Unnamed (north end of Buckstock Mountains)

Prospect, Inactive

Commodities and mineralogy

Main commodities Ag; Au; Cu
Other commodities As; Bi; Cd; Pb; W; Zn
Ore minerals arsenopyrite; bornite; chalcopyrite; scheelite; sphalerite
Gangue minerals quartz

Geographic location

Quadrangle map, 1:250,000-scale SM
Quadrangle map, 1:63,360-scale B-7
Latitude 61.38683
Longitude -158.40945
Nearby scientific data Find additional scientific data near this location
Location and accuracy This prospect is on hill 2008 at the head of the northern tributary to Gold Run in the northern Buckstock Mountains. The occurrence is near the center of the SW1/4 sec. 5, T. 15 N., R. 51 W., of the Seward Meridian. The location is accurate.

Geologic setting

Geologic description

This prospect consists of two quartz-sulfide veins that strike N75-80W across a knob of hornfels of the Upper Cretaceous Kuskokwim Group; the hornfels is cut by N70E-striking felsic dikes of the Cretaceous Buckstock Mountains intrusive complex (Cady and others, 1955). A younger dike that strikes north-south also cuts hornfels on the ridge. The Buckstock Mountains pluton has a U-Pb age of 59.2 Ma (Miller and others, 2002).
The mineralized quartz veins cut both the hornfels and the dikes. The dikes are argillized and the hornfels near the dikes are intensely altered to tourmaline, quartz, and ferricrete. The two mineralized quartz veins each average about 12 to 20 inches thick and can be traced for about 280 feet before disappearing into talus on both sides of the knob. Sulfides, which make up 1 to 2 percent of the quartz veins, include arsenopyrite, bornite, chalcopyrite, and traces of sphalerite. Yellow scheelite grains were identified in hand specimens The sulfides are usually associated with quartz that forms coxcomb textures. Six grab samples of the quartz-sulfide veins contained 187 parts per billion (ppb) gold, 72.7 parts per million (ppm) silver, 1,410 ppm copper, 149 ppm bismuth, 1,060 ppm lead, 419 ppm zinc, 495 ppm arsenic, 6.0 ppm cadmium, and 419 ppm tungsten (M.L. Miller and T.K. Bundtzen, unpublished analytical data, 1992, 1999).
Geologic map unit (-158.411804642266, 61.3861180274382)
Mineral deposit model Polymetallic vein (Cox and Singer, 1986; model 22c).
Mineral deposit model number 22c
Age of mineralization Unknown. Miller and others (2002) report a U-Pb age of 59.2 Ma for the Buckstock pluton that is present here as felsic dikes.
Alteration of deposit Strong argillic alteration in dikes; tourmaline impregnations in hornfels.

Production and reserves

Workings or exploration This prospect was sampled during a joint Alaska Division of Geological and Geophysical Surveys and U.S. Geological Survey investigation in 1992.
Indication of production None

References

References

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 5/9/2003