Unnamed (on upper Powers Creek)

Occurrence, Probably inactive

Commodities and mineralogy

Main commodities Ag
Other commodities Mo; Zn
Ore minerals chalcopyrite; pyrite; pyrrhotite

Geographic location

Quadrangle map, 1:250,000-scale SD
Quadrangle map, 1:63,360-scale D-5
Latitude 57.77102
Longitude -133.48678
Nearby scientific data Find additional scientific data near this location
Location and accuracy This altered zone is at an elevation of about 800 feet, about 0.4 mile southwest of the terminus of the Sumdum Glacier. It is about 0.5 mile north-northeast of the center of section 30, T. 47 S., R. 74 E.

Geologic setting

Geologic description

This occurrence is an zone of rusty, siliceous, chlorite schist that is southwest of the toe of the Sumdum Glacier; Brew and Grybeck (1984) assign the schist a Cretaceous metamorphic age. Kimble and others (1984) systematically sampled the zone with a series of 11 samples that extended for 1,150 feet perpendicular to the layering of the metamorphic rocks. All 11 samples contained 0.5 to 1.0 part per million (ppm) silver; 3 contained 15-30 ppm molybdenum, and 2 contained 150-380 ppm zinc. Many of the rocks in the iron-stained zone have sparse disseminated sulfides. The sulfides are mainly pyrrhotite although trace chalcopyrite also occurs. The iron staining is probably due to the weathering of the pyrrhotite.
Geologic map unit (-133.488500794609, 57.770685770635)
Mineral deposit model Sparse pyrrhotite and rare chalcopyrite in gneiss.
Age of mineralization Occurs in schist of Cretaceous (metamorphic) age.
Alteration of deposit Iron-staining probably due to weathering of pyrrhotite.

Production and reserves

Workings or exploration None beyond sampling by government geologists.
Indication of production None

Additional comments

The occurrence is in the Tracy Arm-Fords Terror Wilderness Area which is closed to mineral exploration and mining.

References