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Unnamed (southeast of mouth of Stag Bay)

Prospect, Probably inactive

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Commodities and mineralogy

Main commodities Cu; Fe
Other commodities Ag
Ore minerals chalcopyrite; magnetite; pyrite
Gangue minerals epidote; quartz

Geographic location

Quadrangle map, 1:250,000-scale SI
Quadrangle map, 1:63,360-scale D-8
Latitude 57.9119
Longitude -136.3477
Nearby scientific data Find additional scientific data near this location
Location and accuracy This prospect is on the northeast flank of Mount Hill about a mile south-southeast of the mouth of Stag Bay. The prospect is at an elevation of about 1,500 feet, 0.2 mile north-northeast of the center of sec. 4, T. 46 S., R. 56 E. It is location P-38 of Bittenbender and others (1999), MAS no. 0021140087 (U.S. Bureau of Land Management, 2002), and is included in location 7 of Cobb (1972, 1978). The location is accurate.

Geologic setting

Geologic description

Johnson and Karl (1985) map the rocks in the area of this prospect as Freeburn assemblage, a collage of kilometer-scale, fault-bounded, lozenge-shaped blocks of Cretaceous and Cretaceous(?) metasedimentary and metavolcanic rocks. The prospect is about 0.2 mile west of the Border Ranges Fault, a northwest-striking, steeply-dipping or vertical regional fault that separates Cretaceous or younger rocks on the southwest from Mesozoic or Paleozoic rocks on the northeast.
Twenhofel and others (1949) describe this deposit as sheared and altered, fine-grained gabbro or diorite containing magnetite, pyrite, and chalcopyrite. Two trenches expose 55 and 35 feet of mineralized rock that consists of about 60 percent magnetite, about 20 percent each of epidote and quartz, locally abundant pyrite, and up to 2 percent chalcopyrite. Bittenbender and others (1999), citing work by Asbury (1964) and Kimball (1982), describe the prospect as a porphyry deposit containing copper, iron, and tungsten, although tungsten is not reported in the sample analyses that they cite. Their samples contained up to 1.07 percent copper, 20-90 percent magnetite, and a trace of silver.
Geologic map unit (-136.349538405484, 57.9115186151522)
Mineral deposit model Porphyry copper? (Cox and Singer, 1986; model 17).
Mineral deposit model number 17?
Age of mineralization Probably Cretaceous or younger.
Alteration of deposit Unspecified [hydrothermal?] alteration of host rock.

Production and reserves

Workings or exploration Two trenches.
Indication of production None

Additional comments

The site is in West Chichagof-Yakobi Wilderness.

References

MRDS Number AO13243

References

Asbury, D.W., 1964, Report on Vevelstad copper-iron property (Stag Bay): Alaska Division of Mines and Minerals Miscellaneous Report 114-10, 3 p.
Bittenbender, P., Still, J.C., Maas, K., and McDonald, M., Jr., 1999, Mineral resources of the Chichagof and Baranof Islands area, southeast Alaska: Bureau of Land Management, BLM-Alaska Technical Report 19, 222 p.
Cobb, E.H., 1972, Metallic mineral resources map of the Sitka quadrangle, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-467, scale 1:250,000.
Cobb, E.H., 1978, Summary of references to mineral occurrences (other than mineral fuels and construction materials) in the Sitka quadrangle: U.S. Geological Survey Open-File Report 78-450, 124 p.
Kimball, A.L., 1982, Mineral land assessment of Yakobi Island and adjacent parts of Chichagof Island, southeastern Alaska: U. S. Bureau of Mines Mineral Land Assessment report, MLA 97-82, 199 p.
Twenhofel, W.S., Reed, J. C., and Gates, G.O., 1949, Some mineral investigations in southeastern Alaska: U.S. Geological Survey Bulletin 963-A, p. 1-45.
U.S. Bureau of Land Management, 2002, Alaska mineral locations database report (Sitka quadrangle), July 2, 2002, 205 p. [http://imcg.wr.usgs.gov/dem.html]
Reporters H.C. Berg (U.S. Geological Survey)
Last report date 10/16/2004