Unnamed (east valley wall of Kuskokwim River) (ARDF #SM039) As, Mo, Pb

Unnamed (east valley wall of Kuskokwim River)

Occurrence, Inactive

Commodities and mineralogy

Main commodities	As; Mo; Pb
Other commodities	Hg; W
Ore minerals	arsenopyrite; unspecified sulfides
Gangue minerals	quartz

Geographic location

Quadrangle map, 1:250,000-scale	SM
Quadrangle map, 1:63,360-scale	C-7
Latitude	61.64208
Longitude	-158.25329
Nearby scientific data	Find additional scientific data near this location
Location and accuracy	This occurrence is at the summit of a prominent northeast-trending ridge east of the Kuskokwim River near the eastern boundary of the Sleetmute C-7 quadrangle. The occurrence is at an elevation of about 800 feet and about 0.6 mile north-northeast of the center of sec. 24, T. 18 N., R. 50 W., of the Seward Meridian. The location is accurate.

Geologic setting

Geologic description This unnamed occurrence consists of thin, conjugate quartz -sulfide veins in a granite porphyry sill. This intrusion has has a 40K/40Ar biotite age of 71.2 Ma (Bundtzen and others, 1998). The conjugate veins, which strike N75E and N55W and dip steeply to vertically, are 0.4 to 1.1 inches thick. The veins consist of quartz with selvages of mica, 0.5 to 1.0 percent arsenopyrite, and other unidentified sulfides. The mineralized area totals about 550 square feet in size and within that area there is an average of about 1 vein per foot. Several grab samples contained up to 148 parts per million (ppm) lead, 52 ppm molybdenum, 2.0 ppm tungsten, and 1.4 ppm mercury (Bundtzen and others, 1998).
Geologic map unit	(-158.25566823045, 61.64137543654)
Mineral deposit model	Polymetallic vein (Cox and Singer, 1986; model 22c).
Mineral deposit model number	22c
Age of mineralization	Undated; may be genetically related to the granite-porphyry host rock which has been dated at 71.2 Ma (Bundtzen and others, 1998).
Alteration of deposit	White mica (potassic).

Production and reserves

Workings or exploration	Surface sampling was conducted by the Alaska Division of Geological and Geophysical Surveys in 1987 and 1991 (Bundtzen and others, 1998). During the 1990s, Placer Dome Exploration sampled this occurrence but the results of their study is unknown. The area has been trenched but the trenches were overgrown with vegetation in 1991.
Indication of production	None

References

References Bundtzen, T.K., Harris, E.E., Miller, M.L., Layer, P.W., and Laird, G.M., 1998, Geology of the Sleetmute C-7, C-8, D-7, and D-8 quadrangles, Horn Mountains, southwestern Alaska: Alaska Division of Geological and Geophysical Surveys Report of Investigations 98-12, 38 p., one sheet, scale 1:63,360. Cady, W.M., Wallace, R.E., Hoare, J.M., and Webber, E.J., 1955, The central Kuskokwim region, Alaska: U.S. Geological Survey Professional Paper 268, 132 p.
Reporters	T.K. Bundtzen (Pacific Rim Geological Consulting, Inc.) and M.L. Miller (U.S. Geological Survey)
Last report date	5/8/2003