Dunite Hill Occurrence, Chistochina Mining District, Valdez-Cordova Census Area, Alaska, USAi

Regional Level Types
Dunite Hill Occurrence	Occurrence
Chistochina Mining District	Mining District
Valdez-Cordova Census Area	Census Area
Alaska	State
USA	Country

Location: 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.
Geology: 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.
Workings: 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.
Age: Late Triassic.
Alteration: The dunite is locally serpentinized.

Commodities (Major) - Cu, Ni, Pd, Pt
Development Status: None
Deposit Model: Ni-Cu-PGE in differentiated mafic-ultramafic sill.

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Link to USGS - Alaska:	MH194

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