HR: 0800h
AN: OS41C-0491    [Abstracts]
TI: Characterization of Gulf of Mexico Sediment in Hydrate and Non-Hydrate Bearing Cores Using Specific Surface Area
AU: * Gilbert, L Y
EM: lgilbert@usgs.gov
AF: U. S. Geological Survey, 384 Woods Hole Rd., Woods Hole, MA 02543 United States
AU: Waite, W F
EM: wwaite@usgs.gov
AF: U. S. Geological Survey, 384 Woods Hole Rd., Woods Hole, MA 02543 United States
AU: Winters, W J
EM: bwinters@usgs.gov
AF: U. S. Geological Survey, 384 Woods Hole Rd., Woods Hole, MA 02543 United States
AU: Mason, D H
EM: dmason@usgs.gov
AF: U. S. Geological Survey, 384 Woods Hole Rd., Woods Hole, MA 02543 United States
AB: Specific surface area (SSA) measurements made on four cores recovered in the Mississippi Canyon region of the Gulf of Mexico suggest that SSA is not a controlling factor in hydrate formation. SSA was determined using the single point Brunauer, Emmett, and Teller (B.E.T.) method on a Quantachrome Quantasorb Sorption System. This method uses thermal conductivity to measure the volume of nitrogen adsorbed and desorbed from the sample surface. Core MD02-2569, 10.35 m in length, was collected in 1032 m of water and had gas hydrate veins up to 2 cm thick. SSA measurements were made at 6.45 m below seafloor (mbsf) and 8.16 mbsf. Core MD02-2573, which also contained hydrate, was 4.2 m long, and was located 28 m from MD02-2569 in 1027 m of water. SSA measurements were made at .30, 3.25, and 4.0 mbsf. Core MD02-2569 had SSA values ranging from 26.01-27.6 m$^{2}$/g. Core MD02-2573 had higher SSA values ranging from 30.96 to 32.92 m$^{2}$/g excluding the .3 mbsf sample, which yielded a SSA value of 22.61 m$^{2}$/g. MD02-2570 and MD02-257, non-hydrate bearing cores recovered $\sim$3 km apart and $\sim$22 km southwest of MD02-2573, were collected at depths of 631 and 664 m. Each produced similar SSA values (30.94 to 32.40 m$^{2}$/g and 31.55 to 35.61 m$^{2}$/g) to core MD02-2573 and MD02-2570 produced a lower SSA value of 22.4 m$^{2}$/g at .50 m below the surface. The presence of gas hydrate in cores MD02-2569 and MD02-2573, both collected at similar water depths and locations, but with different SSA, suggests that SSA is not a dominant factor in hydrate formation. This is supported by the similarity of SSA values of core MD02-7573 as compared to cores MD02-2570 and MD02-2571, all from varying locations within the hydrate stability field. We interpret that hydrate formation may be more dependent on water depth and local environmental variations (e.g. gas saturation, gas flux) than on SSA.
DE: 5100 PHYSICAL PROPERTIES OF ROCKS
DE: 5194 Instruments and techniques
DE: 3000 MARINE GEOLOGY AND GEOPHYSICS
SC: Ocean Sciences [OS]
MN: 2004 AGU Fall Meeting