Baumeister Bench

Mine, Inactive

Commodities and mineralogy

Main commodities Au
Other commodities Ag
Ore minerals gold; magnetite
Gangue minerals quartz

Geographic location

Quadrangle map, 1:250,000-scale ID
Quadrangle map, 1:63,360-scale D-2
Latitude 62.97241
Longitude -156.51016
Nearby scientific data Find additional scientific data near this location
Location and accuracy The Baumeister Bench is on a dissected alluvial terrace about 100 feet higher than the modern flood plain of Ganes Creek. It is about 500 feet southeast of the Ganes Creek mining camp near the common corners of sections 4, 5, 8, and 9, T. 33 N., R. 38 W., of the Seward Meridian. The location is accurate.

Geologic setting

Geologic description

The Baumeister Bench mine is on a relict strath terrace formed by ancestral Ganes Creek before headward erosion and stream piracy of upper Ganes Creek. In late Tertiary or early Pleistocene, upper Ganes Creek flowed into the Beaver Creek drainage (Eakin, 1914; Mertie, 1916; Bundtzen, 1980 (GR 63); Bundtzen and Miller, 1997). The bench is the part of ancestral Ganes Creek that is locally preserved on both flanks of modern Ganes Creek over a distance of more than 10 miles kilometers.
The rocks at the base of the Baumeister Bench are altered, probably by surficial weathering processes; up to 10 feet of the Upper Cretaceous, Kuskokwim Group sedimentary rocks on bedrock are oxidized and dike rocks are altered to clay and gossan. Alluvium on the bench consists of rounded gravel and cobbles of sedimentary and igneous rocks. Placer gold, often with adhering quartz, occurs in the alluvium, as well as magnetite. Exceptionally large nuggets have been found in the bench deposit.
Geologic map unit (-156.512524147472, 62.9717775075606)
Mineral deposit model Placer Au deposit (Cox and Singer, 1986; model 39a).
Mineral deposit model number 39a
Age of mineralization Probably late Tertiary or early Pleistocene (Hopkins and others, 1971).
Alteration of deposit Bedrock below the gold-bearing alluvium is altered to at least 3 meters of depth. Dike rocks have been gossanized and converted to clay.

Production and reserves

Workings or exploration The Baumeister Bench probably was discovered with other bench deposits of the area before 1910 (Maddren, 1910). The Baumeister Bench was mined by hydraulic methods at intervals between discovery and World War II (Warren Magnuson, pers. communication, 1986). After World War II, bulldozers were used for exploration and ground preparation activities.
Indication of production Yes
Production notes Production prior to 1960 was lumped with Ganes Creek (ID011). About 3,500 ounces of gold were recovered from the Baumeister Bench during mining between 1960 and 1966 (Warren Magnuson, oral communication, 1990). About 1,500 ounces were recovered from alluvium and reworked tailings in the 1980s and 1990s (T.K. Bundtzen, unpublished records, 1999). Between 1964 and 1986, 60-ounce and a 122-ounce gold nuggets were mined on the Baumeister Bench (Warren Magnuson, oral communication, 1990); during the 1990s, gold-quartz nuggets weighing up to 55 ounces were mined on the bench (Doug Clark, oral communication, 2001).

References

References

Bundtzen, T.K., and Miller, M.L., 1997, Precious metals associated with Late Cretaceous-early Tertiary igneous rocks of southwestern Alaska, in Goldfarb, R.J., and Miller, L.D., eds., Mineral Deposits of Alaska: Economic Geology Monograph 9, p. 242-286.
Hopkins, D.M., Matthews, J.V., Wolfe, J.A., and Silberman, M.L., 1971, A Pliocene flora and insect fauna from the Bering Sea region: Paleoecology, vol. 9, p. 211-231.
Reporters T.K. Bundtzen (Pacific Rim Geological Consulting, Inc.), M.L. Miller (U.S. Geological Survey); and C.C. Hawley (Hawley Resource Group)
Last report date 5/12/2003