Fluid chemistry and shallow gas hydrate dynamics at active pockmarks of the Vestnesa Ridge, west Svalbard margin

Hong, Wei-Li, Pape, Thomas, Schmidt, Christopher, Yao, Haoyi, Wallmann, Klaus, Plaza Faverola, Andreia, Rae, James William Buchanan, Lepland, Aivo, Bünz, Stefan and Bohrmann, Gerhard (Submitted) Fluid chemistry and shallow gas hydrate dynamics at active pockmarks of the Vestnesa Ridge, west Svalbard margin Journal of Geophysical Research - Solid Earth . DOI 10.1002/essoar.10503250.1.

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Abstract

Gas hydrate dynamics and the fluid flow systems from two active pockmarks along Vestnesa Ridge (offshore west Svalbard) were investigated through the pore fluid geochemistry obtained during the 2016 MARUM-MeBo 70 drilling cruise. Based on the pore water chloride concentration profiles from Lunde and Lomvi pockmarks, we estimated up to 47% pore space occupied by gas hydrate in the sediments shallower than 11.5 mbsf. These gas hydrates were formed during periods of gaseous methane seepage, but are now in a state of dynamic equilibrium sustained by a relatively low methane supply at present. We detect a saline formation pore fluid around nine meters below seafloor from one of the seepage sites in Lunde pockmark. This formation pore fluid has elevated dissolved chloride concentrations and B/Cl ratios, higher δO and δD isotopic signatures of water and lower δB signatures, which collectively hint to a high temperature modification of this fluid at great depths. By integrating our findings with the previous work from Vestnesa Ridge, we show that the variable fluid phases (gaseous vs. aqueous fluid) and migration pathways are controlled by the sediment properties, such as buried carbonate crusts, and the state of fluid reservoirs.

Document Type: Article
Additional Information: This preprint has been submitted to and is under consideration at Journal of Geophysical Research - Solid Earth. ESSOAr is a venue for early communication or feedback before peer review. Data may be preliminary.
Research affiliation: MARUM
OceanRep > GEOMAR > FB2 Marine Biogeochemistry > FB2-MG Marine Geosystems
OceanRep > GEOMAR > FB4 Dynamics of the Ocean Floor > FB4-MUHS
Refereed: Yes
DOI etc.: 10.1002/essoar.10503250.1
ISSN: 0148-0227
Related URLs:
Projects: The Ocean in the Earth System
Expeditions/Models:
Date Deposited: 01 Jul 2020 06:47
Last Modified: 01 Jul 2020 06:47
URI: http://eprints.uni-kiel.de/id/eprint/50007

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