THE SEARCH FOR RARE EARTH ELEMENTS (REES) IN LIGNITE COAL SEAMS WITH X-RAY DIFFRACTION (XRD): A CASE STUDY FROM THE CRETACEOUS EAGLE FORMATION, ELK BASIN, PARK COUNTY, WYOMING, USA

REEs are essential to the economy of the United States and our infrastructure; without a domestic source, our national security could be threatened. In response, the US governments has been incentivizing locating sources of REEs in domestic territory. Some areas of interest include pre-existing quarries and mines, as these sites are already exposed and well-researched, allowing for a more economically efficient usage with less environmental impact when compared to creating new mining sites.

This case study investigates a prospective source of REEs in the Eagle Formation, exposed in Elk Basin Oil field in Park County, Wyoming, USA. The Late Cretaceous Eagle Formation is composed of light gray to tan coarse-grained sandstones that contain well-exposed lignite outcrops. X-ray diffraction (XRD) and X-ray fluroscence (XRF) analysis allows us to view the elemental and mineral composition of lignite and surrounding strata, looking for host minerals that could contain REEs and establishing a chemostratigraphic framework for the Eagle Formation. These chemostratigraphic and analytical techniques are being applied to draw connections between the Eagle’s lignite coal seams and minerals that contain REEs.