Unnamed (west of South Arm, Bay of Isles, Knight Island) (ARDF #SR247) Cu, Zn

Unnamed (west of South Arm, Bay of Isles, Knight Island)

Prospect, Inactive

Commodities and mineralogy

Main commodities	Cu; Zn
Ore minerals	chalcopyrite; pyrite; pyrrhotite; sphalerite
Gangue minerals	epidote; quartz

Geographic location

Quadrangle map, 1:250,000-scale	SR
Quadrangle map, 1:63,360-scale	B-2
Latitude	60.3621
Longitude	-147.735
Nearby scientific data	Find additional scientific data near this location
Location and accuracy	The prospect is located in the saddle on the southeast flank of hill 1870 west of the head of South Arm, Bay of Isles, at an elevation of about 1,350 feet. It is in the SW1/4 section 9, T. 3 N., R. 10 E., of the Seward Meridian. This is location S-63 of Jansons and others (1984). This location is accurate to within a quarter of a mile.

Geologic setting

Geologic description The occurrence consists of an iron-stained shear zone in schistose greenstone that contains pyrite, pyrrhotite, chalcopyrite, and sphalerite (Kurtak and Jeske, 1986). The shear zone is nearly vertical, strikes N25E, and can be traced for about 6 miles. The zone cuts greenstone of the Orca Group of early Tertiary age (Nelson and others, 1985). Within the zone, a 2.5- by 25-foot outcrop of iron-stained greenstone contains pyrite, pyrrhotite, about 1 percent chalcopyrite, and 20 percent sphalerite. Quartz and epidote veinlets also occur within the zone (Kurtak and Jeske, 1986). Chip and grab samples from this occurrence contained from 20 ppm to 0.8 percent copper and from 30 ppm to 5 percent zinc (Kurtak and Jeske, 1986). The U.S. Bureau of Mines reported some minor digging and scrapings in the area (Kurtak and Jeske, 1986).
Geologic map unit	(-147.737033893802, 60.3615243497935)
Mineral deposit model	Besshi massive sulfide (Cox and Singer, 1986; model 24b)
Mineral deposit model number	24b
Age of mineralization	Tertiary or younger; the mineralization is in rocks of the Orca Group of Tertiary age.

Production and reserves

Workings or exploration	The U.S. Bureau of Mines reported some minor digging and scrapings in the area (Kurtak and Jeske, 1986). Chip and grab samples from this occurrence contained from 20 ppm to 0.8 percent copper and from 30 ppm to 5 percent zinc (Kurtak and Jeske, 1986).
Indication of production	None

References

References Jansons, Uldis, Hoekzema, R.B., Kurtak, J.M., and Fechner, S.A., 1984, Mineral occurrences in the Chugach National Forest, southcentral Alaska: U.S. Bureau of Mines Mineral Land Assessment 5-84, 218 p., 2 sheets, scale 1:250,000. Kurtak, J.M., and Jeske, R.E., 1986, Mineral investigations in the Chugach National Forest, Alaska (Islands area): U.S. Bureau of Mines Open-File Report 54-86, 302 p., 1 sheet, scale 1:63,360. Nelson, S.W., Dumoulin, J. A., and Miller, M.L., 1985, Geologic map of the Chugach National Forest, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-1645-B, 16 p., 1 sheet, scale 1:250,000.
Reporters	Jeff A. Huber and Carol S. Huber (Anchorage)
Last report date	12/6/2001