Distribution and abundance of gas hydrates in near-surface deposits of the Håkon Mosby Mud Volcano, SW Barents Sea.

Pape, Thomas, Feseker, Tomas, Kasten, Sabine, Fischer, David and Bohrmann, Gerhard (2011) Distribution and abundance of gas hydrates in near-surface deposits of the Håkon Mosby Mud Volcano, SW Barents Sea. Open Access Geochemistry, Geophysics, Geosystems, 12 (9). Q09009. DOI 10.1029/2011GC003575.

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Abstract

The occurrence of gas hydrates at submarine mud volcanoes (MVs) located within the gas hydrate stability zone (GHSZ) is controlled by upward fluid and heat flux associated with MV activity. Determining the spatial distribution of gas hydrates at MVs is crucial to evaluate their sensitivity to known episodic changes in volcanic activity. We determined the hydrocarbon inventory and spatial distribution of hydrates at an individual MV structure. The Hakon Mosby Mud Volcano (HMMV), located at 1,250 m water depth on the Barents Sea slope, was investigated by combined pressure core sampling, heat flow measurements, and pore water chemical analysis. Quantitative pressure core degassing revealed gas-sediment ratios between 3.1 and 25.7, corresponding to hydrate concentrations of up to 21.3% of the pore volume. Hydrocarbon compositions and physicochemical conditions imply that gas hydrates incipiently crystallize as structure I hydrate, with a dissociation temperature of around 13.8 degrees C at this water depth. Based on numerous in situ measurements of the geothermal gradient in the seabed, pore water sulfate profiles and microbathymetric data, we show that the thickness of the GHSZ increases from less than 1 m at the warm center to around 47 m in the outer parts of the HMMV. We estimate the total mass of hydrate-bound methane stored at the HMMV to be about 102.5 kt, of which 2.8 kt are located within the morphological Unit I around the center and thus are likely to be dissociated in the course of a large eruption.

Document Type: Article
Keywords: Meeresgeologie; Dynamic Autoclave Piston Corer; Hakon Mosby Mud Volcano; gas hydrates; in situ temperature; methane; pore water sulfate; EASTERN MEDITERRANEAN SEA; GLOBAL METHANE EMISSION; GULF-OF-MEXICO; BLACK-SEA; PORE-WATER; FLUID-FLOW; TEMPERATURE-MEASUREMENTS; GEOCHEMICAL CONSTRAINTS; HYDROCARBON GASES; MARINE-SEDIMENTS
Research affiliation: MARUM
OceanRep > GEOMAR > FB2 Marine Biogeochemistry > FB2-MG Marine Geosystems
AWI
Refereed: Yes
Open Access Journal?: No
DOI etc.: 10.1029/2011GC003575
ISSN: 1525-2027
Projects: HERMES, GEOTECHNOLOGIEN, Excellence Cluster 'The Ocean in the Earth System'
Expeditions/Models/Experiments:
Date Deposited: 11 Jan 2012 14:12
Last Modified: 08 Jul 2019 13:13
URI: http://oceanrep.geomar.de/id/eprint/13403

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