REEY CONCENTRATIONS IN SHALES AND FIRECLAYS FROM WV INVESTIGATED USING ICP-AES AND SEM

Rare Earth Elements and Yttrium (REEYs) are integral to industry and the demand for REEY has increased dramatically given their use in automotive manufacturing and electronic devices. This has led scientists to explore for sources of REEY other than the traditional igneous carbonatites. These unconventional sources include fireclays and shales associated with coal seams in Appalachia, particularly West Virginia.

We collected and analyzed 68 samples of shales, fireclays, and tonsteins from Pennsylvanian aged units throughout WV. This was completed using inductively coupled plasma atomic emission spectroscopy (ICP-AES) after careful selection of rock standards for calibration curves. The results show that samples from the Lower and Upper Freeport and Lower Kittanning members of the Alleghany formation collected from the northern panhandle and the Pittsburgh member at the base of the Monongahela Formation of the Milton area contain ΣREEY values > 350 ppm, indicating some economic potential. However, it is necessary to identify the minerals that contain these elements, which will determine how they will be extracted from the source rock. To investigate the source of REEY and their host minerals, we analyzed two shales with the highest ΣREEY values from the Pittsburgh member in Milton using backscattered electron imaging and energy dispersive spectrometry (EDS) attached to the scanning electron microscope (SEM).

Results show that the shales consist of kaolinite, illite, potassium feldspar, plagioclase feldspar, and chlorite. Zircon, ilmenite, xenotime, monazite, and apatite are common accessory minerals constituting < 5 volume %. REEY are concentrated in angular to subrounded monazite and xenotime, which are clearly detrital with average grain sizes of 360 and 340 square microns, respectively. EDS spectra indicate that the clay minerals do not contain any REEY. This suggests that REEY were not carried by fluids; as precipitation of these elements would cause them to be adsorbed onto the surface of the clay minerals.