Unnamed Occurrence (ARDF - SK056; near Tsirku Glacier), Skagway District, Juneau District, Haines Borough, Alaska, USA
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Geology: According to Still and others (1984): 'Float and bedrock samples contain up to 6.2% zinc, 2.33% copper, 1.18% lead, 450 ppm cobalt, 49.84 ppm silver, 0.30 ppm gold, 1.13% barium, 200 ppm tin, 400 ppm arsenic, 300 ppm nickel, and 900 ppm bismuth. The samples include: 'pyrrhotite bearing quartz vein in slate', 'quartz boulder with 0.1 foot pyrrhotite band', 'massive pyrrhotite boulder with sparse quartz', 'altered volcanic boulder with massive sphalerite, chalcopyrite and galena(?)', and '70% silica, 30% sulfides - pyrrhotite, chalcopyrite and sphalerite.' Bedrock in the area is Paleozoic slate, metavolcanics. and limestone near a Cretaceous diorite, quartz diorite and granodiorite pluton (MacKevett and others, 1974). The nature of this occurrence is unclear. It is probably either a polymetallic quartz-sulfide vein(s) or a volcanogenic, massive sulfide. If it is a vein(s), then it is probably Cretaceous based on the age of nearby intrusives (MacKevett and others, 1974). If it is a volcanogenic massive sulfide occurrence, then it is probably Late Triassic like the Windy Craggy and Greens Creek massive sulfide deposits (Still, 1984 [OF 118-84]; Newberry and others, 1997).
Age: If it is a quartz-sulfide vein, it is probably Cretaceous, based on the age of nearby intrusives (MacKevett and others, 1974). If it is a volcanogenic massive sulfide, it is probably Late Triassic like the Windy Craggy and Greens Creek massive-sulfide deposits nearby (Still, 1984 (OFR 118-84); Newberry and others, 1997)
Alteration: Altered volcanics are mentioned but not described (Still and others, 1984).
Commodities (Major) - Ag, Au, Cu, Pb, Zn; (Minor) - Ba, Co
Development Status: No
Deposit Model: Unknown, but probably either a polymetallic quartz-sulfide vein or a Besshi- or
Mineral List
7 entries listed. 7 valid minerals.
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References
Berg, H.C., 1984, Regional geologic summary, metallogenesis, and mineral resources of southeastern Alaska: U.S. Geological Survey Open-file Report 84-572, 298 p., 1 plate, scale 1:600,000. MacKevett, E.M., Jr., Robertson, E.C., and Winkler, G.R., 1974, Geology of the Skagway B-3 and B-4 quadrangles, southern Alaska: U.S. Geological Survey Professional Paper 832, 33 p., 1 plate. Newberry, R.J., Crafford, T.C., Newkirk, S.R., Young, L.E., Nelson, S.W., and Duke, N.A., 1997, Volcanogenic massive sulfide deposits of Alaska, in Goldfarb, R.J. and Miller, L. D., eds., Mineral deposits of Alaska: Economic Geology Monograph 9, p. 120-150. Still, J.C., 1984, Stratiform massive sulfide deposits in the Mt. Henry Clay area, southeast Alaska: U.S. Bureau of Mines Open-File Report 118-84, 65 p. Still, J.C., Weir, K.R., Gilbert, W.G., and Redman, E.C., 1984, Stream-sediment, float, and bedrock sampling in the Porcupine mining area, southeast Alaska: U.S. Bureau of Mines Open-File Report 173-84, 16 p., 1 sheet.
