Marmot upper basin Prospect, Hyder District, Prince of Wales-Outer Ketchikan Borough, Alaska, USA
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Location: The Marmot upper basin prospect (Berg and others, 1977, p. 106) is in Section 26 on the southeast side of Banded Mountain at an elevation of about 4600 to 4750 feet. This location is accurate to within about a quarter of a mile.
Geology: The country rocks in the general area of this prospect (Berg and others, 1977, p. 15-18, 22; Koch, 1996) are banded variegated pelitic hornfels, phyllite, and fine-grained schist of the Jurassic or older Mesozoic Hazelton Group. The metasedimentary rocks are intruded by andesite dikes that may be apophyses of the Triassic Texas Creek Granodiorite, and by aplite dikes that may be apophyses of Eocene Hyder Quartz Monzonite. The mineral deposit (Berg and others, 1977, p. 100, 106, 110, 112; Elliott and Koch, 1981, p. 9, loc. 19) consists of a stockwork(?) of quartz [-calcite] veins up to about 3 feet thick in locally iron-stained dark pelitic hornfels of the Hazelton Group. The veins contain pyrite, chalcopyrite, molybdenite, and galena. The highest assay values reported from vein and hostrock samples collected by the U.S. Bureau of Mines in 1972 were 2000 ppm Mo, 5000 ppm Pb, 3000 ppm Cu, 150 ppm Ag, and 0.1 ppm Au. Lead-isotope studies of the galena at the Marmot upper basin prospect (Maas and others, 1995, p. 229-248) indicate that the deposit is Eocene in age, contemporaneous with emplacement of the Hyder Quartz Monzonite.
Workings: Highest assay values reported from veins and hostrock samples collected by U.S. Bureau of Mines in 1972 were 2000 ppm Mo, 5000 ppm Pb, 3000 ppm Cu, 150 ppm Ag, and 0.1 ppm Au.
Age: Lead-isotope studies of the galena at the Marmot upper basin prospect (Maas and others, 1995, p. 229-248) indicate that the deposit is Eocene in age, contemporaneous with emplacement of the Hyder Quartz Monzonite.
Alteration: Local intense iron staining
Commodities (Major) - Ag, Cu, Mo, Pb; (Minor) - Au, Zn
Development Status: None
Deposit Model: Polymetallic veins
6 entries listed. 6 valid minerals.
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Berg, H.C., Elliott, R.L., Smith, J.G., Pittman, T.L., and Kimball, A. L., 1977, Mineral resources of the Granite Fiords Wilderness Study Area, Alaska, with a section on aeromagnetic data by Andrew Griscom: U.S. Geological Survey Bulletin 1403, 151 p. Elliott, R.L., and Koch, R.D., 1981, Mines, prospects, and selected metalliferous mineral occurrences in the Bradfield Canal quadrangle, Alaska: U.S. Geological Survey Open-File Report 81-728-B, 23 p., 1 sheet, scales 1:250,000 and 1:63,360. Koch, R.D., 1996 [In press), Reconnaissance geologic map of the Bradfield Canal quadrangle, southeastern Alaska: U.S. Geological Survey Open-File Report, 1 sheet, scale 1:250,000. Maas, K.M., Bittenbender, P E., and Still, J.C., 1995, Mineral investigations in the Ketchikan mining district, southeastern Alaska: U.S. Bureau of Mines Open-File Report 11-95, 606 p.