Breccia (south of Snowcap Mountain)

Occurrence, Inactive

Commodities and mineralogy

Main commodities Ag; Au; Cu
Other commodities Bi
Ore minerals arsenopyrite; chalcopyrite; galena; pyrite; pyrrhotite; sphalerite
Gangue minerals calcite; chlorite; epidote; quartz; sericite; tourmaline

Geographic location

Quadrangle map, 1:250,000-scale LH
Quadrangle map, 1:63,360-scale B-2
Latitude 61.4203
Longitude -153.5792
Nearby scientific data Find additional scientific data near this location
Location and accuracy This occurrence is at an elevation of about 4,500 feet on the east side of a small glacier, 2.9 miles southeast of Snowcap Mountain. It is in the SE1/4 section 4, T 15 N, R 24 W, of the Seward Meridian. The location is accurate to within 0.2 mile.

Geologic setting

Geologic description

A tourmaline-cemented breccia as much as 80 feet across is present in monzogranite at this locality (Gamble and others, 1989). The breccia, includes vein quartz, light-colored angular rock fragments, and monzogranite clasts to about 3 feet across suspended in a black tourmaline matrix that also contains lesser amounts of sericite, quartz, calcite, and chlorite. Discontinuous quartz-tourmaline-sulfide veins to a foot wide cut the breccia along vertical, north-south-trending fractures. Sulfides in the veins include arsenopyrite, chalcopyrite, pyrrhotite, pyrite, and lesser amounts of galena and sphalerite; gangue minerals include quartz, tourmaline, chlorite, and epidote. A composite grab sample of 5 veins in the breccia contains as much as 4.1 ppm gold, 7 ppm silver,and greater than 2,000 ppm arsenic. Selected sulfide-rich samples contain as much as 21 ppm gold, 150 ppm silver, 10,000 ppm copper, and greater than 2,000 ppm arsenic and 1,000 ppm bismuth (Gamble and others, 1989).
Geologic map unit (-153.58145691223, 61.419648941582)
Mineral deposit model Tourmaline-cemented breccia in granitic rocks
Age of mineralization Cretaceous or Tertiary? The breccia and veins crosscut granitic rocks that may be Late Cretaceous or Tertiary parts of the Alaska-Aleutian Range batholith.
Alteration of deposit Tourmaline replacement and veining.

Production and reserves

Workings or exploration Reconnaissance sampling has been done in this area (Gamble and others, 1989).
Indication of production None