Unnamed Prospect (ARDF - PM011; northeast of Canoe Bay), Alaska Peninsula District, Aleutians East Borough, Alaska, USA
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Location: This prospect is located on the Alaska Peninsula approximately 1.5 miles northeast of the shore of Canoe Bay and 2.5 miles southwest of Knutson Lake (Nokleberg and others, 1987, locality AP2; Wilson and others, 1988, locality 49). The map site is at an elevation of 1,100 feet, in the SE1/4 of sec. 8, T. 53 S., R. 78 W., of the Seward Meridian. The location is accurate to within 1,200 feet.
Geology: This prospect is localized in a domical intrusive complex of Pliocene or Quaternary age that cuts sedimentary rocks of the Upper Cretaceous Hoodoo Formation (Wilson and others, 1995). The complex contains two rhyolites that are in part intrusive and in part extrusive, a rhyodacite quartz porphyry, several tuff units, and narrow dikes of quartz-sericite-pyrite-feldspar porphyry. Soil samples have defined potentially mineralized areas, but visible gold in rock samples or mineralized quartz veins have not been found. The soils contained as much as 5.2 ppm gold and 8.4 ppm mercury. On the basis of the soil geochemical surveys, Trujillo and others (1982) infer two types of mineralization: a pervasive type occurring in the older rhyolite in areas of argillization and silicification; and an east-west-trending linear type 900 to 3,600 feet in length and cutting several rock types. The older rhyolite also displays a radial pattern of soil anomalies interpreted to be related to tensional cracks that served as conduits for mineralizing fluids. Channel samples of sericitized lithic tuff contained as much as 3.45 ppm gold, 6.5 ppm silver, 258 ppm copper, 23 ppm lead, 675 ppm zinc, 212 ppm arsenic, and 0.941 ppm mercury. Grab samples of the older rhyolite contained as much as 0.90 ppm gold, 0.8 ppm silver, 44 ppm copper, 87 ppm lead, 120 ppm zinc, 231 ppm arsenic, and 0.29 ppm mercury (Trujillo and others, 1982). Freeport Exploration Company in 1984 identified two areas of anomalous soils. One contained 0.5 ppm gold over an area 400 by 1,200 feet. Trenching revealed a fault marked by only minor gold values. A second area of soils contained 0.3 ppm gold in an area 100 by 800 feet (Freeport Exploration Company, 1985). A possible source of some of the gold soil anomalies may be gold-bearing volcanic ash from Mount Dana.
Workings: Resource Associates of Alaska mapped the prospect, conducted VLF-EM surveys, and collected 1,350 rock and soil samples during the period 1979 to 1983. In 1984 Freeport Exploration Company collected 600 soil and rock samples, dug five backhoe trenches for a total of 700 feet, and hand-dug several hundred feet of trenches. Channel samples of a tuff unit contained as much as 3.45 ppm gold and 6.5 ppm silver. Grab samples of the older rhyolite returned values of as much as 0.90 ppm gold and 0.8 ppm silver. The U.S. Geological Survey collected several samples at this site in the mid-1980s.
Age: Pliocene or younger.
Alteration: Freeport Exploration Company (1985) identified phyllic, propylitic, and argillic alteration phases within the intrusive complex. The phyllic phase, thought to be the oldest, consists of moderate to strong sericitization, quartz overgrowths, and disseminated pyrite. Propylitic alteration cross-cuts and overprints the phyllic phase. Argillic alteration is restricted to faults and fractures and cross-cuts the other phases. Trujillo and others (1982) reported the argillic alteration to be widespread, intense, and pervasive.
Commodities (Major) - Ag, Au; (Minor) - As, Cu, Hg, Pb, Zn
Development Status: No
Deposit Model: Hot-spring Au-Ag? (Cox and Singer, 1986; model 25a)
Mineral List
2 entries listed. 2 valid minerals.
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References
Anderson, G.L., Butherus, D.L., Fankhauser, R.E., Pray, J.C., Lindberg, P.A., and Hoffman, B.L., 1980, Exploration and evaluation of lands leased from Aleut Native Corporation 1980: Resource Associates of Alaska Report, 84 p, 16 map sheets, various scales. (Report held by the Aleut Corporation, Anchorage, Alaska.) Angeloni, L.M., Wilson, F.H., and Sutley, Stephen, 1985, Map and tables showing preliminary rock geochemical data, Port Moller, Stepovak Bay, and Simeonof Island quadrangles, Alaska: U.S. Geological Survey Open-File Report 85-470, 179 p., 1 sheet, scale 1:250,000. Butherus, D. L., Gressitt, E.E., Pray, J., Corner, N.G., Lindberg, P.A., Fankhauser, R.E., 1979, Exploration and evaluation of the Aleut Native Corporation lands: Resource Associates of Alaska Report, 69 p, 90 map sheets, various scales. (Held by the Aleut Corporation, Anchorage) Freeport Exploration Company, 1985, 1984 report of activities, Canoe Bay joint venture: Freeport Exploration Company, 25 p. (Report held by the Aleut Corporation, Anchorage, Alaska.) Nokleberg, W.J., Bundtzen, T.K., Berg, H.C., Brew, D.A., Grybeck, D.J., Robinson, M.S., Smith, T.E., and Yeend, W., 1987, Significant metalliferous lode deposits and placer districts of Alaska: U.S. Geological Survey Bulletin 1786, 104 p., 2 plates, scale 1:5,000,000. Trujillo, R.S., Tapper, C.J., Alvarez, T.J., Porterfield, Ben, and Toupe, W.M., 1982, Exploration and evaluation of precious metal potential of portions of Aleut Corporation lands, southwest Alaska 1982: Resource Associates of Alaska unpublished report, 91 p, 33 maps, various scales. (Report held by the Aleut Corporation, Anchorage, Alaska.) Wilson, F.H., Detterman, R.L., Miller, J. W., and Case, J.E., 1995, Geologic map of the Port Moller, Stepovak Bay, and Simeonof Island quadrangles, Alaska: U.S. Geological Survey Miscellaneous Investigation Series Map I-2272, 1 sheet, scale 1:250,000. Wilson, F.H., White, W.H., and DuBois, G.D., 1988, Brief descriptions of mines, prospects, and mineral occurrences in the Port Moller and Stepovak Bay quadrangles, Alaska Peninsula: U.S. Geological Survey Open-File Report 88-666, 128 p., 1 plate, scale 1:250,000.
