Foster

Prospect, Probably inactive

Commodities and mineralogy

Main commodities Ag; Pb; Zn
Other commodities Au
Ore minerals chalcopyrite; galena; pyrite; sphalerite
Gangue minerals calcite; quartz

Geographic location

Quadrangle map, 1:250,000-scale DE
Quadrangle map, 1:63,360-scale D-3
Latitude 54.8294
Longitude -132.7078
Nearby scientific data Find additional scientific data near this location
Location and accuracy Roehm (1942) described the geology of this prospect in considerable detail but his location is ambiguous. It most likely is at an elevation of about 400 feet, close to the ridge between upper Coning Inlet and Seclusion Lake, near the center of the west boundary of section 22, T. 81 S., R. 85 E., but it may be a mile or more from there. The prospect was found with difficulty in 1952 by Glover (1954 [PE121-4]), but he does not provide an unambiguous location. In recent years, several other geologists (Maas and others, 1991; Hedderly-Smith, 1999) have unsuccessfully searched for the Foster prospect in heavily overgrown terrain that has been disturbed by logging.

Geologic setting

Geologic description

The rocks in the vicinity of the likely location of the Foster prospect are pre-Ordovician dacitic metavolcanic rocks, marble, and argillite (Gehrels, 1991). Roehm (1942) describes the prospect as a quartz lens or vein about 170 feet long and 12 to 15 feet thick. The lens or vein strikes N42W and dips 75E; it is parallel to the schist, limestone, and argillite host rocks and contains numerous limestone fragments. The schist footwall is highly mineralized with small quartz lenses. The surface exposure of the vein appears barren due to surface oxidation, but a 10-foot-deep trench exposed abundant pyrite, chalcopyrite, sphalerite, and galena. Two 5-foot channel samples showed nil to 0.02 ounce of gold per ton, 0.10 to 0.30 ounce of silver per ton, 0.47 to 1.20 percent copper, up to 0.55 percent lead, and 0.18 to 1.22 percent zinc. The prospect was reexamined by Glover (1954 [PE 121-4]), but his oxidized surface samples contained little metal.
Geologic map unit (-132.709463745833, 54.8290546192676)
Mineral deposit model Stratiform base metal deposit or volcanogenic massive-sulfide deposit.
Age of mineralization Pre-Ordovician or younger.
Alteration of deposit Much surface oxidation that has almost totally leached the sulfides.

Production and reserves

Workings or exploration A 10-foot-long trench apparently has been obliterated by forest growth and logging.
Indication of production None

Additional comments

The subsurface rights to the land in the vicinity are held by the Sealaska Corporation.

References