Unnamed (on tributary of Cheeneetnuk River)

Occurrence, Inactive

Commodities and mineralogy

Main commodities Cu
Other commodities Ag
Ore minerals pyrite

Geographic location

Quadrangle map, 1:250,000-scale MG
Quadrangle map, 1:63,360-scale A-5
Latitude 62.065
Longitude -155.207
Nearby scientific data Find additional scientific data near this location
Location and accuracy This unnamed occurrence is located on a north-south ridgeline overlooking an unnamed tributary of Cheeneetnuk River; it is at an elevation of 2,475 feet (754 m) in the SE1/4 sec. 19, T. 23 N., R. 32 W., of the Seward Meridian. The location corresponds to map number 138 in Gilbert (1981); his station no. 77WG203. The reporter visited the site in 1989.

Geologic setting

Geologic description

This unnamed occurrence is a sulfide gossan hosted in Upper Paleozoic argillite of the Mystic subterrane, adjacent to a Tertiary andesite dike (Gilbert, 1981; Wilson and others, 1998). The gossan trends northeast for 90 meters and may be related to the dike.
Pyrite impregnates ferricrete gossan in one sample; otherwise sulfide minerals have been completely oxidized. The argillite is locally thermally upgraded to hornfels; axinite and secondary biotite are observed in talus and rubble crop. A mid-Tertiary (39.8 Ma) granite pluton (Solie and others, 1991) is exposed in low angle contact with the Upper Paleozoic argillite and probably underlies the ridge where the mineralization occurs. Surface dimensions of the gossan are not available. One grab sample of gossan contained 350 ppm copper and 0.3 grams/tonne silver (Gilbert, 1981).
Geologic map unit (-155.209311418549, 62.0643434095592)
Mineral deposit model Polymetallic replacement? (Cox and Singer, 1986; model 19a?).
Mineral deposit model number 19a?
Age of mineralization Unknown; possibly related to 39.8 Ma granite body nearby (Gilbert, 1981; Solie and others, 1991).
Alteration of deposit Axinite, secondary biotite.

Production and reserves

Workings or exploration W.G. Gilbert found the occurrence during a geologic mapping program for the Alaska Division of Geological and Geophysical Surveys in 1977 (Gilbert, 1981). One grab sample of gossan contained 350 ppm copper and 0.3 grams/tonne silver (Gilbert, 1981).
Indication of production None
Reserve estimates None.

References