GEOLOGICAL SURVEY CIRCULAR 265 

RADIOACTIVITY INVESTIGATIONS IN THE 

SERPENTINE-KOUGAROK AREA 

SEWARD PENINSULA 

ABASKA, 1946 

u .•. 

PUElLit.l I CJ It,; 

.SAN .ERANC:J5C:LJ, C:AI...Jft:JRNIA 

UNITED STATES DEPARTMENT OF THE INTERIOR 

Douglas McKay, Secretary 

GEOLOGICAL SURVEY 

W. E. Wrather, Director 

GEOLOGICAL SURVEY CIRCULAR 265 

RADIOACTIVITY INVESTIGATIONS IN THE SERPENTINE-KOUGAROK AREA 

SEWARD PENINSULA, ALASKA, 1946 

By Robert M. Moxham and. Walter S. West 

This report concerns work done on 

behalf of the U. S. Atomic Energy 

Commission and is published with 

the permission of the Commission 

Washington, D. C., 1953 

Free on application to the Geological Survey, Washington 25, D. C. 

RADIOACTIVITY INVESTIGATIONS IN THE SERPENTINE-KOUGAROK AREA 

SEWARD PENINSULA, ALASKA, 1946 

By Robert M. Moxham and Walter S. West 

CONTENTS 

Page 

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

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

Geography . . . . . . • . . . . . . • . . . . . . . . . . . . . . . . . . . . . . 2 

Location and extent of area . . . . • . . . . . . . . . . . 2 

Physical conditions in the area. . . . . • . • . • . • . 2 

Settlements, accessibility, and 

sources of supply. . • . . • . . • . • . . • . • . • . . . . . 2 

Geology ..•.•..•..•.....•...•...•...••......... 2 

Undifferentiated limestone, slate, and 

schist .....•.•.••....•••.......•....... 2 

Port Clarence limestone . . . . • . . • . • • • . . • . . . 2 

Greenstone ..... , .•........•.•.•.•.•..••. 2 

Granite at Serpentine Hot Springs and 

other felsic intrusives . . . . • . . . • . • . . • . • • . 4 

Page 

Mineralization, lode prospects, and 

placer gold mining .•...••.•••. o • • • • • • • • • • • • • • 4 

Radioactive mineral investigations .... o ••• o ••• o. 6 

Field studies ...•..••.•.........•.••. o • • • • 6 

Laboratory studies . . . . . . . . . . . . . • . • . . • • . . . 6 

Distribution of radioactive material . . . . . . . . 6 

Bedrock deposits of radioactive material. . • . • . . • • . • • • . . . . • . . 7 

Radioactive material in the alluvium ..•. 7 

Radioactive minerals ....... o • • • • • • • • • • • • • 7 

Thorium-uranium content ...•.•• 0 •••• 8 

Conclusions. . . . • • • . • . . . • . . . • . . . . . . . . . . . • • . . . • . 8 

Literature cited . . . . . • . • • • • • . • . . . . . . . • • • . . . . . . . 8 

Unpublished reports . . . • • • • • • . • • • . • • . • • • . • • . . • • 8 

ILLUSTRATIONS 

Page 

Figure 1. Geologic sketch map of the Serpentine-Kougarok area, Seward Peninsula, Alaska, showing 

sample localities. . . • • • • • • • • • • • • • • • • • . • • • • • . • . . • • • • • . • . . . . . • . . . . • . . . • . . • . • . . . . . . • . . • • • • • . . • . 3 

2. Geologic sketch map of the Serpentine-Hot Springs area ...• 0 ........... 0........................ 5 

TABLES 

Page 

Table 1. Data on bedrock samples, granite area in vicinity of Serpentine Hot Springs........................ 9 

2. Data on placer 'sarr.ples .•.•..•..•..•..•....•.....•.•...•.....•.•.....•...... 0........ . . . . . . . . 9 

ABSTRACT 

Radioactive minerals in small quantities were 

found in the bedrock and alluvium within the outcrop 

area of granite at the head of Serpentine River. 

Tests of radioactivity at outcrops of the granite 

indicate that small amounts of radioactive material is 

disseminated throughout the mass. Four variants of 

the normal granite have been recognized: early and 

late differentiates, and pegmatitic and fine-grained 

facies. All variants except the early differentiates 

show radioactivity in excess of the normal granite. 

The average equivalent uranium content of 29 samples 

of the granitic variants is 0. 008 percent. The heavymineral portions of these samples average 0. 034 percent equivalent uranium. 

The radioactivity of the placer material and 

bedrock is attributable to zircon, sphene, allanite, 

hydrogoethite, and two unidentified secondary minerals. 

Neither the bedrock nor placer deposits contain sufficient radioactive materials to be of present commercial 

interest. 

1 

INTRODUCTION 

Investigations in the Serpentine-Kougarok area 

on the Seward Peninsula, Alaska, in 1946, were made 

specifically to search for lode and placer deposits of 

radioactive materials. Two factors were responsible 

for the selection of this particular area for examination: 

1) Two sarr.ples from the upper Kougarok area 

in the Alaskan placer collection were tested for radioactivity in the winter of 1944-45. One sample {labelled 

Harris Creek, a tributary of the North Fork) showed 

1. 335 percent equivalent uranium and was among the 

more highly radioactive samples from all of Alaska 

(Harder and Reed, 1945, p. 5, 14). 

2) Investigations in 1945 at Ear Mountain 

(Killeen and Ordway, 1946), 45 miles west of the 

Serpentine-Kougarok area, exposed a small radioactive 

lode deposit associated with a granitic intrusive similar 

to the granite at the head of the Serpentine River. 

Field work began June 22, 1946 and was terminated September 23, 1946. 
GEOGRAPHY 

Location and extent of area 

The Serpentine-Kougarok area (fig. 1), in the 

north-central part of the Seward Peninsula in western 

Alaska, straddles the divide along the east-west axis 

of the peninsula. 

The limits of the area have been chosen arbitrarily 

to include the headwater portions of the Serpentine, 

Kougarok, Pish, and Humboldt Rivers and the eastern 

headwater tributaries of American River. 

Nome, on the south coast of the peninsula is 

approximately 80 miles south of the center of the area. 

Physical conditions in the area 

Rolling, treeless tundra is prevalent throughout 

the area. Low ridges with locally steep and rugged 

peaks lie between the principal drainage basins. 

Kougarok Mountain, 2, 767 feet in altitude, is the highest peak in the region. Tundra extends up the flanks 

of the hills until the steepness of the slope affords 

some 9rainage. Above this level the rocks are generally bare of vegetation and usually disintegrated into 

a deep talus mantle by severe frost action. The area 

is treeless, except for a few small stunted willows in 

some creek bottoms. 

Settlements, accessibility, and sources of supply 

Nome is the principal source of supplies and the 

main base for small planes, which are the only convenient means of transportation into the SerpentineKougarok area. 

The two most frequently used landing fields in 

the Serpentine-Kougarok area are at Taylor, in the 

upper part of the Kougarok River valley at the mouth 

of Taylor Creek, and on Hot Springs Creek at the head 

of the Serpentine River. At the time the field work 

was carried out the Serpentine Hot Springs field was 

generally considered hazardous because of its short 

runways (about 1, 000 feet), rough surface, and the 

prevalence of crosswinds and downdrafts. The Taylor 

field was the more frequently used for routine service. 

Airstrips are also in use at most of the active mining 

camps, including Keenan's arid John Kanari's camps, 

4 and 6 miles, respectively, north of Taylor on the 

Kougarok River; George Bodis' camp on Dick Creek 

in the Serpentine basin, about 12 miles northwest of 

Taylor; and at the camp of the North Fork Dredging Co., 

on North Fork, 5 miles east of the KougarokRiver. 

Taylor, formerly an active placer-mining camp 

and center of population in the Serpentine-Kougarok 

area, was almost completely abandoned during World 

War II owing to the ban on gold mining. Only one man 

was working there during the summer of 1946. Taylor 

can be reached by road from Shelton in the lower 

Kougarok River valley, the terminus of a narrow gage 

railway from Nome. Freight for the Kougarok area is 

also brought in by barge from Teller to Davidson's 

landing, 25 miles south of Taylor, and then hauled by 

tractor to the various mining camps. 

Serpentine Hot Springs, about 14 miles north of 

Taylor, can be reached by either tractor or plane. 

2 

There are no permanent residents in the immediate 

vicinity. 

GEOLOGY 

Earlier reconnaissance investigations in the 

Serpentine-Kougarok area in 1900, 1901, and 1906 

were summarized by Brooks in 1908 (Collier and 

others, 1908, p. 294-328). Brief statements have been 

published on some of the lode prospects (Smith, 1908, 

p. 244; Mertie, 1918, p. 440-442; Brooks, 1922, p. 65) .. 

Comments on the placer-mining activities are made in 

a water-supply paper (Henshaw and Covert, 1908, 

p. 77-98) and in many of the Geological Survey's reports 

on the mining industry. 1 The placers of the upper 

Kougarok River are described in an unpublished report 

by Shallit (1941). 

Three· types of bedrock are recognized in the 

Serpentine-Kougarok area. These are: 

1) Two "units" of the Nome group of altered 

sedimentary rocks of Ordovician and· Silurian age. 

a) Undifferentiated limestone, slate, and 

schist. 

b) The Port Clarence limestone, probably 

mostly Silurian in age. 

2) Greenstone of Paleozoic age or younger. 

3) Granite and other felsic intrusives of Mesozoic 

or, in part, perhaps of Tertiary age. 

Quaternary unconsolidated silt, sand, and gravel 

occur as fill of variable depth in the valley bottoms. 

Undifferentiated limestone, slate, and schist 

In general, the undifferentiated limestone, slate, 

and schist of the Nome group are exposed in the valley 

basins, whereas the Port Clarence limestone forms 

the ridges between the basins. Exceptions to this 

generalization include parts of Kougarok Mountain and 

Midnight Mountain and the nearby hills, which are 

composed of schist. The schist normally consists of 

quartz and chlorite or muscovite but is locally 

graphitic. 

Port Clarence limestone 

The Port Clarence limestone is a massive, 

crystalline marble in most places. At localities near 

the limestone-schist contact the limestone shows considerable contortion. Traces of fossils have been 

retained in a few localities despite the intense metamorphism. Collections made by Collier on Harris 

Creek were considered to be Niagaran or middle 

Silurian in age (Collier and others, 1908, p. 76). 

Greenstone 

Intensely altered mafic intrusive rocks, classified as greenstone by Collier, occur on Washingto~ 

1Annual summary reports from 1905 to 1942 by A. H. Brooks and 

p. s. Smith on the mining or mineral industry of Alaska. The numbers 

of the yearly bulletins may be obtained from •publications of the 

Geological Survey•. 
ee•'re~s-·~40~·----------------------~z~o·------------------~-r.~~~~~--~--~--~--T----r~~~------------r-------r-~~~ 00' 

50' 

168° 164° 160° 

NOR rON 

~4"1t~.~~------~--------+-------~~~~---rl64° 

,p /N t1 =-==-= 10 MILES 

INDEX MAP OF SEWARD PENINSULA, ALASKA 

65° 

~~~L-~~~~L-~~~~~~~~~~~~~~~~~~~~~~~4-~---------U~~-----L--------------~~·~·-30' 

.... - u.s. .......... '""'"' to,..,.,lllc •• ,. 

wit• •o .. floetlooo 1- U.S.A.A.F. llltllt -

(1. 

:::> 

0 

a: 

(!) 

~ 0 

z 

SEDIMENTARY ROCKS 

D Silf1 sand, and grovel 

D Port Clarence limestone 

D Undifferentiated limestone 

slate, and schist 

t> ~~ :::>Z 

0 

h 

z!./ 

::!~ a:o 

;;j!§ 

rJl 

10 Miles ... ... , Olo4iflod - hllotln sza 

EXPLANATION 

IGNEOUS ROCKS 

r Road m 2 Cot trail iii Granite _and ~ther felsic !ij A 

.. ~ .. - !~ Airstrip 

@ ~ s Placer mining operation 

Greenstone ~ X 

Copper prospect 

.142 

Sample location and collection 

oomber referred to in text 

Figure 1. -Geologic sketch map of the Serpentine-Kougarok area, Seward Peninsula, Alaska, showing sample localitie: 

3 
and Henry Creeks, tributaries of the upper Kougarok 

River, and in the valley of the Kougarok south of 

Coarse Gold Creek. The greenstone on Henry Creek 

contains crystals of actinolite and garnet but lacks the 

schistose characteristic of this rock type in other 

localities. 

Granite at Serpentine Hot Springs and 

other felsic intrusives 

In the vicinity of Serpentine Hot Springs, a 

granitic stock of Mesozoic or Tertiary age is exposed 

over a roughly oval area (fig. 2). Th~ long axis of 

the oval is about 6 miles in length, extending in an 

east-west direc~ion. Serpentine Hot Springs is slightly 

west ~f the center of the granite area, the larger part 

of which is within the headwater drainage of Hot Springs 

and Humboldt Creeks, and the Pish River. Pinnacles 

formed by weathering along well-developed joint systems 

make the outcrop area rather conspicuous. 

The normal granite is a coarse, light-colored 

rock composed chiefly of quartz, orthoclase, and 

biotite. Locally it encloses rounded masses, up to a 

foot in diameter, containing a much greater proportion 

of biotite. They probably represent partly assimilated 

inclusions of an early mafic magmatic differentiate 

or border phase. 

The stock has been transected by three types of 

intrusive material or differentiates of the granite: 

1) Pegmatitic quartz-muscovite veins. 

2) Fine-grained, felsic dikes similar to the 

granite in composition. 

3) Dark-colored, tabular, dike-like masses 

similar,in composition to the earlier mafic differentiates. 

Probably all of the three types listed are related 

in time of emplacement and magmatic source and 

represent phases in consolidation of the magma. 

The variants are generally very irregular and difficult 

to trace for any distance. The contacts may be either 

sharp or gradational. Few of the dikes exceed several 

inches in thickness, and the thicker portions are generally lens-shaped. Vugs are present in some of the 

pegmatites and are lined with quartz, mica, and 

tourmaline crystals. 

Although these granitic variants are present in 

many parts of the area, the greatest number occur in 

the pinnacles on the flanks and summit of the low hill 

on the northeast side of the south fork of Hot Springs 

Creek. Vugs and irregular banding are well developed 

in a pegmatite that transects a pinnacle near the summit 

of the hill.at the local~ty where samples 86-88 were 

collected (fig. 2). The pegmatite consists of a central 

zone up to 4 inches in width composed of quartz, muscovite, and tourmaline, and irregular zones on both 

sides composed of layers of fine-grained, felsic 

material a few inches in width. A biotite-rich zone, 

about 5 feet in length and several inches wide, occurs 

in the normal granite along one margin of the vein. 

In a second pinnacle, 30 feet distant, the probable 

continuation of the same dike contains a vug 2 feet in 

diameter lined with quartz crystals up to 2 inches in 

length and books of mica. 

4 

Rhyolitic intrusives of small size were found by 

earlier surveys on the summit and southwest slopes 

of Kougarok Mountains, 18 miles west of Serpentine 

Hot Springs. 

MINERALIZATION, LODE PROSPECTS, 

AND PLACER GOLD MINING 

A small amount of placer cassiterite occurs in 

the gravels of Humboldt Creek and has been reported 

from Mascot Gulch, a headwater tributary of the 

Kougarok, and from Dick Creek, a tributary of the 

Serpentine River. An unverified report suggests that 

cas~iterite may occur also in Budd and Windy Creeks, 

tributaries to American River. Scheelite, said to 

hav~ been obtained from Homestake Creek, a tributary 

entering the Kougarok River from the west at Taylor, 

was shown to the writers by a prospector. Cinnabar 

has been recognized in some gravels of the lower 

Kougarok River valley, and a small amount was seen 

in concentrates panned from a shallow gully in the 

south side of the eastern fork of Hot Springs Creek. 

Several copper prospects have been staked in 

the vicinity of Kougarok Mountain, but evidence of 

development work was seen only at the Ward property 

between Bismark and Star Creeks, 2 miles north of 

the northern end of Kougarok Mountain. Several 

trenches have been dug at the Ward prospect, and an 

adit, now caved a short distance from the portal, 

reveals several veins of malachite and azurite about 

2 inches thick near a limestone-schist contact. 

Gold-quartz lodes are reported to have been 

exposed by placer mining at the headwaters of the 

Kougarok River, but none have been worked 

commercially. 

Placer-gold deposits have been found in many 

parts of the drainage basins of the area. The placers 

have been mined on Dick Creek, Humboldt Creek, 

some tributaries of the American River, and in the 

Kougarok basin. The major part of the production 

has been from the Kougarok and its tributaries. 

The Kougarok district ranked second in gold 

production on the Seward Peninsula before World 

War II, surpassed only by the Nome district (Smith, 

1941, p. 59). Dredges accounted for the largest output, but many smaller hydraulic workings also contributed to it. Gold mining was at a standstill during 

the war owing to the ban on all but very small 

operations. 

Mining in the upper Kougarok River valley has 

centered around Taylor, where a number of bulldozerhydraulic operations were active during the prewar 

period. Most of the other workings were within a 

short distance of Taylor on the main stream, but many 

of the upper tributaries have been worked sporadically 

in the past, some nearly to their sources. In 1946, 

the operations in the upper Kougarok River valley, 

above the mouth of North Fork, were as follows: 

John Kanari, 6 miles north of Taylor; the Kougarok 

Consolidated PlacersJinc., 4 miles north of Taylor, 

where dredging had not yet been resumed, but drilling 

was in progress; Jim Carroll at Taylor; Sam Godfrey 

at the mouth of Henry Creek, 2 miles south of Taylor; 
CJ'1 

164"50' ~· 40' 

=1 \~ ~ ~soot """"' .. 

..,. : 

I ~";..,:';.!_ ·~.:X'/-~' ·~~t:2:_!_'27:oiefll~·~·~ 

50' 

164"50' 4d 

on .oa. 

35' 

v 

,. ... 90 .• 

·?r' ''" Mldnh~ht Mtn 

35' 

30' 25' 164"20' 

17 I 7!1 165" 55' 

./ ./1 fHI/ / / / / /1 

30' 25' 

"=hfr::d~i~a~::~·,~= ~;:.~.r.p:r.trhl:ha~PI 0 

I 

3 Miles 

I 

8ooloty modlfiad from Bulletin ~ 

Figure 2.--Geologic sketch map of the Serpentine-Hot Springs area., Seward Peninsula,. Alaska, showing sample 

localities. 

EXPLANATION 

SEDIMENTARY ROCKS 

D t,. ._i Silt, Sand, and gravel ~ 

Q. D i Port Clarence limestone ~~ 

i~ 

z 

~ Urullfferentiated D limestone Ill 

~~ slate, anol schist 

IGNEOUS ROCKS 

~ Granite II • 45.015(Piacerl 0 101.021(--) 

Sample location referred to in text 

-c;,,~;l 

Airstrip 

Hot Sprin9 

~ Placer minino operation 

• I Buildi"95 
and the North Fork Dredging Co., operating a dredge 

at the mouth of Harris Creek. In the upper Serpentine 

River valley, George Bodis was working near the 

mouth of Dick Creek, 12 miles northwest of Taylor, 

Near the mouth of Budd Creek, a tributary of American 

River, Dodson had resumed mining, but his camp was 

not visited. Mining had not yet been resumed at the 

Walsh camp on Humboldt Creek, about 8 miles east 

of Serpentine Hot Springs. 

Placer deposits in the Kougarok River valley 

occur both in the gravels of the present streams and 

in those on benches at two or more levels. The more 

conspicuous benches are at altitudes of 25 and 50 feet 

above the present stream. The benches are discontinuous and somewhat difficult to recognize because 

of erosion and soil creep. The bench gravels average 

10 to 20 feet in thickness. Drilling at the dredge site 

of the Kougarok Consolidated Placers, Inc., in 1946, 

showed the stream gravels to be 18 feet thick. All of 

the gravels are characteristically barren of gold 

except within a few inches of bedrock. 

RADIOACTIVE MINERAL INVESTIGATIONS 

Field studies 

At the time the field work was undertaken the 

portable radiation equipment available from commercial sources was relatively crude. The field instrument 

used in this investigation was constructed by the 

Geological Survey and utilized a 3-inch glass-walled 

gamma tube housed in a cylindrical brass probe. It 

was necessary to use this tube for both outcrop testing 

and semiquantitative assaying. By present-day standards the counter' would be considered inadequate for 

the type of work in which it was applied. Semiquantitative assays of bedrock samples were made in the 

field by comparison with a standard containing a known 

percentage of equivalent uranium. 

Heavy-mineral concentrates were panned from 

surface gravels of nearly all the major drainages in 

-an effort to determine whether the placer deposits 

contained sufficient radioactive material to constitute 

a source of supply. In addition, a study of the radioactivity and mineral constituents of such samples 

helped in the search for bedrock deposits. The samples 

represent surface gravel only, except those obtained 

from placer mines. Care was taken, however, to 

remove the uppermost well-washed gravel and to take 

samples at such depths that the sand and clay forrr.ed 

a tight matrix between the pebbles and retarded the 

downward movement of the heavy minerals. 

Laboratory studies 

Bedrock and placer samples were further 

concentrated in the laboratory for mineralogical study 

and for determining to what degree the radioactive 

material could be concentrated. The small quantity 

of material which would not pass through a 20-mesh 

sieve was rejected after scanning for radioactive 

mi.neral fragment$. Samples were split into fractions 

of greater and less than 2. 89 specific gravity. From 

some selected samples the minerals heavier than 

3. 3 specific gravity were removed. Measurement 

6 

of the equivalent uranium content of the plus 

2. 89 specific gravity fractions was made with a 

laboratory beta count~r. 

Distribution of radioactive ma<.erial 

Radioactive material was found in significant 

quantities in gravel or bedrock only in the area of 

intrusive granitic rock outcropping in the vicinity of 

Hot Springs Creek at the head of the Serpentine River 

and adjacent east-flowing drainage. 

Data concerning the bedrock samples are given 

in table 1, and the data on the placer or gravel 

samples are listed in table 2. 

Samples of the placer deposits of Budd and 

Eldorado Creeks (eastern tributaries of American 

River), the upper Kougarok River and its tributaries, 

and the headwater tributaries of the Serpentine River, 

excluding Hot Springs Creek, did not show sufficient 

radioactivity to be detected with the field counter, 

although a few of the heavy-mineral fractions of these 

sarr.ples are slightly radioactive. However, the investigation was not carried far enough into the · 

American and Goodhope River basins to entirely eliminate these placer areas; likewise, no work was done 

on the Kougarok River or its tributaries downstream 

from North Fork. 

One dredge concentrate was collected from the 

Kougarok Consolidated Placers, Inc. The material 

was derived from gravel on the east side of the 

Kougarok River between the mouths of Taylor and 

Homestake Creeks. No appreciable radioactivity was 

noted. 

The reconnaissance of Harris Creek failed to 

reveal any placer material along the creek's course 

comparable in radioactivity to that shown by the older 

sample from the Alaskan placer collection. Unfortunately, all of this original sample from Harris Creek 

was used in chemical analysis. The original sample 

may represent an extremely .local concentration or 

a sluice concentrate from gravel immediately above 

bedrock at one of the older placer workings, or the 

sample may have been incorrectly labeled and actually 

taken at another locality. 

Both 11 units 11 of theN orne group were examined 

in a number of localities with no radioactivity being 

apparent. The greenstone was tested at the outcrop 

area on Kougarok Mountain. The results we.re 

negative. The felsic rocks on Kougarok Mountain 

were not found in place. Placer samples from the 

drainage basin :ln which float from these rocks was 

found failed to show significant radioactivity. 

No radioactive minerals were found at the Ward 

copper prospect located on the north flank of Kougarok 

Mountain. Laboratory tests of the ore taken a few 

feet from the portal were negative. 

The locations of all samples collected in the 

Serpentine Hot Springs area are shown in figure 2. 

In the symbols used for sample localities on figure 2, 

for example, 93. 023, the figures preceding the 

decimal points are the field collection numbers of the 

samples. The figures including and following the 
decimal points represent the percent of equivalent 

uranium, in the heavy-mineral fractions. Data relating to samples 118 through 184 have been omitted 

from figure 1 and the tablP.s because of their insignificant radioactivity. 

Bedrock deposits of radioactive materiaL,-The 

granite in much of the Serpentine-Hot Springs area 

probably contains disseminated accessory minerals 

which are slightly radioactive, for gamma counts on 

all outcrops are above the average background count. 

Four samples of the granite from widely separated 

localities averaged 0. 005 percent equivalent uranium. 

The crushed material was separated with methylene 

iodide, and a very small quantity of heavy minerals 

was obtained. The small amount of heavy residue 

prevented a quantitative determination of the equivalent uranium content, but qualitative radiation tests 

indicate slight radioactivity. A sample of disintegrated 

granitic material collected from a sidehill wash, concentrated by the removal of the lighter minerals 

through creep action, contained 0. 004 percent equivalent uranium as determined in the field. The heavymineral fraction of this sample was found to contain 

0. 06 percent equivalent uranium. 

As stated above, four facies of the normal 

granite have been recognized. Samples of three, the 

pegmatites and fine-grained felsic and late mafic 

differentiates, all show radioactivity in excess of the 

granite, whereas outcrop tests of the early differentiates failed to indicate any concentration of radioactive minerals. The most radioactive unconcentrated 

sample (no. 82) of lode material is of the pegmatitic 

variety and contains 0. 032 percent equivalent uranium. 

The average of 20 samples of the pegmatitic facies of 

the normal granite indicates that this facies contains 

an average of about 0. 009 percent equivalent uranium. 

The sample of fine-grained felsic intrusive 

(no. 86) showing the greatest radioactivity contains 

0. 015 percent equivalent uranium. The average content 

of the three samples of felsic dikes is 0. 009 percent 

equivalent uranium. The most radioactive sample of 

the mafic dike material (no. 105) contains 0. 011 percent equivalent uranium. The average of the three 

sites sampled is 0. 008 percent equivalent uranium. 

Radioactive material in the alluvium.-The radioactivity of most of the concentrates is sufficient to be 

readily recognizable with a portable survey meter. 

The content of radioactive material in these concentrates 

panned from the gravel in the Serpentine-Hot Springs 

area ranges from 0. 000 to 0. 017 percent equivalent 

uranium. As the degree of concentra~~on obtained by 

panning is purely arbitrary and differs for each sample, 

the percent equivalent uranium of the semiconcentrates 

is not given in table 2. 

Further concentration of these samples in 

bromoform yielded heavy-mineral fractions containing 

0. 003 to 0. 84 percent equivalent uranium. The average 

equivalent uranium content of the heavy fractions of 

the 74 samples is 0. 064 percent. The increase in 

tenor of radioactive material effected by heavy-liquid 

separations indicates roughly the amount of beneficiation of the original gravel that might be obtained by 

the most efficient gravity methods under ideal conditions. The concentration ratio, that is, the weight 

of the original gravel to that of the heavy-mineral 

7 

fraction, gives a rough estimate of the amount of 

heavy minerals in the gravel that might be recovered 

at each sample locality. The concentration ratio 

averages 758 to 1. Assuming that 1 cubic yard of 

gravel weighs 3, 100 pounds, the heavy-mineral content averages 4 pounds per cubic yard of gravel. 

The amount of radioactive material in the 

unconcentrated gravel is too low to be determined with 

a counter, but may be computed from the concentration 

ratios and the equivalent uranium content of the heavymine'ral fractions (see table 2). 

Radioactive minerals 

Radioactivity in the gravel and bedrock 

originates from radioactive elements associated with 

the following minerals: zircon (ZrSi04), sphene 

(CaTiSi04 ), allanite (an hydrous silicate of Ca, Fe, 

Al, Ce, La, and Di), hydrogoethite (3Feg03. 4Ha0), 

and two unidentified secondary minerals. 

The small size of the zircon crystals prevented 

hand picking sufficient. material for a quantitative 

analysis of its activity. However, a magnetic separation of sample 18 yielded a nearly pure zircon 

fraction which was tested semiquantitatively with a 

laboratory beta counter and showed approximately 

0.15 percent equivalent uranium. Sodium-fluoride flux 

tests for uranium {Northrup, 1945) on this fraction 

were negative so that the radioactivity is thought to 

be due to thorium, although fluorescence due·to any 

uranium present may have been inhibited by the relatively high percentage of zirconium. 

Spectrographic analyses of hand-picked samples 

of allanite and sphene show 0. 1 and 0. 03 percent 

thorium, respectively. These figures are approximate, 

as they are close to the limit of sensitivity for the 

method used. Uranium was not detected spectrographically, and sodium-fluoride flux tests for uranium 

on these two minerals were also negative. 

The three secondary minerals, hydrogoethite 

and two unidentified, react positively for uranium in 

sodium-fluoride flux. Spectrographic analysis indicates a content of somewhat less than 1 percent. No 

thorium was detected. 

Field outcrop tests, as well as the laboratory 

studies, of the normal granite indicate the presence 

of minor amounts of radioactive accessory minerals 

rather evenly distributed throughout the mass. The 

widespread occurrence of zircon and sphene in the 

streams draining the outcrop area of the intrusive 

supports this conclusion. Allanite, which is less 

common and present in smaller amounts, is also an 

accessory mineral in the normal granite, although 

perhaps more irregularly disseminated. 

The radioactivity of the pegmatitic facies of the 

granite is due primarily to hydrogoethite and two 

other secondary minerals as yet unidentified. X-ray 

and spectrographi~ studies of these two minerals were 

inconclusive in suggesting the nature of the primary 

minerals from which they may have been derived. 

The major constituent elements of one of the secondary 

minerals are Cu, Ag, and Pb; traces of Be and Fe 

are present. The other mineral consists mainly of 
Al, Ca, Fe, Ag, Cu, Pb, and Si. The hydrogeothite 

contains traces of Cu, Ag, Be, and Si, in addition to 

the major constituent, Fe. 

The radioactive part of the heavy-mineral fraction of the fine-grained acidic intrusives is composed 

chiefly of zircon and sphene with lesser amounts of 

allanite, wnereas the radioactive heavy portion of the 

biotitic variant is composed primarily of allanite with 

only a few grains of zircon. 

Mineralogical studies of the placer samples 

indicate that the radioactivity .is due principally to zircon 

and sphene, both of which are present in all of the concentrates. Allanite is present in many of the samples, 

and hydrogoethite and the two unidentified secondary 

minerals occur in a somewhat smaller percentage of 

the concentrates. Although these minerals usually 

constitute a minor portion of the heavy minerals in 

comparison to the zircon and sphene, they doubtless add 

considerably to the radioactivity in many samples. 

'l'horium-uranium content.-The relative amounts 

of thorium and uramum in the gravel and bedrock 

deposits are dependent upon the nature of the mineral 

constituents. As shown above, the radioactivity of the 

placer deposits is primarily due to thorium-bearing 

zircon, sphene, and allanite, and to a lesser extent 

to secondary minerals containing uranium. The 

radioactivity of the normal granite, the fine-grained 

felsic intrusives, and the biotite-rich material is also 

due to the presence of thorium-bearing minerals. The 

secondary minerals of the pegmatitic facies contain 

uranium but thorium is not in quantities detectable 

by· spectrographic analysis. · 

CONCLUSIONS 

The investigations in the. Serpentine-Kougarok 

area failed to reveal either placer or bedrock deposits 

of radioactive material in quantities of present commercial interest. Although the field studies were 

8 

necessarily restricted in their scope, the results do not 

indicate further work to be warranted at the present 

time. 

LITERATURE CITED 

Brooks, A. H., 1922, The Alaskan :nining industry 

in 1920: U. S. Geol. Survey Bull. 722-A, p. 1-74. 

Collier, A. J., and others, 1908, The gold placers of 

parts of the Seward Peninsula, Alaska: U. S. Geol. 

Survey Bull. 328. 

Henshaw, F. F., and Covert)C. C., 1908, The 

Kougarok region: in, Water-supply investigations 

in Alaska, 1906-1907: U. S. Geol. Survey WaterSupply Paper 218, p. 77-98. 

Mertie, J. B., Jr., Lode mining and prospecting on 

Seward Peninsula: U. S. Geol. Survey Bull. 662-I, 

p. 425-449. 

Northrup, M. A. , 1945, Fluorescent bead test for 

uranium in minerals: Ind. Eng. and Chern., 

Anal. Ed., val. 17, p. 664-670. 

Smith, P. S., 1908, Investigations of the mineral of 

SewardPeninsula: U.S. Geol. SurveyBull. 345-E, 

p. 206-250. 

, 1941, The miner:al industry of Alaska 

-1=-·n-1,...,9...,3""'9,....: -=u'='"". S. Geol. Survey Bull. 926-A, p. 1-106. 

UNPUBLISHED REPORTS 

Harder, J. 0., and Reed, J. C., 1945, Preliminary 

report on radioactivity of some Alaskan placer 

samples: U. S. Geol. Survey Trace Elements 

Investigations Report 6. 

Killeen, P. L., and Ordway, R. J., 1946, Trace 

elements investigation at Ear Mountain, Seward 

Peninsula, Alaska: U. S. Geol. Survey Trace 

Elements Investigations Report 27. 

Shallit, A. B., 1941, Placer dep6sits in the upper 

Kougarok, Seward Peninsula, Alaska: Manuscript 

presented at the University of Alaska for the degree 

of Engineer of Mines. 
Table 1.--Data on bedrock samples, granite area in vicinity of Serpentine ~ot Springs 

Concentration eU content Sample eU content of heavy-mineral ratio (weight 

locality crushed sample concentrate 1 of the original Type of material 

no. (percent) (percent) sample to heavy 

minerals) 

74 0.016 0.034 2.0 Quartz-muscovite-tourmaline vein. 

75 .019 .057 3-3 Same vein no. 74; 8 feet distant. 

76 .oo8 • 033 5.6 Quartz-muscovite vein . 

77 .006 .017 2.3 Do. 

78 .004 .018 5.0 Do. 

79 .016 .024 2.7 Quartz-muscovite tourmaline vein. 

So • 005 .011 3.4 Quartz-muscovite vein . 

81 .007 • 025 19.5 Do . 82 .032 .096 9.5 Do. 

83 .004 .039 17.9 Biotite-rich granitic differentiate. 

84 .004 .020 4.5 Do. 

85 .009 • 021 1.9 Fine-grained felsic vein . 

86 .015 .071 150.5 Do. 

87 .004 .070 42.0 Do. 

88 .004 .036 4.6 Quartz-muscovite-tourmaline vein. 

90 .007 • 021 110.0 Fine-grained felsic vein . 

93 .012 . 023 6.9 Quartz-muscovite vein . 

96 .000 .009 2.3 Do . 102 .002 • 060 214.0 Disintegrated granite from sidehill wat 

103 .004 • 022 16.4 Quartz-muscovite vein . 104 .000 • 023 8.5 Iron-stained zone in granite . 105 • 011 .033 4.4 Biotite-rich granitic differentiate . 106 .004 .040 15.4 Quartz-muscovite-tourmaline vein . 107 .012 • 044 7.5 Quartz-muscovite vein. 

108 .000 . 021 7.0 Iron-stained zone in granite • 110 .007 .040 14.7 Iron-stained quartz vein in granite . lll • 008 . 035 6.8 Quartz-muscovite vein . 112 .009 .034 9.6 Do . 

113 • 008 .018 16.5 Do. 

1 Specific gravity +2.89. 

Table 2.--Data on placer samples, granite area in vicinity of Serpentine Hot Springs 

Sample locality no. eU content gravels in place 

Heavy-mineral concentrate 

(+2.89 sp gr) eU content 

(percent) 

Concentration ratio (weight 

original gravels to heavymineral fraction) 

60 

59 

58 

57 

56 

55 

26 

( percent) 

HOT SPRINGS CREEK AND TRIBUTARIES 

( <1ll ~mmp1es in order downstream) 

!Vlain right-limit t.ributary of north fork 

0.00011 0.041 

.00015 .oss 

.00008 .036 

.00011 .047 

.00006 .050 

.00009 .046 

.00016 .052 

t. 

378:1 

382:1 

448:1 

414:1 

852:1 

529:1 

334:1 

er. 
Table 2.--Data on placer samples, granite area in vicinity of Serpentine Hot Springs--Continued 

Sample locality no. 

42 

41 

40 

39 

91 

38 

eU content gravels Heavy-mineral concentrate Concentration ratio (weight 

in place (+2.89 sp gr) eU content original gravels to heavy-

(percent) (percent) mineral fraction) 

HOT SPRINGS CREEK AND TRIBUTARIES--Continued 

~outheast headwater branch of the north fork 

0.00010 

.00002 

.00001 

.00004 

.00015 

.00004 

0.041 

.oo8 

.018 

.040 

.178 

.015 

404:1 

514:1 

1,350:1 

1,031:1 

1,169:1 

389:1 

Minor tributary gulches near junction northeast and southeast headwater branches of north fork 

73 0.00118 0.840 711:1 

70 .00072 .463 635:1 

71 .00009 .039 445:1 

Northeast headwater branch of the north fork 

25 0.00002 0.016 895:1 

24 .00002 .015 645:1 

23 .00005 .035 705:1 

22 .00007 .044 674:1 

21 .00009 .053 587:1 

20 .00002 .054 3,400:1 

37 .00190 .260 137:1 

19 .00001 .017 1,260:1 

North from below junction of headwater branches to main right-limit tributary 

18 0.00011 0.070 630:1 

72 .00011 .100 929:1 

17 .00007 .028 391:1 

16 .00007 .070 952:1 

15 .00004 .052 1,226:1 

69 .00001 .006 421:1 

14 .00004 .036 856:1 

68 .00022 .112 508:1 

67 .00039 .103 264:1 

South fork Hot Springs Creek 

35 0.00005 0.069 1,473:1 36 .00003 .031 1,226:1 

32 .00002 .032 1,432:1 34 .00000 .003 728:1 

33 .00000 .005 835:1 

31 .00008 .050 670:1 

30 .00002 .012 544:1 

29 .00028 .064 225:1 

63 .00008 .038 502:1 

62 .00009 .034 375:1 61 .00007 .036 544:1 28 .00024 .062 262:1 

27 .00005 .036 750:1 48 .00013 .052 392:1 

46 .00006 .044 805:1 

47 .00003 .018 613:1 

10 
Table 2.--Data on placer samples, granite area in vicinity of Serpentine Hot Springs--Continued 

eU co~tent gravels HeaV¥-mineral concentrate Concentration ratio (weight 

in place (+2.~ sp gr) eU content original gt>avels to heavy-

(percent) (percent) mineral fraction) 

Sample locality no. 

HOT SPRINGS CREEK AND TRIBUTARIES--Continued 

Left-limit gully of Hot Springs Creek below forks 

45 o.ooooo 1 0.015 1 2,520:1 

Downstream from junction of main right-limit tributary and north fork 

66 

13 

12 

11 

10 

9 

7 

6 

5 

4 

3 

2 

1 

43 

44 

92 

109 

101 

95 

94 

100 

99 

97 

98 

0.00021 

.00046 

.00011 

.00027 

.00014 

.00018 

.00016 

.00004 

.00008 

.00004 

.00015 

.00015 

.00016 

.00003 

.00007 

o.o86 

.loB 

.062 

.o82 

.o6o 

.079 

.068 

.030 

.037 

.030 

.040 

.041 

.044 

.027 

.050 

PISH RIVER AND TRIBUTARIES 

0.00001 

.00001 

.00001 

0.020 

.031 

.oo8 

Humboldt Creek and tributaries 

0.00004 

.00012 

.oooo6 

.00000 

.00002 

.00002 

11 

0.038 

.057 

.037 

.016 

.009 

.010 

409:1 

236:1 

564:1 

3o8:1 

420:1 

428:1 

427:1 

867:l 

495:1 

,740:1 

259:1 

265:1 

278:1 

787:1 

667:1 

1,940:1 

2,835:1 

702:1 

1,086:1 

456:1 

637:1 

2,021:1 

462:1 

438:1 

INT.-DUP. SEC., WASH., D.C. 39229