BLT Prospects, Valdez Creek Mining District, Matanuska-Susitna Borough, Alaska, USAi

Regional Level Types
BLT Prospects	Group of Prospects
Valdez Creek Mining District	Mining District
Matanuska-Susitna Borough	Borough
Alaska	State
USA	Country

Location: 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.
Geology: 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 volcanoclastic 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 The arsenopyrite-rich veins probably correlate with the Upper Cretaceous veins at the Golden Zone mine (unpublished report by Addwest Minerals International Ltd., 1997).
Workings: Underground work encountered the Blind Vein in the 1970's. 19 drill holes (totalling 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).
Age: Late Cretaceous and younger.
Alteration: Clays, ankerite/calcite, and quartz are the dominant alteration assemblages in the mafic dikes.

Commodities (Major) - Ag, Au; (Minor) - Cu, Pb, Zn
Development Status: None
Deposit Model: Polymetallic vein (Cox and Singer, 1986; model 22c)

Other Databases

Link to USGS - Alaska:	HE044

Other Regions, Features and Areas containing this locality

References