Latitude: 63°13'55"N
Longitude: 149°37'11"W
Location: The Banner prospect is at an elevation of about 2,600 feet, about 1.1 mile southwest of the confluence of Bryn Mawr Creek and the West Fork of Chulitna River. It is in SE1/4 sec. 27, T. 19 S., R. 10 W., of the Fairbanks Meridian. The location is accurate to within 1,000 feet. This is locality 2-3 of Hawley and Clark (1974).
Geology: In the area of the Banner prospect, the northeast-trending Banner fault separates unaltered Triassic sedimentary rocks on the southeast from strongly altered Triassic conglomerate, hornfels, and marble on the northwest. The altered rocks are cut by skarn zones extending 500 feet from the fault zone. The deposit consists of sulfide-bearing skarn and quartz-sericite veins that cut the skarn. Sulfides in the skarn zones vary in content, but average about 10%. They consist of arsenopyrite, pyrrhotite, pyrite, chalcopyrite (unpublished report by Addwest Minerals International Ltd., 1997). Copper content ranges up to 1% and gold values run 0.4 to 1 ounce per ton. The Banner skarn deposit probably is related to an apophysis of the Upper Cretaceous (70-65 Ma) porphyry plug at the Golden Zone mine (HE043).
Workings: Workings consist of surface trenches and two holes drilled to a maximum depth of 300 feet. Copper content ranges up to 1% and gold values run 0.4 to 1 ounce per ton.
Age: The skarns are probably related to an apophysis of the Upper Cretaceous (70-65 Ma) porphyry plug at the Golden Zone mine (HE043). The quartz-sericite veins may be Tertiary.
Alteration: Pyrite-quartz-sericite veins overprint earlier skarn calc-silicate assemblages that consist of epidote, pyroxene, actinolite, and occasional garnet.
Commodities (Major) - Ag, Au, Cu
Development Status: None
Deposit Model: Cu skarn and polymetallic veins (Cox and Singer, 1986; models 18b, 22c)
References
Hawley, C.C., and Clark, A.L., 1974 (1975), Geology and mineral deposits of the upper Chulitna district, Alaska: U.S. Geological Survey Professional Paper 758-B, p. B1-B47, 2 plates, scale 1:12,000 and 1:48,000. Hawley, C.C., and others, 1978, Mineral appraisal of lands adjacent to Mt. McKinley National Park, Alaska. Contract No. JO166107: U.S. Bureau of Mines Open-File Report 24-78, 274 p., 12 sheets.
Mineral List
6 entries listed. 5 valid minerals.
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