East Rainy

Prospect, Active

Commodities and mineralogy

Main commodities Cu; Ni; Pd; Pt
Other commodities Au; Co; Ir; Os; Rh; Ru
Ore minerals chalcopyrite; magnetite; pentlandite; pyrrhotite

Geographic location

Quadrangle map, 1:250,000-scale MH
Quadrangle map, 1:63,360-scale B-4
Latitude 63.3301
Longitude -145.8792
Nearby scientific data Find additional scientific data near this location
Location and accuracy The East Rainy prospect is at an elevation of 4,900 feet about 2.8 miles N10E from the junction of the North and West Forks of Rainy Creek. It is about 0.4 mile north of the center of section 29, T. 18 S., R. 10 E., of the Fairbanks Meridian. Figure 18 of Bittenbender and others (2007) is a geologic map of the prospect.

Geologic setting

Geologic description

The East Rainy prospect is near the north margin of the Late Triassic, Rainy Creek ultramafic-mafic complex that intrudes volcanic and sedimentary rocks of the Tetelna Volcanics and the Slana Spur Formations, both of Pennsylvanian and Permian age (Stout, 1976, Nokleberg and others, 1992 [MF]; 1992 [Open-File]; Bittenbender and others, 2007). The complex is up to 5,000 feet thick, dips shallowly north, and can be traced for more than 15 miles; it is mainly serpentinized dunite with subordinate peridotite, pyroxenite, and gabbro. The base of the complex is a layered gabbro as much as 1,500 feet thick.
The East Rainy prospect was discovered by American Copper and Nickel Company in 1995 or 1996 using data from airborne resistivity and magnetic geophysical surveys (Bittenbender and others, 2007). A joint venture with Fort Knox Gold Resources drilled a 246-foot hole in 1998. The property was acquired by Nevada Star Resources who drilled 7 holes totaling 980 feet in 2003 (Freeman, 2004).
The rocks at the East Rainy prospect are layered and gradually grade upward from porphyritic gabbro, through dunite, peridotite, feldspathic peridotite, and mafic-rich gabbro. There are at least two leucocratic gabbro dikes. (Figure 18 of Bittenbender and others (2007) is a geologic map of the geology). The mineralization is mostly in the feldspathic and mafic gabbro. The mineralization consists mainly of disseminated or net-textured pyrrhotite, pentlandite, and chalcopyrite.
Bittenbender and others (2007) collected 5 samples to characterize the mineralization. They averaged 4,085 parts per million (ppm) copper, 4,516 ppm nickel, 679 parts per billion (ppb) platinum, 774 ppb palladium, and 322 ppb gold. The highest platinum value was 950 ppb; the highest palladium value was 898 ppb.
Freeman (2004) reported that two holes in the 2003 Nevada Star drilling were in bad ground and the others did not intersect mineralization. The only notable mineralization were two, 5-foot intercepts in one hole. One intercept in feldspathic peridotite contained 1,366 ppm nickel, 833 ppm copper, 150 ppb platinum, and 148 ppb palladium. The other in leucogabbro contained 2,488 ppm nickel, 1,443 ppm copper, 205 ppb platinum, and 215 ppb palladium. The drilling indicated that the the mineralization is cut off at shallow depth by a younger intrusive body.
In 2011, Pure Nickel Inc., drilled two drill holes at East Rainy, totaling 488 meters. Platinum Group Element (PGE) values of up to 650 ppb over 2.52 meters of drill core were reported. Pure Nickel also completed a mapping and sampling program in 2011. Highlights of metal concentrations from grab sampling at East Rainy are 2.0 percent nickel, 1.3 percent copper, and 7.9 grams of PGE + gold + silver per tonne (Pure Nickel, 2011).
Geologic map unit (-145.881458449287, 63.3296842339499)
Mineral deposit model Nickel-copper-PGE mineralization in a differentiated mafic-ultramafic complex.
Age of mineralization Genetically related to the emplacement of a Late Triassic mafic-ultramafic complex (Bittenbender and others, 2007).
Alteration of deposit The gabbroic rocks are moderately serpentinized (Bittenbender and others, 2007).

Production and reserves

Workings or exploration
The East Rainy prospect was discovered by American Copper and Nickel Company in 1995 or 1996 using data from airborne resistivity and magnetic geophysical surveys (Bittenbender and others, 2007). A joint venture with Fort Knox Gold Resources drilled a 246-foot hole in 1998. The property was acquired by Nevada Star Resources who drilled 7 holes totaling 980 feet in 2003 (Freeman, 2004). The prospect was examined and sampled by the Bureau of Land Management in the early 2000s.
In 2011, Pure Nickel Inc., drilled two drill holes at East Rainy, totaling 488 meters. Platinum Group Element (PGE) values of up to 650 parts per billion over 2.52 meters of drill core were reported. Pure Nickel also completed a mapping and sampling program in 2011. Highlights of metal concentrations from grab sampling at East Rainy are 2.0 percent nickel, 1.3 percent copper, and 7.9 grams of PGE + gold + silver per tonne (Pure Nickel, 2011).
Indication of production None
Reserve estimates None.
Production notes None.

References

References

Bittenbender, P.E., Bean, K.W., Kurtak, J.M., and Deininger, James Jr., 2007, Mineral assessment of the Delta River Mining District area, east-central, Alaska: U.S. Bureau of Land Management, Alaska Technical Report 57, 675 p.
Freeman, C.J., 2004, Executive summary report for the MAN project, Delta River Mining District, Alaska: Unpublished report prepared by Avalon Development Corporation, Geology Report MN04EXE1, 40 p.
Pure Nickel Inc., 2011, Pure Nickel MAN Alaska Exploration Update: http://www.purenickel.com/s/NewsReleases.asp?ReportID=497855 (News release on December 21, 2011, as of July 9, 2014).
Reporters W.T. Ellis (Alaska Earth Sciences), C.C. Hawley (Hawley Resource Group), and W.J. Nokleberg (USGS); D.J. Grybeck (Contractor, USGS); V.C. Zinno (Alaska Earth Sciences, Inc.)
Last report date 12/11/2014