GEOLOGICAL SURVEY CIRCULAR 185 OF

RECONNAISSANCE FOR RADIOACTIVE 

DEPOSITS ALONG THE 

UPPER PORCUPINE AND LOWER COLEEN 

RIVERS, NORTHEASTERN ALASKA

By Max G. White

UNITED STATES DEPARTMENT OF THE INTERIOR 

Oscar L. Chapman, Secretary

GEOLOGICAL SURVEY 

W. E. Wrather, Director

GEOLOGICAL SURVEY CIRCULAR 185

RECONNAISSANCE FOR RADIOACTIVE DEPOSITS ALONG THE 

JPPER PORCUPINE AND LOWER COLEEN RIVERS, NORTHEASTERN ALASKA

By Max G. White

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., 1952

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

Page

Part 1. Reconnaissance along the upper

Porcupine River 

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

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

Location of area................... 1

Purpose and scope of 

investigation..................... 1

General geographic information..... 1

Previous geologic 

investigations.................... 1

Radioactivity reconnaissance 

in 1948.......................... 3

Geology and radioactivity 

investigations........................ 3

Sedimentary rocks.................. 3

Pre-Cambrian rocks........... 3

Radioactivity studies....... 3

Ordovician and Silurian 

strata....................... 5

Radioactivity studies....... 5

Silurian limestone and 

shale........................ 5

Radioactivity studies....... 5

Devonian rocks................. 6

Radioactivity studies..... i.. 6

Carboniferous limestone 

and shale.................... 6

Radioactivity studies....... 6

Tertiary sediments............ 6

Radioactivity studies....... 6

Quaternary alluvium........... 6

Radioactivity studies....... 6

Part 1. Reconnaissance along the upper

Porcupine River Continued 

Geology and radioactivity 

investigations- -Continued

Igneous rocks....................

Mesozoic( ?) granitic rocks..., 

Radioactivity studies.....

Radioactive minerals. 

Biotite..........

Clarkeite( ?).....

Hematite........

Pyrite..........

Rutile(?). .......

Unknown

mineral no. 1... 

Unknown

mineral no. 2.. 

Unknown

mineral no. 3... 

Tertiary lava flows...........

Summary of materials tested... .......

Conclusions................ .........

References cited. ...................

Part 2. Reconnaissance along the lower

Coleen River 

Abstract............................

Introduction.........................

Location of area.................

Purpose and scope of investigation 

Area investigated.................

Geology............... ..............

Lower Coleen River..............

Rabbit Mountain .................

Radioactivity investigations...........

Reference cited .....................

Page

ILLUSTRATIONS

Figure 1. Geologic sketch map of the upper Porcupine River, northeastern Alaska, showing location 

of samples collected in 1948. ......................................................

2. Sketch map of the Sunaghun Creek-upper Rapid River area, northeastern Alaska. .........

3. Geologic sketch map of the lower Coleen River, Alaska........ ........................

11

11

11

11

11

11

11

11

11

12

Page

2

4

13

TABLES

Table' 1. Data on heavier-than-bromoform fractions of concentrates from gravels of streams tributary 

to the upper Porcupine River, northeastern Alaska......................................

2. Data on samples related to the granitic intrusive on the international boundary north of the

Porcupine River, northeastern Alaska. ................................................

3. Radioactivity values for samples collected in Coleen River valley in 1948................... 12

iii
RECONNAISSANCE FOR RADIOACTIVE DEPOSITS ALONG THE 

UPPER PORCUPINE AND LOWER COLEEN RIVERS, NORTHEASTERN ALASKA

PART 1. RECONNAISSANCE ALONG THE UPPER PORCUPINE RIVER

ABSTRACT

The highest equivalent-uranium co'ntent found 

in the sedimentary rocks on the upper Porcupine 

River, northeastern Alaska, is 0.005 percent. 

Rhyolitic dikes associated with a granitic intrusive 

a few miles north of the Porcupine, along the international boundary, contain about 0.006 percent 

equivalent uranium, which is attributed to small 

amounts of disseminated radioactive accessory 

minerals. The granite also is slightly radioactive.

INTRODUCTION

LOCATION OF AREA

The Porcupine River, a major tributary of the 

Yukon River, is located in northeastern Alaska 

(fig. 1). It enters the Yukon from the northeast, 

near the town of Fort Yukon, a short distance north 

of the Arctic Circle. The upper two-thirds of the 

Porcupine River is in Yukon Territory, Canada. 

The river waters are navigable by medium-sized 

river boats and scows for 280 miles above its mouth. 

The river distance from the mouth of the Porcupine 

to Rampart House on the Alaska-Yukon boundary is 

about 215 miles. Only the area along the upper 80 

miles of the Alaskan part of the river, from Burnt 

Paw to Rampart House (fig. 1), was examined in 

detail in the course of this investigation.

PURPOSE AND SCOPE 

OF INVESTIGATION

In 1948 a Geological Survey field party carried 

on a radioactivity reconnaissance in the Porcupine 

River valley to obtain the following:

1) General information on possible radioactive 

deposits-.

2) Specific information on the content of radioactive material in black shale and other 

sedimentary rocks of pre-Cambrian and 

Paleozoic age.

3) Radio metric and geologic information on a 

granitic intrusive north of the Porcupine 

River valley along the international boundary.

No information on the occurrence of radioactive materials in the valley of the Porcupine River was available prior to the 1948 investigation. The period of 

field work extended from late in June to late in August and was carried on by a party consisting of

Max G. White, geologist; Arthur Wahl and Glenn E. 

Fellows, camp assistants; and Egil Salveson and 

Charlie Strom, boatmen.

This work was done on behalf of the Division 

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

GENERAL GEOGRAPHIC INFORMATION

The lower 100 miles of the Porcupine River 

crosses a broad flat alluvium-filled basin called the 

Yukon Flats. Many meanders and sloughs make the 

channel very tortuous and in places difficult to follow. The lowest exposure of bedrock, a bluff called 

Graphite Point, is 100 miles above the river's mouth.

Between Graphite Point and the mouth of the 

Coleen River (fig. 1), about 30 miles farther upstream, the Porcupine has cut its course through 

rocks that are principally limestone. The cliffs 

along this part of the river are 60 to 75 ft high and 

are known locally as the "Lower Ramparts". From 

the mouth of the Coleen River to Red Gate (fig. 1) 

the Porcupine occupies a wide meander loop across 

a small basin. This basin is filled partly with 

Quaternary alluvium and partly with gravels of 

Tertiary age. Red Gate is a high, dark-reddish 

cliff, which rises- abruptly above the river to a 

height of 300 ft and marks the entrance to the "Upper 

Ramparts", where, for 52 miles, from Red Gate to 

12 miles east of the international boundary, the 

Porcupine has cut a nearly continuous canyon 250 to 

300 ft deep; locally the cliffs rise 500 ft above the 

valley floor.

For further information on this region, both 

geographic and historic, the reader is directed to 

Fitzgerald's report (1944)1 on a general topographic 

reconnaissance of the Porcupine River valley.

PREVIOUS GEOLOGIC INVESTIGATIONS

Four geologic investigations (Kindle, 1908; 

Maddren, 1912a, 1912b; Cairnes, 1914; and Mertie, 

1941) have been made of the rocks along the 

Porcupine River and along the international boundary in northeastern Alaska.

Kindle's observations were made in 1906 

during a three weeks' round trip by canoe from Fort 

Yukon to Rampart House. His paper includes a 

geologic map of the rocks adjacent to the Porcupine 

River from the Lower Rampart to the international 

boundary.

lSee reference cited.
\NDEX MAP OF NORTHEASTERN ALASKA

Tract Elements field work by M. G. White, 1

Figure 1. --Geologic sketch map of the upper Porcupine River, northeastern Alaska, showing location of samples

collected in 1948.
In 1911 and 1912 Maddren accompanied 

the International Boundary Survey, mapping the 

geology of a strip 4 miles wide straddling the 

boundary from the Porcupine River north to 

the Arctic Coast. The results of his 1911 field 

work (Maddren, 1912a), the study of the Porcupine-Firth River sector, were published without a map. Notes and maps for the area 

north of the Firth remain unpublished in the 

Geological Survey files (Maddren, 1912b).

Cairnes' studies along the international 

boundary south of the Porcupine River paralleled 

the work of Maddren. The final published report includes geologic strip maps of the boundary from the Porcupine south to the Yukon 

River (Cairnes, 1914).

Mertie (1941, unpublished) conducted a 

geologic investigation on the Porcupine River in 

1941 (manuscript notes and maps in files of 

U. S. Geological Survey).

RADIOACTIVITY 

RECONNAISSANCE IN 1948

Geologic data and maps from the investigations described above served as the basis 

for the radioactivity reconnaissance in 1948. 

Much of this reconnaissance consisted in radiometric tests on outcrops of Silurian, Devonian, 

and Carboniferous black shale. All the preCambrian rocks were also examined in some 

detail. Concentrates were taken from the 

gravels of most of the streams entering the 

Porcupine, as a check on the possible presence 

of radioactive materials in the areas drained 

by these streams. A granite mass along the 

international boundary 6 to 23 miles north of 

the Porcupine was investigated both radiometrically 

and geologically. Very little previous information was available about this intrusive.

The geologic maps in this report are 

modifications and expansions of maps already 

in existence. Figure 1 is modified from a 

map by Kindle (1908, p. 321), and figure 2 

from one by Maddren (1912b).

Portable survey meters with conventional 

low-count beta-gamma tubes were used for 

field radioactivity measurements. Continuous 

radiometric traverses were made on foot along 

most of the outcrops of the various rock types. 

Where counting rates seemed appreciably higher 

than background, stationary counts were taken 

on the outcrops and significant samples were 

taken. These samples were crushed and tested 

in the field with either a standard portable survey meter or a modified counter designed by 

U. S. Geological Survey. Representative samples from outcrops that showed the presence of 

radioactive material were examined in the laboratory for a final check on the field results.

GEOLOGY AND RADIOACTIVITY INVESTIGATIONS

Brief descriptions of the rocks of the geologic systems present in the upper Porcupine 

area are given below. Radioactivity studies, 

where made, are included with the separate 

descriptions.

SEDIMENTARY ROCKS 

Pre-Cambrian rocks

The oldest rocks on the Porcupine River 

are those on the upper 6 miles of the river 

in Alaska, near the international boundary. 

Cairnes (1914, pp. 44-58) assigned them to 

the pre-Cambrian (actually pre-Middle Cambrian) 

and correlates them with the Tindir group 

farther south along the boundary. Mertie (1932, 

pp. 369-392) presents an excellent description 

of the Tindir group in the area of its type 

locality.

The Tindir group on the Porcupine River 

consists of quartzite, usually light gray, some 

sandstone and siltstone, and bedded dolomite 

and shale. Most of this shale is black, but 

some red and yellow beds also are present. 

The quartzite is apparently more abundant in 

the upper and lower parts of the sequence than 

in the middle. The quartzite forms the cliffs 

300 to 500 ft high in the vicinity of Rampart 

House. Weathering of the exposed surfaces 

of the quartzite gives this rock the appearance 

of massive chalky limestone. The more protected surfaces, however, are usually covered 

with a light-yellow film of sulfur that has 

accumulated from the oxidation of pyrite disseminated in the quartzite.

The sandstone and siltstone, interbedded 

in the quartzite, commonly are highly ferruginous, deep chocolate to yellow, and have 

brown spots due to weathering of enclosed 

iron sulfide. The dolomite and black shale 

each account for approximately 25 percent of 

the total sequence. The dolomite is cream 

to white and very dense; the black shale in 

places is highly contorted between the more 

competent beds of quartzite and dolomite and 

locally exhibits a slaty cleavage.

No evidence of significant faulting or 

folding was observed in the rocks of the Tindir 

group, which have a prevailing westerly dip 

of about 40°. A conservative estimate of the 

stratigraphic thickness of this group along the 

upper Porcupine River is 18,000 ft.

Radioactivity studies

Radiometric readings were taken on outcrops in all traverses of the pre-Cambrian
EXPLANATION

SEDIMENTARY ROCKS

Stream Concentrate Sample Location

S-41

Trace Elements field work by M.G. White, 1948

Figure 2. --Sketch map of the Sunaghun Creek-upper Rapid River area, northeastern Alaska.

4
sedimentary rocks. Data on samples collected 

from locations with relatively high field readings are listed below. The sample localities 

are shown on figure 2.

Sample no

S-38 

S-39 

S-40 

S-41 

S-42

S-43 

S-44

S-45 

S-46 

S-51

S-52

Rock type and location 

Black slate, Sunaghun Creek 

do

do 

do

Black shale, Porcupine River below Rampart 

House.

 _ do 

Black shale, Porcupine River in vicinity of 

Fred Creek.

 do - 

 do 

Red shale, Porcupine River below Rampart

House . 

Yellowish Shale, Porcupine River below

Rampart House.

eUx content 

(percent)

0.004

.002

.002

.002

.003

.003

.003

.002

.001

.004

.005

^-eU, equivalent uranium

In 1947 the Geological Survey received some 

samples of radioactive calcareous siltstone or 

argillite of pre-Cambrian age from Great Slave 

Lake, Northwest Territories, Canada. Chemical 

analyses of the rock (Rabbitt, 1947) show the presence of 0.17 percent thorium oxide and 0.006 percent uranium. According to Lang (1950, p. 9) monazite and pitchblende or uraninite have been identified 

in these rocks. He also adds that these minerals 

are probably original constituents of the rocks. The 

lithologic similarity of the pre-Cambrian sedimentary 

rocks at Great Slave Lake (Stockwell, 1936) to the 

pre-Cambrian Tindir group on the international 

boundary (Cairnes, 1914; Mertie, 1932) led to the 

search for similar thorium-bearing strata in the 

course of this reconnaissance of radioactive materials. 

The search, however, disclosed no significantly 

radioactive rock of any type in the pre-Cambrian 

sequence.

Ordovician and Silurian strata

least several thousand feet thick, are buff and bluishgray dolomite and limestone.

Radioactivity studies

The Ordovician and Silurian carbonate rocks 

were tested only hastily with a standard portable survey meter traverse on the way downstream at the 

end of the field season. These rocks appear to be 

essentially nonradioactive.

Silurian limestone and shale

Kindle (1908, p. 332) states that the section 

Of rocks immediately overlying the pre-Cambrian 

6 to 10 miles downstream from Rampart House 

probably contain rocks of both Ordovician and 

Silurian age, but he was unable to separate the two 

systems. Cairnes (1914, pp. 55, 59) found Middle 

Cambrian fossils in rocks, believed to be no older 

than Ordovician, that overlie the Tindir group in its 

type area. He also states that the strata overlying 

the pre-Cambrian range in age from Cambrian to 

Silurian. As Kindle's geologic map was used as a 

base in this reconnaissance, his designation of these 

strata as Ordovician and Silurian is used in this 

report. These Ordovician and Silurian rocks, at

The Silurian strata along the Porcupine River 

comprise about 3,000 ft of magnesian limestone or 

dolomite, mostly on the lower part of the river, and 

were not examined in this reconnaissance. At the 

top of the Silurian, within the area of the upper part 

of the river, is a small amount of black shale which 

was examined at two places, one 3 miles above Burnt 

Paw and the other about 1 mile above Old Rampart 

(fig. 1).

Radioactivity studies

Above Burnt Paw (fig. 1) black- and chocolatecolored fissile shale is interbedded with thin layers 

of dolomitic limestone and a few thin layers of sandstone. The highest radiometric readings recorded 

in the field were obtained on outcrops of this shale. 

About 1 mile above Old Rampart (fig. 1) approximately 

300 ft of black graptolitic fissile shale with a few thin 

beds of black limestone were also tested for 

radioactivity. The equivalent-uranium content of 

Silurian black shale samples collected above Burnt 

Paw and near Old Rampart is as follows:

eU content 

Sample no. Rock type and location (percent)

S-15 Black shale interbedded with limestone, 0.005

about 3 miles upstream from Burnt Paw. S_l6 do .005 

S-17 do .000 

S-18 do .002 

S_19 do .001 

S_2Q do .002 

S-33 Black graptolitic shale, about 1 mile up

stream from Old Rampart. .003 

S_34 do .003
Devonian rocks

The Devonian rocks along the upper Porcupine 

River (fig. 1) consist of siliceous limestone; black, 

brown, gray and red shale; and a small amount of 

interbedded basalt.

Radioactivity studies

The Devonian shale at the mouth of the Rapid 

River (fig. 1) was traversed radiometrically but 

proved barren of significantly radioactive beds. 

Samples of black shale (nos. S-35 and S-36, fig. 1) 

from two beds with the highest field readings contain only 0. 002 percent equivalent uranium. The 

basalt and siliceous limestone are nonradioactive.

Carboniferous limestone and shale

The Carboniferous strata exposed on the upper 

Porcupine River (fig. 1) are interbedded limestone

and shale. Some of the limestone beds are grayto cream-colored, somewhat massive, and contain 

some chert; some are bluish-black to gray, and, 

locally, fissile or slaty, calcareous or sandy, or 

graphitic. Although no estimate of the thickness of 

the Carboniferous rocks has been made because 

these beds usually have been highly disturbed, the 

Carboniferous section doubtless includes many 

hundreds of feet of sedimentary beds.

Radioactivity studies

Radiometric traverses on foot along all exposures of Carboniferous rocks on the upper Porcupine disclosed no beds of shale or other rock 

that contained more than 0.003 percent equivalent 

uranium. The equivalent-uranium values of samples 

taken from Carboniferous strata showing the 

greatest radioactivity on the outcrop are listed 

below.

eU content 

Sample no. Rock type and location (percent)

S-21 Black shale, at east side of mouth of 0.005

Coleen River. 

S-23 Black shale, north side of Porcupine River .003

upstream from Coleen River.

S_24 do .001 

S _25 do .001 

S-26 Black shale, south side of Porcupine River .002

downstream from Salmontrout River.

S_27 do .002 

S_28 do .002 

S_29 do .002 

S_50 do ' .002 

S-31 Black shale, north side of Porcupine River .003

opposite mouth of Salmontrout River.

S_52 do .003 

S-62 Black shale, north side of Porcupine River .003

opposite mouth of Coleen River.

Tertiary sediments

A wide belt of Tertiary sediments between 

Fish Creek and Red Gate (fig. 1) is comprised of 

about 40 ft of sand, gravel, and drab clay with 6- 

to 10-in. beds of low-grade lignite; underlain by 

50 ft of soft, finely laminated, drab-colored clay. 

Similar beds occur on the north bank of the Porcupine River below the Coleen River.

Radioactivity studies

Several of the lignite beds, cropping out 

between Fish Creek and Red Gate and below the 

mouth of the Coleen River, were tested radiometrically in the field and found to be nonradioactive.

Quaternary alluvium

Concentrates were taken from gravels (Quaternary alluvium) of streams draining into the 

Porcupine River in an attempt to determine whether 

heavy radioactive minerals were being eroded from 

rocks in the watersheds of those streams. The 

locations of such concentrates are plotted on figures 1 

and 2. Between 40 and 100 Ib of stream gravels at

each location were panned to semiconcentrates in 

the field. Such semiconcentrates were further concentrated in the laboratory by the use of bromoform 

(sp gr 2.8).

Radioactivity studies

The equivalent-uranium content of the heavierthan-bromoform mineral fractions of the semiconcentrates of the stream gravels was determined 

radiometrically in the laboratory. No significant 

amounts of radioactive material were detected in 

any of these heavy-mineral fractions. Data on these 

samples are shown in table 1.

IGNEOUS ROCKS

Two main types of igneous rock are found in 

the Porcupine River area. One type is a granitic 

intrusive of Mesozoic(?) age, which occurs along 

the international boundary 6 to 23 miles north of the 

Porcupine (figs. 1 and 2); the other type consists 

of lava flows of Tertiary age which form the bulk of 

the Upper Ramparts of the Porcupine River from 

Howling Dog Creek northeastward to a point 10 miles 

west of the international boundary (fig. 1).
Mesozoic(?) granitic rocks

The Mesozoic(?) granitic body north of the 

Porcupine River was first located by the International Boundary Survey in 1911 (Maddren, 1912a).

This body is the westward extension of a large 

granite mass in the Old Crow Mountains of 

Canada, and intrudes pre-Cambrian sedimentary 

rocks consisting mainly of quartzite and black 

shale.

Table 1. Data on heavier-than-bromoform fractions of concentrates from gravels of streams tributary to the upper Porcupine River, northeastern Alaska

Field no. 

(see fig. 1 

and 2)

48AWe63

1?80

84

85

87

129

130

131

132

133

135

j._po

137

139

141

170

171

172

174

177

178

200

ATE 

file no.

3178

3177

3179

3180

3181

3182

31§3

3184 -3-1 QC

^iftR

-3-1 Qr^

 3*1 QD

JlOO 3189 3190 3191 3192 3193 3205

3204

3203

3202

3201

3200

3199

Location

David Creek.

Howling Dog Creek.

Rapid River.

White Mountain Creek.

Campbell River.

Sunaghun Creek, near mouth.

Sunaghun Creek, lower part.

j /"l

j /"i

H

j _

,

Sunaghun Creek, lower part.

_ _ __ -. _ r\r\ ___ -. -

J

Sunaghun Creek, middle part.

 do 

First south tributary of Porcupine

River below Rampart House.

Second south tributary of

Porcupine River below Rampart

House .

Third south tributary of

Porcupine River below Rampart

House .

First north tributary of

Porcupine River above third

south tributary (sample 172)

below Rampart House.

North tributary of Porcupine

River opposite mouth of Fred

Creek.

Fred Creek.

North tributary of Porcupine 

River about l£ miles below

Fred Creek.

eU content 

(percent)

0.000

.000

.000

.000

.000

.003

.002

.002

.002

.000

.000

(1)

.001 (*)

.001

OO^ !oo6

.005

.000

.001

.003

.000

.006

Concentration 

ratio

2,300:1

1,600:1

3,400:1

1,200:1

1,000:1

600:1

1,300:1

3,000:1

800 :1

650:1

300:1

7,600:1

7

700:1

800:1

1,100:1

2,400:1

500:1

3,800:1

1,100:1

1,300:1

850:1

-' Sample too small for determination of eU content.

Within the area examined (fig. 2), the granite 

is medium- to coarse-grained, and contains small 

amounts of biotite and hornblende and very small 

amounts of the accessories apatite, zircon, and 

magnetite. Most of the orthoclase feldspar and much 

of the biotite in the granite have been partly replaced 

by minute sericitic aggregates.

Rhyolitic dikes, locally aplitic in texture, appear 

on the borders of the granite, cutting into the preCambrian sedimentary rocks. The largest of these 

dikes observed is at the head of White Mountain Creek 

(fig. 2).

Field evidence indicates that the granite mass 

underlies the thick covering of Tertiary lava flows 

that appears a few miles to the west. The granite 

contact probably veers gradually to the north and

then northeast, to cross the international boundary at a point approximately 23 miles north 

of the Porcupine River.

The age of the granite is not yet known, 

but it is thought to be younger than Carboniferous and older than Tertiary, and therefore 

Mesozoic(?).

Radioactivity studies

Although the granitic rocks in the upper Porcupine area contain minor amounts of radioactive 

materials, no zones of high concentrations were 

found. The rhyolitic rocks are slightly more 

radioactive than the coarser-grained phases of 

the granite. Consequently, the field studies were
extended to all borders of the granite where the 

rhyolitic dikes are located. The equivalent uranium

content and other data of all samples collected by the 

author in the area of the granite are shown in table 2.

Table 2. Data oh samples related to the granitic intrusive on the international boundary north

of the Porcupine River, northeastern Alaska

Field no. 

(see fig. 2)

48AWe89

90

99

100

101

107

108

111

112

117

ATE file 

no.

3194

3195

3196

3217-L

3218-L

3219-L

3197

3220-L

-2pOT T jeLcLA. J_i 

3198

Description and 

location

Concentrate from stream gravels in

northeast headwaters fork of Sunaghun

Creek.

Concentrate from stream gravels in

Sunaghun Creek about ^ mile west of

international boundary.

Concentrate from disintegrated rhyolitic dike near Sunaghun Creek about

^ mile west of the international

boundary.

Crushed fragments of fresh rock from

spme locality as sample 48AWe99«

Crushed granite from ridge west of

Sunaghun Creek aboat £ mile west of

international boundary.

Crushed granite from highest point on

ridge about 2 miles west of international boundary.

Concentrate from stream gravels in

northwest headwater fork of Sunaghun

Creek.

Crushed rhyolitic rock from saddle

between Sunaghun and White Mountain

Creeks .

 do 

Concentrate from stream gravels in a

southeast tributary of the Rapid

River.

eU content

U rushed 

rock

_

-

-

0.006

.003

.003

-

.006

.006

(percent)

Heavy -mineral 

fraction l

0.045

.016

.060

.030

.004

.009

.010

.002

.035

.052

Concentration 

ratio

3,500:1

8,200:1

2,000:1

450: 1

6:1

6:1

1,000:1

10:1

Qcr -i 05:1

2,700:1

-'-Fraction heavier than bromoform (sp gr 2.8).

Radioactive minerals

Z. S. Altschuler and T. W. Stern of the Geological Survey's Trace Elements Laboratory examined 

six moderately radioactive samples (nos. 48AWe89, 

90, 99, 100, 108 and 117, fig. 2 and table 2) from the 

granitic rock area on the international boundary in an 

attempt to determine which mineral cause the radioactivity. Subsequently the author examined a seventh 

sample (48AWell2, fig. 2 and table 2) for the same 

purpose. The radioactive minerals found in these 

samples are as follows:

Biotite. --The radioactivity of sample 48AWell2 

is restricted to the biotite part of the heavy-mineral 

fraction. The sample is from a large rhyolitic dike 

at the head of White Mountain Creek (fig. 2).

Clarkeite( ?). --Reddish-brown uraniferous grains, 

tentatively identified as clarkeite (1103. nH^O) by its 

optical properties, appears to be the only radioactive 

mineral in sample 48AWe89.

Hematite. --The hematite in sample 48AWe99 is 

reported to contain some uranium as an impurity.

Pyrite. Fluoresence tests of the heavy minerals 

in sample 48AWelOO indicate that pyrite grains, which 

are oxidized and altered although euhedral, are radioactive, mostly on the surfaces and in minute fractures 

within the grains. Crushed fragments show minute 

amounts of quartz and another material within the 

fractures. Fluorimetric analysis shows the presence 

of 0.027 percent uranium. Whole grains of pyrite 

were used in this analysis. A second fluoresence 

test made on crushed grains disclosed no uranium, 

bearing out the hypothesis that the uranium is only 

in the surficial, weathered part of the pyrite.

Rutile(?). Fluoresence tests indicate that 

material tentatively identified as altered rutile(?) is 

probably the only uranium-bearing mineral in sample 

48AWell7. This mineral, however, is too altered 

and heterogeneous to yield a good X-ray pattern. It 

is called altered rutile(?) on the basis of an incomplete 

spectrographic determination. Optically, however, 

it resembles eschynite.

Unknown mineral no. 1. A mineral, herein 

1' designated "Unknown mineral no. 1", contains most 

of the radioactive material in the heavy-mineral 

fraction of sample 48AWe99. Identification of this 

mineral by optical or X-ray methods appears to be 

impossible. It is probably hexagonal, although 

pseudo-orthorhombic in appearance, and is orange 

and translucent with a dull 1'uster. In addition to 

uranium, this mineral contains calcium and phosphorus.
Unknown mineral no. 2. The only radioactive 

mineral in sample 48AWe90 has not yet been identified. For the purpose of this report it is called 

"Unknown mineral no. 2". This altered mineral 

contains iron, titanium, aluminum, and silicon as 

determined by spectrographic analysis, and uranium 

by fluoresence test.

Unknown mineral no. 3. - - Unknown mineral 

no. 3 apparently is the only uranium-bearing mineral 

in sample 48AWel08. It is black and opaque, and 

spectrographic analysis indicates that its major constituents are iron, manganese, aluminum, and silicon.

Tertiary lava flows

Tertiary lava flows, which form the bulk of 

the Upper Rampart, extend from 10 miles west of 

the international boundary westward to Howling Dog 

Creek. The flows are over 300 ft thick and are exposed in the steep cliffs that rise abruptly from river 

level. At one place above Old Rampart there are at 

least 15 different flows distinguishable in the canyon 

wall. The lava rests on a very irregular surface of 

Paleozoic rocks. Exposures of Paleozoic rocks such 

as those at the mouths of Rapid and Campbell Rivers 

represent localities on the pre-lava erosion surface 

that were of sufficient relief to be only thinly covered, 

if at all, by the flows. Tests of the Tertiary lava 

flows showed them to be nonradioactive.

SUMMARY OF MATERIALS TESTED

Shale, granitic rock, and concentrates from 

gravels of streams draining areas of granitic rocks 

are the only materials tested in the reconnaissance 

of the Porcupine River area that contained at least 

minor amounts of radioactive material. The search 

did not reveal any deposit that would be considered 

a commercial source of uranium ore. A summary 

of the results for the material tested is shown in 

the table on page 10.

CONCLUSIONS

Although this reconnaissance disclosed the presence of minor amounts of radioactive materials

associated with shale beds of pre-Cambrian and 

Paleozoic age, and Mesozoic(?) granitic rocks, the 

equivalent-uranium contents are not of sufficient 

significance to warrant additional study. It is probable 

that the Porcupine River area described in this report does not contain deposits that can be considered 

as a commercial source of uranium.

REFERENCES CITED

Cairnes, D, D., 1914, The Yukon-Alaska international boundary, between Porcupine and Yukon 

Rivers- Canada Geol. Survey Mem. 67, 161 pp.

Fitzgerald, Gerald, 1944, Reconnaissance of Porcupine Valley, Alaska: U. S. Geol. Survey Bull. 

933-D, pp.219-243.

Kindle, E. M., 1908, Geologic reconnaissance of 

the Porcupine Valley, Alaska: Geol. Soc. America 

Bull. vol. 19, pp. 315-338.

Lang, A. N., 1950, Summary account of Canadian 

uranium deposits: Canada Geol. Survey mimeographed report.

Maddren, A. G., 1912a, Geologic investigations 

along the Canada-Alaska boundary: U. S. Geol. 

Survey Bull. 520-K, pp. 297-314.

___________ 1912b, (Unpublished notes and maps 

of surveys along the international boundary north 

of the Porcupine River, in files of U. S. Geol. 

Survey).

Mertie, J. B., Jr., 1932, The Tatonduk-Nation 

district (Alaska): U. S. Geol. Survey Bull. 836-E, 

pp. 347-443.

____________ 1941, (Unpublished notes and 

maps of surveys along the Porcupine River, Alaska, 

in files of U. S. Geol. Survey).

Rabbitt, J. C., 1947, Interim report on thoriumbearing limestone from Great Slave Lake, Canada: 

U. S. Geol. Survey Trace Elements Memorandum 

Rept. 50 (unpublished).

Stockwell, C. H., 1936, Preliminary geological map 

of Great Slave Lake, east arm (east and west sheets), 

Northwest Territories: Canada Geol. Survey Paper 

' 36-16.
Summary of results for materials tested

Rock types and age of 

material tested

Radioactivity 

(values given are 

in percent eU)

Sedimentary and other bedded rocks:

Pre-Cambrian (Tindir group) 

Quartzite 

Dolomite 

Black shale 

Red shale 

Yellow shale

Ordovician and Silurian

Dolomite and limestone

Silurian

Magnesian limestone (dolomite) 

Black shale (above Burnt Paw) 

Black shale (above Old Rampart)

Devonian

Black shale

Basalt

Siliceous limestone

Carboniferous

Black shale 

Limestone

Tertiary

Lignite

Igneous rocks:

Mesozoic(?)

Medium- to coarse-grained granite 

Unconcentrated 

Heavy-mineral fractions

Rhyolite dike rock 

Unc once ntrated 

Heavy-mineral fractions

Tertiary 

Lava

Heavy-mineral concentrates from stream gravels:

From gravels of Porcupine River tributaries 

which drain areas underlain mostly by 

sedimentary strata and basaltic rocks

From gravels of streams draining area of 

granitic rocks along the international 

boundary

0.001-0.004 *

.004 

.005

.000-0.005

.003

.002

.001-0.003

.003 

.004-0.009

.006 

.002-0.060

0.000-0.006

.010-0.052

LNonradioactive.

10
PART 2. RECONNAISSANCE ALONG THE LOWER COLEEN RIVER

ABSTRACT GEOLOGY

The highest radioactivity value obtained in 

a traverse of shales in the middle Paleozoic 

strata of the lower Coleen River is 0.003 percent equivalent uranium. Traverses on preCambrian schists at Rabbit Mountain were made 

with negative results.

INTRODUCTION

LOCATION OF AREA

The Coleen River, a northern tributary 

of the Porcupine River, heads in the Brooks 

Range of northern Alaska and enters the. Porcupine River about 50 miles in an airline west 

of the Alaska-Yukon boundary. (See inset, 

fig. 3.)

PURPOSE AND SCOPE 

OF INVESTIGATION

During the Porcupine River investigation 

in 1948 (see part 1) a 10-day side trip was 

made up the Coleen River to investigate reported outcrops of sedimentary rocks. A 

party of four men ascended the river to a 

point 75 miles above its mouth, where J. E. 

Owens, the only inhabitant of the valley, maintains a permanent residence. This area had 

never before been explored by the Geological 

Survey.

This work was done on behalf of the 

Division of Raw Materials of the U. S. Atomic 

Energy Commission.

AREA INVESTIGATED

All exposures along the river from J. E. 

Owens' camp to the mouth of the Coleen River 

were tested for radioactivity, and most of them 

were sampled. In addition, measurements of 

radioactivity were made on the slopes of 

Rabbit Mountain, 15 miles east of Owens' camp. 

Radioactivity values of all samples collected 

during this investigation are recorded in table 3.

This investigation should be considered a geological exploration-reconnaissance pf the lower 

Coleen River, as no geological information was 

available from the area prior to this investigation. 4

LOWER COLEEN RIVER

No attempt was made to measure any stratigraphic sections or to make any detailed geological studies or maps---all effort was directed 

solely to the detection of possible radioactive 

deposits.

The rocks on the lower Coleen River consist of a series of gray, black, and red shales, 

slate with some limestone and siltstone, and an 

abundance of light-gray chert in, beds up to 

20 ft thick. Dikes and sills of basic igneous 

rock are found throughout the series. There 

is a distinct similarity between the rocks on 

the Coleen River and those to the west in the 

Sheenjek River valley, which Mertie (1929, 

p. 119) tentatively classified as "Devonian or 

Carboniferous".

As no attempt was made at geologic mapping, figure 3 merely shows the locations of 

most of the outcrops that were tested and from 

which samples were collected.

RABBIT MOUNTAIN

Two and a half days were spent investigating Rabbit Mountain, about 15 miles east of 

Owens' camp. This mountain had been locally 

reported to be a mass of granite, but traverses 

along most of its northwest side showed it is 

composed of schist .and slate, similar to the 

pre-Cambrian rocks along the international boundary, about 30 miles east of Rabbit Mountain. 

No mineralization was found associated with two 

granite dikes that intrude the schist.

RADIOACTIVITY INVESTIGATIONS

Foot traverses with portable survey meters 

were made along all accessible exposures of bed11
rock and talus on the Coleen River and at Rabbit Mountain. 

No significant radioactivity was detected anywhere.

The samples listed in table 3 are those brought back 

to the laboratory for a final, conclusive check.

Table J>.--Radioactivity values for samples collected in Coleen River valley in 1948.

Pile 

no.

S-l

*

S-2

S

-2

S 4

o c

s-6

S-7

a Q

<S Q

S

-i n

C3 -| T

S n o

S-13 

S-14

S-22 

3176

Field 

no. 

(48AWe)

1 

2(1) 

2(2)

I?

?6 

17

1

Q

19r\s\

23

29 

31

44 

43

Location and description

Black shale cut by basic dikes 

in section below Owens' camp. 

Black shale in section on Coleen 

River below Owens' camp.

rtn - - _ -

 do -

 do 

Black shale from section on Coleen 3 miles airline below Owens' 

camp.

 do 

- ^ _ r*n -«--- ______

Black shale 3^ miles airline 

above Porcupine River.

(^Q __ __ _____ __

Black shale, Coleen River, donated 

by J. E. Owens. 

Stream concentrate from Rabbit 

Mountain .

Percent equivalent uranium 

in crushed rock

0.002 

.002 

.002

.002

.002

.000

.002 

nn~^

A/-^O

.002

.002

.002

.003 

.003

.000 

*.001

*Heavier-than-bromoform mineral fraction.

According to J. E. Owens, the Aluminum 

Company of America reports the presence of more 

than trace amounts of gallium in material from the 

Coleen River area, which he had submitted for 

spectrographic analysis.

REFERENCE CITED

Mertie, J. B., Jr., 1929, The Chandalar-Sheenjek 

district (Alaska): U. S. Geol. Survey Bull. 810-B, 

pp. 87-139.

12
EXPLANATION

S-22»

Sample locality

Figure 3. --Geologic sketch map of the lower Coleen River, Alaska.

13 INT.-DUP. SBC.. WASH., D.C. 22132