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Paper No. 113-9
Presentation Time: 3:30 PM
RARE EARTH ELEMENT AND CRITICAL MINERAL ENRICHMENT IN COAL-ADJACENT STRATA OF THE UINTA REGION, UTAH AND WESTERN COLORADO
This study provides a comprehensive coal-associated rare earth element (REE) and critical mineral (CM) resource evaluation from the Uinta Region, central Utah and western Colorado. Rare earth element (REE) and critical mineral (CM) resources are essential for modern technology and the transition to carbon-neutral energy sources. REE and CM-enrichment has been demonstrated in coal and coal-adjacent strata in some U.S. regions but has not been rigorously evaluated in the coal-bearing Uinta Region of central Utah and western Colorado. Limited existing REE data available from the Uinta Region (n = 88, United States Geological Survey, USGS, CoalQual database) show limited REE-enrichment in coal samples. 27% of samples contain >100 pm total REE concentration and 3% >200 ppm. However, new geochemical analyses indicate significantly more REE-enrichment in coal-associated strata, more so than existing USGS data from coals. New geologically guided sampling of coal resources and coal-adjacent strata has been conducted, with a geographic focus on mines and coal processing waste piles. Samples have been geochemically evaluated by coupling inductively coupled plasma-mass spectrometry (ICP-MS) and portable X-ray fluorescence (pXRF) to identify REE and CM-enriched strata and samples. Results suggest that particular carbonaceous shale units, commonly adjacent to coal seams, are REE-enriched. For this study, REE-enrichment is defined as REE >200 ppm from selective pXRF methods (Ce, La, Nd, Pr, and Y only) or total REE >300 ppm from ICP-MS methods. Locally, igneous dikes that cross cut coal seams are REE-enriched (total REE >300 ppm and up to ~1000 ppm). Waste pile samples of carbonaceous shale and igneous dikes show REE-enrichment. Some coal and carbonaceous shale samples from previous coal processing display significant REE-enrichment. Further evaluation of the stratigraphic and lateral variability of REE and CM-enriched intervals is needed to quantify the resource volume. Investigation of the mineralogical association and geologic controls on REE and CM-enrichment in coal-associated strata is ongoing.