The Duluth Complex
The Duluth Complex is a well known geological formation with large quantities of copper, nickel, cobalt, platinum, palladium and gold. The Duluth Complex lies just south of the eastern end of the Mesabi Iron Range in northeastern Minnesota.
The Duluth Complex hosts the NorthMet mineralization. The Complex extends in an arc-like belt from Duluth to the northeastern tip of Minnesota. Emplacement of the intrusion appears to have been along a system of northeast-trending normal faults that form half-grabens stepping down to the southeast. The magma was intruded as sheet-like bodies along the contact between the Early Proterozoic sedimentary rocks of the Animikie Group and the mafic lava flows of the North Shore Volcanic Group.
The Minnesota Department of Natural Resources estimates the Duluth Complex contains about 4.4 billion tons of mineral resources grading at 0.66% copper and 0.20% nickel.
The 30-mile long stretch of the Duluth Complex, along the Mesabi Range, hosts at least 10 known significant deposits. PolyMet’s NorthMet deposit is located on its western end, where deposits are amenable to open pit mining.