|Quadrangle map, 1:250,000-scale||PA|
|Quadrangle map, 1:63,360-scale||D-1|
|Nearby scientific data||Find additional scientific data near this location|
|Location and accuracy||This prospect includes several claims and a test pit on mineralization at the east end of a small island south of the Keku Islands and just north of the peninsula north of Saginaw Bay. The prospect is about 6.8 miles east-southeast of Cornwallis Point; it is in the north half of section 28, T. 57 S., R. 72 E.|
This prospect is one of a group of similar deposits (PA021 to PA031) that are scattered along the south shore of Saginaw Bay, on the peninsula north of Saginaw Bay, and on the Keku Islands. They occur in a heterogeneous section of unmetamorphosed volcanic, carbonate, and clastic rocks that vary in age from Silurian to Triassic (Muffler, 1967). The mineralization generally consists of veins, veinlets, and irregular pods that contain base metals and barite (Still and others, 2002). There are no plutonic rocks in the immediate vicinity; however, the sedimentary rocks are cut by scattered gabbro dikes. The origin of the deposits is uncertain although most appear to be epigenetic. Various origins have been proposed including that they are remobilized massive-sulfide deposits, that they are related to a buried intrusive, or that they are Mississippi-Valley-type deposits.This prospect was known before 1925 and was staked intermittently until at least 1953. The only working is a small test pit. The rocks in the area consist of limestone, part of the the Kuiu Limestone of Silurian age, that is cut by gabbro dikes (Muffler, 1967). The limestone is cut by short veins, stringers, and pods of barite, witherite, and pyrite. Still and others (2002) sampled several occurrences on the small island on which the deposits occur. At the northwest end of the island, a barite stringer about 1.5 feet wide contained 3.2 percent zinc, 2,355 parts per million (ppm) lead and 24.22 percent barite. At the northeast end of the island, a mineralized zone 50 feet wide extends for about 50 feet before it disappears under the water. The zone contains stringers of barite and pyrite with rare galena, and pods of pyrite up to 0.6 feet wide and 1.0 feet long. A pod of barite with pyrite contained 1,602 ppm arsenic, and 7,107 ppm barium. A pyrite lens contained 1,725 ppm arsenic and 8,498 ppm barium.
|Geologic map unit||(-134.081982254643, 56.9011446021432)|
|Mineral deposit model||Stringers and pods of barite, witherite, and pyrite in limestone.|
|Age of mineralization||Younger than the Silurian to Triassic host rocks.|
|Workings or exploration||This prospect was known before 1925 and was staked intermittently until at least 1953. The only working is a small test pit.|
|Indication of production||None|
Additional commentsMAS number: 0021160013.
Buddington, A.F., 1925, Mineral investigations in southeastern Alaska: U.S. Geological Survey Bulletin 773-B, p. 71-139.
Cobb, E.H., 1972, Metallic mineral resources map of the Port Alexander quadrangle, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-464, 1 sheet, scale 1:250,000.
Cobb, E.H., 1978, Summary of references to mineral occurrences (other than mineral fuels and construction materials) in the Port Alexander quadrangle: U.S. Geological Survey Open-File Report 78-787, 33 p.
Jermain, G.D., and Rutledge, F.A., 1949, Summary report of war minerals examination, Spallright Nos. 1, 2, and 3: Unpublished U.S. Bureau of Mines report, 2 p. (On file at the Juneau Mineral Information Center, U.S. Bureau of Land Management, Juneau, Alaska.)
Muffler, L.J.P., 1967, Stratigraphy of the Keku Islets and neighboring parts of Kuiu and Kupreanof Islands, southeastern Alaska: U.S. Geological Survey Bulletin 1241-C, p. C1-C52.
Still, J.C., Bittenbender, P.E., Bean, K.W., and Gensler, E.G., 2002 Mineral assessment of the Stikine area, central Southeast Alaska: U.S. Bureau of Land Management Technical Report 51, 560 p.
|Reporters||Donald J. Grybeck (U.S. Geological Survey)|
|Last report date||2-Jan-05|