Michigan Creek Bench Mine, Iditarod District, Yukon-Koyukuk Borough, Alaska, USA
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Geology: The Michigan Bench is a small placer mine near the mouth of a small north-flowing, unnamed tributary of Michigan Creek. The deposit is on a terrace that probably represents an ancestral alluvial fan at the base of the small gulch that flows northeast at the mine. The gulch drains an area underlain by a swarm of granite porphyry and granodiorite dikes and sills exposed at the heads of Julian (ID177) and Spruce Creeks (ID176) (Miller and Bundtzen, 1994; Miller, Bundtzen, and Gray, 2005). In addition to gold, the principal heavy minerals in concentrate include cinnabar, garnet, and magnetite (Bundtzen, Cox, and Veach, 1987). The garnets are probably derived from garnetiferous granite-porphyry intrusions identified during geologic mapping southwest of the mine (Miller and Bundtzen, 1994). The Michigan Bench produced 125 ounces of gold during the early 1980s (Miller, Bundtzen, and Gray, 2005).
Workings: Placer gold was located on Michigan Creek in 1911 (Brooks, 1912). Samples were collected by the U.S. Geological Survey and Alaska Division of Geological and Geophysical Surveys in the 1980s (Bundtzen, Cox, and Veach, 1987).
Production: The Michigan Bench produced 125 ounces of gold during the early 1980s (Miller, Bundtzen, and Gray, 2005).
Commodities (Major) - Au; (Minor) - Ag, Hg
Development Status: Yes; small
Deposit Model: Placer Au deposit (Cox and Singer, 1986; model 39a).
4 entries listed. 3 valid minerals.
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Brooks, A.H., 1912, The mining industry in 1911, in Brooks, A.H., and others, Mineral resources of Alaska, report on progress of investigations in 1911: U.S. Geological Survey Bulletin 520-A, p. 17-44. Bundtzen, T.K., Cox, B.C., and Veach, N.C., 1987, Heavy mineral provenance studies in the Iditarod and Innoko districts, western Alaska: Process Mineralogy VII, The Metallurgical Society, p. 221-246. Miller, M.L., and Bundtzen, T.K., 1994, Generalized geologic map of the Iditarod quadrangle, Alaska showing potassium-argon, major oxide, trace element, fossil, paleocurrent, and archeological sample localities: U.S. Geological Survey Miscellaneous Field Studies Map MF-2219-A, 48 pages; 1 sheet, scale 1:250,000. Miller, M.L., Bundtzen, T.K., and Gray, J.E., 2005, Mineral resource assessment of the Iditarod quadrangle, west-central Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-2219-B, scale 1:250,000, pamphlet.