Spruce Creek Mine, Iditarod District, Yukon-Koyukuk Borough, Alaska, USA
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Geology: The Spruce Creek placer mine is a moderately shallow, but narrow, muck-covered, placer gold deposit. The lower mile of the creek has been mined. The paystreak is about 30 to 60 feet wide and is overlain by about 12 to 20 feet of organic muck (L.E. Wyrick, oral communication, 1986; T.K. Bundtzen, unpublished field data, 1986; Miller and Bundtzen, 1994; Miller, Bundtzen, and Gray, 2005) In addition to gold and abundant cinnabar, ilmenite, garnet, and magnetite have been identified in concentrates. The gold averages 897 fine (Bundtzen, Cox, and Veach, 1987). A plausible lode source for the placer gold is a granodioritic pluton at the head of the creek. A local source for the cinnabar is suggested by the angular fragments of this relatively friable mineral that are found in abundance in the placer concentrates. Placer gold was found in Spruce Creek in 1911 (Brooks, 1912) but most of the exploration began in 1979 when L.E. Wyrick trenched and drilled the placer. Stripping began in 1980 and mining took place from late 1980 to 1983. The mechanized mining was unprofitable due to the narrowness of the creek, the thick overburden, and the marginal amount of gold in the paystreak (L.E. Wyrick, oral communication, 1986). About 274 ounces of gold was produced.
Workings: Placer gold was found in Spruce Creek in 1911 (Brooks, 1912) but most of the exploration began in 1979 when L.E. Wyrick trenched and drilled the placer. Stripping began in 1980 and mining took place from late 1980 to 1983. The mechanized mining was unprofitable due to the narrowness of the creek, the thick overburden, and the marginal amount of gold in the paystreak (L.E. Wyrick, oral communication, 1986).
Age: Undated, but probably Quaternary.
Production: Gold was discovered in 1911 (Brooks, 1912). About 274 ounces) of gold was produced prior to 1984 but mainly from 1981 to 1983 (L.E. Wyrick, oral commun., 1986).
Reserves: There could be still be gold in the gravel under thick overburden in the upper end of the creek (L.E. Wyrick, oral communication, 1986).
Commodities (Major) - Au; (Minor) - Hg
Development Status: Yes
Deposit Model: Placer Au deposit (Cox and Singer, 1986; model 39a).
4 entries listed. 4 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.