EVALUATION OF COAL RESOURCES AND RARE EARTH ELEMENT LEVELS IN THE US GULF COAST

Rare earth elements (REEs) are critical for economic growth, national security, and technological advances in the United States. The objective of this study was to estimate coal resources and REE levels in the Gulf Coast region of the US. Isopleth maps of cumulative coal thickness were developed based on stratigraphic data for 30,100 boreholes and REE levels were measured in ~60 archived USGS samples representing the major mines. Most coals in the Gulf Coast are lignite. Results show there is an estimated ~85 billion tons of coal in the Gulf Coast Basin, with Texas accounting for 43% of the total, followed by Mississippi (25%), Louisiana 13% and Tennessee (10%). The remaining states accounted for < 5% of the total each. The estimated coal resources increased with depth from 3 billion tons in upper 15 m to 85 billion tons in upper 90 m. Historically, there were a total of 28 mines in the Gulf Coast; however, only six are currently active, four in Texas and one each in Louisiana and Mississippi. Median total REE level + Yttrium + Scandium in 64 coal samples is ~440 mg/kg on an ash basis. Higher levels were restricted to two mines in Texas (Gibbons Creek mine: range 1,070 – 7,800 mg/kg; San Miguel: range 150 – 940 mg/kg). Reconnaissance analysis indicates that the REEs are concentrated within the organics, similar to North Dakota lignite, making the REEs more readily extractable. This reconnaissance work suggests that Gulf Coast coals provide a promising source of these elements.