Unnamed Occurrence (ARDF - MF064; southwest of Red Mountain), Juneau District, Skagway-Hoonah-Angoon Borough, Alaska, USA
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Location: The deposit is near the 1000-foot elevation on an outlier to Red Mountain in section 35, T. 33 S., R. 56 E., of the Copper River Meridian. The crest of Red Mountain is about 2.5 miles to the northeast of the site which is also about 2 miles east of the anchorage at Goose Cove. It is probably located within 0.2 mile. The site is the same as number 20 of MacKevett and others (1971), number 44 of Cobb (1972), and number 72 of Kimball and others (1978).
Geology: The occurrence is in the Black Cap Limestone of Devonian age, near a granodiorite cupola of probable Cretaceous age (MacKevett and others, 1971, p. 55). Pyrite-rich pods and impregnations as much as 10 feet long and 1 foot diameter occur in the limestone. A representative sample collected by MacKevett and others (1971, table 9) contained 7000 ppm zinc, 500 ppm lead, 70 ppm cadmium, 1.5 ppm silver and an anomalous amount (30 ppm) of molybdenum. At the site, white incrustations, either hydrozincite or smithsonite, occur as secondary minerals on the pyrite-rich mass. Sphalerite is assumed to be the primary zinc mineral. Lead is abundant enough so that galena could exist as the primary lead mineral. The pods are too small and lean to be of significance, but they are probably distal phases of the igneous-affiliated mineral deposits of the area. The existence of anomalous quantities of molybdenum suggests a distal relation to nearby molybdenum deposits, as at the Nunatak (MF036).
Workings: There are no workings. A sample of a partly oxidized sulfide pod in limestone exposed at the site contained 7000 ppm zinc, 500 ppm lead, 70 ppb cadmium, 30 ppm molybdenum and 1.5 ppm silver (MacKevett and others, 1971).
Age: Cretaceous or younger.
Commodities (Major) - Zn; (Minor) - Ag, Cd, Mo, Pb
Development Status: No
Deposit Model: Distal sulfide-rich replacement pods in limestone.
6 entries listed. 6 valid minerals.
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Cobb, E.H., 1972, Metallic mineral resources map of the Mount Fairweather quadrangle, AK: U.S. Geological Survey Miscellaneous Field Study Map MF-436, 1 sheet, scale 1:250,000. Kimball, A.L., Still, J.C., and Rataj, J.L., 1978, Mineral resources, in Brew, D. A., and others, Mineral resources of the Glacier Bay National Monument wilderness study area, Alaska: U.S. Geological Survey Open-File Report 78-494, p. C1-C375. MacKevett, E.M., Jr., Brew, D.A., Hawley, C.C., Huff, L.C., and Smith, J.G., 1971, Mineral resources of Glacier Bay National Monument, Alaska: U.S. Geological Survey Professional Paper 632, 90 p., 12 plates, scale 1:250,000.