Unnamed Occurrence (ARDF - TL053; near McDoel Peak), Yentna District, Matanuska-Susitna Borough, Alaska, USA
Location: Reed and others (1978, locality 38) show this occurrence in a tributary to Johnson Creek at about 2700 feet. The locality is approximately 3.5 miles east of McDoel Peak in the southeast quarter of Section 3, T. 22 N., R. 16 W., of the Seward Meridian.
Geology: Curtin, Karlson, O'Leary, Day, and McDanal (1978) report gold (+30 ppm) in bulk heavy-mineral concentrate samples from stream gravels at this locality. The area is underlain by hydrothermally altered Mesozoic graywacke and argillite (KJs) and one of the small bodies of diorite/granodiorite assigned to the Late Cretaceous (67.4 m.y.) Kichatna plutons (TKk) (Reed and others, 1978; Reed and Nelson, 1980). The creek contains abundant float of vein quartz. Gold was not detected from the quartz material, but Reed and others (1978) report a pan concentrate yielded more than 30 colors of fine gold. They indicate that similar altered zones are observed along Dollar (TL031) and Thunder Creeks (TL032, TL058), at the headwaters of Treasure (TL030), Dutch (TL033) and Bear Creeks (TL017).
Workings: Reconnaissance mapping (Reed and Nelson, 1980), stream silt and rock sampling (Curtin, Karlson, O'Leary, Day, and McDanal,1978) has been done by the U.S. Geological Survey. Prospecting and sampling was done by prospectors and claim owners in the 1980s. Current claim status is not known.
Age: Pleistocene; gold in sediment samples may have been derived from zones within the KJs that are hydrothermally altered by one of the Late Cretaceous diorite/granodiorite (67.4 m.y.) Kichatna plutons (TKk) mapped by Reed and Nelson (1980).
Alteration: The area is underlain by hydrothermally altered Mesozoic graywacke and argillite (Reed and others, 1978). Alteration mineralogy is not specified. However, based on its reported similarity to altered zones at Thunder Creek (TL032, TL058), it is most likely argillic alteration of Mesozoic sedimentary rocks.
Commodities (Major) - Au
Development Status: No
Deposit Model: Placer Au-PGE (Cox and Singer, 1986; model 39a).
ReferencesCobb, E.H., and Reed, B.L., 1980, Summaries of data on and lists of reference to metallic and selected nonmetallic mineral deposits in the Talkeetna quadrangle, Alaska: U.S. Geological Survey Open-File Report 80-884, 106 p. Curtin, G.C., Karlson, R.C., O'Leary, R.M., Day, G.W., and McDanal, S.K., 1978, Geochemical and generalized geologic maps showing the distribution and abundance of gold and silver in the Talkeetna quadrangle, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-870-E, 2 sheets, scale 1:250,000. MacKevett, E.M., Jr., and Holloway, C.D., 1977, Map showing metalliferous and selected non-metalliferous mineral deposits in the eastern part of southern Alaska: U.S. Geological Survey Open-File Report 77-169-A, 99 p., 1 sheet, scale 1:1,000,000. Reed, B.L., and Nelson, S.W., 1980, Geologic map of the Talkeetna quadrangle: U.S. Geological Survey Miscellaneous Investigations Map I-1174, 1 sheet, scale 1:250,000. Reed, B.L., Nelson, S.W., Curtin, G.C., and Singer, D.A., 1978, Mineral resources map of the Talkeetna quadrangle, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-870-D, 1 sheet, scale 1:250,000.
1 entry listed. 1 valid mineral.
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Locality Updated: Vila Nova de Poiares, Coimbra District, PortugalFrom Rui Nunes, 29th Aug 2014 16:17:00