Assessment of the Platinum-Group Element Resources in Mafic-Ultramafic Igneous Intrusions of the Midcontinent Rift System, Lake Superior Region

Mineral Resources Program

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.

Assessing undiscovered contact- and reef-type PGE (+Cu-Ni) deposits is a challenging undertaking requiring further research and testing. Although mineral deposit models exist, they have yet to be applied directly to assess for undiscovered resources in the United States. The intrusions of the Duluth Complex and other smaller intrusive complexes of the Midcontinent Rift in the Lake Superior region have a high potential to contain undiscovered Cu-Ni-PGE sulfide deposits and provide an opportunity to further develop/refine, test and apply our mineral deposit models. In addition, more fully evaluating the possible mineral endowment of the Midcontinent Rift intrusive complexes will aid significantly in establishing the PGE resource base of the United States.

This project will focus on...

preparing and publishing deposits models for reef-type and contact-type PGE deposits
preparing the economic filter that will be used with the assessment
acquiring and compiling publicly available data for the Duluth Complex and related mafic and ultramafic intrusions
contacting potential cooperators and adding any information they can provide to the compilation;
evaluating and selecting the software to use for 3-D visualization and geostatistical resource estimation. Map data will be compiled into a GIS (ESRI); the format of the drill hole database will be compatible with the requirements for the modeling software. For the modeling software, we will start by considering products such as Geostatistical- and 3-D-analyst- extensions in ArcGIS; Geosoft’s Target for ArcGIS; the SGeMS geostatistical package; and Earthvision.

The objective of this project is to publish an assessment of the Duluth Complex and related mafic-ultramafic intrusions in the 1.1 Ga Midcontinent Rift System in the Lake Superior region that will (1) highlight the mineral resource potential for this region and its importance to the Nation, and (2) identify areas and topics for future research initiatives that will serve the national interest. This project will be conducted in coordination with the Minnesota Geological Survey, the Minnesota Department of Natural Resources, the Natural Resources Research Institute, academia, and industry.

Project Contacts

Project Leader: Michael Zientek
Phone: 509-368-3105
Email: mzientek@usgs.gov
Geology, Minerals, Energy, and Geophysics Science Center

Associate Project Leader: Klaus Schultz
Phone: 703-648-6320
Email: kschulz@usgs.gov
Eastern Mineral and Environmental Resources Science Center

Mineral Resources Program Science Priority

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