Idaho; Upgrade; Wildcat; Trail Mines, Iditarod District, Yukon-Koyukuk Borough, Alaska, USA
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Geology: The Idaho, Upgrade, Wildcat, and Trail Mines produced gold from alluvial, residual, and semi-residual placer deposits on the steep northwest slopes of Chicken Mountain at the head of Flat Creek (ID104). The placers were mined from the early 20th Century to World War II but they were most productive before about 1930. During mining, it was difficult to distinguish the original overburden (Mertie, 1936, p. 204-205) and most of the gold was in weathered granitic bedrock gruss. Locally the granite was covered by about 6 feet of organic-rich muck lying directly on auriferous bedrock. According to assays reported by Mertie (1936), gold at the Upgrade claim was 844 fine and gold downslope on the Wildcat claims was 884 fine; Mertie attributed the difference to the bedrock sources rather than selective removal of silver during formation of the placers. The Idaho claims were in operation when visited by Mertie (1933). The mine then was on two paystreaks, one of which was inferred to be the upper extension of Flat Creek (ID104). Overburden ranged from 8 to 20 feet thick and was mostly angular to sand-like granitic material, with little true alluvium. The value of the ground was stated top be about 30 cents per bedrock foot. The gold that was recovered had an average fineness of 856 and was extremely fine-grained; it was accompanied by cinnabar, which was not abundant. These claims include the Idaho lode prospect at the very top of Flat Creek (Bundtzen and others, 1992). Samples collected from exposed quartz-sulfide veins contained up to 52.0 parts per million (ppm) gold, 1,600 ppm arsenic, 470 ppm antimony, and 110 ppm bismuth. Quartz-tourmaline clots are present in the walls of the veins. Based on examination of published and unpublished records, Bundtzen and others (1992) estimated that the Upgrade, Idaho, Wildcat, and related claims produced 76,400 ounces of placer gold from 1910 to 1930.
Workings: The Upgrade claims were extensively developed by David Strandberg and associates in about 1915 at about the time Flat Creek (ID104) was being extensively mined. The mines were in production when visited by Mertie in 1933 (Mertie, 1936). Exploration on the Idaho, Upgrade, Wildcat, and Alpha claim groups has taken place mainly by churn drilling and open cut preliminary to mining which was nearly continuous from 1910 to 1940s (Cobb, 1976 [OFR 76-576]). Snow fences were constructed prior to 1920 to trap water for sluicing since there was no regular stream sources of water (Smith, 1917). In 1967, the Bureau of Mines auger drilled the area (Kimball, 1969). Ken Dahl worked the Idaho claim during the early 1980s (T.K. Bundtzen, unpublished field data, 1984-86).
Age: The placer deposits are probably Quaternary; the lodes are undated.
Alteration: The monzonite bedrock is altered to gruss; quartz-tourmaline alteration in walls of Idaho lode.
Production: Based on examination of published and unpublished records, Bundtzen and others (1992) estimated that the Upgrade, Idaho, Wildcat, and related claims produced 76,400 ounces of residual placer gold from 1910 to 1930.
Reserves: None known; thought to be largely mined out (Bundtzen and others, 1992).
Commodities (Major) - Au; (Minor) - Ag, Hg
Development Status: Yes
Deposit Model: Placer Au deposit (Cox and Singer, 1986; model 39a).
7 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., 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. Mertie, J.B., Jr., 1936, Mineral deposits of the Ruby-Kuskokwim region, Alaska: U.S. Geological Survey Bulletin 864-C, p. 115-245. Smith, S.S., 1917, The mining industry in the Territory of Alaska during the calendar year 1915: U.S. Bureau of Mines Bulletin 142, 65 p.