LEVERAGING COAL FOR NON-FUEL, CRITICAL MINERAL RESOURCES: GEOLOGIC TRENDS IN RARE EARTH ELEMENT ABUNDANCE IN COAL-BEARING STRATA OF THE UINTA REGION, UTAH AND WESTERN COLORADO (Invited Presentation)

Identifying domestic critical mineral resources for modern technology and sustainable energy is a pressing societal challenge. Coal associated critical mineral resources, particularly rare earth elements, have been identified in the Appalachian region. They are more poorly constrained in the western U.S.

Based on existing and newly collected geochemical data, Cretaceous coal-bearing strata of the Uinta Region of Utah and western Colorado are variably rare earth element (REE)- enriched (> 200 ppm). REE-enriched intervals are most commonly found in carbonaceous siltstone and shale units that bound coal seams. Coal seams themselves are typically not REE-enriched, with a few exceptions. Igneous dikes that cross cut coal-bearing strata in one region show REE-enrichment.

This study focuses primarily on the coal-bearing intervals of the Cretaceous Blackhawk Formation (Fm), Ferron Sandstone, and Naturita Fm of Utah and the Mesaverde Fm of western Colorado. Secondary analysis was performed on volcanic tuff-bearing intervals of oil shale in the Eocene Green River Formation.

Portable X-ray fluorescence (pXRF) analysis (n =6202) on field-collected hand samples and core samples has been coupled with inductively coupled plasma mass spectrometry (ICP-MS) analysis on a subset of samples (n = 145). The dataset presented here is significantly expanded compared to previous USGS CoalQual REE datasets available for the Uinta Region (n = 88). Samples were collected and analyzed from eight active and three historic mine localities, five waste piles, three Mesaverde Fm cores, five Blackhawk Fm cores, nine Ferron Sandstone cores, seven Ferron outcrop or shallow mine localities, and six Green River Fm cores.

The results of this study indicate that carbonaceous shale-bearing floor and roof material of active coal mines may be a REE-enriched resource and require further resource assessment, mining engineering viability and economic evaluation. Igneous dikes found locally cross cutting coal seams and in hand samples in regional waste piles may be a limited REE resource. The study highlights the non-fuel resource potential of coal among a changing energy geology landscape.