Unnamed (head of Little Bay)

Prospect, Undetermined

Commodities and mineralogy

Main commodities Ag; Au; Cu; Ni
Ore minerals chalcopyrite; pyrrhotite

Geographic location

Quadrangle map, 1:250,000-scale SI
Quadrangle map, 1:63,360-scale D-7
Latitude 57.7817
Longitude -136.2921
Nearby scientific data Find additional scientific data near this location
Location and accuracy This prospect is at sea level at the head of Little Bay. The prospect is about 0.1 mile east of the center of sec. 23, T. 47 S., R. 56 E. It is location P-46 of Bittenbender and others (1999), location 17 of Cobb (1972, 1978), and MAS no. 0021140057 (U.S. Bureau of Land Management, 2002). The location is accurate within about 0.5 mile.

Geologic setting

Geologic description

Johnson and Karl (1985) map the rocks around this prospect as a Tertiary, composite stock of gabbronorite and norite, enclosed by a discontinuous shell of tonalite. About 5 square miles of the stock are above sea level. The stock intrudes and thermally metamorphoses Cretaceous graywacke and melange. The stock postdates several high-angle, northwest-striking faults.
Cobb (1972, 1978), citing Overbeck (1919), describes this prospect as chalcopyrite and pyrrhotite in a quartzitic rock, probably near a contact with granitic rocks. Assays reportedly showed copper, silver, gold, and a trace of nickel. Only a little work had been done in 1916.
Bittenbender and others (1999), also citing Overbeck, describe the prospect as an extension of the Cu-Ni magmatic segregation deposit at Mirror Harbor (SI040), but this does not seem to agree with Overbeck's description. Bittenbender and others report a trench at the prospect.
Geologic map unit (-136.29393286418, 57.7813255349815)
Mineral deposit model Duluth Cu-Ni-PGE? (Cox and Singer, 1986; model 5a).
Mineral deposit model number 5a?
Age of mineralization If Bittenbender and others' description is correct, the deposit is Tertiary.

Production and reserves

Workings or exploration Limited surface exploration in the early 1900s.
Indication of production None

Additional comments

The prospect is in West Chichagof-Yakobi Wilderness.

References

MRDS Number A013255

References

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.
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