Unnamed (west side of West Fork Maclaren River)

Occurrence, Inactive

Commodities and mineralogy

Main commodities Cu
Other commodities Ag
Ore minerals azurite; bornite; chalcocite; chrysocolla; malachite
Gangue minerals calcite; epidote; quartz

Geographic location

Quadrangle map, 1:250,000-scale MH
Quadrangle map, 1:63,360-scale A-6
Latitude 63.221
Longitude -146.7828
Nearby scientific data Find additional scientific data near this location
Location and accuracy This occurrence is on the west side of the West Fork Maclaren River valley at an elevation of approximately 3,600 feet, in the SE1/4SE1/4 section 33, T. 19 S., R. 5 E., Fairbanks Meridian. The occurrence corresponds to locality 10 of Kaufman (1964) and locality 10 in figure 4 of Cobb (1979 [OFR 79-238]). The location is probably accurate within one-third mile.

Geologic setting

Geologic description

The rock at this occurrence is Nikolai Greenstone of Late Triassic age (Nokleberg and others, 1982, 1991). Copper-bearing float occurs throughout a rock slide at the locality (Kaufman, 1964). The float consists of propylitized greenstone containing copper-rich pods and copper-bearing quartz-epidote-calcite veins that cut the greenstone. The copper minerals bornite and chalcocite and their oxidation products (azurite, chrysocolla, and malachite) were observed at the site. The rocks were not sampled; small amounts of silver typically occur with copper in the Basaltic Cu-type deposits of the area.
Geologic map unit (-146.785066607238, 63.2205614643664)
Mineral deposit model Basaltic Cu (Cox and Singer, 1986; model 23).
Mineral deposit model number 23
Age of mineralization Probably Cretaceous or early Tertiary (see MH060).
Alteration of deposit The mineralization is associated with quartz-epidote-calcite veins in propylitized basalt and andesite of the Nikolai Greenstone.

Production and reserves

Indication of production None

Additional comments

A traverse above the copper-bearing rock slide failed to reveal a source (Kaufman, 1964).

References

References

Reporters W.T. Ellis (Alaska Earth Science), C.C. Hawley (Hawley Resource Group), and W.J. Nokleberg (USGS)
Last report date 8/3/2001