Occurrence, Active

Commodities and mineralogy

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

Geographic location

Quadrangle map, 1:250,000-scale MH
Quadrangle map, 1:63,360-scale A-5
Latitude 63.2477
Longitude -146.208
Nearby scientific data Find additional scientific data near this location
Location and accuracy The BM-75 occurrence is at an elevation of about 4,300 feet in the headwaters of a north-flowing tributary of upper Eureka Creek and is in the SE1/4SE1/4 section 21, T. 19 S., R. 8 E., Fairbanks Meridian.

Geologic setting

Geologic description

The BM-75 occurrence is hosted by the Fish Lake mafic-ultramafic intrusive complex, which is of Late Triassic age and believed to be a lopolithic feeder of the Nikolai basalt flows (Nokleberg and others, 1991). The occurrence is in a pod of serpentinized peridotite in a gabbroic unit of the third magmatic cycle of the Fish Lake complex. The pod of serpentinized peridotite contains a few percent disseminated pyrrhotite, chalcopyrite, pentlandite, and magnetite (Foley, 1992; Foley and others, 1989) A grab sample contained 70 parts per billion (ppb) palladium and 70 ppb platinum (U.S. Bureau of Mines, unpublished data, 1985).
Geologic map unit (-146.210258482266, 63.2472754733795)
Mineral deposit model Ni-Cu-PGE in differentiated mafic-ultramafic sill.
Age of mineralization Late Triassic, the age of the host rock.
Alteration of deposit The peridotite is serpentinized.

Production and reserves

Workings or exploration The occurrence is on active Fort Knox Gold Resource claims.
Indication of production None