GEOLOGICAL SURVEY CIRCULAR 606 

Anomalous Concentrations of 

Gold, Silver, and Other Metals 

in the Mill Canyon Area 

Cortez Quadrangle, Eureka · 

and Lander Counties, Nevada 

Anomalous Concentrations of 

Gold, Silver, and Other Metals 

in the Mill Canyon Area 

Cortez Quadrangle, Eureka 

and Lander Counties, Nevada 

By James E. Elliott and John D. Wells 

GEOLOGICAL SURVEY CIRCULAR 606 

Washington 1968 
United States Department of the Interior 

WALTER J. HICKEL, Secretary 

Geological Survey 

William T. Pecora, Director 

First printing 1968 

Second printing 1970 

Free on application to the U.S. Ged/ogica/ Survey, Washington, D.C. 20242 
CONTENTS 

Paee 

Abstract ................................................................................................................................ 1 

Introduction .. .. . .. .. . . .. . . . . . .. .. .. . . .. . . . . . . .. . . . . . . .. .. .. .. .. .. .. . . .. .. .. .. .... .. . . . .. .. . . .. . . .. .. .. . .. . .. .. . . .. .. . . . .. . .. . .. .. . .. . 1 

General geology . . . .. .. . . . . . . .. . . .. . . .. . . .. .. . . . .. .. . . .. .. . . . .. .. .. . . .. . . .. .. .. . .. .. . .. .. . .. .. .. .. . .. . .. .. .. .. .. .. .. . .. . . .. . . . . .. . .. 8 

Ore deposits .................. :....................................................................................................... 8 

Geochemical anomalies .. . . . .. .. . . .. .. . . . .. .. . .. .. .. . .. . . . . .. . .. . .. .. .. .. .. . .. . .. . .. .. . .. .. .. .. . .. . .. .. .. . . .. . . . .. . . . .. . . . .. .. . 5 

Favorable area for exploration ........................................................................................ 7 

Conclusions . . . . . . . . .. . . .. . .. .. .. . .. .. . .. .. .. .. . . .. .. . .. . . .. .. .. .. .. . .. .. . .. . .. . . .. .. .. . .. . .. .. . .. .. .. . .. . .. . .. . .. . . .. .. . .. . .. .. .. .. . .. . 7 

References cited . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .... . . . . . . . . . ... . . . . . . .. . . . . . . . . . . . . . . .. . . . . . . .. . . . . . .. . . .. . . .. . ... . . . . . . . .. . . 7 

ILLUSTRATIONS 

Pap 

FIGURE 1. Index map showing location of Mill Canyon area .. . .. .. . .. .... . .. .. .. .. .. .. . .. . .. .. . 2 

2. Map showing general geology of the Mill Canyon area, including mines, 

mineralized faults, and veins .................................................................... 4 

8. Geologic map and sections of area near mouth of Mill Canyon................ 10 

4-12. Maps showing element distribution: 

4. Gold .................................................................................................... 12 

5. Silver . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . .. . . . . . .. . . . . .. . . .. . . . . . . .. . . . . .. . . . . . . . . . . . . . . . . . . . . . .. . . . . . 18 

6. J.Jead .................................................................................................... 14 

7. Zinc ...................................................................................................... 15 

8. Copper . .. . . . .. . . . . . . . . . . . . .. . . . .. . .. . . . .. . . . . . .. . . . .. . .. . . .... ... .. . .. . . . .. . . . . . . .. . . . . . . . . . .. . . . . . . .. 16 

9. Arsenic .. . .. .. . . .. .. .. . .. . .. . .. .. .. .. . .. . .. .. . .. .. .. .. . .. .... .. .. .. .. . .. .. . .. . .. .. . .. .. . . .. .. . .. . .. .. .. 17 

10. Antimony . . . . . . . . . . . . . . . . . . . . . .. . . . .. . . .. . . .. . .. .. . . . . .. .. . .. . . . . . . . .. . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . 18 

11. Mercury . . . .. . . . . . .. . . . .. . . . . . .. .. . .. . . . . . . . . . . .. .. . . . . . . . . . . . . .. . . .. . . . .. . . . . . . . . . . . . . . . . . . . . .. . . . . .. 19 

12. Tellurium .. . . . . . . .. . . . . . . . . . .. . .. . . . . . . .. . . . . . . .. . . . . . . ... . . . . . . . . . . . .. . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . 20 

TABLES 

TABLE 1. Range of values and median values of samples from the Mill Canyon Page 

area ................................................................................................................. . 6 

2. Range of values and median values of samples collected'for background 

values in the Cortez quadrangle ................................................................ .. 6 

III 

ANOMALOUS CONCENTRATIONS OF GOLD, SILVER, AND OTHER METALS IN THE MILL 

CANYON AREA, CORTEZ QUADRANGLE, EUREKA AND LANDER COUNTIES, NEVADA 

BY JAMES E. ELLIOTT and JOHN D. WELLS 

ABSTRACT 

The Mill Canyon area is in the eastern part of the 

Cortez window of the Roberts Mountains thrust belt 

in the Cortez quadrangle, north-central Nevada. Gold 

and silver ores have been mined from fissure veins in 

Jurassic quartz monzonite and in the bordering Wenban 

Limestone of Devonian age. Geochemical data show 

anomalies of gold, silver, lead, zinc, copper, arsenic, 

antimony, mercury, and tellm·ium. Geologic and geochemical studies indicate that a formation favorable 

for gold deposition, the Roberts Mountains Limestone 

of Silurian age, may be found at depth near the mouth 

of Mill Canyon. 

INTRODUCTION 

Many of the metallic ore deposits of northcentral Nevada occur in regional alinements 

or mineral belts. One of the most economically 

and geologically important, and also one of the 

most conspicuous, of these mineral belts is the 

northwest-trending Battle Mountain-Eureka 

belt (Roberts, 1966, p. 61), which includes the 

Cortez quadrangle. The dominant structural 

feature of north-central Nevada is the Roberts 

Mountains overthrust which juxtaposes Paleozoic siliceous and carbonate rocks of equivalent age. Many metallic mineral deposits are in 

lower plate carbonate rocks exposed in erosional windows of the Roberts Mountains thrust, 

such as the Cortez window. Several gold deposits occur in these lower plate carbonate rocks, 

particularly the Roberts Mountains Limestone 

of Silurian age, and in the breccia zones of the 

thrust. Examples of such deposits are the Carlin, Cortez, and Gold Acres mines (fig. 1) and 

the Bootstrap mine. 

The U.S. Geological Survey has been conducting geologic and geochemical investigations 

under its Heavy Metals program in the Cortez 

quadrangle since July 1966. This report per1 

tains to the Mill Canyon area in the northeastern part of the Cortez quadrangle (fig. 1) in 

T. 27 N., R. 48 E., where lower plate Pal~ozoic 

carbonate rocks are intruded by Jurassic quartz 

monzonite. Preliminary results indicate that 

the relationships among gold and silver deposits, geochemical anomalies, and geologic 

features in the Mill Canyon area are favorable 

enough to warrant further investigation. The 

Roberts Mountains Limestone of Silurian age, 

present at a moderate depth below the surface 

near the mouth of Mill Canyon, and the z0ne of 

altered Wen ban Limestone of Devonian age 

that borders the Mill Canyon stock are favorable hosts for gold deposits. 

Geochemical investigations included collection and analysis of more than 300 rock 

samples. Sample localities are shown in the 

geochemical maps (figs. 4-12). All samples 

were from fault zones, veins, mine dumps, or 

outcrops of altered rock. More than one s!:tmple 

was collected from many of the localities shown, 

but only the highest value for each element 

from a given locality is plotted on the maps. 

All samples were analyzed in the field in mobile laboratories of the U.S. Geological Survey. 

Gold and tellurium were determined by a wet 

chemical method using atomic absorption spectrophotometry. Mercury was deter'llined 

instrumentally by an atomic absorption technique. Thirty elements were determined semiquantitatively on the emission spectrograph. 

The geology of the Cortez quadrang ·~ has 

been mapped and described by Gilluly and Masursky ( 1965). The economic geology of the 

area has been briefly described by En1mons 

(1910) and Vanderburg (1938). 

The authors acknowledge the assistarce, in 

analytical work, of G. H. VanSickle, D. J. 

Grimes, T. G. Ging, Jr., E. L. Mosier, and 
llJOOO' 45' 30' 116°15' 

>-j ~ 

c CARLIN MINE 

Vl 

,0 '-'' n >- ""¢ ';Y ~ >-

f-< 

'<;-~ .,:; :J z 0 :J 

·*" c u 0 

~'<' "f.; -< u :.::: 0 '<' 7 ll..] :::.: 0'<;- 0::: ......1 

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.~ ~ ll..] 

40 

45' .'<' 0 "' ~ 6 ~ <k 

./• 

.rJ /,\, 

s 

30' 

\ 

I 

\ 

I 

\ 

I 

\ 15' 

r·--------------, 

j Area of figure 1 

! • 

I 

·,, NEVADA 

·,, 

·,, 

''--,--, __ f 

5 0 5 10 15 MILES 

FIGURE 1.-Index map showing location of the Mill Can yon area in the Cortez quadrangle, anc1 Carlin, Gold 

Acres, and Cortez gold mines. Base from U.S. Geological Survey, Winnemucca quadrangle, 1:250,000, 1962. 

2 
others of the Geological Survey. Also, the authors thank Mr. Allen Russell for permitting 

access to the mining properties in the Mill Canyon area and for many helpful discussions. 

GENERAL GEOLOGY 

The rocks of the Mill Canyon area include 

Paleozoic sedimentary rocks, intrusive rocks of 

Jurassic age, and Quaternary alluvial deposits 

(fig. 2) . The Paleozoic sedimentary rocks comprise two distinct facies which are approximately equivalent in age; these facies are 

separated by the Roberts Mountains thrust 

fault. One facies includes formations that range 

in age from Cambrian to Devonian and consist 

predominantly of carbonate rocks with minor 

quartzite. The second facies includes formations that range in age from Ordovician to 

Silurian and consist predominantly of siliceous 

rocks. In adjacent areas, Devonian rocks of the 

siliceous facies are also represented. The carbonate facies is considered to be autochthonous 

and the siliceous facies allochthonous. The siliceous facies has been transported into juxtaposition with the carbonate facies from the 

west along the Roberts Mountains thrust 

(Gilluly and Masursky, 1965, p. 10). The rock 

unit mapped as Paleozoic undifferentiated 

occupies the thrust zone and is not directly 

assignable to either the carbonate or the 

siliceous facies. 

Rocks of Jurassic age are the quartz monzonite of the Mill Canyon stock and the 

satellite bodies of alaskite and intermediate 

dikes associated with the stock. In figure 2, 

the igneous rocks are shown as one unit, and in 

figure 3 they are subdivided into quartz monzonite, alaskite, and intermediate dikes. A 

radiometric age determination by the potassium-argon method on a biotite concentrate 

from the Mill Canyon stock yielded an age of 

151 million years ( Gilluly and Masursky, 1965, 

p. 71). 

In general, the sedimentary units strike 

north and dip moderately east. The Roberts 

Mountains thrust has been warped into an antiform (Gilluly and Masursky, 1965, p. 89), and 

later erosion has formed the Cortez window 

in which the carbonate facies is exposed below 

the thrust. The lower plate rocks are cut by 

many faults, most of which are probably related 

3 

to the period of thrusting. The upper plate is 

structurally more complex and is composed of 

many slices of western facies, all faulted 

together with little apparent systen1 ( Gilluly 

and Masursky, 1965, p. 93). 

The Mill Canyon stock intrudes the lower 

plate rocks in the axis of the Cortez window 

and crosscuts the Roberts Mountains thrust to 

the east. The stock is composite and consists of 

two parts: ( 1) a discordant western part, 

roughly rectangular in outline, and (2) ar eastern laccolithic or bysmalithic lobe ( Gilluly and 

Masursky, 1965, p. 68). Several mineralized 

veins are near the junction of the two parts of 

the :Mill Canyon stock (fig. 2, left of ce"'lter) . 

ORE DEPOSITS 

Deposits in the Mill Canyon area have been 

prospected and mined for the past 100 years. 

The estimated total production from the area 

is approximately $800,000. Vanderburg (1938, 

p. 26) estimated the total production prior to 

1937 at $200,000. The remaining $GOO,OOO was 

produced mostly in the years 1937-42 (U.S. 

Bureau of Mines, 1938-59). Most of the n1ining 

has been in gold and silver, the gold predominating in dollar value. The ore deposits are of 

three types: ( 1) fissure veins in quartz monzonite that contain silver, lead, zinc, anc1 gold, 

(2) silver, lead, and zinc replacement d€.posits 

in limestone (Vanderburg, 1938, p. 27), and 

(3) gold deposits along fault zones in limE.stone. 

The most productive deposits have been nearsurface oxidized ore along faults in limestone 

near the quartz monzonite-limestone cr"ltact. 

Several of the more important mine<: and 

workings and the mineralized faults and veins 

are shown in figure 2. Few of the mine workings are now accessible. In the quartz monzonite the main ore-bearing structures trend 

north-northeast to north-northwest and dip 

steeply. Near the southern border of the stock, 

at the Emma E mine (the southernmost mine 

shown in fig. 2), the main fault strikes northwest and dips 50°-75° NE. Near the northern 

border of the stock, deposits in the Wen ban 

Limestone are along extensions of the northnortheast and north-northwest trendf and 

along faults which are parallel to the instrusive 

contact (fig. 3). These faults generally trend 

east to northeast and dip 35°-40° N. or NW. 
2000 0 2000 4000 FEET 

FIGURE 2.-General geology of the Mill Canyon area. Geology by Gilluly and Masursky (1965); modified by 

Elliott. 

4 
EXPLANATION 

Quaternary alluvium 

Jurassic quartz monzonite, alaskite, 

and intermediate dikes 

Paleozoic sedimentary rocks 

Pzl, lower plate carbonate facies 

Pzu , upper plate siliceous facies 

Pzs , undifferentiated 

-------- Contact 

Dashed where approximately located 

__ _,___---... High-angle fault, showing direction of dip. 

Dashed where approximately located; 

dotted where concealed _......_ __ ...... __ ~ 

Thrust fault, sawteeth on upper plate. 

Dashed where approximately located 

Vein, showing dip 

~ 

Mine 

APPRO X I MATE MEAN 

OECLINATI0N, 1968 

FIGURE 2.-Continued. 

5 

The mineralogy and mineral associationf of 

the gold-silver ores were studied in 38 polished 

sections of ore specimens. The specimens were 

obtained mainly frorri unoxidized vein material 

on mine dumps. The predominant primary sulfide minerals are pyrite, arsenopyrite, 

sphalerite, and galena. Boulangerite, bournonite, argentian tetrahedrite, chalcopyrite, 

pyrargyrite-proustite, gold, and stibnite commonly occur in minor amounts. Vanderburg 

(1938, p. 27) noted the occurrence of argentite 

and stephanite also. Arsenic and antimony are 

generally abundant in the ores. Tellurium and 

mercury are present in anomalous concentrations. 

One of the main purposes of this study Fas 

to determine the sites and modes of occurre~ce 

of the gold and silver. Most of the silver i~· in 

argentian tetrahedrite; some occurs as ruby 

silver minerals. Silver-rich samples usu~.lly 

contain abundant sulfosalts of lead, copr~r, 

silver, and antimony, such as boulanger;te, 

bournonite, tetrahedrite, and ruby silver minerals. Gold, where seen in polished sections, 

occurs as blebs ( 5-40 microns across) in pyrite 

or, rarely, in arsenopyrite. Amounts of gold 

and silver vary somewhat independently ~.nd 

may reflect different phases of mineralization. 

GEOCHEMICAL ANOMALIES 

The Mill Canyon area contains anomalous 

amounts of gold, silver, lead, zinc, copr~r, 

arsenic, antimony, mercury, and tellurium 

(figs. 4-12). Locally, anomalous amounts of 

other elements are present. The highest ancmalies lie in a northwest-trending belt and occur 

in the quartz monzonite and the adjoining Wenban Limestone of Devonian age. The anomaJ~es 

in the quartz monzonite are concentrated alcng 

north-trending fissure veins where the east lobe 

and the west part of the stock join. The anom.alies in the Wen ban Limestone are concentrated 

in faults and altered zones. Although most of 

the mineralized Wen ban Limestone is near the 

contact of the quartz monzonite, some of the 

mineralized limestone occurs near the Roberts 

Mountains thrust near the mouth of Mill 

Canyon. 

A summary of data (table 1) shows the 

range of values and median values for most of 
the samples from the Mill Canyon area. Table 2 

presents analyses of samples selected in the 

Cortez quadrangle from apparently unaltered 

country rocks to obtain background values for 

gold, silver, lead, zinc, copper, arsenic, antimony, and mercury. No background data are 

available for tellurium. Of the background samples, 11 were from quartz monozite and alaskite, 

38 from lower plate rocks, and 20 from upper 

plate rocks. The high concentration of all metals 

in the Mill Canyon area is striking when compared to the background values. 

The analytical results pertaining to the Mill 

Canyon samples were treated statistically. A 

most valuable statistical treatment, for the 

purposes of this study, is that of correlation 

analysis, which measures the degree of similarity between different pairs of variables, such 

as between gold and silver or between lead and 

and zinc. The correlation coefficient may range 

from -1.0, a perfect negative correlation, to 

+ 1.0, a perfect positive correlation. A high 

negative correlation signifies that as one element (for example, gold) increases, another element (for example, silver) decreases proportionately or vice versa. A high positive correlation indicates that both elements increase or 

decrease proportionately. A low positive or 

negative correlation coefficient-one that apTABLE 1.-Range of values and median values, in parts 

,per million, of samples from the Mill Canyon area 

Element Minimum Maximum Median No. of samples 

Au ------------- <0.1 160 <0,1 273 Ag ------------- <.5 5,000 1.5 273 Pb ------------- <10 >10,000 25 273 Zn ------------- <200 >10,000 <200 273 Cu ------------- <2 >5,000 60 273 As ------------- <200 >10,000 600 273 Sb ------------- <100 >10,000 100 273 Hg ------------- <.05 >10 .5 273 Te ------------- <.1 62 .1 305 

TABLE 2.-Range of values and median t'alues, in parts 

per million, of samples collected for background 

values in the Cortez quadrangle 

Element Minimum Maximum Median No. of samples 

Au ------------ <0.02 0.1 <0.02 69 Ag ------------ <.5 5 <.5 65 Pb ------------ <10 100 10 63 Zn ------------ <200 300 <200 69 Cu ------------ <5 300 10 69 As ------------ <200 <200 <200 69 

Sb ------------ <100 300 <100 69 Hg ------------ <.01 .95 .10 56 

6 

proaches zero-shows that the t~vo elements 

act fairly independently of each other. 

Correlation analysis was applied to geochemical samples collected in the Mill Canyon area 

to test the relations among anomahus elements 

and to test the use of certain elements as indicators of mineralization. 

As a first test, 106 samples from veins and 

fault zones in the quartz monzonite stock were 

compared. The results showed strong positive 

correlations between the element pairs: goldlead, gold-copper, gold-antimony, gold-iron, 

silver-lead, silver-antimony, silver-copper, silver-iron, lead-copper, lead-antimory, lead-iron, 

copper-antimony, copper-iron, and antimonyiron. The element pair gold-silver had a low 

positive correlation. Little or no correlation was 

indicated ·for all other possible ele'"tlent pairs. 

In a second test, 273 samples cdlected from 

all rock units in the Mill Canyon area were 

compared. Relalionships established for samples from the quartz monzonite sto~k thus were 

tested for the area as a whole. E'~ment pairs 

showing strong positive correlatior.;; were goldarsenic, silver-lead, silver-copper, silver-antimony, lead-copper, lead-antimony, and copperantimony. The element pair gold-silver had a 

very low positive correlation. All other element 

pairs showed little or no correlation. 

The strong positive correlations for samples 

from the quartz monzonite stock involving gold 

as one element of the element pair did not hold 

true for the area as a whole, whereas most of 

the strong correlations involving silver did 

hold true. The results of the stat~stical treatment support the geologic evidence from the 

study of polished sections. The conclusions are: 

1. Silver is found in sulfosalt suites of silver-, 

lead-, antimony-, ·and copper-b-:l.aring minerals, such as tetrahedrite, }~')ulangerite, 

bournonite, and ruby silvers or oxidized 

equivalents of these suites, both in the Mill 

Canyon stock and in the bordering rocks. 

2. In the igneous rocks, gold also occurs with 

the sulfosalt suite of minerals and is associated with iron in pyrite. However, the behavior of gold with respect to silv€r is erratic. 

3. In samples taken from all rock types, gold 

is somewhat erratic and shows a preference 

only for arsenic, perhaps reflecting an association with arsenopyrite. 
Geochemically the best indicator elements for 

gold and silver are: ( 1) lead, copper, and antimony for gold and silver in the quartz monzonite stock, (2) lead, copper, and antimony for 

silver in the bordering country rocks, and ( 3) 

arsenic for gold in the bordering country rocks. 

Locally, however, other elements, such as mercury or tellurium, may be i1nportant indicators 

of gold and silver deposits. 

FAVORABLE AREA FOR EXPLORATION 

The most favorable area for exploration is a 

roughly rectangular block of Wen ban Limestone. locally mineralized and altered, near the 

mouth of Mill Canyon. The area is bordered on 

the west and south by quartz monzonite, on the 

east by the Roberts Mountains thrust, and on 

the northwest by the Crescent Valley fault 

(fig. 3). Lithologically this block of limestone 

is similar to the lower 1,000 feet of Wenban 

Limestone at the type section, 4 miles to the 

southwest in Cortez Canyon. Early Devonian 

fossils have been collected from the upper part 

of this block near the mouth of Mill Canyon 

(Gilluly and 1\;Iasursky, 1965, p. 32). The limestone has been bleached and partly silicified 

for as much as 1,000 feet fron1 the intrusive 

contact. The bleaching has changed the normal 

medi urn gray or dark gray of the limestone to 

a light buff. Locally, extreme silicification has 

resulted in the forn1ation of dense brown jasperiod. Geochemically this area is anomalous 

in gold, silver, lead, zinc, copper, arsenic, antimony, mercury, and tellurium, especially near 

the instrusive contact. 

Inasmuch as some of the major gold deposits 

in north-central Nevada occur in the Roberts 

Mountains Limestone, the same rocks should be 

considered in the Mill Canyon area as a favorable host for gold deposits. The new Cortez 

gold discovery is only 11;2 miles to the west of 

Mill Canyon. The gold at this locality is concentrated in the Roberts Mountains Limestone 

just below the Wenban Limestone and is associated with anomalies of mercury, arsenic, antimony, and tu~gsten (Wells and others, 1967). 

These elements, with the exception of tungsten, 

also occur in anomalous concentrations in the 

northwestern part of the Mill Canyon area. 

7 

The Roberts Mountains Limestone is not exposed at the surface near the mouth of Mill 

Canyon but would be expected to occur at a 

shallow depth. Cross sections in figure 3 show 

the interpreted subsurface geology near the 

mouth of Mill Canyon. From these cross sections, the Roberts Mountains Limestone if estinlated to be 300-1,500 feet below the surface. 

Favorable zones for gold deposits may be present near the intersection of projected vein 

structures and the Roberts Mountains-Wenban 

contact. 

The geochemical association of metals in the 

zone of alteration in the Wen ban Lime~ tone 

adjacent to the Mill Canyon stock is also similar 

to that in the Cortez deposit. This similarity 

suggests that physical exploration for ar economic evaluation of this area is justified. 

CONCLUSIONS 

Geologic studies show the Mill Canyon area 

to be mineralized and to have a geochemic:d association of metals that is similar to th~ associations in the Cortez, Carlin, and other gold 

mines in north-central Nevada. Potential mineralized rock is untested at depth, but on the 

basis of this evidence some exploration vrould 

appear justified. In particular, the Ro"">erts 

Mountains Limestone is favorable to test and 

sample because of its known association with 

gold deposits in this area. 

REFERENCES CITED 

Emmons, W. H., 1910, A reconnaissan<'~ of 

some mining camps in Elko, Lander, and 

Eureka counties, Nevada: U.S. Geol. Survey Bull. 408, 130 p. 

Gilluly, James, and Masursky, Harold, 1965, 

Geology of the Cortez quadrangle, Nevada, 

'With a section on Gravity and aeromagnetic surveys, by D. R. Mabey: U.S. Geol. 

Survey Bull. 1175, 117 p. 

Roberts, R. J., 1966, Metallogenic provincef and 

mineral belts in Nevada, in AIME Pacific 

Southwest Mineral Industry Conf., Sparks, 

Nev., 1965: Nevada Bur. Mines Rept:. 13, 

Papers, pt. A, p. 47-72. 

U.S. Bureau of Mines, 1938-59, Minerals yearbook [annual volumes for years 1937-58]: 

Washington, U.S. Govt. Printing Office. 
Vanderburg, W. 0., 1938, Reconnaissance of 

mining districts in Eureka County, N evada: U.S. Bur. Mines Inf. Circ. 7022, 66 

p. 

8 

Wells, J.D., Erickson, Ralph, and Ptoiser, L. R., 

1967, Geology and mineralogy of the Cortez 

gold deposit, Nevada [abs.]: Mining Eng., 

v. 19, no. 12, p. 40. 

133.:1 oooz 

01 

13A31 V3S NV31'j Sl Wn!VO 

!33~ 09l l't'A!I31NI !lnOlNOO 

0001 0 0001 

~~~~~~,-~--~~T=o~~--~r?TO~<rr~-r~~~~~~~~--~~~~~~~~r-~~~,1! 

.ov 
6500' 

6000' 

5500' 

5000' 

4500' 

6500' 

6000' 

5500' 

5000' 

~jDWij Devonian Wenban Limestone 

Owa. altered 

~ 

~ 

Silurian Roberts 

Mountains Limestone 

Silurian 

-

Fourmile 

Canyon Formation 

t·:·:::.~(::j Quaternary alluvi urn 

1"9!~~t~J •.:-,·.,t~h' 

Jurassic intrusive rocks 

.Jd, intermediate dikes 

Jal, alaskite 

Jqrn, quartz monzonite 

EXPLANATION 

Paleozoic 

~ rocks 

undifferentiated 

I­

~~~ :;:,-

' I 

I 

11 

.... Contact 

Dashed where approximately located; 

dotted where concealed 

L._ __ _ 

High-angle fault, showing direction of dip. 

Dashed where approximately located 

. . Thrust fault, sawteeth on upper plate. 

Dashed where approximately located 

Vein, showing dip 

Dot where mineralized 

25 ___1.__ 

Strike and dip of beds 

® 

Probable extension of vein 

From surface and underground workings. 

Shown on section A-A 'only 

A' 

B' 
0 

Q 

Q 

Q 

Qa1 

8 

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116"35' 

Q 

Q 

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Q 

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Jqm 

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"V;' .a.PPROX!MATE ME-'N 

OECUNAllON, 1968 

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GOLD IN PARTS PER MILLION 

f\u 

<0.1 

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Q 1.0-10 

• >10 (value shown) 

~m 

Jqm 

0 

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0 0 0 

f\u 

1 MILE 

116'33' 

0 

23 

0 

0 

Kl 

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FIGURE 4.-Gold distribution, maximum concentration in all samples at each locality. Geologic symbols 

explained in figure 2. 

12 
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2000 

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IN PARTS PER MILLION 

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Q 20-200 

• >200 (value shown 

where 21000) 

0 

0 

0 

0 

o e 

0 

0 

1 MILE 

0 

0 

0 

0 

e 

0 0 

0 

0 

SILVER 

FIGURE 5.-Silver distribution, maximum concentration in all samples at each locality. Geologic symbols 

explained in figure 2. 

13 
LEAD 

0 

0 ,.• 

e 

,, 

I 

\ 

e 

• 

0 

0 

·~ 

• 

0 

0 

0 

0 e 

0 

0 0 

8 

0 

0 

0 

---- ~· --~-e---- -- -

liz 

0 

0 

0 e 

0 

0 0 

LEAD IN PARTS PER MILLION 

0 

1 MILE 

0 <20 

0 20-190 

e 200-990 

l;J 1000-5000 

• >5000 

0 

0 

0 

0 

0 

0 

0 

FIGURE 6.-Lead distribution, maximum concentration in all samples at each locality. Geologic symbols 

explained in figure 2. 

14 
e 

e e e 

"I 

_J e 

e 

i • L __ _ 

j l 0 

,,/"e o! 

• 

I 

r 

l 

~t 

., 

• e 

lj I -~t ~li ~ I • 

~ l.1o • 9 

• e 00 

• 

• 

• 

' e 

,-~--

• 

0 

e : e 

~ 

e 

----9~ 

• 

• 

•• 

• 

~ 

e 

ttl 

e ~ 

e 

'•l' 

e 

e 

~-<>o9 

0 

-,---

'h 

e 

~. 

oo e ~ 

e 

• 

e 

ZINC IN PARTS PER MILLION 

e 

9 

e 

1 MILE 

0 <200 

e 200-990 

~ 1000-5000 

• >5000 

e 

e 

e 

e 

e 

e 

ZINC 

FIGURE 7.-Zinc distribution, maximum concentration in all samples at each locality. Geologic symbols 

explained in figure 2. 

15 
I 

llil 

lil 

I 

lil 

0 •• 

0 

lil 

., 

~~---~ 

/ j 

,.F~"& 

0 

lil 

• 

0 

0 

0 

0 

lil lilljl lil • 

lil 

COPPER 

IN PARTS PER MILLION 

0 

0 <20 

0 20-99 

lil 100-1000 

• >1000 

0 

0 lil 

0 

' 0 

Jqm 

0 

• 

COPPER 

0 

0 

• 

q, 

lillil 

0 

0 

0 

lil 

0 

Oil lil 

0 

0 

0 

0 

lil 

0 

olil lil 

lil 

lil 

lil 

0 

0 

0 

0 

lil 

lil 

lil 

-- -~ --~·~ ---------... --------~--~-~--·-----=---'--··-----~---- --·-------..L.. 

0 1 MILE 

FIGURE 8.-Copper distribution, maximum concentration in all samples at each locality. Geo <:~gic symbols 

explained in figure 2. 

16 

I 

1 

j 
Qal 

0 8 

0. il 

\( e« 

I 

\ 

(: 

e 

e 

• t 

Jqm 

• 

----

Ptl 

0 

• 

e 

• 

• 

0 

0 

e ' e 

• 

0 

e 

ee 

• • 

~~~ 

P,l 

0 e 

Jqm 

• 

• 

0 

0 

34' 

••• 

0 

e 

• •• .. • 

0 

ARSENIC 

IN PARTS PER MILLION 

Pw 

0 <200 

0 200-990 

e 1000-5000 

• >5000 

0 

Jqm 

0 

0 

0 

~m 

0 

0 0 0 

e 

e 

Ptu 

0 

0 

e 

0 

116"33' 

0 

...,o 0 

e 

0 

0 0 

~-( ~~ e 

40·~----~~--------------~-------------------------------------+--------------~~------------------4---i 10' 

• 0 

0 

0 1 MILE AR~-=:NIC 

FIGURE 9.--Arsenic distribution, maximum concentration in all samples at each locality. Geologic SyJ"lbols 

explained in figure 2. 

17 
; 16'35' 

Qal 

0 

• 

0 

0 • 

0 

• 

34' 

•• • 

ANTIMONY 

IN PARTS PER MILLION 

0 <100 . 0 100-490 

.• 500-2000 

• >2000 

Jqm 

116"33' 

0 0 

0 

il~----------------------~----~·----------------------------~-4~-------------------------------t~ 

0 

0 

0 0 

" 0 0 0 

• 0 0 

Q 0 

Atu 

0 

0 

P.d 0 

0 0 0 0 

• 0 

At I • • 0 

0 0 

• 0 

ANTIMONY 0 

FIGURE 10.--Antimony distribution, maximum co:q.centration in all samples at each locality. Ge.ologic symbols 

expl~ined in figure 2. 

18 
0 

0 

Jqm 

APPROXIMATE MtAN 

DECLINATION, 19M 

Q 

~ 

" " 'b 

0 

0 

Q 

Q 

0 

0 

0 

0 

" 

0 

0 

0 

0 

Q •o 0 0 

Jqm 

0 

• 0 0 

"e 0 

0 

0 

• 

34' 

0 

Q 

MERCURY 

IN PARTS PER MILLION 

0 <0.1 

0 0,1-0.99 

" 1-5 • >5 

0 

Jqm 

0 

~m 

0 Q 

0 

0 

I 

01 

I 

"' ~ /"'" J " Q " I 0 

0 0 0 

0 

0 

0 

F\u 

0 0 0 

" " • " 

MERCURY 

FIGURE 11.-Mercury distribution, maximum concentration in all samples at each locality. Geologic symbols 

explained in figure 2. 

19 
Pzl 0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 0 

0 0 

0 0 

0 

0 

Q 

fld 

TELLURIUM 

IN PARTS PER MILLION 

0 <0.1 

0 0.1-0.3 

8 0.4-1.0 

• > 1.0 

0 

0 

0 

0 

0 0 0 

0 

0 

0 0 

0 

0 

0 

0 

0 

0 

L--------------.JI....----...J.L----------------1-------~---'0':1_-L ____ ~------

TELLURIUM 0 1 MILE 

0 

j 

I 

~ ~0 I 

0 'j 

I 

I 

I 

I 

0 I 

I 

FIGURE 12.-Tellurium distribution, maximum concentration in all samples at each locality. Geologic symbols 

explained in figure 2. 

20