Rare earth elements (REEs) in shale deposits show increasing interest because of their unique profile in minerals as well as in pore water of shales. For unconventional gas extraction processes, REEs show potential as naturally occurring tracers of subsurface fluid migration both during and after hydraulic fracturing as well as tools for source identification and apportionment in the event of shallow groundwater contamination. In this study, we screened Marcellus Shale outcrop samples for REEs using inductively-coupled plasma mass spectrometry (ICP-MS).  The samples were collected from different organic-rich shale formations from seven geographic locations in West Virginia, Virginia, Pennsylvania, and New York with surface exposures of the Middle Devonian Marcellus. The shale samples were prepared using three methods to quantitatively measure the REE abundance: HF/HNO3 acid digestion, lithium metaborate fusion, and sodium peroxide fusion. Analysis was performed using an external calibration technique and internal standards were used to correct for instrumental drift and matrix effects. Appropriate interference corrections were employed during the analysis. Results obtained using the above three methods of sample preparation were compared to provide insights for quantitative analysis of shales for REEs. Understanding of geologic abundance and variability is crucial to future applications of REEs as tracers in the aqueous phases in contact with these shales.

Methods to assess the abundance of rare earth elements (REEs) in shales: The Marcellus Shale

248th National Meeting (2014)

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