LITHIUM IN FLUIDS FROM PALEOZOIC-AGED RESERVOIRS, APPALACHIAN PLATEAU REGION, USA

The trace element, lithium (Li⁺), in fluids is an indicator of water-rock reaction in saline sedimentary basin fluids, because it is present in very low concentration in seawater and in evaporated seawater, the most likely burial fluids, and it exists in extremely low concentration in marine evaporative salts, which are the most likely additional source of chloride (Cl^-) greater than seawater concentrations. We present a compilation of lithium and selected other dissolved species concentrations in saline fluids from oil and gas wells in western Pennsylvanian and eastern Ohio that are producing from Silurian to Devonian-aged formations. The Li/Cl in these fluids is not constant, suggesting multiple types of Cl-rich water and/or multiple sources of Li. The Li/Cl ratio increases from west to east across the study area in four or five bands of similar Li/Cl. Li and Li/Cl are not correlated with petroleum-production formation and are only generally correlated with depth. Based on the spatial distribution of the solutes and solute ratios, we present some working hypotheses for end member fluid compositions that explain the three-dimensional distribution of lithium in this segment of the Appalachian Plateau Province, and that provide insight into paleoflow conditions in the region.