28 

Roberts Mountains Formation ----------- 79 

Jasperoid ----------------------------- 108 

Silurian and Devonian limestone ------- 28 

Popovich Formation -------------------- 45 

Transitional assemblage---------------- 12 

Cretaceous granodiorite----------------

Cretaceous quartz monzonite ----------- Cretaceous or Tertiary rhyodacite flows 

Andesitic rocks of unknown age --------

Eocene and Oligocene granodiorite -----

Oligocene quartz latite ---------------

Intrusive breccia --------------------- Miocene rhyolitic welded tuff----------

21 

7 

7 

13 

9 

35 

10 

_2 

877 

Formation at the Carlin deposit. Gold concentrations 

greater than or equal to 1 ppm are present at several 

localities in the Roberts Mountains allochthon. These 

appear to be isolated occurrences not clearly 

indicative of any gold potential. However, their 

presence may be the result of gold mineralization 

through the allochthon from more potentially 

favorable host rock (such as limestone) at depth. 

The relation of the aeromagnetic trough north of 

the Carlin deposit (fig. 3) to gold mineralization is 

uncertain, but the hydrothermally altered rock is 

clearly enriched in gold. Ore bodies smaller than the 

Carlin deposit are present southeast and northwest of 

the Carlin mine in the zone of altered rock. Similar 

ore bodies may be present below the Roberts 

Mountains thrust northwest of the mine and below the 

alluvium of Little Boulder Basin. 

Arsenic 

Arsenic is a relatively rare crustal element 

constituting about 2 ppm in igneous rocks, 4 ppm in 

bottom sediment of the Atlantic Ocean, but from 65 to 

650 ppm in Proterozoic sedimentary iron ores 

(Gualtieri, 1973, p. 53). Average arsenic 

concentrations in most of the rock units of the study 

area are likely to be much less than the 200-ppm lower 

Table 3. Spearman correlation coefficients for the elements that are statistically correlated with one 

another directly or indirectly at a confidence level of 99 percent 

16 

Rock unit 

Siliceous assemblage: 

Quartz veins -----------~ 

Hanson Creek Formation: 

Quartz veins-------------

Roberts Mountains FormationPopovich Formation----------

Hanson Creek Formation: 

Quartz veins-------------

Pogonip Group --------------

Hanson Creek Formation: 

Dolomite-----------------

Quartz veins-------------

Roberts Mountains FormationHanson Creek Formation 

Quartz veins--------------

Jasperoid-------------------

Correlation Degrees Student's 

Element coefficient of freedom t test 

As 

As 

Mo 

Hg 

Sc 

As 

Cu 

Hg 

Pb 

Pb 

As 

Pb 

Sb 

Zn 

As 

Sb 

Sb 

Mo 

Gold 

0.78 

.73 

.75 

.69 

.70 

0.75 

.63 

Copper 

0.66 

.85 

.62 

.63 

.77 

.86 

.64 

.67 

.57 

Lead 

0.84 

Arsenic 

0.66 

10 3-97 

12 3.68 

11 3.84 

39 5.99 

16 3.93 

16 4.51 

21 3.69 

12 3.02 

10 5.06 

19 3.42 

17 3.32 

9 3.56 

12 5.74 

15 3.26 

12 3.11 

23 3.29 

8 4.43 

15 3.43 
limit of detection. Therefore, any concentrations of 

arsenic in amounts detectable by the spectrographic 

method are considered to be anomalous. Maximum 

values of arsenic are as high as 7,000 ppm, the upper 

limit of detection. 

Arsenic concentrations greater than or equal to 

200 ppm are present in 190 (or 22 percent) of the 

samples (table 5). Arsenic is most common in quartz 

veins in the Hanson Creek formation (68 percent) and 

in quartz veins in the siliceous assemblage (59 

percent), and less abundant in quartz latite (43 

percent) and jasperoid (33 percent). The highest 

concentrations of arsenic (greater than 7,000 ppm) 

occur in quartz veins in the Hanson Creek Formation, 

in jasperoid, and in quartz latite. Arsenic is much less 

common and in lower concentrations in the Roberts 

Mountains and Popovich Formations, the two rock 

units comprising the Carlin deposit. Radtke (1981, p. 

109) reported an average arsenic content of 506 ppm 

for unoxidized ore and 405 ppm for oxidized ore at the 

Carlin deposit. Arsenic has a positive correlation with 

gold in quartz veins in the Hanson Creek Formation 

(0. 73) and in quartz veins in the siliceous assemblage 

(0. 78), with silver in quartz veins in the Hanson Creek 

Formation (0. 75), with copper in quartz veins in the 

Hanson Creek Formation (0.63) and in the Roberts 

Mountains Formation (0.67), and with molybdenum in 

jasperoid (0.66) (see table 3). 

Geographic distribution of arsenic in 

concentrations greater than or equal to 200 ppm 

coincides with the distribution of gold in the Carlin 

and Big Six areas and with the small gold deposits west 

and northwest of the Carlin mine (fig. 7). Most arsenic 

is in and near the aeromagnetic trough (fig. 3). 

Exceptionally high concentrations are in quartz veins 

in the Hanson Creek Formation south and west of the 

Carlin mine and in a quartz latite dike south of the 

Lynn window. 

Mercury 

Mercury concentrations greater than or equal to 

0.01 ppm (lower limit of detection) are present in 98 

percent of the samples collected for this study. 

Background values (geometric means) for mercury in 

most rock units in the area range from 0.05 to 0.2 ppm 

(table 6). These values are consistent with crustal 

abundance, calculated at about 0.08 ppm (Bailey and 

others, 1973, p. 407). Higher background values, in the 

0.45 to 8 ppm range, are present in quartz veins, 

jasperoid, and the Roberts Mountains Formation-rock 

units that have undergone extensive mineralization. 

Threshold values of mercury vary from one rock unit 

to another. In general, concentrations greater than or 

equal to 1 ppm seem anomalous. This general 

threshold is 100 times the limit of detection and about 

10 times crustal abundance and the background values 

of many of the rock units. 

Mercury concentrations greater than or equal to 1 

ppm are present in 207 (or 24 percent) of the samples 

(table 6). Mercury is most abundant in quartz veins in 

the Hanson Creek Formation (75 percent) and in 

jasperoid (52 percent), both of which display 

significant mineralization. (Jasperoid is included in 

the zone of hydrothermally altered rock shown as unit 

DSa in figure 2 and by light stippling in figure 3.) 

About one-third of the samples of the Roberts 

Mountains Formation and quartz latite contain 

concentrations greater than or equal to 1 ppm 

mercury. A little more than one-quarter of the 

samples of quartzite (siliceous assemblage) and quartz 

veins (siliceous assemblage), the Popovich Formation, 

and quartz monzonite have anomalous mercury 

concentrations. High mercury concentrations (greater 

than 10 ppm) are present locally in most of the rock 

units named above, as well as in chert and limestone of 

the siliceous assemblage. At the Carlin deposit 

average mercury content of unoxidized ores is 21 ppm 

and of oxidized ores, 18 ppm (Radtke, 1981, p. 80, 

108). Mercury has a positive correlation with gold in 

the Roberts Mountains Formation (0.69) and with 

copper in the Pogonip Group (0.66) (see table 3). 

Our samples showed that mercury concentrations 

greater than or equal to 1 ppm are present in the 

Carlin and Big Six areas and in association with gold in 

the northwest-trending zone of hydrothermally altered 

rock (fig. 8). High concentrations of mercury (greater 

than 10 ppm) are present in and near the aeromagnetic 

trough (fig. 3) and are associated with large gold and 

silver concentrations south and southwest of the Carlin 

mine. A few localities have concentrations greater 

than 10 ppm mercury in the southern Lynn window 

near rocks relatively rich in molybdenum, tungsten, 

and zinc. 

Antimony 

Antimony concentrations greater than or equal to 

70 ppm (lower limit of detection) are present in 164 (or 

19 percent) of the samples collected in the area (table 

7). This concentration is much greater than crustal 

abundance, estimated to be 0.2 to 0.5 ppm, with 

basalts and deep-sea clays containing as much as 1 

ppm (Miller, 1973, p. 47). Therefore, samples with 

detectable amounts of antimony are considered 

anomalous. Some samples have concentrations of 

antimony greater than 10,000 ppm, the upper limit of 

detection. Precise antimony contents were not 

determined for these samples. 

Antimony in detectable quantities is present in 16 

of the rock units in the area (table 7). It is 

proportionally most common in quartz veins in the 

Hanson Creek Formation (93 percent). More than onehalf of the jasperoid samples (55 percent) and about 

one-third of the samples of the Roberts Mountains 

Formation (32 percent) contain concentrations greater 

than or equal to 70 ppm antimony. Less than onequarter of the samples of all other rock units contain 

detectable amounts of this element. High 

concentrations (greater than 10,000 ppm) of antimony 

are present primarily in quartz veins in the Hanson 

Creek Formation; one sample of shale il1 the siliceous 

assemblage contains 10,000 ppm. Average content of 

antimony in unoxidized Carlin ores is 126 ppm and in 

oxidized ores, 95 ppm (Radtke, 1981, p. 83, 109). 

Antimony is statistically associated with copper (0.86) 

and lead (0.84) in quartz veins in the Hanson Creek 

Formation and with copper (0.57) in the Roberts 

Mountains Formation (table 3). 

17 
The distribution of samples with concentrations 

greater than or equal to 70 ppm antimony coincides 

with the occurrence of gold and other elements in the 

Carlin mine and with gold occurrences in the zone of 

hydrothermally altered rock northwest and southeast 

of the mine (fig. 9). Most of these occurrences have 

less than 1,000 ppm antimony. Concentrations greater 

than 10,000 ppm are associated with arsenic and 

barium in the Blue Star area and with gold, silver, 

arsenic, and lead in several combinations south and 

southwest of the Carlin mine in quartz veins in the 

Hanson Creek Formation. Samples containing very 

large concentrations of antimony are generally distant 

from the Carlin mine, although a few are in the 

vicinity of the aeromagnetic trough. 

Copper 

Copper concentrations greater than or equal to 5 

ppm (lower limit of detection) are present in 85 

percent of the samples obtained for this study. 

Background values in 21 rock units are less than or 

equal to 50 ppm (table 8), concentrations consistent 

with the 50 ppm crustal abundance (Cox and others, 

1973, p. 167). The other two units with higher 

background values of copper are quartz veins in the 

Hanson Creek Formation (700 ppm) and quartz latite 

(100 ppm). Threshold values of copper in the study 

area vary by rock unit from less than 100 ppm to more 

than 200 ppm. In this study a general threshold of 200 

ppm was used. 

Copper concentrations greater than or equal to 

200 ppm are present in 76, or 9 percent, of the samples 

(table 8). Thirteen of the rock units have no samples 

showing this much copper. Of the rock units with 

anomalous amounts of copper, quartz veins in the 

Hanson Creek Formation commonly (61 percent) 

contain copper concentrations greater than or equal to 

200 ppm. Copper concentrations greater than or equal 

to 10,000 ppm (upper limit of detection) are present in 

chert and quartz veins in the siliceous assemblage, in 

jasperoid, and in quartz latite. All analyzed samples 

from the Roberts Mountains and Popovich Formations 

show copper concentrations less than or equal to 150 

ppm. Unoxidized ore at the Carlin deposit averages 33 

ppm copper and oxidized ore, 22 ppm (Radtke, 1981, p. 

89, 111). Copper is positively correlated with arsenic 

in quartz veins in the Hanson Creek Formation (0.63) 

and in the Roberts Mountains Formation (0.67), with 

antimony in the same two rock units (0.86 and 0.57, 

respectively), with lead in the Pogonip Group (0.85), in 

dolomite of the Hanson Creek Formation (0.62), in 

quartz veins in the Hanson Creek Formation (0.77). and 

with zinc in quartz veins of the Hanson Creek 

Formation (0.64) (see table 3) . . Samples with copper concentrations greater than 

or equal to 200 ppm are concentrated in the general 

vicinity of the Big Six gold deposit (fig. 10). Locally 

high copper concentrations are present in the Blue Star 

mine area-in association with gold, silver, and 

arsenic-and in the siliceous assemblage northeast of 

the Carlin mine. 

18 

Lead 

Lead concentrations greater than or equal to 10 

ppm (lower limit of detection) are present in 59 percent of the samples collected for this study. 

Background values for 22 of the rock units in the area 

are less than or equal to 30 ppm lead (table 9). These 

are in accord with the 5- to 20-ppm range in igneous 

rocks, the 7- to 20-ppm range for sedimentary rocks, 

and a crustal abundance of 15 ppm (Morris and others, 

1973, p. 317). Quartz veins in the Hanson Creek 

Formation have a much higher background (3,000 

ppm). At the Carlin deposit average lead content in 

oxidized ores is 25 ppm and in oxidized ores range 

from 20 to 51 ppm (Radtke, 1981, p. 86, 111). These 

values are not much greater than the background 

values for samples of the Roberts Mountains 

Formation in this study. However, samples of 

unoxidized ores have as much as 1,500 ppm, and 

oxidized ores, as much as 200 ppm. Threshold values 

are near 100 ppm in most rock units in this study, 

therefore, a general threshold of 100 ppm lead is used 

here. Some samples contain an undetermined amount 

of lead greater than 20,000 ppm (upper limit of 

detection). 

Lead concentrations greater than or equal to 100 

ppm are present in 66, or 8 percent, of the samples 

from the study area (table 9). Quartz veins in the 

Hanson Creek Formation contain proportionally more 

lead in anomalous amounts than any of the other rock 

units (75 percent). Less than one-seventh of the 

samples of the other units contain concentrations 

greater than or equal to 100 ppm lead. Nine of the 

units contain less than 100 ppm. Lead has a positive 

correlation with copper in the Pogonip Group (0.85),in 

dolomite of the Hanson Creek Formation (0.62), and in 

quartz veins in the Hanson Creek Formation (0. 77) and 

with antimony in quartz veins in the Hanson Creek 

Formation (0.84) (see table 3). 

The distribution of samples with anomalous lead 

values coincides in part with samples high in gold and 

other elements at the Carlin mine but is areally more 

restricted. Other samples with anomalous lead values 

are geographically associated with high gold, silver, 

arsenic, and mercury concentrations south and northwest of the mine (fig. 11). The greatest lead 

concentrations are in quartz veins in the Hanson Creek 

Formation away from the Carlin area. 

Barium 

Barium concentrations greater than or equal to 20 

ppm (lower limit of detection) are present in 96 

percent of the samples studied. Background values for 

the rock units in the area vary from a low of 20 ppm in 

the Popovich Formation to a high of 1,500 ppm in 

Tertiary granodiorite (table 10). Fifteen of the rock 

units have background values less than or comparable 

to crustal abundance, estimated to be 300 to 500 ppm 

(Brobst, 1973, p. 77). Of the eight rock units with 

barium concentrations greater than or equal to 700 

ppm background, seven are igneous rocks. Threshold 

values for the rock units are greater than or equal to 

1,000 ppm, which is used here as a general threshold. 
Some samples have barium concentrations greater than 

5,000 ppm (upper limit of detection). 

Barium concentrations greater than or equal to 

1,000 ppm are present in 180, or 21 percent, of the 

samples (table 10). The intrusive rock units have 

proportionally more samples with greater than or 

equal to 1,000 ppm than the other rock units (78 

percent max, Tertiary granodiorite; 38 percent min, 

Cretaceous granodiorite). The average barium content 

of unoxidized ores at the Carlin deposit is 400 ppm; 

oxidized ores average 1,100-1,600 ppm (Radke, 1981, 

p. 90, 112). 

Samples with barium concentrations greater than 

or equal to 1,000 ppm are abundant in areas of high 

gold and arsenic concentrations in the Carlin and Big 

Six areas (vicinity of aeromagnetic trough, see Figure 

3) and in the Blue Star area (vicinity of aeromagnetic 

high 1944, see figure 3). Zones of relatively abundant 

barium are also in the vicinity of the two 

aeromagnetic highs south of the Carlin mine (fig. 12). 

Barium-strontium relations 

Barium-strontium relations were studied at the 

Highland Valley porphyry copper deposits in British 

Columbia by Olade and others (1975); they found that 

Ba/Sr ratios greater than 1 outline mineralized zones 

in the igneous rocks. Although the geologic setting at 

the Lynn window is very different from the porphyry 

copper deposits at Highland Valley, Ba/Sr ratios in the 

study area were obtained in order to determine if they 

define areas of hydrothermal mineralization. Ba/Sr 

ratios were calculated for all samples by assuming an 

average strontium content of 50 ppm for samples with 

less than 100 ppm (lower limit of detection) strontium 

and an average barium content of 10 ppm for samples 

with less than 20 ppm (lower limit of detection) 

barium. The geometric mean values of Ba/Sr ratios 

for the rock units of the area range from 0.5 to 7, with 

19 of the rock units having mean values greater than 

or equal to 1. A geographic plot (not included here) of 

localities with Ba/Sr ratios greater than or equal to 10 

exhibits clusters of sites which closely match the areas 

of high barium concentrations. High Ba/Sr ratios, 

therefore, reflect the relatively high barium 

concentrations in the study area. 

Manganese 

Manganese concentrations greater than or equal 

to 10 ppm (lower limit of detection) are present in 98 

percent of the samples. Background concentrations 

for most of the 23 rock units in the area are less than 

or equal to 1,000 ppm, the estimated crustal 

abundance (Dorr and others, 1973, p. 387). The 

background value exceeds crustal abundance in the 

Hamburg Dolomite (2,000 ppm). Manganese 

concentrations greater than or equal to 1,000 ppm are 

present in 138, or 16 percent, of the samples (table 

11), suggesting that the area sampled may be below 

normal in its manganese content with respect to 

crustal abundance, although not clearly below normal 

with regard to average manganese content for certain 

sedimentary and igneous rocks. Because of the small 

proportion of samples with manganese at and above 

crustal abundance, 1,000 ppm was chosen as a general 

threshold in this study. Some of the samples have 

more than 5,000 ppm (upper limit of detection). 

Manganese concentrations greater than or equal 

to 1,000 ppm are most common in Tertiary 

granodiorite (67 percent), and nearly as common in the 

Hamburg Dolomite (55 percent) and the Pogonip Group 

(56 percent). Among the other 20 rock units, intrusive 

breccia (40 percent) and limestone in the siliceous 

assemblage (38 percent) have anomalous amounts of 

manganese in more than one-third of the samples. 

One-third or less of the samples from the other 18 

rock units have maximum manganese concentrations 

greater than or equal to 1,000 ppm. 

Anomalous concentrations of manganese are 

present in diffuse clusters close to centers of intrusion 

and hydrothermal alteration (fig. 13). The main 

cluster, in and near the Cretaceous quartz monzonite 

intrusion, is partly coincident with areas of anomalous 

molybdenum, tin, tungsten, and zinc. A small cluster 

in the vicinity of the Cretaceous granodiorite is partly 

coincident with areas of anomalous arsenic and 

barium. Anomalous manganese values in the vicinity 

of the Tertiary granodiorite and quartz latite intrusions are close to occurrences of anomalous amounts 

of barium. Manganese concentrations greater than or 

equal to 1,000 ppm are also present in the Carlin and 

Big Six areas and in some rocks near the Lynn fault 

between the two deposits. However, manganese is not 

closely associated with quartz veins and jasperoid, 

which are linked to gold mineralization. At one 

locality in siliceous rocks northeast of the Carlin mine, 

large amounts of copper and manganese are present 

together. 

Molybdenum 

Molybdenum concentrations greater than or equal 

to 5 ppm (lower limit of detection) are present in 246, 

or 28 percent, of the samples studied. Background 

values for rocks in the area are less than 5 ppm, 

consistent with crustal abundance, estimated to be 1 

to 1.5 ppm (King and others, 1973, p. 427). Average 

concentrations of molybdenum at the Carlin mine are 

similar or higher in magnitude: oxidized ores, 3 ppm; 

unoxidized ores, 6 ppm (Radtke, 1981, p. 90, 112). 

Estimated threshold values of the rock units range 

from 5 to 2,000 ppm (table 12), or the entire range of 

analytical values from the sample population. A 

threshold of 50 ppm molybdenum was selected for all 

samples. 

Molybdenum concentrations greater than or equal 

to 50 ppm are present in 36, or 4 percent, of the 

samples collected. Molybdenum is most common and 

in greatest concentrations in the Hamburg Dolomite 

and the Pogonip Group. Molybdenum is statistically 

associated with gold in quartz veins in the Hanson 

Creek Formation (0. 75) and with arsenic in jasperoid 

(0.66) (see table 3). 

Anomalous concentrations are present in the 

southeast Lynn window close to the aeromagnetic high 

2072 (fig. 3), which is associated with quartz 

19 
monzonite (fig. 14). A zone of anomalous molybdenum 

occurrences also lies along a northeast-striking fault 

southeast of the Carlin mine. Few high molybdenum 

occurrences are in the Carlin and Big Six areas. 

Silver 

Because the crustal abundance of silver is 

estimated to be 0.07 ppm (Vinogradov, 1962), amounts 

of silver greater than or equal to 0.5 ppm (lower limit 

of detection) are considered anomalous in this study. 

Silver in detectable amounts is present in 225, or 26 

percent, of the samples collected (table 13). It is most 

abundant and in greatest concentrations in quartz 

veins in the Hanson Creek Formation; 82 percent of 

these samples contain detectable silver and threefourths of these contain greater than or equal to 5 

ppm, to a maximum of 1,500 ppm. A little more than 

one-third of the samples of chert in the siliceous 

assemblage and of the Roberts Mountains Formation 

contain concentrations greater than or equal to 0.5 

ppm silver, reflecting silver mineralization in the 

Carlin and Big Six areas. In this study, however, silver 

does not exceed 10 ppm in chert of the siliceous 

assemblage and 3 ppm in the Roberts Mountains 

Formation. A little less than one-third of the samples 

of the Hamburg Dolomite, of quartz veins in the 

siliceous assemblage, and of jasperoid contain greater 

than or equal to 0.5 ppm silver. Of these units, 

jasperoid contains a maximum of 500 ppm; Hamburg 

Dolomite, 15 ppm; and quartz veins in the siliceous 

assemblage, 2 ppm. The youngest rock unit definitely 

affected by silver mineralization is quartz latite. 

Although intrusive breccia contains silver and may be 

younger than quartz latite, the silver may be in 

previously mineralized quartz latite fragments 

incorporated into the breccia. Unoxidized ores in the 

Carlin deposit average 0.4 ppm; oxidized ores average 

0. 7 ppm (Radtke, 1981, p. 88, 111). Silver has a 

positive correlation with arsenic (0. 75) and copper 

(0.63) in quartz veins in the Hanson Creek Formation 

(see table 3). 

Disseminated deposits of the Carlin type contain 

very small amounts of silver and very large gold/silver 

ratios. At Carlin the average gold/silver ratio is about 

20:1 (Radtke, 1981, p. 88). Ratios in other 

disseminated gold deposits may differ widely from this 

figure. At Gold Acres the ratio is 10:1 (Wrucke and 

Armbrustmacher, 1975, p. 23). Also, gold and silver 

are not statistically associated. Nevertheless, the 

geographic distribution of the two metals suggests a 

close spatial association (figs. 6 and 15). Silver 

occurrences are common in the Big Six and Carlin 

mine areas and near the Lynn fault between the two 

mines and north of the Big Six mine. This distribution 

supports the hypothesis that the Lynn fault was a main 

conduit for mineralizing fluids. Silver contents of 500 

to 1,500 ppm are present in quartz veins in the Hanson 

Creek Formation south and west of the Carlin mine, 

coinciding with scattered relatively high gold 

concentrations in that area. Analyses of these rocks 

show that their gold/silver ratios are very different 

20 

from the Carlin deposit, with, in some places, ratios 

less than 1. Silver is much more abundant than gold in 

the southern Lynn window where the rocks have 

undergone contact metamorphism due to the largely 

concealed quartz monzonite intrusion. Scattered 

occurrences of silver are in the siliceous assemblage 

immediately south of the window. 

Tin 

Tin concentrations greater than or equal to 10 

ppm (lower limit of detection) are present in 45, or 5 

percent, of the samples in 7 of the rock units sampled 

in this study (table 14). Thus, background values of tin 

for most of the rock units are less than 10 ppm, 

consistent with crustal abundance, estimated at 2 to 3 

ppm, although some kinds of rock average 10 or more 

parts per million tin (Sainsbury and Reed, 1973, p. 

641). Threshold for tin in this study is taken to be 10 

ppm. 

Tin concentrations greater than or equal to 10 

ppm are most common in quartz veins in the Hanson 

Creek Formation (53 percent)and in the Hamburg 

Dolomite (40 percent), and less common in dolomite of 

the Hanson Creek Formation (18 percent) and in the 

Pogonip Group (17 percent). 

Tin in detectable quantities is primarily in an area 

north of exposures of the quartz monzonite (fig. 16). 

This area is coincident with areas rich in molybdenum, 

manganese, tungsten, and zinc. High values of tin 

(greater than or equal to 1,000 ppm) coincide with high 

values of gold, silver, lead, antimony, and zinc at three 

localities south of the Carlin mine. Two of these 

localities are high in arsenic and two are high in 

mercury. A locality rich in tin west of the Carlin mine 

is also rich in lead, silver, and zinc. 

Tungsten 

Tungsten concentrations greater than or equal to 

50 ppm (lower limit of detection) are present in 40, or 

5 percent, of the samples collected (table 15). This 

value is much greater than the 1 to 1.3 ppm estimated 

crustal abundance (Hobbs and Elliott, 1973, p. 669). 

Therefore, all samples with detectable amounts of 

tungsten are considered anomalous in this study. 

No tungsten was found in samples of 11 of the 

rock units studied. Of the other units, tungsten 

greater than or equal to 50 ppm is most common in the 

Hamburg Dolomite (25 percent). Although only two 

samples of the Pogonip Group contain tungsten in 

amounts greater than or equal to 50 ppm, the concentration of tungsten in both samples is high (2,000 and 

10,000 ppm). Less than one-seventh of the samples of 

the remaining rock units have tungsten concentrations 

greater than or equal to 50 ppm, to a maximum of 200 

ppm. Unoxidized ores at the Carlin mine average 12 

to 18 ppm tungsten; oxidized ores average 8 to 12 ppm 

(Radtke, 1981, p. 90, 112). 

Samples with high tungsten concentrations (200-

10,000 ppm) are grouped in the southeastern Lynn 

window in the contact metamorphic aureole associated 
with the aeromagnetic high 2072 (fig. 3) and coincide 

with areas high in molybdenum, manganese, tin, and 

zinc (fig. 17)~ Samples with generally low tungsten 

content (less than or equal to 200 ppm) from the Carlin 

and Big Six areas are associated with gold and other 

elements in the northwest-trending zone of hydrothermally altered rock. A diffuse cluster of tungstenbearing samples came from the Blue Star area near the 

aeromagnetic high 1944 (fig. 3), which is related to the 

Cretaceous granodiorite. 

Zinc 

Zinc concentrations greater than or equal to 200 

ppm (lower limit of detection) are present in 209, or 24 

percent, of the samples obtained for this study (table 

16). This concentration is greater than the 65 to 94 

ppm estimated for crustal abundance, but not greater 

than zinc concentrations in some carbonaceous shales 

and dolomites (Wedow and others, 1973, p. 700). Background values for 21 of the rock units in the study area 

are less than 200 ppm. However, the Hamburg 

Dolomite has a background of 200 ppm zinc, and 

quartz veins in the Hanson Creek Formation have a 

background of 1,500 ppm. Concentrations of zinc 

greater than or equal to 200 ppm may be significant, 

although actual threshold values are probably greater 

than 200 ppm. In this study, all samples with 

detectable amounts of zinc are considered anomalous,· 

and some samples contain zinc in amounts greater than 

10,000 ppm, (the upper limit of detection). 

Zinc in detectable quantities is most common in 

quartz veins in the Hanson Creek Formation (86 

percent). Zinc is less abundant in the Hamburg 

Dolomite (53 percent) and in quartz veins in the siliceous assemblage (50 percent). Quartz veins in the 

siliceous assemblage, dolomite and quartz veins in the 

Hanson Creek Formation, jasperoid, and the Popovich 

Formation locally contain zinc in amounts greater than 

or equal to 10,000 ppm. Igneous rocks contain little 

zinc . The relatively high zinc content of the Hamburg 

Dolomite may be of sedimentary or diagenetic origin, 

as in the zinc-rich dolomites mentioned by Wedow and 

others (1973). Unoxidized ores in the Carlin deposit 

average 165 to 185 ppm zinc; oxidized ores average 90 

ppm (Radtke, 1981, p. 111). Zinc is statistically 

associated with copper (0.64) in quartz veins in the 

Hanson Creek Formation (see table 3). 

Clusters of samples with greater than or equal to 

200 ppm zinc were collected from the Carlin and Big 

Six areas and along the Lynn fault (fig. 18). A few 

high concentrations (greater than or equal to 5,000 

ppm) are present in that area. Local high concentrations are in jasperoid northwest of the Carlin mine and 

in quartz veins in the Hanson Creek Formation south 

and southwest of the mine. These high .zinc concentrations are associated with large concentrations of gold, 

silver, mercury, lead, and antimony. A broad cluster 

of zinc concentrations lies in an area of the southeast 

Lynn window north of the Cretaceous quartz 

monzonite intrusion and is partly coincident with zones 

rich in manganese, molybdenum, tin, and tungsten. 

Southwest of the quartz monzonite, partly in the 

siliceous assemblage, a diffuse cluster of zinc-rich 

samples is partly coincident with clusters of silver-rich 

and barium-rich samples. Scattered occurrences of 

zinc with concentrations greater than or equal to 500 

ppm (but with no clear relation to other elements or 

structures) are in the siliceous assemblage in the north 

part of the Rodeo Creek NE quadrangle. Other occurrences in the southeast corner of the Welches Canyon 

quadrangle are close to high concentrations of barium 

(fig. 12), mercury (fig. 8), and silver (fig. 15). 

DISCUSSION 

Areas where clusters of samples contain 

anomalous concentrations of each of the 13 elements 

studied are outlined on figures 19 and 20. The 

elements are divided into two groups on the basis of 

the geographic similarity of the areas in which they 

are present in anomalous concentrations • Areas with 

anomalous concentrations of gold, arsenic, mercury, 

antimony, copper, and lead are present in the Rodeo 

Creek NE quadrangle, and some localities rich in gold, 

arsenic, antimony, mercury, and lead are present in 

both quadrangles (fig. 19). Areas with anomalous 

concentrations of silver, barium, manganese molybdenum, tungsten, and zinc are present in both 

quadrangles (fig. 20). Tin, most of which is in the 

Welches Canyon quadrangle, is included in this suite. 

The partial geographic segregation of the two suites of 

elements has been caused by different hydrothermal 

systems or by structural and (or) physiochemical 

controls but was not likely fortuitous. The segregation 

of the element suites suggests the kind of element 

zoning described by White (1981) for active geothermal 

systems and for epithermal deposits: an upper zone 

with gold dominant, characterized by mercury, antimony, and arsenic and containing minor silver (includes 

thallium and boron) and a lower zone containing much 

silver and base metals (includes selenium, tellurium, 

and bismuth). The two zones may be separated in 

places by a barren zone. In the Lynn window, this kind 

of zoning, with complications, may be present. The 

geographic separation of the zones in the window may 

be due to tilting and erosion during the late Mesozoic 

and Tertiary, or, more likely, the configuration of 

isotherms or conduits of the hydrothermal fluids. 

The source of the gold in the Carlin deposit is not 

known. Dickinson and others (1978) suggested that ore 

fluids could have leached some or all of the gold, as 

well as other elements, from sedimentary carbonate 

rocks beneath the deposit. On the basis of relations of 

stable isotopes, Radtke (1981, p. 134) suggested that 

gold and gangue components were hydrothermally 

leached from the carbonate assemblage of the 

southern Tuscarora Range, from shale and sandstone 

believed to underlie the carbonate section, and from 

igneous rocks. B. R. Doe (in Radtke, 1981, p. 133) 

concluded from lead-isotope ratios in vein barite from 

the Carlin deposit that all or at least part of the lead 

in the veins was derived from the Roberts Mountains 

Formation. Similarly, lead and sulfur isotope relations 

determined for the Cortez deposit by Rye and others 

(1974) were interpreted to favor a gold source in the 

country rock. The reasoning behind these conclusions 

21 
should be examined briefly in order to see whether the 

conclusions are justified. 

Radtke and others (1980) and Radtke (1981, p. 

123, 133) concluded from studies of certain stable 

isotopes that the hydrothermal fluids at the Carlin 

deposit were largely of meteoric origin and did not 

contain significant amounts of co2, sulfur, or barite 

from sources other than marine carbonate rocks, 

because the isotope ratios in certain gangue minerals 

and in altered rocks are like the isotope ratios in fresh 

carbonate rocks. The problem with jumping from 

these conclusions to the hypothesis that the gold was 

also leached from the marine carbonate rocks is that 

the stable isotopes mentioned above do not bear 

directly on the origin of the gold (see Anderson, 1980, 

p. 36-38). Gold from a magmatic source could be 

carried by the hydrothermal fluids while the fluids 

scavenge gangue components from and equilibrate 

stable isotope ratios with the country rock. Therefore, 

with regard to gold origin, stable isotope studies are 

intrinsically inconclusive, if not irrelevant. 

Another approach to the origin of the gold would 

be to show by calculation whether all the gold at the 

Carlin deposit could be obtained by leaching from the 

local sedimentary rocks. The gold that could not be 

derived from the sedimentary rocks would have to 

have a magmatic source. Radtke (1981, p. 135) stated 

that all the gold at the Carlin deposit could have been 

leached from 3,000 t of carbonate rocks, implying an 

unreasonably high gold concentration of at least 3.3 

percent in the source rock. Estimates of volume of 

rock, presumably largely from the Roberts Mountains 

Formation, needed as a source for amounts of As, Ba, 

Cu, Hg, Pb, Sb, and Th found in the Carlin deposit 

were calculated by Dickson and others (1979, p. 107) 

but are not directly relevant to the origin of the gold. 

To some extent calculations of this nature are 

inconclusive because of the number of unknown 

factors. Some of these factors are discussed briefly 

below prior to presenting some trial calculations. 

Figure 3 indicates that, at least at the surface, 

hydrothermal alteration is concentrated in the Roberts 

Mountains and Popovich formations. Hydrothermal 

effects, which may reflect subsurface alteration in 

these two formations, are found in the siliceous rocks 

of the upper plate of the Roberts Mountains thrust. 

The extent of surficial alteration does not seem 

consistent with the model of leaching gold from a 

great thickness of sedimentary rocks beneath the 

deposit unless the zone of hydrothermal alteration is 

narrowly focused along steep faults. The calculations 

below are made for three models: (1) leaching of gold 

only from the Roberts Mountains and Popovich Formations (897 m total thickness); (2) leaching of gold from 

the entire carbonate section of the window (2,572 m); 

and (3) leaching of gold from a vertical block of rock 

of unspecified lithology, having dimensions determined 

by surface exposures of hydrothermally altered and 

mineralized rocks. 

Radtke (1981, p. 135) assumed that the Carlin 

deposit contained 100 t of gold, an amount also 

mentioned by Henley and Ellis (1983, p. 29). A 

prophetic overestimate of production of 4 million 

ounces was given by Dickson and others (1979, p. 

101). An estimate of the gold content is obtained here 

22 

by adding production and reserves. Production 

through 1983 (table 1) was 112 t of gold. Published 

reserves, as of 1984 (Skillings, 1984, p. 6), are 4.5 

million tons (English) of ore containing 0.079 troy 

ounces per ton, or 22.4 t (metric). A total of 134.4 t 

of gold can be accounted for in this way. Some of this 

amount is from the nearby Blue Star, Bootstrap, and 

Maggie Creek deposits (fig. 1). Submarginal gold 

deposits peripheral to the main deposit may account 

for an additional quantity of gold that is irretrievable 

at present. For purposes of the following calculations, 

a total of 140 t of gold is used. 

Radtke and others (1972) reported gold concentrations of 0.06 ppm in two samples of fresh carbonate 

host rock (formation not indicated) at the Carlin 

deposit. However, these values, as well as the values 

of other elements from this class of rock at the 

deposit, are suspect because of the difficulty in 

visually determining what rocks have been completely 

unaffected by mineralizing fluids in a terrane in which 

broad halos of hydrothermally altered rocks are 

characteristic. Most of the samples of unaltered host 

rock studied by Radtke and others (1972) actually 

contained less than 0.02 ppm gold (lower limit of 

detection), but a more exact concentration was not 

determined. The volume of rock necessary to leach 

the amounts of As, Ba, Cu, Hg, Pb, Sb, and '51 found in 

the Carlin deposit range from 0.004 to 6 km (Dickson 

and others, 1979). These figures imply average sourcerock gold concentrations of 0.0086 to 13 ppm. Radtke 

(1981, p. 135) later estimated the gold content of 

possible source rocks at 0.03 ppm. This figure is much 

larger than most gold analyses of modern seawater, 

equals the largest gold content found in marine 

organisms (Jones, 1970), and is much greater than 

average gold content for carbonate rocks (0.002-0.003 

ppm, Jones, 1969, p. 23). Wells and others (1969, p. 

532-536), who proposed a sedimentary origin for the 

gold at the Cortez deposit, found gold-bearing pyrite 

in the "unaltered" Roberts Mountains Formation near 

the deposit. They obtained 0.6 ppm gold in pyrite, 

which was recalculated to 0.006 ppm for the rock as a 

whole, given 1 percent pyrite in the rock. This 

concentration of gold is approximately as high as 

concentrations of gold found in modern seawater and 

in certain marine organisms (Jones, 1970), and two to 

three times the average for carbonate rocks (Jones, 

1969). Mullens (1980, p. 41-42), however, pointed out 

the difficulty in obtaining unaltered host rock near 

epithermal deposits in Nevada and maintained that the 

amount of pyrite in the unaltered Roberts Mountains 

Formation is 0.3 percent. More pyrite than that, he 

suggests, would reflect hydrothermal origin. This 

conclusion impies that the "unaltered" Roberts 

Mountains Formation studied by Wells and others 

(1969) had been slightly mineralized. Assuming 

uniform distribution of gold in the pyrite, the gold 

concentration of unaltered rocks in the Cortez area 

should be closer to the 0.002 ppm value for average 

carbonate rocks. In the calculations below, original 

gold values of 0.002, 0.006, and 0.03 ppm are used. 

Although previous workers cited above have 

suggested that the origin of the gold is leaching from 

rocks beneath the Roberts Mountains Formation, they 

have not indicated what gold values these rocks may 
have had originally. This matter is not addressed here, 

as most rock types have gold values which fall into the 

range 0.002 to 0.03 ppm (Jones, 1969). 

Radtke (1981, p. 135) assumes a 90-percent 

efficiency in leaching of gold from the source 

carbonate rocks but does not indicate how this level of 

efficiency was determined. In the calculations below, 

100-percent efficiency in leaching, transporting, and 

depositing the gold is assumed, although the hydrothermal processes are not likely to be that efficient. 

The volume calculations below would have to be 

increased by an amount that depends on the level of 

efficiency one wishes to assume. 

Densities of carbonate rocks range from about 

1.8 to 2.84 (Heiland 1940, p. 84; Daly and others, 1966, 

p. 23-24). A value of 2. 7 is assumed for the carbonate 

rocks of the Lynn window on the basis of the range of 

density of 2.58 to 2.8 for Paleozoic carbonate rock. 

For simplifying calculations a density of 2. 7 is also 

assumed for the noncarbonate rocks of the Lynn 

window, including rocks beneath the exposed section. 

This density may be somewhat high for parts of the 

section such as the Eureka Quartzite and for some of 

the granitic rocks which may underlie the window. 

Assuming a gold concentrati~H of 0.002 ppm in 

unaltered carbonate rocks, 7x10 t of fresh rock 

would have to be leached to supply 140 t of gold. If 

this amount of leached rocks was entirely in the 

Roberts Mountains and Popovich formations, an area 

underlain by lea~ed rocks of the two formations 

would ~otal 29 km . This compares favorably with the 

25-km estimated area of hydrothermally altered 

rocks in the Rodeo Creek NE quadrangle (includes 

exposed areas and assumed extent of hydrothermal 

alteration concealed by alluvium in Little Boulder 

Basin). However, most of that ~old has to be concentrated in an area of about 3 km around the main pit 

at the Carlin mine, indicating that intensive leaching 

may have been more restricted. 

If the gold concentratiofb of the unaltered source 

rocks was 0.006 ppm, 2.3x10 t of rock would have to 

be leached of gold. Deriving the gold from the 

Roberts Mountains an1 Popovich Formations would 

result in at least 9.6 km of ground underlain by hydrothermally altered rock of the two formations. If the 

gold c~ncentration of the source rocks was 0.03 ppm, 

4. 7x10 t

2

of rock would have to be leached, resulting 

in 1.9 km of hydrothermally altered terrane underlain 

by the two formations. Although the two larger gold 

concentrations for source rocks result in figures for 

the surficial extent of hydrothermally altered rocks 

that are more in line with the geologic evidence, these 

gold values are probably too high for the fresh rocks. 

Performing the same calculations utilizing a 

model requiring leaching of gold from strata 

equivalent to the entire exposed section of the Lynn 

window reduces the lateral extent of hydrothermal 

alteration to be expected. With an initial gold concentration of 0.002 ppm in the source rozks, hydrothermal 

alteration would underlie only 10 km ; with 0.006 ppm 

initial gold concent2ation, only 3.3 ~m 2; and with 0.03 

ppm, only 0. 7 km . The 10-km figure is nearly 

consistent with the geologic evidence and can be 

reduced by including leaching of gold from rock units 

that may underlie the exposed carbonate section. In 

this case it would not be necessary to resort to geologically unlikely gold values in the source rocks. The 

only possible problem with including rocks beneath the 

exposed section as part of the gold source is that one 

cannot be sure whether these rocks are sedimentary or 

igneous (or metamorphic), as there are shallow intrusions north and south of the Carlin deposit and possibly 

also beneath it. In addition, it is not known whether 

one or more intrusions has shouldered aside a 

substantial part of the carbonate section not far below 

the deposit. Further, the question is left unresolved as 

to whether the gold has a magmatic source or was 

derived by lateral secretion, because either hypothesis 

could be consistent with a shallow intrusion. 

By trying to leach the gold from a vertically 

bounded block of ground irrespective of lithology, one 

can calculate the depth to which the rock would have 

to be leached of gold. Using an initial gold concentration of 0.002 p~ and assuming that the entire 1.6 by 

16 km (25.6 km ) alteration zone from the east side of 

the Tuscarora Range to the Bootstrap deposit (fig. 1) is 

a potential source region, leaching would have to 

extend downward at least 1 km, a reasonable depth for 

a hydrothermal system. However, most of the goli 

may have come from a column of rock, with a 3-km 

cross section, extending downward in2 the vicinity of 

the main pit. Using the figure of 3 km for the area of 

a column of leached rock, the zone of leaching would 

extend to a depth of 8.6 km. This is close to, but 

slightly exceeds, the lower limit of hydrothermal 

systems (Henley and Ellis, 1983). Changing initial 

assumptions such as the initial gold concentration of 

the source rock and the cross-sectional area of the 

rock column would decrease the depth of the alteration zone. Given the possibility of shallow intrusions 

in the area, it seems likely that the zone of leaching 

would intersect a concealed pluton. The origin of the 

gold would then be indeterminate because the gold 

could have had a magmatic source or could have been 

leached from the plutonic rock. 

Seward (1973) suggested that a significant proportion of gold could be transported by thio complexes in 

hydrothermal ore solutions. Using his experimen!ally 

determined solubility of 0.0225 ppm, 6.22 km of 

water would be needed to tranport 140 t of gold in 

solution. Weissberg (1969, p. 104) found gold concentrations of 0.00004 ppm in certain thermal waters in 

New Zealand that were forming ore-grade 

precipitates. This low concentration is not necessarily 

the same as would be found in all other thermal environments. However, this figure can be used as a lower 

limit for purposes of comparison. If the hydrothermal 

fluids that formed the Carlin deposi! carried no more 

than 0.00004 ppm, about 3,500 km of water would 

have to pass through the site of the deposit. To determine whether this amount of water can reasonably 

flow through the Carlin deposit in a single geothermal 

cycle requires examination of the duration of geothermal systems in general and discharge rates of 

known geothermal systems. 

Silberman and others (1979) examined geologic 

evidence for the duration of geothermal and oreforming epithermal systems. The timespans range 

from 1 to 3 million years. Cathles (1981) constructed 

cooling curves for plutons and concluded that, for the 

23 
conductivities he selected, no intrusion at 800° C can 

maintain an anomaly greater than 200° C within 5 km 

of the surface for more than 4 m.y. For purposes of 

this report, two cases are examined: (1) that the gold 

was deposited during one geothermal system that 

lasted for 3 million years, the maximum duration based 

on geologic evidence, and (2) that gold was deposited 

at least three times, twice during the Cretaceous and 

once during the Tertiary, coincident with the three 

intrusive periods for which geologic evidence is available in the study area. (The two Tertiary intrusions 

overlap in time and, for purposes of these calculations, 

are considered to be a single intrusive period.) Each 

period is assumed to have resulted in a geothermal 

system lasting 3 million years. 

It is not known whether the geothermal system or 

systems that occurred in the Carlin area vented at the 

surface. Radtke and others (1980, p. 646) suggested 

that 305 to 518 m of overlying rock were eroded away 

during the late Tertiary after the latest period of 

mineralization, and no evidence of surface springs 

remains. However, the fluids carrying the gold must 

have flowed generally upward toward the paleosurface 

and may be considered as discharge even if the water 

was ultimately recycled to the convective geothermal 

system. 

Natural discharges from identified conv~ction 

systems range from less than 0.001 to 5. 7 m /min 

(Renner and others, 1975, p. 5-57; Brook and others, 

1979). Discharges from Steamboat Springs, Nevada 

and Sulphur Bank, California are of particular 

interest. The Steamboat Springs geothermal area is 5 

km northwest of the Comstock Lode district 

(Thompson ~nd White, 1964). Siliceous mud 

precipitated in fissures below the water table in the 

Steamboat Springs area contains as much as 10 ppm 

gold (White, 1967, p. 594). White (1968, p. C87) estim!ted discharge for the Steamboat Springs area at 4.5 

m /min; 36 percent of this discharge is from 

geothermal wells. The Sulphur Bank mine is the most 

productive mineral deposit in the world that is closely 

related to hot springs (White and Roberson, 1962, p. 

398). Sims and White (1981, p. 238) estimated discharge3 from the Sulphur Bank mercury mine area at 

1.1 m /min. These discharge rates must be used 

cautiously as standards of comparison because there is 

no way of knowing if these are close to averages for 

their systems. At least these discharge rates can be 

used to indicate possible magnitudes of natural discharges. 

If the gold at the Carlin mine was deposited 

during a geothermal cycle lasting 3 million years, 

average :fischarge of water would have to be at least 

2,070 m /yr if the water carried as much as 0.0225 

ppm gold. This is very low compared to the yearly 

natural flow of 1.83million m 3 /yr at Steamboat Springs 

and 0.6 million m /yr at Sulphur Bank. Even if the 

hypothetical Carlin geothermal system lasted only 1 

million years, the flow required to deposit the gold 

would be many orders of magnitude smaller than many 

natural discharges. The hydrothermal system responsible for deposition of the gold, however, may have 

been a subsystem of a much more extensive 

geothermal system with a total discharge much 

greater than needed to form the Carlin deposit. If the 

24 

work was done by all three of the geothermal systems 

that may have affected the area, the efficiency in 

concentrating the gold by the three systems could have 

been very low. If the thermal waters that circulated 

through the Carlin deposit carried 0.00004 ppm gold, 

a~ual discharge would have to be at least 1.2 million 

m over a 3 mqlion-year-long geothermal system, and 

0.39 million m for three geothermal systems, each 

lasting 3 million years. The greater discharge rate is 

still less than the one at Steamboat Springs, suggesting 

that even with very low gold concentrations in 

solution, one geothermal system may have been able to 

do the work of transporting the gold to the 

depositional site. 

Although the calculations outlined above are 

inconclusive, they suggest (1) that the gold at the 

Carlin deposit could have been leached from the 

country rock, although magmatic sources cannot be 

ruled out, and (2) that the work of leaching and transporting the gold to the deposit could have been 

performed by a single, relatively inefficient 

geothermal system, even though geologic evidence 

suggests that at least three systems could have 

developed in the area. These conclusions may apply to 

the larger Gold Quarry deposit (Skillings, 1984, p. 7). 

However, we do not have the geological information 

about the deposit necessary to model deposit geometry 

and calculate masses. 

Because gold-bearing rock was eroded from the 

upper part of the Carlin deposit and nearby areas, 

including the Big Six deposit, gold placer deposits 

should be present near the lode deposits. Gold placers 

are present in Lynn, Rodeo, Sheep, and Simon Creeks 

and in Quaternary fanglomerate where Lynn Creek 

leaves the siliceous assemblage on the east flank of 

the Tuscarora Mountains (Johnson, 1973, p. 26-27). 

Gold placers are not known from drainages below the 

Carlin deposit because micron-size gold particles from 

the Roberts Mountains and Popovich formations are 

too small to recover by panning. The Carlin deposit 

was recently (in geologic terms) uncovered by erosion 

prior to discovery (Evans, 1980, pl. 1, cross section cC'). Gold-bearing gravels from this upper plate source 

have subsequently been mixed with and (or) buried by 

alluvium derived from the carbonate assemblage. 

Therefore, unexploited gold placers of limited 

potential may underlie present alluvium in streams 

draining east and west from the Carlin deposit and 

from parts of the northwest-trending zone of hydrothermally altered rock. Placers could be present in 

the alluvium of southern Little Boulder Basin and along 

the east flank of the Tuscarora Mountains in the 

southeast corner of the Rodeo Creek NE quadrangle. 

This alluvium and the fanglomerate to the north are 

underlain by the middle Miocene to early Pliocene 

Carlin Formation, some of which could also contain 

gold placers. Minor gold placers in southwest Rodeo 

Creek NE quadrangle may be present downstream from 

gold-bearing quartz veins in the Hanson Creek 

Formation. Gold in any of these Tertiary and Quaternary units, especially if it originated from the 

carbonate assemblage, may be present in small 

amounts in very fine sediment fractions and may not 

constitute economic deposits by present-day standards. 

Some of the geologic, aeromagnetic, and geo-
chemical features associated with the Carlin deposit 

may be unique; other features may be useful as guides 

for exploration for disseminated gold deposits, at least 

in Nevada. Among characteristics that may be useful 

as exploration guides is the well-known lithologic 

association of principal gold deposits in the Roberts 

Mountains and Popovich formations, particularly the 

silty laminated dolomitic limestone common to both 

formations. Gold is also deposited in chert and shale 

of the siliceous assemblage, but these deposits do not 

comprise the major ore body in the study area. Large 

reserves of gold have been found in the Coast Ranges 

of California in a geologic setting very different from 

north-central Nevada (Vredenburgh, 1982). The 

deposits are associated with altered serpentinite and 

assemblages that include a wide variety of marine 

sedimentary rocks, mafic volcanic rocks, and 

metamorphic rocks (zeolite and blueschist facies). 

These deposits are associated with relatively high 

concentrations of mercury and antimony. These 

occurrences suggest that lithology may not be as 

important as other kinds of ore controls on a regional 

basis. 

Steep, generally north-trending faults are 

associated with the Carlin, Big Six, Blue Star, and 

Bootstrap deposits, although a regional northwesttrending structure may have been important in 

localizing alteration and gold deposition. Gold was 

deposited in the brecciated rock, and the faults served 

as conduits of mineralizing fluids. These relations 

indicate that another guide to exloration would be 

broad, preferably intersecting fracture zones, the 

trends of which may be important if they are related 

to Proterozoic or Paleozoic structures that are 

inferred to control the orientations of mineral belts. 

Gold occurrences in the study area indicate that many 

lithologies may be favorable ore hosts provided they 

are brecciated or hydrothermally altered enough to be 

permeable to ore fluids. 

Because the deposits in the Lynn window and 

vicinity seem related to Mesozoic and Tertiary intrusions, Paleozoic rocks in the vicinity of other such 

intrusions should be examined for metalliferous 

deposits. These intrusions may be concealed below 

sedimentary rocks where their presence may be 

indicated by broad contact-metamorphic aureoles 

surrounding minor intrusive bodies and aeromagnetic 

highs, especially over terrane exhibiting contact 

metamorphism and intrusion. Ore deposits may be 

closely associated with intrusions, as at the Gold 

Strike mine. Alternatively, deposits may be several 

kilometers from visible parts of intrusions. At the 

Carlin mine in the Lynn window, the major gold 

deposit is about 5 km from the outcrops of the quartz 

monzonite, 8 km from the Cretaceous granodiorite at 

the Gold Strike mine, and even farther from the main 

Tertiary granodiorite and quartz latite intrusions; one 

or more of these intrusions may have been associated 

with the gold mineralization at Carlin. 

Absence of contact-metamorphic aureoles or 

aeromagnetic highs does not rule out the presence of 

concealed intrusions. Aureoles could be concealed 

beneath unmetamorphosed or hydrothermally altered 

rocks. Aeromagnetic highs over concealed intrusions 

may be absent if the ferromagnetic minerals are 

oxidized, were absent initially, or are overprinted by 

ferromagnetic surficial lavas. The highs also may be 

absent if the intrusions are deep below surficial rocks 

poor in ferromagnetic minerals. In this case, ore 

deposits may also be inaccessible to surficial exploration techniques. The aeromagnetic trough in the study 

area does not appear to be significant regionally, 

because the gold deposits at the Bootstrap and Carlin 

windows (U.S. Geological Survey, 1967), at Gold Acres 

(Wrucke and others, 1968, fig. 7), and at Cortez 

(Gilluly and Masursky, 1965, pl. 3) occur on aeromagnetic gradients. 

The Carlin deposit is within a broad zone of 

hydrothermally altered rock that may be part of an 

extensive mineral belt at least 70 km long. The origin 

of this zone is complex; in the study area it may be the 

product of as many as three periods of hydrothermal 

activity. Other broad alteration zones of this kind 

may have potential gold deposits, regardless of 

orientation. 

Because gold is statistically associated with 

mercury in the Roberts Mountains Formation, the 

principal ore host at the Carlin deposit, mercury 

analyses of soil gas may be a particularly valuable 

exploration tool in disseminated gold deposits 

(McCarthy and others, 1969). Brooks and Berger (1978) 

however, have found that detected mercury anomalies 

may not be directly related to gold mineralization at 

depth. 

CONCLUSIONS 

(1) The Carlin gold deposit is present in a northwest-trending zone of hydrothermally altered rocks 30 

km long by 3 km wide that may be part of a 

70-km long belt of mineralization. 

(2) Geologic evidence suggests that the zone of 

hydrothermally altered rocks, including the Carlin 

deposit, developed as a consequence of Mesozoic and 

Tertiary intrusions. 

(3) Partial geographical segregation of the 

following element suites may be due to one or more 

controls, including element zoning in a geothermal 

system: (a) Au, As, Hg, Sb, Cu, and Pb in the Rodeo 

Creek NE quadrangle around the Carlin mine; and (b) 

Ag, Ba, Mn, Mo, Sn, W, and Zn in both quadrangles. 

(4) Mass-balance calculations suggest that the 

gold in the Carlin deposit could have been 

concentrated during one geothermal cycle by hydrothermal fluids scavenging gold at concentrations 

similar to crustal abundance from carbonate sedimentary rocks in the lower plate of the Roberts 

Mountains thrust. However, a magmatic source for 

part of the gold cannot be ruled out. 

(5) Gold-placer deposits of limited potential may 

be present in Tertiary and Quaternary sedimentary 

units east and west of the Carlin and Big Six deposits 

and downstream from gold-bearing quartz veins in the 

Hanson Creek Formation. 

(6) Guides for exploration for Carlin-type disseminated gold deposits include (a) a litho logy, such as the 

silty dolomitic limestone in the Roberts Mountains and 

Popovich Formations, which is permeable to hydro25 
thermal fluids, or any lithology which has had its 

permeability enhanced by hydrothermal action and (or) 

brecciation; (b) broad intersecting fault zones, 

especially ones which may be regional structures of 

great age; (c) Mesozoic and (or) Tertiary intrusions in 

Paleozoic rocks; (d) broad zones of hydrothermally 

altered rocks, especially ones coincident with (b); and 

(e) mercury anomalies in soil gas. 

REFERENCES CITED 

Adams, J. W., 1973, Scandium, in Brobst, D. A., and 

Pratt, W. P., eds., United States mineral 

resources: U.S. Geological Survey Professional 

Paper 820, p. 567-571. 

Akright, R. L., Radtke, A. S., and Grimes, D. J., 1969, 

Minor elements as guides to gold in the Roberts 

Mountains Formation, Carlin gold mine, Eureka 

County, Nevada: Quarterly of the Colorado 

School of Mines, v. 64, no. 1, p. 49-66. 

Anderson, Phillip, 1980, Regional time-space 

distribution of porphyry deposits-a decisive test 

for the origin of metals in magma-related ore 

deposits; in Ridge, J. D., ed., Papers on mineral 

deposits exclusive of western North America: The 

International Association on the Genesis of Ore 

Deposits quadrennial symposium, 5th, Snowbird, 

Alta, Utah, 1978, Proceedings, v. 1, p. 35-48. 

Bailey, E. H., Clark, A. L., and Smith, R. M., 1973, 

Mercury, in Brobst, D.A., and Pratt, W. P., eds., 

United States mineral resources: U.S. Geological 

Survey Professional Paper 820, p. 401-414. 

Berger, B. R., and Taylor, B. E., 1980, Pre-Cenozoic 

normal faulting in the Osgood Mountains, 

Humboldt County, Nevada: Geology, v. 8, p. 594-

598. 

Brobst, D. A., 1973, Barite, in Brobst, D. A., and Pratt, 

W. P., eds., United States mineral resources: U.S. 

Geological Survey Professional Paper 820, p. 75-

84. 

Brook, C. A., Mariner, R. H., Mabey, D. R., Swanson, 

J. R., Guffanti, Marianne, and Muffler, L. J. P., 

1979, Hydrothermal convection systems with 

reservoir temperatures 90° C: in Muffler, L. P. 

J., ed., Assessment of geothermal;esources of the 

United States-1978, U. S. Geological Survey 

Circular 790, p. 18-85. 

Brooks, R. A. and Berger, B. R., 1978, Relationship of 

soil-mercury values to soil type and disseminated 

gold mineralization, Getchell Mine area, 

Humboldt County, Nevada, in Lovering, T. G. and 

others, eds., Conceptual models in exploration 

geochemistry; the Basin and Range Province of 

the western Unitd States and northern Mexico, 

Journal of Geochemical Exploration, v. 9, no. 2-3, 

p. 186-194. 

Butterman, W. C., 1980a, Gold, in Metals and minerals, 

v. 1 of Minerals yearbook l977: U.S. Bureau of 

Mines,p.427-445. 

1980b, Gold, in Metals and minerals, v. 1 of Miner-

--als Yearbookl978-79: U. S. Bureau of Mines, v. 1, 

p. 377-399. 

Cathles, L. M., 1981, Fluid flow ~d genesis of hydrothermal ore deposits: Economic Geology, 75th 

Anniversary Volume, p. 424-457. 

26 

Coats, R. R., and Riva, J. F., 1983, Overlapping 

overthrust belts of late Paleozoic and Mesozoic 

ages, northern Elko County, Nevada: Geological 

Society of America Memoir 157, p. 305-327. 

Cox, D. P., Schmidt, R. G., Vine, J. D., Kirkemo, 

Harold, Tourtelot, E. B., and Fleischer, Michael, 

1973, Copper, in Brobst, D. A., and Pratt, W. P., 

eds., United States mineral resources: U.S. 

Geological Survey Professional Paper 820, p. 163-

190. 

Daly, R. A., Manger, G. E., and Clark, S. P., Jr., 1966, 

Density of rocks, in Clark, S. P., Jr., ed., 

Handbook of physical constants: Geological 

Society of America Memoir 97, p. 19-26. 

Dickson, F. W., Rye, R. 0., and Radtke, A. S., 1978, 

The Carlin gold deposit: product of an ancient 

geothermal system that extracted ore and gangue 

components from sedimentary rocks abs. : International Association on the Genesis of Ore 

Deposits Symposium, 5th, Snowbird, Alta, Utah, 

1978, Program and Abstracts, p. 82. 

1979, The Carlin gold depositas a product of rock-

--water interactions: in Ridge, J. D., ed., Papers on 

mineral deposits of western North America, 

International Association on the Genesis of Ore 

Deposits Quadrennial symposium, Snowbird, Alta, 

Utah, 1978, Proceedings, v. IT: Nevada Bureau of 

Mines and Geology Report 33, p. 101-108. 

Dorr, J. V. N., IT, Crittenden, M. D., Jr., and Worl, R. 

G., 1973, Manganese, in Brobst, D. A., and Pratt, 

W. P., eds., United States mineral resources: U.S. 

Geological Survey Professional Paper 820, p. 385-

399. 

Emmons, W. H., 1910, A reconnaissance of some 

mining camps in Elko, Lander, and Eureka 

Counties, Nevada: U.S. Geological Survey 

Bulletin 408, 130 p. 

Evans, J. G., 1974a, Geologic map of the Rodeo Creek 

NE quadrangle, Eureka County, Nevada: U.S. 

Geological Survey Geologic Quadrangle Map GQ1116, scale 1:24,000. 

1974b, Geologic map of the Welches Canyon quad-

--rangle, Eureka County, Nevada: U.S. Geological 

Survey Geologic Quadrangle Map GQ-1117, scale 

1:24,000. 

__ 1980, Geology of the Rodeo Creek NE and Welches 

Canyon quadrangles, Eureka County, Nevada: 

U.S. Geological Survey Bulletin 1473, 81 p. 

Evans, J. G., and Cress, L. D., 1972, Preliminary 

geologic map of the Schroeder Mountain 

quadrangle: U.S. Geological Survey Miscellaneous 

Field Studies Map MF-324, scale 1:24,000. 

Evans, J. G., and Mullens, T. E., 1976, Bootstrap 

Window, Elko and Eureka Counties, Nevada: U.S. 

Geological Survey Journal of Research, v. 4, no. 1, 

p. 119-125. 

Evans, J. G., and Peterson, J. A., 1980, Chemical 

analyses of 877 rocks from the Rodeo Creek NE 

and Welches Canyon quadrangles, Eureka County, 

Nevada: U.S. Geological Survey Open-File Report 

80-605. 

Evans, J. G., and Theodore, T. G., 1978, Deformation 

of the Roberts Mountains Allochthon in northcentral Nevada: U.S. Geological Survey 

Professional Paper 1060, 18 p. 

Gilluly, James, and Masursky, Harold, 1965, Geology of 
the Cortez quadrangle, Nevada: U.S. Geological 

Survey Bulletin 117 5, 117 p. 

Grimes, D. J., and Marranzino, A. P., 1968, Directcurrent arc and alternating-current spark emission 

spectrographic field methods for semiquantitative analyses of geologic materials: U.S. 

Geological Survey Circular 591, 6 p. 

Gualtieri, J. L., 1973, Arsenic, in Brobst, D. A., and 

Pratt, W. P., eds., United States mineral 

resources: U.S. Geological Survey Professional 

Paper 82.0, p. 51-61. 

Hardie, B. S., 1966, Carlin gold mine, Lynn district, 

Nevada: Nevada Bureau of Mines Report 13, p. 

73-83. 

Hausen, D. M., 1967, Fine gold occurrence at Carlin, 

Nevada: New York, Columbia University, Ph. D. 

thesis, 166 p. 

Hausen, D. M., and Kerr, P. F., 1968, Fine gold 

occurrence at Carlin, Nevada, in Ridge, J. D., ed., 

Ore deposits of the United States, 1933-1967 

(Graton-Sales Volume) Vol. I: New York, American 

Institute of Mining, Metallurgical, and Petroleum 

Engineers, p. 908-940. 

Heiland, C. A., 1940, Geophysical exploration: New 

York, Prentice-Hall, 1013 p. 

Henley, R. W., and Ellis, A. J., 1983, Geothermal 

systems ancient and modern: a geochemical 

review: Earth Science Reviews, v. 19, p. 1-50. 

Hobbs, S. W ., and Elliott, J. E., 1973, Tungsten, in 

Brobst, D. A., and Pratt, W. P., eds., United 

States mineral resources: U.S. Geological 

Survey Professional Paper 820, p. 667-678. 

Hoyt, C. D., 1971, Gold, in Metals and Minerals, v. 1 of 

Mineral Yearbook 1969: v. 1, U.S. Bureau of 

Mines, p. 521-538. 

1972, Gold, in Metals and Minerals, v. 1 of Mineral 

--yearbook 1970: U.S. Bureau of Mines, p:-535-552. 

Johnson, M. G., 1973, Placer gold deposits of Nevada: 

U.S. Geological Survey Bulletin 1356, 118 p. 

Jones, R. S., 1968, Gold in meteorites and in the 

Earth's crust: U. S. Geological Survey Circular 

603,4 p. 

1969, Gold in igneous, sedimentary and metamor-

--phic rocks: U.S. Geological Survey Circular 610, 

28 p. 

1970, Gold content of water, plants, and animals: 

--U.S. Geological Survey Circular 625, 15 p. 

Ketner, K. B., and Smith, J. F., Jr., 1982, Mid-Paleozoic age of the Roberts thrust unsettled by new 

data from northern Nevada: Geology, v. 20, p. 

298-303. 

King, R. U., Shawe, D. R., and MacKevett, E. M., Jr., 

1973, Molybdenum, in Brobst, D. A., and Pratt, W. 

P., eds., United States mineral resources: U.S. 

Geological Survey Professional Paper 820, p. 425-

435. 

Lee, Tan, and Yao, Chi-Lung, 1970, Abundance of 

chemical elements in the earth's crust and its 

major tectonic units: International Geology 

Review, v. 12, no. 7, p. 778-786. 

Lepeltier, Claude, 1969, A simplified treatment of 

geochemical data by graphical representation: 

Economic Geology, v. 64, p. 538-550. 

Lovering, T. G., 1963, Use of nonparametric statistical 

tests in the interpretation of geological data: 

Transactions of the Society of Mining Engineers, 

v. 226, no. 2, p. 137-140. 

Lucas, J. M., 1981, Gold, in Metals and Minerals, v. 1 

of Minerals Yearbook 1980: U.S. Bureau of Mines, 

p.- 34 7-373. 

1982, Gold, in Metals and Minerals, v. 1 of Minerals 

--Yearbook 1981; U.S. Bureau of Mines, p:-365-391. 

1983, Gold, in Metals and Minerals, v. 1 of Minerals 

--Yearbook, 1982: U.S. Bureau of Mines, p. 369-397. 

1984, Gold, in Metals and Minerals, v. 1 of Mineral 

--Yearbook, 1983: U.S. Bureau of Mines, p. 385-411. 

McCarthy, J. H., Jr., Vaughn, W. W., Learned, R. E., 

and Meuschke, J. L., 1969, Mercury in soil gas and 

air-a potential tool in mineral exploration: U.S .. 

Geological Survey Circular 609, 16 p. 

McKee, E. H., Silberman, M. L., Marvin, R. E., and 

Obradovich, J. D., 1971, A summary of 

radiometric ages of Tertiary volcanic rocks in 

Nevada and eastern California. Part L Central 

Nevada: Isochron/West, no. 2, p. 21-42. 

Miller, M. H., 1973, Antimony, in Brobst, D. A., and 

Pratt, W. P., eds., United States mineral 

resources: U.S. Geological Survey Professional 

Paper 820, p. 45-50. 

Morris, H. T., Heyl, A. V., and Hall, R. B., 1973, Lead, 

in Brobst, D. A., and Pratt, W. P ., eds., United 

States mineral resources: U.S. Geological Survey 

Professional Paper 820, p. 313-332. 

Morrow, A. B., and Bettles, Keith, 1982, Geology of 

the Gold Strike mine, Elko County, Nevada: 

Western States Minerals Corporation, Wheat 

Ridge, Colorado. 

Mullens, T. E., 1980, Stratigraphy, petrology, and some 

fossil data of the Roberts Mountains Formation, 

north-central Nevada: U.S. Geological Survey 

Professional Paper 1063, 67 p. 

Olade, M., Fletcher, K., and Warrren, H. V., 1975, 

Barium-strontium relationships: Western Miner, 

March, p. 24-28. 

Radtke, A. S., 1973, Preliminary geologic map of the 

Carlin gold mine, Eureka County, Nevada: U.S. 

Geological Survey Miscellaneous Field Studies 

Map MF-537, scale 1:3,636. 

1974, Preliminary geologic map of the area of the 

--Carlin and Blue Star gold deposits, Eureka, 

County, Nevada: U.S. Geological Survey 

Miscellaneous Field Studies Map MF-552, scale 

1:12,000. 

__ 1981, Geology of the Carlin gold deposit, Nevada: 

U.S. Geological Survey Open-File Report 81-97, 

154 p. 

Radtke, A. S., Heropoulos, C., Fabbi, B. R., Scheiner, 

B. J ., and Essington, Mel, 1972, Data on major and 

minor elements in hosts rocks and ores, Carlin 

deposit, Nevada: Economic Geology, v. 67, p. 975-

978. 

Radtke, A. S., Rye, R. 0., and Dickson, F. W., 1980, 

Geology and stable isotope studies of the Car lin 

gold deposit, Nevada: Economic Geology, v. 75, p. 

641-672. 

Radtke, A. S., and Scheiner, B. J., 1970, Studies of 

hydrothermal gold deposition (I)-Carlin gold 

deposit, Nevada-the role of carbonaceous 

materials in gold deposition: Economic Geology, 

v. 65, p. 87-102. 

Regnier, Jerome, 1960, Cenozoic geology in the 

vicinity of Car lin, Nevada: Geological Society of 

27 
America Bulletin, v. 71, p. 1189-1210. 

Renner, J. L., White, D. E. and Williams, D. L., 1975, 

Hydrothermal convection systems, in White, D. E. 

and Williams, D. L., eds., Assessment of 

geothermal resources of the United States1975: U.S. Geological Survey Circular 726, 155 p. 

Roberts, R. J., 1960, Alinement of mining districts in 

north-central Nevada: U.S. Geological Survey 

Professional Paper 400-B, p. B17-B19. 

Roberts, R. J ., Montgomery, K. M., and Lehner, R. E., 

1967, Geology and mineral resources of Eureka 

County, Nevada: Nevada Bureau of Mines Bulletin 

64, 152 p. 

Roberts, R. J., Radtke, A. S., Coats, R. R., Silberman, 

M. L., and McKee, E. H., 1971, Gold-bearing 

deposits in north-central Nevada and southwestern 

Idaho: Economic Geology, v. 66, p. 14-33. 

Ryan, J. P.,1966, Gold, in Metals and Minerals, v. 1 of 

Mineral yearbook 1965: U.S. Bureau of Mines, P: 

433-454. 

1968, Gold, in Metals and Minerals, v. 1 of Miner-

--als yearbookl967: U.S. Bureau of Mine5;""v. 1, p. 

523-544. 

1969, Gold, in Metals and Minerals, v. 1 of Miner-

--als yearbookl968: u·.s. Bureau of Mine~ p. 529-

549. 

Rye, 'R. 0., Doe, B. R., and Wells, J. D., 1974, Stable 

isotope and lead isotope study of the Cortez, 

Nevada, gold deposit and surrounding area: U.S. 

Geological Survey Journal of Research, v. 2, p. 

13-23. 

Sainsbury, C. L., and Reed, B. L., 1973, Tin, in Brobst, 

D. A., and Pratt, W. P., eds., United States 

mineral resources: U.S. Geological Survey 

Professional Paper 820, p. 637-651. 

Seward, T. M., 1973, Thio complexes of gold and the 

transport of gold in hydrothermal ore solutions: 

Geochimica et Cosmochimica Acta, v. 37, no. 3, 

P• 379-399. 

Siegel, Sidney, 1956, Nonparametric statistics for the 

behavioral sciences: New York, McGraw-Hill, 

312 P· 

Silberman, M. L., White, D. E., Keith, T. E. and 

Dockter, R. D., 1979, Duration of hydrothermal 

activity at Steamboat Springs, Nevada, from ages 

of spatially associated volcanic rocks: U.S. 

Geological Survey Professional Paper 458-D, 14 p. 

Sims, J. D., and White, D. E., 1981, Mercury in the 

sediments of Clear Lake, in Research in The 

Geysers--Clear Lake geothe~al area, northern 

California: U.S. Geological Survey Professional 

Paper 1141 , p. 2 3 7 -241. 

Skillings, D. N., Jr., 1984, Carlin Gold Mining Co.'s 

operations and Gold Quarry project: Skillings 

Mining Review, v. 73, no. 47, Nov. 24, p. 4-8. 

Thompson, C. E., Hakagawa, H. M., and Van Sickle, G. 

H., 1968, Rapid analyses for gold in geologic 

materials, in Geological Survey research 1968: 

U.S. Geological Survey Professional Paper 600-B, 

p. B130-B132. 

Thompson, G. A., and White, D. E., 1964, Regional 

geology of the Steamboat Springs area, Washoe 

County, Nevada: U.S. Geological Survey 

Professional Paper 458-A, 52 p. 

U.S. Geological Survey, 1967, Aeromagnetic map of 

28 

the Palisades 1 and Palisades 2 quadrangles, 

Eureka and Elko Counties, Nevada: U.S. 

Geological Survey Open-file report 67-246 , scale 

1:62,500. 

Vaughn, W. W~, and McCarthy, J. H., Jr., 1964, An 

instrumental technique for the determination of 

submicrogram concentrations of mercury in soils, 

rocks, and gas, in Geological Survey research 

1964: U.S. Geological Survey Professional Paper 

501-D, p. D123-D127. 

Vinogradov, A. P., 1962, Average contents of chemical 

elements in the principal types of igneous rocks of 

the Earth's crust: Geochemistry, no. 7, p. 641-

664. 

Vredenburgh, L. M., 198 2, Tertiary gold bearing 

mercury deposits of the Coast Ranges of 

California: California Geology, v. 35, no. 2, p. 23-

27. 

Wedow, Helmuth, Jr., Kiilsgaard, T. H., Heyl, A. V., 

and Hall, R. B., 1973, Zinc, in Brobst, D. A., and 

Pratt, W. P., eds., United States mineral 

resources: U.S. Geological Survey Professional 

Paper 820, p. 697-711. 

Weissberg, B. G., 1969, Gold-silver ore-grade 

precipitates from New Zealand thermal waters: 

Economic Geology, v. 64, p. 95-108. 

Wells, J. D., Elliott, J. E., and Obradovich, J.D., 1971, 

Age of the igneous rocks associated with ore 

deposits, Cortez-Buckhorn area, Nevada, in 

Geological Survey research 1971: U.S. Geological 

Survey Professional Paper 750-C, p. C127-C135. 

Wells, J. D., Stoiser, L. R., and Elliott, J. E., 1969, 

Geology and geochemistry of the Cortez gold 

deposit, Nevada: Economic Geology, v. 64, p. 

526-537. 

West, J. M., 1973, Gold, in Metals and Minerals, v. 1 of 

Minerals yearbook 1971: U.S. Bureau of Mines, V. 

1, p. 539-560. 

1974, Gold, in Metals and Minerals, v. 1 of Minerals 

--yearbook 1972: U.S. Bureau of Mines, p-:-567-588. 

1975, Gold, in Metals and Minerals, v. 1 of Minerals 

--yearbook 1973: U.S. Bureau of Mines, p-:-557-581. 

1976, Gold, in Metals and Minerals, v. 1 of Minerals 

--yearbook 1974: U.S. Bureau of Mines, v. 1, p. 603-

626. 

1977, Gold, in Metals and Minerals, v. 1 of Minerals 

--yearbook 1975: U.S. Bureau of Mines, v-:-1, p. 669-

696. 

West, J. M., and Butterman, W. C., 1979, Gold, in 

Metals and Minerals, v. 1 of Minerals yearbook 

1976: U.S. Bureau of Mines,V.1, p. 591-615. 

White, D. E., 1967, Mercury and base-metal deposits 

with associated thermal and mineral waters, in 

Barnes, H. L , ed., Geochemistry of hydrothermal 

ore deposits: New York, Holt, Rinehart and 

Winston, p. 575-631. 

1968, Hydrology, activity, and heat flow of the 

---Steamboat Springs thermal system, Washoe 

County, Nevada: U.S. Geological Survey 

Professional Paper 458-C, 109 p. 

1981, Active geothermal systems and hydrothermal 

--ore deposits: Economic Geology, 75th 

Anniversary Volume, p. 392-423. 

White, D. E. and Roberson, C. E., 1962, Sulphur Bank, 

California, a major hot-spring quicksilver deposit: 
Geological Society of America Bulletin, 

Buddington Volume, p. 397-428. 

Wrucke, C. T., and Armbrustmacher, T. J., 1975, 

Geochemical and geologic relations of gold and 

other elements at the Gold Acres open-pit mine, 

Lander County, Nevada: U.S. Geological Survey 

Professional Paper 860, 27 p. 

Wrucke, C. T., Armbrustmacher, T. J., and Hessin, T. 

D., 1968, Distribution of gold, silver, and other 

metals near Gold Acres and Tenabo, Lander 

County, Nevada: U.S. Geological Survey Circular 

589, 19 p. 

29 
11!)'l15' 

Qal 

-----··------~-----~-·--~~--·---·-_j Gr:m.OGY BY ,J. f.VANS 1968-71 

3 KILOMETERS 

Pipe 6. Locations of samples with gold concentrations greater than or equal to 0.05 ppm. See figure Z for 

explanation of geologic symbols. 

30 
I 

> 

w 

.... 

.... 

ct 

> 

a: 

w 

0 

Qal 

soc 

~ ~ ) SOc 

(j""--

:L 

SOh DSrm 

EXPLANATION 

Gold content, in parts per million 

+ ~ 0.05 to < 0.25 

6. ~ 0.25 to < 0.50 

D ~ 0.50 to < 1.00 * ~ 1.00, value shown 

~ ~L-----------\~------T-K-.rd------~ 

4il'4S LOc ~---· -

Figul'e 6. Continued. 

3KtlOMHERS 

-11fiG15' 

WELCHES CANYON 

QUADRANGLE 

Qal 

GEOLOGY BY J. G. EVANS 1%8-71 

31 
SOc GEOLOGY BY J. G. EVANS l%8·71 

3KILOMETERS 

l'taua'e 7. Locations of samples with arsenic concentrations greater than or equal to 200 ppm. See figure 2 for 

explanation of geologic symbols. 

32 
l'" 

> 

w 

..J 

-' 

ct 

> 

iX 

w 

0 

;:) 

0 

Q) 

SO• 

c ~ 

C1a1 

( 

I x J 

) 

I 

\.,, •. i, 

I 

Figure 7. Continued. 

.// ~ 

.. / ....... }: 

3 KILOMETERS 

116"15' 

Oal 

D! 

GEOLOGY BY J. G. EVANS 1968-71 

33 
116"1S' 

3 KILOMETERS 

Fi~Ue 8. Locations of samples with mercury concentrations greater than or equal to 1 ppm. See figure 2. for 

explanation of geologic symbols. 

34 
f? 

,U 

/( 

> 

ct 

> 

a:: 

w 

0 

Gal 

~,D! 

\..\ c 

EXPLANATION 

Mercury concentration, in parts per million 

+0!!1to<5 . I ~ / D 2: 5 to < 10 

c._/ _; * 0!!:: 10, actual value not known ~ when > 10 ppm 

~~·~~------------~--------------~ 4,1·4·· ~~ ~~- --- - ----- ___ .,L\____________________ \ __ 

Figure 8. Continued. 

T( 

Qol~ \ ! 

(~~ 

D! 

SOc 

UEOLOGY BY J. G. FVAN~ !961'1-71 

3 KILOMETERS 

35 
HODEO CHE[.K NE QUADRANGLE 

Qf 

Ot 

) 

3 KILOMETERS 

P'ipan 9. Locations of samples with antimony concentrations greater than or equal to 70 ppm. See figure 2. for 

explanation of geologic symbols. 

36 
Trt 

I 

\ 

i 

c.J.-J 

>-

w 

-J 

-J 

<t 

> 

a:: 

w 

0 

()d: 

-> 

SOt 

S(ir 

EXPLANATION 

Antimony concentration, in parts per million 

+ ~ 70 to < 500 

b.~ 500 to < 1,000 

D ~ 1,000 to < 5,000 

SC)c 

* ~ 5,000, value shown; actual value not known 

when > 10,000 ppm 

Figure 9. Continued. 

; 16'15' 

--WELCHES CANYON] 

QUADRANGLE !,: 

Oal 

/ "'""" .....---------\.._ '~ ' ------- 2 z __.---/..-111 ~ 

;?/ 

?- I 

I 

Tc 

D! 

g- so 

i" 

,-,~ 1\~' I \;' ' ''j 

TKrd ' TKrd / l Kr~) - --- L -- - - __ _._- - ~-------

SOc 

GEOLOGY BY J. G. [\i;\NS 1968-71 

3 KILOMETERS 

37 
RODEO CREEK NE Q~ADRANGLE ~ so, 

Qf 

DSrrn GEOLOf>Y BY J. G. EVANS 1968-71 

3 KilOMETERS 

Fipe 10. Locations of samples with copper concentrations greater than or equal to ZOO ppm. See figure Z for 

explanation of geologic sym bois. 

38 
> 

w 

...l 

....1 

<t 

> 

a: 

w 

0 

Qal 

EXPlANATION 

Copper concentration, in parts per mdlion 

+ ~ 200 to < 1,000 

b.~ 1,000 to < 5,000 

0 ~ 5,000 to < 10,000 * ~ 10,000, actual value not known 

when > 10,000 ppm 

""rot \~ . ...J. ______ __L ___________ ~ 

Figure 10. Continued. 

9- SOc j1 Oi 

~~_~_-;:~?_ 

WELCHES CANYON I 

QUADRANGLE i 

0~~ 

~I 

Tc 

I 

I 

I 

I 

I 

Oo~ \ I 

SOc 

bi I 

Dl 

I 

I 

I 

i 

GEOLOGY BY J. G. EVANS 1968-71 

3 KILOMETERS 

39 
*7/.000 

>2o,ood * ., . . ~/~· >20,0bO / 

+ 

+ 

+: 

HODFO CKLLK Nr: 

+ 

/ 

3 KilOMETERS 

P'ta&ue 11. Locations of samples with lead concentrations greater than or equal to 100 ppm. See figure 2. for 

explanation of geologic symbols 

40 
> 

w 

-J 

-J 

<t 

> 

DSrrn 

:~'h. 

r 

I 

EXPLANATION 

Lead concentration, in parts per million 

+ 2:: 100 to < 300 

6. 2:: 300 to < 1,000 

0 2:: 1,000 to < 7,000 * 2:: 7 ,000, value shown; actual value not known 

when > 20,000 ppm 

Figure 11. Continued. 

~ 16'15' 

Tc 

SOc 

3 KILOMETERS 

41 
+ 

4 

~--· 

i 

.·, :'\ 

:.A 

_ .. tj' 

+ 

;; 

HODEO Cf\l-_[.K NE QUADHi\N(.iLE 

0 !::,. 

0 !::,. / 

D;/ 

;!~::,. 

J+!::,. + 

t++ + 

2. 

0 

+ 

+ 

+ 

+ 

+ 

\ ' ~ ) ·. 

3 KILOMETERS 

Fi&W'e lZ. Locations of samples with barium concentrations greater than or equal to 1,000 ppm. See figure 2 for 

explanation of geologic symbols 

42 
• (( Trt l 

> 

w 

..,j 

..,j 

Oai 

/ 

EXPLANATION 

Barium cbncentration, in parts per million 

+ 1,000 

6. 1,500 to 2,000 

0 3,000 to 5,000 * > 5,000, actual value not known 

Figure lZ. Continued. 

118'15' 

Dl 

3 KILOMETERS 

43 
D 

Qf 

soc 

Qal 

GEOLOGY BY J. G. EVANS 1968-71 

t3KILOMETERS 

Figlue 13. Locations of samples with manganese concentrations greater than or equal to 1,000 ppm. See figure Z 

for explanation of geologic symbols. 

44 
> 

w 

-J 

..J 

<( 

> 

a: 

w 

c 

-J 

:::> 

0 

IXl 

) 

/ 

SOc 

I 

~ ) 

c. 

EXPLANATION 

Manganese concentration. in parts per million 

+ 1.000 

b. 1.500 to 2.000 

0 3.000 to 5.000 * > 5.000. actual value not known 

Figure 13. Continue4. 

3KILOME1IRS 

WELCHES CANYON 

QUADRANGLE Oai 

01 

SOc 

G. EVAN!'> l96S-7J 

45 
+ 

+ 

+ 

+ 

+ 

+ 

3 KILOMETERS 

Figure 14. Locations of samples with molybdenum concentrations greater than or equal to 50 ppm. See figure 2. 

for explanation of geologic symbols. 

46 
>-

w 

-4 

....; 

ct 

> 

S(Jc 

r 

i 

EXPlANATION 

Molybdenum concentrations, in parts per million 

+~50 to < 100 

6. ~ 100 to < 500 \ * ~ 1,000, value shown 

lKrd 

Figure 14. Continued. 

c;EOLOGY BY J G £\'.1\:-.i~ l%S-7l 

3KILOMETEAS 

47 
3 KILOMETERS 

P'ipe 15. Locations of samples with silver concentrations greater than or equal to 0.5 ppm. See figure Z for 

explanation of geologic symbols. 

48 
\ 

\ 

1 

/,.....--, .. --/ ' ,,~.---! 

>-

w 

...I 

...I 

<t 

> 

0 

/ 

........ 

~ 

r-'0 

! { "-- ·~-~/ ! 

EXPLANATION 

Silver concentration, in parts per million 

+ 0!: 0.5 to < 1.0 

6. 0!: 1.0 to < 5.0 

0 ~ 5.0 to < 10.0 * 2:: 10.0, value shown 

rc 

\ 

~ Dl 

g- SOr j1 01 

/\ ___ ~ ~~~)! --~.., ' /~1 

Tl<.r~ ______ .,_ _ _!_Kr~( ____ /' ~~Kr~L __ _ 

GfOLOGY BY J. G. f'V:'\N~ !968-71 

0 3 KILOMETERS 

L----.----~------~--------~ 

FiguN 15. Continued. 

49 
!1o"lb' 

HODEO CHLEK NE QUADHANGLE 

Qf 

3 KILOMETERS 

Figun 16. Locations of samples with tin concentrations greater than or equal to 10 ppm. See figure 2 for 

explanation of geologic sym bois. 

50 
:. (! 

H .. · 

. 

/I ., 

ct 

> 

a: 

w 

0 

::.:;) 

0 

m 

Gal 

EXPLANATION 

Tin concentration, in parts per million 

+ 2: 10 to < 100 

b. 2: 100 to < 300 

0 2: 300 to < 1,000 * 2: 1 ,000; actual value not known 

when > 1,000 ppm 

Figure 16. COntinued. 

116°15' 

w-E-LC ___ H_E_S __ C_A_N_Y_O_N----.1 

QUADRANGLE . Qal • DOb 

Dl 

SOc 

-L.....--'----- -- --~----------

GEOLOGY BY J. G. EVANS 1968-71 

3 KILOMETERS 

51 
Of 

Ot 

GEOLOGY BY ,I G EVANS 1968-71 

3 KILOMETERS 

J'ipe 17. Locations of samples with tungsten concentrations greater than or equal to 50 ppm. See figure Z for 

explanation of geologic symbols. 

52 
> 

w 

...1 

...I 

<( SOc 

> 

3KILOMETEAS 

Figure 17. COntinued. 

53 
:o 

+ 

*::,!Jo.ooo 

'+ + 

0 

+ 

+ 

+ + 

0 

0 

+ 

0 

+ 

60 

*>10,000 .·• 

3 KILOMETERS 

+ 

Pipe 18. Locations of samples with zinc concentrations greater than or equal to 2.00 ppm. See figure 2. for 

explanation of geologic symbols. 

54 
>-

w 

...1 

...1 

ct 

> 

a:: 

w 

a 

Ga' 

c ~ 

Figure 18. Cbntinued. 

DOb 

3 KILOMETERS 

116°1&' 

WELCHES CANYON! 

Go~-~ 

Tc 

Ool~ 

~ 

I 

+ Dl 

SOc 

55 
~~ 

{2074x) _ __, 

High Low 

EXPLANATION 

Centers of aeromagnetic anomalies. Highest values 

(in gammas) at X 

---Au--- Area containing clusters of samples with anomalous 

concentrations of gold (Au) 

- --As --- Area containing clusters of samples with anomalous 

Au* concentrations of arsenic (As) 

- . - Hg- . - Area containing clusters of samples with anomalous 

concentrations of mercury (Hg) 

........... Sb........... Area containing clusters of samples with anomalous 

concentrations of antimony (Sb) 

- .. - Cu-· ·- Area containing clusters of samples with anomalous 

concentrations of copper (Cu) 

----- Pb ----- Area containing clusters of samples with anomalous 

concentrations of lead (Pb) * Locality with high concentrations (in parts per million) 

of one or more of the following elements: 

Au,~ 1 

As,~ 7,000 

Hg, ~ 10 

Sb, ~ 5,000 

Cu, ~ 10,000 

Pb, ~ 7,000 

3KILOMETERS 

;. 

Pipe 19. Map showing areas with anomalous concentrations of gold, arsenic, mercury, antimony, copper, and 

lead and centers of aeromagnetic anomalies. See figure 2. for explanation of geologic symbols. 

56 
> 

w 

_, 

_, 

<t i 

> / 

'~ 

a: 

w 

0 

_, 

:> 

0 

CXl 

3KILOMETIRS 

Figure 19. Continued. 

57 
(2074';) 

--High 

---Ag---

---Ba---

···········Mn··········· 

----- Mo-----

-x-Sn-x-

-·-w-· 

-··-ZnEXPLANATION 

Centers of aeromagnetic anomalies. Highest values 

(In gammas) at X 

Area containing clusters of samples with anomalous 

concentrations of silver (Ag) 

Area containing clusters of samples with anomalous 

concentrations of barium (Ba) 

Area containing cluaters of samples with anomalous 

concentrations of manganese (Mn) 

Area containing clusters of samples with anomalous 

concentrations of molybdenum (Mo) 

Area containing clusters of samples with anomalous 

concentrations of tin (Sn) 

Area containing clusters of samples with anomalous 

concentrations of tungsten (W) 

Area containing clusters of samples with anomalous 

concentrations of zinc (Zn) 

{,:l' 

* Locality with high concentrations (In parts per miUion) 

of one or more of the following elements: 

Ag, ~ 0.5 

Ba, ~ 1,000 

Mn.~ 1,000 

Mo.~ 50 

Sn, 2: 10 

W, 2:50 

Zn, 2: 200 

3KilOMETERS 

Figure ZO. Map showing areas with anomalous concentrations of silver, barium, manganese, molybdenum, tin, 

tungsten, and zinc and centers of aeromagnetic anomalies. See figure 2 for explanation of geologic symbols. 

58 
> 

a: 

w 

0 

..J 

;::) 

0 

Oal 

Figure 20. Cbntinued. 

£h 116"15' --·---.----------------, i WELCHES CANYON I 

Dob : QUADRANGLE I 

• Oal ' 

Tc 

Tc 

Dl 

JKILOMETERS 

59 
60 

Table 4. Distribution of gold in rock units 

Units with no samples containing ~0.05 ppm gold are omitted 

Number of samples 

with~ 0.05 ppm 

Percent of Number of samples 

Rock unit subpopulation with ~ 1 ppm 

Siliceous assemblage 

Chert ---------------------- 49 

Quartzite ------------------ 3 

Shale ---------------------- 6 

Quartz veins --------------- 7 

Eureka Quartzite --------------

Hanson Creek Formation 

Dolomite ------------------- 8 

Quartz veins --------------- 21 

Roberts Mountains Formation --- 20 

Jasperoid --------------------- 33 

Silurian and Devonian limestone 2 

Popovich Formation ------------

Cretaceous granodiorite -------

Quartz monzonite --------------

Quartz latite ----------------- 12 

Total----------------------- 176 

19 

14 

18 

32 

20 

75 

25 

31 

7 

22 

19 

14 

34 

10 

Table 5. Distribution of arsenic in rock units 

Units with no samples containing ~200 ppm arsenic are omitted 

Number of samples 

with ~ 200 ppm 

Siliceous assemblage 

Chert ---------------------- 67 Quartz --------------------- 6 Shale ---------------------- 7 Quartz veins --------------- 13 

Hamburg Dolomite -------------- 3 

Eureka Quartzite -------------- 1 Hanson Creek Formation 

Dolomite ------------------- 1 Quartz veins --------------- 19 

Roberts Mountains Format·ion --- 15 

Jasperoid --------------------- 36 

Popovich Formation ------------ 3 

Cretaceous granodiorite ------- 2 Quartz monzonite -------------- 2 Quartz latite ----------------- 15 

Total----------------------- 190 

Percent of 

subpopulation 

26 

27 

21 

59 

8 

6 

3 

68 

18 

33 

9 

10 

29 

43 

22 

9 

0 

0 

2 

0 

0 

8 

4 

7 

0 

2 

0 

0 

4 

36 (4 percent) 

Number of samples 

with ~ 1 ,000 ppm 

20 

1 

2 

4 

0 

0 

0 

11 

5 

10 

1 

1 

0 

7 

62 (7 percent) 

Maximum value 

(ppm) 

20.0 

.1 

.96 

7 .o 

.1 

.5 

18.0 

118.0 

32.0 

.1 

1.4 

.6 

.1 

8.0 

Maximum value 

(ppm) 

5,000 

1,000 

7,000 

3,000 

300 

300 

700 

>7 ,000 

3,000 

>7 ,000 

2,000 

2,000 

500 

>7 ,000 
Table 6. Distribution of mercury in rock units 

Rock unit Background 

Number of 

samples 

with ~ 1 ppm 

Percent of 

subpopula tion 

Siliceous assemblage: 

Chert----------------------- 0.10 46 18 

Quartzite------------------- .20 6 27 

Shale----------------------- .20 5 15 

Limestone------------------- .10 3 14 Quartz veins---------------- .45 6 27 

Hamburg dolomite--------------- .20 10 

Pogonip Group------------------ .1 1 6 

Eureka Quartzite--------------- .2 0 0 Hanson Creek Formation: 

Dolomite-------------------- .2 7 18 

Quartz veins---------------- 8.00 21 75 

Roberts Mountains Formation---- .45 26 33 

Jasperoid---------------------- 1.00 56 52 

Silurian and Devonian limestone .05 0 0 

Popovich Formation------------- .15 12 26 

Transitional assemblage-------- .10 0 0 

Cretaceous granodiorite------- .08 1 5 

Quartz monzonite-------------- .12 2 29 

Rhyodacite flows-------------- .08 0 0 

Andesite---------------------- .08 0 0 

Tertiary granodiorite--------- .08 0 0 

Quartz la ti te----------------- .20 11 31 

Intrusive breccia------------- .07 0 0 

Rhyolitic welded tuff--------- .07 0 0 

Total---------------------- 207 24 

Table 7. Distribution of antimony in rock units 

Units with no samples containing :: 70 ppm antimony are omitted 

63 

Number of 

samples 

with ~ 5 ppm 

12 

2 

0 

1 

2 

0 

0 

0 

3 

15 

4 

16 

0 

3 

0 

1 

1 

0 

0 

0 

3 

0 

0 

(7 percent) 

Maximum 

value 

(ppm) 

>10 

6.0 

3.0 

>10 

7.0 

3.5 

1.6 

.7 

>10 

>10 

>10 

>10 

.9 

>10 

.26 

>10.0 

>10 

.65 

.24 

.35 

>10 

.40 

.12 

Rock unit 

Number of samples 

with :: 70 ppm 

percent of 

subpopula tion 

Number of samples 

with ~ 1 , 000 ppm 

Maximum value 

(ppm) 

Siliceous assemblage 

Chert ---------------------- 20 8 0 300 

Quartzite ------------------ 1 5 0 200 

Shale ---------------------- 1 3 1 10,000 

Quartz veins --------------- 1 5 0 500 

Hamburg Dolomite -------------- 3 8 0 200 

Pogonip Group ----------------- 1 6 0 150 

Eureka Quartzite -------------- 3 17 0 300 

Hanson Creek Formation 

Dolomite ------------------- 9 23 2 1,500 

Quartz veins --------------- 26 93 15 >10 ,000 

Roberts Mountains Formation --- 25 32 1 1 ,ooo 

Jasperoid --------------------- 59 55 1 3,000 

Silurian and Devonian limestone 3 11 0 100 

Popovich Formation ------------ 4 7 1 2,000 

Cretaceous granodiorite ------- 1 5 0 500 

Andesite ---------------------- 1 8 0 100 

Quartz latite ----------------- 6 17 0 150 

Total---------------------- 164 19 21 (2 percent) 

61 
Table 8. Distribution of copper in rock units 

Number of Percent of Number Maximum 

Rock unit Background samples subpopula tion of samples value 

with ~ 200 ppm with ~ 1,000 ppm (ppm) 

Siliceous assemblage: 

Chert----------------------- 50 29 11 10 >10,000 

Quartzite------------------- 15 0 0 0 100 

Shale----------------------- 30 2 6 0 300 

Limestone------------------- 7 0 0 0 50 

Quartz veins---------------- 50 5 23 3 10,000 

Hamburg Dolomite--------------- 15 7 18 1 3,000 

Pogonip Group------------------ 5 0 0 0 150 

Eureka Quartzite--------------- 5 0 0 0 30 

Hanson Creek Formation: 

Dolomite-------------------- 5 1 3 0 500 

Quartz veins---------------- 700 17 61 13 7,000 

Roberts Mountains Formation---- 10 0 0 0 150 

Jasperoid---------------------- 10 4 4 1 > 10,000 

Silurian and Devonian limestone 15 1 4 0 200 

Popovich Formation------------- 5 0 0 0 150 

Transitional assemblage.-------- < 5 0 0 0 20 

Cretaceous granodiorite-------- 15 0 0 0 100 

Quartz monzonite--------------- 5 0 0 0 30 

Rhyodacite flows--------------- < 5 0 0 0 10 

Andes! te----------------------- 15 2 15 1 7,000 

Tertiary granodiorite---------- 10 0 0 0 30 

Quartz latite------------------ 100 8 23 3 10,000 

Intrusive breccia-------------- 30 0 0 0 50 

Rhyolitic welded tuff---------- < 5 0 0 0 5 

Total----------------------- 76 9 32 (4 percent) 

Table 9. Distribution of lead in rock units 

Number of Percent of Number of Maximum 

Rock unit Background samples subpopula tion samples value 

with > 100 ppm with ~ 1,000 ppm (ppm) 

Siliceous assemblage: 

Chert----------------------- 10 14 b 0 200 

Quartzite------------------- <10 1 5 0 100 

Shale----------------------- 10 0 0 0 50 

Limestone------------------- <10 0 0 0 70 

Quartz veins---------------- <10 2 9 0 100 

Hamburg Dolomite--------------- 20 5 13 1 1,000 

Pogonip Group------------------ <10 1 6 0 100 

Eureka Quartzite--------------- 10 1 6 0 100 Hanson Creek Formation: 

Dolomite-------------------- 20 5 13 2 7,000 

Quartz veins---------------- 3,000 21 75 HI >20,000 

Robaerts Mountains Formation--- 15 d 10 2 3,000 

Jasperoid---------------------- <10 4 4 1 2,000 

Silurian and Devonian limestone <10 0 0 0 

Popovich Formation------------- <10 2 4 2 7 ,ooo 

Transitional assemblage-------- 10 0 0 0 <10 

Cretaceous granodiorite-------- 10 0 0 0 20 

Quartz monzonite--------------- 20 0 0 0 30 

Rhyodacite flows--------------- 15 1 14 0 100 

Andesite----------------------- 10 0 0 0 50 

Tertiary granodiorite---------- 20 0 0 0 30 

Quartz latite------------------ 15 1 3 10 100 

Intrusive breccia-------------- 10 0 0 0 20 

Rhyolitic welded tuff---------- 30 0 0 0 70 

Total---------------------- 66 8 26 (3 percent) 

62 
Table 10. Distribution of barium in rock units 

Number of 

Rock unit Background samples Percent of subpopulation 

Number of 

samples 

Maximum 

value 

(ppm) with ~ 1 , 000 ppm (ppm) 

Siliceous assemblage: 

Ch&rt----------------------- ~0 56 22 

Quartzite------------------- 300 5 23 Shale----------------------- 500 7 21 

Limes tone------------------- 100 1 5 

Quartz veins---------------- 300 4 18 

Hamburg Dolomite--------------- 70 1 3 Pogonip Group------------------ 30 0 0 

Eureka Quartz! te-------------- 50 6 

Hanson Creek Formation: 

Dolomite-------------------- 30 3 8 

Quartz veins---------------- 20 2 7 

Roberts Mountains Formation---- 200 11 13 

Jasperoid---------------------- 20 27 25 Silurian and Devonian limestone 200 8 29 

Popovich Formation------------- 10 6 15 Transitional assemblage-------- 500 2 11 

Cretaceous granodiorite-------- 700 8 38 Quartz monzonite--------------- 700 3 43 

Rhyodacite flows--------------- 700 1 14 

Andes! te----------------------- 700 6 46 

Tertiary granodiorite---------- 1,500 7 78 Quartz lati te------------------ 700 14 40 

Intrusive breccia-------------- 1,000 7 70 Rhyolitic welded tuff---------- 200 0 0 

Total---------------------------- 180 21 

Table 11. Distribution of manganese in the rock units 

Rock unit 

Siliceous assemblage 

Chert ---------------------- Quartzite ------------------ Shale ---------------------- Limestone ------------------ Quartz veins --------------- Hamburg Dolomite --------------

Pogonip Group -----------------

Eureka Quartzite -------------- Hanson Creek Formation: 

Dolomite ------------------- Quartz veins --------------- Roberts Mountains Formation --- Jasperoid --------------------- Silurian and Devonian limestone 

Popovich Formation ------------ Transitional assemblage -------

Cretaceous granodiorite ------- Quartz monzonite -------------- Rhyodacite flows -------------- Andesite ---------------------- Tertiary granodiorite·---------

Quartz latite ----------------- Intrusive breccia ------------- Rhyolitic welded tuff ---------

Total ----------------------

Background 

(ppm) 

100 

100 

100 

700 

150 

2,000 

300 

150 

200 

200 

200 

70 

300 

150 

150 

700 

300 

700 

700 

1,000 

200 

500 

500 

Number of samples 

with ~ 1,000 ppm 

21 

2 

9 

8 

6 

22 

10 

0 

8 

2 

9 

3 

5 

2 

0 

7 

2 

2 

4 

6 

5 

4 

1 

l3a 

with ~ 5,000 ppm 

9 

1 

0 

0 

1 

0 

0 

0 

2 

8 

0 

1 

0 

0 

0 

0 

1 

1 

0 

2 

0 

28 (3 percent) 

Percent of 

subpopula tion 

2 

9 

26 

38 

27 

55 

56 

0 

20 

7 

11 

3 

18 

4 

0 

33 

29 

29. 

31 

67 

14 

40 

20 

16 

> 5,000 

> 5,000 

2,000 

1,000 

> 5,000 

2,000 

700 

3,000 

> 5,000 

> 5,000 

> 5,000 

> 5,000 

3,000 

> 5,000 

1,500 

1,500 

3,000 

1,000 

5,000 

5,000 

3,000 

> 5,000 

700 

Maximum value 

(ppm) 

5,000 

1,500 

2,000 

>5,000 

> 5,000 

>5,ooo 

>5,000 

700 

>5,000 

1,000 

5,000 

5,000 

3,000 

2,000 

300 

2,000 

1,000 

1,000 

1,500 

1,500 

3,000 

1,500 

5,000 

63 
64 

Table lZ. Distribution of molybdenum in the rock units 

Number of samples 

with .::so ppm 

Percent of Maximum value 

Rock unit subpopulation (ppm) 

Siliceous assemblage: 

Chert----------------------- 15 6 150 

Quartzite------------------- 1 5 50 

Shale----------------------- 2 6 70 

Limestone------------------- 0 0 10 

Quartz veins---------------- 2 9 70 

Hamburg Dolomite--------------- 4 10 1,000 

Pogonip Group------------------ 3 17 2,000 

Eureka Quartzite--------------- 0 0 7 Hanson Creek Formation: 

Dolomite-------------------- 3 200 

Quartz veins---------------- 4 200 

Roberts Mountains formation---- 1 1 50 

Jasperoid---------------------- 4 4 70 

Silurian and Devonian limestone 0 0 10 

Popovich Formation------------- 2 4 70 

Transitional assemblage-------- 0 0 10 

Cretaceous granodiorite-------- 0 0 10 

Quartz monzonite--------------- 0 0 < 5 

Rhyodacite flows--------------- 0 0 < 5 

Andesite----------------------- 0 0 < 5 

Tertiary granodiorite---------- 0 0 5 

Quartz la ti te------------------ 0 0 10 

Intrusive breccia-------------- 0 0 5 

Rhyolitic welded tuff---------- 0 0 10 

Total----------------------- 36 

Table 13. Distribution of silver in rock units 

Units with no samples containing ~ 0.5 ppm silver are omitted 

Rock unit 

Number of samples 

with ~0.5 ppm 

Siliceous assemblage 

Chert ---------------------- 88 

Quartzite ------------------ 14 

Shale ---------------------- 6 

Quartz veins --------------- 6 

Hamburg Dolomite -------------- 10 

Pogonip Group ----------------- 2 

Eureka Quartzite -------------- 1 

Hanson Creek Formation 

Dolomite ------------------- 11 

Quartz veins --------------- 23 

Roberts Mountains Formation --- 29 

Jasperoid --------------------- 23 

Silurian and Devonian limestone 1 

Popovich Formation ------------ 5 

Rhyodacite flows -------------- Tertiary granodiorite --------- Quartz latite ----------------- Intrusive breccia -------------

Total 225 

Percent of Number of samples 

subpopulation with ~ 5 ppm 

35 3 

18 0 

18 0 

27 0 

28 6 11 0 

6 0 

28 2 

82 17 

36 10 

21 4 

4 0 

13 0 

14 0 

11 0 

11 2 

10 0 

26 34 (4 percent) 

Maximum value 

(ppm) 

10 

1.5 

1.5 

2 

15 

1 

.5 

7 1,500 

3 

500 

.5 

3 

1 

.5 

5 

.5 
Table 14. Distribution of tin in rock units 

Units with no samples containing :: 10 ppm tin are omitted 

Rock unit 

Siliceous assemblage 

Number of samples 

with :! 10 ppm 

Limestone ------------------ 2 

Hamburg Dolomite -------------- 16 

Pogonip Group ----------------- 3. 

Hanson Creek Formation 

Dolomite ------------------- 7 

Quartz veins --------------- 15 

Roberts Mountains Formation ---

Jasperoid ---------------------

Total 45 

Percent of 

subpopulation 

10 

40 

17 

18 

53 

5 

Table 15. Distribution of tungsten in rock units 

Units with no samples containing ~ 50 ppm tungsten are omitted 

Number of samples Percent of 

Maximum value 

(ppm) 

50 

200 

200 

100 

> 1,000 

10 

100 

Maximum value 

Rock unit with ::50 ppm subpopulation (ppm) 

Siliceous assemblage 

Chert --------------------- 5 2 150 

Quartzite ----------------- 1 5 50 

Shale --------------------- 2 6 70 

Quartz veins -------------- 3 14 100 

Hamburg Dolomite ------------- 10 25 200 

Pogonip Group ---------------- Hanson Creek Formation 

2 11 10,000 

Dolomite ------------------

Quartz veins --------------

Roberts Mountains Formation --

Jasperoid -------------------- Cretaceous granodiorite ------

Quartz latite ----------------

Total----------------------

1 3 

2 7 

4 5 

6 6 

5 

14 

40 

Table 16. Distribution of zinc in rock units 

Units with no samples containing :: 200 ppm zinc are omitted 

Rock unit 

Number of samples 

with :: 200 ppm 

Siliceous assemblage 

Chert ---------------------- 68 

Quartzite ------------------ 2 

Shale ---------------------- 10 

Limestone ------------------ 3 

Quartz veins --------------- 11 

Hamburg Dolomite -------------- 21 

Pogonip Group ----------------- II 

Hanson Creek Formation 

Dolomite ------------------- 8 

Quartz vein ---------------- 211 

Roberts Mountains Formation --- 18 

Jasperoid --------------------- 21 

Silurian and Devonian limestone 5 

Popovich Formation ------------ 8 

Transit ion a 1 assemblage-------- 1 

Tertiary granodiorite --------- 1 

Quartz latite ----------------- II 

Total----------------------- 209 

Percent of Number of samples 

subpopulation with ~ 1 ,000 ppm 

27 9 

9 0 

29 1 

14 1 

50 5 

53 12 

22 3 

20 3 

86 16 

23 6 

19 5 

18 0 

18 1 

8 0 

11 0 

11 0 

211 62 (7 percent) 

200 

70 

70 

100 

70 

200 

Maximum value 

(ppm) 

5,000 

300 

1,500 

1,000 

>10,000 

5,000 

5,000 

10,000 

10,000 

2,000 

>10,000 

500 

>10,000 

200 

200 

500 

65 
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