FL Feeder

Prospect, Active

Commodities and mineralogy

Main commodities Cu
Other commodities Ag; Au; Ni
Ore minerals chalcopyrite; pyrite

Geographic location

Quadrangle map, 1:250,000-scale MH
Quadrangle map, 1:63,360-scale B-5
Latitude 63.3049
Longitude -146.306
Nearby scientific data Find additional scientific data near this location
Location and accuracy The FL Feeder prospect is at an elevation of about 4,700 feet one mile east of the toe of the Eureka Glacier, in the SE1/4SE1/4 section 36, T. 18 S., R. 7 E., Fairbanks Meridian. It is in a tributary to locally named Landslide Creek (see figure 3 of Rose, 1966 [ADMM GR 20]).

Geologic setting

Geologic description

The rocks in the area of the FL Feeder prospect occur within a body of diorite, quartz diorite, and gabbro that intrude andesite, dacite, and graywacke (Rose, 1966 [ADMM GR 20, figure 3]). A quartz monzonite crops out to the south of the gabbro body. The gabbroic body is possibly a sill (Nokleberg and others, 1991).
The FL Feeder prospect consists of chalcopyrite- and pyrite-bearing hornblende-biotite gabbro breccia that trends southeasterly and cuts the enclosing gabbro at a high angle. The breccia is intensely amphibolitized and contains large porphyroblastic biotite crystals. The chalcopyrite and pyrite occur in clasts and matrix of the breccia. Samples of breccia assay as much as 1.1 percent copper, 0.1 percent nickel, 10 parts per million silver, and 192 parts per billion gold (W.T. Ellis, written communication, 1996).
Geologic map unit (-146.308264568299, 63.3044757113299)
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 Secondary amphibole and biotite are strongly developed in the FL Feeder breccia.

Production and reserves

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