GEOCHEMICAL VARIATIONS OF RARE EARTH ELEMENTS IN MARCELLUS SHALE FLOWBACK WATERS AND MULTIPLE-SOURCE CORES IN THE APPALACHIAN BASIN

Rare earth elements (REE) – encompassing the naturally occurring lanthanides, yttrium, and scandium – are potential tracers for subsurface groundwater-brine flows and geochemical processes. Application of these elements as naturally occurring tracers during shale gas development is reliant on accurate quantitation of trace metals in hypersaline brines. We have modified and validated a liquid-liquid technique for extraction and preconcentration of REE from saline produced waters from shale gas extraction wells with quantitative analysis by ICP-MS. This method was used to analyze time-series samples of Marcellus shale flowback and produced waters. Additionally, the total REE content of core samples of various strata throughout the Appalachian Basin were determined using HF/HNO₃ digestion and ICP-MS analysis. A primary goal of the study is to elucidate systematic geochemical variations as a function of location or shale characteristics. The results of these analyses and discussion of their significance will be presented.