Top Prospect, Hyder District, Prince of Wales-Outer Ketchikan Borough, Alaska, USA
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Geology: The country rocks in the area of the Top prospect are pelitic metasedimentary and subordinate andesitic metavolcanic strata of the Jurassic or older Mesozoic Hazelton Group; the Triassic Texas Creek Granodiorite, which underlies and locally intrudes the Hazelton; and the Eocene Hyder Quartz Monzonite, which intrudes the Hazelton and Texas Creek rocks(Smith, 1977; Koch, 1996). According to Maas and others (1995, p. 254, 258), the deposit consists of disseminated and semi-massive pyrite, sphalerite, and tetrahedrite, and a quartz-sulfide vein. The deposit is hosted in Hazelton volcanic rocks and has been exposed for a length of about 450 feet. Maas and others (p. 254) suggest that this deposit is Jurassic in age, based on similarities in mineralogy, structural setting, and hostrock, to isotopically-dated Jurassic deposits elsewhere in the Hyder district (for example, see BC065, BC067). If so, the deposit is contemporaneous, at least in part, with island-arc volcanism in Hazelton time (Alldrick, 1993).
Workings: The deposit has been exposed by surface trenching for about 450 feet. Samples collected by the U.S. Bureau of Mines in 1992 or 1993 (Maas and others, 1995, p. 258) contain up to 48.03 ppm Au, 100.8 ppm Ag, and 10.3% Zn.
Age: Maas and others (1995, p. 254) suggest that this deposit is Jurassic in age, based on similarities in mineralogy, structural setting, and hostrock, to isotopically-dated Jurassic deposits elsewhere in the Hyder district (for example, see BC065, BC067). If so, the deposit is contemporaneous, at least in part, with island-arc volcanism in Hazelton time (Alldrick, 1993).
Alteration: Volcanic hostrocks are impregnated with sulfide minerals.
Commodities (Major) - Ag, Au, Zn
Development Status: None
Deposit Model: Polymetallic veins
Mineral List
4 entries listed. 4 valid minerals.
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References
Alldrick, D.J., 1993, Geology and metallogeny of the Stewart mining camp, northwestern British Columbia: British Columbia Department of Mines and Petroleum Resources Bulletin 85, 105 p., 2 plates, scale 1:50,000. 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. Smith, J.G., 1977, Geology of the Ketchikan D-1 and Bradfield Canal A-1 quadrangles, Alaska: U.S. Geological Survey Bulletin 1425, 49 p., 1 plate.