RARE EARTH ELEMENTS (REE) AND OTHER CRITICAL MINERALS IN LATE CRETACEOUS COAL AND RELATED STRATA IN THE SAN JUAN BASIN, NEW MEXICO: PRELIMINARY OBSERVATIONS

Critical minerals, including rare earth elements (REE), are becoming increasingly more important in our technological society because they are used in many of our electronic devices (such as cell phones, computer monitors, wind turbines, etc.), batteries, and magnets. In New Mexico, low to moderate concentrations of REE and other critical minerals are found in Late Cretaceous coal and related strata in the San Juan and Raton Basins. These rocks are being characterized as part of the DOE’s CORE-CM (Carbon Ore, REE, and Critical Minerals) program. Three types of deposits are discussed here. Coal deposits form in swamps near the Late Cretaceous coastline. Humates are weathered coal that are produced from both coal and humate mines, and are used as soil amendments and dyes. Clinkers are naturally burned coal and adjacent strata and are used in road construction and as a flux. The New Mexico coal, humate, and clinker deposits are relatively low in REE (<325 ppm TREE), Li (<90 ppm), V (<168 ppm), Co (<51 ppm), Ni (<108 ppm), Zr (<557 ppm), Hf (<14 ppm), and many other critical minerals compared to normal economic deposits. However, some of these rocks are enriched in Al₂O₃ (as much as 40%) and Sr (as much as 3740 ppm), both critical minerals. Common minerals hosting the critical minerals in these rocks include clay minerals, zircon, and rutile/anatase. Potential geologic sources of REE and other critical minerals in New Mexico coal, humate, and clinker deposits include Proterozoic granitic and metamorphic rocks (such as those found in the Zuni and Nacimiento Mountains), the Jurassic-Cretaceous arc volcanism and magmatism forming the Mogollon Highlands to the south and west, and recycling of older sediments, although hydrothermal or weathering fluids could concentrate some of the critical minerals. Coal may also be a potential source of carbon fiber, coking coal, and graphite. More chemical and mineralogical analyses are required to fully understand the distribution and origin of REE and critical minerals in these deposits. As the demand for some of these elements increases because of increased need and short supplies, the dollar value per ton of ore rises, enhancing deposit economics. Ultimately, economic potential will most likely depend upon production of more than one commodity, maybe even from coal, humate, and clinker deposits.