Hail Creek Prospect, Delta River Mining District, Southeast Fairbanks Census Area, Alaska, USAi

Regional Level Types
Hail Creek Prospect	Prospect
Delta River Mining District	Mining District
Southeast Fairbanks Census Area	Census Area
Alaska	State
USA	Country

Location: This prospect is at an elevation of 4,200 feet in a west-flowing tributary, informally called Hail Creek, to upper North Fork Rainy Creek. It is in the SW1/4NE1/4 section 25, T. 18 S., R. 9 E., Fairbanks Meridian.
Geology: At Hail Creek, an elongate east-northeast-trending magnetic high coincides with nine airborne electromagnetic anomalies. The eastern string of four anomalies marks an iron oxide-stained, serpentinized and silicified zone in a dunite that contains local copper-stained limonitic fractures (W.T. Ellis, oral communication, 2001). To the west, downhill along this trend, the dunite is intruded by a variably serpentinized taxitic olivine gabbro. A copper-stained and sulfide-bearing serpentinized zone is present in one location along the poorly exposed gabbro contact. The sulfide minerals noted include trace to 2 percent disseminated chalcopyrite, pentlandite, pyrrhotite, and magnetite. Strong large-loop electromagnetic geophysical conductors were detected on three surveyed lines. The surrounding rocks are part of the Rainy ultramafic-mafic complex of Late Triassic age (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. The complex intrudes the Slana Spur Formation of Pennsylvanian age (Nokleberg and others, 1991). 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 in this area has been by American Copper and Nickel Company (ACNC) working with Fort Knox Gold Resources, Inc. Exploration from 1995 through 1998 included rock sampling, airborne and ground geophysical surveys, and completion of one diamond drill hole (W.T. Ellis, oral communication, 2001). The general area was staked by ACNC in 1995, but the Hail Creek occurrence was not discovered until 1998 when the exploration followed up a reconnaissance large-loop geophysical survey and an anomalous float sample found in 1995. The float sample contained 0.39 percent nickel, 0.24 percent copper, 0.09 percent cobalt, 216 parts per billion (ppb) palladium, and 295 ppb platinum. UTEM geophysical conductors coincide with the east-northeast-trending Hail Creek zone. A rock grab sample from the occurrence assayed 0.25 percent nickel, 0.48 percent copper, 68 ppb palladium, and 95 ppb platinum. One 250-foot drill hole completed in 1998 failed to penetrate significant mineralization at one of the stronger UTEM anomalies. The occurrence is on active claims of Fort Knox Gold Resources.
Age: Late Triassic.
Alteration: Local silicification and serpentinization of dunite and gabbro.

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:	MH152

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