Unnamed (3850 Nunatak west of Tarr Inlet)

Occurrence, Inactive

Commodities and mineralogy

Main commodities Cu
Other commodities Ag; Zn
Ore minerals chalcopyrite; pyrite; pyrrhotite
Gangue minerals quartz

Geographic location

Quadrangle map, 1:250,000-scale MF
Quadrangle map, 1:63,360-scale D-3
Latitude 58.954
Longitude -136.992
Nearby scientific data Find additional scientific data near this location
Location and accuracy The occurrence is on a nunatak on a 3850-foot largely ice-mantled mountain two miles southwest of Tarr Inlet and three miles northwest of the point between Johns Hopkins Inlet and Tarr Inlet. It is in the NE 1/4 of section 1, T. 34 S., R. 50 E., of the Copper River Meridian and is located within 0.25 mile accuracy. The location is number 27 of Kimball and others (1978).

Geologic setting

Geologic description

The occurrence area is extensively ice-mantled. Generally it is in an area where the country rocks are volcanic rocks of Permian age intruded by granitic rocks of Cretaceous age (Brew and others, 1978). At the occurrence, skarn-like pods of massive sulfide as much as 0.5 foot across occur in marble and volcanic rocks at a granitic contact. Silicate minerals in the skarn include actinolite, chlorite, diopside, epidote, and garnet. The sulfides are mainly pyrite and pyrrhotite, and minor chalcopyrite. Chip samples (Kimball and others, 1978, table C37, location 27) contained as much as 770 ppm copper, 190 ppm zinc, and 1.5 ppm silver.
Geologic map unit (-136.99388681864, 58.9535934613347)
Mineral deposit model Skarn, massive sulfide -- similar to porphyry copper, skarn related (Cox and Singer, 1986; model 18a).
Mineral deposit model number 18a
Age of mineralization Tertiary.
Alteration of deposit Skarn developed in calc-magnesian rocks. Skarn minerals include garnet and epidote.

Production and reserves

Workings or exploration Surface occurrence only; samples of massive sulfide pods as much as 0.5 foot thick contained anomalous amounts of copper, zinc, and silver (Kimball and others, 1978, table C37, number 27).
Indication of production None

Additional comments

Extensive ice cover which could conceal skarn- or porphyry copper-type deposits. The occurrence is in Glacier Bay National Park and Preserve.