CORE TO LOCAL SCALE ASSESSMENT OF REE AND CRITICAL MINERALS IN SEDIMENTARY ROCKS FROM THE POWDER RIVER BASIN (Invited Presentation)

Existing methodologies for sampling and analysis of conventional mineral deposits has resulted in underrepresentation of key data needed to assess the resource potential of unconventional critical mineral (UCM) feedstocks. This work contributes to an overarching effort to develop methodical and systematic data collection methods to aid in the characterization and assessment of UCM resources in domestic geologic deposits. Here we demonstrate the reliability and level of data quality for non-destructive in-situ measurements of REE and other critical elements in geologic materials using a portable x-ray fluorescence analyzer (pXRF). A suite of standard reference materials and field samples were used to evaluate and optimize scanning parameters for different rock types present in coal bearing and non-coal bearing sedimentary strata found in the Powder River Basin. Field scale analysis by pXRF was used to analyze and map element concentrations in drilled rock cores from the Brook Mine, Sheridan Wyoming. Geochemical logs were used in conjunction with geophysical logs, core descriptions, and electron microscopy to assist in identifying critical mineral occurrence and enrichment at the core scale. Upscaling to seam and mine scale was done through analysis and correlation of geochemical, lithological, and stratigraphic data obtained through the analysis of 100+ cores collected at the mine site. The spatial data collected was used to map UCM resource enrichments at the core and seam scale. The results also provided key data to perform confidence testing of the NETL Unconventional Resource assessment tool for the PRB and can be applied to locate other promising domestic sources of unconventional critical minerals in Western North America.