Granite Creek Mine, Iditarod District, Yukon-Koyukuk Borough, Alaska, USA
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Geology: Placer gold has been mined on Granite Creek since 1910 (Mertie, 1936). The deposit developed where the creek dissects mineralized volcanic and plutonic rocks north of Otter Creek (Bundtzen and others, 1992). The gold fineness averages 854 (Mertie, 1936). Heavy minerals identified in concentrates include gold, arsenopyrite, cinnabar, scheelite, chromite, and ilmenite (Mertie, 1936; Bundtzen, Cox and Veach, 1987). The placer gold was very fine grained and shotty; about 1.5 feet of bedrock was dug up to recover the gold (Cobb, 1976 [OFR 76-576]). Granite Creek has produced at least 4,750 ounces of gold and 636 ounces of silver since the early 20th century (Bundtzen and others, 1992; Miller, Bundtzen, and Gray, 2005). These production estimates derived from incomplete mint records are probably conservative.
Workings: Mining began on Granite Creek in 1908 using scrapers working in open cuts; the most extensive mining took place between 1924 and 1940 (Cobb, 1976 [OFR 76-576]).
Age: Unknown; probably Quaternary.
Production: Granite Creek has produced at least 4,750 ounces of gold and 636 ounces of silver since the early 20th century (Bundtzen and others, 1992; Miller, Bundtzen, and Gray, 2005). These production estimates derived from incomplete mint records are probably conservative.
Commodities (Major) - Au; (Minor) - Ag, As, Cr, Hg, W
Development Status: Yes
Deposit Model: Placer Au deposit (Cox and Singer, 1986; model 39a).
6 entries listed. 6 valid minerals.
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Bundtzen, T.K., Miller, M.L., Laird, G.M., and Bull, K.F., 1992, Geology and mineral resources of Iditarod mining district, Iditarod B-4 and eastern B-5 quadrangles, southwestern Alaska: Alaska Division of Geological and Geophysical Surveys Professional Report 97, 46 p., 2 sheets, scale 1:63,360. Cobb, E.H., 1972, Metallic mineral resources map of the Iditarod quadrangle, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-363, 1 sheet, scale 1:250,000. Cobb, E.H., 1974, Placer deposits of Alaska: U.S. Geological Survey Bulletin 1374, 213 pages. Cobb, E.H., 1976, Summary of references to mineral occurrences (other than mineral fuels and construction material) in the Iditarod and Ophir quadrangles, Alaska: U.S. Geological Survey Open-File Report 76-576, 101 p. Kimball, A.L., 1969, Reconnaissance sampling of decomposed monzonite for gold near Flat, Alaska: U.S. Bureau of Mines Open File Report 6-69, 39 p. McGimsey, R.G., Miller, M.L., and Arbogast, B.F., 1988, Paper version of analytical results, and sample locality map for rock samples from the Iditarod quadrangle, Alaska: U.S. Geological Survey Open-File Report 88-421-A, 110 p., 1 sheet, scale 1:250,000. Mertie, J.B., Jr., 1936, Mineral deposits of the Ruby-Kuskokwim region, Alaska: U.S. Geological Survey Bulletin 864-C, p. 115-245. 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. Morgan, W., 1992, Synopsis of Granite Creek placer operation, Granite Creek, Iditarod quadrangle, central Alaska, unpublished company report for L.E., and Marilyn Wyrick, 22 p.