SPATIAL AND TEMPORAL TRENDS OF RARE EARTH ELEMENT ABUNDANCE IN ILLINOIS BASIN COAL BEDS

Coal is currently being looked at as a potential alternative source of rare earth elements (REEs). Coal beds are complex assemblages of organic and inorganic materials, with a wide range of chemical composition, that contribute to a great range of variability in absolute concentrations and fractionation of rare earth elements. With this knowledge, it becomes critical to know which parts of coal beds have higher concentrations of REEs to enhance economic recovery. This study is an attempt to respond to such questions with mineable Illinois Basin coal beds as an investigation platform. The Illinois Basin is a major coal producing district in the Unites States extending across most of Illinois and parts of western Kentucky and southwestern Indiana. Stratigraphically, the study interval is situated in the Carbondale and Shelburn Formations (late Middle Pennsylvanian, Desmoinesian, Asturian), which includes the principle commercially extracted coal beds (Springfield, Herrin and Baker/Danville), along with the associated strata. Lateral and vertical variations of REEs in the coal beds, and variations related to temporal and spatial geological phenomena are illustrated and discussed. Collectively, the study illustrates, in fine detail, how REEs vary among, and within, the coal beds. Results are compared with average REE concentrations of the upper continental crust, which is frequently used as a ground base proxy for comparison.