RARE EARTH ELEMENTS (REE) IN LATE CRETACEOUS COAL AND BEACH-PLACER SANDSTONE DEPOSITS IN THE SAN JUAN BASIN, NEW MEXICO: PRELIMINARY OBSERVATIONS

Rare earth elements (REE) and other critical minerals (Ti, Zr, U, Th, Nb) are found in Late Cretaceous coal and beach placer deposits in the San Juan Basin, NM. Many of these critical minerals, especially Ti and REE, are increasingly becoming more important in our technological society and are used in many of our electronic devices, such as cell phones, computer monitors, wind turbines, etc. Ti is used in paints and glazes. The coal deposits are relatively low in REE and other critical minerals and are less than the concentrations found in beach-placer sandstones. The REE plots of coal deposits exhibit relatively flat-REE chondrite-normalized enriched patterns, typically with slight negative Eu anomalies. The coal deposits form in swamps near the beaches. Beach-placer sandstone deposits are concentrations of heavy minerals that formed by mechanical concentrations (i.e. settling) of heavy minerals on beaches or in longshore bars in a marginal-marine environment. The REE plots of beach-placer deposits exhibit light-REE chondrite-normalized enriched patterns, typically with negative Eu anomalies. The beach-placer sandstones are typically underlain by nearshore marine sandstone and overlain by nonmarine fine-grained sandstone, carbonaceous shale, and coal. The beach-placer sandstone deposits in the San Juan Basin are small tonnage, low grade, well-cemented, and have a high iron content. Not only do these deposits represent potential future economic resources, they also help define local depositional trends of the Cretaceous beaches at the time of deposition. Potential sources of both beach-placer and coal deposits include Proterozoic granitic and metamorphic rocks, such as those found in the Zuni Mountains, the Jurassic arc volcanism and magmatism forming the Mogollon Highlands to the south and west, and recycling of older sediments. More chemical analyses are required to fully understand the distribution of REE and critical minerals in both types of deposits. However, 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 both coal and beach-placer deposits.