HR: 15:00h
AN: OS53B-05    [Abstracts]
TI: Properties of Sea Floor Hydrates From the Gulf of Mexico
AU: * Bohrmann, G
EM: gbohrmann@uni-bremen.de
AF: Earth Sciences University Bremen, Klagenfurterstr., Bremen, 28359, Germany
AU: Klapp, S A
EM:
AF: Earth Sciences University Bremen, Klagenfurterstr., Bremen, 28359, Germany
AU: Abegg, F
EM:
AF: Earth Sciences University Bremen, Klagenfurterstr., Bremen, 28359, Germany
AU: Kuhs, W F
EM:
AF: GeoZentrum University Göttingen, Goldschnmittstrasse, Göttingen, 37077, Germany
AB: Near-surface methane hydrates are well known from numerous seep sites on active and passive continental margins. The hydrates exhibit a characteristic macroscopic and microscopic fabric as shown by samples recovered from a large range of water depths. In the Gulf of Mexico gas hydrates have been sampled from shallow northern slope in the Green Canyon area between 600 and 1000 m water depth and in the southern Gulf in 3300 m water depth. The internal fabric of pure gas hydrate has a peculiar structure with pores that result from rising methane gas. The porous gas hydrate structure could also be observed at the surface of gas hydrate outcrops in 3300 m water depth using ROV QUEST during METEOR cruise M67/2. Fabric analyses of hydrate samples indicate that at least parts of the hydrate are formed from free methane gas. Free gas migrates upwards through the sediment column and is also indicated by gas bubbles emanating at the seafloor. These bubbles form plumes in the water column. Gas hydrate decomposition and ice formation is also documented by cryo- stage X-ray diffraction and Rietveld analyses. Preservation of structure I hydrates various between 40-70% and has a average preservation of 60%. Preservation of structure II hydrates from the Gulf of Mexico is much better, which is explained by shallower stability curve of such hydrates.
DE: 3004 Gas and hydrate systems
SC: Ocean Sciences [OS]
MN: 2007 Joint Assembly