Unnamed (near Frying Pan Lake)

Prospect, Active

Commodities and mineralogy

Main commodities Fe
Other commodities Ti; V
Ore minerals ilmenite; magnetite

Geographic location

Quadrangle map, 1:250,000-scale IL
Quadrangle map, 1:63,360-scale D-7
Latitude 59.8588
Longitude -155.3286
Nearby scientific data Find additional scientific data near this location
Location and accuracy This prospect is centered on hill 1760 about 1.3 miles west of lake 943, locally called Frying Pan Lake. The site is near the center of section 5, T. 4 S., R. 35 W.

Geologic setting

Geologic description

This prospect is now mainly of local or historical interest as of 2011 in view of the great amount of exploration that has been done on the Pebble copper prospect (IL007) several miles to the northeast and the drilling on the '25 Zone' prospect (IL005) less than a half mile to the south.
This prospect is a body of breccia that consists of angular, magnetite-bearing pyroxenite fragments in a matrix of Tertiary or Cretaceous granodiorite (Reed and Detterman, 1965). Pyroxenite clasts constitute 50-90 percent of the breccia, and magnetite occurs in crystal aggregates as much as 1 inch across. Sixteen samples of breccia collected by Reed and Detterman (1965) contained 16 to 24 percent FeO, about 1.3 percent TiO2, 0.1 to 3.2 percent P2O5, and 0.1 to 0.15 percent V2O5. A magnetic concentrate of the material contained about 3.5 percent TiO2, reflecting the presence of ilmenite or titaniferous magnetite. Samples collected by Fischer (1975) contained about 0.02 percent V2O5, less than was reported by Reed and Detterman. Fischer's magnetite-rich concentrate from pyroxenite contained 40-60 percent iron, 3.1 percent TiO2, and 0.3-0.5 percent vanadium (Fischer, 1975). Bouley and others (1995) reported considerable iron in two samples of biotite pyroxenite they collected. Their sample 10 contained 18.78 percent iron (as Fe203). The rocks are also highly potassic and are similar to alkali ultramafic rocks in composite plutons elsewhere in the central Alaska Range (Foley and others, 1997).
Geologic map unit (-155.330791578034, 59.8581091231078)
Mineral deposit model Magnetite-bearing pyroxenite.
Age of mineralization The pyroxenite is probably Late Cretaceous but possibly predates the 90 Ma Pebble Copper deposit (IL007).
Alteration of deposit Not noted.

Production and reserves

Workings or exploration Exploration has been limited to geologic mapping and surface sampling at this locale but see ARDF IL005 for drilling at a copper prospect about a mile to the south.
Indication of production None
Reserve estimates Fischer (1975) estimated a resource of 7 billion tons of magnetite-bearing breccia that contained 7 million tons of vanadium.
Production notes None.

References

MRDS Number A013031

References

Bouley, B.A., St. George, P., and Wetherbee, P.K., 1995, Geology and discovery at Pebble Copper, a copper-gold porphyry system in southwest Alaska: Canadian Institute of Mining, Metallurgy, and Petroleum, Special Volume 46, p. 422-435.
Foley, J.Y., Light, T.D., Nelson, S.W., and Harris, R.A., 1997, Mineral occurrences associated with mafic-ultramafic and related alkaline complexes in Alaska, in Goldfarb, R.J., and Miller, L.D., eds., Mineral Deposits of Alaska: Economic Geology Monograph 9, p. 396-449.
Reporters C.C. Hawley, Hawley Resource Group, Anchorage, Alaska; D.J. Grybeck (Contractor, USGS)
Last report date 2/28/2011