Unnamed (west of lower Eureka Glacier)

Occurrence, Probably inactive

Commodities and mineralogy

Main commodities Cr; Ni
Other commodities Pd; Pt
Gangue minerals quartz

Geographic location

Quadrangle map, 1:250,000-scale MH
Quadrangle map, 1:63,360-scale B-5
Latitude 63.3048
Longitude -146.4349
Nearby scientific data Find additional scientific data near this location
Location and accuracy This occurrence is at an elevation of about 5,000 feet in a south-flowing tributary of the East Fork Maclaren River about 2 miles west of the toe of Eureka Glacier. The occurrence is at the southeast corner of section 32 T. 18 S. R. 7 E. Fairbanks Meridian, and corresponds to locality A8 of Kurtak and others (1992).

Geologic setting

Geologic description

This occurrence is approximately on a major east-west fault that separates granitic rocks of Jurassic or Cretaceous age (on the north) from Paleozoic metasedimentary rocks or Nikolai Greenstone of Late Triassic age (Nokleberg and others, 1991). A steep northwest cross fault was mapped at about this locality by Rose (1966 [ADMM GR 20, figure 3). Rose also mapped lenticular masses of dunite and gabbro farther north, within dioritic rocks of the granitic complex.
The U.S. Bureau of Mines traversed along the gulch that exposes the occurrence between about 4,500 and 5,500 feet elevation and found inclusions or dikes of serpentinized dunite in a granitic host that they called quartz monzonite (Kurtak and others, 1992, locality A 8). The serpentinized dunite contained 0.21 to 0.24 percent nickel and 0.13 to 0.15 percent chromium. The mineral host(s) of the nickel and chromium is unknown. Silicified quartz monzonite in a fault zone contained 12 parts per billion palladium and 5 parts per million platinum. Platinum and palladium were also detected in creek gravel and dunite float (Kurtak and others, 1992, table A8).
Geologic map unit (-146.437165989662, 63.3043730559138)
Mineral deposit model Ultramafic related.
Age of mineralization Mesozoic (?), possibly the age of the ultramafic host rocks.
Alteration of deposit Silicification of quartz monzonite; serpentinization of dunite (Kurtak and others, 1992).

Production and reserves

Workings or exploration
U.S. Bureau of Mines geologists traversed the deep gulch that crosses the intrusive rock-metasedimentary rock contact (Kurtak and others, 1992). Their samples of serpentinized dunite contained as much as 0.24 percent nickel and 0.15 percent chromium; an altered quartz monzonite contained 12 parts per billion palladium.
The occurrence is on active MAN Resources claims (W.T. Ellis, written communication, 2001).
Indication of production None

References