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Unnamed (near the glacier at the head of the West Fork Chistochina River)

Occurrence, Inactive

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Commodities and mineralogy

Main commodities Cu
Other commodities Fe; Mn
Ore minerals chalcopyrite; magnetite; rhodochrosite; rhodonite; pyrite
Gangue minerals carbonate mineral; chlorite; epidote; quartz

Geographic location

Quadrangle map, 1:250,000-scale MH
Quadrangle map, 1:63,360-scale A-2
Latitude 63.1845
Longitude -144.973
Nearby scientific data Find additional scientific data near this location
Location and accuracy This occurrence is southeast of the terminus of the glacier at the the head of West Fork Chistochina River and at an elevation of about 4,100 feet. It is in the W1/2NE1/4 section 13, T. 20 S., R. 14 E., Fairbanks Meridian. The occurrence corresponds to locality 9 on figure 1 of Rose (1967) and locality 2 on figure 6 of Cobb (1979 [OFR 79-238]). The location is probably accurate within 1,000 feet.

Geologic setting

Geologic description

The rocks near this site are andesite of the Slana Spur Formation of Pennsylvanian to Permian age (Richter and Dutro, 1975). The andesite is intruded by Mesozoic (?) quartz monzonite and is partly replaced by pods as much as 5 feet wide that have abundant chalcopyrite, pyrite, and magnetite in a gangue of quartz, epidote, chlorite, and an unspecified carbonate mineral (Rose, 1967). Rose found a boulder near the site that contained rhodonite, rhodochrosite, and quartz but could not determine if it was locally derived or transported.
Geologic map unit (-144.975223216969, 63.1840992691218)
Mineral deposit model Cu skarn (Cox and Singer, 1986; model 18b).
Mineral deposit model number 18b
Age of mineralization Possibly Mesozoic, on the basis of the association with a quartz monzonite pluton of that age.
Alteration of deposit Replacement of andesite by masses of skarn-like pyrite-chalcopyrite-magnetite accompanied by chlorite, epidote, quartz, and a carbonate mineral.

Production and reserves

Workings or exploration The natural exposure of mineralized andesite is in an abandoned stream channel; the occurrence was not found during the investigations of I.M. Lange and W.J. Nokleberg in 1979 and 1980.
Indication of production None

References

MRDS Number A011772

References

Cobb, E.H., 1979, Summary of references to mineral occurrences (other than mineral fuels and construction materials) in the Mount Hayes quadrangle, Alaska: U.S. Geological Survey Open-File Report 79-238, 140 p.
Richter, D.H., and Dutro, J.T., Jr., 1975, Revision of the type Mankomen Formation (Pennsylvanian and Permian), Eagle Creek area, eastern Alaska Range, Alaska: U.S. Geological Survey Bulletin 1395-B, p. B1-B25.
Rose, A.W., 1967, Geology of the upper Chistochina River area, Mount Hayes quadrangle, Alaska: Alaska Division of Mines and Minerals Geologic Report 28, 41 p., 2 maps, scale 1:40,000.
Reporters W.T. Ellis (Alaska Earth Sciences), C.C. Hawley (Hawley Resource Group), and W.J. Nokleberg (USGS)
Last report date 6/27/2003