Wetleggs Project

At the southern end of the range closer to Babbit a deposit of other ores have been discovered. The rocks, composed mostly of gabbro, are part of the Duluth Complex. They contain ores of copper, nickel, platinum and silver. Even though the amounts are small the area is being studied by several mining companies (International Nickel Co., Bear Creek Mining, and Exxon Minerals) because the infrastructure and labor force are already in place for mining. These photos are from similar kinds of rocks at a railroad cut off Dunka Road. These rocks are ophitic augite troctolite (a form of gabbro), olivine gabbro, and augite rich pegmatite. They have a rusty iron staining (notice in the top left photo) that is characteristic of copper and nickel deposits. It is due to the weathering of the sulfides in the rock. The sulfides that are present include pyrrhotite (iron sulfide), pentlandite (nickel sulfide) and chalcopyrite (copper sulfide). One of the gabbro exposures exhibits variably sized anorthosite inclusions that range from 2 inches across to 10x15 foot blocks. The anorthosite crystallized earlier from a plagioclase rich magma only to be broken up, surrounded and carried upward by later gabbroic magmas. In the lower right photo some larger crystal faces of feldspar are visible. The large crystals of gabbro have the same mineral composition of the very small grained rock basalt.

Gabbro
Gabbro
Gabbro
Gabbro
Two other major base metal deposits occur further to the northeast in the Duluth Complex. The Dunka road deposit, initially drilled by United States Steel Corp. was recently being evaluated as a possible mine by PolyMet Mining Corp. of Golden Colorado. Poly Met estimates that the deposit contains about 808 million tons of material of 0.43% copper and 0.11% nickel with localized concentrations of palladium.

The Babbit deposit which was drilled and defined by Bear Creek Mining (1959-1971) and by AMAX (1974-1978). The deposit is currently controlled by Teck-Cominco Ltd, Vancouver, B. C., who estimates that the Babbitt deposit, renamed the Mesaba deposit contains 700 million tons of material that is about 0.46% copper and 0.12% nickel.
 

 
 
  All information on this page is from the 2003 MN DNR Minerals Workshop.
 

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