Unnamed (western Mitrofania Island)

Occurrence, Inactive

Commodities and mineralogy

Main commodities Ag; Au; Pb; Zn
Other commodities As; Bi; Cu; Sb
Ore minerals pyrite; unidentified sulfides
Gangue minerals calcite; quartz

Geographic location

Quadrangle map, 1:250,000-scale SB
Quadrangle map, 1:63,360-scale D-3
Latitude 55.848
Longitude -158.88
Nearby scientific data Find additional scientific data near this location
Location and accuracy This site is located on the west shore of Mitrofania Island, 0.6 mile west-northwest of the top of hill 1660. It is referred to as SBRGX-44 in Wilson and others (1988, locality 18). The location is accurate to within 2,500 feet.

Geologic setting

Geologic description

This occurrence is in an area mapped as undivided Tertiary volcanic rocks (Wilson and others, 1995). Small plutons of Miocene or Pliocene granodiorite to quartz diorite crop out a few miles to the north and south of the occurrence (Wilson and others, 1995). At this site, fractured and silicified volcanic flows are cut by numerous quartz-calcite veinlets as much as 2 inches thick, which fill the fracture zones (Wilson and others, 1988). Some veinlets carry as much as 80 to 90 percent pyrite and other, unidentified, sulfides. Rock samples collected by the U.S. Geological Survey contained 10 ppm or less gold, and as much as 500 ppm antimony, 26,000 ppm arsenic, 1,500 ppm copper, 300 ppm lead, 50 ppm silver, and 10,000 ppm or more zinc (Angeloni and others, 1985; Wilson and others, 1988). Bismuth is also reported in some of the analyses.
Geologic map unit (-158.882003045233, 55.8472141721102)
Mineral deposit model Polymetallic veins (Cox and Singer, 1986; model 22c).
Mineral deposit model number 22c
Age of mineralization Tertiary.
Alteration of deposit Silicification.

Production and reserves

Workings or exploration Rock samples 84AGe10-16 collected by the U.S. Geological Survey in the mid-1980s, contained 10 ppm or less gold, and as much as 500 ppm antimony, 26,000 ppm arsenic, 1,500 ppm copper, 300 ppm lead, 50 ppm silver, and greater than 10,000 ppm zinc (Angeloni and others, 1985; Wilson and others, 1988). Bismuth is also reported in some of the analyses.
Indication of production None

Additional comments

This site is located on land selected by the Bristol Bay Native Corporation.

References