Unnamed Occurrence (ARDF - ID121; north of Discovery Camp), Iditarod District, Yukon-Koyukuk Borough, Alaska, USA
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Geology: This occurrence consists of iron-oxide-stained rubble of a quartz vein of unknown extent. The vein is in an aureole of hornfels that overlies an intrusion exposed to the west at the Golden Ground prospect (ID116). The mineralized rubble also contains fragments of brecciated, hornfelsed sandstone with tourmaline rosettes (Bundtzen and others, 1992; Miller and Bundtzen, 1994; Miller, Bundtzen, and Gray, 2005). The prospect was developed by one trench that is now sloughed and overgrown. Grab samples of mineralized rubble contain up to 1,000 parts per billion (ppb) gold, 1,000 ppb silver, 650 parts per million (ppm) antimony, more than 2,000 ppm arsenic, 2,000 ppm boron, 50 ppm tungsten, and more than 10.0 ppm mercury (McGimsey and others, 1988). The high boron value probably reflects the presence of tourmaline.
Workings: A trench cut prior to 1986 explored the mineralized area. The area was sampled by the U.S. Geological Survey in 1986 (McGimsey and others, 1988; Bundtzen and others, 1992).
Age: Undated; probably related to a nearby intrusion that is 70.6 Ma (Bundtzen and others, 1992).
Alteration: Tourmaline-mica greisen is developed in the hornfels.
Commodities (Major) - Au; (Minor) - Ag, As, Hg, Sb, W
Development Status: None
Deposit Model: Polymetallic vein (Cox and Singer, 1986; model 22c).
3 entries listed. 1 valid mineral.
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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. 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. 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.