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  3. Alaska Resource Data File (ARDF)

Unnamed (northeast shore of Portage Arm)

Occurrence, Probably inactive

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Commodities and mineralogy

Main commodities Cu
Ore minerals bornite; chalcopyrite; covellite; pyrite; pyrrhotite
Gangue minerals quartz

Geographic location

Quadrangle map, 1:250,000-scale SI
Quadrangle map, 1:63,360-scale B-3
Latitude 57.3423
Longitude -134.9043
Nearby scientific data Find additional scientific data near this location
Location and accuracy This occurrence on Catherine Island is at sea level on the northeast shore of Portage Arm, about a mile north of Portage Point. The occurrence is 0.4 mile south-southeast of the center of sec. 21, T. 52 S., R. 65 E. It is location P-100 of Bittenbender and others (1999), location 61 of Cobb (1972, 1978), and MAS no. 0021140050 (U.S. Bureau of Land Management, 2002). The location is accurate within 0.5 mile.

Geologic setting

Geologic description

The rocks in the vicinity of this occurrence are part of the Jurassic and/or Triassic, Kelp Bay Group which consists of phyllite, quartzite, greenschist, greenstone, graywacke, and semischist (Loney and others, 1975). The rocks in this area are marked by the development of an intense cataclastic foliation. Loney and others (1963) noted pyrite, chalcopyrite, covellite, and bornite in quartz veins and iron-stained siliceous rocks in this area. Bittenbender and others (1999) collected 4 samples along several miles of shoreline of quartz and quartz veins with up to 1-2 percent chalcopyrite and 10 percent pyrite and pyrrhotite. Gold was below 5 parts per billion in all the samples and the highest copper value was 1,810 parts per million; all of the other metallic elements were at background level.
Geologic map unit (-134.906060125609, 57.3419616688349)
Mineral deposit model Quartz veins with copper minerals.
Age of mineralization Triassic or younger based on the age of the host rocks.

Production and reserves

Workings or exploration Apparently only surface sampling by government geologists.
Indication of production None

References

MRDS Number A013307

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.
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.
Loney, R.A., Berg, H.C., Pomeroy, J.S., and Brew, D.A., 1963, Reconnaissance geologic map of Chichagof Island and northwestern Baranof Island, Alaska: U.S. Geological Survey Miscellaneous Geologic Investigations Map I-388, 1 sheet, scale 1:250,000.
Loney, R.A., Brew, D.A., Muffler, L.J.P., and Pomeroy, J.S., 1975, Reconnaissance geology of Chichagof, Baranof, and Kruzof Islands, southeastern Alaska: U.S. Geological Survey Professional Paper 792, 105 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