Surface Geochemical Tools for Hydrocarbon Exploration and Structural Mapping in the Great Basin of Nevada and Utah

David M. Seneshen, James H. Viellenave, and John V. Fontana. Direct Geochemical, 130 Capital Drive, Suite C, Golden, CO 80401, phone: 303 277 1694, fax: 303 278 0104, [email protected]

The innovative application of both organic and inorganic surface geochemical tools has facilitated exploration and structural mapping in the Great Basin. More specifically, the interrelationship of C1-C8 hydrocarbons in soils is used to predict “oil-prone” areas and the major and trace element concentrations in soils map the spatial distribution of underlying hydrothermal dolomites and faults. Soils over normal faults that bound oils typically have higher concentrations of heavy hydrocarbons (>C5), carbon dioxide, carbon monoxide, uranium, halogens, alkaline earth metals (i.e. Mg, Ca, and Sr) and lower concentrations of transition metals (e.g. Fe, Mn, Ni, etc.). Soils directly over the oil fields have unique multivariate hydrocarbon ratios that distinguish them from barren unproductive areas. These hydrocarbon ratios are used to predict oil potential in unknown areas. Case studies from several areas of the Great Basin in Nevada and western Utah compiled over a seven-year period will be presented to emphasize the potential of these tools for both oil exploration and structural mapping in this extensional geological environment.