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Assessment of the platinum-group element resources in mafic-ultramafic igneous intrusions of the Midcontinent Rift System, Lake Superior region



Platinum-group elements (PGE) are critical commodities. They are essential for the US economy; however the US imports all the PGE that we need to use. There are no available substitutes.

A significant, though not yet fully defined, PGE resource is the sulfide mineralization in mafic intrusions related the 1.1 Ga Midcontinent Rift System in the Lake Superior region. The Midcontinent Rift extends more than 2000 km northward from Kansas beneath Lake Superior and then southeast through Michigan, but is only exposed around Lake Superior. Rift-related rocks include flood basalts, comagmatic mafic intrusions, and minor rhyolite overlain by sandstone. The Duluth Complex in northeastern Minnesota is one of the largest mafic intrusive complexes in the world, covering an area of about 5700 km2, and is second in size only to the Bushveld Complex.

Evaluating the possible mineral endowment of the Duluth Complex will aid significantly in establishing the PGE resource base of the United States.

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