caa a22 4500 463216202 CHVBK 20180405153157.0 cr unu---uuuuu 170326e20070601xx s 000 0 eng 10.1007/s00367-007-0081-3 doi (NATIONALLICENCE)springer-10.1007/s00367-007-0081-3 Authigenic carbonates from methane seeps of the Congo deep-sea fan [Elektronische Daten] [Catherine Pierre, Yves Fouquet] 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 either within the sulphate/methane transition zone or deeper in sulphate-depleted sediments. The oxygen isotopic compositions of the diagenetic carbonates (3.17-6.01‰ V-PDB) indicate that precipitation occurred with bottom seawater mixed with a variable contribution of water from gas hydrate decomposition. The very low carbon isotopic compositions of the diagenetic carbonates (−57.1 to −27.75‰ V-PDB) demonstrate that carbon derives mostly from the microbial oxidation of methane. Springer-Verlag, 2007 Pierre Catherine LOCEAN, UPMC (UMR 7159), 4 Place Jussieu, 75252, Paris Cedex 05, France aut Fouquet Yves Géosciences Marines, IFREMER, Technopôle de l'Iroise, 29280, Plouzané Cedex, France aut Geo-Marine Letters Springer-Verlag 27/2-4(2007-06-01), 249-257 0276-0460 27:2-4<249 2007 27 367 https://doi.org/10.1007/s00367-007-0081-3 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/s00367-007-0081-3 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Pierre Catherine LOCEAN, UPMC (UMR 7159), 4 Place Jussieu, 75252, Paris Cedex 05, France aut NATIONALLICENCE 700 1- Fouquet Yves Géosciences Marines, IFREMER, Technopôle de l'Iroise, 29280, Plouzané Cedex, France aut NATIONALLICENCE 773 0- Geo-Marine Letters Springer-Verlag 27/2-4(2007-06-01), 249-257 0276-0460 27:2-4<249 2007 27 367 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer