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Ebba

Prospect, Inactive

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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 C-1
Latitude 57.6638
Longitude -134.2263
Nearby scientific data Find additional scientific data near this location
Location and accuracy The Ebba prospect is at an elevation of about 300 feet at the southeast end of Hasselborg Lake. The prospect is 0.5 mile southwest of the center of sec. 34, T. 48 S., R. 69 E. It is location 68 of Cobb (1972, 1978) and MAS no. 0021140030 (U.S. Bureau of Land Management, 2002). The location is accurate within 0.2 mile.

Geologic setting

Geologic description

The rocks in the vicinity of the Ebba prospect are part of a unit of Mesozoic and Paleozoic, undifferentiated metamorphic rocks (Lathram and others, 1965). Race and Rose (1967) describe the prospect here as highly chloritized gabbro that is partially replaced by pyrrhotite, chalcopyrite, and possibly other sulfides. The deposit was discovered in 1959 and a claim was staked on it. A sample of the gabbro contained 0.03 percent copper, 0.15 percent nickel, 0.02 ounce of gold per ton, and 1.13 ounce of silver per ton. Unmineralized gabbro occurs nearby and the gabbro is bordered by schist, chert, and black phyllite a few hundred feet away.
Geologic map unit (-134.228044383784, 57.6634627813845)
Mineral deposit model Gabbro with chalcopyrite and pyrrhotite.
Alteration of deposit The mineralized gabbro is highly chloritized.

Production and reserves

Workings or exploration The deposit was discovered and claimed in 1959; there is no indication of any substantial exploration work on it.
Indication of production None

Additional comments

The prospect is now within the Wilderness of the Admiralty Island National Monument and is closed to mineral exploration and development.

References

MRDS Number A013314

References

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.
Lathram, E.H., Pomeroy, J.S., Berg, H.C., and Loney, R.A., 1965, Reconnaissance geology of Admiralty Island, Alaska: U.S. Geological Survey Bulletin 1181-R, p. R1-R48.
Race, W.H., and Rose, A.W., 1967, Geochemical and geological investigations of Admiralty Island, southeastern Alaska: Alaska Division of Geological and Geophysical Surveys, Geochemical Report 8, 45 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 Donald Grybeck (U.S. Geological Survey)
Last report date 5/5/2005