Golden Ground Prospect (Neilson) Prospect, Iditarod District, Yukon-Koyukuk Borough, Alaska, USA
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Geology: The Golden Ground or Neilson prospect is a thin, north-trending, steeply dipping, quartz-sulfide vein associated with a swarm of veinlets that cut augite basalt that forms a roof pendant overlying a monzodiorite stock. The stock has been dated as 70.5 Ma (Bundtzen and others, 1992; Miller and Bundtzen, 1994; Miller, Bundtzen, and Gray, 2005). The vein varies from 0.4 to 2 inches thick and has been explored by two adits with 50 to 60 feet of drift (Holzheimer, 1926). The thin quartz veins contain megascopic grains of arsenopyrite, galena, scheelite, and pyrite. Grab samples contain up to 50.0 parts per million (ppm) gold, 2,000 ppm silver, 2.00 percent lead, 1.00 percent antimony, 5,000 ppm copper, 2,000 ppm tungsten, 1,000 ppm zinc, more than 1.00 percent arsenic, 300 ppm cadmium, 40 ppm bismuth, and more than 10.0 ppm mercury (McGimsey and others, 1988). The high silver, copper, lead, arsenic, and antimony, values suggest that unidentified sulfosalt minerals are also present. One sample contained the highest silver value known from the Iditarod quadrangle.
Workings: Lode prospecting in this area was reported by Brooks (1914). The Golden Ground vein was possibly discovered or developed by Rasmus Neilson, a Danish geologist who discovered the Golden Horn vein (ID115). The prospect was explored with 50 to 60 feet of drifts before 1926 (Holzheimer, 1926). Additional lode activity was reported in the area by Mertie (1936). Surface samples were collected by the Alaska Division of Geological and Geophysical Surveys and U.S. Geological Survey in the 1980s (McGimsey and others, 1988; Bundtzen and others, 1992). An exploration tunnel that was caved by 1933 and described by Cobb (1976 [OFR 76-576]) as the Malemute Gulch lode may be this prospect.
Age: Undated; the nearby monzodiorite pluton is 70.6 Ma (Bundtzen and others, 1992).
Production: According to John Miscovich (oral communication, 2002) a small amount of high-grade gold ore from the Golden Ground prospect may have been included with production from the Golden Horn Mine (ID115).
Commodities (Major) - Ag, Au; (Minor) - As, Bi, Cd, Cu, Hg, Pb, Sb, W, Zn
Development Status: Undetermined.
Deposit Model: Polymetallic vein (Cox and Singer, 1986; model 22c).
5 entries listed. 5 valid minerals.
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Brooks, A.H., 1914, Mineral resources of Alaska; report on progress of investigations in 1913: U.S. Geological Survey Bulletin 592, 413 p. 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., 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. Holzheimer, F.W., 1926, Lode mining activity in Otter Creek, Iditarod district, Alaska: Alaska Territorial Department of Mines Report MR 73-1, 7 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.