Unnamed (east of West Fork Maclaren River)

Occurrence, Inactive

Commodities and mineralogy

Main commodities Cu
Ore minerals azurite; chalcopyrite; magnetite; malachite
Gangue minerals epidote; quartz

Geographic location

Quadrangle map, 1:250,000-scale MH
Quadrangle map, 1:63,360-scale A-6
Latitude 63.2242
Longitude -146.7128
Nearby scientific data Find additional scientific data near this location
Location and accuracy This occurrence is at an elevation of about 4,000 feet in a west-flowing tributary to the West Fork Maclaren River, in the NW1/4SW1/4 section 36, T. 19 S., R. 5 E., Fairbanks Meridian. The site corresponds to locality 11 of Kaufman (1964), locality 18 in figure 4 of Cobb (1979 [OFR 79-238]), and locality 25 in table 2 of Nokleberg and others (1991).

Geologic setting

Geologic description

The rock near this prospect is propylitized metabasalt of the Nikolai Greenstone of Late Triassic age (Nokleberg and others, 1991). Some probably Cretaceous granitic material is exposed at the site.
Copper minerals are found in place and in float at the site. Kaufman (1964, p. 7, occurrence 11) speculated that the source of float minerals is probably a considerable distance upstream.
Chalcopyrite occurs in place in stringers in greenstone and intrusive material at the site of the occurrence. Float found in the creek bed at the 4,000-foot elevation consists of banded chalcopyrite-magnetite skarn and banded azurite-malachite.
Geologic map unit (-146.715065497068, 63.2237633344364)
Mineral deposit model Basaltic Cu? (Cox and Singer, 1986; model 23?); Cu skarn in float material (Cox and Singer, 1986, model 18b).
Mineral deposit model number 23?, 18b
Age of mineralization Uncertain. The banded chalcopyrite-magnetite skarn float is almost certainly derived from the Cretaceous Zackly skarn deposit (MH067), discovered in 1979.

Production and reserves

Workings or exploration Bedrock and float mineral specimens were found during geologic mapping (Kaufman, 1964). The source of float almost certainly is the Zackly skarn deposit (MH067).
Indication of production None

Additional comments

Kaufman (1964) noted the mineralized skarn float may have traveled a considerable distance downstream, a conclusion borne out with the discovery of the Zackly prospect (MH067) in 1979 by Resource Associates of Alaska.