QUALITATIVE RARE EARTH ELEMENT ANALYSIS OF OHIO UNDERCLAYS USING PORTABLE X-RAY FLUORESCENCE

Aluminum-rich clays and claystones associated with Pennsylvanian- and Permian-age coal horizons can be found throughout eastern Ohio. Previous research in Pennsylvania and West Virginia has highlighted similar deposits as possible sources of Rare Earth Elements (REE). Samples were gathered from sites covering most of the Pennsylvanian and Permian outcrop belt in Ohio, with subsamples taken at regular intervals throughout the clay. Samples were dried and powdered in preparation for analysis via portable X-ray fluorescence (pXRF) in order to qualitatively assess REE content. While the pXRF can only measure four of the REEs (lanthanum, cerium, praseodymium, and neodymium), some associations emerge. In preliminary data, total REE content ranges from about 50 ppm to over 350 ppm, with an average of 210 ppm. Average clay/shale REE content over these four elements is 183 ppm. Currently, the greatest concentrations occur in the Lower Kittanning underclay and red Conemaugh Group shale. The lowest concentration comes from the Middle Mercer underclay. The data does not indicate correlation between total REE concentration and proximity of the subsample to the overlying coal. A comparison of total REE versus other major element concentrations shows a direct correlation with iron. This association coupled with a weak aluminum correlation suggests the possibility that the REEs are not adsorbed onto the clay minerals but instead may be hosted in iron minerals in the clay. Further analysis via tabletop XRF and X-ray diffraction (XRD) is required to confirm these results. If accurate, these associations may be able to help target intervals with the greatest potential for future economic use and give an insight into the origins of these REE-rich units.