Gravel Pit Occurrence, Chistochina Mining District, Valdez-Cordova Census Area, Alaska, USAi

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

Location: This occurrence is in a gravel pit at an elevation of 3,650 feet on the north side of the Denali Highway, 1.9 miles southeast of Fourteenmile Lake. It is in the NW1/4NW1/4 section 36, T. 21 S., R. 10 E., Fairbanks Meridian.
Geology: Peridotite in a borrow pit on the side of the Denali Highway contains as much as 1 percent disseminated pyrrhotite and traces of platinum group elements (L.D. Hulbert, oral communication, 2001). The peridotite probably is part of the Tangle ultramafic-mafic complex of Late Triassic age. Two grab samples collected by MAN Resources respectively contained 0.11 percent nickel, 0.01 percent copper, 67 ppb palladium, and 146 ppb platinum and 0.27 percent nickel, 0.09 percent copper, 58 parts per billion (ppb) palladium, 51 ppb platinum, and 51 ppb gold (L.D. Hulbert, 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 is believed to be a lopolithic feeder of the Nikolai basalt flows of the Wrangellia Terrane (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: Two grab samples collected by MAN Resources respectively contained 0.11 percent nickel, 0.01 percent copper, 67 parts per billion (ppb) palladium, and 146 ppb platinum and 0.27 percent nickel, 0.09 percent copper, 58 ppb palladium, 51 ppb platinum, and 51 ppb gold. The occurrence is on active claims of MAN Resources.
Age: Late Triassic.
Alteration: The peridotite is locally serpentinized.

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

Other Databases

Link to USGS - Alaska:	MH193

Other Regions, Features and Areas containing this locality