Crash

Prospect, Active?

Commodities and mineralogy

Main commodities Au; Cu; Ni; Pd; Pt
Other commodities Cr
Ore minerals chalcopyrite; chromite; magnetite; pentlandite; pyrrhotite

Geographic location

Quadrangle map, 1:250,000-scale MH
Quadrangle map, 1:63,360-scale B-5
Latitude 63.316
Longitude -146.225
Nearby scientific data Find additional scientific data near this location
Location and accuracy The Crash prospect is at an elevation of about 5,120 feet, about 4.1 miles northwest of the junction of Broxson Gulch and Eureka Creek. It is about 0.4 mile east of peak 5540 and about 0.5 mile north of the center of section 33, T. 18 S., R. 8 E. The location is accurate.

Geologic setting

Geologic description

The Crash prospect is in an east-trending, northward-dipping sill of Late Triassic, ultramafic and mafic rocks that are part of the Eureka complex (Rose, 1966; Nokleberg and others, 1992 [MF]; Nokleberg and others, 1992 [Open-File]; Bittenbender and others, 2007). The prospect was found by industry in the 1990s (W.T. Ellis, unpublished data, 1996). At this prospect, the sill is about 100 feet thick; it dips north about 40 degrees; and consists of differentiated pyroxenite and gabbro. The footwall of the sill is siliceous volcanic rocks; the hanging wall is argillite, slate, and graywacke. A layer in the sill is altered with plagioclase going to saussurite and pyroxene going to actinolite; malachite and garnierite staining is prominent locally. The gabbro contains as much as 7 percent disseminated sulfides and magnetite. The sulfides are mainly pyrrhotite with small amounts of chalcopyrite and pentlandite. Samples assayed as much as 0.09 percent copper, 0.42 percent nickel, 630 parts per billion (ppb) palladium, and 475 ppb platinum (W.T. Ellis, unpublished data, 1996).
Bittenbender and others (2007) examined and sampled the prospect. Their best sample was from iron-stained peridotite that contained 1,315 parts per million (ppm) copper, 2,180 ppm nickel, 322 ppb platinum, 414 ppb palladium, and 85 ppb gold.
Geologic map unit (-146.227264671067, 63.315577548307)
Mineral deposit model Nickel-copper-PGE mineralization in a differentiated mafic-ultramafic sill.
Age of mineralization Genetically related to the emplacement of a Late Triassic mafic-ultramafic complex.
Alteration of deposit The ultramafic rocks units are moderately to strongly serpentinized.

Production and reserves

Workings or exploration Found and sampled by industry in the 1990s; examined and sampled by the Bureau of Land Management in the early 2000s.
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.
Reporters W.T. Ellis (Alaska Earth Sciences), C.C. Hawley (Hawley Resource Group), and W.J. Nokleberg (USGS); D.J. Grybeck (Contractor, USGS)
Last report date 5/13/2012