Nunatak (south of Snowcap Mountain)

Occurrence, Inactive

Commodities and mineralogy

Geographic location

Quadrangle map, 1:250,000-scale LH
Quadrangle map, 1:63,360-scale B-2
Latitude 61.4068
Longitude -153.6225
Nearby scientific data Find additional scientific data near this location
Location and accuracy This occurrence is at an elevation of 5,500 feet on the south end of a small nunatak, 3.25 miles south of Snowcap Mountain. It is in the NW1/4 section 8, T 15 N, R 24 W, of the Seward Meridian. This location is accurate; other vein occurrences are within a quarter of a mile of this location (Gamble and others, 1989).

Geologic setting

Geologic description

Barren quartz veins, quartz-amphibole veins, and sulfide-bearing veins occupy east-west trending, sub-vertical fractures in biotite-hornblende monzodiorite to quartz monzodiorite in this area (Gamble and others, 1989). Two sulfide-bearing veins at an elevation of 5,500 feet on the south end of a small nunatak are about 1 to 2 feet wide and contain 5 to 70 percent chalcopyrite, arsenopyrite, and magnetite, and lesser amounts of galena, sphalerite, pyrite, and pyrrhotite. Erythite (cobalt bloom) is locally present and gangue minerals in the sulfide-bearing veins include amphibole, apatite, clinopyroxene, chlorite, epidote, quartz, and plagioclase. Composite chip samples of these veins contain as much as 1.5 ppm gold, 150 ppm silver, and greater than 20,000 ppm copper, 2,000 ppm arsenic, and 2,000 ppm copper. Apatite is locally abundant in the veins, and some samples contain as much as 1 percent phosphorus. Other sulfide-rich samples from the area contain up to 12 ppm gold, 700 ppm silver, and 640 ppm bismuth, and greater than 20,000 ppm copper, 2,000 ppm arsenic, and 2,000 ppm cobalt. A sample that contains greater than 20,000 ppm arsenic, 5,000 ppm cobalt, and 10,000 ppm nickel and only 7 percent iron may be glaucodot- or alloclasite-bearing (Gamble and others, 1989). The gangue mineralogy of the sulfide-bearing veins may indicate that they are in part mineralized mafic dikes.
Geologic map unit (-153.624762035641, 61.4061459542511)
Mineral deposit model Polymetallic veins? (Cox and Singer, 1986, model 22c)
Mineral deposit model number 22c?
Age of mineralization Cretaceous or Tertiary? The veins crosscut granitic rocks that may be Late Cretaceous or Tertiary parts of the Alaska-Aleutian Range batholith.
Alteration of deposit The sulfide-bearing veins may be variably altered and replaced mafic dikes.

Production and reserves

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

References