GEOLOGICAL SURVEY CIRCULAR 335

RECONNAISSANCE FOR 

RADIOACTIVE DEPOSITS 

IN EAST-CENTRAL 

ALASKA, 1949

This report concerns work done on 

behalf of the U. S. Atomic Energy 

Commission and is published with 

the permission of the Commission.
UNITED STATES DEPARTMENT OF THE INTERIOR 

Douglas McKay, Secretary

GEOLOGICAL SURVEY 

W. E. Wrather, Director

GEOLOGICAL SURVEY CIRCULAR 335

RECONNAISSANCE FOR RADIOACTIVE DEPOSITS 

IN EAST-CENTRAL ALASKA, 1949

By Helmuth Wedow, Jr., M. G. White, and others

This report concerns work done on 

behalf of the U. 8. Atomic Energy 

Commission and is published with 

the permission of the Commission.

Washington, D. C., 1954

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

Page

CHAPTER A. Fairbanks and Livengood quadrangles, by Helmuth Wedow, Jr., J. M. Stevens, 

and G. E. Tolbert

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

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

Mines, prospects, and areas examined for 

radioactivity........................... 1

Fairbanks district................... 1

Melba Creek bismuth prospect... 1 

Tolovana mine................. 2

Cleary Hill mine............... 2

Elliott Highway ..................... 2

Geology ...................... 2

Radioactivity.................. 2

Goodluck Creek..................... 2

Conclusions.............................. 3

Literature cited.......................... 3

CHAPTER B.-Miller House-Circle Hot Springs 

area, by M. G. White and G. E. Tolbert

Abstract................................. 4

Introduction.............................. 4

Geology ................................. 4

Radioactivity investigations................ 4

Granite ............................ 4

Placers............................ 5

Conclusions.............................. 6

Literature cited.......................... 6

CHAPTER C. -Copper Creek copper lode prospect, Eagle district, by Helmuth Wedow, Jr. 

and G. E. Tolbert

Abstract................................. 7

Introduction.............................. 7

Geology ................................. 7

Page

CHAPTER C. Copper Creek copper lode prospect, Eagle district Continued

Radioactivity studies..................... 7

Conclusions............................. 9

Literature cited......................... 9

CHAPTER D. Placer concentrates from the 

Fortymile district, by M. G. White

Abstract................................ 10

Introduction............................. 10

Geology ................................ 10

Radioactivity and mineralogic studies...... 10

Conclusions............................. 12

Literature cited......................... 12

CHAPTER E.-Wilson Creek, My Creek, 

Ben Creek, and Chicken areas, Fortymile 

district, by Helmuth Wedow, Jr. and 

G. E. Tolbert

Abstract................................ 13

Introduction............................. 13

Measurement of radioactivity............. 13

Areas investigated....................... 13

Wilson Creek area ................. 13

Geology...................... 18

Radioactivity studies .......... 18

My Creek area..................... 18

Geology...................... 18

Radioactivity studies .......... 18

Ben Creek area.................... 19

Geology...................... 19

Radioactivity studies .......... 19

Chicken area ...................... 20

Summary and conclusions ................ 21

Literature cited......................... 22

ILLUSTRATIONS

Page

Plate 1. Map of parts of Fairbanks and Livengood quadrangles, east-central Alaska.................. In pocket

2. Geologic sketch map of the Miller House-Circle Hot Springs area .......................... In pocket

Figure 1. Sketch map of the Eagle district............................................................... 8

2. Sketch map of part of the Fortymile district, showing location of placer concentrates obtained

	from the district prior to 1949.............................................................. 11

3. Sketch map of the Fortymile district .......................................................... 14

4. Geologic sketch map of the Wilson Creek area.................................................. 15

5. Geologic sketch map of the My Creek area..................................................... 16

6. Geologic sketch map of the Ben Creek area .................................................... 17

	TABLES

	Page

Table 1. Data on samples collected along the Elliott Highway, 1949 ....................................... 3

2. Data on granite samples from the Miller House-Circle Hot Springs area .......................... 5

3. Locality distribution of uranium-bearing minerals in the Miller House-Circle Hot Springs area...... 5

4. Variation of radioactivity in the adit on the Copper Creek copper lode, Eagle district............... 7

5. Data on selected: samples from the Copper Creek copper lode prospect, Eagle district.............. 9

6. Equivalent-uranium content of placer concentrates obtained from the Fortymile district prior to 1949... 10

7. Data on samples collected in the Wilson Creek area............................................. 19

8. Data on samples collected in the My Creek area................................................ 19

9. Data on samples collected in the Ben Creek area ............................................... 20

10. Data on samples collected from Chicken and vicinity, 1949 ...................................... 21

11. Summary of data on radioactivity of materials tested in the Fortymile district, 1949 ................ 21
RECONNAISSANCE FOR RADIOACTIVE DEPOSITS 

IN EAST-CENTRAL ALASKA, 1949

By Helmuth Wedow, Jr., M. G. White, and others

CHAPTER A. -FAIRBANKS AND LIVENGOOD QUADRANGLES 

By Helmuth Wedow, Jr., J. M. Stevens, and G. E. Tolbert

ABSTRACT

In the summer of 1949, several mines and prospects in the Fairbanks and Livengood quadrangles, 

east-central Alaska, were examined for the possible 

presence of radioactive materials. Also tested were 

metamorphic and sedimentary rocks of pre-Cambrian 

and Paleozoic age crossed by the Elliott Highway, which 

extends from Fox, near Fairbanks, northwestward 

about 70 miles to the town of Livengood. Nuggets consisting chiefly of native bismuth and containing as much 

as 0.1 percent equivalent uranium had been found previously in a placer on Fish Creek several miles downstream from the reported bismuth-bearing lode on 

Melba Creek, but none of the lodes tested in 1949 exhibited radioactivity in excess of 0.003 percent equivalent uranium. The greatest radioactivity found in the 

rocks along the Elliott Highway was in an iron-stained 

pre-Cambrian schist and in a carbonaceous( ?) shale 

of Middle Devonian or Carboniferous age. Respective 

samples of these rocks contain 0.003 andO. 004 percent 

equivalent uranium. A possible local bedrock source 

for the euxenite-polycrase mineral found in a placer 

concentrate containing about 0.04 percent equivalent 

uranium was sought in the watershed of Goodluck Creek, 

near Livengood. The bedrock source of this mineral 

could not be located and it is believed that the source 

could be outside of the Goodluck watershed because 

drainage changes during Quaternary time may well 

have introduced gravels from nearby areas.

INTRODUCTION

The purpose of this report is to record the results 

of brief radioactivity reconnaissance investigations made 

during the summer of 1949 in the Fairbanks and Livengood quadrangles, east-central Alaska (pi. 1). The 

objectives of these investigations were:

(1) To examine several mineral deposits in the 

Fairbanks district not previously tested for radioactivity,

(2) to make a. radioactivity traverse of the 

Elliott Highway between Fox and Livengood,

(3) to search for a possible local bedrock source 

of a radioactive mineral of the euxenite-polycrase 

series found in a concentrate from a placer on Goodluck 

Creek in the Livengood district.

The field radioactivity tests were made with portable survey meters adapted to accept probes consisting

of six 1- by 14-inch or four 1- by 18-inch gamma tubes 

connected in parallel and covered with a cylindrical 

metal housing. The equivalent-uranium determinations 

given in this report were made by the writers with a 

laboratory sealer in Washington. This reconnaissance 

was done on behalf of the Division of Raw Materials of 

the U. S. Atomic Energy Commission.

MINES, PROSPECTS, AND AREAS EXAMINED FOR 

RADIOACTIVITY

Fairbanks district

Melba Creek bismuth prospect

A placer concentrate (obtained prior to the 

initiation of the search for radioactive ores in Alaska 

in 1945), from Fish Creek, a short distance below the 

mouth of Pearl Creek (pi. 1), contains 0.01 to 0.1 percent equivalent uranium (Wedow, Killeen, and others, 

1954, p. 7). The concentrate consists of a few small 

nuggets, mostly of native bismuth, with traces of flake 

and wire gold. Native bismuth is also reported (Hill, 

1933, p. 71) in concentrates from placers on Pearl 

Creek, a tributary of Fish Creek, and on the upper 

part of Gilmore Creek, west of Fish Creek.

The only recorded bedrock occurrence of bismuth 

in the upper part of the watershed of FishCreek upstream 

from the location of the concentrate containing the radioactive bismuth, is on the divide between Melba and Monte 

Cristo Creeks, both tributaries of Fish Creek near its 

head. Chapin(1914, p. 330, 331) describes the mineral 

deposit as a bismuth-bearing gold quartz vein cutting a 

fine-grained biotite granite. He reports that an opening 

on the vein at the time of his visit in 1912 was inaccessible, but that a surface exposure of the vein showed it 

to be about 5 inches thick with a vertical dip and an 

easterly trend. Chapin states further that in specimen 

material visible gold was imbedded in the native bismuth 

and bismuth sulfide. At the time of the reconnaissance 

in July 1949 the workings on the bismuth prospect were 

completely caved and all that remained of the operation 

was highly disintegrated rock on the dumps around the 

old filled shaft and in the ruins of a small mill.

Search of the dumps and the old mill revealed no 

traces of bismuth-bearing material. The maximum 

radioactivity observed was in the fine-grained biotite 

granite which, by field test, was estimated to contain 

no more than 0.002 percent equivalent uranium. Similar 

tests showed that the few pieces of iron-stained vein
quartz, also found on the dumps, contain less than 

0.001 percent equivalent uranium.

Tolovana mine

The Tolovana mine (Hill, 1933, p. 91, 92) lies 

on the east side of Willow Creek, a headwater tributary 

of Cleary Creek (pi. 1). It has long been abandoned 

and the adit is almost closed by ice. However, approximately 900 feet of underground workings along the ore 

deposit were still accessible in 1949. The deposit consists of stringers or veinlets of quartz enclosing lenses 

of quartz-biotite schist. Gold and metallic sulfides 

occur both in the quartz veinlets and in the schist adjacent to the veinlets. A traverse along the accessible 

workings showed no anomalous radioactivity. Ratemeter readings, using the 18-inch gamma probe previously described, ranged from 3 to 9 scale divisions 

on the 2. 0 range. A sample of highly iron-stained vein 

material from a point showing the maximum radioactivity contains only 0. 003 percent equivalent uranium.

Cleary Hill mine

The Cleary Hill mine (Hill, 1933, p. 93-96) lies 

on the divide between Chatham and Bedrock Creeks, 

tributaries of Cleary Creek (pi. 1). In 1949 only small, 

selected parts of the vein were being mined by two men 

working on a lease from the company, Cleary Hill Mines, 

Inc. The workings of the mine are extensive and intricate because the vein is offset by a complex series of 

faults. The vein ranges from 4 to 24 inches in width 

and consists of crushed iron-stained quartz with gold 

and minor amounts of arsenopyrite and stibnite. 

Yellow-green oxides of arsenic and antimony commonly 

stain many parts of the vein and enclosing schist 

country rock.

Radioactivity traverses were made along the main 

haulage tunnel on the 300-foot level and also on part of 

the 400-foot level. Higher levels and stopes were not 

examined because of caving. As in the Tolovana 

mine, about a mile to the southwest, the rate-meter 

readings ranged from 3 to 9 scale divisions on the 

2. 0 range. The maximum readings were obtained in 

the more heavily iron-stained parts of the vein and in 

iron-stained zones of fault gouge. Several selected 

samples of the iron-stained vein and gouge material 

contain no more than 0. 003 percent equivalent uranium.

Elliott Highway 

Geology

The Elliott Highway is about 70 miles long and 

extends from Fox on the Steese Highway to the northern 

terminus at Livengood (pi. 1). It cuts diagonally across 

the northeasterly trend of the regional structure. Four 

major sedimentary and metamorphic rock units form 

the bedrock along the highway. Brief descriptions of 

these units, summarized from reports by Mertie (1937) 

and Capps (1940) follow:

(l) The Birch Creek schist of pre-Cambrian age 

consists mainly of quartzite, quartz-mica, mica, feldspathic, and chloritic schists and quartzite with minor 

amounts of calcareous and carbonaceous schists and crystalline limestone. Quartz-mica and quartzite schists are

the prevalent types cropping out along the highway. 

These rocks are highly metamorphosed and practically 

none of the original sedimentary features of the rocks 

remain. Quartz veins are abundant throughout the schist.

(2) The sedimentary rocks of pre-Middle Ordovician 

age consist of red and green slaty shale, black argillite, 

chert, quartzite, phyllite, quartzose sandstone, and 

limestone. The rocks are metamorphosed but not to the 

same extent as the older Birch Creek schist. At a few 

localities a slaty cleavage has developed in the shale 

and the argillite.

(3) The Tolovana limestone of Middle Silurian 

age is exposed along the Elliott Highway only in the 

bluff along the north side of Globe Creek. It is a 

light- to dark-gray massive limestone that weathers to 

buff and white.

(k) Rocks of post-Middle Silurian age include 

sedimentary rocks of Middle Devonian and Carboniferous 

age. The predominant rock types are sandstone, quartzite, shale, slate, argillite, and limestone. Some of 

the shale is carbonaceous.

The distribution of these units along the highway 

is shown on plate 1. Because much of the highway 

crosses terrain covered by moss and muck deposits 

typical of interior Alaska, the chief exposures of bedrock are in road cuts and borrow pits.

Radioactivity

The radioactivity traverse along the Elliott Highway was made with the 18-inch gamma probe mounted 

on the hood of a jeep. The average speed of the 

jeep during the traversing was about 15 miles per hour. 

Background for the probe used was 4-5 scale divisions 

on the 2. 0 range.

The range and average of the rate-meter readings 

over the four major rock units are given below:

Rock unit

Pre-Middle Ordovician sedimentary

Middle Devonian and Carboniferous

Rate-meter 

(in scale 

on 2.0

Maximum 

range

^-11

i»- 10

2- k

k- 9

readings 

divisions 

range)

Average 

range

6

,7

3

1^-6

As a check on the significance of the maximum ratemeter readings along the route of the traverse, selected samples were taken at points of "high" radioactivity. 

The locations of these sampling points are shown on 

plate 1. The rock type and radioactivity data of the 

samples are given in table 1.

Goodluck Creek

Goodluck Creek is a headwater tributary of Livengood Creek in the Livengood gold-placer district 

(pi. 1). A concentrate from a placer operation on 

Goodluck Creek showed a content of 0.02 percent equivalent uranium when tested for radioactivity in 1945.1

1Hatder, J. O., and Reed, J. C., 1945, Radioactivity of some Alaskan 

placet samples: U. & Geol. Survey Trace Elements Inv. Kept. 6, p. 23 and 

table 1. (Unpublished.)
Table 1. Data on samples collected along the Elliott Highway, 1949

[Rate-meter readings in scale divisions of 2.0 range]

Sample 

no.

3842

3843

3844

3845

3846

3847

3848

Age and rock type

Pre-Cambrian (Birch Creek schist) iron-stained schist 

Pre-Cambrian (Birch Creek schist) unweathered gray-green schist 

Pre-Middle Ordovician -red slaty shale _____ _ _ .

Pre-Middle Ordovician gray shale -

Middle Devonian -Carboniferous brecciated shale and sandstone -

Middle Devonian-Carboniferous(?) felsite dike -

Rate -meter 

reading

9-11

8- n 9

8 Q

9-10

8- ,-, 9

7-8

8

,-, - 9

Equivalent 

uranium 

(percent)

0.003 

.003

.002

.001

.004

.001

.001

Reanalysis of this sample in 1946 indicated an equivalent uranium content ranging from 0. 031 to 0.048 percent but field studies in 1946 (Wedow, Killeen, and 

others, 1954, p. 11) failed to duplicate the concentrate.

The bedrock of the Goodluck Creek watershed is 

chiefly chert and silicified limestone of Mississippian 

age. The chert is dark gray to black and lies mostly 

on the northeast side of the creek; the silicified limestone is buff to white and lies, for the most part, on 

the northwest side of the valley. A small body of diorite 

or greenstone crops out on the southwest side of the 

creek near its head and, possibly, may be a dike lying 

between the chert and limestone.

Mineralogic study of the radioactive concentrate 

in the spring of 1949 determined that the radioactivity 

of the sample is due to a black pitchy or resinous 

metamict mineral which on X-ray analysis by Evelyn 

Cisney of the Geological Survey proved to be one of the 

euxenite-polycrase series. This series consists of 

niobates and titanates of yttrium, erbium, cerium, and 

uranium (Ford, 1932, p. 697, 698). The common 

mode of occurrence of euxenite-polycrase minerals at 

known localities throughout the world is in granite pegmatites or in placers probably derived from such rocks 

(George, 1949, p. 52-55).

The reconnaissance in the Goodluck Creek area 

in 1949 was an attempt to locate a possible local bedrock 

source of the euxenite-polycrase mineral. Radioactivity 

traverses were made on foot throughout the watershed 

of Goodluck Creek but no rocks showing significant 

radioactivity were detected. The chert, limestone, 

and diorite or greenstone were all estimated to contain 

0.001 percent equivalent uranium or less. No evidence 

of the possible occurrence of granitic rock types, particularly pegmatite, was observed in the Goodluck 

Creek watershed.

Concentrates (taken in 1946 and 1949) from old 

dumps of the placer operations on Goodluck Creek in 

the vicinity of the euxenite-bearing concentrate contain 

only 0. 002 percent equivalent uranium. The concentrates are chiefly limonite-hematite with some magnetite and traces of epidote, spinel, chromite, ilmenite, 

gold, cinnabar, and cassiterite.

CONCLUSIONS

The brief reconnaissance investigations in the 

Fairbanks and Livengood quadrangles in 1949 failed to 

reveal any occurrences of radioactive minerals warranting further study. It is likely that the radioactivity 

associated with bismuth nuggets in placers on Fish Creek

in the Fairbanks district may be of some significance 

but the scarcity of outcrops in the upper part of the 

watershed of Fish Creek precludes the use of portable 

survey meters for traversing in search of the lode 

source.

Further radioactivity traversing in the watershed 

of Goodluck Creek in search of the bedrock source of 

the euxenite-polycrase mineral found in a placer on 

thatcreekis also unwarranted because of the widespread 

cover of vegetal material, muck, and alluvium and the 

resultant paucity of outcrops. It is also likely that the 

bedrock source of this mineral may lie outside of the 

Goodluck watershed. Drainage changes in Quaternary 

time prior to the establishment of the present drainage 

system, as suggested by Mertie (1918, p.- 260-262), 

may have brought gravels into the watershed from such 

nearby areas as the Amy Creek drainage to the west. 

It is possible, therefore, that the source of the euxenitepolycrase mineral may have been in a now-eroded 

pegmatitic facies of a small albite granite intrusive on 

Amy Creek (Mertie, 1918, p. 248, pi. 13). Thus, the 

problem of the origin of this highly radioactive mineral 

is similar to that of the uraniferous ellsworthite and 

other radioactive minerals found in the placers of the 

Tofty tin belt of the Manley Hot Springs-Rampart district 

to the west (Moxham, 1953).

LITERATURE CITED

Capps, S. R., 1940, The Alaska Railroad region:

U. S. Geol. Survey Bull. 907. 

Chapin, Theodore, 1914, Lode mining near Fairbanks

[Alaska]: U. S. Geol. Survey Bull. 592, p. 321-355. 

Ford, W. E., 1932, Dana's Textbook of Mineralogy,

4th ed.: New York, John Wiley & Sons, Inc. 

George, D'Arcy, 1949, Mineralogy of uranium- and

thorium-bearing minerals: U. S. Atomic Energy

Commission, Technical Information Service,

RMO-563, 198 p. 

Hill, J. M., 1933, Lode deposits of the Fairbanks

district [Alaska]: U. S. Geol. Survey Bull. 849,

p. 29-163. 

Mertie, J. B., Jr., 1918, The gold placers of the

Tolovana district [Alaska]: U. S. Geol. Survey

Bull. 662, p. 221-277. 

______1937, The Yukon-Tanana region, Alaska:

U. S. Geol. Survey Bull. 872. 

Moxham, R. M., 1953, Reconnaissance for radioactive

deposits in the Manley Hot Springs-Rampart district,

east-central Alaska: U. S. Geol. Survey Circ. 317. 

Wedow, Helmuth, Jr., Killeen, P. L., and others,

1954, Reconnaissance for radioactive deposits in

eastern interior Alaska, 1946: U. S. Geol. Survey

Circ. 331.
CHAPTER B.-MILLER HOUSE-CIRCLE HOT SPRINGS AREA 

By M. G. White and G. E. Tolbert

ABSTRACT

Granite of Mesozoic( ?) age in the Miller HouseCircle Hot Springs area, east-central Alaska, contains 

0.005 to 0.007 percent equivalent uranium. The radioactivity is mostly caused by uranium in such primary 

accessory minerals of the granite as allanite, garnet, 

scheelite, sphene, and zircon. However, the presence 

of metallic sulfides, cassiterite, and uraniferous fluorite, malachite, and topaz in the granite or associated 

placers suggests the possibility of a post-emplacement 

or late-stage mineralization of the granite, presumably of hydrothermal origin, as a source for at 

least part of the uranium. Additional reconnaissance 

in the area to determine the presence or absence of 

hydrothermal uraniferous deposits of commercial grade 

appears warranted.

INTRODUCTION

The Miller House-Circle Hot Springs area is 

located in east-central Alaska about 100 miles eastnortheast of Fairbanks (pi. 2). The area lies in the 

highlands along the south edge of the Yukon Flats. It 

is easily accessible from Fairbanks via the Steese 

Highway or by plane to small airfields in the area (pi. 2).

Analysis of 33 placer concentrates (obtained prior 

to 1949 from mining operations on Porcupine, Bonanza, 

Miller-, Mastodon, Independence, Deadwood, Ketchum, 

Holdem, Switch, Portage, Half Dollar, and Harrison 

Creeks in the Miller House-Circle Hot Springs area) 

showed radioactive material in the range of 0. OX percent 

equivalent uranium only in concentrates from Ketchum 

and Portage Creeks. Preliminary mineralogic study of 

these samples indicated that the radioactive mineral 

may be monazite, although too little material was 

available for thorough examination.

In September 1949 a Geological Survey party consisting of Max G. White and Gene E. Tolbert, geologists, 

and Egil Salveson, camp assistant, conducted a reconnaissance in the Miller House-Circle Hot Springs area 

in an attempt to locate the source of the radioactive 

material found in the placers and to obtain more material for mineralogic study. The party was in the area 

for about one week at the close of the field season after 

having completed previously assigned projects elsewhere 

in interior Alaska. This work was done on behalf of 

the Division of Raw Materials of the U. S. Atomic 

Energy Commission.

GEOLOGY

The geology, mineral deposits, and mining activities of the Miller House-Circle Hot Springs area have

been described by Prindle (1913) and Mertie (1938). 

The bedrock of the area includes the pre-Cambrian 

Birch Creek schist, which is mostly a quartz-mica 

variety. This schist has been intruded by granitic 

rocks of Mesozoic( ?) age.

Johnson (1910) reports the occurrence of wolframite, cassiterite, arsenopyrite, pyrite, galena, 

limonite, and tourmaline, in addition to gold, in placer 

concentrates from Deadwood and Switch Creeks; 

arsenopyrite in quartz-feldspar veins on Switch Creek; 

and pyrite, galena, and quartz in mineralized fracture 

zones on the upper part of Deadwood Creek.

RADIOACTIVITY INVESTIGATIONS

Radiometric traverses in the Miller House-Circle 

Hot Springs area were made with commercial portable 

survey meters modified to accept probes of six 1- by 

14-inch gamma tubes or four 1- by 18-inch gamma 

tubes which were interchangeable with the standard 

6-inch beta-gamma probes.

As many localities as the limited time permitted 

were traversed for radioactivity. The courses of these 

traverses are shown on plate 2. The results of the 

radiometric traversing indicate that the granite and the 

wash from disintegrated granite are more radioactive 

than the adjacent schist and alluvium and were probably 

the source of the radioactive minerals found in the 

placer concentrates taken prior to this reconnaissance. 

Selected samples of the granite on Portage and Deadwood Creeks and at Miller House were taken for radioactivity analysis and mineralogic study. In addition, 

concentrates were taken from various placer workings, 

other stream gravels, and areas of granite wash to 

supplement the data on the granite samples. The equivalent-uranium analyses of these samples were made 

in 1949-50 by personnel of the Alaskan Trace Elements 

Unit. Most of the mineralogic determinations were 

made by Miss Kiyoko Onoda of the Trace Elements 

Section Washington Laboratory.

Granite

The data on the granite samples obtained in the 

Miller House-Circle Hot Springs area are summarized 

in table 2.

Mineralogic study of the heavy-mineral fraction 

of sample 49AWel77L from Portage Creek shows the 

presence of minor amounts of allanite, zircon, and 

apatite, and traces of magnetite and sphene. The 

allanite, apatite, and sphene are uraniferous. The 

heavy-mineral fraction of the granite on Deadwood 

Creek (sample 49AWel99L) contains chlorite, uraniferous
fluorite, and magnetite. The minerals of the heavy 

fraction of the granite near Miller House are as 

follows:

Minerals

Altered rock fragments with hematite and

Malachite 1 

Pyrite - 

Rutile - -----

Estimated 

volume 

(percent )

60

20

10

5

2

1

1

1

1 Indicates mineral is uranium-bearing.

The mineralogic study indicates that the radioactivity 

of the granite is apparently due mostly to uranium 

rather than thorium although this is not conclusive because 

no quantitative analyses were made. The locality

distribution of the uranium-bearing minerals in the 

granite is shown in table 3.

Placers

The radioactivity of the concentrates from stream 

gravels and granite wash in the Circle Hot Springs area 

(pi. 2) is comparable to that of the several samples 

available prior to 1949; that is, it is in the 0. OX range 

of percent equivalent uranium. The radioactivity, as 

in the granite, is more than likely due to uranium, 

rather than thorium.

The mineralogy of the placer concentrates is 

similar to that of the heavy-mineral fractions of the 

granite samples. Many other heavy minerals, though, 

are also present. Of significance are cassiterite and 

traces of chalcopyrite and fluorite on Portage Creek, 

scheelite on Hot Springs and Ketchum Creeks, cassiterite 

onKetchum and Deadwood Creeks, and topaz on Ketchum 

Creek. The locality distribution of the uranium-bearing 

minerals in the placers is shown by creek in table 3.

The presence of monazite was not verified in 

any of the samples collected in 1949.

Table 2. Data on granite samples from the Miller House-Circle Hot Springs area

Sample no.

Field

49AWel68L 

177L 

198L

199L 

200L 

203L 

204L

File

3649 

3655 

3669

3670 

3671 

3674 

3675

Location and description

Portage Creek; granite from bedrock in 

placer mine. 

Portage Creek; disintegrated granite from 

bedrock in placer mine. 

Deadwood Creek, just below mouth of Switch 

Creek; granite bedrock in placer cut.

______ _ -do- - 

Equivalent uranium (percent)

Unconcentrated

0.005

.005

.006 

.006 

.007 

.00?

Fraction 

>2.8 sp gr

0.020 

.056 

.023

.041 

 035 

 053 

.065

Concentration ratio

15:1 

15,400:1 

400:1

550:1 

325:1 

150:1 

325:1

Table 3. Locality distribution of uranium-bearing minerals in the Miller House-Circle

Hot Springs area

Locality and material sampled

Portage Creek:

Hot Springs Creek:

Ketchum Creek:

Deadwood Creek:

Miller House:

Allanite Apatite Flaorite

Garnet

Limonite Malachite Scheelite

<Dc

c/3

is]

ao

EH

Zircon
CONCLUSIONS

Although many of the uranium-bearing minerals 

in the granite and placer concentrates of the Miller 

House-Circle Hot Springs area are probably primary 

accessory minerals of the granite, the presence of 

fluorite, topaz, several of the metallic sulfides, 

cassiterite, and malachite indicates the possibility 

that hydrothermal alteration of the granite after its 

emplacement or in the late stages of its emplacement 

may in part be the source of the uranium. It is possible that concentrations of primary uranium minerals 

may occur in association with the granitic rocks in the 

Miller House-Circle Hot Springs area, particularly in 

the headwaters of Deadwood, Boulder, and Bedrock 

Creeks (pi. 2) in the vicinity of the granite-schist contact.

The possibility, however, that such concentrations may 

occur within the granite should not be overlooked.

LITERATURE CITED

Johnson, B. L., 1910, Occurrence of wolframite 

and cassiterite in the gold placers of Deadwood Creek, 

Birch Creek district [Alaska]: U. S. Geol. Survey 

Bull. 442-F, p. 246-250.

Mertie, J. B., Jr., 1938, Gold placers of the Fortymile, Eagle, and Circle districts, Alaska: U. S. 

Geol. Survey Bull. 897-C, p. 133-261.

Prindle, L. M., 1913, A geologic reconnaissance of 

the Circle quadrangle, Alaska: U. S. Geol. Survey 

Bull. 538.
CHAPTER C. -COPPER CREEK COPPER LODE PROSPECT, EAGLE DISTRICT 

By Helmuth Wedow, Jr. and G. E. Tolbert

ABSTRACT

Investigation of radioactivity anomalies at the 

Copper Creek copper lode prospect, Eagle district, 

east-central Alaska, during 1949 disclosed that the 

radioactivity is associated with copper mineralization 

in highly metamorphosed sedimentary rocks. These 

rocks are a roof pendant in the ''Charley River'' batholith 

of Mesozoic( ?) age. The radioactivity is probably due 

almost entirely to uranium associated with bornite and 

malachite.

INTRODUCTION

The Copper Creek copper lode prospect is located 

in the southwestern part of the Eagle district in eastcentral Alaska, and is about 60 miles west of the town 

of Eagle, which is near the international boundary. 

(See fig. 1.) The prospect is on the right bank of Copper 

Creek about 6 miles above the creek's confluence with 

the Charley River.

The Copper Creek prospect has never been reported in Geological Survey literature although knowledge of it is widespread among prospectors in interior 

Alaska. It was staked and partially developed by the 

Hudson brothers in the early 1900's, but has sin^e 

changed hands several times. The owner of the claim 

in 1949, Howard Sparks of Fairbanks, restaked the 

prospect in 1946 on the possibility that the gold, silver, 

lead, and tungsten content, in addition to the copper, 

might warrant further exploration.

The workings at the Copper Creek prospect consist 

of an adit in a cliff-surface showing of copper ore. The 

portal is 10 to 15 feet above the level of Copper Creek 

and the workings extend 114 feet underground. The ore 

showings occur only in about the first 40 feet of the adit. 

Lack of understanding of a complex structure apparently 

caused the earlier prospectors to wander off the trend 

of the ore-bearing zone with the result that the last 

60 feet of the adit are entirely in essentially barren rock.

The examination of the Copper Creek prospect 

was made as a side trip in connection with other radioactivity studies in a nearby part of the Fortymile district 

(see chapter E). Transportation to the prospect was by 

a helicopter furnished by Detachment "B, " TenthRescue 

Squadron, U. S. Air Force, based at Ladd Field, Fairbanks. 

The examination was made on August 17, 1949. The 

authors were accompanied by George O. Gates of the 

Geological Survey and Ho ward Sparks, owner of the prospect. The statement below on the geologic setting of the 

prospect has been taken mainly from field notes by Gates.

This work was done on behalf of the Division of 

Raw Materials of the U. S. Atomic Energy Commission.

GEOLOGY

The bedrock at the Copper Creek lode prospect, 

previously mapped in reconnaissance as granite of 

Mesozoic( ?) age (Prindle, 1913, pi. 2; Mertie, 1937, 

pi. 1), consists of highly metamorphosed sedimentary 

rocks. These rocks are apparently part of a small 

(several square miles) roof pendant in the "Charley 

River" batholith and acted as a host for the deposition 

of the metallic minerals found in the prospect.

Tentative identifications show a lime-silicate 

rock and an amphibolite as the two main lithologic 

types at the prospect. The bulk of the metallic minerals 

is in the lime-silicate rock, mainly along a contact 

with the amphibolite, with minor amounts of the metallic 

minerals disseminated through both rock types but in 

diminishing amounts away from the contact. Chalcopyrite, 

malachite, and azurite are the chief metallic minerals 

at the prospect. Minor amounts of galena are present 

and traces of gold, silver, and tungsten have been reported in assays.

RADIOACTIVITY STUDIES

The radioactivity of the rocks at the Copper 

Creek prospect was measured with a commercial model 

of a portable survey meter modified to accept both the 

standard 6-inch beta-gamma probe and a probe consisting of six 1-by 14-inch copper-walled gamma tubes 

connected in parallel.

The variation in radioactivity in the adit, as 

measured with the large gamma probe, is summarized 

in table 4.

Table 4. Variation of radioactivity in the 

adit on the Copper Creek copper lode, Eagle 

district

Distance (ft)

into adit

from portal

0- 2

2- 18

18- 32

32- 40

40- 44 '

44- 48

48- 54

54-114

Radioactivity

(divisions on

2.0 scale)

12

10

8

10

16-18

12

10

8

Rock type

,,

Lime -silicate rock

and amphibolite.

Do.

Amphibolite.

Lime-silicate rock.

Lime-silicate rock

with iron-stained

fracture zones.

Lime-silicate rock.

Do.

Do.
65°

through 

3731-L COPPER CREEK

LODE PROSPECT

EXPLANATION

5? 3725-L Sample from lode prospect 

O 3688 Stream concentrate

Figure 1. Sketch map of the Eagle district, Alaska.
Table 5. Data on selected samples from the Copper Creek copper lode prospect, Eagle district

[Equivalent-uranium analyses by members of the Alaskan Trace Elements Unit]

Sample 

no.

Equivalent uranium (percent)

Unconcentrated 

rock

Fraction 

<5«5 sp gr

Fraction 

>5-5 sp gr

Remarks

Placer

-z^QQ 1 0.005 2 0.015 Concentrate from about 50 pounds of gravel in Copper

Creek about 100 feet upstream from lode prospect.

"Portal" anomaly

5750 -L

5751-L

0.052

.001

3 0.044

.005

2 0.005

.002

Grab sample from most radioactive spot on east side

of portal.

Grab sample from slightly radioactive part of ore

zone on east side of portal.

"40-44" anomaly

5725-L

5726-L

5727-L

5728-L

5729 -L

0.005

.006

.005

.004

0.010

.004

u .012

.006

 0.002

.005

.002

.005

Grab sample of rock adjacent to most radioactive

iron-stained fracture zone.

Chip sample of 1-foot layer above most radioactive

fracture.

Chip sample of 1-foot layer below most radioactive

fracture.

Grab sample of same fracture zone as sample 5725-L

but about 6 feet downdip of fracture.

Specimen of rock immediately below fracture in sample

5725-L; radioactivity appears to be confined to

0.1 foot of rock immediately adjacent to fracture.

1Fraction <2.8 sp gr.

2Fraction >2.8 sp gr.

"Contains 0.058 percent U as determined by F. S. Grimaldi, Washington Trace Elements Laboratory.

4Contains 0.009 percent U as determined by F. S. Grimaldi, Washington Trace Elements Laboratory.

Testing with the 6-inch beta-gamma probe indicated that the radioactivity at the "portal" anomaly is 

localized around certain mineral groupings in the ore zone. 

At-the "40-44" anomaly the radioactivity appears to be 

confined to iron-stained surfaces or zones along lowangle fractures or faults in the lime-silicate rock. 

Data on selected samples from the locations of both 

anomalies are summarized in table 5.

As seen in table 5, the uranium in the samples 

from the Copper Creek prospect is concentrated mainly 

in material of less than about 3. 0 specific gravity. 

This material consists mostly of wollastonite and reddish or yellowish calcite. It also contains minor amounts 

of galena and bornite, mostly as inclusions in some of 

the wollastonite grains. The bornite is slightly altered 

to malachite. The uranium apparently occurs as an 

impurity in the bornite and malachite.

The radioactivity of the placer concentrate (sample 

3688, table 5 and fig. 1) from Copper Creek is probably 

due mostly to thorium within trace amounts of monazite.

CONCLUSIONS

Minor amounts of radioactive materials are 

associated with copper ores at the Copper Creek prospect in the Eagle district where a small roof pendant 

in the " Charley River" batholith appears to be highly mineralized. The radioactive minerals are bornite arid 

malachite, in which uranium apparently occurs as an 

impurity. Because of the limited time available for the 

examination of the prospect, reconnaissance of most of 

the roof-pendant area was not undertaken. It is possible 

that greater concentrations of uranium may occur in or 

immediately adjacent to the area of the roof pendant.

LITERATURE CITED

Mertie, J. B., Jr., 1937, The Yukon-Tanana region, 

Alaska: U. S. Geol. Survey Bull. 872.

Prindle, L. M., 1913, A geologic reconnaissance of 

the Circle quadrangle, Alaska: U. S. Geol. Survey 

Bull. 538.
CHAPTER D. -PLACER CONCENTRATES FROM THE FORTYMJLE DISTRICT

ByM. G. White

ABSTRACT

Studies of 24 placer-concentrate samples from 

the Fortymile district of east-central Alaska available in the Geological Survey's Alaskan Concentrate File prior to 1949 revealed only two samples 

containing significant amounts of radioactivity. Both 

samples are from Atwater Bar on the South Fork 

of the Fortymile River, a short distance below 

the confluence of Mosquito and Dennison Forks. 

The radioactivity is due to traces of uraniumbearing thorianite, which occurs as minute black 

cubes and fragments. No data are available as 

to the source of the thorianite.

INTRODUCTION

The purpose of this report is to present the 

results of laboratory radioactivity and mineralogic 

studies on the 24 placer-concentrate samples from 

the Fortymile district, east-central Alaska, available in the Alaskan Concentrate File of the Geological Survey prior to 1949. These samples were 

collected by several Survey geologists over a period 

of years from sluice boxes of placer-mining operations in the east-central part of the district. (See 

fig. 2.) Significant radioactivity was detected in 

only two samples, both from Atwater Bar on the 

South Fork of the Fortymile River. This work was 

done on behalf of the Division of Raw Materials of the 

U. S. Atomic Energy Commission.

Until 1949 the only field investigation for 

radioactivity made in the Fortymile district was a

reconnaissance in 1946 along the Alaska Highway 

at the southwestern edge of the district (Wedow, 

Killeen, and others, 1954).

GEOLOGY

The geology and mining of the Fortymile 

district has been discussed by Prindle (1905, 1907, 

1909, 1913) and Mertie (1930, 1937, 1938). The 

bedrock of the district consists chiefly of metamorphic rocks of pre-Cambrian and Paleozoic age. 

The metamorphic rocks are represented by many 

different lithologic types and are intruded by large 

and small masses of granitic rocks of Mesozoic( ?) 

age. Minor amounts of Tertiary volcanic rocks 

and coal-bearing sedimentary strata are also found 

in the district.

Atwater Bar is a deposit of bench gravels 

located on the left limit of the South Fork of the 

Fortymile River several miles below the confluence 

of Mosquito and Dennison Forks (see fig. 2). No 

extensive mining operations have been undertaken 

at Atwater Bar since it was dredged for several 

seasons in the mid-1930's. During the 1949 season 

a small outfit was prospecting in preparation for 

mining on a small scale.

RADIOACTIVITY AND MINERALOGIC STUDIES

The equivalent-uranium content of the placerconcentrate samples as determined in the laboratory is given in table 6.

Table 6. Equivalent-uranium content of placer concentrates obtained from the Fortymile district

prior to 1949

File 

no.

256

ooco

n '-rC. 

176

248

530

536

535

533

170 

85

27

534

53?

Location

Ingle Creek 

 do 

Chicken Creek, Claim 5-jj? Below 

Myers Fork, Purdy's claim -

Chicken Creek, Burrett's claim 

Chicken Creek, Busts' claim 

. do 

Lost Chicken Creek 

Equivalent 

uranium 

(percent)

0.001

.004

r\r\~\

.004

.005

.005

.004

.001

< .001 

.001

.001

.001

.002

File 

no.

277

284

79 i *Q 530

O)i

537

1

r\r\r-f\

1149Or~\ 29

OOC~1

Location

. do -

Gilleland Creek -

. do -

. do -

mouth of Napoleon Creek. 

Franklin Creek 

Equivalent 

uranium 

(percent)

0.041

.033 

.003

.001

<.001

.001

<'.001

.004

.001

.001

.007

10
20 Miles

Figure 2. Sketch map of part of the Fortymile district, Alaska, showing location of placer concentrates obtained

from the district prior to 1949.

Only the two samples (nos. 277 and 284) from 

Atwater Bar show noteworthy amounts of radioactivity. 

The principal radioactive mineral in these samples, 

as determined by spectrographic methods, is 

uranium-bearing thorianite. It occurs in trace 

amounts as minute black cubes and fragments in 

the minus 100-mesh size-fraction of the samples. 

No detailed information is available on the source 

of the gravels at Atwater Bar; therefore little 

can be said here as to the significance of 

thorianite in these gravels. The two samples 

from Atwater Bar are almost identical in mineral 

composition. The average composition is as follows:

Mineral

Spinel -

Rock- forming (chief Iji 

ferromagnesian silicates) minerals 

Percent

*>y

volume

25 

25 

15 

10 

10 

5

5

Mineral

"Plrvct 4- A . . . . ___

QrtV, OrtT 4 4- o

Cassiterite 

Percent

by

volume

2 

2 

1 

trace 

trace 

trace 

trace

11
Mineralogic studies show that the slight amount 

of radioactivity in the other samples apparently 

originates from traces of radioelements in zircon 

and sphene.

CONCLUSIONS

The radioactivity of placer concentrates obtained prior to 1949 from the Fortymile district 

is due chiefly to zircon and sphene. In two 

samples from Atwater Bar, however, most of the 

radioactivity is due to a uranium-bearing thorianite. 

Because the source of the Atwater Bar gravels 

is unknown, the significance of this thorianite 

cannot be evaluated. However, this occurrence 

may be a clue to possible bedrock sources of 

uranium in the drainage basin upstream from the 

location of the placer.

LITERATURE CITED

Mertie, J. B., Jr., 1930, Mining in the Fortymile district 

[Alaska]: U. S. Geol. Survey Bull. 813-C, p. 125-142.

____1937, The Yukon-Tanana region, Alaska: 

U. S. Geol. Survey Bull. 872.

____ 1938, Gold placers of the Fortymile, Eagle, and 

Circle districts, Alaska: U. S. Geol. Survey 

Bull. 897-C, p. 133-261.

Prindle, L. M., 1905, The gold placers of the Forty-mile, 

Birch Creek, and Fairbanks regions, Alaska: 

U. S. Geol. Survey Bull. 251.

____1907, The Fortymile gold placer district, 

[Alaska]: U. S. Geol. Survey Bull. 345-D, p. 187-199.

____1909, The Fortymile quadrangle, YukonTanana region, Alaska: U. S. Geol. Survey Bull. 375. 

1913, A geologic reconnaissance of the Circle

quadrangle, Alaska: U. S. Geol. Survey Bull. 538. 

Wedow, Helmuth, Jr., Killeen, P. L., and others, 1954, 

Reconnaissance for radioactive deposits in eastern 

interior Alaska, 1946: U. S. Geol. Survey Cire. 331.

12
CHAPTER E. -WILSON CREEK, MY CREEK, BEN CREEK, AND CHICKEN AREAS, FORTYMILE DISTRICT

By Helmuth Wedow, Jr. and G. E. Tolbert

ABSTRACT

A reconnaissance was conducted in the Wilson 

Creek, My Creek, and Ben Creek areas, Fortymile 

district, east-central Alaska, in 1949 in an attempt to 

locate three occurrences of high-grade uranium ores 

reported by prospectors. The search was unsuccessful. 

A maximum of 0. 005 percent equivalent uranium was 

found in felsic igneous rocks of the Wilson Creek and 

Ben Creek areas. The radioactivity of these rocks in 

the Wilson Creek area is probably due to traces of 

radioactive elements in the common accessory minerals 

of the igneous rocks; in the Ben Creek area it is probably 

due chiefly to thorium in monazite and allanite, which 

were identified in concentrates from gravels of streams 

draining areas underlain by the igneous rocks. Radioactivity tests of Tertiary sedimentary rocks in the 

vicinity of Chicken show that a sulfide-bearing montmorillonite-type clay contains as much as 0.005 percent 

equivalent uranium and that coked(?) coal and ash from 

a burned coal bed contain as much as 0. 003 percent 

equivalent uranium. A concentrate submitted by a prospector from a gold-placer deposit at Atwater Bar, a 

short distance east of Chicken, contains traces of 

uranothorianite and monazite and has an equivalent 

uranium content of 0. 027 percent.

INTRODUCTION

The purpose of this report is to give the results 

of reconnaissance in the Fortymile district, east-central 

Alaska (fig. 3), conducted in 1949 to investigate three 

possible occurrences of high-grade uranium ores reported by prospectors. These reported occurrences 

were in the vicinity of Wilson Creek (fig. 4), My Creek 

(fig. 5), and Ben Creek (fig. 6). Limited additional 

studies were made in the vicinity of Chicken as time 

permitted. (See inset, fig. 3.) The work was done on 

behalf of the Division of Raw Materials of the U. S. 

Atomic Energy Commission by a Geological Survey 

party consisting of Helmuth Wedow, Jr. and Gene E. 

Tolbert, geologists, and Fred Freitag, camp hand. 

The party was in the field from July 22 to August 20,

At the request of the Atomic Energy Commission, the U. S. Air Force detailed a helicopter and its crew and provided such other air 

support as was necessary to assist the Survey 

party in its operations. The assistance of the 

members of Detachment "B," 10th Rescue Squadron, 

U. S. Air Force, in developing the details of the 

air support furnished the Survey party is gratefully acknowledged. Lt. Murl Chamberlin and 

Sgt. Walter Embree, pilot and mechanic respectively, were the military personnel detailed 

directly to the Survey project.

The Fortymile district lies in east-central Alaska 

along the international boundary (see key map, fig. 3). 

Most of the district is drained by the Fortymile River 

and its tributaries (fig. 3). The town of Chicken is the 

only settlement of consequence within the district, although many placer-mining camps are scattered 

throughout the northeastern part of the district and 

homesteads are being claimed along the Alaska Highway 

on the southern edge of the district. Chicken is accessible by air by regularly scheduled flights from 

Fairbanks and, since September 1949, by ground traffic 

along the newly constructed southern part of the Taylor 

(Fortymile) Highway (fig. 3). Other parts of the Fortymile district are relatively inaccessible because the 

few other small airfields in the district are located 

mostly at the mining camps.

For the investigation of the Wilson Creek and 

My Creek areas the helicopter-supported Geological 

Survey party was based near the airstrip at Chicken 

and daily flights were made out to the areas under study. 

For the'reconnaissance in the Ben Creek area a temporary advance base was established on Slate Creek at 

the mouth of Gold Run.

MEASUREMENT OF RADIOACTIVITY

The radioactivity of rocks in the areas of the 

reported high-grade uranium occurrences in the Fortymile district was measured with high-count traverse 

probes consisting of six 1- by 14-inch gamma tubes 

connected in parallel and attached to modified commercial models of portable survey meters. For convenience in carrying for foot traversing, the counters 

and probes were lashed to packboards and the rate 

meters were attached to cables and carried by hand in 

front of the operator. The instrument response (background) in the field over most sedimentary and metamorphic rocks averaged about 900 counts per minute, 

or a rate-meter reading of about 5 scale divisions on 

the 2.0 mr/hr1 range.

In each area investigated selected samples were 

taken from rocks that exhibited radioactivity above the 

basic instrument response. The samples were later 

analyzed for their equivalent-uranium content in the 

laboratory by the authors.

AREAS INVESTIGATED 

Wilson Creek area -

In 1948 the Alaska Territorial Department of 

Mines reported that Mr. Charles Fillyez, former

1Milliroentgens per hour.

13
SKETCH MAP OF CHICKEN AND VICINITY

Base from U. S. Geol. Survey Bull 872, pi. 1 Trace elements field work by Helir.utll Wedow, Jr 

and Gene E. Tolbert, 1949

EXPLANATION

Helicopter flight

Approximate location

Toylor (Fortymile) Highway

(under construction)

© 3697-L 

Igneous rock sample

O S-256

Sedimentary rock sample

 3689

Placer concentrate

Figure 3. Sketch map of the Fortymile district, east-central Alaska.

14
Base and geology adapted from U. S. Geol. Survey 

Bull. 375, pi. 2 and Bull. 538. pi. 2

Figure 4. Geologic sketch map of the Wilson Creek area, Fortymile district, Alaska.
, ' > / y^ v -" ^^^ v T-* »^ 

r 1 7 J>?v 7 A < r v -jXr r « v v u*^ 

I v B^\ > < i, A t- ^t^*- J ^ -f v ) 

i^l-r > v 0 X * *rv* ""**-* 

T^Ts^V-Vp v ^> v- ; v-

> < *- -i - - ^o-^« ilx-1 - !-.«_, A^f,

^ Base and geology adapted from U. S. Geol, Survey Bull. 538, pi. 2*

. . ?

Figure 5. Geologic sketch map of the My Creek area, Fortymile district, Alaska.
Base and geology adapted from U.S. Geol. Survey Bull. 538, pi. 2

EXPLANATION

[^differentiated rocktj * *

Radioactivity travwrt*

* 

Helicopter landing

© 3711-L 

Samplt location

 3716 

Stream concentrate

Figure 6. Geologic sketch map of the Ben Creek area, Fortymile district, Alaska.

17
Alaskan prospector, had information about a pitchblende 

occurrence in the Fortymile district. When questioned 

early in 1949 by W. S. Twenhofel of the Geological 

Survey, Fillyez indicated that in 1919 he had found a 

heavy black mineral in a vein on the crest of the ridge 

west of the confluence of the North and South Forks of 

the Fortymile River in the vicinity of Wilson Creek 

(fig. 4). The mineral subsequently was identified as 

pitchblende by Mr. Seymour a private assayer in 

Fairbanks, now deceased. Fillyez stated further that 

an old trail leading westward along the ridge toward 

Wilson Creek from the confluence of the forks would 

lead to the vein. Scattered remnants of this trail were 

located along this ridge in the course of the reconnaissance in 1949.

Geology

The geology of the Wilson Creek area has been 

mapped by reconnaissance methods by Prindle (1909, 

pi. 2; 1913, pi. 2) in the course of studies of the Fortymile and Circle quadrangles. The bedrock consists of 

the pre-Cambrian Birch Creek schist and granitic intrusivesof Mesozoic(?) age (fig. 4). In the Wilson Creek 

area the Birch Creek schist is predominantly a quartzmica schist, but locally contains such metamorphic rock 

types as quartzite, coarse-crystalline marble, and 

micaceous and chloritic schists. Small dikes and sills 

of intrusive granite, apparently offshoots of the large 

igneous mass at Monument Peak (fig. 4), and quartz 

veins of unknown age and origin occur in the area mapped 

as Birch Creek schist, but their small size prevents 

their being distinguished separately on the map.

Radioactivity studies

Approximately 17 miles of foot traverses were 

made along the ridges in the vicinity of Wilson Creek 

(fig. 4) west of the confluence of the North and South 

Forks of the Fortymile River in an attempt to locate 

the reported Fillyez pitchblende occurrence. No significant radioactivity anomaly was detected that might 

lead to the discovery of the pitchblende.

Most rate-meter readings over the various 

lithologic types of the Birch Creek schist ranged between 5 and 7 scale divisions (2.0 range) or approximately 0.001 percent or less equivalent uranium. 

Readings over the granitic rocks in the Wilson Creek 

area ranged from 13 to 18 scale divisions (2. 0 range) 

and were the highest obtained in the area. The equivalent-uranium content of the granitic rocks ranges 

from 0. 001 to 0. 005 percent. This radioactivity is 

assumed to be due to the presence of traces of radioactive elements in the common accessory minerals of 

the granite.

A zone of limonitic alteration in brecciated schist 

(sample 3692-L, fig. 4) contains 0.004 percent 

equivalent uranium. This slightly anomalous radioactivity is most likely due to traces of uranium in the 

iron oxides. A search was made for other evidence of 

mineralization, particularly at or near the graniteschist contact, but none was found.

The data on the samples obtained in the Wilson 

Creek area are given in table 7; the locations of the 

samples are plotted on figure 4.

My Creek area

An occurrence of pitchblende in the My Creek 

area (fig. 5) was reported by Mr. E. D. Manske to the 

Geological Survey through the Territorial Department 

of Mines in the latter part of 1948. The original discovery was supposed to have been made by Mr. William 

Kruhm, former Alaskan prospector, now deceased, in 

1904 while he and one other man were prospecting for 

gold. According to Manske the presence of pitchblende 

was substantiated by a report on samples submitted by 

Kruhm to a commercial assay firm in the States.

Geology

Reconnaissance geologic mapping in the My 

Creek area (fig. 5) was done by Prindle (1913, pi. 2) in 

the course of his studies in the Circle quadrangle. The 

bedrock consists of the pre-Cambrian Birch Creek 

schist and granitic intrusives of Mesozoic(?) age. In 

general, the geology is very similar to that of the 

Wilson Creek area, described above.

Some of the quartz veins in the My Creek area 

are as much as several feet thick and normally are 

highly fractured and stained with hematite. One quartz 

vein observed, was on the "Ruby silver claim" (sample 

locality 3707-L, fig. 5) which, in addition to quartz and 

hematite, contains pods of galena, partly altered to 

cerussite, and calcite. No pyrargyrite (ruby silver) 

was identified in later laboratory study of samples 

taken from this vein. A stibnite prospect has been reported on the divide between My Creek and Our Creek 

several miles west of the "Ruby silver claim. "

Radioactivity studies

About 18 miles of radioactivity traverses were 

made on foot in the My Creek area (fig. 5) in an attempt 

to locate anomalous radiation that would lead to the 

discovery of the pitchblende-bearing vein reported by 

Manske who accompanied the party for one day in the 

field. No significant radiation was detected in the 

course of the traversing, nor did tests of concentrates 

(samples 3699 and 3704, fig. 5) from gravels on Our 

and My Creeks show any radioactivity or mineral content that would suggest the occurrence of a high-grade 

uranium deposit in the watersheds of the streams above 

the point of the sampling. The hematite-stained quartz 

veins, one of which also contains lead minerals, showed 

no radioactivity. The maximum radioactivity (10 scale 

divisions on the 2. 0 range and 0. 003 percent equivalent uranium) found in the area was in the coarsegrained granite at the head of Our Creek (sample 

locality 3706-L, .fig. 5). This slight amount of radioactivity is believed to be due to traces of uranium and 

thorium commonly found in the accessory minerals of 

felsic igneous rocks. A large area of schist heavily 

stained with hematite on the north side of the first 

stream north of My Creek (sample locality 3709-L, 

fig. 5) was also slightly radioactive. The maximum 

radioactivity detected at this locality was 9 scale 

divisions on the 2. 0 range. A sample of this altered 

rock contains 0.002 percent equivalent uranium.

The data on the samples collected in the My 

Creek area are listed in table 8; the locations of the 

samples are shown on figure 5.

18
Table 7. Data on samples collected in the Wilson Creek area

Sample 

no.

3692-L 

3693-L

"^Olio T

3694b-L

3695 -L

Description and location

Iron-stained zone in contorted brecciated schist; on divide between 

Wilson and Buckskin Creeks about 4-| miles east of Monument Peak. 

Granitic dike in schist; on divide between Wilson and Buckskin Creeks 

about 5 5- miles east of Monument Peak. 

Granite; at summit of Monument Peak 

Pegmatitic(?) facies of granite; same location as 3694a-LGranite; from spur of Monument Peak about -J mile northeast of summit--

ell1 

(percent)

0.004

.005

.005

.001

.005

Rate -meter 

reading2

10 

13

15 3 15

18

'Equivalent uranium as determined in the laboratory.

2In scale divisions on 2.0 range.

3High reading probably due to adjacent granite.

Table 8. Data on samples collected in the My Creek area

Sample 

no.

Description and location

eU1 

(percent)

Rate-meter 

reading2

3699

3704

3705-L

3706-L

3707-L

3708-L

3709-L

Heavy-mineral fraction 3 of panned concentrate of 50 pounds of gravel;

from dump of old placer-gold prospect pit on Our Creek. 

Heavy-mineral fraction 3 of panned concentrate of 50 pounds of gravel;

from dump of old placer-gold prospect pit on My Creek at mouth of

Eva Creek. 

Massive shattered quartz vein with hematite staining along fractures;

on ridge between My and Eva Creeks.

Coarse-grained granite; on divide at head of My and Our Creeks 

Quartz vein containing galena and hematite with some limonite and

cerussite, also some calcite in the gangue; "Ruby silver claim" on

ridge between My and Eva Creeks.

Iron-stained (gossan) rock with a few fragments of galena; same location as 3707-L. 

Hematite-stained quartz-mica schist with scattered quartz veinlets; on

ridge on north side of first stream north of My Creek.

0.002

.001

< .001

.003 

<.001

<.001 

.002

10

6

^Equivalent uranium.

2 In scale divisions on 2.0 range.

'Greater than 2.8 specific gravity.

Ben Creek area

An occurrence of "yellowish uranium ore" on one 

of the branches of the first south-flowing tributary of Ben 

Creek (fig. 6) in the northwestern part of the Fortymile 

district was reported by Mr. William Ott of Fairbanks to 

the Geological Survey through the Territorial Department 

of Mines in 1948. Asample collected by Ott in 1918 was 

reportedly assayed by a laboratory at Seattle, Washington 

and was reported to have a "highcontent of uranium." 

However, no records are available for checking because 

the laboratory went out of business about 1923-24.

Geology

The~g¥plQgy-of the Ben Creek area (fig. 6) was 

mapped by Prindle (1913, pi. 2) in his studies of the 

Circle quadrangle. The rocks consist of pre-Middle 

Ordovician sedimentary rocks, chiefly clastic, intruded 

by granite of Mesozoic( ?) age. An area-of porphyritic 

rhyolite between Green Creek and Ruby Creek shown 

on figure 6 as part of the granite may be a border phase 

of the granite. On the other hand, it may well be one 

of the Tertiary rhyolites described by Mertie (Prindle, 

1913, p. 44, 45), although sufficient evidence is not 

available to substantiate this possibility.

Little is known of the possibilities for mineral 

deposits in the area. Gold Run in the southern part of 

the area (fig. 6) was mined for placer gold in the early 

part of the century. Ott reports, also, that large 

fragments of vein float containing galena occur in the 

gravel at the mouth of Fourth of July Creek (fig. 6). 

A small copper prospect (see Chapter C) is located on 

Copper Creek about 22 miles northwest of the mouth 

of Ben Creek.

Radioactivity studies

i

Between 6 and 7 miles of radioactivity traversing 

was done in the Ben Creek drainage basin in the vicinity 

of the "yellowish uranium ore" occurrence reported 

by Ott. No anomalous radioactivity was found beyond 

that which normally occurs in most felsic igneous 

rocks. Rate-meter readings for the most part,were 

constant at about 9 scale divisionsjon-the' 2.0 range. 

These readings increased to 10 and 11 scale divisions 

toward the contact of the granite with the sedimentary 

rocks in the part of the traverse to the mouth of Ben 

Creek. Selected samples (nos. 3711-L to 3714-L, 

fig. 6) of the granite contain from 0. 002 to 0. 004 percent equivalent uranium. In addition to the radioactivity traverses on the ground, the area was searched

19
carefully from the air at low altitudes with the helicopter 

for the highly colored zones indicative of possible 

mineralization; none were found in the Ben Creek drainage area or in the Slate Creek drainage area above the 

mouth of Ben Creek. Southwest of the Ben Creek 

drainage, however, a large orange-colored hill between 

Green Creek and Ruby Creek was prominent and showed 

a slightly greater radioactivity than surrounding rocks 

when tested from the air. The rock in this hill is a 

porphyritic rhyolite varying in color from yellow through 

orange and red to purple. Ground traverses over the 

rhyolite showed rate-meter readings of 14 to 18 scale 

divisions on the 2.0 range; samples (nos. 3720-L to 

3724-L, fig. 6 and table 9) of the rhyolite contain 

0.005 percent equivalent uranium. In contrast to the 

granite and rhyolite, rate-meter readings over the 

clastic sedimentary rocks on a traverse along the lower 

part of Gold Run (fig. 6) showed only 4 to 6 scale divisions 

on the 2. 0 range. These readings indicate an equivalent-uranium content of less than 0.001 percent for the 

rocks along the traverse. The radioactivity data on 

samples taken in the Ben Creek area are given in 

table 9. The locations of the samples are plotted on 

figure 6.

As a check on the possible radioactive minerals 

in the granitic rocks, concentrates were taken from 

the stream gravels at the mouth of Ben Creek, on Slate 

Creek just above the mouth of Ben Creek, at the mouth 

of Ruby Creek, and on Gold Run (samples 3716 to 3719, 

fig. 6). The data on the radioactivity of these concentrates are given in table 9. Monazite and allanite are 

present in the concentrates from Ben, Slate, and 

Ruby Creeks, therefore the radioactivity is assumed

to be due chiefly to thorium. Although the granite 

samples were not examined specifically for monazite 

and allanite, the presence of these minerals in the 

concentrates from gravels of streams with drainage 

basins entirely within the granite suggests that they 

probably occur as accessory minerals in the granite. 

Supporting this hypothesis is the fact that the concentrate from Gold Run, which does not drain any area of 

granitic rock, is not appreciably radioactive and does 

not contain either allanite or monazite.

Chicken area

A few radioactivity tests were made in the vicinity 

of Chicken. (See inset, fig. 3.) In addition, several 

slightly radioactive samples were donated to the Geological Survey by prospectors. The data on the samples 

obtained in the vicinity of Chicken are listed in table 10; 

the locations of the samples are plotted on the inset of 

figure 3.

The radioactive sluice-box concentrate from the 

placer-gold operation on Atwater Bar is comparable 

to similar concentrates from Atwater Bar described 

by White (see Chapter D). The chief radioactive minerals are uranothorianite and monazite. Although time 

did not permit a search for the bedrock source of the 

uranothorianite, the brittle nature of this mineral, and 

hence its tendency to shatter when transported, suggests 

that the source is not far distant.

Prindle (1909, p. 24 and pi. 2) describes and 

maps a small area of Tertiary coal-bearing sedimentary

Table 9. Data on samples collected in the Ben Creek area

Sample 

no. Description and location

eU 1 

(percent)

Rate-meter 

reading2

3711-L

3712-L

3713-L

3714-L

3715-L

3716

3717

3718

3719

3720-L

3721-L

3722-L

3723-L

3724-L

Medium- to coarse-grained granite; on divide between Ben Creek and

Slate Creek drainage. 

Coarse-grained (pegmatitic facies?) granite, in large stream boulder;

from tributary of Ben Creek about £ mile above mouth. 

Medium- to coarse-grained granite bedrock (weathered); same location

as 3712-L. 

Medium- to coarse-grained granite on left limit of Ben Creek about

1 mile above mouth. 

Medium- to coarse-grained granite on left limit of Ben Creek about

100 yards above mouth. 

Heavy-mineral fraction 3 of panned concentrate from about 100 pounds

of stream gravel; on Ben Creek about 250 feet above mouth. 

Heavy-mineral fraction 3 of panned concentrate from about 100 pounds

of stream gravel; on Slate Creek about 500 feet above mouth. 

Heavy-mineral fraction 3 of panned concentrate from about 75 pounds

of stream gravel; on Ruby Creek about \ mile above mouth. 

Heavy-mineral fraction 3 of panned concentrate from about 100 pounds

of stream gravel; on Gold Run about \ mile above mouth. 

Hematite- and limonite-stained porphyritic rhyolite of granite; on

west flank of large "orange hill" between Ruby and Green Creeks. 

Orange-colored residuum from rhyolite; same location as 3720-L - 

Purplish-colored rhyolite; about 1 mile northeast of 3720-L - 

Iron-stained rhyolite; about £ mile northeast of summit of

"orange hill." 

Same as 3723-L; at summit of "orange hill" 

0.002

.004

.002

.003

.003

.096

.068

.015

.003

.005

.005

.005

.005

.005

9

10

11

18

18

14

14

14

Equivalent uranium.

2In scale divisions on 2.0 range.

3Greater than 2.8 specific gravity.

20
rocks in the vicinity of Chicken. The samples of montmorillonite-type clay from deeply weathered rock in the 

valley of the first creek west of Chicken Creek (table 10) 

most likely were collected from a bed in the Tertiary 

sequence. The samples contain 0.001-0.005 percent 

equivalent uranium and consist mostly of clay with 

some sand-size particles and a minor amount of coarser 

material. The coarser material is chiefly in the form 

of rounded pellets. The entire material of the samples, 

however, is too disintegrated to determine whether the 

original rock was igneous or sedimentary in origin. 

A few of the pellets contain small crystals of pyrite 

partly altered to hematite and limonite. The heavymineral fraction greater than 2. 8 specific gravity of 

sample 3701-L contains as much as about 0.06 percent 

equivalent uranium. It consists of about 99 percent 

pyrite with traces of hematite, goethite, covellite, 

chalcopyrite, biotite, and chlorite. The radioactivity 

is probably due to uranium occurring as an impurity in 

the iron oxides.

The coked(?) coal and related ash beds containing 

as much as 0. 003 percent equivalent uranium collected near Chicken are also part of the Tertiary

sedimentary rocks mapped by Prindle (1909, pi. 2). 

The proximity of a body of basalt to the coal and the 

fact that much of the coal now exposed was coked(?) 

rather than completely burned suggests that the burning 

and possible coking accompanied the emplacement of 

the basaltic rocks. The slightly anomalous radioactivity 

of the coal and ash beds is probably due to the concentration of traces of radioactive elements in the process 

of coking and burning.

SUMMARY AND CONCLUSIONS

Three occurrences of high-grade uranium ores 

reported by prospectors in the Fortymile district were 

not found. The maximum radioactivity detected was 

in felsic igneous rocks, which contain as much as 

0.005 percent equivalent uranium. Concentrates from 

gravels of creeks draining areas underlain by the felsic 

igneous rocks contain as much as 0. 096 percent equivalent uranium. This' radioactivity is assumed to be 

due chiefly to thorium in allanite and monazite. A 

summary of the materials tested in the Fortymile 

district is given in table 11.

Table 10. Data on samples from Chicken and vicinity, 19^9

Sample 

no.

Description and location

eU 1 

(percent)

Rate-meter 

reading2

363Q

3690

3697-L

3698-L

3700-L

3701-L

3702-L

3703-L 

S-256

S-257 

S-258 

S-259

Sluice-box concentrate from placer-gold operations at Atwater Bar;

donated by Lon L. Davis. 

Same as sample 3689-- __-_ _____ ________ ______ __

Coarse-grained granitic rock; in borrow pit along Ta'ylor Highway about

4- miles southwest of Mosquito Pork bridge. 

Mafic dike about 6 feet thick cutting granitic rock at locality of

sample 3697-L. 

Montmorillonite-type clay from artificial exposures on first creek

west of Chicken Creek. 

Same as sample 3700-L- ______ __ __ _ - ________ _ ___

Same as sample 3700-L; hard pellets in clay appear to be sulfide

bearing. 

Same as sample 3700-L; mostly clay ____ _ _____ 

Ash bed from burned coal; about \ mile northwest of Chicken -------

Coked(?) coal; same location as sample S-256- ------ ________ ___

Burned clay; same location as sample S-256-- --___- ---_ - ____

Coked(?) coal; same location as sample S-256 - --- --

0.027

.003

.002

.002

.003

.005

.001

.003

.002

.001

.002

11 

IQ 

10 

10

Equivalent uranium. 

2In acale divisions on 2.0 range.

Table 11. Summary of data on radioactivity of materials tested in the Fortymile district,

Type of material tested and location

Equivalent

uranium 

(percent)

Type of material tested and location

Equivalent

uranium

(percent)

Granitic rocks:

Wilson Creek area - 

My Creek area-- --- 

Ben Creek area - 

Vicinity of ChickenPorphyritic rhyolite:

Ben Creek area - - 

Mafic dike:

Vicinity of ChickenMineralized quartz 

veins:

My Creek area -

0.003-0.00^

.003

.002- .004 

.002

.005

.002

.001

Hematite- or limonite-stained schist: 

Wilson Creek area --- - - 

My Creek area-- -- 

Sulfide-bearing clay:

Vicinity of Chicken 

Coked(?) coal and ash beds from 

burned coal:

Vicinity of Chicken 

Concentrates from placers:

My Creek area - 

Ben Creek area- - - -- 

Vicinity of Chicken 

0.00^ 

.002

0.001- .005

.001- .003

.001- .002

.003- .096

.003- .027

21
Although the search for high-grade uranium 

deposits in the Fortymile district in 1949 was unsuccessful, the district cannot be arbitrarily dismissed as 

having no potential for radioactive minerals. It is significant to note that small amounts of uranium occur in a 

copper deposit on Copper Creek (see Chapter C) a short 

distance northwest of the district, and traces of uranothorianite are found in the placers of AtwaterBar near 

Chicken. In addition, occurrence of £Luorite(Wedow and 

others, 1953, p. 13) and metallic minerals (Mertie, 1937, 

p. 244, 245), commonly associated elsewhere with 

uranium, are known in the district. At present, however, too little geologic information is available to 

suggest specific localities for uranium prospecting.

LITERATURE CITED

Mertie, J. B., Jr., 1937, The Yukon-Tanana region,

Alaska: U. S. Geol. Survey Bull. 872. 

Prindle, L. M., 1909, The Fortymile quadrangle,

Yukon-Tanana region, Alaska: U. S. Geol. Survey

Bull. 375. 

_____1913, A geologic reconnaissance of the

Circle quadrangle, Alaska: U. S. Geol. Survey

Bull. 538. 

Wedow, Helmuth, Jr., and others, 1953, Preliminary

summary of reconnaissance for uranium and

thorium in Alaska, 1952: U. S. Geol. Survey

Circ. 248.

22

INT.-DUP. SEC.. WASH.. D.C- S>4i«!t
GEOLOGICAL SURVEY CIRCULAR 335 PLATE 1

*

EXPLANATION

Undifferentiated sedimentary 

rocks

Tolovana limestone

Undifferentiated sedimentary

Birch Creek schist 

Contact

Sample localities along Elliott Highway

Mines and prospects

Occurrence of euxenite-polycrase 

mineral

bismuth prospect

Contour interval 20Ofeet KEY MAP OF EAST-CENTRAL ALASKA Datum is moan sea level

MAP OF PARTS OF FAIRBANKS AND LIVENGOOD QUADRANGLES, EAST- CENTRAL ALASKA
m 

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m

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CO

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m 

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o

o

CO 

7^m 

H 

o

T)

OTl

H

mm

o

CO

m

i

o

3) or~ 

m

o

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CO

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CO

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