Junior Prospect, Alaska Peninsula District, Aleutians East Borough, Alaska, USA
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Location: The Junior prospect is on Unga Island approximately 2.5 miles northeast of Acheredin Bay. The map site is near the top of hill 1055, in the NE1/4 of sec. 21, T. 57 S., R. 75 W., Seward Meridian (Wilson and others, 1988, locality 30). The location is accurate to within 1,200 feet.
Geology: The Junior prospect is a 4,000- by 200-foot area of quartz-pyrite-chlorite-zeolite veinlets, pyritic chalcedonic quartz veins, and pyrite-quartz stringers, all cutting chloritized andesite of the late Eocene to early Oligocene Popof volcanic rocks (Wilson and others, 1995). Gangue minerals also locally include calcite and jasper. Peterson and others (1982) believed that the prospect is at the intersection of northeast- and northwest-striking faults. In addition to being chloritized, the andesite is marked by local silicification near the veins, especially in areas of high vein density. Only sporadic occurrences of gold have been noted. The best values were 2.2 ppm gold and 14 ppm silver in a grab sample. In drill core, the highest gold values were 0.03 ppm over 5 feet and 0.02 ppm over 1, 5, and 10 feet (Trujillo and others, 1981). Silver was at least 0.1 ppm over the entire hole (522 feet), with best values at 2.75 ppm in three 3- to 5-foot sections. Mercury ranged from 0.1 to more than 10 ppm and arsenic from 205 to more than 1,000 ppm.
Workings: In 1981 Resource Associates of Alaska mapped the prospect, collected 145 rock and 309 soil samples, conducted a magnetic survey, and drilled one hole for a total of 522 feet. Only low precious metal values were detected.
Age: Eocene or younger.
Alteration: The alteration consists of pervasive chloritization and local silicification.
Commodities (Major) - Ag, Au; (Minor) - Hg
Development Status: None
Deposit Model: Epithermal gold veins
Mineral List
6 entries listed. 3 valid minerals.
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References
Trujillo, R.S., Anderson, G., 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. 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.
