Physical and chemical characterization of gas hydrates and associated methane plumes in the Congo–Angola Basin

Charlou, J. L.; Donval, Jean-Pierre; Fouquet, Yves; Ondréas, Hélène; Knœry, Joël; Cochonat, Pierre; Levaché, D.; Poirier, Yannick; Jean‐Baptiste, Philippe; Fourré, Élise; Chazallon, Bertrand

doi:10.1016/j.chemgeo.2003.12.033

Cited by 122 publications

(90 citation statements)

References 64 publications

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“…After recovery, the PEGAZ sampler was connected to a gas transfer system on board for subsampling [19]. The collected gases were stored at ∼3 bars in 12 mL preevacuated vials from Labco5.…”

Section: Methodsmentioning

confidence: 99%

“…Any seep may be composed of a single gas stream or several ones very close to each other such that they clearly define its perimeter. Submarine seeps, at cold seeps, occur worldwide along the continental margins and are usually related to geological structures with either positive reliefs such as submarine pingoes [1][2][3][4][5][6][7], carbonate concretions and pavements [8][9][10][11], and mud volcanoes [9,[12][13][14][15][16][17][18] or negative reliefs like pockmarks [13,[19][20][21][22][23]. They also occur in seafloor-reaching fault areas at tectonically active regions without being associated with a specific relief [24][25][26][27][28].…”

Section: Introductionmentioning

confidence: 99%

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Gas Seepage along the Edge of the Aquitaine Shelf (France): Origin and Local Fluxes

et al. 2017

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During the scientific expedition GAZCOGNE2 at the Bay of Biscay nine gas seeps were sampled for the first time and their flux was measured using an in situ pressure-preservation sampler (PEGAZ, © IFREMER). Overall, three sites were investigated to determine the nature and the origin of the gases bubbling at the seafloor and forming acoustic plumes into the water column, as this was the question raised from the first geologic study of the area. This has guided our study and accordingly corresponds to the main purpose of the present article. Thus, the molecular and isotopic ( D and 13 C) analyses revealed that the gas seeps were primarily composed of methane. Both methane and ethane are of microbial origin, and the former has been generated by microbial reduction of carbon dioxide. Heavier hydrocarbons accounted for less than 0.06% mol of the total amount. Despite the microbial origin of methane, the samples exhibit subtle differences with respect to the 13 C CH 4 values, which varied between −72.7 and −66.1‰. It has been suggested that such a discrepancy was predominantly governed by the occurrence of anaerobic methane oxidation. The PEGAZ sampler also enabled us to estimate the local gas fluxes from the sampled streams. The resulting values are extremely heterogeneous between seeps, ranging from 35 to 368 mLn⋅min −1 . Assuming a steady discharge, the mean calculated methane emission for the nine seeps is of 38 kmol⋅yr −1 . Considering the extent of the seep area, this very local estimate suggests that the Aquitaine Shelf is a very appropriate place to study methane discharge and its fate on continental shelves.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Gas Seepage along the Edge of the Aquitaine Shelf (France): Origin and Local Fluxes

et al. 2017

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“…The gases were extracted from the hydrate samples using a gas extraction set-up (Charlou et al, 2004), and the hydrate water was collected and stored in another 20 mL glass tube. The resulting gases were also transferred into 10 mL glass tubes at a pressure ranging between 2 and 3 bars.…”

Section: Wwwintechopencommentioning

confidence: 99%

Geochemical Dynamics of the Natural-Gas Hydrate System in the Sea of Marmara, Offshore Turkey

Ruffine¹,

Fandiño²,

Étoubleau³

et al. 2012

Advances in Natural Gas Technology

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“…Iron sometimes plays a critical role in biogeochemical processes at seeps, leading occasionally to the formation of orange iron-oxidizing microbial mats on the seafloor (Omoregie et al, 2008). High Fe concentrations are frequently found in methane plumes Charlou et al, 2004;Lemaitre et al, 2014) and this process could lead to the precipitation of Feoxyhydroxide and/or nanosulfide phases as well (Lemaitre et al, 2014). So far, Fe geochemistry has not been used to trace the variability of redox conditions and the formation environment of authigenic minerals at seeps.…”

Section: Introductionmentioning

confidence: 99%

Using iron speciation in authigenic carbonates from hydrocarbon seeps to trace variable redox conditions

Dong

Chen

et al. 2015

Marine and Petroleum Geology

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Physical and chemical characterization of gas hydrates and associated methane plumes in the Congo–Angola Basin

Cited by 122 publications

References 64 publications

Gas Seepage along the Edge of the Aquitaine Shelf (France): Origin and Local Fluxes

Gas Seepage along the Edge of the Aquitaine Shelf (France): Origin and Local Fluxes

Geochemical Dynamics of the Natural-Gas Hydrate System in the Sea of Marmara, Offshore Turkey

Using iron speciation in authigenic carbonates from hydrocarbon seeps to trace variable redox conditions

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