HR: 1340h
AN: B13A-0200    [Abstracts]
TI: The Use of Stable Hydrogen Isotopes as a Geothermometer in Hydrothermal Systems
AU: * Proskurowski, G
EM: giora@u.washington.edu
AF: University of Washington, UW School of Oceanography, Seattle, WA 98195 United States
AU: Lilley, M D
EM: lilley@ocean.washington.edu
AF: University of Washington, UW School of Oceanography, Seattle, WA 98195 United States
AU: Fr�h-Green, G L
EM: gretli@erdw.ethz.ch
AF: ETH-Zentrum, Institute for Minerology & Petrology, Zurich, CH-8092 Switzerland
AU: Olson, E J
EM: olson@ocean.washington.edu
AF: University of Washington, UW School of Oceanography, Seattle, WA 98195 United States
AU: Kelley, D S
EM: kelley@ocean.washington.edu
AF: University of Washington, UW School of Oceanography, Seattle, WA 98195 United States
AB: Terrestrial geothermal work by Arnason in the 1970's demonstrated the utility of stable hydrogen isotopes as a geothermometer[1]. However, with the exception of two data points from 9�N in a study by Horibe and Craig[2], the value of this geothermometer in hydrothermal systems has never been rigorously assessed. Equilibrium fractionation factors for H2-H2O and H2-CH4 have previously been determined experimentally and theoretically over a range of temperatures and provide an expression relating alpha (fractionation) and temperature. We have measured the dD of H2(g), CH4(g) and H2O from a diverse selection of hydrothermal vent localities including Lost City, Middle Valley, Endeavour, Guaymas, Logatchev, Broken Spur, and SWIR. These samples were chosen to represent a wide range of fluid temperatures and a variety of environmental settings. We see a strong correlation between measured vent temperature and predicted vent temperature using both the hydrogen-water and the methane-hydrogen geothermometers over a temperature range of 25-400�C. In the case of the H2-H2O geothermometer, the predicted temperatures are slightly elevated with respect to the measured temperatures at the low temperature Lost City site, and are in good agreement at high temperature vent sites. The H2-CH4 geothermometer predicts temperatures that are 40-80�C elevated with respect to the measured temperature in both the low and high temperature sites. These measurements demonstrate that the hydrogen isotope geothermometer in the hydrogen-methane-water system is robust in hydrothermal systems and may be a useful tool in determining the temperature of the root zone. 1. Arnason, B., The Hydrogen-Water Isotope Thermometer Applied to Geothermal Areas In Iceland. Geothermics, 1977. 5: p. 75-80. 2. Horibe, Y. and H. Craig, D/ H fractionation in the system methane-hydrogen-water. Geochimica et Cosmochimica Acta, 1995. 59(24): p. 5209-5217.
DE: 4820 Gases
DE: 4825 Geochemistry
DE: 4870 Stable isotopes
DE: 3035 Midocean ridge processes
DE: 0370 Volcanic effects (8409)
SC: Biogeosciences [B]
MN: 2004 AGU Fall Meeting