HR: 16:15h
AN: B54C-02    [Abstracts]
TI: Pore fluid chemistry of cold seeps in the Sea of Marmara
AU: * Tryon, M D
EM: mtryon@ucsd.edu
AF: Scripps Institution of Oceanography, UCSD, 9500 Gilman Dr., 0244, La Jolla, CA 92093- 0244, United States
AU: Cagatay, N
EM: cagatay@itu.edu.tr
AF: Istanbul Technical University, Faculty of Mines, Geology Department, Maslak, Istanbul, 84469, Turkey
AU: Henry, P
EM: henry@cdf.u-3mrs.fr
AF: CEREGE/Collège de France, Europôle de l'Arbois - Batiment Trocadéro - BP80, Aix-en- Provence, 13545, France
AU: Zitter, T
EM: zitter@cdf.u-3mrs.fr
AF: CEREGE/Collège de France, Europôle de l'Arbois - Batiment Trocadéro - BP80, Aix-en- Provence, 13545, France
AU: Géli, L
EM: Louis.Geli@ifremer.fr
AF: IFREMER, Marine Geosciences Department, BP 70, Plouzané, 29280, France
AU: Charlou, J
EM: charlou@ifremer.fr
AF: IFREMER, Marine Geosciences Department, BP 70, Plouzané, 29280, France
AU: Shipboard Scientific Party, M
EM: henry@cdf.u-3mrs.fr
AB: During the Marnaut cruise in the Sea of Marmara, south of Istanbul, fluid and gas seeps were identified and explored along the Main Marmara Fault, the submerged western extension of the North Anatolian Fault Zone that cuts across the entire length of the sea. Our objective was to study the relationship between fluid expulsion sites and active faults at a transform plate boundary. Utilizing the Nautile submersible, ten cold seep sites spanning the fault zone were explored. The tectonic environments of the seeps included strike-slip faults in transtensional and transpressive contexts, normal faults, folds and landslides. Most seeps were extensive, patchy, and diffuse, displaying patches of black sulfidic sediment with typically white to yellow/orange microbial mat on the surface. One endmember type was highly focused, emitted ambient temperature shimmering fluids of low salinity that precipitated chimney structures. At other sites gas bubbles were seen coming from both the sediment cover and from open fractures. Another type had the appearance of a mud volcano with bacteria covered sediment and a fan morphology extending downslope from the seep. This latter site was associated with very high salinity fluids and significant traces of hydrocarbons and included shallow gas hydrate well outside its normal stability field. Hypothetically, the brackish water seeps (already known from Marmarascarps ROV cruise) can be explained by a local fluid source of lake water trapped in the first 100 m of sediment during the last glaciation. However, deeper sources are required at the hydrocarbon emission site and, probably, contribute to steady gas bubble flow at other sites. Push cores were collected, where possible, at the seeps for chemical and biological analysis. As all seeps had carbonate crusts or outcrops to a varying degree this was not always successful. Kullenberg piston cores of up to 10 m were also collected in the seep areas during night operations. Fluids were extracted at intervals along the cores using vacuum extraction (Rhizon). Pore fluids from these cores exhibit chlorinities from 100 to over 1000 mM and a comparably wide range of other major and trace ion compositions. We will report the preliminary results of these core pore fluid analyses.
UR: http://tryonlab.ucsd.edu/Marmara/marnaut_objectives.html
DE: 0408 Benthic processes (4804)
DE: 1050 Marine geochemistry (4835, 4845, 4850)
DE: 3004 Gas and hydrate systems
DE: 3080 Submergence instruments: ROV, AUV, submersibles
DE: 8106 Continental margins: transform
SC: Biogeosciences [B]
MN: 2007 Fall Meeting