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In situ measurements of oxygen isotopic composition in deep-sea coral, Lophelia pertusa: Re-examination of the current geochemical models of biomineralization |
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| Authors: | Claire Rollion-Bard Dominique Blamart Yannicke Dauphin |
| Institution: | a Nancy-Université, Centre de Recherches Pétrographiques et Géochimiques, CNRS-UPR 2300, BP 20, 54501 Vandoeuvre-lès-Nancy Cédex, France b Laboratoire des Sciences du Climat et de l’Environnement, avenue de la Terrasse, 91198 Gif-sur-Yvette Cédex, France c UMR IDES, Interactions et Dynamique des Environnements de Surface, Bat. 504, Université Paris XI, 91405 Orsay Cédex, France |
| Abstract: | We present ion microprobe measurements of oxygen isotopic compositions in the deep-sea coral Lophelia pertusa. Compared to bulk skeletal aragonite fibres, the EMZ (early mineralization zone), near the inside of the calyx, was systematically depleted in 18O. Rayleigh fractionation from a semi-closed fluid reservoir does not explain this and other geochemical differences. Furthermore, pH values estimated from skeletal δ11B data are inconsistent with the idea that EMZ (or centres of calcification) 18O depletion reflects a more alkaline calcification environment. Our data, combined with microstructural and geochemical observations, indicate that the aragonitic fibres and EMZ are formed by a compartmentalized mineralization calicoblastic ectoderm, which exerts strong biological control on the composition of the skeleton. Hence, we propose a new model whereby amorphous calcium carbonates (ACC) are precursors to the EMZ, whereas the fibre precipitation is probably governed by kinetic processes. |
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