GEOLOGICAL SURVEY CIRCULAR 680 

Gold Anomaly in Soil of the 

West End Creek Area, 

Yellow Pine District, 

Valley County, Idaho 
: ,;.·' 
Gold Anomaly in Soil of the 

West End Creek Area, 

Yellow Pine District, 

Valley County, Idaho 

By B. F. leonard 

GEOLOGICAL SURVEY CIRCULAR 680 

Washington 19 73 
United States Department of the Interior 

ROGERS C. B. MORTON, Secretary 

Geological Survey 

V. E. McKelvey, Director 

Free on application to the U.S. Geological Survey, Washington, D.C. 20244 
CONTENTS 

PaRe 

Abstract ---------------------------------------------------------------- 1 

Introduction ------------------------------------------------------------- 1 

Sampling --------------------------------------------------------------- 1 

Geology ----------------------------------------------------------------- 3 

Description of anomalies -------------------------------------------------- 4 

Silver-gold ratios -------------------------------------------------------- 4 

Mineralogy of selected samples -------------------------------------------- 5 

Summary and interpretation ---------------------------------------------- 6 

Acknowledgments -------------------------------------------------------- 7 

References -------------------------------------------------------------- 7 

ILLUSTRATIONS 

Page_ 

FIGURE 1. Geologic map of the West End Creek area ---------------------- 2 

2-8. Maps showing metal anomalies in soil, West End Creek area: 

2. Gold -------------------------------------------------- 10 

3. Silver ------------------------------------------------- 11 

4. Mercury ---------------------------------------------- 12 

5. Antimony --------------------------------------------- 13 

6. Arsenic ----------------------------------------------- 14 

7. Tungsten ---------------------------------------------- 15 

8. Silver-gold ratios -------------------------------------- 16 

TABLE 

Page 

TABLE 1. Distribution of gold, silver, and some associated elements in 128 soil 

samples, West End Creek area ------------------------------ 3 

III 

Gold Anomaly in Soil of the West End Creek Area, 

Yellow Pine District, Valley County, Idaho 

By B. F. leonard 

ABSTRACT 

A gold anomaly recently found by soil sampling 

near the Yell ow Pine mine is accompanied by a silver 

anomaly and by conspicuous though minor mercury, 

antimony, arsenic, and tungsten anomalies. The anomalies are not completely delimited by the sampling, 

but preliminary results indicate that a gold anomaly 

extends 600 feet along one fault and 500 feet along 

a fault that intersects it. The gold content of 128 

soil samples ranges from less than 0.05 ppm (part per 

million) to 8.0 ppm; the median value is 0.70 ppm. 

Within the area in which gold in the soil samples is 

equal to or greater than 1 ppm, 23 samples have as the 

mean 2.91 ppm, equivalent to 0.085 troy ounce of gold 

per ton. The gold anomaly in soil helps define an attractive exploration target for low-grade gold ore in 

this area, which overlaps that of the West End Creek 

gold prospects described by J. R. Cooper in 1951 in 

U.S. Geological Survey Bulletin 969-F (p. 151-197). 

INTRODUCTION 

A gold anomaly in the West End Creek area, 

Yellow Pine district, Valley County, Idaho, was 

found by soil sampling carried out by the U.S. 

Geological Survey in 1972. The gold anomaly 

(fig. 2) is accompanied by a silver anomaly 

(fig. 3) and by conspicuous though relatively 

minor mercury, antimony, arsenic, and tungsten 

anomalies (figs. 4-7). The anomalies are not 

completely delimited by the sampling, but the 

preliminary results clearly indicate that a gold 

anomaly extends 600 feet along the fault zone 

paralleling West End Creek and 500 feet along 

the West End fault itself. The gold anomaly 

helps define an attractive exploration target 

for low-grade gold ore in this area, which 

overlaps that of the West End Creek gold 

prospects. 

The West End Creek prospects, 0.8 mile 

1 

northeast of the inactive Yellow Pine ant.imonygold-tungsten mine, were discovered by the 

Bradley Mining Co. in 1943 and descr~ bed by 

Cooper (1951, p. 189-190; prospects near 

32,000 N., 24,700 E., pl. 38). Cooper concluded 

that the prospects "may contain a substantial 

tonnage of ore averaging a little less t:'lan 0.1 

ounce of gold per ton." 

Two holes were diamond-drilled at tr~ prospects about 1946. The site of DDH WEC-1 

(fig. 1) is marked by the remains of tr~ drilling platform. The site of DDH WEC-2 and the 

orientation of both holes are inferred from an 

oral description given me by Mr. Ernest Oberbillig, mining engineer. 

Mining claims in the area of tb e gold 

anomaly were reportedly held by ElP~tronic 

Metals, Inc., Boise, Idaho in 1972. In 1f71 and 

1972, bulldozing and sampling of the Elf'~tronic 

Metals claims were carried out under the supervision of Mr. Oberbillig. 

SAMPLING 

Samples taken by Leonard at sites east and 

southwest of DDH WEC-1 (fig. 1) in July 

1972 assayed 3.0 and 7.0 ppm (parts IJ er million) Au, respectively, and :=1.5 and 3 ppm Ag. 1 

The assays confirmed the occurrence of gold 

in the area. To estimate the extent of gold 

mineralization, 128 samples of soil were collected later in July by John Schloder~r and 

volunteer William C. Leonard of the Survey 

field party. Results of the sampling are shown 

1 Analyses by U.S. Geological Survey; Au determined by fire assay 

p~us atomic absorption method by W. D. Goss, A. W. Ha.ubert, and 

J. A. Thomas; Ag determined by semiquantitative spectrographic 

analysis by R. G. Havens. 
32,000N 

EXPLANATION 

Precambrian Hoodoo Quartzite 

Contact, approximately located 

Fault, approximately located 

X 

Prospect 

Preliminary sample site 

DOH 

WEC-Ie ): 

Diamond-drill hole 

Location and direction approximate 

24,500E 

32,000N -i-

/ 

/ 

0 200 

CONTOUR INTERVAL 80 FEET 

\ 

qt 

Geology and topography 

frotn Cooper (1951, pl. 38) 

400 FEET 

FIGURE !.-Geologic map of the West End Creek area. 

2 
in figures 2-7 and in table 1. The soil samples 

were taken at depths of 4 to 6 inches, where 

possible at intervals of 25 feet on traverses 100 

feet apart. The samples represent colluvium 

from which organic debris and larger rock 

fragments were rejected. Most of the sample 

material would pass through the loosely held 

fingers of the sampler's hand. The whole of 

each sample was crushed to minus 4-mesh, 

split, finely ground, and analyzed. The bulk 

sample, not merely the fines, was chosen for 

analysis because it represents what might be 

mined at shallow depth from this deposit. 

Slopes in the sampled area are generally 

steep (fig. 1) ; the vegetation is varied. The 

slope north of West End Creek is bare, supports 

small grasses, or has widely spaced conifers. 

The rest of the area is covered with dense 

brush and conifers, and the forest floor is littered with mull. Banister's (1970, fig. 2) geochemical sampling of mull in the West End 

Creek area ended approximately where our 

sampling of soils began. 

GEOLOGY 

The geology of the West End Creek area 

is complex. Regional geologic mapping shows 

that the area is a jumble of fault blocks of 

metamorphic rock related to the inner ringfracture system of a large Tertiary cauldron 

whose central feature is the Thunder Mountain caldera of Challis Volcanics. (For a brief 

description of the cauldron and its ore deposits, see U.S. Geological Survey, 1971, p. A36.) 

Metamorphic rocks of the West End Creek 

area are dolomite, limestone, mica schist, and 

quartzite (Cooper, 1951, pl. 38; this report, 

fig. 1). The metamorphic rocks are interpreted 

here as Precambrian; the carbonate rocks are 

correlated with the Yellowj acket For1nation, 

the quartzite with the stratigraphically higher 

Hoodoo Quartzite, and the mica schist either 

with a part of the Yellowjacket beneE.th the 

carbonate rocks or with the lower part of the 

Hoodoo. A metavolcanic unit (Leonard, 1962) 

that occurs elsewhere at the top of the ~·rellowj acket is missing from the West End Creek 

area. The mica schist is interpreted as a 

muscovite-rich retrograded equivalent of the 

sillimanite-biotite schist of the district. The 

metamorphic rocks of the West End Cre~k area 

form northwest-trending belts that are parts 

of isoclinal, locally recumbent folds paralleled 

by and crosscut by faults of various a~~es and 

senses of movement. In places, the metan1orphic 

rocks are cut by alaskite of the Idaho batholith suite. 

Cooper (1951, pl. 38; this report, fig. 1) 

showed three faults in the West End Creek 

area. He interpreted the apparent horizontal 

offset of metamorphic rock belts on OY)posite 

sides of the West End fault 2 as indicative of 

right-lateral movement along the fault. A similar movement sense may be inferred along the 

fault that underlies West End Creel~. here 

named the Seeing Eye fault for its so•1theast 

strike. The Seeing Eye fault is partly exposed 

as a zone of slumped gouge visible in roadcuts 

along West End Creek. This fault, and probably the neighboring faults as well, rr.~rks a 

zone of deformation, not a single, sharp break. 

The southwestward increase in apparent 

horizontal offset along the West End fault and 

the steepening of the dip of foliation in l''lmolo2 The West End fault was named many years ago. Note that 

the West End fault does not coincide with West End Creek. The 

name of the fault, though confusing, is too well estahlished to 

change. 

TABLE 1.-Dist-ribution of gold, silver, and some associated elements in 128 soil samples, West End Creek area 

[Values in parts per million, unless otherwise noted. 1 ppm Au or Ag is equivalent to 0.029 troy ounce per short ton. Analyses by U.S. Geological Survey. Au and Ag determined by atomic absorption analysis: Au by E. Welsch and J. D. Hoffman, Ag by R. ~· 

Carten and R. M. O'Leary. Hg determined by R. Turner. As, Sb, W, and Fe determined by semiquantitative spectrographic analysis 

by D. Siems and B. Crim. L, detected but below limit of determinationj 

Au ---------------

Ag --------------- Hg ---------------

As --------------- Sb ---------------

VV --------------- Fe (in percent) __ _ 

Limit of determination 

0.05 

.5 

.01 

200 

100 

50 

.05 

1 Values at and below limit of detection counted as zero. 

Range 

<0.05- 8.0 

<.5 - 17.0 

.08- 5.8 

<200 -2,000 

<100 - 300 

<50 - 150 

.7- 5 

2 Not significant; too many values below limit of detection. 

3 

Mode 

L(0.05) 

1.0 

0.10-0.19 

<200 

<100 

<50 

3 

Median Mean 1 

0.70 0.69 

4.0 1.6 

.52 .90 

200 (2) 

L(100) (2) 

<50 (2) 

3 2.6 
gous rock units north of the fault are consistent 

with a reinterpretation of the fault as a hinge 

fault of the radial fracture system of the 

Thunder Mountain caldera. In this reinterpretation, the hinge point of the West End fault 

is at its intersection with the Seeing Eye fault; 

relative motion along the West End fault 

swings the north side up, and the total angular 

displacement is about 23 o, or-if the angular 

displacement was equal in magnitude and opposite in sense-about 11 o up for the north 

block and about 11 o down for the south block. 

DESCRIPTION OF ANOMALIES 

The gold anomaly shown by soil sampling 

is mainly along West End Creek and west of 

its confluence with the gully underlain by the 

West End fault (fig. 2). A lobe of the anomaly 

extends southwestward, parallel to the West 

End fault and about 100 feet southeast of it. 

Minor gold highs are present at the southwest 

corner of the sampled area. A conspicuous gold 

high, incompletely mapped, is present at the 

southeast corner of the sampled area. This high 

is near the intersection of the Seeing Eye fault 

and a north-northeast-striking fault mapped 

by Cooper. The preliminary sampling merely 

shows a target for additional exploration; it 

does not fully define the area that may be 

favorable for the occurrence of gold. 

The silver anomaly (fig. 3) is nearly coincident with the gold anomaly in outline, but the 

highs do not all correspond with each other. 

Moreover, the southwest lobe of the silver 

anomaly passes across the trace of the West 

End fault. The relations of the distribution of 

silver and gold in the soil samples are better 

seen in figure 8, a plot of the Ag-Au ratios. 

Mercury, antimony, arsenic, and tungsten 

(figs. 4-7), as well as copper (not illustrated; 

maximum concentration 100 ppm), give minor 

anomalies similar in outline to those of gold 

and silver. Accordingly, any of the five minor 

elements might have served as a pathfinder for 

gold and silver at this site, but none of them 

was essential. Statistically, none of the five 

minor metals correlates well with gold or silver; spatially, all five indicate the gold and 

silver target. 

Tin, an element rarely detected in spectrographic analyses of rocks of the region, gives 

a weak anomaly near the southeast corner of 

4 

the area sampled. The peak value is only 15 

ppm. 

Iron gives a minor anomaly similar in orientation to the gold anomaly but difrering in details of shape. Broad iron highs generally coincide with the mica schist belt. A narrow, weak 

high coincides with the trace of tl'~ West End 

fault. Iron lows coincide with arer~ of quartzite and carbonate rocks. These r~lations are 

only of local significance, for in so'lle places in 

the region, carbonate rocks characteristically 

break down to terra rossa, a red, iron-rich soil. 

The iron anomaly in the West End Creek area 

is too trivial to show as a text figure, but the 

distribution of iron is summarized in table 1. 

The element is of interest because iron oxide 

minerals are conspicuous in mucr of the soil 

in the West End Creek area, and gold is associated with them. Nevertheless, it is the mineralogy of the soils, rather than tl'C!ir total Fe 

content, that is significant. 

The following additional ele1nents were 

sought by semiquantitative sp~ctrographic 

analysis: B, Ba, Be, Bi, Ca, Cd, Co, Cr, La, 

Mg, Mn, Mo, Nb, Ni, Pb, Sc, Sr, Ti, V, Y, 

Zn, Zr. Among these, Mo is present in slightly 

anomalous concentrations (5-7 ppm) in three 

samples. The other elements detected spectrographically behave as common rock-forming 

elements and show no anomalour concentrations. 

SILVER-GOLD RATIOS 

Gold and silver are the only ele1nents of the 

table 1 suite that show a moderately good correlation by statistical test, in spite of the wide 

range of Ag-Au ratios. The ratios range from 

0.5 to 40.0 (mostly from 1 to 7), the mode is 

2 (by class intervals 0-0.9, 1.0-1.9, ... ) , the 

median 3.0, and the mean 4.8, "based on 73 

sample pairs for which the values of both Ag 

and Au are above the limit of determination. 

The ratio of 0.5 is given by a single, erratic, 

gold-rich sample containing 4 pprn Ag and 8 

ppm Au. If this erratic sample is disregarded, 

the coefficient of determination, 'f2 , is 0. 70. The 

quality of the correlation is only fair; 1.00 

would represent a perfect correlation. 

A map of the contoured Ag-Au ratios (fig. 

8) shows that the attempt to corr~late all the 

determinable ratios is destined for limited success because the ratios are distinctly zoned. 
Low ratios ( <3.0) form a trough flanked by 

higher ratios. The axis of the trough coincides 

in most places with the higher gold values. By 

inverting the ratio, the relation can be stated 

another way: high Au-Ag ratios generally accompany the higher Au values; or, the higher 

the gold assay, the greater the apparent fineness of the gold. The relation is a common one 

in many gold deposits. 

Once the zoning is recognized, the Ag-Au 

ratios of the trough and flanking areas can be 

compared separately. For the trough, Ag:Au 

<3.0 for 27 samples, the coefficient of determination, r 2 , corrected for the small number of 

samples, is 0.85. The line of regression is defined by the equation 

Yc=l.975X-0.061, 

and the scatter or standard error of estimate, 

U,sy' is 1.33 ppm. This means that, within about 

1 ppm, the calculated value of Ag (taken as 

the dependent variable) is roughly twice the 

value of Au. For the flanking areas that are 

well defined, Ag:Au >3.0 for 17 samples, the 

coefficient of determination, r 2 , corrected for 

the small number of samples, is 0.89. The line 

of regression is defined by the equation 

Y c=5.266X +0.466, 

and the standard error of estimate, u8Y' is 1.07 

ppm. That is, within about 1 ppm, the calculated 

value of Ag is roughly five times the Au value 

plus 0.5 ppm. Thus the correlations are good 

when the zonal distribution of the metals is 

taken into account. 

MINERALOGY OF SELECTED SAMPLES 

Five samples selected because of their high 

gold, high silver, and median gold content 

were cleaned ultrasonically and separated in 

methylene iodide by James R. Jacobs. The sized 

heavy and light fractions were examined microscopically. 

More than 70-80 percent of each sample 

consists of the common rock-forming minerals 

of the mica schist and quartzite that underlie 

most of the area sampled. 

No particles of native metal, unoxidized sulfides, or unoxidized sulfosalts were detectable 

in the plus 325-mesh fractions or in the washed 

minus 325-mesh fines. Goethite and hematite 

are common oxidation products, and clays are 

moderately abundant. Some of the goethite is 

pseudomorphous after minute pyritohedra of 

5 

pyrite; the rest is granular, fibrous, or formless. Hematite is present as plates of rpecularite, as black grains, and as earthy rec. grains, 

in part intergrown with goethite. A trace of 

jarosite ( ?) was detected in one X-ray powder 

photograph of goethite. 

The clays are colorless to dark brown. X-ray 

powder diffractograms show them to be a mixed 

assemblage. Illite is present in all five samples 

and dominant in most. In most samples, illite 

is accompanied by kaolinite, montmorillonite, 

or both minerals. Chlorite and an unirtentified 

clay-size mineral are present in seve:ral samples. No goethite, lepidocrocite, or jarc~ite was 

detectable in the clay fraction. 

Samples of the heavy fractions and of the 

untreated soil samples were mounted in coldsetting plastic and polished by various methods. Owing to the porosity and fragility of the 

hematite-goethite intergrowths and, ir the untreated samples, to the abundance of clay, the 

samples were difficult to polish. After repeated 

trials, work was concentrated on the minus 60, 

plus 100-mesh heavy fraction of a sample for 

which analysis of the original unseparated soil 

sample gave 6.0 ppm Au and 14.0 ppm Ag. This 

atypical sample was chosen because of the 

reasonable likelihood of identifying gold particles in it. 

The polished section of the heavy fraction of 

this atypical sample showed 50 grainf of iron 

oxides, most of them cellular aggre,?:ates of 

minute hematite plates intergrown with very 

fine grained goethite. A few of the ag~regates 

resemble pseudomorphs after pyrite. Scanned 

at X 320 with a dry objective, 14 grains (28 

percent) showed minute pips of a brigl't metallic mineral within the iron oxide aggregates, 

generally as a single recognizable pip within 

each aggregate grain. The diameter of measurable pips is < 1 to 2.2 microns. The pips, examined at X 480 with an oil-immersk'l objective, are equant to shredlike, bright, very pale 

yellow to almost white, well polished, and softer 

than the hematite within which most of them 

are enclosed. In addition to the single pips 

visible at X 320, several to a dozen bright 

particles < 1 micron in diameter are visible 

in oil in each grain of the iron oxide aggregate. 

The minute size of all the pips mak€.s it impossible to measure their physical pro'1erties. 

Electron-microprobe scanning of the pips and 
their oxide host grains also fails to identify 

the pips but does indicate the site of some gold 

and silver in the sample. George A. Desborough, 

the probe analyst, reports that the pips do not 

contain measurable Au, Ag, Hg, As, S, Sb, Se, 

or Te. In contrast, pits as much as 5 microns 

long within the oxide host show a high concentration of Ag, subordinate Au and S, and no 

detectable Hg, As, Sb, Se, or Te. The proportions of Ag and S suggest that the pits contain 

acanthite, but failure of these areas to polish 

leaves the identification of acanthite in doubt. 

For eight areas, the ratio of Ag to Au within 

the pits ranges from 1.2 to 13.5 and averages 

6.2. The high mean Ag-Au ratio in the pits 

contrasts strongly with the ratio of 2.3 found 

by assay of the original soil sample. Probe 

scans of a polished mount of the soil sample 

itself and of a typical soil sample assaying 0. 70 

ppm Au and 2.0 ppm Ag showed a slight concentration of Ag at the contacts of micron-size 

particles of iron sulfides identified optically and 

by probe as pyrite and pyrrhotite. The iron sulfides in the unseparatzd soil samples are inclusions within rock-forming silicates and are 

most likely accessory minerals of the unmineralized country rock. 

In summary, a careful mineralogical reconnaissance of representative samples shows that 

some of the Ag-perhaps much of it--is present as a sulfide (acanthite ?) ; that the silver 

sulfide areas contain some Au, whose form is 

unknown; and that Hg is neither concentrated 

in the silver sulfide areas nor locatable elsewhere by microprobe study of these samples. 

Silver sulfide areas definable by microprobe are 

confined to the hematite-goethite aggregates, 

within which they occur as unpolished areas 

only a few microns long. The Ag-Au ratio is 

considerably higher in the silver sulfide areas 

than in the corresponding bulk sample ; therefore, some Au of unspecifiable site is also present. Particles of native gold and silver have not 

been identified. 

The small particle size of the precious-metalbearing areas and the absence of identifiable 

particles of native gold or electrum are consistent with the statement of Cooper (1951, p. 

190) that low-grade ore from the West End 

Creek prospects cyanides readily, the implication being that the ore treated was not free 

milling. 

6 

SUMMARY AND INTERPRETATION 

A major gold anomaly nearly coiiJcident with 

a major silver anomaly is present in soils of 

the West End Creek area. The gold anomaly, 

though incompletely mapped, is r. favorable 

target for further exploration. Tll e principal 

area in which gold values exceed 1 ppm measures about 100 by 450 feet. Several smaller 

areas having Au > 1 ppm are pr~~sent south 

and southwest of the main part of the anomaly. 

The limits of the isolated highs have not been 

established. Gold in soils is not lin1ited to the 

immediate neighborhood of the West End fault, 

along which most of the earlier prospecting 

was concentrated. Instead, the principal gold 

anomaly mapped so far is along West End 

Creek itself. 

Within the area in which gold values are 

equal to or greater than 1 ppm, 23 samples 

have as the mean 2.91 ppm Au, 6.00 ppm Ag, 

and Ag:Au=2.06. The mean gold content of 

these soil samples, equivalent to 0.085 troy 

ounce per ton, is remarkably close to "a little 

less than 0.1 ounce of gold per ton/' the average reported by Cooper (1951, p. 190) for a 

substantial tonnage of ore at the West End 

Creek prospects. 

The distribution of gold, silver, and minor 

metals in the soils is most reasorably interpreted as related to the West End and Seeing 

Eye faults and to a third fault that strikes 

north-northeast. The widespread occurrence of 

gold and silver in the soils suggests a diffuse 

sort of mineralization, accompani£ld by little 

gangue except clay minerals and iron oxides. 

The field aspect of the iron oxides suggests 

weathering, but these oxides and their hydrates 

might equally well have been formed by a lowtemperature hypogene process attendant on 

deposition of the gold. The zoning of gold and 

silver values might be either hypogene or supergene; in other areas, both pro~esses have 

led alike to the development of gold-rich zones 

in which the gold is enriched at the expense of 

silver. The gold-rich zones here are not confined to gullies and creek bottoms, where surface water is seasonally plentiful; and upslope 

areas do not characteristically shov-' silver depletion, as one might expect if leaching of the 

more soluble element, silver, had been effected 

by ground water. Rather, the zonal distribution 

of gold and silver in the soils seems more rea-
sonably interpreted as a primary feature of the 

underlying deposit. Nothing in the distributional pattern is suggestive of eluvial or ancient 

placer concentration or of a lithogene source 

of the gold and silver. 

No other investigations of gold and silver 

anomalies in soils of the district are available 

to guide an economic interpretation of the 

results of this sampling. Nevertheless, the preliminary results reported here seem adequate 

to encourage further exploration of the area 

for low-grade gold ore. 

ACKNOWLEDGMENTS 

I am indebted to Mr. T. C. Jarrett of the 

T. C. J arret Co. for suggesting a method of 

embedding that made it possible to polish the 

fragile iron oxide aggregates, to Mr. Ernest 

Oberbillig, Electronic Metals, Inc., for information on drill sites, to my associate George A. 

Desborough for microprobe analyses of selected 

7 

samples, to James R. Jacobs for the sep".ration 

of samples, to Glen Izett and C. S. ,.Tenable 

Barclay of the Geological Survey for access to 

special X-ray equipment, and to the chemists 

of the Geological Survey for providing the 

abundant analytical data on which thi~· report 

is based. 

REFERENCES 

Banister, D'A. P., 1970, Geochemical investigations for 

gold, antimony, and silver at S.tibnite, ldE.ho: U.S. 

Bur. Mines Rep-t. Inv. 7417, 7 p. 

Cooper, J. R., 1951, Geology of the tungsten, E.ntimony, 

and gold deposits near Stibnite, Idaho: r.S. Geol. 

Survey Bull. 969-F, p. 151-197. 

Leonard, B. F., 1962, Old metavolcanic rocks of the Big 

Creek area, central Idaho, in Short P"·l)ers in 

geology, hydrology, and topography: U.S. Geol. 

Survey Prof. Paper 450-B, p. B11-B15. 

U.S. Geological Survey, 1971, Geological Survey research 1971: U.S. Geol. Survey Prof. Paper 750-

A, 418 p. 

FIGURES 2-8 
32,000N 

'\ 

\ 0 

o.~b ."') 

-~ .P.30 

EX PLANATION 

.t.o 

Sample site 

Au, in ppm 

0.10. 

0.25. 

200 FEET 

I 

FIGURE 2.-Gold anomaly in soil, West End Creek area. Contours 0.1-0.5-1-2-3-5 ppm. N, not detected; L, detected but below limit of determination (0.05 ppm). 

10 
EXPLANATION 

.2.0 

Sample site 

Ag, in ppm 

\ N. 

N. ~ 

\ 

\ 

\ 

\ 

\ 

i '\ \ 

I \ 

\ \ 

' 0 N L.\ \ . \ \ 

\._ \, ''\ 

FIGURE 3.-Silver anomaly in soil, West End Creek area. Contours 1-2-3-5-10-15 ppm. N, not detected; L, detected but below limit of determination (0.5 ppm). 

11 
EXPLANATION 

.1.7 

Sample s't 

Hg, in p~~ 

/

0.39 . . 

()'? 019) \ o.\o. 

FIGURE 4 .-M ercury anomaly in soil, . West End 

12 

Creek area C . ontours 0.5-1-2-3-4-5 ppm. 
32,000N 

EXPLANATION 

.2 

Sample site 

Sb, in 102 ppm 

N. 

N. 

24,500E 

\\ \ 

L. 

N. N. 

N. 

N N . N. 

I 

I 

I 

N.;N. 

N. 

N . I 

N N. 

N. . 

/ 

/ / 

FIGURE 5.-Antimony anomaly in soil, West End Creek area. Contours L-1-2-3Xl02 ppm. N, not detected; L, detected but below limit of determination (100 ppm). 

13 
32,000N \ 

\ 

\ 

EXPLANATION 

.3 

Sample site 

As, in 102 ppm 

\ 

\ 

\ 

I N. 1· 

I 

I 

N. 

N. 

N. N. 

N. /." • 

/ / / N i I 0/ ( 

• / I 

J' \ \ \ 

\ 2\ N. N. \ \ 

\ \ \ 

I 

FIGURE 6.-Arsenic anomaly in soil, West End Creek area. Contours 2-3-5-10-20Xl02 ppm. N, n'lt detected at 

200 ppm. 

14 
\ 

EX PLANATION 

.50 

Sample site 

W, in ppm 

24,500E 

"· \"• "· 

\ 

\ 

N. \ 

\ 

\ N. 

'\.,, \. N. 

' N. \ \ N. \ 

\ 

\ N. \ 

\ N. \ 

\ N. 

N. \ N. \ 

\ .. 

N \ 

\ '\\ 

\ 

L. 

FIGURE 7.-Tungsten anomaly in soil, West End Creek area. Contours L-50-100 ppm. N, not detected; L,. detected 

but below limit of determination (50 ppm). 

15 
'32,000N 

EXPLANATION 

Sample site 

Ag:Au ratio 

24,500E 

I . I· • I ).. 

FIGURE 8.-Silver-gold ratios in soil, West End Creek area. Contours 3-5-10-20-30-40. 

16