Unnamed (southwest flank of Alpha Ridge)

Occurrence, Inactive

Commodities and mineralogy

Main commodities Cu
Other commodities Ag; Pb; Zn
Ore minerals chalcopyrite; galena; limonite; malachite
Gangue minerals quartz; sericite

Geographic location

Quadrangle map, 1:250,000-scale MM
Quadrangle map, 1:63,360-scale C-3
Latitude 63.5176
Longitude -151.0309
Nearby scientific data Find additional scientific data near this location
Location and accuracy This occurrence represents an area of mineralization on the southeast flank of Alpha Ridge. The location is the approximate midpoint of the area, which trends east-northeast for about 2000 feet and is up to 500 feet wide. The location is at the center of the north half of the section line between sections 21 and 22, T. 16 S., R. 18 W., Fairbanks Meridian. The location is accurate.

Geologic setting

Geologic description

This occurrence consists of disseminated chalcopyrite, pyrite, and possibly galena in a felsic unit of the Precambrian Birch Creek Schist (Hawley and Associates, 1978; Bundtzen, 1981). The schist is locally coated with malachite. Anomalous metal values in soil samples indicate that the outcrop area of the occurrence is at least 2000 feet long and about 500 feet wide. The occurrence is about on strike with the Alpha vein (MM021) but probably not related to it.
The occurrence was mapped and sampled by Hawley and Associates (1978), who collected eight samples (table 4.1-1(A), nos. 40-46, including subsamples) of the schist and of soil derived from it. Rock sample 41 contained 345 ppm copper, 1650 ppm lead, 635 ppm zinc and 11 ppm silver; rock sample 43B contained 1200 ppm copper. Soils contained 180- 545 ppm copper, and all but one contained detectable silver; the maximum silver value in soil was 3.8 ppm. The deposit probably formed by remobilization of primary metalliferous minerals in the felsic hostrock.
Geologic map unit (-151.033185744464, 63.5170912703427)
Mineral deposit model Probable remobilization of distal volcanogenic base metals in felsic hostrocks.
Age of mineralization Probably Precambrian, the age of the felsic protolith of the Birch Creek Schist. Remobilization of primary metals in the schist probably occurred in Eocene time, during the main stage of Kantishna district mineralization (see record MM091).
Alteration of deposit Local oxidation of copper mineral(s).

Production and reserves

Workings or exploration The occurrence has been mapped in reconnaissance; there are no known workings.
Indication of production None

Additional comments

The occurrence is in Denali National Park and Preserve. It is a type of mineral deposit that probably did not attract the attention of early prospectors.

References

References

Bundtzen, T.K., 1981, Geology and mineral deposits of the Kantishna Hills, Mt. McKinley quadrangle, Alaska: M. S. Thesis, University of Alaska, College, Alaska, 238 p.
Reporters C.C. Hawley
Last report date 12/27/2000