HR: 17:00h
AN: OS52D-05    [PDF]
TI: Innovations in Sampling Pore Fluids From Deep-Sea Hydrate Sites
AU: * Lapham, L L
EM: llapham@unc.edu
AF: Dept of Marine Sciences, University of North Carolina at Chapel Hill, 12-7 Venable Hall, CB#3300, Chapel Hill, NC 27599 United States
AU: Chanton, J P
EM: jchanton@mailer.fsu.edu
AF: Dept of Oceanography, Florida State University, Tallahassee, FL 32306 United States
AU: Martens, C S
EM: cmartens@email.unc.edu
AF: Dept of Marine Sciences, University of North Carolina at Chapel Hill, 12-7 Venable Hall, CB#3300, Chapel Hill, NC 27599 United States
AU: Schaefer, H
EM: schaefer@uvic.edu
AF: School of Earth and Ocean Sciences, University of Victoria, PO Box 3055, Victoria, BC V8W 3P6 Canada
AU: Chapman, N R
EM: chapman@uvic.edu
AF: School of Earth and Ocean Sciences, University of Victoria, PO Box 3055, Victoria, BC V8W 3P6 Canada
AU: Pohlman, J W
EM: jp@vims.edu
AF: Virginia Institute of Marine Sciences, College of William and Mary, PO Box 1346, Gloucester Point, VA 23062 United States
AB: We have developed a sea-floor probe capable of collecting and returning undecompressed pore water samples at in situ pressures for determination of dissolved gas concentrations and isotopic values in deep-sea sediments. In the summer of 2003, we tested this instrument in sediments containing gas hydrates off Vancouver Island, Cascadia Margin from ROPOS (a remotely operated vehicle) and in the Gulf of Mexico from Johnson-Sea-Link I (a manned submersible). Sediment push cores were collected alongside the probe to compare methane concentrations and stable carbon isotope compositions in decompressed samples vs. in situ samples obtained by probe. When sufficient gas was available, ethane and propane concentrations and isotopes were also compared. Preliminary data show maximum concentrations of dissolved methane to be 5mM at the Cascadia Margin Fish Boat site (850m water depth) and 12mM in the Gulf of Mexico Bush Hill hydrate site (550m water depth). Methane concentrations were, on average, five times as high in probe samples as in the cores. Carbon isotopic values show a thermogenic input and oxidative effects approaching the sediment-water interface at both sites. This novel data set will provide information that is critical to the understanding of the in situ processes and environmental conditions controlling gas hydrate occurrences in sediments.
DE: 1050 Marine geochemistry (4835, 4850)
SC: Ocean Sciences [OS]
MN: 2003 Fall Meeting