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Unnamed (north shore of Walker Cove)

Occurrence, Undetermined

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Commodities and mineralogy

Main commodities Cu; Mo
Other commodities Ag
Ore minerals chalcopyrite; molybdenite; pyrite
Gangue minerals quartz

Geographic location

Quadrangle map, 1:250,000-scale KC
Quadrangle map, 1:63,360-scale C-3
Latitude 55.729
Longitude -130.859
Nearby scientific data Find additional scientific data near this location
Location and accuracy This occurrence is on the north shore of Walker Cove 1.9 miles east-northeast of its mouth. The site is in section 9, T. 71 S., R. 95 E., of the Copper River Meridian. It corresponds to area G-7 in Berg and others (1977, p. 134), and to loc. 23 in Elliott and others (1978). The location is accurate within 0.1 mile.

Geologic setting

Geologic description

The country rocks in the area of this site are Tertiary or Cretaceous foliated quartz diorite and granodiorite of the Coast Range batholith, and pelitic paragneiss that forms roof pendants, screens, and inclusions in the batholith (Berg and others, 1988). The metamorphic sequence represents marine 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 quartz stringers and fissure(?) veins up to about 2 feet thick that cut paragneiss and gneissic quartz diorite. Most of the veins are apparently barren, but one two-foot-thick vein contains several volume percent of pyrite, and minor amounts of chalcopyrite and molybdenite (Berg and others, 1977, p. 134). Some of the paragneiss country rock near the veins contains small pods, stringers, and disseminations of pyrite. A grab sample of this paragneiss contained 3.0 ppm Ag. Chip samples of the richest section of the two-foot-thick quartz vein contained 900 ppm Cu, 70 ppm Mo, 0.1 ppm Au, 1.0 ppm Ag, and less than 5 ppm Pb (Berg and others, 1977, p. 135). Chip samples of the quartz diorite, paragneiss, and other quartz veins assayed up to 110 ppm Cu, 10 ppm Pb, 100 ppm Zn, 5 ppm Mo, and 1.0 ppm Ag.
Geologic map unit (-130.860705107745, 55.7286548807868)
Mineral deposit model Polymetallic veins (Cox and Singer, 1986; model 22c)
Mineral deposit model number 22c
Age of mineralization Fissure veins probably are Cretaceous or younger.

Production and reserves

Workings or exploration A grab sample of sulfide-bearing paragneiss contained 3.0 ppm Ag. Chip samples of the richest section of a two-foot-thick sulfide-bearing quartz vein contained 900 ppm Cu, 70 ppm Mo, 0.1 ppm Au, 1.0 ppm Ag, and less than 5 ppm Pb (Berg and others, 1977, p. 135). Chip samples of quartz diorite, paragneiss, and other quartz veins assayed up to 110 ppm Cu, 10 ppm Pb, 100 ppm Zn, 5 ppm Mo, and 1.0 ppm Ag.
Indication of production None

Additional comments

Site is in Misty Fiords National Monument Wilderness.

References

MRDS Number A012300

References

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.
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.
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.
Reporters H.C. Berg, USGS
Last report date 6/29/1999