Unnamed Occurrence (ARDF - KC019), Misty Fiords National Monument, Ketchikan District, Prince of Wales-Outer Ketchikan Borough, Alaska, USA
Site is in Misty Fiords National Monument Wilderness.
Location: This occurrence is at an elevation of about 600 feet in cliffs east of the Chickamin River, about 2 miles north of the mouth of the South Fork. The site is in section 16, T. 69 S., R. 96 E., of the Copper River Meridian. It corresponds to area M-4 in Berg and others (1977), and to loc. 19 in Elliott and others (1978). The location is accurate within 0.1 mile.
Geology: The country rocks in the area of this occurrence consist chiefly of rusty-weathering pelitic paragneiss that forms roof pendants, screens, and inclusions in Tertiary or Cretaceous foliated granodiorite and quartz diorite of the Coast Range batholith (Berg and others, 1977, p. 126; Berg and others, 1988). The paragneiss probably represents marine argillaceous and clastic strata that underwent high-grade regional metamorphism in Cretaceous or Tertiary time. The premetamorphic age of the strata is uncertain, but they probably are mainly Paleozoic and may be as old as Precambrian (Berg and others, 1988, p. 26; Gehrels and others, 1990; Crawford and others, 2000). The occurrence consists of a zone of rusty-weathering pyritic paragneiss and schist, whose foliation strikes N30W and dips 55NE. The zone is about 450 feet thick and its outcrop can be traced along strike to the southeast for about 3 miles (Berg and others, 1977, p. 126 and pl. 2). The zone probably is the southeast extension of a similar rusty zone on the other side of Chickamin River (KC018). In addition to locally abundant pyrite, the rocks contain sparse chalcopyrite. Chip samples taken perpendicular to the foliation across about 350 feet of the zone assayed up to 150 ppm Mo, 95 ppm Cu, 15 ppm Pb, 80 ppm Zn, and 1 ppm Ag. One sample contained a trace (less than 0.05 ppm) of gold (Berg and others, 1977, p. 126 and fig. 36).
Workings: Thirteen chip samples taken perpendicular to the foliation across about 350 feet of a 600-foot-thick zone of iron-stained paragneiss assayed up to 150 ppm Mo, 95 ppm Cu, 15 ppm Pb, 80 ppm Zn, and 1 ppm Ag. One sample contained a trace (less than 0.05 ppm) of gold (Berg and others, 1977, p. 126 and fig. 36).
Alteration: Conspicuous iron-staining.
Commodities (Major) - Cu, Mo; (Minor) - Ag?, Pb, Zn
Development Status: None
Deposit Model: Disseminated base-metal sulfides in rusty-weathering paragneiss
| Chalcopyrite|| Pyrite|
2 entries listed. 2 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. Berg, H.C., Elliott, R.L., and Koch, R.D., 1988, Geologic map of the Ketchikan and Prince Rupert quadrangles, southeastern Alaska: U.S. Geological Survey Mineral Investigations Series Map I-1807, 27 p., scale 1:250,000. Crawford, M.L., Crawford, W.A., and Gehrels, G.E., 2000, Terrane assembly and structural relationships in the eastern Prince Rupert quadrangle, British Columbia, in H.H. Stowell and W.C.McClelland, eds., Tectonics of the Coast Mountains, southeastern Alaska and British Columbia: Geological Society of America Special Paper 343, p. 1-21. Elliott, R.L., Berg, H.C., and Karl, S.M., 1978, map and table describing metalliferous and selected non-metalliferous mineral deposits, Ketchikan and Prince Rupert quadrangles, Alaska: U.S. Geological Survey Open-File Report 78-73-B, 17 p., 1 sheet, scale 1:250,000. Gehrels, G.E., McClelland, W.C., Samson, S.D., Patchett, P.J., and Jackson, J.L., 1990, Ancient continental margin assemblage in the northern Coast Mountains, southeast Alaska and northwest Canada: Geology, v. 18, no. 3, p. 208-211.
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