Unnamed (west side of West Fork of the Maclaren River)

Occurrence, Inactive

Commodities and mineralogy

Main commodities Cu; Mo
Other commodities Ag
Ore minerals chalcopyrite; pyrite; malachite; molybdenite
Gangue minerals iron-bearing carbonate mineral; quartz; white mica

Geographic location

Quadrangle map, 1:250,000-scale MH
Quadrangle map, 1:63,360-scale B-6
Latitude 63.2536
Longitude -146.827
Nearby scientific data Find additional scientific data near this location
Location and accuracy The occurrence is at an elevation of 4,800 feet on an unnamed east-flowing tributary to the west side of the West Fork Maclaren River. The unnamed creek is east of the divide at the head of Clearwater Creek. The occurrence is near the center of section 20, T. 19 S., R. 5 E., Fairbanks Meridian. The site corresponds to locality 12 of Kaufman (1964), locality 13 in figure 4 of Cobb (1979 [OFR 79-238), and locality 4 of MacKevett and Holloway (1977). The location is probably accurate within one-third mile.

Geologic setting

Geologic description

This occurrence consists of sulfide-bearing blocks of talus and of mineralized bedrock. Rocks near the occurrence are folded argillites of probable Cretaceous age (Nokleberg and others, 1991). The argillite is cut by dikes and, possibly, by a small stock of granite. The area is iron stained due to the oxidation of iron-bearing carbonate and of pyrite disseminated in the argillite; some of the talus blocks are also coated with malachite. Kaufman (1964, p. 7) inferred that the pyritic argillite was peripheral to fine- to medium-grained granite in a dike swarm or a small stock.
Talus fragments of granitic material contain abundant disseminated pyrite and sparsely disseminated chalcopyrite and molybdenite. Molybdenite also occurs in quartz-vein-rich talus. Grab samples of mineralized talus contained 0.15 to 0.25 percent molybdenum (Kaufman, 1964, p. 7).
A nearby area was investigated by the U.S. Bureau of Mines in a search for the source of the mineralized granitic material (Kurtak and others, 1992). One quartz-bearing sample contained 29 parts per million molybdenum; a quartz-carbonate vein contained 395 parts per billion gold, and another vein contained 0.98 ounce of silver per ton. The area is very rugged, and the main source of mineralized material may be buried by talus.
Geologic map unit (-146.829269338663, 63.2531608650533)
Mineral deposit model Porphyry Cu-Mo (Cox and Singer, 1986; model 21a).
Mineral deposit model number 21a
Age of mineralization Cretaceous or younger. Mineralized dikes cut argillite of probable Cretaceous age.

Production and reserves

Workings or exploration The area has been mapped and sampled in reconnaissance (Kurtak and others, 1992); claims have been located in the area, but little physical prospecting has been done.
Indication of production None