Mountain Top Mine, Aniak Mining District, Bethel Census Area, Alaska, USAi

Regional Level Types
Mountain Top Mine	Mine
Aniak Mining District	Mining District
Bethel Census Area	Census Area
Alaska	State
USA	Country

Location: The Mountain Top Mine is on a small plateau about 4.2 mile east-northeast of Chineekluk Mountain. It is at an elevation of about 1400 feet, about 0.6 mile northwest of the center of sec. 18, T. 15 N., R. 48 W., of the Seward Meridian. The location is accurate. The mine is locality 34 of Miller and others (1989).
Geology: The rocks in the vicinity of the Mountain Top Mine consists of thermally altered, olivine basalt that overlies(?)sandstone and siltstone of the Upper Cretaceous, Kuskokwim Group (Cady and others, 1955; Sorg and Estlund, 1972). The basalt is interpreted to be a large dike by Sorg and Estlund (1972); a flow by Reifenstuhl and others (1984) and by the reporters of this record (T.K. Bundtzen and M.L. Miller, unpublished field data, 1988). A series of four, en echelon, high-angle faults cut the olivine basalt; the faults strike about N50W, and dip about 80NE (T.K. Bundtzen and M.L. Miller, unpublished prospect map, 1988). The faults are filled with cinnabar, pyrite, and minor stibnite, in a gangue that consists of carbonate minerals and euhedral crystals of quartz. The individual ore zones range from 120 to 190 feet long and 4 to 18 inches thick. Sorg and Estlund (1972) reported that small amounts of liquid hydrocarbon accompany the cinnabar; they also identified dickite and buddingtonite in the mineralized zones. Their mineralized grab samples contained up to 2.00 percent mercury, 1,500 parts per million (ppm) chromium, 100 ppm cobalt, 1,500 ppm arsenic, and 1.5 ppm silver. The high chromium and cobalt probably reflect high background values in the mafic host rocks. Up to 300 parts per billion gold were identified in cinnabar-rich zones (Robinson, 1984 [RI 84-11]). From 1982-1986, about 165 flasks (about 12,540 pounds) of mercury were produced from the Mountain Top Mine (Bundtzen and others, 1987; Miller and others, 1989).
Workings: James R. Wylie discovered the Mountain Top deposit in 1968 after panning cinnabar to its hardrock source. J. R. Wylie subsequently explored the deposit with an auger drill and a bulldozer. In 1970, the U.S. Bureau of Mines drilled seven core holes on the property, the deepest of which was 50 feet. Sorg and Estlund (1972) published a detailed geologic map of the property in 1971. The reporters of this record made a geologic sketch of the property in 1988 (T.K. Bundtzen and M.L. Miller, unpublished. data) In 1988, a D-6 bulldozer, a small ball mill, a jig plant, and a retort furnace were on the mine site.
Age: Undated; the nearby Fairview prospect (ARDF SM019) has a 40Ar/39Ar age of 72.6 Ma (Gray, Gent, and others, 1997).
Alteration: Mafic dikes are altered to dickite and buddingtonite.
Production: From 1982 to 1986, about 165 flasks of mercury were produced from the Mountain Top Mine (Bundtzen and others, 1987; Miller and others, 1989).
Reserves: According to Sorg and Estlund (1972), there were 200 flasks of mercury 'in sight' in 1971.

Commodities (Major) - Hg; (Minor) - Ag, As, Au, Co, Cr, Sb
Development Status: Yes; small
Deposit Model: Silica-carbonate mercury? (Cox and Singer, 1986; model 27c).

Other Databases

Link to USGS - Alaska:	SM058

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References