INVESTIGATING SPATIAL AND TEMPORAL CHANGES OF TRACE ELEMENT ABUNDANCE IN DEVONIAN SHALES OF KENTUCKY

Devonian shales of the Illinois and Appalachian Basins have been studied extensively for their petroleum and critical element resources, as hydrogen and carbon dioxide seals and reservoirs, and to better understand the tectonic evolution of their respective basins. Previous studies focused their efforts on discrete core and/or outcrop sampling, restricting the validity of their conclusions to the area immediately surrounding their sampling localities. This study seeks to understand the variable characteristics of the Devonian shales spatially by examining core in the Illinois and Appalachian Basins and across the Cumberland Saddle that intersects the two basins, and temporally by examining the full depositional suite of Devonian shales in Kentucky. This is to be accomplished by gathering trace element data with a handheld x-ray fluorescent spectrometer at a 1-ft vertical resolution on 65 cored intervals of Devonian shale, totaling about 9,000 ft of core throughout Kentucky. Preliminary results indicate minor spatial changes in the enrichment of trace elements except in discrete areas where significant enrichment of trace elements is observed (for example, enrichment factors of molybdenum in excess of 800). Generally, an inverse correlation between average trace element concentration and isochore thickness is observed, which may be the result of changing sediment sources, depositional conditions, or both. To further investigate the spatial and temporal changes of trace element concentrations, three to four of the analyzed cores will be sampled for organic maturity and content, uranium isotopes, and trace element analysis by mass spectrometry. Expected results will help resolve the controlling factors of trace element enrichment while helping to identify potential resources for future critical mineral extraction.