Geochemical Reconnaissance 

In the Wiseman and Chandalar 

Districts and Adjacent Region, 

Southern Brooks Range, Alaska 

GEOLOGICAL SURVEY PROFESSIONAL PAPER 709 

Geochemical Reconnaissance 

In the Wiseman and Chandalar 

Districts and Adjacent Region, 

Southern Brooks Range, Alaska 

By W. P. BROSGE and H. N. REISER 

GEOLOGICAL SURVEY PROFESSIONAL PAPER 709 

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1972 
UNITED STATES DEPARTMENT OF THE INTERIOR 

ROGERS C. B. MORTON, Secretary 

GEOLOGICAL SURVEY 

V. E. McKelvey, Director 

Library of Congress catalog-card No. 72-189156 

For sale by the Superintendent of Documents, U.S. Government Printing Office 

Washington, D.C. 20402- Price 40 cents (paper cover) 
CONTENTS 

Page 

Abstract _________________________________ ---·-------- _____ --------------- _____ 1 

Introduction _______ -··- ___________________ --·----------------------------------- 1 

Geologic Setting ______________________________ --------------------------------- 1 

Mining history _________________________________ ------------------------------ 3 

Placer-gold sources ------------------------------------------------------- 3 

Geochemical sampling ----------------------------·---------------------------- 3 

Discussion of anomalous areas -------------------·---------------------------- 8 

Wiseman district -------------------------------------------------------- 8 

Chandalar mining area ______________________ ----------------------------- 13 

Other metal occurrences in the Chandalar area ---------------------·----- 16 

Other anomalous areas --------------------------------------------------- 19 

Summary -------------------------------------------------------------------- 20 

References cited -------------------------------·------------------------------ 20 

ILLUSTRATIONS 

Page 

FIGURE 1. Index map of Alaska showing location of Wiseman and Chandalar quadrangles and of areas of figures 2, 

4, and 9 ----------------------------------------------------------------------------------------- 2 

2. Map showing stream-sediment sample localities and generalized geologic map --------------------------- 4 

3. Map showing gold in stream-sediment, rock, and soil samples from Wiseman-Chandalar region _______ 6 

4-8. Map of the Nolan-Hammond River area showing4. Sample localities and unconsolidated deposits -------------------------------------------------- 9 

5. Gold in stream-sediment, rock, and soil samples ------------------------------------------·------ 10 

6. Arsenic and antimony in stream-sediment, rock, and soil samples -----------------------·------ 11 

7. Anomalous concentrations of antimony in stream-sediment samples in and near the Nolan-Hammond River area ___________________ ·-- ____________________________________________ --------- 12 

8. Silver and zinc in stream-sediment, rock, and soil samples ------------------------------------- 13 

9-12. Map of the Chandalar area showing -

9. Sample localities and geologic map -----·------------------------------------------------------ 14 

10. Gold, silver, molybdenum, arsenic, antimony, lead, and zinc in rock, soil, and stream-sediment 

samples near gold deposits ---------------------------------------------------------------- 15 

11. Gold and silver in stream-sediment, rock, and soil samples ------------------------------------ 16 

12. Zinc, lead, arsenic, antimony, copper, and molybdenum in stream-sediment, rock, and soil samples_ 17 

13. Map showing silver and lead in stream-sediment samples and silver in rock and soil samples from the 

Wiseman-Chandalar region -----------------·-------------------------------------------------------- 18 

III 

GEOCHEMICAL RECO~NAISSANCE IN THE WISEMAN AND CHANDALAR DISTRICTS AND 

AD:JACENT REGION, SOUTHERN BROOKS RANGE, ALASKA 

By W. P. BROSGE and H. N. REISER 

ABSTRACT 

Reconnaissance geochemical sampling in the WisemanChandalar region shows that gold and silver anomalies are 

usually accompanied by base-metal anomalies and occur in 

three areas-the Wiseman mining district, the Chandalar 

mining district, and an unexplored zone in carbonate rocks 

north of the mining districts. The preservation of gold 

placers in mountain valleys least affected by glaciation suggests a local bedrock source of gold. Near Wiseman, detailed 

sampling in the apparent source area of the richest gold 

placers shows that gold occurs in small veins of quartz and 

quartz-stibnite. The highest gold content found in the stibnite 

veins is 9.2 ppm, and in the quartz veins 5.8 ppm. In the 

Chandalar district, gold and base metals are concentrated 

in an area of northwest-trending shear zones. The known 

gold lodes are in these shear zones; gold also occurs along 

extensions of one and possibly two of the shear zones a 

mile or more west of the lode mines. In both the Chandalar 

and the Wiseman areas, arsenic is a good pathfinder for 

gold, and zinc is associated with the highest concentrations 

of gold and silver. 

INTRODUCTION 

Placer deposits near Wiseman and Chandalar 

have yielded nearly 300,000 ounces of gold. The 

Chandalar area (fig. 1) includes the only active 

lode-gold mining district in the Brooks Range. Although gold has been known from this region since 

before 1900, the geology is known mostly from 

reconnaissance studies, and the lode sources of 

many placer deposits, as well as the extent of the 

lode deposits, are still uncertain. As part of the investigation for heavy metals by the U.S. Geological 

Survey, samples were collected in 1967 to determine 

whether there is a lode-gold source near the placer 

deposits at Wiseman and whether the lode gold at 

Chandalar extends beyond the known deposits. 

Samples were also collected in the larger region 

around the two mining districts to help complete 

reconnaissance traverses across the southern Brooks 

Range in the Chandalar and eastern Wiseman quadrangles (fig. 2) begun during the geologic mapping 

in 1958-60 (Brosge and Reiser, 1960 and 1964). 

This regional sampling indicates that the principal 

gold mineralization is in the quartz-mica schist and 

phyllite of the two known mining areas and that 

silver mineralization may occur in carbonate rocks 

farther north. 

The geology, gold deposits, and mining history 

of the region were described by Schrader (1900), 

Maddren (1913), Mertie (1925), Reed (1938), 

White (1952), and Marshall (1933). Cobb's (1962 

and 1964) maps show locations of and give references for the individual lode and placer deposits. 

Chipp ( 1970) mapped and sampled the area around 

the Chandalar lode mines in detail and refined the 

stratigraphy shown by the regional mapping. 

Access to the mining areas is mostly by air. Dirt 

roads connect Nolan and the Hammond River mines 

with a landing strip for multiengine airplanes at 

Wiseman. A tractor road connects the Chandalar 

mines with a strip at Chandalar Lake, and the ice on 

Chandalar and Squaw Lakes furnishes a seasonal 

landing area. Strips for light planes give direct 

access to the Chandalar placer mines and to several 

of the mines along the Middle Fork of the Koyukuk. 

The access road for an oil pipeline planned along the 

Middle Fork and Dietrich Rivers would bring heavy 

equipment into the area from Fairbanks. 

During our work the miners helped us in many 

ways. For furnishing housing and transportation, 

we are especially grateful to Frank Birch and 

Wayne Adney of Chandalar, Andrew Miscovich of 

Porcupine Creek, and Smith Wanamaker and Harry 

Leonard of Wiseman. 

GEOLOGIC SETTING 

The southern flank of the Brooks Range, including the Chandalar and Wiseman districts, is underlain mainly by schist of Paleozoic age intruded by 

Mesozoic granitic rocks (figs. 1, 2). Paleozoic sedimentary rocks that lie immediately to the north of 

the granite and schist are mainly limestone and calcareous shale. A broad lowland south of the schist 

and granite is underlain by Paleozoic and Mesozoic 

1 
2 GEOCHEMICAL RECONNAISSANCE, SOUTHERN BROOKS RANGE, ALASKA 

170° 166° 

c R A. 

62° 

60° 

162° 

162° 158° 

T 

158° 154° 

0 

I 

50 

I 

154° 150° 

0 c 

150° 

100 MILES 

I 

146° 

E A N 

146° 

142° 138° 

\ 

~ 

\ 

70° 

\ 62° 

\ 

\ 

60° 

142° 

FIGURE 1.-Index map of Alaska showing location of Wiseman and Chandalar quadrangles. Areas of figures 2, 4, and 

9 are shown in relation to the areas of schist and granite and to the gold placers (black dots). 

phyllite and clastic rocks. Mafic intrusive and extrusive rocks occur in the phyllite and clastic rocks of 

this lowland and also in the schist and Paleozoic sedimentary rocks in the Brooks Range to the north. 

Glaciers of at least three advances have trenched 

and filled the main through-going valleys of the 

southern Brooks Range and have left the lowland 

south of the range largely covered by drift and 

outwash. Erratic boulders indicate that ice of an 

early advance overrode the lower mountains, whereas cirque glaciers occurred in the high mountains 

near the Brooks Range divide and in the southern 

part of the metamorphic belt. High alluvial terraces 

that probably are related to the two younger glacial 

advances extend up some of the major rivers and 

their tributaries. 

The relation of the various glacial advances to the 

gold placers is uncertain, but some of the placer 
GEOLOGIC SETTING 3 

deposits are older than at least the latest advance. 

Mertie ( 1925) described placers stratigraphically 

above and below the glacial deposits near Chandalar Lake, and deep placers near Nolan are buried 

by alluvium that is graded to the level of glacial 

fill in Wiseman Creek valley. 

MINING HISTORY 

Since 1899, when gold was discovered on the Middle Fork of the Koyukuk River, most of the Koyukuk's tributaries for a distance of about 35 miles 

from Gold Creek to Tramway Bar have produced 

placer gold. The greatest production was before 

1917; at present only a few one- or two-man opencut mines are in operation. The richest producers 

have been in the small area north of Wiseman 

shown in figure 2; there approximately 200,000-

250,000 ounces has been produced from Nolan 

Creek, the Hammond River, and their tributaries. 

Placer gold in these streams and the stibnite prospects in the small area between them suggest that 

lode-gold deposits also might be present. 

Placer-gold deposits in the Chandalar area are 

clustered around the known lode-gold deposits (fig. 

9). More than 29,000 ounces of placer gold has 

been produced since the discovery of gold deposits 

on Big Creek in 1906 (U.S. Bureau of Mines, written commun., 1968). Exploration of the gold-bearing 

quartz veins also began about this time. The known 

gold-bearing veins are in a narrow zone that extends about 3 miles northeastward across the strike 

of the country rock. Most exploration has been on 

the Mikado and Little Squaw lodes; the Mikado mine 

is now in production (Alaska Div. Mines Bull., 

1969). 

PLACER-GOLD SOURCES 

Most of the placer gold produced in the southern 

Brooks Range has been mined from deposits found 

in a belt of low rounded mountains and hills that 

trends westward along the northern limit of the 

schistose rocks from Big Lake through Wiseman 

to Wild Lake (figs. 1, 2). The parallelism of this 

placer belt with the regional strike suggests that 

the gold has a local source-in fact gold is found in 

the veins near Wiseman. The preservation of the 

older and deeper gold-bearing alluvial sediments 

within this bert of low hills may have resulted from 

the absence of local glaciers; the most recent glaciation there seems to have been restricted to the main 

valleys. 

Other shallow gold placers extend far upstream 

on creeks that rise in the higher mountains well 

within the area of schistose rocks, particularly on 

the cirque-free southern slopes. The gold in each of 

these probably comes from a local source in the 

schist, and a local source is evident at Chandalar, 

where the placers surround known gold lodes. 

Placer gold that occurs in the lowland south of 

the mountains may in part have been reworked from 

glacial drift of the Middle Fork of the Koyukuk 

(Reed, 1938). Glacial erratic boulders occur in the 

gold-bearing gravel deposits of a former high-level 

channel of the Middle Fork at Tramway Bar. Erratics also occur in placer deposits on the low pass 

between the Middle and South Forks (Reed, 1938), 

and the placers along the South Fork of the Koyukuk (just south of fig. 2) are directly below the 

mouths of former glacial spillways from the Middle 

Fork. 

GEOCHEMICAL SAMPLING 

Most of the 309 stream-sediment samples are of 

predominantly silt-size material. About half of these 

are from the two small areas of detailed sampling 

near Wiseman and Chandalar, and the other half 

from the regional reconnaissance. The regional 

samples were collected along a traverse across the 

sedimentary, volcanic, and metamorphic rocks in 

the upper Koyukuk area, and a traverse across the 

granitic rocks along the North Fork of the Chandalar. A few scattered samples were collected mainly 

from areas of metamorphic rocks. In addition, panned concentrates of stream gravel were collected 

along the North Fork of the Koyukuk. 

Most of the 207 samples of rocks and residual 

soils are grab samples collected on traverses across 

the known or suspected mineralized areas of Wiseman and Chandalar. Those samples collected outside 

the mining districts are from quartz veins and 

mineralized rock collected during regional mapping. 

The analyses and frequency-distribution statistics 

for all stream-sediment samples and the analyses of 

the rock and soil samples from the Wiseman and 

Chandalar districts have been placed on open file 

by the U.S. Geological Survey (Brosge and Reiser, 

1970a, b). The analyses by atomic absorption and 

colorimetric methods were done by H. H. Mehnert, 

J. B. McHugh, W. W. Janes, W. L. Campbell, J. 

Frisken, E. E. Martinez, R. L. Miller, K. R. Murphy, 

S. Rickard, T. A. Roemer, Z. Stephenson and R. 

Vaughn. The spectrographic analyses were made by 

M. DeValliere, A. Farley, Jr., E. E. Martinez, and 

Chris Heropoulos. 

The locations of samples with detectable gold and 

of those with high or anomalous concentrations of 

silver or some base metais are shown by maps 
4 GEOCHEMICAL RECONNAISSANCE, SOUTHERN BROOKS RANGE, ALASKA 

Base from U.S. Geological Survey 

W1seman and Chandalar 

1:250,000, 1956 

0 10 15 20 MILES 

FIGURE 2~Stream-sediment sample 
localities and generalized geologic map. 

SAMPLING 

14JOOO' 

Geology by W. P. Brosge, H. H. Reiser, C. L. Whittington, W. L. Nystrom, 1958 

W. P. Brosge, H. N. Reiser, J. 0. Berkland, D. F. Kellum, 1959 

W. P. Brosge. H. N. Re1ser, J. 0. Berkland, N. K. Hagen, 1960 

W. P. Brosge, H. N. Reiser. B. L. Hoffman, D. Biberdorf, 1967 

5 

EXPLANATION 

ROCK TYPES 

Unconsolidated deposits 

Granitic rocks 

Mafic volcanic rocks 

Greenstone and green schist 

Noncalcareous sedimentary rocks and phyllite 

Quartz-mica schist 

Albite-chlorite-mica schist 

Limestone, marble, calcareous schist, phyllite, and tactite 

Contact 

Appr·o.rimate; includes some 

faults 

• 

Stream-sediment 

sample locality 
6 GEOCHEMICAL RECONNAISSANCE, SOUTHERN BROOKS RANGE, ALASKA 

Base from U.S. Geological Survey 

Wiseman and Chandalar 

1:250,000, 1956 

0 5 10 15 20 MILES 

FIGURE 3.-Gold in stream-sediment, rock, and soil samples from Wiseman-Chandalar 
SAMPLING 

147"00' 

/ 

j 

l 

; \_~ 

~' ~"y I I ) ) .k- I 

region. For details near Wiseman and Chandalar, sec figm·cs 5 and 11. 

EXPLANATION 

Concentration of gold, in 

parts per million, in 

samples 

0 

Stream sediments 

~ 

0.02-0.039 

() 

0.04-0.049 

a 

0.05-0.059 

0.08-02 • 

None found 0.06-0.079 

0 

Rocks 

~ 0.02-.039 

~ 0.04-.079 

+ 

0.08-0.26 

0.8-18.0 • 

Value shown for concentrations greater 

than 1.0. Nonejound 

within range 0.27-0.79 

D 

Soil 

[) 

0.04-0.079 

Iii 

0.08-0.26 

Panned concentrates 

of gravel 

@ 

Concentration shown in 

parts per million 

For gold in rocks and 

soil near Wiseman 

and Chandalar see 

figs. 5 and 11 

Samples with gold in 

concentrations too 

small to be detected 

(Au <0.02 ppm) not 

shown 

Gold placer 

(From Reed, 1938} 

X 

Gold-placer mine active 

since 1955 

7 
8 GEOCHEMICAL RECONNAISSANCE, SOUTHERN BROOKS RANGE, ALASKA 

(figs. 3, 5-8, 10-13). The cutoff values for the concentrations described as anomalous or high are interpretive, but are at approximately the 971;2 and 

95th percentile levels of the continuous part of the 

frequency distribution for each metal. 

Although analyses of stream-sediment samples 

have detected some gold, even in localities outside 

the known placer areas, samples of the type collected seem generally inadequate to detect placer 

gold. Of the 48 samples taken from streams at or 

just below known placers, gold was detected in 

only 14. 

In the discussion of silver, the data for the 79 

stream-sediment samples collected before 1967 are 

omitted because the analytical values of these samples seem about four times too high when compared 

with those of the later samples. 

DISCUSSION OF ANOMALOUS AREAS 

Gold in detectable amounts seems to be fairly 

widespread in the Wiseman-Chandalar region, for 

it is found in many of the quartz vein samples and 

in most of the panned samples taken along the 

North Fork of the Koyukuk (fig. 3). It occurs not 

only in and near the schist and granitic rocks, but 

also in the area of sedimentary rocks to the north. 

Gold concentrations greater than 0.1 ppm (parts 

per million) in rock samples are present, however, 

only in or close to the metamorphic belt, and gold 

in panned samples increases abruptly where the 

North Fork enters the placer belt along the north 

margin of the metariwrphic rocks. 

The most prominent anomalous areas indicated 

by steam-sediment samples are the Chandalar and 

the Nolan-Hammond River areas. These areas contain a disproportionate share of the samples with 

detectable gold and of samples with high to anomalous concentrations of one or more base metalslead, arsenic, and molybdenum at Chandalar; antimony, in the Nolan-Hammond River area (figs. 3, 

7, 12). The association of gold and base-metal 

anomalies in stream sediments from these areas 

reflects the mineral association in the vein and rock 

samples. If the two mining districts are typical, 

then significant gold mineralization in this region 

IS marked by associated base-metal anomalies. 

WISEMAN DISTRICT 

The bedrock in the Nolan-Hammond River area 

consists mainly of black phyllite and gray schistose 

quartz siltstone with some calcareous beds. Disseminated pyrite is common in both the phyllite and 

the quartzose rocks. Quartz occurs in crenulated 

stringers and knots and locally, with stibnite, in 

veins and fracture fillings that postdate metamorphism and folding. A buried pluton south of Wiseman is suggested by heavily tourmalinized vein 

quartz on the west flank of Emma Dome and by 

sHicated limestone at the base of the east flank 

of Emma Dome. 

Placer deposits are of three ages: present stream 

deposits, old buried channel fillings, and probably 

still older high bench deposits. Glacial debris and 

erratics indicate that an early stage of glacial ice 

covered part of the Nolan Creek-Hammond River 

divide and could have been the source of the reworked erratic boulders in the high bench placer 

gravels on the Nolan Creek and lower Hammond 

River drainages. The buried bedrock valley of Nolan 

Creek is a V-shaped gulch (Maddren, 1913), and 

the lower Hammond valley is in part a buried canyon; both were probably incised after the retreat of 

ice of this early stage and partly refilled with goldbearing gravel before the next recognizable glacial 

advance. The gravel fill in Nolan Creek consists 

mainly of chips of locally derived black phyllite. 

Drift of unknown thickness covers the main valley floors of Wiseman Creek, the Middle Fork Koyukuk River, and the upper Hammond River; Pleistocene muck and gravel buries the placers in the 

old bedrock channel of Nolan Creek to depths about 

210 feet near the mouth to about 20 feet near the 

head. Ice of the later advance seems to have scoured 

the main valleys, but not the gold-bearing tributaries. Reed (1938) reported that the buried bedrock channels of the Hammond River and Gold 

Creek (fig. 3) extended out about three-fourths of 

a mile into the Middle Fork Koyukuk valley at 

depths of 115 and 100 feet, but steep dropoffs of 

bedrock beyond this point suggest that these tributary channels have been cut off by glacial scouring 

of the Middle Fork Koyukuk. 

Traces of gold are common in stibnite and quartz 

veins in the Nolan-Hammond River area; these 

veins are therefore thought to be part of a system 

whose erosion yielded the placer deposits. (See 

figs. 4, 5). 

Small amounts of gold (0.02-0.05 ppm) were detected in most of the area examined. The highest 

concentrations were found in a small stibnite prospect at the head of Fay Creek, where one sample 

contained 9.2 ppm gold, and in a thin quartz vein 

at the head of Thompson Pup, where 5.8 ppm and 

0.97 ppm gold were measured by duplicate analyses 

of one sample. The next highest concentrations 
DISCUSSION OF ANOMALOUS AREAS 9 

found are only 0.06-0.08 ppm gold-concentrations 

no greater than are found in some of the samples 

outside the mining districts (fig. 3). 

Gold in the veins is closely associated with anti1:,oo15' 

2 0 v~;;~~t 

~le'"'""' 

(J 1 MILE 

mony and arsenic (fig. 6). All samples of quartzstibnite veins from lower Smith Creek, Midnight 

Dome, and the head of Fay Creek contain detectable 

gold, and with one exception, all gold concentrations 

EXPLANATION 

UNCONSOLIDATED 

DEPOSITS 

rn . 

. 

Alluvium 

Glacial and glaciofluvial deposits 

High-terrace deposits 

containing glacial 

boulders 

Qtp. rfepll.,ff., /IIIII" 1/IUSf/y n·-

1/10/'Pr/ b!l p/aN'I' 111i11i111f 

Contact 

MINES AND 

PROSPECTS 

Stream where placer 

gold has been mined 

in present channel or 

old, deeply buried 

channel (From Reed, 

1938) 

Stibnite prospect 

GEOCHEMICAL 

SAMPLES 

0 

Stream-sediment sample 

locality 

2 5 

Oc:J 

Rock-and soil-sample 

locality or traverse, 

showing numberof 

samples collected 

>-

et:: 

<{ 

z 

cr: 

w 

I-

<{ 

:J 

0 

FIGURE 4.-Sample localities and unconsolidated deposits in Nolan-Hammond River area. 
10 

150°15' 

GEOCHEMICAL RECONNAISSANCE, SOUTHERN BROOKS RANGE, ALASKA 

( 

--

0 1 MILE 

150°00' 

EXPLANATION 

Concentration of gold, 

in parts per million 

0 

Stream-sediment sample 

~ 

0.02-0.039 

() 

0.04-0.049 

~ 

0.05-0.059 (none >0.059) 

Rock sample 

V. indicates t•ein 8ample. 

Others are country rock 

0.02-0.039 

0.04-0.079 

0.08-0.29 

.9.2 

0.3-9.2 

Values for single and 

duplicate analyses 

shown 

0 

Soil sample 

[!!! 

0.02-0.039 

() 

0.04-0.079 (none >0.079) 

FIGURE 5.-Gold in stream-sediment, rock,and soil samples from Nolan-Hammond River area. 
DISCUSSION OF ANOMALOUS AREAS 

150° 15' 150°00' 

11 

EXPLANATION 

Concentration of arsenic 

and antimony, in parts 

per million 

0 

Stream-sediment sample 

As 100 (none > 100, none 

80-99) 

~ 

Sb 10 

~ 

Sb 15-3000. Value 

shown where >99 

Rock sample 

V, indicates vein sample. 

Others nre country rock 

~ 

As 120-199 

~ 

As 200-5000. Value 

shown where >999 

~ 

Sb 40-99 

~ 

Sb 100- >10,000. Value 

shown where >999 

0 

Soil sample 

~ 

As 120-199 

~ 

As 200-800 

lill 

Sb 40-99 

~ 

Sb 100-3000. Value 

shown where >999 

FIGURE 6.-Arsenic and antimony in stream-sediment, rock, and soil samples from Nolan-Hammond River area. Some 

concentration symbols are combined in the figure. 
12 GEOCHEMICAL RECONNAISSANCE, SOUTHERN BROOKS RANGE, ALASKA 

greater than 0.05 ppm are in rocks that contain 

anomalous antimony and arsenic. The exception is 

the richer of the two veins at the head of Thompson 

Pup, and this vein is close to the only antimony 

anomaly detected north of the stibnite prospects. 

Antimony anomalies are present in stream sediments on the west flank of Smith Creek Dome but 

absent on the east flank. Anomalous concentrations 

of antimony also occur farther west in sediments 

from Acme Creek, Washington Creek, and unnamed 

creeks near Pasco Pass, as well as to the south 

in J ap Creek and Minnie Creek (figs. 6, 7). In 

these creeks, gold was detected analytically only 

in sediments of Jap Creek, but it is reported to occur 

in Washington Creek and Minnie Creek, and some 

of the gold in the buried channel of Nolan Creek 

may have come down Acme Creek (Reed, 1938). 

Stibnite pebbles were also reported from the placers 

on Gold Creek about 5 miles east of the N alanHammond River area (Schrader, 1904). The general association of gold and antimony suggests that 

the source of the antimony anomalies in stream 

sediments should be investigated. 

Zinc is associated with gold in the area between 

the heads of Fay Creek and Thompson Pup where 

most of the high vein and bedrock concentrations 

of gold were found (fig. 8), and may therefore be 

a useful pathfinder element. The zinc content does 

not always correlate directly with the gold; the 

zinc is more concentrated in soil than in rock and 

occurs in the bedrock as well as in the veins. A 

small amount of silver (2.9 ppm) occurred with 

gold in a milky quartz vein at the head of Thompson 

Pup. Generally, though, the low content of silver in 

rock, soil, and stream-sediment samples suggests 

that silver is not a useful pathfinder element for 

gold in this area. 

Maddren (1913) suggested that gold occurs in 

the pyritic country rock. Although some pyritic 

bedrock samples contain relatively high (0.4-0.65 

EXPLANATION 

Concentration of antimony, in parts per 

million 

Stream- sediment sample 

0 

100-300 

• 

700-3000 (Sb=500 not found) 

FIGURE 7.-Anomalous concentrations of antimony in stream-sediment samples in and near the Nolan-Hammond River 

area, the highest in the \Viseman-ChanJalar region. 
DISCUSSION OF ANOMALOUS AREAS 13 

150°15' 150°00' 

EXPLANATION 

Concentration of silver 

and zinc, in parts per 

million 

0 

Stream-sediment sample 

~ 

Ag 0.5-0.59 ( 1967 samples) (none >0.59) 

~ 

Zn 130-140 (none >140) 

<J 

Rock sample 

V, indicates vein sample. 

Others are country rock 

(> 

Ag 0.4-0.99 

~ 

Ag 1.0-1.5. 

(Values shown) 

~ 

Zn 120-159 (none > 159) 

D 

Soil sample 

~ 

Ag 0.4-0.99 

Iii] 

Zn 120-159 

~ 

Zn 160-199 (none >190) 

FIGURE 8.-Silver and zinc in stream-sediment, rock, and soil samples from Nolan-Hammond River area. 

ppm) concentrations of silver, the only gold detected 

in bedrock was from samples near gold-bearing 

veins or from surfaces likely to have been contaminated by place_r gold. 

CHANDALAR MINING AREA 

The bedrock of the Chandalar mining area is 

mainly gray quartz-muscovite schist with sills of 

mafic greenschist and some calcareous and quartzose 

beds (fig. 9). Black finely crystalline schist and 

phyllite containing greenstone sills underlies this 

schist along upper Big Creek and Tobin Creek. Chipp 

(1970) showed the contact with the black schist 

as a thrust fault. 

The major structural feature of the Chandalar 

area is a broad northeast-plunging antiform. The 

dominant structural trend in the area east and 

south of the mining area is northeast; however, near 
14 GEOCHEMICAL RECONNAISSANCE, SOUTHERN BROOKS RANGE, ALASKA 

0 2 3 4 5 MILES 

EXPLANATION 

ROCK TYPES 

Unconsolidated deposits 

Greenstone and greenschist 

Gray quartz-mica schist 

R 

Black schist and phyllite 

Distinguished locally 

Calcareous schist and hornfels 

Contact 

Fault ........... _.__.__._ Inferred thrust fault 

Sa wteeth on upper p/.ale 

Inferred shear zone 

--+-__. 

Anticline, showing direction of plunge 

_L ~ 

Measured strike and dip 

of foliation, and strike 

and dip from distant 

view 

MINES AND PROSPECTS 

Stream with mined gold 

placer 

X 

Gold deposit or prospect 

GEOCHEMICAL SAMPLES 

0 Stream-sediment sample 

0 Soil-sample locality 

t:. Rock-sample locality 

6 Rock-and soil-sample 

traverse, showing 

number of samples 

collected 

FIGURE 9.-Sample localities and geologic map, Chandalar area. (Enlarged from regional geologic map. For detailed map 

of northern part see Chipp ( 1970).) 

the known gold deposits, the linear elements trend 

northwest. A northeast-striking high-angle fault 

parallel to upper Big Creek and a northwest-striking 

fault in Tobin Pass bound this area of dominant 

northwest trends. The most conspicuous northwesttrending element is a shear zone that has been exposed in the Mikado mine. On the ridge crest east 

of the mine, this shear zone is marked by discordant 

dips. In the tunnel and trenches at the mine, the 

zone is about 50 feet wide and dips steeply, generally 

to the northwest (Frank Birch, written commun., 

1968). Schist within this zone is obliquely sheared 

and contains subparallel sheared and brecciated goldbearing quartz veins and lenses. The larger veins 

are near the two walls of the shear zone. 

Glacial drift makes up most of the unconsolidated 

deposits in the main valleys and extends up Squaw 

and Little Squaw Creeks to the gold placers (Mertie, 

1925, p. 254). However, the alluvial deposits in upper Tobin and Big Creeks seem to be entirely of 

local rocks. 

Samples of mineralized rock from the worked 

deposits show an association of metals that may be 

a guide to other lode deposits in the area. Arsenopy-
DISCUSSION OF ANOMALOUS AREAS 15 

rite, sphalerite, and minor galena and stibnite are 

present in ore from the Mikado mine ( Maddren, 

1913), and high concentrations of silver, arsenic, 

lead, antimony, and zinc were measured in the 

samples (fig. 10). The copper content of mineralized 

rock is generally low. 

Soil samples show a similar association of metals. 

0 

A. GOLD 

v v ---;c--~v 

~~ ~-~~ 1~---

MIKADO 

MINE 

~~~.0 n 

B. SILVER AND MOLYBDENUM 

C. ARSENIC AND ANTIMONY 

D. LEAD AND ZINC 

0 1 MILE 

Samples near the Little Squaw and Mikado deposits 

generally contain above average amounts of lead, 

molybdenum, and either antimony or arsenic, and 

high zinc content is associated with high gold and 

silver content at the Mikado mine and Star prospect. 

The copper content of soils near the prospects is 

generally low. The highest concentration of gold 

/ 

/ 

/.. 

----~---

/ --7.2v.~- ~~ _..../~¥,_!LITTL ~V SQUA 

~ ~ 

~ ~ 

Gl~ 

EXPLANATION 

Inferred shear zone 

X 

Gold deposit or prospect 

0 

Stream-sediment sample 

Rock sample 

V, indicates vein sample 

D 

Soil sample 

Concentration, in 

parts per million 

A. Gold 

~ 0.02-0.039 

[J ~ 0.04-0.079 

'I ~ 0.08-0.29 

• • 0.3-392 

(Value shown) 

~ 0.05-0.059 

B. c. D. 

Ag As Ph 

0.4-0.99 120-199 70 

Ag As Ph 

1.0-7.2 200-20,000 100-700 

(Va I u e shown) 

Mo 

5 

Mo 

7 

Sh Zn 

40-99 100-159 

Sh Zn 

100-1500 160-2500 

(Value shown) 

As Ph 

80-99 30 

(Value shown) 

FIGURE 10.-Gold, silver, molybdenum, arsenic, antimony, lead, and zinc in rock, soil, and stream-sediment samples near 

gold deposits in the Chandalar area. For location see figures 11 and 12. Some concentration symbols are combined in 

the figure. 
16 GEOCHEMICAL RECONNAISSANCE, SOUTHERN BROOKS RANGE, ALASKA 

in the soil was found about 100 yards west of the 

Mikado portal, and most of the samples with high 

concentrations of silver and arsenic were also west 

of the portal. Conversely, the highest (!oncentrations 

of antimony and molybdenum are east of the portal. 

The Mikado shear zone is also mineralized a mile 

west of the portal; there gold occurs in quartz veins 

and in soil on the topographic trace of the shear 

zone, and the soil contains anomalous amounts of 

arsenic and above average amounts of silver, lead, 

and zinc. 

Sediments in streams that drain the lode pros67" 

30' 

67" 

25' 

() -- / 

/ 

0 4 

pects contain gold and above average amounts of 

zinc, lead, or silver. Most of the high concentrations 

of arsenic and copper in stream sediments are at 

localities near the lodes (figs. 11, 12). Chipp (1970) 

also found that concentrations of copper, and possibly silver, are significantly higher in these streams 

near the lodes. 

OTHER METAL OCCURRENCES IN THE CHANDALAR AREA 

Base-metal mineralization seems to be largely 

within the area of northwest-trending shear zones. 

Base-metal anomalies in stream sediment samples 

5 MILES 

EXPLANATION 

Fault 

Includes thrust faults 

Inferred shear zone 

--+--+ 

Anticline, showing direction of plunge 

Concentration of gold 

and silver, in parts 

per million 

0 

Stream-sediment sample 

~ 

Au 0.02-0.039 

() 

Au 0.04-0.049 

~ 

Au 0.05-0.059 

Au 0.08-0.2. • (value shown) 

0 

Ag 0.5-0.59 

Au <0.02 and Ag <0.5 

not shown 

Rock sample 

Y indicates vein sample 

~ Au 0.02-0.039 

~ Au 0.04-0.079 

Au 0.3-1.7 • 

0Ag.5 

Ag 0.5-0.59 (value shown) 

0 

Soil sample 

DAg .53 

Ag 0.5-1.4 (value shown) 

See fig. 10 for Au and 

Ag in rock and soil 

samples in Mikado 

and Little Squaw 

areas 

FIGURE 11.-Gold and silver in stream-sediment, rock, and soil samples from the Cha.ndalar area. 
DISCUSSION OF ANOMALOUS AREAS 17 

67° 

25' 

148°30' 

Zn 130 

,_.,.... '/- __ \ ....... 

\-

0 2 4 5 MILES 

EXPLANATION 

Fault 

Includes thrustfaults 

Inferred shear zone 

--+--+ 

Anticline, showing direction of plunge 

Stream-sediment samples with high or anamalous concentrations 

of Zn, Pb, As, Sb, Cu 

or Mo 

Ph 30 

~ 

1 metal 

Ph 30 ()As 80 

2 metals 

Zn 150 Mo 1.5 Zn 150 As 200 

aAs 120 • Ph 30 Cu 70 

3 metals 4 metals 

Showing metals and concentration, in parts per 

million 

X 

Gold deposit or prospect 

Rock and soil samples 

with high or anomalous concentrations of 

As, Pb, Cu, and Mo. 

For As, Pb, and Mo in 

Mikado and Little 

Squaw areas, and for 

all samples with high 

concentrations of 

antimony and zinc, 

see fig. 10 

Rock sample 

V, ,indicates Pein sample 

0 

Soil 

~Cu 50 ~Cu 50 

1 metal 

<)t~ 1760 

2 metals 

Showing metals and concentration, in parts per 

million 

FIGURE 12.-Zinc, lead, arsenic, antimony, copper and molybdenum in stream-sediment, rock, and soil samples from the 

Chandalar area. 

are concentrated within this area, and, with one 

exception, the samples of rock and soil from outside 

this area have low base-metal contents. Gold, however, occurs in many stream sediments east of the 

area and on the north side of Lake Creek-Grave 

Creek valley. Some of this gold may have been dispersed by glaciation, but most of the gold detected 

probably is locally derived, for it occurs mostly in 

headwaters and small tributaries above the level 

of glacial deposits. 

The greatest concentration of anomalies in stream 

sediments outside the drainage from known lodes 

is on MeN ett Fork and the unnamed stream to the 

northwest, where gold occurs with silver or lead and 

with above average copper and zinc. Chipp's (1970) 

samples did not show base-metal anomalies in these 

two streams, but did show them in the next stream 

northwest. An inferred northwest-trending shear 

zone close to the sample localities, mapped only from 

aerial photographs, merits examination. 

Gold is also present outside the mining area in 

sediments from streams that cross inferred northeast-trending shear zones near McLellan Creek, Day 

1 

Creek, and Rock Creek and south of the inferred 
18 GEOCHEMICAL RECONNAISSANCE, SOUTHERN BROOKS RANGE, ALASKA 

northwest-trending fault along Big Creek. High 

contents of molybdenum, lead, arsenic, and zinc are 

present locally in sediment samples near Day Creek 

Base from U.S. Geological Survey 

Wiseman and Chandalar 

1:250,000, 1956 

0 5 10 

and south of the inferred Big. Creek fault. The high 

gold content ( 5.2 ppm) of a sediment sample from 

a small tributary south of Big Creek was not con15 20 MILES 

FIGURE 13.-Silver and lead in stream-sediment samples and 
DISCUSSION OF ANOMALOUS AREAS 

19 

firmed by a duplicate analysis and probably reflects 

the effect of a single gold particle. 

The concentrations of lead and molybdenum are 

high in stream sediments of Big Joe Creek and its 

tributaries, and gold occurs in quartz veins at the 

silver in rock and soil samples from Wiseman-Chandalar region. 

prospect near the headwaters of Big Joe Creek and 

on the mountain southwest of Big Joe Creek. 

OTHER ANOMALOUS AREAS 

A third association of anomalies is found in the 

carbonate terrane at the north margin of granitic 

EXPLANATION 

Concentration of silver, 

in parts per million, 

in samples 

0 

Stream sediments 

(1967 samples only) 

~ 

0.5-0.59 

e 

0.6-1.15 

<0.5 not shown 

0 

Rocks 

~ 

1.0-3.0 

6.0-19.0. • None found 

in range 3.1-5.9 

<LO not shown 

0 

Soil 

Cl 

1.0-3.0 

< 1.0 not shown 

Concentration of lead, 

in parts per million, 

in stream-sediment 

samples 

~ 

50-1000 

Value shown for concentrations greater than 

100 
20 GEOCHEMICAL RECONNAISSANCE, SOUTHERN BROOKS RANGE, ALASKA 

rocks on the North Fork of the Chandalar. Here, 

gold in stream-sedilnent and rock samples is 

associated with anomalous concentrations of lead, 

zinc, and copper and relatively high concentrations of silver. Relatively high concentrations of 

silver also occur in rocks and stream sediments 

in a poorly defined zone that follows the trend of 

the carbonate rocks southwestward from the North 

Fork of the Chandalar to the North Fork of the 

Koyukuk (fig. 13). Although the maximum silver 

concentrations in the stream-sediment samples are 

only four or five times higher than the median value, 

higher concentrations are known at three localities 

in this zone. Schrader (1900) collected a vein sample that assayed 6 ppm silver and 18 ppm gold 

from a locality on the North Fork of the Chandalar 

whose approximate position is shown by a question 

mark on figure 13. A sample of galena submitted 

from a prospect in the nearby limestone (not shown 

on fig. 13) assays 360 ppm silver and 6.5 ppm gold. 

Farther west, silver and copper nuggets were found 

in the gold placer on Mule Creek according to Maddren (1913) .

1 

The relatively high silver concentrations are 

principally in the area where the carbonate and calcareous rocks have been intruded by granitic and 

mafic rocks and are in part metamorphosed. 

Schrader ascribed his sample to the mafic rock unit, 

but the closeness of his locality to a granite sill 

makes an association with the mafic rocks uncertain. 

Gold was detected in some samples outside the 

three main anomalous areas. A high concentration 

of gold occurs with silver in samples from one thin 

arsenic-rich vein in the system of east-trending 

quartz veins north of Thazzik Mountain. Gold was 

detected in sediment samples from many of the 

streams south of Wiseman that contain placer gold 

and from one stream that flows almost entirely in 

the glacial drift south of the mountains, but none 

of these samples contain high concentrations of 

other metals. Although many of the placers south 

of Wiseman probably have local sources, gold and 

silver in a quartz vein southwest of Emma Dome is 

the only direct evidence of mineralization in that 

area. A large gossan on Redstar Mountain in the 

northwestern part of the region contains high concentrations of arsenic, antimony, and molybdenum 

but no detectable gold. 

SUMMARY 

Gold-bearing quartz and quartz-stibnite veins are 

common in the N alan-Hammond River area adjacent 

to the placer deposits and are probably part of the 

vein system that was the source of the placers. 

Although gold is generally present in trace amounts 

only, concentrations of as much as 9.2 ppm in 

stibnite and 5.8 ppm in quartz are present. Gold 

was not detected in the pyritic bedrock except near 

veins or where the bedrock may have been contaminated by placer gold. Antimony anomalies in 

stream sediments on and west of Acme Creek suggest the presence of veins west of the Nolan Creek 

placer deposits. 

Near Chanclalar most mineralization coincides 

with an area of northwest-trending shear zones that 

contains the known gold lodes. Within this area gold 

and arsenic were detected about 1 mile northwest 

of the Mikado mine along the strike of the Mikado 

shear zone. Gold and base-metal anomalies in streamsediment samples 2-4 miles northwest of the Little 

Squaw mine indicate that an inferred shear zone 

near these anomalies may also be mineralized. Both 

shear zones merit further investigation. Gold was 

also detected in several streams outside the lodebearing area. In most of these streams, gold is not 

accompanied by other metal anomalies. 

North of the Wiseman-Chandalar mining area, 

reconnaissance sampling shows relatively high concentrations of silver accompanied by gold and lead 

in a zone that is poorly defined but follows the regional strike of the carbonate rocks along the north 

edge of the schist and granitic rocks. One lead-silver 

prospect is known, but much more sampling is required to determine the significance of this zone. 

REFERENCES CITED 

Alaska Division of Mines and Geology, 1969, Mining activities: Alaska Div. Mines Bull., v. 17, no. 10, p. 2. 

Brosge, W. P., and Reiser, H. N., 1960, Progress map of the 

geology of the Wiseman quadrangle, Alaska: U.S. Geol. 

Survey open-file map, scale 1:250,000. 

--1964, Geologic map and sections of the Chandalar 

quadrangle, Alaska: U.S. Geol. Survey Misc. Geol. Inv. 

Map I-375, scale 1:250,000. 

---1970a, Chemical analyses of stream-sediment samples 

from the Chandalar and eastern Wiseman quadrangles, 

Alaska: U.S. Geol. Survey open-file report, 56 p., tables, 

map. 

--- 1970b, Chemical analyses of rock and soil samples 

from the Chandalar and eastern Wiseman quadrangles, 

Alaska: U.S. Geol. Survey open-file report, 8 p., 3 maps. 

Chipp, E. R., 1970, Geology and geochemistry of the Chandalar 

area, Brooks Range, Alaska: Alaska Div. Mines and 

Geology, Geologic Rept. no. 42, 39 p. 

Cobb, E. H., 1962, Lode gold and silver occurrences in 

Alaska: U.S. Geol. Survey Mineral Inv. Map MR-32, 

scale 1 :2,500,000. 

1 Since this repot·t was submitted, about 240 claims in seven groups h<l\·e been staked north and northeast of Mule Creek, near two of the silver localities shown in figure 13. · 
REFERENCES CITED 21 

---1964, Placer gold occurrences in Alaska: U.S. Geol.• 

Survey Mineral Inv. Map MR-38, scale 1 :2,500,000. 

Maddren, A. G., 1913, The Koyukuk-Chandalar region, Alaska: U.S. Geol. Survey Bull. 532, 119 p. 

Marshall, Robert, 1933, Arctic Village: New York Literary 

Guild, 397 p. 

Mertie, J. B., Jr., 1925, Geology and gold placers of the 

Chandalar district, Alaska: U.S. Geol. Survey Bull. 

773-E, p. E215-E263. 

Reed, I. M., 1938, Upper Koyukuk region, Alaska: Alaska 

Dept. Mines [rept. unpub.], 169 p. 

Schrader, F. S., 1900, Preliminary report on a reconnaissance along the Chandalar and Koyukuk Rivers, Alaska, 

in 1899: U.S. Geol. Survey 21st Ann. Rept., p. 443-486. 

--- 1904, A reconnaissance in northern Alaska: U.S. 

Geol. Survey Prof. Paper 20, 139 p. 

White, M. G., 1952, Radioactivity of selected rocks and placer 

concentrates from northeastern Alaska: U.S. Geol. Survey Circ. 195, 12 p. 

U. S. GOVERNMENT PRINTING OFFICE: 1972 0- 455-676