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Rock Glacier

Occurrence, Inactive

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Commodities and mineralogy

Main commodities Cu
Other commodities Fe
Ore minerals malachite; pyrite; pyrrhotite
Gangue minerals carbonate; chlorite; epidote; quartz

Geographic location

Quadrangle map, 1:250,000-scale MG
Quadrangle map, 1:63,360-scale B-3
Latitude 62.354
Longitude -154.128
Nearby scientific data Find additional scientific data near this location
Location and accuracy The Rock Glacier occurrence is located in the headwall of an unnamed stream valley above an active rock glacier at an elevation of approximately 4,600 feet (1,402 m) in the SE1/4 sec. 8, T. 26 N., R. 26 W., of the Seward Meridian. The location is based on descriptions provided in Gilbert and others (1990). The reporter visited the site in 1984.

Geologic setting

Geologic description

Pyrite-rich gossan zones were noted by Gilbert and others (1990) in a composite dike swarm, andesitic flows, and lapilli tuffs within the Windy Fork volcanic complex (Bundtzen, Harris, and Gilbert, 1997). Pyrite and pyrrhotite, which locally comprise up to 50 percent of the gossan-rich zones, are accompanied by carbonates, chlorite, epidote, and quartz. Individual gossan bodies are irregular in dimension, and reach maximum lengths of 40 meters. Gangue mineralogy suggests formation by introduction of metasomatic fluids; i.e., skarns. Malachite staining was observed in some of the fractured hornfels in the gossan zones. No assay data is available for the Rock Glacier occurrence.
Geologic map unit (-154.130222546653, 62.3533806459992)
Mineral deposit model Copper skarn? (Cox and Singer, 1986; model 18b?).
Mineral deposit model number 18b?
Age of mineralization K-Ar age of 37.9 Ma published by Gilbert and others (1990).
Alteration of deposit Propylitization.

Production and reserves

Workings or exploration No assay data is available for the Rock Glacier occurrence.
Indication of production None
Reserve estimates None.

Additional comments

Similar to Rat Fork-Headwall and Rat Fork-Base prospects (MG058; MG059) in McGrath B-2 quadrangle.

References

MRDS Number 10307849

References

Bundtzen, T.K., Harris, E.E., and Gilbert, W.G., 1997, Geologic Map of the eastern McGrath quadrangle, Alaska: Alaska Division of Geological and Geophysical Surveys Report of Investigations 97-14, 34 p., 1 sheet, scale 1:125,000.
Gilbert, W.G., Solie, D.N., Kline, J.T., and Dickey, D.B., 1990, Geologic map of the McGrath B-3 quadrangle, Alaska: Alaska Division of Geological and Geophysical Surveys Professional Report 102, 2 sheets, scale 1:63,360.
Reporters T.K. Bundtzen (Pacific Rim Geological Consulting)
Last report date 12/4/1998