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Authigenic carbonate mounds from active methane seeps on the southern Aquitaine Shelf (Bay of Biscay, France): evidence for anaerobic oxidation of biogenic methane and submarine groundwater discharge during formation ArchiMer
Pierre, Catherine; Demange, Jerome; Blanc-valleron, Marie-madeleine; Dupre, Stephanie.
The widespread methane emissions that were discovered in 2013 on the Aquitaine Shelf at water depth between 140 and 220 m are associated with authigenic carbonate crusts that cover meter-high subcircular reliefs of 10 to 100 m in diameter. These authigenic carbonates are primarily aragonite plus calcite and dolomite, which cement the fine- to medium-grained sandy sediment. The carbonate cement is often pierced by numerous circular cavities of 5 to 10 µm in diameter that are considered to be moulds of gas bubbles. Conversely, micron-sized cavities in the aragonite crystals are attributed to dissolution features, in relation to the production of CO2 during the aerobic oxidation of methane. The oxygen isotopic compositions of bulk carbonate (+1.7 to +3.7‰)...
Tipo: Text Palavras-chave: Aquitaine Shelf; Methane-derived authigenic carbonates; Oxygen isotopes; Carbon isotopes; Submarine groundwater discharge; Anaerobic oxidation of methane; Aerobic oxidation of methane.
Ano: 2017 URL: http://archimer.ifremer.fr/doc/00361/47209/47164.pdf
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Authigenic carbonates from methane seeps of the Congo deep-sea fan ArchiMer
Pierre, Catherine; Fouquet, Yves.
Submersible investigations with the ROV Victor 6000 of some pockmark structures on the seafloor of the Congo deep-sea fan have shown that they are active venting sites of methane-rich fluids, associated with abundant fauna and carbonate crusts. Moreover, methane hydrates have been observed both outcropping and deep in the sediments in the centre of the "Regab" giant pockmark. Authigenic carbonates, mostly calcite sometimes mixed with aragonite, are cementing the sedimentary matrix components and fauna; diatoms are abundant but only as moulds, indicating that biogenic silica dissolution occurred in situ synchronous with carbonate precipitation. The occurrence of diagenetic barite and pyrite in some carbonate crusts demonstrates that they can be formed...
Tipo: Text Palavras-chave: Oxygen isotopes; Carbon isotopes; Congo deep sea fan; Gas hydrate; Methane seep; Authigenic carbonate.
Ano: 2007 URL: http://archimer.ifremer.fr/doc/2007/publication-2608.pdf
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Gaining insight into Clipperton's lagoon hydrology using tritium ArchiMer
Jean-baptiste, Philippe; Fourre, Elise; Charlou, Jean-luc; Donval, Jean-pierre; Correge, Thierry.
Historical descriptions of the Clipperton lagoon appear to converge on the fact that it became isolated from the surrounding ocean around 1858. Since then, because of the high precipitation rate which largely exceeds evaporation in this region of the eastern tropical Pacific, a brackish lens has formed on top of the saline oceanic waters. In 1980, literature data show that the thickness of this water body was reaching 14 m. During the 2005 Etienne's Clipperton expedition, we collected lagoon water on two vertical profiles. Salinity, delta O-18 and tritium analyses were performed on these samples with the objective of gaining further insight into the lagoon hydrology and age of the deep waters. The upper 15 m were characterized by low salinities (5.4 +/-...
Tipo: Text Palavras-chave: Oxygen isotopes; Tritium; Enclosed lagoon hydrology; Clipperton atoll.
Ano: 2009 URL: http://archimer.ifremer.fr/doc/2009/publication-6457.pdf
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