Unnamed (west of the terminus of Eureka Glacier)

Occurrence, Active

Commodities and mineralogy

Main commodities Cu; Ni
Other commodities Pd; Pt
Ore minerals chalcopyrite; pyrrhotite
Gangue minerals serpentine

Geographic location

Quadrangle map, 1:250,000-scale MH
Quadrangle map, 1:63,360-scale B-5
Latitude 63.2876
Longitude -146.3695
Nearby scientific data Find additional scientific data near this location
Location and accuracy This occurrence is at an elevation of about 3,600 feet at the west edge of the terminus of Eureka Glacier (as shown on the 1951 [rev. 1978] edition of the Mount Hayes B-5 topographic map). The occurrence is in the NE1/4NE1/4 section 10, T. 19 S., R. 7 E., Fairbanks Meridian.

Geologic setting

Geologic description

This occurrence is in the westernmost exposure of the Fish Lake ultramafic complex, a large layered lopolith of Late Triassic age considered to be comagmatic with the Upper Triassic Nikolai Greenstone (Nokleberg and others, 1991). This occurrence consists of sulfide minerals disseminated in the ultramafic complex. Chalcopyrite and pyrrhotite form about 5 to 7 percent of the olivine-clinopyroxene wehrlite. The wehrlite is about 100 feet stratigraphically below locally pegmatitic gabbro. Grab samples of sulfide-bearing wehrlite contained as much as 1,180 parts per million (ppm) copper, 1,650 ppm nickel, 58 parts per billion (ppb) palladium, and 50 ppb platinum (W.T. Ellis, unpublished data, 1996).
Geologic map unit (-146.371763903831, 63.287173921929)
Mineral deposit model Ni-Cu-PGE in differentiated mafic-ultramafic sill.
Age of mineralization Late Triassic, synchronous with emplacement of the mafic-ultramafic rocks.
Alteration of deposit The wehrlite is weakly serpentinized.

Production and reserves

Workings or exploration The occurrence is covered by active Fort Knox Gold Resources claims (W.T. Ellis, unpublished field notes, 1996).
Indication of production None