Unnamed (northeast of upper Buckstock River) (ARDF #SM070) As, Cu, Sb

Unnamed (northeast of upper Buckstock River)

Prospect, Inactive

Commodities and mineralogy

Main commodities	As; Cu; Sb
Other commodities	Ag; Au; Bi; Hg; W
Ore minerals	arsenopyrite; pyrite
Gangue minerals	quartz

Geographic location

Quadrangle map, 1:250,000-scale	SM
Quadrangle map, 1:63,360-scale	A-7
Latitude	61.21871
Longitude	-158.61408
Nearby scientific data	Find additional scientific data near this location
Location and accuracy	This prospect is at the head of an unnamed, north-flowing, tributary of the Buckstock River in the central Buckstock Mountains. The occurrence is at an elevation of about 1,600 feet, about 0.2 mile north-northwest of the center of sec. 16, T. 13 N., R. 52 W., of the Seward Meridian. The location is approximate.

Geologic setting

Geologic description The deposit at this prospect consists of: 1) graywacke hornfels with quartz veinlets; 2) silicified granite porphyry with iron oxides; and 3) pyrite-arsenopyrite-bearing, vuggy quartz veins in granite porphyry (Gray, Motooka, and Theodorakos, 1997). The area is underlain by the Cretaceous Buckstock pluton and associated dikes and sills that intrude the sandstone and shale of the Upper Cretaceous, Kuskokwim Group (Cady and others, 1955). The Buckstock pluton has a U-Pb age of 59.2 Ma (Miller and others, 2002). Four grab samples contained up to 1,100 parts per million (ppm) arsenic, 3.4 ppm bismuth, 590 ppm copper, 1.6 ppm mercury, 34 parts per billion (ppb) gold, and 290 ppm antimony (Gray, Motooka, and Theodorakos, 1997). The prospect is in the southwest corner of an area of anomalous stream-sediment and panned-concentrate samples (Gray, Motooka, and Theodorakos, 1997). Stream sediments contained up to 1.3 ppm gold, 150 ppm arsenic, 14 ppm bismuth, and elevated antimony and tungsten. Pan concentrates contained up to 200 ppm gold, 100 ppm silver, 500 ppm antimony, 3,000 ppm tungsten, and more than 2,000 ppm bismuth.
Geologic map unit	(-158.616419427116, 61.2179969633349)
Mineral deposit model	Polymetallic replacement deposit? (Cox and Singer, 1986; model 19a).
Mineral deposit model number	19a?
Age of mineralization	Uncertain. Miller and others (2002) report a U-Pb age of 59.2 Ma from the Buckstock pluton that makes up much of the area.
Alteration of deposit	Silicification and iron-oxide alteration of granite porphyry.

Production and reserves

Workings or exploration	Surface sampling was done by the U.S. Geological Survey in 1995 (Gray, Motooka, and Theodorakos, 1997).
Indication of production	None

References

References 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. Gray, J.E., Motooka, Jerry, and Theodorakos, P.M., 1997, Areas favorable for metallic resources and newly discovered mineral occurrences in the Buckstock Mountains area, southwestern Alaska, in Dumoulin, J.A., and Gray, J.E., eds, Geologic Studies in Alaska by the U.S. Geological Survey in 1995: U.S. Geological Survey Professional Paper 1574, p. 111- 124. Miller, M.L., Bradley, D.C., Bundtzen, T.K., and McClelland, William, 2002, Late Cretaceous through Cenozoic strike-slip tectonics of southwestern Alaska: Journal of Geology, vol.110, p. 247-270.
Reporters	T.K. Bundtzen (Pacific Rim Geological Consulting, Inc.) and M.L. Miller (U.S. Geological Survey)
Last report date	5/8/2003