Jim Creek

Occurrence, Inactive

Commodities and mineralogy

Main commodities Ag; Cu; Zn
Other commodities Au
Ore minerals arsenopyrite; chalcopyrite; pyrrhotite; sphalerite
Gangue minerals calcite; quartz

Geographic location

Quadrangle map, 1:250,000-scale AN
Quadrangle map, 1:63,360-scale C-5
Latitude 61.57
Longitude -148.8
Nearby scientific data Find additional scientific data near this location
Location and accuracy Prospect is located 1.5 mile downstream from the headwaters of Jim Creek at a point roughly 1,500 ft north of the creek. Location accurate within 1 mile. Locality 45 of Cobb (1972), and locality 34 of MacKevett and Holloway (1977).

Geologic setting

Geologic description

Heavily silicified greenstone is cut by a vein that averages 1 ft thick. The vein strikes N 80 W, and is approximately vertical. The vein is composed of 40 percent chalcopyrite, 40 percent pyrrhotite, 15 percent sphalerite, and 5 percent calcite; and assays show 15.08 percent Cu, 2.95 percent Zn, 1.75 oz/ton Ag, and trace Au. The greenstone on both sides of the sulfide vein has been replaced by quartz and calcite, and cut by very thin arsenopyrite veins. Assays of replaced wall rock show 0.41 oz/ton Ag and 0.04 percent Cu. An alaskite dike runs approximately 500 ft upslope the sulfide vein prospect and slate outcrops 50 ft downhill from prospect (Landes, 1927).
Geologic map unit (-148.802216664197, 61.5694688430233)
Mineral deposit model Polymetallic vein (Cox and Singer, 1986; model 22c)
Mineral deposit model number 22c
Age of mineralization Mesozoic or younger.
Alteration of deposit Calcite and quartz replacement of greenstone at periphery of sulfide vein.

Production and reserves

Workings or exploration The vein is composed of 40 percent chalcopyrite, 40 percent pyrrhotite, 15 percent sphalerite, and 5 percent calcite; and assays show 15.08 percent Cu, 2.95 percent Zn, 1.75 oz/ton Ag, and trace amounts of Au. Assays of replaced wall rock show 0.41 oz/ton Ag and 0.04 percent Cu (Landes, 1927).
Indication of production None

References

MRDS Number A011646

References

Reporters D.P. Bickerstaff (USGS contractor); S.W. Huss (USGS)
Last report date 7/30/1998