TRACE ELEMENT CONTENT OF THE MARCELLUS SHALE

The Marcellus shale has the potential for the mobilization of trace elements and water contamination during development and production. The results of over 150 ICP-MS analyses of drill cuttings from the unit across New York are presented documenting the stratigraphic and geographic variations in metals content within the unit, and comparison with upper continental crustal averages (UCC) and other shale units from New York. For purposes of this study, the unit was divided into the Oatka Creek, Chittenango, Cherry Valley, and Union Springs (US) members of the Marcellus Shale. In general, trace element abundances increase down section. The US member displays the greatest enrichment in trace elements compared to the UCC and other members; however, these values represent complete digestion of rock powders and cannot be compared directly to leaching experiments. Enrichments in the US member that average over two times those reported for the UCC include Se (UCC estimate – 0.09 ppm; average enrichment - 84.5x; range of enrichment - 45.2-150.0x), Mo (1.1 ppm; 61.8x; 34.1-98.8x), Cd (0.09 ppm; 23.7x; 5.6-49.1x), Ag (.053 ppm; 11.3x; 9.4-15.1), U (2.7 ppm; 6.7x; 3.1-9.7), As (4.8 ppm; 4.6x; 1.8-7.2x), Sb (0.4 ppm; 4.1x; 1.3-6.8), Hg (0.05 ppm; 3.8x; 2.3-5.8x), Cu (28 ppm; 3.6x; 1.9-5.5x), Ba (628 ppm; 3.1x; 0.5-10.0x), V (97 ppm; 2.8x; 1.0-4.4x), Zn (67 ppm; 2.5x; 0.9-5.3x), Ni (47 ppm; 2.2x; 0.8-3.1x), and Pb (17 ppm; 2.1x; 1.0-3.1x). Enrichments in Ag, As, Ba, Cd, Mo, Se, and U of at least two times over upper crustal crustal averages are typical throughout the entire Marcellus Shale sequence and the upper portion of the underlying Onondaga limestone. The Oakta Creek and Cherry Valley members are most enriched in Schuyler and Tompkins Counties (central part of the basin) while values for the US are variable but with the most enrichment seen in samples from Chautauqua to Schulyer counties (west and central parts of the basin). Of twenty five other New York shales, only the late Devonian Middlesex Shale was similarly enriched to the Union Springs member including Se: (47.8x), Mo (74.9x), Cd (4.4x), Ag (7.6x), U (6.3x), As (4.2x), Cu (4.0x), V (4.3x), Ni (2.2x), and Pb (3.2x). Unrestricted use soil cleanup objectives for metals at New York State Brownfield sites were exceeded by the maximum concentration in the US for As and Ba only.