R. 1 4346 Sg~~~~~~~m$UE 1948

DEPARTMENT OF THINt~ IO

J. A. KRus, SECRETARY~

BUREAU OF~ MNES

JAMES IPOYD, DifjjcToR

REPORT OF, INVESTIGAT N1S

SAMPLING METHODS AND. RESULTS AT THE

SULLIVAN' CREEK TIN PLCRDEPOSITS

MANSLEY HOT SPRINGS. TOFTY, ALASKA~

U ISBU 73TE

JU~AUAL$~1AA932

by

RQWYt L; Tko*"E ANDW. S. WR
R. I. 4346,

September 1948.

REPORT OF INVESTIGATIONS

UNITED STATES DEPARTMENT OF TEE, INTERIOR - BUREAUT OF MINES

SAMPLIING METHODS AND RESULTS AT THE SULLIVAN CREEK TN PLACER

DEPOSITS, MANLEY HOT SPRINGS, TOFTY, ALASKA_/

By Robert L. Thorneg/ and W. S. Wlright2/

CONTENTS .4~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Page

Introduction and summary . ............................ , .

Acknowledgments........ ............. ..... ......... . . ... 2

Location and accessibility........ ......... . ................ 2

Physical features and climate................................ 2

History and production.. ...... ............. **...*. 3

Water supply..................................... ... 3

Occurrence of deposits ............. 4

Character of deposits............ ........ ............ ........ 5

Sampling.i,...,..,,.,...... .. *.*....*........................: 6

General information ... .............. ........ . 6

Shaft sampling. .. .... . . . . ... ...... .. 6

Sampling horizontally......,. ..... ......... ............. 7

Channel samplee . ... ........... ... .. ....... . 7 -

Surface samples.*............. I ............ . ....... . .... 7

Sampling procedure,.. .. .. ............... *..*. .... * 7

Sampling results...... ....................... ...... *... 8

Bibliography ...... ..... ,...,.,., , . .. 8

ILLUSTRATIONS

Following

Fig. page

1. Sketch of Tofty area, Hot Springs district, Alaska, .. , 2

2. Tofty area, Hot Springs district. ...... ,, . . . 4

3. Sullivan Creek bench pit..... . ..............,...... 8

4. ~Cross sections, Sullivan Creek pit ... 8

5. Cross 5. pit..,................,...,.. Cross sections, sections, Sullivan Creek ) SullivanCree..pi......... ......................... . .... 0 8..

6. Cross sections, Sullivan Creek pit., ... ....... ......... 8

INTRODUCTION AND SUMMARY

Cassiterite deposits on Sullivan Creek in central Alaska were investigated by the Bureau of Mines in the spring of 1943. Gold miners in the area

1/i The Bureau of Mines will welcome reprinting of this paper, provided the

following footnote acknowledgment is used: "Repriinted. from Bureau of

Mines Report of Investigations 4346,"-

2/ Mining engineer, Bureau of Mines, Juneau, AJlaska.

2486
R. I'. 4346

have been recovering cassiterite each season as a byproduct of gold placer

operations. Approximately 300 tons of tin concentrates have boon shipped

from the district.

tin The.deposits wore samplod through trenches and smbil shafts. An average

tin content, f 0.28 pound per cubic yard was indicated..

A detailed description of sampling methods and sample analyses is presented in this report.

AC=OVWLEDGMA TS

This paper is one of many reporting various aspects of the Bureau of

Mines program initiated in Auguqt 1939.by passage of the Strategic Minerals

Act, the'scope of which was greatly expanded by subsequent legislation.

Spe6iell acknowldgmelnt is extended to Cleary Hill Mines Co., who supplied

camp fadilitfes, thawinw equtirent, and.a caterpillar tractor for use in the

conduct of' this examinatiio...

LOCATION AND ACCESSIBILITY.

The'depdsit is about 40 miles, east. of the junction of the Tanana and

Yukon Rivers, longitude 150055' W,. and latitude 650o5? N.., as shown in

figure 1. The nearest settlament.io 11ot.Springs, a village of 50 to 100

people, depending upon the sea on. It.is served by a general store, a roadhouse, and a small commercial airfiold.. -Freight is brought in from the coast

by railroad to Nenana, then by river boat. to Hot Springs, which is connected

with the property by15 miles ofgood.truck road. Winter travel is bya.airplane or&og team. A smallJairf ield. is on the propertyi.

PHYSIC-Al FEATURES AND CLIMATE

The area is part of the Yukon Tanana upland and consists of smooth

rounded ridges that rise from the valley floor of Sullivan and Baker Creeks.

The main stream channels, flanked by wide flood plains and gentle gradients,

range fr6oi 450 to 700 feqtin altitude. North of the tin-bearing placers

Roughtop Mountain risesato.an elevation.of.2,800 feet.

The climate is subarctic,, the winters long and cold and the summers

short but rather warm,. The ground, except for soasonal surface thawing, is

permanently frozen.

The average annual precipitation is about 12 inches .A, 3 inches of which

falls as snow from NQvember to March, inclusive. The snow ranges in depth

from 3 to 4 feet on the level. In placer mining summer precipitation is more

important than spring run-off. The frozen ground prevents any underground

storage; hence, the run-off is very rapid. -

3 r Ellsworth, C. E., and Davenport, R. W., Surface Water Supply of the YukonTarnana Rogion: U. S. Geol. Survey Water-Supply Paper, 342, 1915,

343 pp.

2486 -2-
/ /

IZDGEND ~ ~ <B~~~~~~~~c ~ ~ o ~ ~ ~ ~~~Q. / I' (re~~~~~~~~~~~

@ ToftyGul~ch pit@ ' 0 Sullivan Creek pit Mi/es

Figure 1. - Sketch of Tofty area, Hot Springs district, Alaska.

(From U. S. G. S. Bull. 844(d).)
R. I. 4346

The region supports a sparse growth of spruce, birch, and cottonwood,

the greater part having been cut or burned off du-ring the last 20 years.

Except in timbered areas and natural meadows, the surface is covered with

the usual Alaskan carpet of mosses, brush, and creeping plants, which, to a

degree, regulates the run-off from summer precipitation.. Spruce, the mostwidely distributed tree, attains a diemeter of 2 feet or more in favored

locations. However, most of the spruce stands have been cut in the SullivanPatterson Creek drainage area. At the head of Baker Creek, 15 miles northeast, there is enough timber for camp lumber and mining needs. Wood for fuel

may be obtained 3 miles east of the deposits.

HISTORY AND PRODUCTION

Gold placers were first discovered in this area in the winter of 1906-7.

Considerable drift mining was done on this and nearby creeks during the

following decade. Howell and Cleveland drift-mined the greater part of the

Sullivan Creek pit. Their operation consisted of first thawing and sinking

a shaft through 50 to 100 feet of overlying muck and then thawing 4 feet of

gravel adjacent to bedrock, hoisting it to the surface, and washing it in

elevated washing plants. The method was wasteful, inefficient, and expensive.

The mining costs were $3 to $5 a cubic yard.

The property was later taken over by an English company, who carried on

an extensive drilling program, the results of which are not available.

Tillison and L'Hereux followed stripping and mining by means of a hydraulic

lift at the lower end of the present pit.

This property was purchased by Cleary Hill Mines Co., 250 Pere Marquette

Building, Minneapolis, Minn., in 1935. They have carried on mining and

stripping in alternate years. Water from the head of Sullivan Creek is used

to strip the 50 to 60 feet of muck with the aid of monitors. The 3 to 8 feet

of gravel on bedrock is mined by dragline and elevated sluices. Considerable

money and effort have been expended over a period of years in blocking out

the ore reserves on Sullivan and neighboring creeks, but unfortunately no

record of tin content was kept. Only recently heave gold values been permanently recorded.

. .~~~~~~~~~~/

Gold production from the Hot Springs section in 194Oi / was $518,000, of

which $100,000 was from Sullivan Creek. The tin concentrate shipped by Cleary

Hill Mines Co. in 1940 was accumulated during three mining seasons and

amounted to 15,476 pounds containing 8,350 pounds of metallic tin. In 1941,

6,600 pounds of concentrates containing 3,500 pounds of metallic tin were

shipped, Concurrently, drift-mine operators along the outlying creeks recovered. and shipped several hundred pounds of cassiteritei

WATER SUPPLY

Water is furnished by 7,000 feet of ditch, with intakes on Sullivan and

Quartz Creeks., For the removal of overburden in the Sullivan Creek pit,

4/ Smith, Philip S.J, Mineral Industries of Alaskaa in 1940L: U. S. Geol.

Survey Bull. 933(a), 1942, p. 38.

2486 3 -
R. I. 4346

enough water at a 50-foot head is available for stripping with three to five

nozzles. Water for use at the elevated washing plant is circulated from a

settling pond by means of a 12- by 12-inch Diesel pump.

OCCURBETCE OF DEPOSITS

The following creeksodrain the district progressively from west to east,

and tin is said to occur in their associated placers: Woodchopper Creek,

Deep Creek, Miller Creek, Idaho Gulch, Tofty Creek, Sullivan Creek,.Harter

Guloh, Dalton Gulch, Cache Creek, Ferguson Creek, Gold Basin Creek, and Lower

Killarney Creek.

The zone called the tin belt is about 10 miles long, as shown in figures

1 and 2.

Mt'rtie5/ describes it as follows:

The country rock along this belt is probably more or less

continually mineralized, but no continuous pay streak has been

formed. Instead, a number of small, discontinuous pay streeks

are present whose major directions are normal to the zone of

mineralization. The sites of these pay streaks are the gulches

that drain from the hills to the north, or more commonly the

ground lying along the sides of such gulches. In general,

cassiterite and gold occur together in placers, and where the

cassiterite becomes scarce or-absent the gold content also

drops. The sharpness of the cut-off of these small pay streaks

as they are followed north to the hills is amazing. The limit

of the placer is suddenly reached, and north of this limiting

line no tin and but little gold cen be found. The south line

is less exactly defined, because the ancient gulches draining

southward had a tendency to distribute the gold end tin downstream from the mineralized zone, as in the deposit on Sullivan

Croek.

.MIrtie gives the origin of the placers as follows:

A relatively narrow zone in the country rock was originally mineralized with gold and tin. Where this belt was cut

by streams the gold and tin were eroded and concentrated by

the fluviatile action to form commercial placers, and subsequently these old gravel deposits were deeply buried by silt.

According to Waters:

The lodes were not localized along the present tin belt

but originated mearer to Hot Springs Dome, and the present

S/ Mertie, J. B., Jr., Mineral Deposits of art and Hot Springs

Districts, Alaska: U. S. Geol. Survey Bull, 844(d), 1931, pp. 207-208.

6/ Waters, A. E., Jr., Placer Concentrates of Rampart and Hot Springs

Districts: U. S. Geol. Survey Bull. 844(d), 1931, p. 246.

2486 -4-
/ ,0I0 /00a

.Sca/. in Fuei -90~~

Figure 2. - Tofty area, Hot Springs district. (Source of topography unknown, possibly after

U. S. Geological Survey.)
T IN Ws N iN e\ I 

N j~/V/56 101 iSt V G -. .' \ o .

* f A. **6 B Q ' 98810 so *9C \\*

/25 MIff MIv 7.26 MI5 '/ oa6>96^/5 h M I y A .835 740

44 N0 76 _ \. 2 ao_ A, J/5 0 AL/o. \ S .

O e20s 5.02 eI s# wA Q8s3 i S200 C ~ O a ~iw < \ \ \ g\C t+

ao5 c. 5 '-_I 

ao alI e i % s..O r I

l~~~~~~Dp inFet Uo/ Shafo Number 8 3tJ+SA 

0500i Canne y;;.s. amples

ScalI in F0et C. .

I A I ii 3. Se I a/ \

LEOEN/D /

| ~~~~~~Dcpth in Feet' S haf t Number/ / I ~~~~~~~~~Ohorlzonfol Hleo/ Nao/. I~~~~~~~~~~4 Traensit Station ,5 | ~~~~~~~~~+ 5wrfoce and

I 0 Chonnc/ Sornp/cs /

| _Co~~scl in Feet_ _ t i

Figure 3. - Sullivan Creek bench pit.
R. I. 4346

placers are the result of a reworking of older tin-bearing

gravel laid down by an ancient stream that once flowed parallel to the present site of the tin placers but at a higher

level.

The position of this ancient stream could well have been above the level

of the divide now separating the headwaters of Baker and. Sullivan Creeks.

The present topography suggests the possibility of the Baker-Sullivan Creek

depression being in line with what was once an ancient stream. The specific

gravity of the concentrates at the west end is reported to be lower than that

of the concentrates at the east end of the tin belt. This difference could

have been the result of alluvial transportation from east to west. In addition, the tin belt is at a lower level west of Sullivan Creek. The individual

particles are more rounded than would be expected had their source been along,

or just above, the tin belt. The concentrates in Sullivan Creek are coarser

than rice grains, with no finer particles. This fact suggests selective

reconcentration. However, cassiterite has not been found outside the tin

belt. Placers of the streams that drain from the north are not deeply buried

and have been prospected, whereas south of the tin belt the placers are deeply

buried and have not received so much attention. Unless cassiterite occurs

in considerable quantity, it is usually overlooked by the average prospector.

Possibly the lower aggraded portion of Sullivan Creek contains a large

area of very low grade tin- and gold.-bearing gravels. This ground is wet and

is therefore difficult to prospect by sinking shafts. Moreover, it is deep,

and prospectors have found the values distributed throughout the gravel,

rather than lyingdirectly on bedrock. If mineable values are discovered in

these lower alluvial deposits, considerable time and money would be required

to adequately explore end bring them into production.

CHARACTER OF DEPOSITS

The gravel is principally quarzite but also includes considerable vein

quarz and some phyllite. Pay gravel averages 3 to 10 feet in thickness and

is overlain by 50 to 60 feet of muck. Both the muck and gravels are permanently frozen. The gravels are not cemented ant contain few rocks larger

then 10 inches in diameter. The better concentrations of tin are associated

with gold.

The bedrock of phyllite and pyritized slate is easily cleaned to a depth

of 2 feet. Cassite-ite and gold have not penetrated the bedrock below this

level.

As the gravel approached economic grade it was noted that cassiterite

occurred as fine grains and that the gold-was coarse. Lower values were

represented by a few pebbles of cassiterite and flaky gold; that is, as

values increase, the cassiterite particle size decreases proportionately.

The cassiterite pebbles usually carry quartz inclusions, which are freed as

the pebbles are worn down in size, with concurrent increase in specific

gravity. Cassiterite ranged in size from 1 inch down to thepsize of rice

grains, with virtually no finer particles. The gold, in general, was fine

and flaky and would not yield a high recovery if reworked.

2486 5
R. I. 4346-

Tailing-pile structures reflect the position of contained pay streaks,

and may determine their economic value. For each mining location in the pit

there is a distinct reversal of material. The mining sequence was as follows:

1. Top sediments, sluiced and. piled on bedrock.

2. Barren gravel, sluiced and piled on sediments,

3. Pay gravel containing eome bedrock, sluiced and piled on gravel.

4. A small amount of bedrock containing slight value, sluiced and

piled on pay gravel.

The tailing would be relatively easy to sample if the materials were

entirely true, but as each type was washed it was repiled with a bulldozer,

resulting in a highly erratic distribution of values. In general, the lower

portion of the present tailing, representing that portion of top sediments

sluiced and piled on a bedrock, definitely has no value, However, in certain

places the tailing has been repiled in such a manner that some strata contain

erratic values, enclosed by barren material. This condition is the result of

placing material from several pits into one pile.

After the tailings were piled new drains were dug with a dragline, and

the material was heaped along the sides in irregular cones. Later these

drains were cleared or deepened, and the original cones bordering the drains

were covered with fine, barren sediments.

The gravels are free from pyrite, but the bedrock contains about 0.1

pound a cubic yard. As considerable bedrock is mined. in each section, pyrite

is now found in that 3oneral portion of the tailings containing the better

values. In the event of reworking the tailings by sluicing one might expect

this pyrite to cause some difficulty by clogging the riffles.

SAMPLING

General InformationC

T~e sampling wasc done at temperatures of 350 to 450 below 'ero, with

only about 6 hours of daylight. Under these conditions the efficiency of

the men was very low. Samples froze quickly, and warm cabins were required

in which to pan. Difficulty was experienced in preventing the steam lines

and exterior fittings from freezing. Shafts and gopher holes rapidly' retrned

to their original frozen state and made rethawing frequently necessary. As

the winter, progressdd., more daylight was available, and less severe temperatures were experienced. Everything was covered with snow, and trails had to

be broken with caterpillars or showshoes.

Shaft Sampling

The irregular topography of the pit was not cQnducive to shaft sampling.

Some horizontally deposited gravel piles with flat tops were sampled by shafts.

2486 .6 _
R. I. 4346

The gravel was first thawed with a boiler and steam points, and each successive foot was sampled. The average size of the shafts was 5 by 3 by 10 feet.

Each shaft was sunk through gravel and at least 1 foot of bedrock. No gold

or tin was found in the lower part of the shafts or on bedrock.

Sampling Horizontally

Horizontal cuts were made in sampling piles or conma of tailings.

Gopher holes, 18 inches in diameter'and 6 feet long, wore thawed to cut the

internal structure of the coned piles. These holes were started midway up

the pile, and each linear foot was sampled separately.

Channel Samples

Channel samples, 4 by 6 inches, wore cut in vertical faces along roads

and drains.

Surface Samples

Surface samples were taken where no other type of sampling was practi.-

cable. These were cut as shallow holes in the surface of piles.

Sampling Procedure

Shaft end gopher-hole samples were removed in the thawed state. Surface

and chlanel samples were cut from frozen gravels. When taken, each sample

filled a sample bucket having a capacity of 1,900 cubic inches. It was determined that shaft and gopher-hole samples represented 0.95 cubic feet in place,

while surface and channol samples equaled 0.67 cubic feet in place. The

average weight of material was 135 pounds a cubic foot in place. The following method was used to determine the ratio between the quantity of thawed

gravel and that of gravel in place: A number of shallow holes were thawed

within a small area; the gravel was removed and measurcd, The excavation

was then filled with a measured volume of water. This quantity was corrected

for seepage during the measuring period by noting the length of the measuring

period, allowing the water to stand an additional equal period of time, and

then adding enough water to again fill the hole. The latter quantity equals

the amount of seepage and waa;subtracted from the original water me asurement

to give the volume of the, excavation.

Thawed samples freoze rapidly on being cut and ares difficult to wash.

To facilitate panning, all samples were panned as rapidly as taken.

A few samples were washed by rocker, but the coarse particles of

cassiterite remained in the hopper and were difficult to distinguish from

associated gravels, The rocker was soon discarded, end all samples were

panned. Two panners were employed; each cut wood, melted snow, and panned

6 cubic feet of samples a day. Each evening samples were collected to be

cleaned and weighed at the office, at which time the gold and tin were

separated.

2486 7 -
R. I. 4346

SAMPLING RESULTS

Sample results ranged between wide limits. The location and metal

content of Sullivan Creek samples are shown in figures 3, 4, 5, and 6.

Figure 2 shows the location of samples in the upper part of the block,

where the highest tin content was found.- A summary of sampling results

is shown in table 1.

TABLE 1. - Grade pf Sullivan Creek tailing deposit

Tin, pound Gold, ounce

Block poer cubic yard per cubic yard

I.............. . ......... 0.2 O.002

II .*,, .* . 589 .0003

III ...... , .285 .C014

IV. . .' .* . . 382 . .0017

V.0 ... . . ......... 613 .0020

VI .............. .260 .0021

VI, ................. . .27 . 00°-2

IX ... .......... .203 .0003

X , ........ . . .. .. 043 .0014

XI . . . . . ........ .... .082 .0038

Average. ....... 0.241 0.0015

Upper part of small block

Parts of .

IV, V, and VI.... .777 .0028

It appears that the recovery of tin from gold placer mining has been

about 0.04 pound a cubic yard. This, added to the average t-in content of

the tailing, gives an indicated original content of 0.28 pound tf tin a

cubic yard.

BIBLIOGRAPHY

1 EAKIN, HWNY M. A Geological Reconnaissance of a Part of the Rampart

Quadrangle, Alaska, U. S. Geol, Survey Bull. 535k 1913, 38 pp.

2. MERTIE, J. B., JR. Mineral Deposits of the Rampart and Hot Springs

District, Alaska. U, S. Geol. Survey Bull. 844(d), 1931, pp. 207-208.

3. WATERS, A; E. JR. Placer Concentrates of Rampart end Hot Springs

District.. U. S. Geol. Survey Bull. 844(d), 1931, p. 246.

4. DOHENY, L. C. ;Placer Evaluation in Alaska. Ding. and Min. Jour.,

December 1941..

5. SMITH, PHILTP S. M~ineral Industry of Alaska in 1940. U. S. Geol.

Survey Bll. 933(a), 1942, p. 38

6. ELLSWORTH, C. BE., AND DAVENPORT, R, W., Surtace Watel Supply of thp

Yukon-Tanana Region, Alaska. U. S. Geol. Survey Water Supply

Paper 342, 1915, 34 rpp.

2486 -8_
650' Ho 50 /oo /50

650 t _ h A/orizon/o/ ' Scoke in Feet

640' -Sec. A 86/1 A

/006 - ~~~~~~~~~~~ -~~~~~~~VerliCO/ SCOle in7 Fee,'

< Droin ~ 7 - A s~rnt _ ; -_ hTin content In pounds o cublc Jar

630' -- s -- $ ffi _ 2 asS Gol. 60/d contenl in ounces o cubkc yord

\ 3- _ _ 'JS K2 - I _ -

\ Stri~~~~~~~~~~~~~~~~~~~~5-pped Virgin Oro/und /

Au- 61Al - -

6¢0' \ SeC. C 72 2b2 --

620 6 6

DraFg 4. -u Cro s s, Aul 1 C A Au 1.-Crs Aiur sectons Sulva rekpt
6.3- ~ ~ ~ ~ ~ 6

640/ 02 - 3 aZ2 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~6 0.3- _83

\ ec. G rsr- \~~ ~ ~~~~~~~~~~~~~~~~~~~ 50 S /00 /50

630 \ j _ I _ _ / \ I ~~~~~~~~~~~~~~h'or/zonta7/ Scale in feet \30' / \0 30

Vexl Scale in FeV / el\

620v to 5 § jX'5 Au 0.0s~~~~~~~tI Ha7n con/ent inposunds a cubic yrd

Z0 7 a1 Au . 4 an a/ ~~~~~~~~~~Go/d con/enf in ounces a cubic yard .Z

6/0'

Figure 5. - Cross sections, Sullivan Creek pit.
Au

-9- 640' \ f , Sr ^! i _t

Sec. W_

I ,52 //8/ 6S

\~~ II ~~ 

\~~~~ I'N / a1-I

t3 /z/o /vSec.cJ

Tn o cont.nt5n~oounds cub/cya d

H01 Fc, u11 i/7 alCekp re6. 91 ao3l.6 Au arssscmiod, zno50 le/00 FetSIA00

Vertfijal SCale it, Feet

7ln Content d/npounc.' a cubic yard 65oAio ~f~See a Au - 6

Go/d content ,'7 ounces a cubic yard A'ock- S-OpWe

Au 003T

Figure 6.- Cross sections, Sullivan Creek pit.