GEO-CM: Biogeochemical Processes Affecting Critical Mineral Hosts in Mine Tailings and Weathered Ore Zones

Washington University, Saint Louis MO

Investigators

Abstract

New domestic resources of critical minerals are needed to support a sustainable economy. Rare earth elements are necessary for magnets in electric motors and wind turbines while platinum group elements are essential for catalytic converters on vehicles and for advanced chemical processing, but both resources are primarily obtained from foreign sources. Mine waste rocks represent promising hosts for rare earth elements, enabling reuse of materials already removed from the ground. Similarly, zones of ore rocks exposed at Earth’s surface and materials washed into nearby streams represent potential new sources of platinum group elements. The availability of critical minerals in these resource types, and the ability to extract them, are uncertain because these materials have been weathered by the action of sun, wind, and rain. This project will investigate how weathering affects critical minerals in mine wastes and exposed ore zones at three different locations in the United States. The new insight gained will improve the economic competitiveness of the U.S. and enhance national security by evaluating new domestic critical mineral resources through collaboration with industry and government partners. The project will also aid in the development of a domestic scientific workforce by training graduate and undergraduate students in critical minerals, an area of urgent national need. Further, it will encourage high school students from diverse backgrounds to pursue careers in science. The primary research focus of the project is the characterization of materials from distinct critical mineral resources at Earth’s surface. Study of waste materials from the Pea Ridge mine in Missouri will determine how rare earth elements mobilize and redistribute during weathering of iron oxide-apatite tailings, including from acid generated by sulfide mineral oxidation. At the Mountain Pass mine in California, investigation of tailings will show how these same elements transform during weathering of carbonatite ore waste materials. Evaluation of weathered ore zones in the Stillwater Complex in Montana will assess how platinum group elements transform and potentially accumulate in iron oxide minerals. The project will employ advanced microanalytical characterization tools as well as X-ray techniques at synchrotron lightsources to characterize the critical mineral occurrences in these mine tailings and weathered ore zones. This research will improve our understanding of the formation of novel, domestic critical mineral resources and support increased sustainability of resource extraction in the United States. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.