Dunite Hill

Occurrence, Active

Commodities and mineralogy

Main commodities Cu; Ni; Pd; Pt
Ore minerals pyrrhotite
Gangue minerals olivine; serpentine

Geographic location

Quadrangle map, 1:250,000-scale MH
Quadrangle map, 1:63,360-scale A-4
Latitude 63.0685
Longitude -145.7458
Nearby scientific data Find additional scientific data near this location
Location and accuracy This occurrence is at an elevation of 4,000 feet on the east side of peak 4220 about 1.6 miles east-southeast of Fourteenmile Lake. It is in the SE1/4NW1/4 section 25, T. 21 S., R. 10 E., Fairbanks Meridian. Peak 4220 is informally called Dunite Hill.

Geologic setting

Geologic description

Dunite Hill (as it is informally called) is underlain by partly serpentinized massive gray dunite that is part of the Tangle mafic-ultramafic intrusive complex (W.T. Ellis, oral communication, 2001). The complex may be a lopolithic feeder of the Nikolai basalt flows of the Wrangellia Terrane. A grab sample reported by MAN Resources contained 0.16 percent nickel, 0.22 percent copper, 101 parts per billion (ppb) palladium, and 53 ppb platinum.
The Tangle complex is a Late Triassic 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 the 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 (-145.748031719156, 63.0680775702883)
Mineral deposit model Ni-Cu-PGE in differentiated mafic-ultramafic sill.
Age of mineralization Late Triassic.
Alteration of deposit The dunite is locally serpentinized.

Production and reserves

Workings or exploration
A grab sample reported by MAN Resources contained 0.16 percent nickel, 0.22 percent copper, 101 parts per billion (ppb) palladium, and 53 ppb platinum.
The occurrence is on active claims of MAN Resources.
Indication of production None

References

Reporters W.T. Ellis (Alaska Earth Science), C.C. Hawley (Hawley Resource Group), and W.J. Nokleberg (USGS)
Last report date 6/17/2002