Isotopic Composition of Gases and Interstitial Fluids in Sediment of the Vøring Plateau, ODP Leg 104, Site 644

Vuletich, A.K.; Threlkeld, Charles N.; Claypool, George E.

doi:10.2973/odp.proc.sr.104.199.1989

Cited by 6 publications

(3 citation statements)

References 6 publications

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“…At the depth where the dissolved sulfate supply is exhausted, the DIC δ 13 C has a minimum δ 13 C value then reverses and becomes heavier because carbon that is ~70‰ lighter than the DIC pool is being removed to make methane at a faster rate than DIC of -20‰ is being added (Claypool and Kaplan, 1974). If methane were being oxidized at the base of the sulfate reduction zone, the DIC δ 13 C values would be much more negative (from -60‰ to -30‰) as observed in sediments at other locations where AMO is apparently taking place (Claypool and Threlkeld, 1983;Claypool et al, 1985Claypool et al, , 2003Vuletich et al, 1989;Blair and Aller, 1995;Burns, 1998;Borowski et al, 2000).…”

Section: Ge Claypool Et Al Microbial Methane Generation and Gas Trmentioning

confidence: 95%

Microbial Methane Generation and Gas Transport in Shallow Sediments of an Accretionary Complex, Southern Hydrate Ridge (ODP Leg 204), offshore Oregon, USA

Claypool¹,

Milkov²,

Lee³

et al. 2006

Proceedings of the Ocean Drilling Program, 199 Scientific Results

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Sediments at the southern summit of Hydrate Ridge display two distinct modes of gas hydrate occurrence. The dominant mode is associated with active venting of gas exsolved from the accretionary prism and leads to high concentrations (15%-40% of pore space) of gas hydrate in seafloor or near-surface sediments at and around the topographic summit of southern Hydrate Ridge. These near-surface gas hydrates are mainly composed of previously buried microbial methane but also contain a significant (10%-15%) component of thermogenic hydrocarbons and are overprinted with microbial methane currently being generated in shallow sediments. Focused migration pathways with high gas saturation (>65%) abutting the base of gas hydrate stability create phase equilibrium conditions that permit the flow of a gas phase through the gas hydrate stability zone. Gas seepage at the summit supports rapid growth of gas hydrates and vigorous anaerobic methane oxidation. The other mode of gas hydrate occurs in slope basins and on the saddle north of the southern summit and consists of lower average concentrations (0.5%-5%) at greater depths (30-200 meters below seafloor [mbsf]) resulting from the buildup of in situ-generated dissolved micro

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Section: Ge Claypool Et Al Microbial Methane Generation and Gas Trmentioning

confidence: 95%

Microbial Methane Generation and Gas Transport in Shallow Sediments of an Accretionary Complex, Southern Hydrate Ridge (ODP Leg 204), offshore Oregon, USA

Claypool¹,

Milkov²,

Lee³

et al. 2006

Proceedings of the Ocean Drilling Program, 199 Scientific Results

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“…1998), 3–6 mbsf along the Chilean continental margin (Treude et al. 2005), 6–22 mbsf in the Norwegian Sea (Vuletich et al. 1989), 3–13 mbsf on the Nankai Trough (Gamo et al.…”

Section: Discussionmentioning

confidence: 99%

“…Below, sulphate decreases rapidly and linearly to the analytical detection limit of 2.89 mM at 74 mbsf (U1322) and 94 mbsf (U1324), thus defining the depth of the sulphate-methane transition zone at both sites. Deep sulphate-methane transition zones have been documented in other basins: 3.5-10 mbsf offshore Namibia (Niewohner et al 1998), 3-6 mbsf along the Chilean continental margin (Treude et al 2005), 6-22 mbsf in the Norwegian Sea (Vuletich et al 1989), 3-13 mbsf on the Nankai Trough (Gamo et al 1993), 35-85 mbsf on the Peru Margin (Biddle et al 2005), 20 mbsf on the Blake Ridge (Borowski et al 2000), 5-54 mbsf in the western Gulf of Mexico (Presley et al 1973) and 3-12 mbsf in the northern Gulf of Mexico (Paull et al 2005). The deepest sulphate-methane transition zone has been found in the Sulu and Celebes Seas at 172 mbsf (Von Breymann et al 1991).…”

Section: Downward Seawater Flow Evidenced From Sulphate Profilesmentioning

confidence: 99%

Geophysical and geochemical evidence of large scale fluid flow within shallow sediments in the eastern Gulf of Mexico, offshore Louisiana

et al. 2010

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We analyse the fluid flow regime within sediments on the Eastern levee of the modern Mississippi Canyon using 3D seismic data and downhole logging data acquired at Sites U1322 and U1324 during the 2005 Integrated Ocean Drilling Program (IODP) Expedition 308 in the Gulf of Mexico. Sulphate and methane concentrations in pore water show that sulphate-methane transition zone, at 74 and 94 m below seafloor, are amongst the deepest ever found in a sedimentary basin. This is in part due to a basinward fluid flow in a buried turbiditic channel (Blue Unit, 1000 mbsf), which separates sedimentary compartments located below and above this unit, preventing normal upward methane flux to the seafloor. Overpressure in the lower compartment leads to episodic and focused fluid migration through deep conduits that bypass the upper compartment, forming mud volcanoes at the seabed. This may also favour seawater circulation and we interpret the deep sulphate-methane transition zones as a result of high downward sulphate fluxes coming from seawater that are about 5-10 times above those measured in other basins. The results show that geochemical reactions within shallow sediments are dominated by seawater downwelling in the Mars-Ursa basin, compared to other basins in which the upward fluid flux is controlling methane-related reactions. This has implications for the occurrence of gas hydrates in the subsurface and is evidence of the active connection between buried sediments and the water column.

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The geochemical characteristics of the hydrate-bound gases from the Nyegga pockmark field, Norwegian Sea

Vaular

Barth

Haflidason

2010

Organic Geochemistry

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Isotopic Composition of Gases and Interstitial Fluids in Sediment of the Vøring Plateau, ODP Leg 104, Site 644

Cited by 6 publications

References 6 publications

Microbial Methane Generation and Gas Transport in Shallow Sediments of an Accretionary Complex, Southern Hydrate Ridge (ODP Leg 204), offshore Oregon, USA

Microbial Methane Generation and Gas Transport in Shallow Sediments of an Accretionary Complex, Southern Hydrate Ridge (ODP Leg 204), offshore Oregon, USA

Geophysical and geochemical evidence of large scale fluid flow within shallow sediments in the eastern Gulf of Mexico, offshore Louisiana

The geochemical characteristics of the hydrate-bound gases from the Nyegga pockmark field, Norwegian Sea

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