Unnamed Occurrence (ARDF - MM163; on a tributary to upper Pirate Creek), Kantishna District, Denali Borough, Alaska, USA
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Location: This occurrence is on the west side of a north-flowing tributary of Pirate Creek about a mile west of Muldrow Glacier. It is probably within a few hundred feet of the north end of the section line between sections 29 and 30, T. 18 S., R. 15 W., Fairbanks Meridian. The occurrence is included in the description of the Twin Hills lode (MM168) by Cobb (1972, location 35 [MF 366]; 1980 [OFR 80-363]), and in the description of location 44 by MacKevett and Holloway (1977).
Geology: This occurrence is immediately east of the Twin Hills lode (MM168), in the contact zone of the McGonagall granitic pluton mapped by Reed (1961, plate 1). The deposit consists of replacement veins and disseminations of magnetite in a zone estimated to be 20 to 30 feet wide (Moffit, 1933, p. 324). A small amount of chalcopyrite occurs with the magnetite, and the rocks locally are ironstained and coated with copper carbonate(?). Sphalerite occurs in a fracture zone about 100 yards north of the magnetite deposit. The deposit probably is middle Tertiary, the approximate age of the emplacement of the Eocene or Oligocene McGonagall pluton (Reed and Lanphere, 1974). The occurence is one of several in a belt of mineral deposits along the north flank of the McGonagall pluton.
Workings: The deposit was discovered by W. J. Shannon in about 1930.
Age: The deposit probably is middle Tertiary, the approximate age of the emplacement of the Eocene or Oligocene McGonagall pluton (Reed and Lanphere, 1974; Cole, 1998).
Alteration: Oxidation of iron and copper minerals.
Commodities (Major) - Fe; (Minor) - Cu, Zn
Development Status: No
Deposit Model: Disseminated and vein-form, polymetallic lodes and contact deposits (Cox and Si
Mineral List
5 entries listed. 3 valid minerals.
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References
Cobb, E. H., 1972, Metallic mineral resources map of the Mount McKinley quadrangle, Alaska: U. S. Geological Survey Miscellaneous Field Studies Map MF-366, 1 sheet, scale 1:250,000. Cobb, E.H., 1980, Summary of references to mineral occurrences (other than mineral fuels and construction materials) in the Mount McKinley quadrangle, Alaska: U. S. Geological Survey Open-File Report 80-363, 150 p. Cole, R. B., 1998, Early Tertiary post-subduction volcanism and deformation along the north side of the McKinley fault, Alaska [abs]: Geological Society of America. Abstracts with program, v. 30, p. 177. Cox, D.P., and Singer, D.A., eds., 1986, Mineral deposit models: U.S. Geological Survey Bulletin 1693, 379 p. 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. Moffit, F. H., 1933, The Kantishna district: U. S. Geological Survey Bulletin 836, p. 301-338. Reed, B. L., and Lanphere, M. A., 1974, Offset plutons and history of movement along the McKinley segment of the Denali fault system, Alaska: Geological Society of America Bulletin, v. 85, p. 1883-1892. Reed, J. C., Jr., 1961, Geology of the Mt. McKinley quadrangle, Alaska: U. S. Geological Survey Bulletin 1108-A, p. A1-A36.