Little Clearwater Creek

Occurrence, Probably inactive

Commodities and mineralogy

Main commodities Au
Other commodities Ag; Hg; W
Ore minerals cinnabar; gold; scheelite
Gangue minerals magnetite

Geographic location

Quadrangle map, 1:250,000-scale MH
Quadrangle map, 1:63,360-scale A-6
Latitude 63.0992
Longitude -146.8159
Nearby scientific data Find additional scientific data near this location
Location and accuracy The Little Clearwater Creek placer extends from an elevation of about 3,000 feet near the Denali Highway upstream to 3,700 feet in section 33, T. 20 S., R. 5 E., Fairbanks Meridian. The location for this record is at an elevation of 3,300 feet, just below where the creek leaves the mountains and enters a broad flood plain. The occurrence corresponds to placer locality A32 of Kurtak and others (1992).

Geologic setting

Geologic description

The lower course of Little Clearwater Creek drains bedrock composed mainly of metabasalt of Nikolai Greenstone of Late Triassic age. In upper Little Clearwater Creek, diverse sedimentary, volcanic, and metamorphic rocks are juxtaposed by a series of low-angle thrust faults (Nokleberg and others, 1991). The thrust-faulted rocks are mineralized at several places, including at MH048, MH049, and MH056, thus furnishing potential source rocks for the placer deposit in lower Little Clearwater Creek (Clautice and others, 1989; Kurtak and others, 1992). The lode deposits in the upper course of Little Clearwater Creek are enriched in tungsten and mercury, trace elements that are found downstream in the placer deposits.
Seven samples of alluvium were collected in lower Little Clearwater Creek for placer evaluation (Kurtak and others, 1992, table A42). All contained visible particulate gold. Samples at four sites contained 0.001 ounce of recoverable gold per cubic yard. Sample 3142 contained 0.015 ounce gold per cubic yard. Concentrate samples contained as much as 2.4 parts per million (ppm) silver; all were enriched in tungsten. Sample 1869 contained 3,950 ppm tungsten, 379 ppm mercury, and 325 ppm arsenic, in addition to 0.001 ounce of recoverable gold per cubic yard. The concentrate probably contained scheelite, a tungsten mineral known at upstream site MH048, and possibly cinnabar (mercury sulfide).
Geologic map unit (-146.81815852254, 63.0987586368855)
Mineral deposit model Placer Au (Cox and Singer, 1986; model 39a).
Mineral deposit model number 39a
Age of mineralization Holocene.

Production and reserves

Workings or exploration Tammany Mining Company staked the Little Clearwater Creek claims in 1979 and subsequently dug a number of test pits along the creek. The U.S. Bureau of Mines collected a series of placer samples along the creek that contained as much as 0.015 ounce of recoverable gold per cubic yard; concentrate samples contained as much as 3,950 parts per million (ppm) tungsten and 379 ppm mercury (Kurtak and others, 1992).
Indication of production None

Additional comments

Little Clearwater Creek has moderate potential as a placer gold deposit (Kurtak and others, 1992); the placer possibly could produce tungsten and mercury as byproducts.

References