LEAD-SILVER DEPOSITS

IN THE OMILAK AREA,

SEWARD PENINSULA, ALASKA

By John J. Mulligan

report of investigations 6018

UNITED STATES DEPARTMENT OF THE INTERIOR

Stewart L. Udall, Secretary

BUREAU OF MINES

Marling J. Ankeny, Director
This publication has been cataloged as follows:

Mulligan, John J

Lead-silver deposits in the Omilak area, Seward Peninsula,

Alaska. [Washington] U. S. Dept. of the Interior, Bureau of

Mines [1962]

ii, 44 p. illus., map, tables. 27 cm. (U. S. Bureau of Mines.

Report of investigations, 6018)

Bibliography: p. 44

1. Lead ores. 2. Silver ores. 1. Title. (Series)

TN23.U7 no. 6018 622.06173

U. S. Dept. of the Int. Library
CONTENTS

Page

Introduction and summary .. .1.....

Acknowledgment ............................................ 3

Location and accessibility . . . 3

History and production of the Omilak area . . . 3

Physical features, climate, and water supply .............7

Labor supply and living conditions . . . 9

Property and ownership . . . 9

General geology. . . 10

Description of the deposits . . . 12

Foster prospect . . . 12

Omilak mine ...................................... 12..... 

Bureau of Mines work . . . 14

Bulldozer trenching .................................. 14

Purpose and extent . . . 14

Results . ........................................ 15

Diamond core drilling and sampling . . . 16

Methods and conditions . . . 16

Results ... 17

Interpretations . . . 37

Accessory metals and minerals . . . 38

Gold and silver . . . 38

Tin . . ..................................... ... . 39

Copper .......................................... 40

Antimony ... 40

Radioactivity . . . 41

Miscellaneous sampling . . . 42

Omilak mine ... 42

Other prospects ................................. 42

Bibliography .. ............................................ 44

ILLUSTRATIONS

Fig.

1. Index map of Alaska .. 4

2. Seward Peninsula .. 5

3. General geology of the Darby Mountain area . . 6

4. Geology of the Omilak area .. 11

5. Foster prospect .. 13

6. Vertical section through diamond-drill hole 1 .. 18

7. Vertical section through diamond-drill holes 2 and 3.. 19

8. Vertical section through diamond-drill hole 4 .. 20
ILLUSTRATIONS (Con.)

Zia. Fig Page

9. Vertical section through diamond-drill hole 5, 6, 8,

and 9 ............. ... .... 21

10. Vertical section through diamond-drill hole 7 ........ 22

11. Vertical section through diamond-drill hole 10 ....... 23

12. Vertical section through diamond-drill hole 11 ....... 24

13. Vertical longitudinal section on A-A, Foster prospect 38

TABLES

1. Weather data, White Mountain, Alaska . . 8

2. Population of the southern part of the Seward

Peninsula ......................................... 9

3. Lode claims .......................................... 9

4. Analyses of Foster pit samples . . 15

5. Analyses of trench samples . . 16

6. Diamond-drill-hole log, hole 1 . . 25

7. Analyses of diamond-drill core samples,

hole 1 ............................................. 25

8. Diamond-drill-hole log, hole 2 . . 26

9. Analyses of diamond-drill samples, hole 2 . . 26

10. Diamond-drill-hole log, hole 3 . . 27

11. Analyses of diamond-drill samples, hole 3 . . 28

12. Diamond-drill-hole log, hole 4 . . 29

13. Analyses of diamond-drill samples, hole 4 . . 29

14. Diamond-drill-hole log, hole 5 . . ..................... 30

15. Analyses of diamond-drill samples, hole 5 . . 30

16. Diamond-drill-hole log, hole 6 . . 31

17. Analyses of diamond-drill samples, hole 6 . . 31

18. Diamond-drill-hole log, hole 7 . . 32

19. Diamond-drill-hole log, hole 8 . . 33

20. Analyses of diamond-drill samples, hole 8 . ... 33

21. Diamond-drill-hole log, hole 9 . ...... .. 34

22. Analyses of diamond-drill sludge samples, hole 9 ... 35

23. Diamond-drill-hole log, hole 10 . . 35

24. Analyses of diamond-drill samples, hole 10 . . 35

25. Diamond-drill-hole log, hole 11 . . 36

26. Average grade of the gossan deposit in diamond-drill

holes 2, 3, 5, and 6 . . 37

27. Average silver-lead ratio of samples, Foster prospect 39

28. Analyses of samples for tin . . 40

29. Antimony analyses of samples . . 41

30. Radiometric analyses of samples . . 41

31. Analyses of Omilak mine specimens ... 42

32. Analyses of miscellaneous samples . . 43
LEAD-SILVER DEPOSITS IN THE OMILAK AREA,

SEWARD PENINSULA, ALASKA'

by

John J. Mulligan2

INTRODUCTION AND SUMMARY

Lead-silver deposits in the Omilak area, on the western slopes of the

Darby Mountains, Seward Peninsula, Alaska, were investigated by the Bureau

of Mines, during the 1953 and 1954 field seasons, as a part of the U.S.

Department of Interior's continuing program for the development of Alaska's

resources. The Omilak area was the scene of early day prospecting and mining

activity. The Omilak mine, which operated from 1881 to 1890, was the second

producing lode mine in Alaska; the first was a small gold mine near Sitka.

Several hundred tons of ore were produced at the Omilak mine; as an indication

of grade, 41 tons shipped from Omilak in 1889 contained 75 percent lead and

142 ounces of silver per ton.

A prominent, nearby occurrence of lead-silver minerals, found but not

explored during this period, has since become known as the Foster prospect.

Subsequent exploration of this prospect revealed an abundance of massive

galena occurring on an outcrop and as float scattered through limestone talus.

Evidence of lead deposition, together with the generally high silver content

of lead ores previously shipped from the district, indicated that deposits

might be found which would be commercially valuable even in this remote area.

To investigate the possibility, the Bureau of Mines made a reconnaissance of

the Omilak area and did bulldozer trenching, diamond core drilling, and

sampling at the Foster prospect. Data resulting from the investigation are

presented in detail in this report and are summarized in the following

paragraphs.

The western slopes of the Darby Mountains are composed of a series of

extensively folded Paleozoic or possibly pre-Paleozoic metalimestones and

schists that are in contact, to the east, with a large granitic complex.

The dominant geological structure of the Omilak area is a northward pitching

anticline. The axis of this anticline is about 6 miles west of the granitelimestone contact. The lead deposits in the area occur as irregular replacements of limestone. At the Foster prospect the deposits are on the anticlinal

1 Work on manuscript completed October 1961.

2 Mine examination and exploration engineer, Bureau of Mines, Region I,

Juneau, Alaska.
2

crest. The Omilak mine is about 3 miles from the Foster prospect in a zone of

local deformation imposed on the western limb of the anticline.

The Omilak mine workings are in a group of metalimestones with an outcrop

width of about 700 feet and underlain and overlain by massive schists. The

local deformation resulted in a maze of minor fractures and folds in the metalimestones, but there were not major faults. The mine workings were inaccessible, but a small stope, caved to the surface, appeared to have been 20 or 30

feet long, and possible 3 to 4 feet wide and oriented in a northwesterly

direction. Typical specimens of high-grade galena picked up on the shaft

dump contained from 55 to 71 percent lead and from 35 to 88 ounces of silver

per ton.

The Foster prospect comprises a zonally arranged lead-silver-bearing

gossan deposit extending about 700 feet along a line of fracturing having a

general strike of N. 200 to 40° W. and an approximately vertical dip. To

sample this deposit, the Foster pit was deepened, 7 trenches were excavated

to delimit the outcrops, and 11 diamond-drill holes were drilled to depths

ranging from 201 to 430 feet. Intensive fracturing, weathering, and leaching,

extending to the greatest depths attained, made it impossible to determine

definitely either the grade of the gossan or the nature of the primary

deposits. Core and sludge recovery were notably poor and erratic.

The Foster pit exposes a gossan outcrop--about 90 feet long and 12 feet

wide--composed principally of limonite and goethite with some cerussite and

less anglesite; the only recognizable primary minerals are nodules of galena

as much as 2 feet in diameter. Near the surface the outcrop resembled massive

galena. This apparently was due to residual concentration because continued

excavation indicated that galena nodules are less abundant at depth. Only

minor to trace amounts of galena were found in the diamond-drill holes. The

principal minerals found at depth were limonite, goethite, clay, quartz, and

cerussite in irregular earthy deposits, interspersed with zones of hard,

partially replaced silicified metalimestone.

Silver and lesser amounts of tin, zinc, copper, antimony, gold, and an

unidentified radioactive mineral occur with the lead at the Foster prospect.

The silver usually ranges from 0.2 to 0.4 ounce per ton, per percent of lead.

Tin occurs, distributed through the gossan, in amounts ranging from a trace to

0.3 percent. This discovery extends the areas of known tin deposition and

suggests that tin deposits may be found associated with the large granitic

intrusives forming the core of the Darby Mountains. The other metals usually

are present only in trace amounts.

The intensity and depth of weathering indicated by the diamond core

drilling at the Foster prospect suggests that conditions in the area, and

possibly throughout the Seward Peninsula, may be favorable for the formation

of supergene deposits at or near the water table.
3

ACKNOWLEDGMENTS

The base maps were adapted from maps distributed by the Geological Survey.

Information on the general geology and history of the area contained in Geological Survey publications was used in the preparation of this report (see

bibliography).

The cooperation and material assistance given the field party of the

Bureau of Mines by personnel of the Civil Aeronautics Administration (now

Federal Aviation Agency) stationed at Moses Point and Golovin was especially

valuable in this remote region and is gratefully acknowledged.

LOCATION AND ACCESSIBILITY

The Omilak area (figs. 1, 2, and 3) is in the Bendeleben Quadrangle,

Seward Peninsula, Alaska, on the western slopes of the Darby Mountains, 90

miles east-northeast of Nome, and 36 miles north-northeast of Golovin, at

latitude 65002' N. and longitude 162°35' W. The area includes the valleys

of Dry Creek, a headwater tributary of Omilak Creek, and the South Fork of

Mosquito Creek. Both Omilak Creek and Mosquito Creek are tributaries of the

Fish River. The Omilak mine is on the South Fork of Mosquito Creek; the

Foster prospect, on which most of the Bureau of Mines work was done, is at

the head of Dry Creek.

The area is uninhabited and is seldom visited; there are no roads or

marked trails. A gravel road from Nome, open in summer only, ends at Council,

about 35 miles to the west. The usual means of access is by bush planes that

can be chartered at Nome, the transportation and supply center for the Seward

Peninsula. The Bureau of Mines improved a natural airfield in Dry Creek

Valley about 5 miles from the Foster prospect and about one-half mile west

of the foothills of the Darby Mountains. The runway is 1,100 feet long and

has been used by planes carrying a load of 1 ton.

Freight too heavy or bulky for bush planes usually is hauled overland by

tracked-type tractors from the nearest point accessible to ocean shipping.

The ocean shipping season extends from late June to late October. Bureau of

Mines drilling equipment was landed at Golovin and hauled to the Omilak area

on tractor-drawn sleds during the latter part of August. A circuitous route

through the low hills south of the Fish River valley was followed to avoid

marshy flats and deep streams. One way, the distance traveled was about 50

miles and the driving time varied from 45 to 60 hours. The 75 drawbarhorsepower tractor could pull about 1 or 2 tons on thawed ground, 3 to 5

tons on frozen ground and 10 tons or more on frozen snow-covered ground.

Normally a trip can be made on frozen ground in about half the time it takes

on thawed ground.

HISTORY AND PRODUCTION OF THE OMILAK AREA

Deposits of silver-bearing galena in the Darby Mountains have been known

since the earliest trading posts were established on the Seward Peninsula;

the traders apparently learned about them from Eskimos. Official mention of
Ge /~~~74- 162 /

~~ *KeM ~ Ybc hior-s~

DF 4ALA~~ Wa

FIGURE1. ndex Mp -of laska
- SS~~~~~~~~~~~~~t~t

Ep~~~~~~~~~~~~~~~~~~~~~~~~~~E
6

0 r~~~~ le SceI

X/ LEGEND

9\ t///>//X/X/ t vItll G r n s t o ne.

//X> K ,, m ~~G r a n itse.

)\$t/'v' °, .~~ 4 ~ 8

t \/,/z_- ~~~~~Scale in MilYes

162e-30'

FIGURE 3. - General Geology, Darby Mountain Area.
7

lead deposits near Golovin Bay was made in the 1880 census by Petrof (4). In

1881, the Fish River mining district was organized and a company, headed by

John C. Green of San Francisco, staked claims on an outcrop which was named

the Omilak Mine. Omilak--also spelled Umilak, Umalik, and OOmilak--reportedly

is a contraction of an Eskimo word meaning heavy rock. The Omilak mine became

the second producing lode mine in Alaska; the first was a small gold mine near

Sitka.

The Omilak mine (fig. 3) was on a low ridge extending from the western

slopes of the Darby Mountains between the North Fork and South Fork of Mosquito

Creek. The principal underground workings were a 180-foot vertical shaft on

the crest of the ridge with two working levels and an adit on the south slope

of the ridge driven about 500 feet to intersect the deposits at depth (4).

Production was derived from the shaft operations and from surface float; no

ore was found in the adit. In 1889, a shipment of 41 tons of picked ore contained 75 percent lead and 142 ounces of silver per ton; total production for

the decade 1880 to 1890 has been estimated at between 300 and 400 tons. The

ore was transported overland, about 6 miles, to a landing on Omilak Creek; it

was then floated, in shallow-draft boats, about 75 miles down the Fish River

to Golovin and transferred to ocean-going vessels.

Mining was suspended in 1890, but sporadic attempts to resume operations

continued until the early 1920's. At the time of the Bureau's investigation,

the shaft was full of ice and the entrance to the adit was caved. A variety

of obsolete equipment and decaying buildings, reflecting several periods of

operation, were found at the mine openings and at the main camp about one-half

mile downstream on the South Fork of Mosquito Creek.

The Foster prospect also was discovered at an early date; several trenches

and pits appeared to be contemporaneous with the workings at the Omilak mine,

but no record of this early work could be found. In 1949, Neal W. Foster and

Associates of Nome, Alaska, rediscovered the prospect and exposed the outcrop

by bulldozer trenching. No production has been recorded, but several tons of

hand-sorted ore were piled nearby.

The western part of the Darby Mountains has received very little scientific attention. In 1900, members of a Geological Survey party, which

included W. C. Mendenhall, ascended the Fish River by canoe and visited the

Omilak mine Q). In 1909, another Geological Survey party, headed by P. S.

Smith and H. M. Eakin, traveled with packhorses and made a reconnaissance along

the western face of the Darby Mountains (4). In 1952, a brief examination of

the Foster prospect was made by Daniel A. Jones of the Department of Mines,

Territory of Alaska. Topographic maps of the area were compiled from aerial

photographs by the Geological Survey in cooperation with the Army Map Service

and are available to the public from the Map Information Office, Geological

Survey, Washington 25, D.C.

PHYSICAL FEATURES, CLIMATE, AND WATER SUPPLY

The Darby Mountains are a rugged range between two large interior basins,

known as Death Valley or Tubutulik River Valley and the Fish River Flats. The
8

mountains generally trend north-south and are characterized by deeply eroded

valleys and steep slopes; summits range in altitude from 2,000 to more than

3,000 feet. The areas dominantly underlain by limestone are barren of vegetation and mantled with frostbroken rock fragments; the hill slopes approximate

the angle of repose of this loose material and culminate in knifelike ridges.

The areas dominantly underlain by schists are characterized by more rounded

contours and support a sparse growth of tundra vegetation.

The Darby Mountains are near the western margin of tree growth. Small,

widely scattered groves of spruce trees occur where the valleys open into the

lowland basins. Mature trees have an average diameter of 6 to 8 inches and an

average height of 30 to 40 feet. Willows and alders are common and in some

places form dense thickets. The tundra vegetation of the lower hills and

basins is reported to be good reindeer pasture.

The climate is typically subarctic and, except for the top few feet, the

ground remains frozen throughout the year. Table 1 is a compilation of

weather data obtained, principally, at White Mountain, about 35 miles scuthwest of the Omilak area.

TABLE 1. - Weather data, White Mountain, Alaska'

Average annual temperature ............................. OF. 27.7

Average total annual precipitation .................. inches 14.83

Average total annual snowfall .......................... do. 58.2

Average date of breakup: Fish River . .May 22

Average date of freezeup: Fish River . ............ Oct. 14

Average date of breakup: Golovin Bay . ........... May 20

Average date of freezeup: Golovin Bay . ........... Oct. 20

Average date of breakup: Norton Sound . ........... May 312

Average date of freezeup: Norton Sound . ........... Nov. 112

Highest recorded temperature ........................... OF. 89

Lowest recorded temperature ............................. F. -55

Prevailing wind direction .. North

Number of days per year when minimum temperature is 320 F.

or lower. ...................................... 3231

'Data furnished by the U.S. Weather Bureau.

2Date from observations made at Moses Point.

3Taken from Nome data; White Mountain may vary a few days.

Water for diamond drilling was obtained from the headwaters of Dry Creek.

The water became available during the latter part of May when the snow started

to melt, and from June to September, inclusive, the headwaters contained a

fluctuating but usually ample supply. During the second week in October the

stream dried up. Because the drainage basin is barren of vegetation, occasional flash floods washed out pumping installations. However, this did not

seriously impede the work because the floods rarely lasted more than a

few hours.
9

LABOR SUPPLY AND LIVING CONDITIONS

Unskilled, and some skilled labor, can be hired on the Seward Peninsula

but skilled technicians and supervisory personnel usually must be recruited

from other areas. A large percentage of the dominantly Eskimo and part-Eskimo

population is available for employment because of the lack of industrial

development. Table 2 lists the population of the southern part of the Seward

Peninsula as recorded in the 1950 and 1960 census reports. Note that there

was little change in population but half of the communities were abandoned.

Housing must be provided for employees at most places; tents or light,

uninsulated frame cabins are adequate for summer use, but substantial, wellinsulated buildings are needed for year-around operations. The only buildings

in the Omilak area are the long-abandoned bunkhouses, shops and stables near

the Omilak mine and a 12- by 14-foot uninsulated frame cabin at the Dry Creek

airfield.

TABLE 2. - Population of the southern part of the Seward Peninsula

Inhabitants Inhabitants

Places 1950 1960 Places 1950 1960

Council ................ 41 0 Nome .1,930 '2,316

Elim ................... 154 145 Solomon ................ 93 0

Golovin ................ 94 0 White Mountain .129 151

Haycock................ 24 0 Total .2,5 9 .. F599 2,741

Koyuk .................. 134 129 _

PROPERTY AND OWNERSHIP

The two groups of lode claims listed in table 3 were the only known mineral locations in the Omilak area. The patented claims cover the Omilak mine;

the unpatented claims cover the Foster prospect. None of the claims were

mapped during the investigation.

TABLE 3. - Lode claims

Omilak mine:

Pioneer Claim1 ..... 1 9.91 acres

Omilak Claim' ...... 19.98 acres

Foster prospect:2

Claims: Claims (Con.): Claims (Con.):

Gossan No. 1 Would Be Lode Claim No. 1

Gossan No. 2 Ridge Lode Claim No. 2

Gossan No. 3 Utuan Lode Claim No. 3

Gossan No. 4 Dry Lode Claim No. 4

Bandy Jim Lode Claim No. 5

Benson Darby Lode Claim No. 6

Poppy Darby No. 2 Lode Claim No. 7

Lode Claim No. 8

'Patented on February 3, 1894, by the Omilak Gold and Silver Mining Co.

2 Location notices for the above 22 unpatented claims are on file in the

District Magistrate's Office, Second District, Nome, Alaska. Variations

in the spelling of some names were noted.
10

GENERAL GEOLOGY

The geology of the Darby Mountains has not been studied in detail, but

the general features are described in the Geological Survey publications

listed in the bibliography. The following discussion of the general geology

is based on data contained in these publications, but the local geology was

mapped during the investigation and all interpretations based on geological

evidence are those of the writer.

The western slopes of the Darby Mountains (fig. 3) consist of a series of

Paleozoic--or possibly pre-Paleozoic--metasediments that rise abruptly from

the thick alluvial cover of the Fish River basin. The metasedimentary exposure has a generally north-south orientation and an east-west width of from 2

to 10 miles; it is bordered on the east by a dominantly granitic igneous complex, probably of pre-Cretaceous age. The lower members of the sedimentary

series are thin-bedded metalimestones, interspersed with a few thin beds of

schist; the upper members are predominantly thick, alternating bands of metalimestones and quartzose schists. The Foster prospect is in the lower members

of the metasedimentary series about 6 miles west of the granite-metalimestone

contact. The Omilak mine is in the upper members of the series about 9 miles

west of the contact.

The dominant geological feature of the Omilak area is a northward pitching anticline. The axis passes through the Foster prospect, and the Omilak

mine is on the western limb. The anticlinal structure is well exposed on the

southern slopes of the ridge, south-southeast of the Foster prospect (fig. 4).

In this area the rocks are chiefly thin-bedded metalimestones with a few thin

beds of schists. Many, if not most of these metalimestones, are dolomitic.

Pronounced crenulations occur in some beds at the crest of the anticline;

minor crenulations occur in most beds, but some beds are only gently folded.

The differential folding resulted in a dense network of minor faults and

joints, many of which contain calcite or clay filling. The individual faults

and joints rarely extend through more than one bed or a series of thin beds;

there is no evidence of major faults. Northward from the Foster prospect the

anticlinal axis becomes more gently folded, crenulations are not apparent, and

faulting and jointing are less pronounced.

Greenstones are the only recognizable igneous rocks that intrude the

metasediments of the anticline. A prominent greenstone dike, about 1,500 feet

north of the Foster prospect (fig. 4), generally strikes east-west, dips 700

to 800 S., and can be traced for about 1 mile. Locally it pinches and swells

and, in some places, disappears; it is 15 to 20 feet wide at the east end and

gradually pinches out to the west. Petrographic analyses showed that it contains altered feldspar with some serpentine, pyroxene, amphibole, and small

amounts of magnetite, pyrite, chlorite, calcite, biotite, and limonite. Other

greenstone intrusives are short discontinuous bodies, usually of uncertain

orientation. A prominent outcrop of this type occurs in limestone about 2,000

feet south-southwest of the shaft at the Omilak mine. The more prominent

greenstone intrusives are shown on figure 4, but the wide distribution of

greenstone in the stream gravels indicates that many more are present. The

greenstones have had no discernable influence on the distribution of lead

minerals.
1 /m/i S c h \i 500s

0~~~~~~

F //js't e Greenst one

( ~~~~~~~~~~Obscured by overburden

\ // X = : z~~~~~~~ S tr i ke a nd d ip o f b ed s V O ~ ~ t , 21 V e r t i c a I s h oIf t

/ / Xijx 5°<l, X 19 Sample

it _ , < //// } 1 0 1500 3000 4500 6000

Sc12We t

FIGURE 4. - Geology of the Omilak Area.
12

DESCRIPTION OF THE DEPOSITS

Foster Prospect

The Foster prospect comprises a zonally arranged lead-silver-bearing

gossan deposit extending about 700 feet along a line of fracturing. The

fracture system is on or near the axis of an anticline, generally strikes

N. 200 to 40° W. and has a nearly vertical dip. The gossan material is

principally limonite and goethite with some cerussite and less anglesite.

The only recognizable primary mineral occurs as nodules of galena which are

most abundant on the outcrop in the Foster pit but are also scattered in the

overburden for a few hundred feet to the north and south.

The outcrop, exposed in the Foster pit (fig. 5), is about 12 feet wide

and 90 feet long with poorly defined, irregular borders except where it is

terminated abruptly to the northwest by hard, moderately bleached metalimestone. The southeast end is buried under a deep cover of overburden. Near

the surface the outcrop resembles massive galena owing to residual concentration of galena nodules. The nodules range in size from less than an inch to

about 2 feet in diameter and occur encased in oxidation products and imbedded

in a matrix of ice, clay, and earthy oxides. The pit was excavated to a depth

of about 20 feet without encountering much change except that the galena

nodules were less abundant in the bottom than nearer the surface. The depth

and degree of residual concentration are uncertain. No nodules large enough

to core were encountered in the drill holes, but a few recognizable fragments

of galena were recovered in the sludge samples.

The effects of intense weathering made it impossible to determine definitely the nature of the primary deposits. However, the position and type of

remnant minerals would suggest that the primary deposits were derived from

pneumatolytic solutions which invaded the metasediments after they had been

folded into approximately their present positions. The solutions penetrated

the more intensely fractured and broken zones and formed irregular deposits by

replacing limestone. Most of the original constituents have been oxidized,

and the soluble parts have been carried off, leaving only a relatively insoluble remnant.

Weathering and leaching effects similar in nature and intensity to those

on the surface, extend to depths in excess of 400 feet--the practical depthlimit of the drilling equipment. Clay-filled solution channels and earthy

oxide minerals in the fractures would indicate that the zone of downward

percolating water extends below this depth; there is no indication of the

depth to the water table. The intensity and depth of weathering suggests

that, where confining structures exist, conditions on the Seward Peninsula

may be favorable for the concentration of supergene deposits.

Omilak Mine

The Omilak mine (fig. 4) is in a zone of intense local deformation

imposed on the western limb of the same anticline in which the Foster prospect

occurs. The workings that can be seen are in a group of metalimestones,
13

D -H- 7

General strike a dip

\ \ ~~~~~DDH-3,2 .

\ \4 Ad / ~~~~~Foster pit \ DDHH-64 For ~ ~ ~ ~ q

t If/ 1 l < ~~~~LEGEND

$ | /<l r / = ~~~~Gossan

r Sk iBleached metlimestone

ofetsBroen gray metalimestone

to %6 / adz ~~~~~~~~Ionstgainedn sfoil with some

0 50 100 30 |x12 Surface sample

Sca * n tee \ 1~~~~~-4 Channel samples

Scale in ~~~~~~~~~ai- Diamond-drill hole

FIGURE 5. Foster Prospect.
14

having an outcrop width of over 700 feet, which forms one band in a series of

thick, alternating bands of metalimestones and schists. Stratigraphically,

these rocks are over 5,000 feet and possibly as much as 10,000 feet above

those at the Foster prospect.

The bedding near the Omilak mine generally strikes north-south and dips

to the west, but both the schists and the metalimestones are intensely contorted. The schists are folded but have few joints or fractures. Many small

folds, faults, and joints break the metalimestone beds although there is no

evidence of major faults or breaks extending through a number of beds.

The Omilak deposit could not be seen in place because the outcrops had

been removed during mining and the workings had either collapsed or were full

of snow and ice. Near the shaft a small stope had caved to the surface. It

appeared to have contained a lenticular ore body, possibly 20 to 30 feet long

and 3 or 4 feet wide, entirely within the limestone and oriented in a northwesterly direction. Lead minerals found in the shaft dump and in small nearby

fractures are similar in metal content to those at the Foster prospect, except

that silver and stibnite appear to be more abundant at the Omilak mine. There

is no evidence of a relationship between the deposits at the Omilak mine and

the Foster prospect other than a general similarity of minerals and mode-ofoccurrence.

BUREAU OF MINES WORK

The investigation started in the latter part of August 1953, when the

heavier items of equipment and supplies were assembled at Golovin and hauled

overland to the Omilak area. A natural airfield on Dry Creek was improved,

and lighter items were flown from Nome or Golovin as needed. Previous bulldozer trenching at the Foster prospect had revealed that frostbreaking and

intense weathering extended below the limits of surface excavation; therefore,

diamond drilling was the most practical means of sampling the deposit. The

drilling was supplemented by bulldozer trenching and by a reconnaissance of

the area to determine the general geology and the relationship between the

lead occurrences at the Foster prospect and the Omilak mine. Drilling started

September 11, 1953, and stopped on October 11 of that year; work was resumed

on June 1, 1954, and drilling was completed August 31, 1954. Reconnaissance

of the area and surveying and mapping proceeded simultaneously with the drilling and trenching.

Bulldozer Trenching

Purpose and Extent

The original Foster pit was deepened to about 20 feet, and 7 additional

bulldozer trenches were excavated to delineate the trend of the gossan outcroppings and to indicate the limits of deposition as a guide for diamond core

drilling. The Foster pit, bulldozer trenches, and sample locations are shown

in figure 5. Descriptions of samples and data of analyses are presented in

tables 4 and 5.
15

TABLE 4. - Analyses of Foster pit samplesi

Length, Percent Ounces per ton

Number2 feet Description Pb Zn Fe Au AR

1 3.0 Gossan . . ......... e ) 1.7 5.7 (4) (4 )

2 3.0 do . ...................... 0.6 2.6 9.0 0 0.14

3 3.0 do . ...................... 9.5 7.6 23.3 (3) 1.40

4 3.0 do ...................... . 22.1 .2 37.8 e ) 5.68

5 3.0 do . ...................... 6.8 (3) 39.8 (3) 2.75

6 3.0 do . ...................... 2.2 .1 19.7 (4) (4)

7 3.0 do ...................... . 11.6 .1 42.5 e3) 4.74

8 3.0 do ...................... . 25.6 .1 17.6 (3) 14.90

9 - Typical galena nodules ..... 48.0 .2 17.6 0 23.40

610 l High-grade galena ....... 80.0 (3) (43) () 25.42

e11 _ Wall rock . . ...... (4)3 .. .(4)

1 Sample locations are shown on figure 5.

2Numbers 1 through 8 are channel samples; numbers9 through 11 are selected

specimens.

3 Trace.

4No assay.

5 Sample 10, petrographic analyses: Galena, cerussite, and anglesite with some

associated limonite and small amounts of hornblende, arsenopyrite, chalcopyrite, quartz, and pyrite. Spectrographic analyses follows:

Al Sb As Sn Cu Pb & Zn Fe Ni Si Ti

D- E D D E A E E B- E E FLegend: Legend (Con.):

A - more than 10 percent. E - 0.01 to 0.1 percent.

B - 5 to 10 percent. F - 0.001 to 0.01 percent.

C - 1 to 5 percent. G - less than 0.001 percent.

D - 0.1 to 1 percent.

6Sample 11 petrographic analyses: Impure limestone containing magnesianbearing calcite with a relatively small amount of limonite that occurs

as stain.

Results

Generally, the approximate source of surface float could be found by

trenching, but good bedrock samples could not be obtained because of the

broken nature of the rock and the intensely weathered condition of the mineralized outcrops. The few samples obtained from trenches can be considered

only as specimens. Trenches 1 and 2, encountered no gossan material although

a few small galena fragments were found in overburden between the trenches.

The only evidence of mineralizing solutions was some bleaching along fractures

near the middle of trench 2. Iron-stained soil and occasional galena fragments, mixed with metalimestone debris, were encountered in the lower

(southwest) half of trench 3 and in trench 4. This material apparently was
16

derived from two or more small, poorly exposed fracture zones (samples 14 and

15). Sample 16 from trench 4 is a typical specimen of the high-grade float

occasionally found in both trenches 3 and 4. The upper end of trench 3

exposed no gossan material but did expose slightly bleached metalimestone

approximately in line with the outcrop in the Foster pit. Some small galena

fragments, found on the bank above the upper end of trench 3 (sample 12),

could not be traced to their source. Trench 7, therefore, was excavated to

determine whether the amount of galena float in the forstbroken debris would

indicate that extensions of the outcrop were exposed higher on the hillslope;

only a few small fragments of lead-bearing float were found. Trenches 5 and

6 exposed only broken, gray metalimestone with some iron staining on fracture

surfaces.

TABLE 5. - Analyses of trench samples'

Percent Ounces per ton

Number Description Pb Zn Fe Au Ag

12 Small float specimens found above the 69.6 (2) 5.7 0.01 30.36

N.E. end of trench 3.

13 Bleached metalimestone with iron- (3) (3) (3) (3)

stained fractures, trench 3.

14 Gossan material in fracture zone 1.3 (3) (3) (3) (3)

about 1 foot wide, trench 3.

15 Gossan material from a small fracture, .05 (3) (3) (3) (3)

trench 3.

416 Specimen of high-grade float, 51.4 (3) (3) .01 19.7

I trench 4.

'Sample locations are shown on figure 5.

2 Trace . 3No assay.

4Sample 16, petrographic analyses: Galena with some associated cerussite and

small amounts of anglesite and limonite. Spectrographic analyses follows:

Al Sb As Sn Ca Cu Pb Mg A_ Zn Fe Mn Si Ti Mo B

E+ E C- D E E A G D C A E D F F F

Legend: Legend (Con.):

A - more than 10 percent. E - 0.01 to 0.1 percent.

B - 5 to 10 percent. F - 0.001 to 0.01 percent.

C - 1 to 5 percent G - less than 0.001 percent.

D - 0.1 to 1 percent.

Diamond Core Drilling and Sampling

Methods and Conditions

The Foster prospect was explored by 11 holes totaling 3,015 linear feet

drilled to depths of 201 to 430 feet. Conventional diamond-drilling equipment

was used, and normal core-drilling procedures were followed. The core was

logged by the project engineer. No sludge was saved from hole 1; sludge
17

samples from the other holes were saved when the color of return water indicated the presence of metallic minerals. However, because of the porous

nature of the rock, all or part of many sludge samples were lost.

The rock drilled was a much-broken series of metalimestones with a few

thin beds of schist and sandstone. The mineralized zones and many of the

other numerous openings contained an earthy claylike filling that could not

be cored. Drilling was tedious and sample recovery was difficult, but the

only problems not common to drilling similar rock in warmer climates resulted

from the presence of permafrost.

Permafrost was encountered from a few feet below the surface to depths in

excess of 350 feet. Hole 8 may have penetrated to unfrozen rock at a depth of

400 feet (measured down the hole), but the evidence was inconclusive and was

based on the feel of the ground and the absence of ice in the samples. The

openings in the permanently frozen rock were not completely ice filled; drilling water was lost frequently in all holes to the greatest depths attained. A

strong inflow of ground water was encountered within the permafrost in hole 4

at a depth of 200 feet but was not encountered in other holes at greater

depths.

The principal operating problem from permafrost was freezing of water in

the drill holes when circulation stopped. No difficulty ensued while circulation was maintained. Measurements of the time required to form solid ice in a

drill hole were not made; the time was believed to vary widely, probably

dependant partly on the temperature of the circulating water and the length

of time it had been circulated before the stoppage. Two hours after circulation stopped in hole 5, solid ice was encountered at 155 feet and had to be

drilled to the bottom of the hole--at that time 265 feet. For practical purposes, it was found safe to assume that freezing never occurred in less than

45 minutes but might occur anytime thereafter. Antifreeze preparations were

not used because of the frequent loss of drilling water.

Ice in the frozen rock had an initial tendency to support the walls of the

drill holes, but, as drilling progressed, the ice would thaw and caving became

serious. When casing was reamed down at frequent intervals, it showed lessthan-normal tendency to bind; apparently casing limited the thawing effect by

preventing circulating water from coming in direct contact with the frozen

rock. The heat from the circulating water was ample to prevent the casing

from freezing to the rock or to free it after it had frozen. On several

occasions, when the drilling rods were not in the hole, the water in the

casing froze with no apparent bad effects except that it was necessary to

drill out the ice. Cementing the holes had only limited success; apparently

freezing adversely affected the setting qualities of the cement.

Results

The drill hole locations are shown on figure 5. Vertical sections

through the diamond-drill holes are shown in figures 6 through 12. The drillhole logs, together with tabulated chemical, petrographic, and spectrographic

analyses of core and sludge samples are presented in tables 6 through 26.
DDH-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~- co

1350-

1300-

LEGEND

3 Gossan

S Bleached metalimestone

s Metalimestone Ao

135.2 Depth in ft. to points 1 1200-

mentioned in table 6 \

o 50 100

~~~~~~~section A-A

Scale in feet

FIGURE 6. - Vertical Section Through Diamond-Drill Hole 1.
19

DDH-2 |~FosteE

-1300 \t\

Section A-.A

LEGEND

Gossan

B Bleached metalimestone

= Metalimestone

86.6 Depth in ft. to points

mentioned in tables 8and 10

0 50 100

Scale in feet

FIGURE 7. - Vertical Section Through Diamond-Drill Holes 2 and 3.
DDH-4 1350

'A~~~~~~ 01300

LEGEND

all ~~~~~~~1250

Gossan

3 Bleached metalimestone

i| Metalimestone

60.4 Depth in ft. to points 1200-

mentioned in table 12

Section A-A 1150-

) 50 100

Scale in feet

FIGURE 8. - Vertical Section Through Diamond-Drill Hole 4.
-1500 N

A1450 LEGEND

DDH-6 5, Gosson

-1400 asg//3 Bleached melalimestone

- i @ 0 Metalimestone

41 ~~~~~~57.0 Depth In ft. to points -13 50 DDH-88 t59 \ 9,R~e^° 570 Doomentioned In tables 14,16,19,8 21

-1250 50 I l% *

-1200X

-1150 , l

-1100\_

-1050 0

-1000)

Section A-A Scale in feet

FIGURE 9. - Vertical Section Through Diamond-Drill Holes 5, 6, 8, and 9.
1450

-1400 DD H-7

L EG E ND \#

-1300 Gossan

Ez Bleached metalimestone

z Metalimestone

-1250 64.4 Depth in ft. to points mentioned in table 18

0 M00 50 Section A-A

Scale in feet

FIGURE 10. - Vertical Section Through Diamond-Drill Hole 7.
23

1500 DH1

Section JA-JA

179.8

185.2 -1300 0 189.0

a 206.0

LEGEND

-1250 - i~~~~~~~~~~248.0

Gossan

261.0

E Bleached metalimestone

1 MetalimestoneL

28.0 Depth in ft. to points

mentioned in table 23

0 50 100

Scale in feet

FIGURE 11. - Vertical Section Through Diamond-Drill

Hole 10.
1350

Some galena

fragments and iron- DDH-11 II(Stained Soil mixed with metalimestone rubble.

-150 

4rb°°O

LEGEND

-1200 B Gossan

m Bleached metalimestone

:3 Metalimestone

25.3 Depth in ft. to points mentioned in table 25 Section A-A

0 50 100

Scale in feet

FIGURE 12. - Vertical Section Through Diamond-Drill Hole 11.
25

TABLE 6. - Diamond-drill-hole log, hole 1'

Location: See figures 5 and 6. Date begun: September 11, 1953

Elevation of collar: 1,375 feet. Date finished: September 24, 1953.

Depth: 353.6 feet Core sizes: BX to 10.0 feet.

Dip: -35°. AX to 37.4 feet.

Bearing: N. 800 E. EX to 353.6 feet.

Core

Foota e recovery, Formation

From To Distance percent

0.0 135.2 135.2 82 Broken, fine-grained, gray metalimestone with

many small calcite veinlets. Red, yellow, and

brown iron staining is prominent on fracture

surfaces.

135.2 186.0 50.8 55 Similar broken, gray metalimestone with more

numerous iron-stained fractures.

186.0 188.2 2.2 0 Sludge contained metalimestone fragments, quartz

grains, clay, and mica.

188.2 207.8 19.6 26 Gossan composed of broken, bleached, silicious

metalimestone and brown to red earthy clay.

No sulfide minerals were evident.

207.8 208.7 .9 78 Broken bleached silicious metalimestone.

208.7 245.7 37.0 43 Broken, gray metalimestone with iron-stained

fractured surfaces.

245.7 255.0 9.3 82 Broken, bleached, iron-stained metalimestone.

255.0 255.5 .5 50 Earthy dark-brown clay.

255.5 307.6 52.1 54 Broken, light-gray metalimestone with yellow to

red iron staining on fracture surfaces.

307.6 353.6 46.0 72 Broken, dary-gray metalimestone with very little

I___I_ I________ I________ iron staining.

'Analyses data in table 7.

TABLE 7. - Analyses of diamond-drill core samples, hole 11 2

Footage Percent Ounces )er ton

From To Distance Core recovery Pb Zn Fe Au Ag

188.2 193.4 5.2 38 0.20 0.34 1.5 0 0.02

193.4 196.4 3.0 17 .10 .20 2.2 (3) (3)

196.4 199.7 3.3 39 .06 .05 1.5 0 0

199.7 202.9 3.2 12 <.05 .08 .9 (3) 0

202.9 205.6 2.7 15 .09 .20 .5 (3) .06

205.6 207.8 2.2 18 <.05 <.05 .5 (3) .04

207.8 208.7 .0 78 .10 <.05 .1 (3 .01

'No sludge samples from this hole.

2 Spectrographic analyses of a composite of core samples from 188.2 to 208.7 feet:

Al As Be Bi Sn Ca Cu Pb _g & Zn Fe Mn Ni Si Ti V B

A D E E D A D+ E D F C A D E A E F C

Legend: Legend (Con.):

A - over 10 percent. E - 0.01 to 0.1 percent.

B - 5 to 10 percent. F - 0.001 to 0.01 percent.

C - 1 to 5 percent. G - less than 0.001 percent.

D - 0.1 to 1 percent.

3Trace.
26

TABLE 8. - Diamond-drill-hole log, hole 2

Location: See figures 5 and 7. Date begun: September 25, 1953.

Elevation of collar: 1,414 feet. Date finished: September 29, 1953.

Depth: 162.3 feet Core sizes: BX to 10.1 feet.

Dip: -350. AX to 29.2 feet.

Bearing: N. 77° E. EX to 162.3 feet.

Core

Footag recovery, Formation

From To Distance percent

0.0 86.6 86.6 83 Broken, fine-grained, gray metalimestone with a

few calcite veinlets and yellow, brown, and red

staining on fracture surfaces. A few small

fractures contain gray to brown earthy clay.

86.6 89.0 2.4 100 Similar metalimestone with many small fractures

filled with yellow-brown clay.

89.0 95.0 6.0 94 Broken metalimestone bleached to a gray-white

color.

95.0 97.0 2.0 94 Bleached metalimestone and soft, yellow-brown to

chalky-white clay.

'97.0 98.2 1.2 42 Iron-stained, bleached metalimestone partly

replaced by sulfide minerals.

198.2 105.0 6.8 6 Gossan principally composed of earthy ironstained clay with some recognizable sulfide

minerals including 2 rounded nodules of galena

about k inch in diameter. The small percentage

of recovered core contains hematite, limonite,

and bleached silicious limestone.

'105.0 108.2 3.2 69 Broken, silicious metalimestone with some sulfide

minerals. Fractures contain gossan material.

1108.2 112.5 4.3 50 Bleached, iron-stained, broken metalimestone with

some gossan material in the fractures.

112.5 162.3 49.8 64 Broken, fine-grained, gray metalimestone with

I_____ I____ I_______ I_______ some limonite staining on fracture surfaces.

'Analyses data in table 9.

TABLE 9. - Analyses of diamond-drill samples, hole 2

Footag Sample Percent Ounces per ton

From To Distance type Core recovery Pb Zn Fe Au Ag

97.0 98.2 1.2 Core 42 1.60 0.95 30.2 0.03 0.04

98.2 102.7 4.5 - 0 - - - - -

102.7 105.0 2.3 Core 17 .80 .72 13.8 0 .02

105.0 107.2 2.2 do. 50 .10 <.05 .3 (') 0

107.2 108.2 1.0 do. 100 .20 .13 .6 (') .46

198.2 102.7 - Sludge - 2.90 1.40 42.7 (e) .04

102.7 107.2 - do. _ <.05 2.30 32.2 f) .01

107.2 112.5 - do. _ 2.60 1.30 22.2 (1) .02

112.5 115.9 - do. _ .90 .05 5.5 j .17

1Trace.

2 Sludge sample 97.0 to 98.2 feet not recovered.
27

TABLE 10. - Diamond-drill-hole log, hole 3

Location: See figures 5 and 7. Date begun: September 30, 1953.

Elevation of collar: 1,413 feet. Date finished: October 9, 1953.

Depth: 151.3 feet. Core sizes: BX to 10.0 feet.

Dip: -53'. AX to 47.2 feet.

Bearing: N. 77° E. EX to 151.3 feet.

Core

_ ootaRe recovery, Formation'

From To Distance percent

0.0 86.6 86.6 83 Broken, fine-grained, gray metalimestone with a

few calcite veinlets. Yellow, brown, and

bright-red iron minerals form coatings on

fracture surfaces and occur in veinlets less

than 1/8 inch thick. Openings up to 2 inches

across contain earthy, brown to gray clay but

show no evidence of alteration by mineralizing

solutions.

86.6 90.3 3.7 81 Similar metalimestone with more numerous small

fractures and some bleaching along fractures.

90.3 104.4 14.1 74 Gray medium-grained to fine-grained metalimestone with various calcite veinlets 1/16 inch

and less across and many iron-stained fractures but no evidence of bleaching.

2104.4 108.8 4.4 41 Broken, bleached, iron-stained metalimestone

with some clay.

2108.8 113.8 5.0 20 Gossan zone consisting chiefly of earthy, ironstained clay predominately yellow, brown, or

red with only traces of sulfide minerals.

2113.8 132.6 18.8 76 Gossan zone consisting chiefly of metalimestone

largely replaced by goethite, hematite, and

limonite and interspersed with yellow to

reddish-brown clay. No galena and only traces

of other sulfide minerals were observed.

2132.6 138.1 5.5 24 Gossan zone consisting of earthy, yellow to

brown clay, with limonite and altered limestone fragments.

2138.1 141.0 2.9 76 Gossan zone consisting of goethite and limonite

grading into bleached, altered metalimestone.

2141.0 151.3 10.3 39 Broken gray medium-grained to fine-grained metalimestone with limonite staining on fracture

surfaces.

'Petrographic analyses of selected specimens of core from hole 3:

20 to 21 feet: Limestone containing minor amounts of limonite, serici'te, and

traces of kaolinite and carbonaceous matter.

47 feet: Limestone containing minor amounts of sericite, carbonaceous matter,

and a trace of limonite.

122 feet: Limestone with minor amounts of associated limonite pseudomorphs,

altered feldspar, kaolinite, and carbonaceous matter.

140 feet: Goethite and limonite with minor amounts of associated smithsonite

and sericite.

2 Analyses data in table 11.
28

TABLE 11. - Analyses of diamond-drill samples, hole 31

Footage Sample Percent Ounces per ton

From To Distance type Core recovery Pb Zn Fe Au Ag

104.4 108.8 4.4 Core 41 <0.05 <0.05 (2) (2) (2)

108.8 113.8 5.0 do. 20 .97 4.55 34.2 0.05 (3)

113.8 122.6 8.8 do. 65 1.06 .47 55.7 .01 0.48

122.6 129.0 6.4 do. 92 .17 <.05 57.2 .43 .26

129.0 132.6 3.6 do. 75 5.00 <.05 50.8 .03 .10

132.6 138.1 5.5 do. 24 .05 <.05 19.4 .01 (3)

138.1 141.0 2.9 do. 76 .10 <.05 2.2 .05 0

141.0 144.0 3.0 do. 67 .10 <.05 2.7 .03 0

144.0 151.3 7.3 do. 27 .05 <.05 (2) (a) (2) 104.4 108.8 4.4 Sludge - .20 .73 4.3 (3) 0

108.8 113.8 5.0 do. - 1.17 2.27 39.2 (3) 0

113.8 122.6 8.8 do. - .67 .43 56.2 .02 .40

122.6 129.0 6.4 do. - 1.20 .56 55.1 (3) .26

129.0 132.6 3.6 do. - 4.40 .05 48.0 (3) .16

132.6 138.1 5.5 do. - 1.17 .47 27.8 (3) .04

138.1 141.0 2.9 do. - .60 .21 4.3 (2) .05

141.0 144.0 3.0 do. - .70 <.05 11.5 (2) .02

144.0 151.3 7.3 do. - .40 .13 2.3 (3) .01 1Spectrographic analyses of a composite of core samples from 108.8 to 141.0 feet:

Al As Sn Ca Cu Pb Mg A& Zn Cr Fe Mn Ni Si Ti V Mo B

D+ D E D+ E A E F C+ E A E F C E F E E

Legend: Legend (Con.):

A - over 10 percent. E - 0.01 to 0.1 percent.

B - 5 to 10 percent. F - 0.001 to 0.01 percent.

C - 1 to 5 percent. G - less than 0.001 percent.

D - 0.1 to 1 percent.

2No assay.

3Trace.
29

TABLE 12. - Diamond-drill-hole log, hole 4

Location: See figures 5 and 8. Date begun: May 31, 1954.

Elevation of collar: 1,343 feet. Date finished: June 8, 1954.

Depth: 304.2 feet. Core sizes: BX to 10.0 feet.

Dip: -35°. AX to 101.2 feet.

Bearing: N. 770 E. EX to 304.2 feet.

Core

FootaRe recovery, Formation

From To Distance percent

0.0 60.4 60.4 98 Broken, gray to gray-brown metalimestone

with many unoriented calcite veinlets

ranging in width from a hairline to

i inch and many clay-filled fractures of

similar size.

60.4 100.3 39.9 84 Similar metalimestone with more fracturing

but no bleaching or other evidence of

mineralizing solutions. Most intense

fracturing is at 64 feet, 84 feet, 94

feet, 98 feet, and 100 feet.

100.3 107.5 7.2 24 Bleached metalimestone with some ironstained clay.

1107.5 114.8 7.3 22 Gossan zone consisting principally of

iron-stained earthy clay and brown

fragments of altered metalimestone.

114.8 139.3 24.5 47 Broken, gray metalimestone with much iron

stain and some bleaching.

139.3 184.5 45.2 22 Intensely broken, gray metalimestone with

some iron stain on fracture surfaces.

184.5 304.2 119.7 30 Broken, dark-gray metalimestone with little

iron stain and no evidence of mineralizing solutions. Many unoriented fractures make this rock almost impossible

to core.

Analyses data in table 13.

TABLE 13. - Analyses of diamond-drill samples, hole 41

_ _ FootaRe Sample Percent

From To Distance type Core recovery Pb Zn Fe

107.5 109.8 2.3 Core 9 <0.05 0.20 1.7

109.8 111.2 1.4 do. 57 <.05 <.05 1.7

111.2 113.0 1.8 do. 17 <.05 <.05 1.6

113.0 114.8 1.8 do. 17 <.05 .05 4.5

94.1 101.2 7.1 Sludge _.10 .10 4.6

101.2 107.5 6.3 do. _ .10 .10 1.5

107.5 109.8 2.3 do. _ <.05 .10 5.3

109.8 111.2 1.4 do. _ <.05 <.05 2.9

111.2 115.6 4.4 do. _ .10 .05 5.0

lNo assay for Au and Ag.
30

TABLE 14. - Diamond-drill-hole log, hole 5

Location: See figures 5 and 9. Date begun: June 9, 1954.

Elevation of collar: 1,414 feet. Date finished: June 18, 1954.

Depth: 295.0 feet. Core sizes: BX to 15.0 feet.

Dip: -35'. AX to 150.7 feet.

Bearing: N. 79o 30' E. EX to 295.0 feet.

Core

Footage recovery, Formation

From To Distance percent

0.0 15.0 15.0 83 Broken, gray, fine-grained metalimestone with red

and yellow staining on fracture surfaces.

15.0 19.6 4.6 78 Quartz-mica schist in sludge but not recovered in

core, which is similar to core from 0 to 15 feet.

19.6 105.3 85.7 76 Broken, gray, fine-grained metalimestone with red

and yellow iron staining on fracture surfaces and

some small mud-filled fractures.

105.3 111.0 5.7 90 Gray metalimestone with pale-red to light-brown

bands.

111.0 118.3 7.3 97 Gray, fine-grained metalimestone.

118.3 128.3 10.0 64 Quartz-mica schist fragments recovered in sludge

but not in core, which is similar to core from

111.0 to 118.3 feet.

128.3 150.0 21.7 59 Broken, gray metalimestone with many fractures and

small solution cavities. Bleaching is prominent

near some fracture surfaces.

1 2150.0 168.5 18.5 17 Gossan composed principally of red, yellow, and

brown earthy iron oxides mixed with cerussite and

fragments of altered limestone, goethite, hematite, and limonite. Small bands of galena and

traces of other sulfides occur in the solid

fragments.

168.5 215.7 47.2 59 Broken, gray metalimestone with bleaching evident

along some fractures and iron staining on fracture surfaces.

215.7 218.0 2.3 9 Fracture zone with brown mud and some red hematite

fracture filling but no evidence of sulfide minerals and no bleaching of the metalimestone.

218.0 295.0 77.0 65 Broken. fine-grained, gray metalimestone.

'Petrographic analyses of sludge samples from 162.9 to 167.8 feet: Chiefly limonite

with some cerussite; tin and traces of zinc were present, but the minerals could

not be identified.

2 Analyses data in table 15.

TABLE 15. - Analyses of diamond-drill samples, hole 5

Footage Sample Percent Ounces Her ton

From To Distance type Core recovery Pb Zn Fe Au Ag

150.0 155.8 5.8 Core 9 3.00 <0.05 19.9 <0.02 0.02

155.8 159.6 3.8 do. 12 2.90 <.05 55.5 <.02 .54

159.6 168.5 8.9 do. 28 e )

146.8 153.3 6.5 Sludge - .90 <.05 8.2 <.02 .20

153.3 155.8 2.5 do. - 11.20 <.05 37.8 <.02 1.29

155.8 159.6 3.8 do. - 7.10 <.05 50.8 <.02 .60

159.6 162.9 3.3 do. - 4.05 .05 54.6 <.02 .28

162.9 167.8 4.9 do. - 21.10 .17 39.0 <.02 10.02

167.8 170.3 2.5 do. - 2.50 .10 5.8 <.02 1.28

'Sample lost.
31

TABLE 16. - Diamond-drill-hole log, hole 6

Location: See figures 5 and 9. Date begun: June 18, 1954.

Elevation of collar: 1,414 feet. Date finished: June 28, 1954.

Depth: 217.3 feet. Core sizes: BX to 57.0 feet.

Dip: -49°. AX to 138.7 feet.

Bearing: N. 79° 30' E. EX to 217.3 feet.

Core

Footage recovery, Formation

From To Distance percent

0.0 57.0 57.0 74 Broken, iron-stained, gray to red-gray

metalimestone with calcite veinlets and

many small mud-filled fractures.

57.0 107.4 50.4 35 Intensely broken, gray, medium-grained

metalimestone with yellow to red staining on fracture surfaces.

107.4 109.9 2.5 32 Quartz-mica schist fragments in sludge but

core similar to core from 57.0 to 107.4

feet.

109.9 142.9 33.0 66 Broken, gray metalimestone with many small

clay-filled fractures.

142.9 170.2 27.3 63 Broken, bleached metalimestone with yellow

to red clay in many small fractures.

1170.2 185.3 15.1 41 Gossan composed principally of brown to

red earthy iron oxides with clay, altered

metalimestone, hematite, goethite and

limonite.

185.3 217.3 32.0 43 Broken, gray metalimestone with some

bleaching along minor fractures. A clayfilled opening (possibly a solution

cavity) encountered at 197 feet showed

no evidence of mineralizing solutions.

Analyses data in table 17.

TABLE 17. - Analyses of diamond-drill samples, hole 61

Footage Sample Percent

From To Distance type Core recovery Pb Zn Fe

170.2 172.9 2.7 Core 22 0.47 <0.05 50.0

172.9 177.5 4.6 do. 56 .36 <.05 58.5

177.5 179.2 1.7 do. 59 .20 <.05 58.0

179.2 184.0 4.8 do. 27 .78 <.05 54.8

184.0 185.3 1.3 do. 53 .71 <.05 16.6

170.2 172.9 2.7 Sludge - .44 <.05 54.0

172.9 177.5 4.6 do. - .45 .07 57.3

177.5 179.2 1.7 do. - .93 .10 57.9

179.2 184.0 4.8 do. - .48 .10 57.4

184.0 185.3 1.3 do. - .65 .10 40.6

185.3 188.3 3.0 do. - <.05 .05 4.8

188.3 193.4 5.1 do. - <.05 .10 1.1

'No assay for Au and Ag.
32

TABLE 18. - Diamond-drill-hole log, hole 71

Location: See figures 5 and 10. Date begun: June 29, 1954. Elevation of collar: 1,385 feet. Date finished: July 7, 1954.

Depth: 212.4 feet. Core sizes: BX to 65 feet.

Dip: -35°. AX to 212.4 feet.

Bearing: N. 70° E.

Core

Footage recovery, Formation

From To Distance percent

0.0 64.4 64.4 90 Iron-stained, gray to red-gray metalimestone with calcite veinlets and many

small mud-filled fractures.

64.4 68.8 4.4 100 Similar metalimestone with some red hematite and clay in fractures and some

bleaching along fractures.

68.8 84.4 15.6 96 Gray, fine-grained to medium-grained metalimestone with small mud-filled fractures. 84.4 94.7 10.3 84 Broken, gray metalimestone with some

bleaching along fractures.

94.7 98.6 3.9 97 Gray, fine-grained to medium-grained metalimestone.

98.6 106.3 7.7 99 Similar metalimestone with some bleaching

along minor fractures.

106.3 121.2 14.9 89 Broken, dark-gray metalimestone with small

clay-filled fractures.

121.2 125.5 4.3 88 Similarly broken dark-gray metalimestone

with traces of bleaching along minor

fractures.

125.5 136.3 10.8 96 Broken, dark-gray metalimestone. Some

micaceous fragments recovered in sludge

but not in core.

136.3 138.0 1.7 99 Similar metalimestone with traces of

bleaching along fractures.

138.0 212.4 74.4 93 Gray, fine-grained to medium-grained metalimestone with small calcite veinlets and

many small clay-filled fractures. An

open cavity, possibly a solution channel,

was encountered at 169 feet, and a zone

of intense fracturing extended from 200

to 212 feet. There was no gossan material nor evidence of mineralizing

solutions.

lNo samples from this hole were assayed.
33

TABLE 19. - Diamond-drill hole log, hole 8

Location: See figures 5 and 9. Date begun: July 8, 1954

Elevation of collar: 1,334 feet. Date finished: July 22, 1954.

Depth: 430.0 feet. Core sizes: BX to 79.7 feet.

Dip: -50°. AX to 217.9 feet.

Bearing: N. 79° 30' E. EX to 430.0 feet.

Core

Footage recovery, Formation

From To Distance percent

0.0 50.0 50.0 66 Broken, fine-grained, gray metalimestone with few

calcite veinlets and numerous small clay-filled

fractures.

50.0 72.0 22.0 67 Intensely weathered and broken, gray metalimestones

with more numerous small clay-filled fractures.

72.0 79.7 7.7 32 Fracture zone with clay-filled openings over 1 foot

across but no evidence of mineralizing solutions.

79.7 106.0 26.3 81 Broken, fine-grained, gray metalimestone with small

clay-filled fractures.

106.0 184.0 78.0 80 Broken, fine-grained, gray metalimestone with small

clay-filled fractures. Quartz and mica were recovered in the sludge but not in the core.

184.0 233.6 49.6 61 Broken metalimestone with bleaching along fractures

and much iron stain.

233.6 252.0 19.4 82 Broken, fine-grained gray metalimestone with a few

small clay-filled fractures.

252.0 267.4 15.4 82 Broken, bleached metalimestone with considerable

iron stain.

1267.4 269.0 1.6 80 Gossan composed of altered metalimestone partially

replaced by iron oxides but no sulfide minerals.

269.0 272.4 3.4 60 Broken, bleached metalimestone with some gossan

material in fractures.

272.4 368.0 95.6 55 Broken, gray metalimestone with many fractures and

voids. Some fractures and voids are clay filled;

some contain only ice, and some are open. Water

was lost frequently while drilling.

368.0 378.0 10.0 50 Bleached metalimestone with some iron-stained clay

in many small fractures.

378.0 400.0 22.0 49 Broken, gray metalimestone with many ice-filled and

clay-filled fractures.

400.0 430.0 30.0 49 Intensely broken, gray metalimestone with considerable brown clay in fractures but no ice or other

evidence of permafrost. The metalimestone and the

fracture filling is essentially similar to that on

the surface both in original form and degree of

weathering.

Analyses data in table 20.

TABLE 20. - Analyses of diamond-drill samples, hole 8'

Footage Sample Percent

From To Distance type Core recovery Pb Zn Fe

267.4 269.0 1.6 Core 80 0.06 <0.05 6.4

267.4 272.4 5.0 Sludge - .05 .02 4.5

'No assay for Au and Ag.
34

TABLE 21. - Diamond-drill-hole log, hole 9

Location: See figures 5 and 9. Date begun: July 23, 1954.

Elevation of collar: 1,334 feet. Date finished: August 5, 1954. Depth: 395.0 feet. Core sizes: BX to 80.7 feet. Dip: -30°. AX to 205.4 feet.

Bearing: N. 79° 30' E. EX to 395.0 feet.

Core

Footage recovery, Formation

From To Distance percent

0.0 61.0 61.0 71 Broken, fine-grained, gray metalimestone with a few

calcite veinlets and small clay-filled fractures.

61.0 74.9 13.9 67 Similar, broken, fine-grained, gray metalimestone

with more clay-filled fractures; quartz and mica

in the sludge but not in the core.

74.9 88.0 13.1 38 Broken, fine-grained, gray metalimestone with

numerous clay-filled fractures and voids.

88.0 119.8 31.8 76 Broken, gray to red-brown metalimestone with occasional small clay-filled fractures.

119.8 130.5 10.7 64 Broken, gray metalimestone; quartz and mica fragments in the sludge but not in the core. 130.5 205.4 74.9 87 Broken, gray metalimestone with some small clayfilled fractures.

205.4 228.6 23.2 50 Intensely broken, gray metalimestone with many

fractures and voids containing clay, mica,

quartz grains, and ice.

228.6 245.4 16.8 88 Broken, gray metalimestone.

245.4 249.0 3.6 36 Broken, gray metalimestone with several voids.

Sludge contained a large percentage of quartz

and mica mixed with brown, earthy clay. 249.0 290.2 41.2 44 Broken, gray metalimestone with some bleaching

along minor fractures.

290.2 311.6 21.4 74 Broken, gray metalimestone with more intense

bleaching along fracture surfaces.

311.6 316.5 4.9 86 Intensely bleached metalimestone with some gossan

material in fractures.

1316.5 325.6 9.1 40 Gossan zone composed of clay, earthy iron oxides

and altered metalimestone partially replaced by iron oxides but no sulfide minerals.

325.6 330.4 4.8 85 Broken, gray metalimestone.

330.4 342.1 11.7 22 Broken, bleached metalimestone with large voids.

Sludge samples were lost. The color of occasional small amounts of return water indicated

that the voids contained iron oxides. No metallic

minerals were evident in the core.

342.1 395.0 52.9 29 Intensely broken metalimestone with bleaching on

fracture surfaces. Sludge could not be recovered

owing to the porous nature of the rock. The

color of the occasional small amounts of return

water did not indicate the presence of metallic

minerals.

'Analyses data in table 22.
35

TABLE 22. - Analyses of diamond-drill sludge samples, hole 9'

Footage Percent

From To Distance Core recovery Pb Zn Fe

316.5 319.6 3.1 42 <0.05 0.05 3.9

319.6 321.9 2.3 17 <.05 .20 8.0

321.9 323.6 1.7 53 <.05 .20 5.9

323.6 325.6 2.0 50 <.05 <.05 3.7

'No assay for Au and Ag.

TABLE 23. - Diamond-drill-hole log, hole 10

Location: See figures 5 and 11. Date begun: August 6, 1954.

Elevation of collar: 1,491 feet. Date finished: August 20, 1954.

Depth: 291.4 feet. Core sizes: BX to 40.0 feet.

Dip: Vertical. AX to 189.0 feet.

EX to 291.7 feet.

Core

Foota e recovery, Formation

From To Distance percent

0.0 28.0 28.0 71 Intensity broken, gray, fine-grained metalimestone

with some small calcite veinlets and some brown

to yellow stain and clay in small fractures.

28.0 29.0 1.0 0 Mica and clay recovered in sludge.

29.0 179.8 150.8 84 Broken, gray, fine-grained metalimestone with some

small calcite veinlets and some red and brown iron

stain on fracture surfaces.

1179.8 185.2 5.4 40 Gossan zone composed of altered metalimestone, clay,

ice, and earthy iron oxides.

185.2 189.0 3.8 46 Intensely broken and partially bleached metalimestone with some gossan material in fractures.

189.0 206.0 17.0 74 Broken, gray metalimestone with some bleaching

along fracture surfaces.

206.0 242.0 36.0 53 Broken, gray metalimestone.

242.0 248.0 6.0 52 Bleached, altered metalimestone with some ironstained clay in fractures.

248.0 261.0 13.0 81 Broken, gray metalimestone with some bleaching

and iron-staining along fracture surfaces.

261.0 291.7 30.7 46 Intensely broken, dark-gray to nearly black

metalimestone.

'Analyses data in table 24.

TABLE 24. - Analyses of diamond-drill samples, hole 101

Footage _Percent_ Sample 

From To Distance type Core recovery Pb Zn Fe

180.4 185.2 4.8 Core 40 <0.05 <0.05 6.7

179.8 182.1 2.3 Sludge _ <.05 <.05 5.5

182.1 184.7 2.6 do. _ <.05 <.05 5.9

184.7 185.7 1.0 do. _ .05 .05 7.6

185.7 188.2 2.5 do. _ <.05 <.05 3.5

'No assay for Au and Ag.
36

TABLE 25. - Diamond-drill-hole log, hole 111

Location: See figures 5 and 12. Date begun: August 21, 1954. Elevation of collar: 1,316 feet. Date finished: August 31, 1954 Depth: 201.0 feet. Core sizes: BX to 56 feet. Dip: _30'. AX to 136 feet. Bearing: N. 780 E. EX to 201 feet.

Core

Footag recovery, Formation

From To Distance percent

0.0 25.3 25.3 51 Intensely broken, iron-stained, gray

metalimestone.

25.3 27.2 1.9 0 Sludge contained clay, altered metalimestone fragments, and iron oxides. 27.2 43.6 16.4 61 Intensely broken, iron-stained, gray metalimestone.

43.6 45.1 1.5 0 Sludge contained metalimestone fragments and iron-stained clay. 45.1 50.0 4.9 41 Broken, gray metalimestone with a few calcite veinlets and iron-stained fractures. 50.0 53.3 3.3 0 Sludge contained metalimestone fragments

and iron-stained clay. 53.3 83.0 29.7 71 Broken, gray metalimestone with a little

bleaching along fractures.

83.0 83.5 .5 0 Sludge contained metalimestone fragments,

mica, and clay. 83.5 86.0 2.5 72 Broken, gray metalimestone.

86.0 88.0 2.0 0 Sludge contained metalimestone fragments,

mica, and clay. 88.0 103.0 15.0 80 Broken, gray metalimestone.

103.0 107.0 4.0 10 Broken, gray metalimestone in core; clay

and mica in sludge. 107.0 125.0 18.0 72 Broken, gray metalimestone. 125.0 127.0 2.0 0 Sludge contained quartz sand, mica, clay,

and metalimestone fragments. 127.0 156.0 29.0 81 Broken, gray metalimestone with a little

iron staining on fracture surfaces. 156.0 160.0 4.0 45 Bleached metalimestone with some clay and

earthy iron oxides. 160.0 183.0 23.0 77 Broken, gray metalimestone with a little

bleaching along fracture surfaces. 183.0 201.0 18.0 83 Broken, gray to black metalimestone.

'No samples from this hole were assayed.
37

TABLE 26. - Average grade of gossan deposit in diamond-drill

holes 2, 3, 5, and 6

Horizontal Percent1 Ounces

Hole Footage Sample width of Core per ton'

number From To type gossan recovery Pb Zn Fe

DDH-2 97.0 105.0 Core 6.6 11 1.07 0.80 19.4 0.03

DDH-3 108.8 141.0 do. 19.3 58 1.05 .83 41.1 .19

DDH-5 150.0 168.5 do. 15.1 10 2.96 <.05 34.0 .23

DDH-6 170.2 185.3 do. 9.9 41 .52 <.05 52.1

Average DDH-2, 3, 5,

and 6............. Core 12.7 34 1.52 .42 38.3

DDH-2 398.2 105.0 Sludge 5.6 - 1.91 1.70 39.2 .03

DDH-3 108.8 141.0 do. 19.3 - 1.35 .69 42.9 .65

DDH-5 150.0 168.5 do. 15.1 - 9.54 .06 37.3 3.08

DDH-6 170.2 185.3 do. 9.9 _ .53 .07 55.4

Average DDH-2, 3,5,

and 6..... Sludge - - 3.73 .49 43.3

'Weighted only in proportion to the horizontal width represented. Core and

sludge analyses are tabulated separately because little of the soft earthy

material was recovered as core.

2 No assay.

3 Sludge sample 97.0 to 98.2 feet not recovered.

Interpretations

Analyses of the samples from the diamond-drill holes and bulldozer

trenches indicate that the deposit occurs roughly in three zones.

The uppermost zone has traces of bleaching and gossan material is relatively unbroken metalimestones. Diamond-drill hole 7 is entirely within this

zone, which also is exposed in the northwest end of the Foster pit and in

trench 2.

The middle zone is a pod or possibly pipe-like body of gossan that was

formed in broken metalimestone and appears to pitch to the north-northwest at

approximately the local dip of the metasediments--25 to 35 degrees. This body

is exposed in the Foster pit and cut by diamond-drill holes 2, 3, 5, and 6.

An abundance of galena nodules was found in the Foster pit, but no massive

galena was recovered as core and only a few small fragments were found in the

sludge samples. The drill-hole samples contained principally clay, limonite,

goethite, cerussite, anglesite, and quartz in a soft, earthy deposit, interspersed with hard zones of partly replaced silicified metalimestone. Table 26

is a computation of the average grade of core and sludge samples recovered

from this zone.

The third and lowest zone is characterized by intense fracturing, widespread bleaching of the metalimestones, lesser amounts of gossan in apparently

discontinuous openings, and the almost complete absence of sulfide minerals.

Diamond-drill holes 1, 4, 8, 9, and 11 penetrated this zone.
38

LEGEND

Gossan

_ u Relatively unbroken metalimestone with little bleaching

Broken metalimestone with much bleaching Q) Diamond- drill hole ____ % ~~~~Gossan in diamond-drill hole

Scale in feet

FIGURE 13. Vertical Longitudinal Section on A-A, Foster Prospect.

Diamond-drill hole 10 was drilled vertically to determine if the mineral- izing solutions had followed bedding planes or other openings to form deposits extending northward from the outcrop. Little evidence of mineralizing solu- tions and only traces of gossan material were found.

The zonal nature of the deposit and the penetration point of the various drill holes is illustrated in figure 13.

Accessory Metals and Minerals

Gold and Silver

Gold is present in much of the gossan material. The grade ordinarily ranges from a trace to 0.05 ounce per ton. Silver is present in amounts usually ranging from 0.2 to 0.4 ounce per ton per percent lead. Silver usually was more abundant in the less altered samples.
39

Table 27 is a summary of the silver-lead ratios of samples from Foster

pit and diamond-drill holes.

TABLE 27. - Average silver-lead ratio of samples, Foster prospect1

Silver, ounces

Location From To Type Pb, Ag, per ton per

feet feet percent ounces per ton percent lead

DDH-2 .......... 97.0 98.2 Core 1.60 0.04 0.02

DDR-2 .......... 98.2 102.7 Sludge 2.90 .04 .01

DDH-2 .......... 107.2 112.5 do. 2.60 .02 .01

DDH-3 .......... 113.8 122.6 Core 1.07 .48 .45

DDH-3 .......... 129.0 132.6 do. 5.00 .10 .02

DDH-3 .......... 108.8 113.8 Sludge 1.17 _ _ 

DDH-3 .......... 122.6 129.0 do. 1.20 .26 .22

DDH-3 .......... 129.0 132.6 do. 4.40 .16 .04

DDH-3 .......... 132.6 138.1 do. 1.17 .04 .03

DDR-5 .......... 150.0 155.8 Core 3.00 .02 .01

DDH-5 .......... 155.8 159.6 do. 2.90 .54 .19

DDH-5 .......... 153.3 155.8 Sludge 11.20 1.29 .12

DDH-5 .......... 155.8 159.6 do. 7.10 .60 .08

DDH-5 .......... 159.6 162.9 do. 4.05 .28 .07

DDH-5 .......... 162.9 167.8 do. 21.10 10.02 .47

DDH-5 ........ 167.8 ... 170.3 do. 2.50 1.28 .51

Total ....... I - I -_ I _ 72.95 15.17 _

Average: 15.17 = 0.21 ounce silver per ton per percent lead.

72.95

Foster pit:

Sample No. 3 .Channel 9.5 1.40 0.15

Sample No. 4 .do. 22.1 5.68 .26

Sample No. 5 .do. 6.8 2.75 .40

Sample No. 7 .do. 11.6 4.74 .41

Sample No. 8 .do. 25.6 14.90 .58

Total . 75.6 29.47 _

Average: 29.47 = 0.39 ounce silver per ton per percent lead.

75.6

lFoster pit channel samples containing less than 5 percent lead are not

included; however, because of the generally lower grades, all diamond-drill

samples containing more than 1 percent lead are included.

Tin

Tin, in amounts ranging from a trace to 0.3 percent, occurs irregularly

distributed through the gossan at the Foster prospect, apparently associated

with the lead minerals. The tin mineral or minerals could not be isolated or

identified. Analyses are presented in table 28. Tin also occurs with lead

minerals at the Omilak mine (table 31).
40

The discovery of tin in these deposits considerably extends the area of known tin deposition and suggests that tin deposits may be associated with the large granitic intrusives that outcrop to the east.

TABLE 28. - Analysis of samples for tin'

From To Sn, Location feet feet Type percent DDH-2 ....................... 102.7 105.0 Core 0.10 DDH-2 ....................... 98.2 102.7 Sludge .10 DDH-3 ....................... 122.6 132.6 Core .08 DDH-3 ....................... 127.3 129.0 Sludge .08 DDH-5 ....................... 150.0 155.8 Core .09

DDH-5 ....................... 155.8 159.6 do. .06 DDH-5 ....................... 146.8 153.3 Sludge .06

DDH-5 ....................... 153.3 155.8 do. .12 DDH-5 ....................... 155.8 159.6 do. .09 DDH-5 ....................... 159.6 162.9 do. .06

DDH-5 .. , 162.9 167.8 do. .32

DDH-5 ....................... 167.8 170.3 do. .06 DDH-6 .. 170.2 172.9 Core .06

Foster pit:

Sample No. 3................................ _ - Channel .10

Sample No. 4................................ _ - do. .30 Sample No. 5................................ _ - do. .10 Sample No. 7................................ _ - do. .10 Sample No. 8................................ _ - do. .20

1

Sample No. 9................................. -_-Specimen .20 The tin content of samples from diamond-drill holes 1, 2, 3, 5, and 6 and

Foster pit samples 1 through 9 was determined by chemical analyses; only samples having over 0.05 percent tin are listed. Spectrographic analyses of selected specimens indicated that samples containing measurable amounts of lead usually contain at least traces of tin.

Copper

Copper, in amounts ranging from barely perceptable traces to a maximum of 0.1 percent, is distributed throughout the gossan material. However, the only identifiable copper minerals were found in the Foster pit where traces of

copper oxides and small amounts of copper sulfides (principally chalcopyrite)

occur associated with arsenopyrite, pyrite, and quartz as segregations encased in relatively unoxidized massive galena nodules. The copper content of almost all samples was checked, but the results were not tabulated because the grade was uniformly low.

Antimony

The presence of small amounts of antimony in the gossan at the Foster prospect

was verified by chemical and spectrographic analyses, but no visually identifi- able antimony mineral was noted either in the diamond-drill cores or in the
41

surface samples. Analyses are presented in table 29. Stibnite is associated

with galena at the Omilak mine (table 31).

TABLE 29. - Antimony analyses of samples'

Sb,

Location Type percent

DDH-22 . . ........... Core 0.60

Foster pit:

Sample No. 1 ............. Channel .10

Sample No. 2 ............. do. .10

Sample No. 3 ............. do. .30

Sample No. 4 .......... do. .20

Sample No. 5 .do. .20

Sample No. 6 .do. .10

Sample No. 7 .......... do. .20

Sample No. 8 .do. .10

Sample No. 9 .Specimen .20

'The antimony content of samples from diamond-drill holes

1, 2, and 3 and from Foster pit samples 1 through 9 was

determined by chemical analyses; only samples having

over 0.05 percent antimony are listed.

2Core sample from 107.2 to 108.2 feet.

Radioactivity

All drill-hole and surface samples were submitted to routine radiometric

analyses. Results were negative except for some sections of diamond-drill

holes 1, 2, and 3, which have an equivalent uranium content ranging from 0.001

to 0.01 percent. Analyses for these samples are presented in table 30. The

radioactive mineral was not identified.

TABLE 30. - Radiometric analyses of samples

Location From.feet To feet Type eU, percent

DDH-l . ............ 199.7 202.9 Core 0.001

DDH-l . ............ 202.9 205.6 do. .010

DDH-2 . ..................... 91-0 98.2 do. .001

DDH-2 . ............ 107.2 108.2 do. .001

DDH-2 . ............ 107.2 112.5 Sludge .010

DDH-3 . ............ 104.4 106.0 Core .001

DDH-3 . ............ 117.9 118.2 do. .001

DDH-3 . ............ 118.2 119.2 do. .010

DDH-3 . ............ 138.1 141.0 do. .010

DDH-3 . ............ 113.8 116.3 Sludge .010

DDH-3 . ............ 116.3 118.2 do. .001

DDH-3 . ............ 118.2 124.3 do. .010

DDH-3 . ............ 127.3 132.6 do. .001

DDH-3 . ............ 132.6 134.2 do. .010

DDH-3 . ............ 141.0 144.0 do. .010

DDH-3..146.5 151.3 do. .010
42

Miscellaneous Sampling

Omilak Mine

The Omilak mine workings were not accessible for examination or sampling; however, specimens typical of the varied mineral assemblage in the deposit

were obtained and analysed for comparison with the Foster deposit. Descrip- tions and analyses of the samples are in table 31.

TABLE 31. - Analyses of Omilak mine specimens

Specimen data Percent Ounces per ton

No. Description Pb Fe Sb Au Ag

221 Typical specimens of high-grade ore

from shaft dump ..................... 55.2 12.1 1.0 0.13 88.01

222 Specimen from small fracture exposed

in Prospect pit 750 feet southwest

of shaft ............................ .06 3.4 31.7 .05 .19

323 Specimen of high-grade galena from

shaft dump .......................... 71.0 (4) .7 .27 35.80

324 Specimen of stibnite from shaft dump.. 7.5 (4) 32.3 .05 1.70

'Sample locations are shown on figure 4. 2Chemical analyses for copper, tin, and zinc:

Specimen Percent

No. Cu Sn Zn

21 0.15 0.2 0.1

22 <.05 <.05 <.05

a Spectrographic analyses of specimens 23 and 24:

Al Sb As Bi Sn Ca Cu Pb Mg S Fe Mn Ni Si Ti Li

Specimen No. 23 E C- D- F D A G A G D C D E E

Specimen No. 24 D A D- D A E A C D B D F F F C

Legend: Legend (Con.):

A - more than 10 percent. E - 0.01 to 0.1 percent.

B - 5 to 10 percent. F - 0.001 to 0.01 percent.

C - 1 to 5 percent. G - less than 0.001 percent.

D - 0.1 to 1 percent.

4No assay.

Other Prospects

Small fragments of oxidized lead minerals were found at widely scattered

intervals for about 3,500 feet to the south and southeast of the Foster pros- pect. Usually the bedrock source was not apparent, but one small gossan outcrop occurs 3,000 feet S. 600 E. of the Foster prospect (sample 17). The

random distribution of these minerals along the crest and flanks of the same

anticlinal structure suggests that they were derived from smaller deposits
43

similar to the Foster prospect. Analyses of typical fragments are presented

in table 32.

TABLE 32. - Analyses of miscellaneous samples1

Pb,

No. Description percent

217 Selected high-grade specimen from small gossan 3,000 feet

S. 600 E. of Foster pit .. 6.3

218 Float specimen from crest of anticline 2,600 feet S. 220 E. of

Foster pit. (3)

219 Float specimen from crest of anticline 3,500 feet S. 200 E. of

Foster pit. (3)

220 Chip sample of greenstone dike 1,800 feet north of Foster pit.

Dike is 15 to 20 feet wide at the east end and becomes

narrower toward the west.

'Sample locations are shown on figure 4.

2Petrographic analyses:

Sample 17: Limonite and cerussite with some galena.

Sample 18: Cerussite with some associated limonite.

Sample 19: Limonite with a relatively small amount of associated calcite.

A trace of zinc is present but the zinc mineral was not

identified.

Sample 20: An igneous rock that contains altered feldspar with some

serpentine, pyroxene, amphibole, and small amounts of

magnetite, pyrite, chlorite, calcite, biotite, and limonite.

3No assay.
44

BIBLIOGRAPHY

1. BROOKS, ALFRED H., RICHARDSON, G. B., COLLIER, A. J., AND MENDENHALL, W. C. Reconnaissances in the Cape Nome and Norton Bay Regions, Alaska in 1900.

A special publication of the Geological Survey, 1901, pp. 181-218.

2. SMITH, PHILIP S. Investigations of Mineral Deposits of Seward Peninsula.

Geol. Survey Bull. 345, 1907, pp. 245-246.

3. SMITH, PHILIP S., AND EAKIN, HENRY M. Mineral Resources of the NulatoCouncil Region. Geol. Survey Bull. 442, 1909, pp. 345-349.

4. . A Geologic Reconnaissance in Southeastern Seward Peninsula and the

Norton Bay-Nulato Region, Alaska. Geol. Survey Bull. 449, 1911,

pp. 130-133.

5. BROOKS, ALFRED H. Blazing Alaska's Trails. The Caxton Printers, Ltd., Caldwell, Idaho, 1953, pp. 371-372.

6. WEST, WALTER S. Reconnaissance for Radioactive Deposits in the Darby Mountains, Seward Peninsula, Alaska, 1948. Geol. Survey Circ. 300, 1953, 7 pp.

INT. .BU. OF MINES.PGH. *PA. 39 13