Yankee Creek Mine, Innoko District, Yukon-Koyukuk Borough, Alaska, USA
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Location: Yankee Creek is a north-northeast-flowing tributary to the upper Innoko River. Only the lower 4.5 miles of Yankee Creek are in the Ophir quadrangle; the rest of it flows through the Iditarod quadrangle. Mining activity occurred in both quadrangles. The junction of Yankee Creek and the Innoko River is approximately 8 miles southeast of the town of Ophir. The coordinates are for the approximate midpoint of mining activity along Yankee Creek in the Ophir quadrangle; it is near a landing strip and cabins marked on the U.S. Geological Survey Ophir A-1 topographic map (1954, minor revisions 1966), in sec. 3, T. 29 S., R. 13 E., Kateel River Meridian. Yankee Creek corresponds to localities 24 and 25 of Cobb (1972 [MF 367]). This location is accurate.
Geology: The bedrock in the vicinity of Yankee Creek is slate, sandstone, and decomposed igneous rock (Mertie, 1936); the area also contains Cretaceous or Tertiary rhyolitic dikes and alkali-calcic monzonite plutons. These intrusive rocks are the likely source of gold in Yankee Creek (Bundtzen and others, 1987). Only the lower 4 1/2 miles of Yankee Creek are in the Ophir quadrangle; extensive mining along Yankee Creek also occurred in the Iditarod quadrangle. Gold is found in the coarse gravels; in 1911, these gravels were about 8 feet thick and buried under 1 to 3 feet of muck and silt (Maddren, 1911). Bundtzen and others (1987) report that the gold is 849.6 fine, with 129.5 parts silver, and 20.0 parts impurities. Smith (1941) reports an average gold fineness of 882. Heavy minerals identified in pan concentrates from lower Yankee Creek include magnetite, ilmenite, magnesiochromite, scheelite, and free gold (Bundtzen and others, 1987). Marten Gulch, a locally-named tributary to Yankee Creek in the Ophir quadrangle, contained magnetite, ilmenite, siderite, hornblende, hypersthene, eckermanite, and hidalgoite (a lead- arsenic sulfate) (Bundtzen and others, 1987). Yankee Creek was first prospected during the winter of 1908-1909, and mining began in 1909 (Maddren, 1910; Maddren, 1911). Mining was nearly continuous from 1910 until 1940 (Cobb, 1976 [OFR 76-576]). Williams (1950) and Saunders (1960) report mining along Yankee Creek in 1950 and 1959. A conservative estimate of production from Yankee Creek between 1909 to 1968 and 1981 to 1986 is 62,500 ounces of gold and 12,650 ounces of silver (Bundtzen and others, 1987).
Workings: Yankee Creek was first prospected during the winter of 1908-1909, and mining began during 1909 (Maddren, 1910; Maddren, 1911). Mining along Yankee Creek was nearly continuous from 1910 until 1940 (Cobb, 1976 [OFR 76-576]). A dredge was installed in 1921 and operated every year until 1940 (Cobb, 1976 [OFR 76-576]). After 1940, mining was intermittent. Williams (1950) and Saunders (1960) report that Rosander and Reed mined Yankee Creek in 1950 and 1959.
Age: Quaternary. The source(s) of the placer gold probably are the Cretaceous or Tertiary rhyolitic dikes and monzonite plutons in the area (Bundtzen and others, 1987).
Production: A conservative estimate of production from Yankee Creek between 1909 to 1968 and 1981 to 1986 is 62,500 ounces of gold and 12,650 ounces of silver (Bundtzen and others, 1987).
Commodities (Major) - Au; (Minor) - Ag
Development Status: Yes; medium
Deposit Model: Placer Au (Cox and Singer, 1986; model 39a)
1 entry listed. 1 valid mineral.
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Bundtzen, T.K., Cox, B.C., and Veach, N.C., 1987, Heavy mineral provenance studies in the Iditarod and Innoko districts, western Alaska: Alaska Division of Geological and Geophysical Surveys Public-Data File 87-16, 25 p. Chapman, R.M., Patton, W.W., and Moll, E.J., 1985, Reconnaissance geologic map of the Ophir quadrangle, Alaska: U.S. Geological Survey Open-File Report 85-203, 19 p., 1 sheet, scale 1:250,000. Cobb, E.H., 1972, Metallic mineral resources map of the Ophir quadrangle, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-367, 1 sheet, scale 1:250,000. Cobb, E.H., 1973, Placer deposits of Alaska: U.S. Geological Survey Bulletin 1374, 213 p. 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. Maddren, A.G., 1910, The Innoko gold-placer district, Alaska, with accounts of the central Kuskokwim valley and the Ruby Creek and Gold Hill placers: U.S. Geological Survey Bulletin 410, 87 p. Maddren, A.G., 1911, Gold placer mining developments in the Innoko-Iditarod region: U.S. Geological Survey Bulletin 480-I, p. 236-270. Mertie, J.B., Jr., 1936, Mineral deposits of the Ruby-Kuskokwim region, Alaska: U.S. Geological Survey Bulletin 864-C, p. 115-245. Saunders, R.H., 1960, Itinerary report on a trip to the Flat and Ophir Districts: Alaska Territorial Department of Mines Itinerary Report 64-2, 15 p. Williams, J.A., 1950, Mining operations in the Fairbanks district and Innoko and Koyukuk precincts: Alaska Territorial Department of Mines Miscellaneous Report 194-13, 20 p.