Lower Caribou Creek; Lee bench Mines, Kantishna Mining District, Denali Borough, Alaska, USAi

Regional Level Types
Lower Caribou Creek; Lee bench Mines	Group of Mines
Kantishna Mining District	Mining District
Denali Borough	Borough
Alaska	State
USA	Country

Caribou Creek is in Denali National Park and Preserve.
Location: Lower Caribou Creek (Cobb, 1980 [OFR 80-363]) is the part of Caribou Creek below the Kantishna Hills. The lower Caribou Creek placer deposit is about 3 miles long. It extends from the NW1/4 of section 7, T. 15 S., R. 17 W., Fairbank Meridian, to the midpoint of sections 31 and 36 on the R. 17 W.-18 W. township line. The location marks the north limit of placer tailings shown on the 1954 (rev. 1978) edition of the Mt. McKinley C-2 quadrangle topographic map. It approximately coincides with number 47 of Cobb (1972 [MF 366]), placer resource block C-2 of Thornsberry, McKee, and Salisbury (1984, fig. K-3), and the mined area shown by Hawley and Associates (1978).
Geology: Lower Caribou Creek has a gradient of about 150 feet per mile. It flows through a broad alluvial valley cut into bedrock of the Birch Creek Schist (Levell, 1984, v. 1 and 2; Bundtzen, 1981). The broad terrace on the east side of lower Caribou Creek is called the Lee bench. The lower Caribou Creek placer deposit consists of 4 to 7 feet of subrounded to rounded gravel on top of weathered, clayey, bedrock. The lowest 1 to 2 feet of gravel is weakly cemented. The gold was mainly in the gravel, but about 1/2 foot of bedrock was auriferous and was mined with the gravel. Most of the gold was fine and flaky, a little was nuggety, and its fineness was about 680. The gold was weakly to moderately stained with iron and manganese oxides. Garnet and magnetite were abundant in the concentrate. Grade, calculated from production, was about 0.027 ounce (0.019 fine ounce) of gold per cubic yard (Levell, 1984, v. 2, operation 6). The nature of the Lee bench placer is uncertain, as most of it has not been tested. The deposit mainly is on schist bedrock, and consists of 4 to 10 feet of gravel overlain by 2 to 3 feet of frozen muck (Levell, 1984, v. 2). At an exposure about 1/2 mile downstream from the schist-floored deposit, 10 to 15 feet of gravel lies on false bedrock of quartz-rich, Tertiary(?) sand. Spoils from nearby pits include blue clay that possily is possibly Tertiary lake sediment. The average grade of the Lee bench deposit, calculated from ground mined and gold recovered in 1975, is 0.026 ounce (0.019 fine ounce) of gold per cubic yard.
Workings: More than a mile of lower Caribou Creek was mined prior to 1951-52, probably mainly by dragline in about 1940. At least one operation worked the lower Lee bench in 1975 (Levell, 1984, v. 2; Bundtzen, Tosdal, and Smith, 1976). The alluvial deposit in and near the modern valley was mined in 1983 and probably 1984.
Age: Holocene and late Pleistocene; some deposits may be as old as late Tertiary.
Production: Total gold production is uncertain. An operator in 1975 recovered about 70.5 ounces. An efficient 1983 operation had recovered more than 1000 ounces before the end of August, and was in production when visited by Levell (Levell, 1984, v. 2). Based on the grade of mined material, and on the extent of the mining, the lower Caribou placer deposit has probably produced at least 5000 ounces of gold.
Reserves: Resource block C-2 (Levell, 1984) contains about 840,000 cubic yards of alluvium on claimed ground (1983) in or adjacent to modern lower Caribou Creek. The gold resource at the calculated grade of 0.019 fine ounce of gold per cubic yard is 15,960 ounces. There is a much larger, but less quantified, resource on the Lee bench. The estimated volume of claimed (1983) gravel in the bench deposits is 4,300,000 cubic yards. Using the grade calculated from 1975 production from the bench (0.019 fine ounce of gold per cubic yard), the resource is about 81,700 ounces of gold.

Commodities (Major) - Au; (Minor) - Ag
Development Status: Yes; small
Deposit Model: Au-PGE placer (Cox and Singer, 1986; model 39a).

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Link to USGS - Alaska:	MM035

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