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Brenner

Prospect, Inactive

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Commodities and mineralogy

Main commodities Au; Mo; Pb; Zn
Other commodities Cu
Ore minerals arsenopyrite; galena; gold; marcasite; molybdenite; native copper; pyrite; pyrrhotite; sphalerite
Gangue minerals calcite; quartz

Geographic location

Quadrangle map, 1:250,000-scale AN
Quadrangle map, 1:63,360-scale A-6
Latitude 61.045
Longitude -149.115
Nearby scientific data Find additional scientific data near this location
Location and accuracy 500 ft south-southwest of the end of the unimproved road which follows Crow Creek, west of Barnes Mountain. Marked with prospect symbol the Anchorage A-6 1:63,360-scale topographic map. Accurate within 400 ft. Locality 5 on plate 33 of Park (1933), locality 53 of Cobb (1972), locality 42 of MacKevett and Holloway (1977), and locality A-40 of Jansons and others (1984).

Geologic setting

Geologic description

Country rock is Late Cretaceous coarse-grained, massive graywacke of the Valdez Group. Two quartz-calcite veins, averaging 6 in thick, carry galena, sphalerite, pyrite, pyrrhotite, arsenopyrite, molybdenite (?), and marcasite. One vein strikes at N 45 W, and dips 65 N, while the other vein strikes N 35 E. Chalcopyrite and marcasite occur as veinlets in massive pyrrhotite. Pyrrhotite is also found in veinlets with arsenopyrite. Native copper is also reported to be present (Park, 1933).
According to Jansons and others (1984), chip samples contained up to 0.12 oz/ton Au and up to 0.27 oz/ton Ag. Grab samples contained 0.52 oz/ton Au and 0.50 oz/ton Ag. Some samples contain up to 148 ppm Mo, 0.14 percent Cu, and 0.3 percent As.
Geologic map unit (-149.117188865374, 61.0444355687701)
Mineral deposit model Chugach-type low-sulfide Au-quartz veins (Bliss, 1992; model 36a.1).
Mineral deposit model number 36a.1
Age of mineralization Tertiary or younger.
Alteration of deposit The deepest oxidation evident is 30 ft below collar of shaft. Most oxidation is above modern water table (Park, 1933).

Production and reserves

Workings or exploration Park (1933) reports exploration by 175 foot drift along the west vein and a 54 foot inclined shaft with two levels that run along east vein for 80 feet (upper for 30 feet - lower for 50 feet); total underground workings equal 309 feet. Brenner was only prospect in area that has been opened below water table. According to Jansons and others (1984), chip samples contained up to 0.12 oz/ton Au and up to 0.27 oz/ton Ag. Grab samples contained 0.52 oz/ton Au and 0.50 oz/ton Ag. Some samples contain up to 148 ppm Mo, 0.14 percent Cu, and 0.3 percent As.
Indication of production Undetermined
Reserve estimates Reported to have moderate mineral development potential for a small mine (Jansons and others, 1984).

Additional comments

See also: Agostino - ARDF number AN109 and Jewell - ARDF number AN107.

References

MRDS Number A011657

References

Clark, S.H.B., and Yount, M.E., 1972, Reconnaissance geologic map and geochemical analyses of stream-sediment and rock samples of the Anchorage A-6 Quadrangle, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map 351, 2 sheets, scale 1:63,360.
Cobb, E.H., 1972, Metallic mineral resources map of the Anchorage Quadrangle, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map 409, 1 sheet, scale 1:250,000.
Jansons, U., Hoekzema, R.B., Kurtak, J.M., and Fechner, S.A., 1984, Mineral occurrences in the Chugach National Forest, Southcentral Alaska: U.S. Bureau of Mines Open-File Report 5-84, 218 p., 2 sheets, scale 1:250,000.
Park, F.C., 1933, The Girdwood District, Alaska: U.S. Geological Survey Bulletin 849-G, p. 381-424.
Reporters D.P. Bickerstaff (USGS contractor); S.W. Huss (USGS)
Last report date 7/30/1998