Geochemical Prospecting

Studies in the Bullwhacker

Mine Area, Eureka District

Nevada

GEOLOGICAL SURVEY BULLETIN 1000-H

CONTENTS

	Page

Abstract ___._-___ ___-__..-_ . 397

Introduction.----.._______________________________________________ 397

Geology ------... ............... .. - 397

Geochemical prospecting.__________________________________________ 401

Sampling method _ __ ___- ___ _- ___ _ 401

Analytical methods._________________________________ _______ 402

Analytical precision _________ _____________________________ 404

Method of analysis of analytical data____-_--____---______-______ 405

Results of investigation________________________________________ 405

References cited ____-_____---____----___-_-----______-_--__---_-__ 407

ILLUSTRATIONS

Page 

FIGURE 33. Index map showing location of the Bullwhacker mine area. _ 398

34. Geologic map of the Bullwhacker mine area.________ 399

35. Map and histogram showing the distribution of lead in soils

of part of the Bullwhacker mine area ________________ 401

36. Map and histogram showing the distribution of zinc in soils

of part of the Bullwhacker mine area__________________ 402

37. Map and histogram showing the distribution of arsenic in

soils of part of the Bullwhacker mine area._____________ 403

TABLES

TABIE 1. Generalized descriptions of sedimentary rock units in the

Bullwhacker mine area, Eureka district, Nev_______ 400

2. Replicate analyses of two soil samples by colorimetric

methods__ _______________________________________ 404

in

CONTRIBUTIONS TO GEOCHEMICAL PROSPECTING FOR MINERALS

GEOCHEMICAL PROSPECTING STUDIES IN THE BULLWHACKER MINE AREA, EUREKA DISTRICT, NEVADA

By ALPEED T. MIESCH and THOMAS B. NOLAN

ABSTRACT

Investigation of the distribution of lead, zinc, and arsenic in soils of the Bullwhacker mine area, Eureka district, Nev., indicates dispersion patterns of these 

three metals in residual soils over near-surface ore at the Bullwhacker mine. Ore 

at greater depth in the shaft of the T. L. mine, however, is not reflected in lead, 

zinc, and arsenic contents of the soils.

The dispersion patterns are secondary residual soil anomalies in the classification 

given by H. E. Hawkes.

INTRODUCTION

This study was undertaken to determine whether geo chemical 

prospecting methods which have proved valuable for finding ore in 

other districts can be successfully applied to exploration for new ore 

deposits in the Eureka district, Nevada. The ore deposits, which 

were mined as early as 1864 (Curtis, 1884, p. 3), have been valuable 

principally for their lead, silver, and gold.

The Bullwhacker mine area is on Mineral Point in the northern 

part of the Fish Creek Range, approximately \% miles northwest of 

the town of Eureka, Eureka County, Nev. (fig. 33). This area was 

selected for investigation because the distribution of ore in the area is 

relatively well known from drilling and mining.

James Prentice, under the supervision of T. S. Lovering, collected 

the samples for this study. All analyses were made by H. E. Crowe, 

of the U. S. Geological Survey.

GEOLOGY

The Bullwhacker mine area is underlain by a gently dipping sequence of sedimentary rocks of Cambrian and Ordovician age which 

have been intruded by a sill-like mass of quartz porphyry (fig. 34)

A general description of the sedimentary rocks is given in table 1.

A complete description of the sedimentary rocks in the vicinity of 

Eureka is given by Nolan and others (1956).

The general northeast dip of the sediments is interrupted to the 

west and the south by poorly defined domal upwarps, and numerous 

faults of relatively small throw cut the tilted and domed beds. The 

quartz porphyry appears to be younger than the faults.

467657 68 397
398 CONTRIBUTIONS TO GEOCHEMICAL PROSPECTING FOR MINERALS

N 

DIAMOND VALLEY A

30'

FIOUBE 33. Index map showing location of the Bullwhacker mine area (see fig. 34), Eureka district,

Nevada.

The quartz porphyry forms an irregular sill-like mass over much 

of the area. It appears to have been intruded partly as a sill along 

the contact between the Dunderburg shale and the Windfall formation and partly as a dike along one or more of the faults that cut 

this contact. Information obtained by drilling, however, shows that 

its general habit is sill-like. Most of the rock is hydro thermally altered, 

and only the quartz phenocrysts remain unaltered. There has been 

little or no alteration of the invaded rocks.
GEOCHEMICAL PROSPECTING STUDIES, EUREKA DISTRICT, NEV. 399

EXPLANATION

::';'££/X Op 1,-'/-'. 

-.-;/ v.V.>--'.v.V:.

Hamburg dolomite

ik a

Contact, showing dip

Long (fashed where approximate,

short dashed where inferred

Fault, showing dip 

Long dashed where approximate, 

short dashed where inferred; 

dotted where concealed

10 

Strike and dip of beds

B 

Shaft

1 Holly

2 Williamsburg

3 Bullwhacker

4 T. L.

5 Helen

1000

I_

Geology by T. B. Nolan, 1954

2000 Feet.

Drill hole, barren

 

Drill hole, ore

II ___ L_

Sample ( trayerses 

FIGURE 34. Geologic map of the Bullwhacker mine area (see flgs. 35,36, 37) .[Eureka district, Nevada.

The most conspicuous faults strike north-south, and are easily 

recognized by displacements of the contact of the Dunderburg shale 

and Windfall formation. Two eastward-trending fractures of relatively slight throw, however, appear to have been important in 

localizing the group of ore bodies between the Bullwhacker and 

Holly mines.
400 CONTRIBUTIONS TO GEOCHEMICAL PROSPECTING FOR MINERALS

TABLE 1. Generalized descriptions of sedimentary rock units in the Bullwhacker 

mine area, Eureka district, Nevada

Series

Lower Ordpvlclan

Upper Cambrian

Middle and Upper 

Cambrian

Bock unit

Pogonip group

Windfall 

formation

Bullwhacker 

member

Catlin member

Dunderburg shale

Hamburg dolomite

Thickness 

(feet)

1,600

400

250

265±

200+

Description

Thick-bedded limestone, mostly 

cherty

Uniform thin-bedded sandy limestone. Ore bearing at Bullwhacker mine.

Limestone with interbedded sandy 

or shaly limestone. Commonly 

cherty.

Brown-weathering shale. Poorly exposed. Interbedded nodular and 

fossiliferous limestone.

Thick-bedded dark-gray dolomite. 

Thoroughly fractured in most 

places. Locally silicificd, especially near contact with Dunderburg shale.

Although mineralized ground is widespread, as is reflected by the 

numerous prospect pits throughout the area, minable ore bodies in 

the area shown on figure 34 have been found only in the limestones 

of the Windfall formation and the Pogonip group near the surface 

in the belt from the Bullwhacker mine to the Holly mine and in 

a deeper zone that is near the base of the Hamburg dolomite in the 

vicinity of the T. L. shaft.

The ore bodies in the Bullwhacker and Holly mines are reported 

by Roland Blanchard (Oct. 1922, written communication) to be 

oxidized lead-silver-gold replacement bodies in limestone beds adjacent to steep crosscutting fissures, which were also mineralized. 

Although little of the ore remains to be seen, it is probable that it 

was in large part composed of plumbojarosite and other oxidized 

lead minerals and an abundance of "mineral" limonite. The ore 

bodies seem not to have extended more than a few tens of feet away 

from the fissures in the favorable limestone beds. These ore shoots 

were mined out many years ago.

Newly discovered ore shoots in the T. L. mine are also largely 

oxidized, though they lie from 200 to 400 feet below the groundwater table, which is about 635 feet below the surface. The ore 

shoots are irregular gently dipping lenses that are composed of pods 

and veinlike bodies of ore minerals in fractured dolomite. Some 

galena remains in the ore shoots, but anglesite, cerussite, plumbojarosite, and limonite appear to be the most abundant minerals.

The oxidized ore bodies at both the Bullwhacker and the T. L. 

mines are characterized by the presence of arsenic, probably in the 

mineral beudantite. They also contain small amounts of oxidized
GEOCHEMICAL PROSPECTING STUDIES, EUREKA DISfTRTCT, NEV. 401

zinc minerals. Sulfide ore cut by the workings in the T. L. mine 

contains pyrite, galena, sphalerite, and arsenopyrite.

GEOCHEMICAL PROSPECTING

SAMPLING METHOD

The samples collected for analysis in this study are soil grab 

samples and were taken at approximately 100-foot intervals along 

4 major traverses and several minor traverses (figs. 34, 35, 36 and 37). 

The samples were taken from the upper 3 or 4 inches of the soil layer. 

The general flat surface of the Bullwhacker mine area suggests that 

transportation of soils has been minor. The soils sampled are 

largely residual.

The soil samples were taken without regard to parent material; 

hence, the sample traverses cross geologic boundaries separating 

limestone, shale, and quartz porphyry (fig. 34). No pronounced or 

consistent variation of metal content with type of parent material was

x° \

FX E 1 

E XE j

\ § BULLWHACKER

\ \ . / SHAFT/

\ \x' / F /

\D FX<^ *XE D /

GX\ X Q /

A\ *#C

X Cl rl f / * XC to. x/ / xf,.

/XE / X B

I J>/ B

v V x %

V-' XA xA XXC

A X* xA

AX X. XA c X B

* * x c XB

X X g

X* xA X ° /^\X

T. L. SHAFT* XA fx X°'\

-X XI vv

A ° XA Xfl 1

A X XB |

XA X* A P>VX C

x* X \X°''V

X" X

B I

XA A * '

A X

X

C

X

A 1 7-', 

X Jl

B A

x. £ /£

AX XA S j

» VA O z /*

X " /"

x° ^ y?

X B

XA

X*

50-

W40-

UJ

CL

1-

u. 

0

£J20-

m _ .

5

3 

ZIG- .

o ..,.., , ,..l.,_r~i , .

LEAD (PPM) 2 3 85.3,3,8,8 " N r * s

i __ i

3 1 ®

88

MAP SYMBOL n , : D E F Q H 1 

HISTOGRAM

EXPLANATION

X°

Location of soil sample and range of 

lead content shown by map symbol

Sea histogram

o

Drill hole, barren

J Drill hole, ore

 120 - 

Isopleth of lead content of soil.

in parts per million. Isopleth

Interval is a factor of 8

500 0 900 Feet

FIGURE 36. Map and histogram showing the distribution of lead in soils of part of the Bullwhacker mine

area, Eureka district, Nevada. 

467557 58 2
402 CONTRIBUTIONS TO GiBOCHEQVEI'OAL PROSPECTING FOE MINERALS

noted, though a consistent variation might be found using more 

precise analytical methods. At least, such variation is too minor 

to be detected with the type of analyses used for this investigation 

and is overshadowed by the magnitude of other variations that have 

been detected.

3 D BULL WHACKER 

SHAFT

ZINC (PPM);

MAP SYMBOLA B c o E F 

HISTOGRAM

EXPLANATION

Location of soil sampled and range of

zinc content shown by map symbol

See histogram

p Drill hole, barren

Drill hole, ore

 5/ 

Isopteth of zinc content of soil, in 

parts per million. Isopleth 

interval is a factor of 33/8

500

I_

500 Feet

_J

FIOXJBE 36. Map and histogram showing the distribution of zinc in soils of part of the Bullwhacker mine

area, Eureka district, Nevada.

ANALYTICAL METHODS

The methods of lead, zinc, and arsenic determination used in this 

investigation were developed or modified for use in geochemical 

prospecting (Lakin and others, 1952, p. 14, 21: Almond, 1953, p. 8). 

Lead and zinc are determined using the heavy-metal reagent dithizone 

(Sandell, 1950, p. 87-111) in a carbon tetrachloride solution. Colors 

exhibited by the lead and zinc dithizonates in solution are compared 

visually with standard solutions. Up to 35 lead determinations or 

60 zinc determinations can be made per man-day under favorable 

conditions.
GEO'CBEMICAL PROSPECTING STTJDIEIS, EUREKA DISTRICT, NEV. 403

_ -^yx

x°

c * x°

/ B BULLWHACKER 

I SHAFT

<t>

XD

X° O X°

T. L. SHAFT

x° xo 

x°

XB

xc xc

Cv x x* r B .

*°

,B X«

40-

fezo-

 »» F

11

ARSENIC ' S R

(PPM)

MAP SYMBOL A B c

HISTOGRAM

EXPLANATION

Location of soil sampled and range of

arsenic content shown by map symbol

Sea histogram

o 

Drill hole, barren

Drill hole, ore

Isopleth of arsenic content of soil, 

In parts per million. Isopleth 

interval 'is a factor of 3 3/a

FIOURE 37. Map and histogram showing the distribution of arsenic In soils of part of the Bullwhacker 

mine area, Eureka district, Nevada.

Arsenic is determined by the Gutzeit method involving the passage 

of gases evolved from an acidified sample solution through lead 

acetate to a confined spot on mercuric chloride paper. The color of 

the confined spot is compared visually with spots obtained from 

standard solutions.

Twenty-one samples from the Bullwhacker mine area were also 

analyzed for silver by a method described by Lakin and others (1952, 

p. 22). Some dispersion of silver in waUrock adjacent to ore in the 

Eureka district was reported by Curtis (1884, p. 82-87). The soil 

samples analyzed for this investigation, however, all contained less 

than 0.2 ppm (parts per million) silver. Many of the samples 

analyzed for silver were those highest in lead, zinc, and arsenic content.
404 CONTRIBUTIONS TO GEOCHEMDCAL PROSPECTING F0« MUNERAiLS

ANALYTICAL PRECISION

An estimate of the precision of the lead, zinc, and arsenic determinations may be obtained by examination of the two sets of replicate 

analyses given in table 2. The replicate analyses were made during 

the course of the other analytical work done for this report and by 

the same analyst. Approximately every eighth or ninth sample 

analyzed was a split of 1 of the 2 control samples. One large soil 

sample was split into two fractions by the analyst (samples 1 and 2, 

table 2). Sample 2 was then "salted" with high-grade oxidized lead 

ore. It is suspected that some of the variation between lead determinations on sample 2 may be due to incomplete mixing of the soil 

and lead ore mixture, through the arsenic and zinc determinations on 

this sample are in close agreement.

The total range of variation of replicate lead determinations is 

limited to three of the logarithmic classes used on the maps (fig. 35); 

the maximum spread is 4 times or 300 percent. However, determinations of lead in sample 1 which was not "salted" are in closer agreement. These determinations are limited to two of the log classes, 

and the maximum spread is only two and one-half times or 150 

percent. The maximum deviation of lead determinations on sample 1 

from the mean of the 9 replicate determinations is 60 percent.

TABLE 2. Replicate analyses of two soil samples by colorimetric methods (results

in parts per million)

[Values in parentheses are map symbols (figs. 35,36, and 37) which are labels for logarithmic classes]

Sample 1

Pb

200 (D) 

120 (D) 

100 (C)

150 (D)

100 

100 

200

80 

100

C) 

C) 

D)

0) 

C)

As

200 (H) 

40 (D) 

60 (E)

50 (D)

20 (B) 

60 (E) 

60 (E)

60 (D) 

40 (D)

Zn

100 (C) 

50 (A) 

100 (C)

50 (A)

50 (A) 

60 (A) 

100 (C)

100 (C) 

70 (B)

Sample 2

Pb

25, 000 (E) 

30, 000 (K) 

15, 000 (J)

15, 000 (J)

40, 000 (L) 

60, 000 (L) 

20, 000 (K)

15. 000 (J) 

15, 000 (J)

As

300(1) 

300(1) 

500 (J)

400 (J)

600 (J 

600 (J 

400 (J

300(1 

400 (J

Zn

1.600(J) 

1, 600 (J) 

1,200(1)

1,000

1,000 

1.000 

1,000

1,300 

1,500

1)

8

D

J) 

J)

The arsenic determinations agree generally within a factor of 1.7 

except for 2 determinations of sample 1 which showed respectively 

20 and 200 ppm arsenic in contrast to other determinations of 40-60 

ppm. Except for these 2 determinations the results are limited to 

2 adjoining log classes as used in figure 37.

Zinc determinations appear to be the most precise. The maximum 

deviation is two times or 100 percent. Zinc determinations of sample 

2 are in even closer agreement.
GEOCEGEMICAL PROSPECTING STUDIES, EUREKA: DISTRICT, NEV. 405

In general, the variation of analytical determinations inherent in 

the analytical technique is limited to two log classes as used on 

figures 35, 36, and 37.

METHOD OP ANALYSIS OF ANALYTICAL DATA

The frequency distributions of lead, zinc, and arsenic are shown in 

the histograms of figures 35, 36, and 37, respectively. The class 

intervals of the histograms are logarithmic, the class limits forming 

geometric series generated by factors of 1.5 (Zn and As) and 2 (Pb). 

The class intervals of the zinc and arsenic histograms are less than 

that of lead because the total ranges of the concentrations of these 

 elements in the samples are less than the lead range.

Figures 35, 36, and 37 also show, respectively, the map distribution 

patterns of lead, zinc, and arsenic in soils of the part of the Bullwhacker mine area that was sampled. The analytical results are 

plotted as symbols which identify the class interval of the histogram in 

which the concentration of the element in the sample occurs. Use of 

symbols rather than specific concentrations permits an easier visual 

examination of the distribution and variation of the data. The ranges 

of concentration specified by each map symbol are different for the 

three elements.

The areal variations or distribution patterns are also described by 

geometric isopleths.1 The locations of the isopleths and the isopleth 

intervals were selected to show the more important features of the 

distribution patterns as exhibited by the map symbols.

RESULTS OF INVESTIGATION

Examination of figures 35, 36, and 37 indicates metal "highs" in the 

soils in the vicinity of the Bullwhacker shaft where lead-silver ore 

was mined just below the surface. It is conceivable that some part 

of each of these "highs" is the result of surface contamination from 

"ore dust" distributed during mining operations, but no evidence for 

this was noted in the field or in the samples. Calculation of the 

amount of lead in the upper 6 inches of soil within a 300-foot radius 

of the Bullwhacker shaft, using 0.025 percent as the average lead 

content indicates that it is comparable to the amount of lead in 

about 10 tons of 5 percent lead ore. Though some ore was undoubtedly distributed in the soils during mining operations, it appears 

reasonable to assume that it was far less than this amount and that 

the lead "high" in the soils around the shaft is due primarily to dispersion of lead into the wallrocks during ore formation and later 

concentration in the soils.

' Isopleth here means a line drawn through points of equal metal content.
The background concentration of lead in the soils which were 

sampled, regardless of type of parent material, appears to vary mostly 

between 15 and 120 ppm. It is important to note, however, that the 

term "background" cannot be interpreted here in the restricted sense 

that the samples are unaffected by mineralization (Lovering and 

others, 1956, p. 660). Most of them were taken too close to the 

known ore in the Bullwhacker shaft and other ore in the area to make 

this assumption safe. However, soils in the vicinity of the Bullwhacker shaft show a sharp rise in lead content over soils south of the 

shaft. The lead content of 1 sample collected 200 feet southwest of 

the shaft is more than 0.5 percent.

Two soil samples taken 700 feet east of the T. L. shaft contain lead 

in the range from 120 to 240 ppm. Lead concentrations in this range 

would not appear anomalous on the basis of the frequency distribution of all the lead analyses, but here they occur in adjacent samples 

taken near a shallow prospect pit in a weakly mineralized fault zone 

and are probably significant. In contrast, one lone value in this 

range southeast of the T. L. shaft is not considered significant.

The local background concentration of zinc in soils of the area 

ranges from 30 to 170 ppm. Soils taken from around the Bullwhacker shaft range up to 0.08 percent zinc. The two samples which 

were taken east of the T. L. shaft and which are regarded as anomalous in lead do not contain unusual concentrations of zinc.

Arsenic, in general, ranges from 15 to 50 ppm in samples taken more 

than several hundred feet from the Bullwhacker shaft. Samples 

taken nearer the shaft are as high as 150 ppm arsenic. The samples 

which were taken east of the T. L. shaft and which contain high concentrations of lead do not contain unusually high concentrations of 

arsenic.

The lead, zinc, and arsenic "highs" in the distribution patterns of 

these elements in soils near the Bullwhacker shaft appear clearly to 

be reflections of the ore and mineralized rock in the Bullwhacker 

mine. The greater intensity and broader extent of the lead "high" 

is in accord with the greater abundance of lead in the ore, but it also 

seems likely that during the processes of supergene alteration and 

oxidation of the country rock and during soil formation, lead was 

enriched in the soil by residual concentration while zinc, at least, was 

removed. In the Tintic district, Utah, Lovering (part I of Morris 

and Lovering, 1952, p. 697) has found that zinc traveled more than 

150 feet during supergene alteration of the ore, while lead is practically immobile during supergene alteration. According to Lovering 

these relative mobilities agree with the relative solubilities of lead 

and zinc sulfate as given by Britton (1942). It has been suggested
GEOCHEMI'CAL PROSPECTING STUDIES, EUREKA DISTRICT, KIEV. 407

by Goldschmidt (1954, p. 471) that arsenic is precipitated in soils by 

ferric iron hydroxide and that the arsenic is present in many soils as 

insoluble ferric arsenate.

From the relationships discussed above, notably the immobility of 

lead during supergene processes, it appears that dispersion of lead, 

zinc, and arsenic outward from the site of ore deposition took place 

during the emplacement of the ore, so that primary dispersion patterns of these elements are present in the country rock. The extent 

to which the primary pattern might differ from that found in the 

essentially residual soils could only be determined by sampling the 

unweathered bedrock beneath the thin soil cover. Regardless, lead, 

zinc, and arsenic are present in the soils in detectable amounts and 

exhibit secondary dispersion patterns or residual soil anomalies 

(Hawkes, 1954, p. 55).

In the writers' opinion the ore body at the Bullwhacker mine could 

have been discovered by the geochemical prospecting method used in 

this investigation. The metal "highs" near the Bullwhacker shaft 

are distinct and well pronounced for all three metals examined. On 

the other hand, the presence of the deeper ore in the T. L. shaft 

(800-1,000 feet below the surface) and the drill holes (800-1,100 feet 

below the surface) in the central part of the sampled area is not 

reflected in the distribution of the elements in the soils and could not 

have been detected.

A lead "high" in the soil south of a prospect pit in the southeastern 

part of the sampled area may be an indication of ore, although the 

weakly mineralized rock discovered in the pit was not encouraging. 

Additional geochemical prospecting along the fault crossing the 

prospect pit may indicate more pronounced metal anomalies related 

to the presence of ore.

REFERENCES CITED

Almond, Hy, 1953, A field method for the determination of traces of arsenic in

soils, in Additional field methods used in geochemical prospecting by the

U. S. Geological Survey: U. S. Geol. Survey open-file report, p. 8-12. 

Britton, H. T. S., 1942, Hydrogen ions: London, Chapman and Hall, Ltd., v. 2,

p. 79. . Curtis, J. S., 1884, Silver-lead deposits of Eureka, Nevada: U. S. Geol. Survey

Mon. 7, 200 p. 

Goldschmidt, V. M. (edited by Alex Muir), 1954, Geochemistry: Oxford,

Clarendon Press, 730 p. 

Hawkes, H. E., 1954, Geochemical prospecting investigations in the Nyeba

lead-zinc district, Nigeria: U. S. Geol. Survey Bull. 1000-B, p. 51-103. 

Lakin, H. W., Almond, Hy, and Ward, F. N., 1952, Compilation of field methods

used in geochemical prospecting by the U. S. Geological Survey: U. S.

Geol. Survey Circ. 161, 34 p.
Levering, T. S., Lakin, H. W., Ward, F. N., and Canney, F. C., 1956, The use of 

geochemical techniques and methods in prospecting for uranium, in Page 

L. R., Stocking, H. E., and Smith, H. B., Contributions to the Geology < 

Uranium and Thorium by the United States Geological Survey and Aton%u 

Energy Commission for the United Nations International Conference o 

Peaceful Uses of Atomic Energy, Geneva, Switzerland, 1955: U. S. Geo 

Survey Prof. Paper 300, p. 659-666.

Morris, H. T., and Levering, T. S., 1952, Supergene and hydrothermal dispersion 

of heavy metals in wall rocks near ore bodies, Tintic district, Utah: Ecor 

Geology, v. 47, p. 685-716.

Nolan, T. B., Merriam, C. W., and Williams, J. S., 1956, The stratigraphic sectio 

in the vicinity of Eureka, Nevada: U. S. Geol. Survey Prof. Paper 276, 77 p,"

Sandell, E. B., 1950, Colorimetric determinations of traces of metals: New York, 

Interscience Publishers, Inc., 673 p.