Graben

Occurrence, Inactive

Commodities and mineralogy

Main commodities Co; Cu; Ni
Other commodities Au; Hg; Ti

Geographic location

Quadrangle map, 1:250,000-scale TK
Quadrangle map, 1:63,360-scale D-3
Latitude 62.8304
Longitude -148.2411
Nearby scientific data Find additional scientific data near this location
Location and accuracy The Graben occurrence is on the north bank of the Susitna River, about 0.2 mile east of the mouth of Watana Creek. The location is accurate.

Geologic setting

Geologic description

This occurrence is in basalt of the Triassic, Nikolai Greenstone. Fractures in the amygdaloidal basalt are marked by orange-red to orange-brown coatings, locally accompanied by yellow-green coatings and white and yellow efflorescence (J. Schmidt, written communication, 2001). Rock samples collected by the U.S. Geological Survey contain up to 2,120 parts per million copper, 110 parts per million nickel, 226 parts per million cobalt, 0.2 part per million gold, and 1.05 percent titanium; one sample contains 1.56 parts per million mercury (J. Schmidt, written communication, 2001). (The 0.2-part-per- million gold value is an ICP analysis done by XRAL Laboratories; a fire assay shows less than 0.005 ppm gold. The cause of the discrepancy is not known.)
Geologic map unit (-148.243342492154, 62.829935172324)
Mineral deposit model Basaltic copper? (Cox and Singer, 1986; model 23?)
Mineral deposit model number 23?
Age of mineralization Occurs in Triassic basalt.
Alteration of deposit Iron-oxide(?) and undetermined secondary minerals.

Production and reserves

Workings or exploration Only surface sampling by U.S. Geological Survey (J. Schmidt, written communication, 2001).
Indication of production None

References