BLT

Prospects, Active

Commodities and mineralogy

Main commodities Ag; Au
Other commodities Cu; Pb; Zn
Ore minerals arsenopyrite; chalcopyrite; galena; sphalerite; tetrahedrite
Gangue minerals ankerite; calcite; marcasite; quartz; sericite

Geographic location

Quadrangle map, 1:250,000-scale HE
Quadrangle map, 1:63,360-scale A-6
Latitude 63.213
Longitude -149.651
Nearby scientific data Find additional scientific data near this location
Location and accuracy The BLT prospect is at an elevation of about 3,650 feet on the west bank of the head of Bryn Mawr Creek, a northeast-flowing tributary of the West Fork Chulitna River. The map site is on the east edge of sec. 4, T. 20 S., R. 11 W., of the Fairbanks Meridian. Access is via dirt road from Colorado Station along the north side of the West Fork Chulitna River to the junction with Bryn Mawr Creek. The road crosses the West Fork Chulitna River and climbs southwesterly to the Golden Zone mine (HE043), which adjoins the BLT prospect on the north. The location is accurate to within 1,000 feet.

Geologic setting

Geologic description

BLT is the name given to the prospect that includes the Blind, Little, and Tunnel veins near the Golden Zone mine (HE043) (C.C. Hawley, oral communication, 1999). The veins and a strongly altered mafic dike are in a shear zone that defines the southeast margin of the Golden Zone porphyry. The shear zone and mafic dike cut Triassic redbed sandstone, conglomerate, limestone, and volcaniclastic rocks. The shear zone-dike (BLT zone) also cuts the quartz-biotite porphyry associated with the Golden Zone breccia pipe. The BLT prospect consists of early, arsenopyrite-rich quartz veins, followed by quartz-carbonate-sulfide veins, stockwork zones, and massive sulfide lenses. The veins are colloform and banded, indicating an epithermal depositional environment. Sulfide phases in the BLT differ from those in the Golden Zone, in that they contain more pyrite and marcasite, more lead and zinc, and less copper. Only the younger, sulfide-quartz-carbonate veins that locally cut the arsenopyrite-rich veins contain free gold. The arsenopyrite-rich veins probably correlate with the Upper Cretaceous veins at the Golden Zone mine (unpublished report by Addwest Minerals International Ltd., 1997).
Geologic map unit (-149.653291647366, 63.2125259663222)
Mineral deposit model Polymetallic vein (Cox and Singer, 1986; model 22c)
Mineral deposit model number 22c
Age of mineralization Late Cretaceous and younger.
Alteration of deposit Clays, ankerite/calcite, and quartz are the dominant alteration assemblages in the mafic dikes.

Production and reserves

Workings or exploration Underground work encountered the Blind Vein in the 1970s. Nineteen drill holes (totaling over 6,000 feet) have been completed up to the present (1999), along with widespread trenching and soil geochemistry grids. Closely-spaced helicopter aeromagnetic and EM geophysical surveys have been flown over this prospect. The State of Alaska flew a more widely-spaced helicopter aeromagnetic survey in 1996 (Burns, 1997).
Indication of production None

References