Bowser Creek-Main Mine, Yukon-Koyukuk Census Area, Alaska, USAi

Regional Level Types
Bowser Creek-Main Mine	Mine
Yukon-Koyukuk Census Area	Census Area
Alaska	State
USA	Country

Part of a larger intrusive-related mineral center; see Bowser Creek-Northeast (MG067) and Bowser Creek-Headwaters (MG066) prospects.
Location: The Bowser Creek-Main deposit is located along the steep, eastern margin of an active rock glacier in Bowser Creek valley; it is at an approximate elevation of 4,200 feet (1,280 m) in sec. 9, T. 24 N., R. 24 W., of the Seward Meridian. Location accurately determined; reporter visited the site in 1982 and 1988.
Geology: The Bowser Creek-Main deposit consists of replacement pods, lenses and veins of sphalerite, galena, pyrrhotite, and minor chalcopyrite, marcasite, and pyrite in skarn adjacent to felsic dikes. However, important fissure-controlled, silver-rich galena, tetrahedrite, pyrrhotite, and calcite mineralization occurs in marble away from the skarn itself. Sphalerite is iron-rich (marmatite). Galena is paragenetically late and crosscuts the earlier sphalerite-chalcopyrite veins and replacement bodies. No sulfosalts were recognized. The skarns and replacement deposits at the Bowser Creek-Main deposit are related to a dumbell-shaped, 7 square kilometer, composite pluton that intrudes a limestone rich section of the Barren Ridge Limestone, a unit of the Dillinger subterrane (Bundtzen, Harris, and Gilbert, 1997). A quartz porphyry phase of the Bowser Creek pluton has been radiometrically dated at 60.4 Ma (Bundtzen and others, 1988). Prospect sketches were provided by Reed and Elliott (1968, C 596). The richest silver concentrations occur in shear-zone controlled massive galena-sulfide veins. Reed and Elliott (1968, C 596) reported values of up to 9,635.0 grams/tonne silver, 60.00 percent lead, 14.70 percent zinc, 0.49 percent copper, and 0.4 grams/tonne gold. Bundtzen and others (1988) reported that the average of six high-grade samples of massive galena ore from shear zones in the marble front contained 2,510.0 grams/tonne silver, 23.70 percent lead, 3.44 percent zinc, 0.15 percent copper, and 110 ppb gold. Other samples collected by Bundtzen and others (1988) contained 157 ppm cobalt and 0.11 percent cadmium. Based on polished-section and assay data, silver has a highest correlation coefficient with lead (galena); cobalt is concentrated in the pyrrhotite. High cadmium values occur in sphalerite. The mineralogical source of the sporadic gold values is unknown.
Workings: The Bowser Creek-Main deposit was discovered during regional geological mapping and mineral investigations conducted in the southern Alaska Range by the U.S. Geological Survey and published in Reed and Elliott (1968, C 559 and 596) and Reed and Lanphere (1972). Portland-based, Alaskamin Mining Company and St. Eugene Mining Company, the operator for Falconbridge Mining Company, acquired the property in late 1968 (Williams, 1969) and by 1973, cut about 250 feet of surface trenches, built a 2,600-foot-long airport on the Post River, and sacked about 15 tons of high grade galena ores for air shipment to Sunshine Mining Company's Kellogg smelter in Idaho (B.L. Reed and C.N. Conwell, written communication 1982). Records from an alleged early drilling program have not been documented. Reed and Elliott (1968, C 559) reported values from surface chip samples of up to 9,635 grams/tonne silver, 60.00 percent lead, 14.70 percent zinc, 0.49 percent copper, and 0.4 grams/tonne gold. Bundtzen and others (1988) reported that the average of six high grade samples of massive galena-sulfide ores from shear zones in the marble front contained 2,510 grams/tonne silver, 23.70 percent lead, 3.44 percent zinc, 0.15 percent copper, and 110 ppb gold. Other samples collected by Bundtzen and others (1988) contained 0.11 percent cadmium and 157 ppm cobalt.
Age: Tertiary, based on 60.4 Ma age of nearby quartz porphyry intrusion; ore mineralization not dated.
Alteration: Pyrrhotite and iron-rich sphalerite (marmatite) ubiquitously weather to a deep reddish brown gossan.
Production: Approximately 15 tons of galena-rich massive sulfide ores were sacked and eventually processed at the Sunshine Mining Company smelter in Kellogg, Idaho in 1972-73 (B.L. Reed and C.N. Conwell, written communications, 1982). These ores contained about 2,332 grams/tonne silver, about 50 percent lead, and elevated zinc, cadmium, copper, and gold. Only the lead and silver were credited at the smelter (C.N. Conwell, written communication, 1982).

Commodities (Major) - Ag, Pb, Zn; (Minor) - As, Au, Cd, Co, Cu
Development Status: Yes; small
Deposit Model: Zinc-lead skarn deposits (Cox and Singer, 1986; model 18c); low temperature lea

Other Databases

Link to USGS - Alaska:	MG068

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References