East Peak Occurrence (Rainy), Delta River Mining District, Southeast Fairbanks Census Area, Alaska, USAi

Regional Level Types
East Peak Occurrence (Rainy)	Occurrence
Delta River Mining District	Mining District
Southeast Fairbanks Census Area	Census Area
Alaska	State
USA	Country

Location: The East Peak (Rainy) occurrence is a few hundred feet east of peak 6346 at an elevation of 6,000 feet. It is on the west side of North Fork Rainy Creek in SW1/4NE1/4 section 27, T. 18 S., R. 9 E., Fairbanks Meridian.
Geology: The East Peak (Rainy) occurrence is in an Upper Triassic ultramafic-mafic complex (the Rainy complex) that intrudes the Slana Spur Formation of Pennsylvanian age (Nokleberg and others, 1991). In this area a layered marginal gabbro sequence is as much as 1,500 feet thick. Prominent rock types are gabbronorites, clinopyroxene megacrystic melagabbro, and wherlite. The East Peak showing is in a melagabbro layer near the lower contact of the complex. Mineralization consists of 5 to 15 percent disseminated pyrrhotite and minor chalcopyrite and pentlandite in a coarse-grained olivine melagabbro with 15 to 25 percent feldspar. Two rock samples collected by American Copper and Nickel Company respectively contained 0.27 and 0.30 percent copper, 0.13 and 0.08 percent nickel, 84 and 510 parts per billion (ppb) palladium, and 110 and 55 ppb platinum. A sample collected by MAN Resources contained 46 ppb gold, 0.03 percent copper, 0.085 percent nickel, 510 ppb palladium, and 55 ppb platinum (W.T. Ellis, oral communication, 2001). The Rainy ultramafic-mafic complex is a steeply north-dipping tablular intrusion of dunite, peridotite, and gabbro that varies from less than 100 feet thick to more than 6,000 feet thick and extends for more than 12 miles in length (W.T. Ellis, oral communication, 2001). Discontinuous marginal gabbro extends along most of the southern (lower) contact and is less continuous along the northern (upper) contact. Magmatic mineralization is synchronous with emplacement of the Rainy complex, which is part of a 120-mile-long belt of mafic-ultramafic and associated rocks in the east-central Alaska Range.
Workings: Exploration on the Rainy property has been by American Copper and Nickel Company (ACNC) working with Fort Knox Gold Resources, Inc. Exploration from 1995 through 2001 included rock sampling, airborne and ground geophysical surveys, and completion of one diamond drill hole (W.T. Ellis, oral communication, 2001). The occurrence was discovered and staked by ACNC in 1995, but the claims were allowed to lapse in 1999. It is now (since 2000) on active claims of MAN Resources (MAN). Two rock samples collected by ACNC respectively contained 0.27 and 0.30 percent copper, 0.13 and 0.08 percent nickel, 84 and 510 parts per billion (ppb) palladium, and 110 and 55 ppb platinum. A sample collected by MAN contained 46 ppb gold, 0.03 percent copper, 0.085 percent nickel, 510 ppb palladium, and 55 ppb platinum (W.T. Ellis, oral communication, 2001).
Age: Late Triassic.
Alteration: The olivine melagabbro is variably serpentinized.

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

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Link to USGS - Alaska:	MH135

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