|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 is near the shore on the north side of the Cornwallis Peninsula (the peninsula north of Saginaw Bay). It is about 2.8 miles east-southeast of Cornwallis Point and about 0.3 mile east of the center of section 15, T. 57 S., R. 71 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 first staked in 1923 and was restaked periodically until at least 1931 (Buddington, 1925; Still and others, 2002). The mineralization consists of barite veins, veinlets, and pods that cut a sequence that consists mainly of felsic and mafic volcanic rocks of the Keku Volcanics of Triassic age (Muffler, 1967). Some similar veins and veinlets contain witherite. The veins vary from 0.1 to 2.3 feet thick, extend for up to 200 feet along strike, and occur across a zone about 300 feet wide (Still and others, 2002). The veins generally strike northwest and dip steeply to vertically. The rocks in the immediate vicinity of the mineralization consist of a sequence of felsic volcanics, volcanic breccia, limestone, and conglomerate. The volcanics and conglomerate also contain disseminated pyrite and sphalerite. A sample across a vein about 2 feet thick contained 28.3 percent barite. A sample of conglomerate with disseminated sphalerite and pyrite contained 8,382 parts per million (ppm) zinc. A sample of Carboniferous limestone nearby with disseminated pyrite, sphalerite, and galena contained 5.72 percent zinc and 600 ppm lead.
|Geologic map unit||(-134.205035040161, 56.9237338344942)|
|Mineral deposit model||Barite-witherite veins; disseminated sulfides.|
|Age of mineralization||Younger than the Triassic host rocks.|
|Workings or exploration||Claims were first staked in 1923 and were restaked until at least 1931. More recently the prospect was examined and sampled by the U.S. Bureau of Land Management (Still and others, 2002).|
|Indication of production||None|
Additional commentsMAS number: 0021160008.
|MRDS Number||A013377; A013378; A013379; A013380|
Buddington, A.F., 1925, Mineral investigations in southeastern Alaska: U.S. Geological Survey Bulletin 773-B, p. 71-139.
Buddington, A.F., and Chapin, Theodore, 1929, Geology and mineral deposits of southeastern Alaska: U.S. Geological Survey Bulletin 800, 398 p.
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.
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|