Unnamed (head of South Fork Kuskokwim River) (ARDF #LH022) Ag, Cu, Mo, Sn

Unnamed (head of South Fork Kuskokwim River)

Occurrence, Inactive

Commodities and mineralogy

Main commodities	Ag; Cu; Mo; Sn
Ore minerals	chalcopyrite; pyrite
Gangue minerals	quartz; tourmaline

Geographic location

Quadrangle map, 1:250,000-scale	LH
Quadrangle map, 1:63,360-scale	C-2
Latitude	61.5182
Longitude	-153.4803
Nearby scientific data	Find additional scientific data near this location
Location and accuracy	This occurrence is at an elevation of about 4,800 feet on the south side of a glacier that occupies the central headwater tributary of the South Fork Kuskokwim River. The map site is in the SE1/4 section 32, T 17 N, R 23 W, of the Seward Meridian. This is locality 8 of Cobb (1972 [MF 412]; 1976 [OF 76-485]) and locality 24 of Gamble and others (1989). The location is probably accurate to within a quarter of a mile.

Geologic setting

Geologic description Reed and Elliott (1970) reported finding two sulfide-bearing boulders at this locality. The boulders are of Tertiary quartz diorite and diorite gneiss (Cobb and Reed, 1981). The quartz diorite boulder contained quartz-tourmaline veins carrying 15 percent chalcopyrite and 5 percent pyrite. The diorite gneiss boulder contained tourmaline and 15 percent disseminated chalcopyrite. Rock samples contained as much as 50 ppm silver, 700 ppm molybdenum, 700 ppm tin, and 0.7 ppm gold.
Geologic map unit	(-153.482542454751, 61.5175582416358)
Mineral deposit model	Polymetallic veins and porphyry Cu? (Cox and Singer, 1986, models 22c and 21a?)
Mineral deposit model number	22c and 21a?
Age of mineralization	Tertiary. Quartz veins and mineralization crosscut Tertiary intrusive rocks.
Alteration of deposit	Quartz-tourmaline veining and replacement(?).

Production and reserves

Workings or exploration	Reconnaissance sampling has been completed in this area (Reed and Elliott, 1970).
Indication of production	None

References

MRDS Number	A013065
References Cobb, E.H., 1972, Metallic mineral resources map of the Lime Hills quadrangle, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-412, 1 sheet, scale 1:250,000. Cobb, E.H., 1976, Summary of references to mineral occurrences (other than mineral fuels and construction materials) in the Iliamna, Lake Clark, Lime Hills, and McGrath quadrangles, Alaska: U.S. Geological Survey Open-File Report 76-485, 101 p. Cobb, E.H., and Reed, B.L., 1981, Summaries of data on and lists of references to metallic and selected nonmetallic mineral occurrences in the Iliamna, Lake Clark, Lime Hills, and McGrath quadrangles, Alaska; Supplement to Open-File Report 76-485; Part A, Summaries to January 1, 1981: U.S. Geological Survey Open-File Report 81-1343-A, 25 p. Gamble, B.M., Bailey, E.A., and Reed, B.L., 1989, Gold occurrences near Snowcap Mountain, Lime Hills B-2 quadrangle, Alaska: U.S. Geological Survey Open-File Report 89-0646, 8 p. Reed, B.L., and Elliott, R.L., 1970, Reconnaissance geologic map, analyses of bedrock and stream sediment samples, and an aeromagnetic map of parts of the southern Alaska Range: U.S. Geological Survey Open-file Report 70-271, 24 p., 4 sheets, scale 1:250,000.
Reporters	Travis L. Hudson and Madelyn A. Millholland
Last report date	6/10/2001