|Quadrangle map, 1:250,000-scale||HE|
|Quadrangle map, 1:63,360-scale||A-6|
|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 descriptionBLT 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 The arsenopyrite-rich veins probably correlate with the Upper Cretaceous veins at the Golden Zone mine (unpublished report by Addwest Minerals International Ltd., 1997).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.|
|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|
Berg, H.C., and Cobb, E.H., 1967, Metalliferous lode deposits of Alaska: U.S. Geological Survey Bulletin 1246, 254 p.
Hawley, C.C., and Clark, A.L., 1974 (1975), Geology and mineral deposits of the upper Chulitna district, Alaska: U.S. Geological Survey Professional Paper 758-B, p. B1-B47, 2 plates, scale 1:12,000 and 1:48,000.
Hawley, C.C., and others, 1978, Mineral appraisal of lands adjacent to Mt. McKinley National Park, Alaska. Contract No. JO166107: U.S. Bureau of Mines Open-File Report 24-78, 274 p., 12 sheets.
Mulligan, J.J., Warfield, R.S., and Wells, R.R., 1967, Sampling a gold-copper deposit, Golden Zone mine, south-central Alaska: U.S. Bureau of Mines Open-File Report 9-67, 59 p.
Ross, C.P., 1933, The Valdez Creek mining district, Alaska: U.S. Geological Survey Bulletin 849-H, p.425-468.
|Reporters||N. Van Wyck (Stevens Exploration Management Corporation)|
|Last report date||4/7/2000|