CHARACTERIZING UTICA SHALE DEPOSITIONAL PROCESSES USING PORTABLE XRF ANALYSES AND POSITIVE MATRIX FACTORIZATION

Interest in mudrocks has grown over the past two decades due to innovations in drilling and completion technology allowing for economic hydrocarbon extraction of resources directly from source rocks. This has resulted in an abundance of data obtained via a variety of analytical equipment such as portable x-ray fluorescence spectroscopy (pXRF). This study aims to develop a workflow to utilize Environmental Protection Agency: Positive Matrix Factorization (EPA PMF) with pXRF data of mudrocks. EPA PMF is a multivariate receptor model typically used to quantify the composition and contribution of source factors in aerosol samples which we have adapted to geologic studies. Our approach uses PMF on pXRF data from core and drill cutting samples to provide a statistically-based quantitative analysis of elemental proxy information that has the potential to identify cryptic stratigraphic variability. Elemental concentrations from the Flat Creek Shale and Indian Creek Shale of the Utica Group and portions of the Trenton Group were measured in three drill cores in the Mohawk Valley, central New York State, using (pXRF). A suite of 29 elements were measured at a 10-inch spacing in one core and 3-inch spacing in two additional cores. The resulting data and associated variability were used as the input parameters for the PMF model. PMF returned a best fit solution that included contributions from carbonates (Ca, Fe), siliciclastics (Si, Al, Mg), biogeochemical metals (V, Ni, Cu, Zn, Mo), sulfides (S, Fe, As, Mo), diagenetic processes (Ca, Sr) and two lesser factors that may be indicators of sediment provenance or diagenetic processes. When the PMF-calculated output factors are plotted, depositional processes can be interpreted that correspond with lithologic facies that have been described using traditional techniques.