Unnamed Occurrence (ARDF - KC023), Walker Cove, Misty Fiords National Monument, Ketchikan District, Prince of Wales-Outer Ketchikan Borough, Alaska, USA

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Site is in Misty Fiords National Monument Wilderness.
Location: 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.
Geology: 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.
Workings: 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.
Age: Fissure veins probably are Cretaceous or younger.

Commodities (Major) - Cu, Mo; (Minor) - Ag
Development Status: None
Deposit Model: Polymetallic veins (Cox and Singer, 1986; model 22c)

Mineral List

Chalcopyrite

Molybdenite

Pyrite

Quartz

4 entries listed. 4 valid minerals.

References