|Quadrangle map, 1:250,000-scale||PM|
|Quadrangle map, 1:63,360-scale||A-2|
|Nearby scientific data||Find additional scientific data near this location|
|Location and accuracy||This prospect is located on Unga Island approximately 1 mile southeast of Red Mountain and 1 mile west of Bloomer Peak (Wilson and others, 1988, locality 27). The location is accurate to within 1,200 feet.|
This prospect occurs in rocks mapped as late Eocene to early Oligocene Popof volcanic rocks (Wilson and others, 1995). In the immediate area of the prospect an interlayered sequence of silicified and argillized andesitic crystal and lithic tuffs is overlain by unaltered dacite tuff (Ellis and Apel, 1990). A diorite plug crops out in the southeast part of the area.
Silica-replaced permeable tuffs are best exposed at the discovery site, defined in 1979 and 1980 by Resource Associates of Alaska as a siliceous knob (Anderson and others, 1980). Other less exposed zones of silica replacement, siliceous breccias, and areas of clay-pyrite alteration occur throughout the area. The siliceous zones appear to grade laterally into argillically altered rock.
The knob contains pyritic zones and abundant drusy quartz veins. Two stages of silicification have been recognized. The earlier is a pervasive replacement by amorphous silica and the later is represented by small, discontinuous quartz veins. A hot-springs origin of the silica has been suggested by Trujillo and others (1981). Sparse quartz-barite veins contain as much as 11.8 ppm gold, 19 ppm silver, 1,000 ppm lead, 750 ppm arsenic, 170 ppm mercury, and 150 ppm antimony (Trujillo and others, 1981).Drilling of the knob in 1981 and 1983 by Resource Associates of Alaska and UNC Teton Exploration Drilling Company penetrated a 60- and a 90-foot zone of intense silicification. These holes contained as much as 0.085 ppm gold, 4.25 ppm silver, 55 ppm arsenic, and 5 ppm or more mercury.
|Geologic map unit||(-160.595045758918, 55.2111689893848)|
|Mineral deposit model||Epithermal gold veins, Hot-springs Au-Ag (Cox and Singer, 1986; model 25a)|
|Mineral deposit model number||25a|
|Age of mineralization||Eocene or younger.|
|Alteration of deposit||The rocks exhibit intense silicification and argillization.|
|Workings or exploration||From 1979 to 1983, Resource Associates of Alaska and UNC Teton Exploration Drilling Company mapped and sampled the prospect, ran magnetometer and EM surveys, and drilled two core holes for a total of 339 feet. They collected 270 soil and about 100 rock samples. In 1990 Battle Mountain Exploration Company mapped and sampled the prospect and relogged the core.|
|Indication of production||None|
Andersen, G.D., 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.)
Ellis, W.T., and Apel, R.A., 1990, Unga/Alaska Peninsula 1990 final report: Battle Mountain Exploration Company report, 49 p., 29 map sheets at various scales. (Report held by the Aleut Corporation, Anchorage, Alaska.)
Peterson, R.J., Handverger, P., Rosenkrans, D., Bartels, E, and Woolston, D., 1983, Shumagin Islands precious metal exploration program southwest Alaska: UNC Teton Exploration Drilling Company report, 61 p. (Report held by the Aleut Corporation, Anchorage, Alaska.)
Trujillo, R.S., Andersen, G.D., MacLeod, T., Hendrick, K., Farnham, S., Peterson, J., 1981. Exploration and evaluation of the Unga-Popof-Korovan Islands portion of lands leased from Aleut Native Corporation: Resource Associates of Alaska report, 70 p., 38 map sheets, 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.
|Last report date||1/9/2001|