Unnamed (on east side of West Fork Maclaren River)

Occurrence, Inactive

Commodities and mineralogy

Main commodities Cu
Other commodities Ag
Ore minerals chalcocite; malachite
Gangue minerals epidote; quartz

Geographic location

Quadrangle map, 1:250,000-scale MH
Quadrangle map, 1:63,360-scale B-6
Latitude 63.2504
Longitude -146.7302
Nearby scientific data Find additional scientific data near this location
Location and accuracy This occurrence is at an elevation of about 4,000 feet, about 1,300 feet south of the center of section 23, T. 19 S., R. 5 E., Fairbanks Meridian. The site corresponds to locality 16 in figure 4 of Cobb (1979 [OFR 79-238]). The location is probably accurate within one-quarter mile.

Geologic setting

Geologic description

Rocks near the site are andesitic to basaltic volcanic rocks of the Nikolai Greenstone of Late Triassic age, a characteristic unit of the Wrangellia terrane (Nokleberg and others, 1981). Chalcocite or its oxidation product malachite occur in quartz-epidote veinlets and vesicles partly filled with quartz-epidote. The copper minerals also occur on fracture or joint surfaces of the host andesite and basalt. Copper is typically accompanied by some silver.
Geologic map unit (-146.732467715688, 63.2499634292458)
Mineral deposit model Weak copper mineralization of cupriferous volcanic rocks. Basaltic Cu (Cox and Singer, 1986; model 23).
Mineral deposit model number 23
Age of mineralization Post-Late Triassic. It also postdates a folding event that occurred in pre-Late Jurassic time (Stout, 1976, p. 30-31). It probably occurred in the Cretaceous during regional metamorphism and granitic plutonism (Nokleberg and others, 1986) or in the early Tertiary at about the time of emplacement of dacite porphyry dikes (Stout, 1976, p. 23, 31).

Production and reserves

Workings or exploration Natural exposures; copper minerals were found during geochemical investigations (Smith and others, 1973, 1975).
Indication of production None



Reporters W.T. Ellis (Alaska Earth Science), C.C. Hawley (Hawley Resource Group), and W.J. Nokleberg (USGS)
Last report date 7/30/2001