Unnamed (Walker Fork)

Occurrence, Inactive

Commodities and mineralogy

Main commodities Au
Gangue minerals ankerite; calcite; chlorite; clay; quartz

Geographic location

Quadrangle map, 1:250,000-scale EA
Quadrangle map, 1:63,360-scale A-2
Latitude 64.0871
Longitude -141.6797
Nearby scientific data Find additional scientific data near this location
Location and accuracy This occurrence is located at water level at the apex of a sharp bend of the Walker Fork of the Fortymile River in section 28, T. 27 N., R. 19 E., of the Copper River Meridian. The location is accurate.

Geologic setting

Geologic description

This occurrence is in a hornblende-biotite granodiorite of the Walker Fork pluton. Biotite from the pluton gives a 40Ar/39Ar plateau age of 99.0 +/- 0.5 Ma (Layer and others, 2002). The pluton is left-laterally offset about one-half mile by a northeast-trending high-angle fault (Werdon and others, 2001). A prominent circular magnetic low along the fault is present in airborne geophysical survey data (Alaska Division of Geological and Geophysical Surveys and others, 1999). The magnetic low corresponds to an area of extensive shearing. The granodiorite is partially altered to chlorite, clay, and calcite. Altered granodiorite that is cut by limonite and quartz veins with ankerite(?) and calcite contains as much as 55 ppb gold (Szumigala and others, 2000).
Geologic map unit (-141.68198111866, 64.0867756407392)
Mineral deposit model Shear zone-hosted lode gold.
Age of mineralization Associated with a fault that offsets the Walker Fork pluton of Cretaceous age.
Alteration of deposit The granodiorite is partially altered to chlorite, clay, and calcite.

Production and reserves

Indication of production None