Aspects of rare earth element geochemistry of the Pond Creek coalbed, Pike County, Kentucky

The chemistry of rare earth elements (REE) and selected critical elements was examined in the high volatile A bituminous Pond Creek coal in Pike County, Kentucky. The Pond Creek coal has been one of the most important coal resources in eastern Kentucky but, up to now, no modern methods, such as Inductively coupled plasma – mass spectroscopy (ICP-MS) have been applied to the characterization of the rare earth elements within the coal. The concentration of the REE and their internal distribution (light REE/heavy REE) varies between lithotypes through the coal, ranging from <300-ppm REE at the top of the coal to >1000-ppm REE in the bright lithotype (zone 4) in the middle of the coal. The latter lithotype has the highest light REE/heavy REE, suggesting that the mire was isolated from detrital sources of REE-bearing minerals and, instead, was influenced by hydrothermal enrichment emanating from the movements along the Pine Mountain trust fault to the south of the study area. The Mn + Fe₂O₃ + CaO and Sr + Ba chemistry of the lithotype suggests that it's precursor mire was less acidic than other bright lithotypes with the Pond Creek profile, however the upward change in the chemistry indicates a temporal acidification of the zone 4 lithotype.