Unnamed (in upper Fog Creek)

Occurrences, Inactive

Commodities and mineralogy

Main commodities Au
Other commodities Ag; Bi
Ore minerals pyrite
Gangue minerals calcite; epidote; quartz

Geographic location

Quadrangle map, 1:250,000-scale TK
Quadrangle map, 1:63,360-scale C-3
Latitude 62.7177
Longitude -148.4231
Nearby scientific data Find additional scientific data near this location
Location and accuracy Several occurrences are along a two-mile segment of a ridge, informally called Grizzly Ridge, that is on the west side of upper Fog Creek. The site is centered at an elevation of about 5,000 feet, 0.2 mile east of the center of sec. 1, T. 30 N., R. 5 E., Seward Meridian.

Geologic setting

Geologic description

The rocks in the vicinity of these occurrences are mostly Paleozoic crystal-lithic tuff cut by diabase and gabbro dikes and by other very fine grained, gray, intermediate(?), biotite-bearing intrusions (Csejtey and others, 1978). Cretaceous or Jurassic argillite also occurs in the area. U.S. Geological Survey samples of epidotized tuff contain 0.4 part per million gold; the diabase and gabbro dikes contain 1 percent pyrite and up to 0.3 parts per million gold, with 2 parts per million bismuth (J. Schmidt, written communication, 2001). The very fine grained, gray intrusive rocks are pyritic and contain up to 0.3 parts per million gold and 0.4 parts per million silver. A float sample of quartz-calcite vein breccia contains 0.2 parts per million silver. The argillite locally is pyritic and contains up to 0.5 parts per million silver. (Six samples analyzed by ICP methods by XRAL Laboratories give values that vary from 0.2 to 0.4 part per million gold; fire assays of the samples give values of less than 0.005 part per million gold. The cause of this discrepancy is not known.)
Geologic map unit (-148.425335138496, 62.7172281279086)
Alteration of deposit The fragmental plagioclase crystal/lithic tuff is epidotized (J. Schmidt, written communication, 2001).

Production and reserves

Workings or exploration Only surface sampling by U.S. Geological Survey (J. Schmidt, written communication, 2001).
Indication of production None

References