|Quadrangle map, 1:250,000-scale||PA|
|Quadrangle map, 1:63,360-scale||B-3|
|Nearby scientific data||Find additional scientific data near this location|
|Location and accuracy||This occurrences is a pegmatite about 600 feet in diameter that is about 1.0 mile west of the head of Redfish Bay near the middle of the south boundary of section 36, T. 63 S., R. 67 E., of the Copper River Meridian. The location is accurate.|
Geologic descriptionAs described by Sainsbury (1957), this occurrence consists of a circular body of pegmatite about 600 feet in diameter. The pegmatite is in a large composite intrusive body near the contact of monzonite or granite and quartz diorite. Loney and others (1975) map the body as tonalite and granodiorite of Tertiary age. Detailed mapping by Sainsbury indicates that the pegmatite consists of two or more dike-like phases. The pegmatite is zoned with a core of quartz surrounded by a shell of variable mineralogy that includes areas of perthite, quartz, and graphic granite; microcline-perthite; and perthite, mica, and quartz. A border zone is generally quartz and graphic granite. The chief commodity of interest is microcline-perthite that occurs in zones 4 to 10 feet thick; the largest zone is at least 120 feet long and 6 to 8 feet thick. There is some optical-grade quartz. Sainsbury tentatively identified a few grains of cassiterite, but there is no indication of beryllium, columbium, or tantalum minerals. The pegmatite is not radioactive.
|Geologic map unit||(-134.883098131644, 56.3573145233823)|
|Mineral deposit model||Pegmatite.|
|Age of mineralization||The pegmatite is in a large Tertiary granitic intrusion and is probably the same age.|
|Workings or exploration||Probably none beyond surface examination and sampling by the U.S. Geological Survey and U.S. Bureau of Mines.|
|Indication of production||None|
Additional commentsMAS number: 0021160021.
Berrryhill, R.V., 1963, Examination of a pegmatite deposits near Redfish Bay, Baranof Island, southeastern Alaska: U.S. Bureau of Mines Examination Report 136, 5 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.
Loney, R.A., Brew, D.A., Muffler, L.J. B., and Pomeroy, J.S., 1975, Reconnaissance geology of Chichagof, Baranof, and Kruzof Islands, southeastern Alaska: U.S. Geological Survey Professional Paper 792, 105 p.
Sainsbury, C.L., 1957, Some pegmatite deposits in southeastern Alaska: U.S. Geological Survey Bulletin 1024-G, p. 141-161.
Skow, M.L., 1962, Mica, a materials survey: U.S. Bureau of Mines Information Circular 8125, 240 p.
|Reporters||Donald J. Grybeck (U.S. Geological Survey)|
|Last report date||2-Jan-05|