Unnamed (south of Fielding lake)

Prospect, Active

Commodities and mineralogy

Main commodities Cu; Ni
Other commodities Pd; Pt
Ore minerals chalcopyrite; pyrrhotite; secondary copper mineral(s)
Gangue minerals quartz

Geographic location

Quadrangle map, 1:250,000-scale MH
Quadrangle map, 1:63,360-scale A-4
Latitude 63.1088
Longitude -145.7679
Nearby scientific data Find additional scientific data near this location
Location and accuracy This prospect is at an elevation of 3,300 feet on the east bank of the principal south tributary of Fielding Lake. It is in the NW1/4SE1/4 section 11, T. 21 S., R. 10 E., Fairbanks Meridian. It corresponds to locality 2 in Rose (1966 [ADMM GR 19]) and locality S86 in table 2 of Nokleberg and others (1991).

Geologic setting

Geologic description

This prospect is a copper-stained quartz vein about 1 foot thick that cuts fine-grained gabbro and minor pyroxenite. Nearby sparse float of gabbro contains disseminated chalcopyrite and pyrrhotite (Rose, 1966 [ADMM GR 19]). The vein strikes N10W and dips vertically.
The rocks are part of the Tangle ultramafic-mafic intrusive complex of Late Triassic age, which may be a lopolithic feeder of the Nikolai greenstone basalt flows of the Wrangellia Terrane (W.T. Ellis, oral communication, 2001). The Tangle complex is a north-dipping layered intrusion of dunite, peridotite, and gabbro that varies from less than 2,000 feet thick to more than 4,000 feet thick and extends for more than 12 miles in length (W.T. Ellis, oral communication, 2001). The complex intrudes the Tangle Formation of Permian age (Nokleberg and others, 1991). It may connect with the Fish Lake complex at depth below the Amphitheater synform. Magmatic mineralization is synchronous with emplacement of Tangle complex, which is part of a 120-mile-long belt of mafic-ultramafic and associated rocks in the east-central Alaska Range.
Geologic map unit (-145.770135940844, 63.1083786842745)
Mineral deposit model Ni-Cu-PGE in differentiated mafic-ultramafic sill; Basaltic Cu (Cox and Singer, 1986; model 23).
Mineral deposit model number 23
Age of mineralization Late Triassic and Cretaceous.

Production and reserves

Workings or exploration Several small pits have been dug on the quartz vein. The prospect is on active claims of MAN Resources.
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 6/17/2002