East Fork Maclaren River

Prospect, Inactive

Commodities and mineralogy

Main commodities Au
Other commodities Ag; PGE
Ore minerals gold; pge

Geographic location

Quadrangle map, 1:250,000-scale MH
Quadrangle map, 1:63,360-scale B-5
Latitude 63.2681
Longitude -146.4426
Nearby scientific data Find additional scientific data near this location
Location and accuracy This placer prospect extends from elevations of about 3,000 to 3,350 feet on the East Fork Maclaren River, about 2 miles west of the outwash plain of the Eureka Glacier. The prospect is near the center of section 17, T. 19 S., R. 7 E., Fairbanks Meridian. The site corresponds to the approximate midpoint of placer locality A14 of Kurtak and others (1992). This is Kardex site number KX86-206 (Heiner and Porter, 1972).

Geologic setting

Geologic description

The upper East Fork Maclaren River below Eureka Glacier cuts tuffaceous rocks of Triassic age. Lowermost Eureka Glacier appears to cross a dunite-rich zone of the Fish Lake mafic-ultramafic complex about a mile wide (Stout, 1976, plate 1). Eureka Glacier trends nearly north-south; the uppermost East Fork Maclaren River trends about east-west; consequently it is uncertain if the glacier scoured the upper East Fork and removed any placer concentrations of pre-glacial age.
The U.S. Bureau of Mines collected three pan-concentrate samples from this placer (Kurtak and others, 1992, table A14). All contained particulate gold. Sample 1036 contained 0.0019 ounce of recoverable gold per cubic yard. Platinum-group metals were not determined. Sample 1576 (bank gravel) had 1 fine and 30 very fine gold flakes; a pan-concentrate sample assayed 40 parts per billion (ppb) platinum, 6 ppb palladium, and 1 part per million silver.
Geologic map unit (-146.444863453328, 63.2676715936287)
Mineral deposit model Placer Au-PGE (Cox and Singer, 1986; model 39a).
Mineral deposit model number 39a
Age of mineralization Holocene.

Production and reserves

Workings or exploration
The Three Bears claims were staked along the East Fork in 1979-80. From 1981 to 1986, claims were tested by backhoe test holes and by suction dredging. During its investigation of the Valdez Creek district, the U.S. Bureau of Mines collected three placer samples (Kurtak and others, 1992), one of which contained 0.0019 ounce of recoverable gold per cubic yard. Another sample contained 40 parts per billion (ppb) platinum and 6 ppb palladium.
The occurrence is now covered by claims owned by MAN Resources (W.T. Ellis, written communication, 2001).
Indication of production None

Additional comments

The presence of gold and platinum-group metals suggests that more testing is warranted.

References