CHARACTERIZATION OF COAL RESOURCES IN THE U.S. GULF COAST AND RARE EARTH ELEMENT POTENTIAL

The ongoing energy transition from carbon-based fuels to renewable energy in the U.S. is increasing the demand for critical minerals such as Rare Earth Elements (REEs). Coal and coal by-products have long been known to contain appreciable quantities of metals, with some deposits today potentially being economically favorable. Within the Gulf Coast Basin there are seven active coal mines with total coal production of 20 million tons in 2019 where surface mining is used to extract coal to depths of up to 300 ft (~90 m). In our current study, we mapped the distribution of coals within the Gulf Coast Basin and quantified concentrations of REEs and other select metals in representative deposit samples. Coal thickness data were compiled from several databases, including data from the 2011 U.S. Geological Survey Gulf Coast Coal Assessment Report (https://doi.org/10.1306/St621328). Total coal thickness was mapped across the basin, including Texas, Louisiana, Arkansas, Mississippi, and Alabama. A total of 40 archived coal deposit samples from the U.S. Geological Survey were analyzed for their critical mineral contents. Regional isopleth maps of total coal thickness show coal extending from the Texas/Mexico border northeast to Mississippi/Alabama. The dominant coals are those from the Wilcox and Jackson Groups. These deposits are predominantly lignites with subbituminous coals restricted to Eagle Pass, Texas, near the Mexican Border. Texas accounts for ~53% of the coal tonnage within the top 100 m of depth, followed by Mississippi (28%), and Louisiana (14%). The corresponding coal tonnage is greatest in Texas (16.5 billion short tons), followed by Mississippi (8.7 billion short tons), and Louisiana (4.5 billion short tons). Preliminary REE results show elevated levels in samples from the Gibbons Creek mine (up to ~7800 ppm on a dry ash basis) and San Miguel mine (up to 930 ppm) in Texas. Future work will include detailed comparisons of Gulf Coast lignites with lignites from North Dakota and the Williston Basin, including REEs and critical minerals within and outside active coal mines. Our ongoing work demonstrates potential for REE recovery from coals in the Gulf Coast Basin.