Methane seep carbonates yield clumped isotope signatures out of equilibrium with formation temperatures

• Published in: Nature Communications
• Main Authors: Loyd, S. J., Sample, J., Tripati, R. E., Defliese, W. F., Brooks, K., Hovland, M., Torres, M., Marlow, J., Hancock, L. G., Martin, R., Lyons, T., Tripati, A. E.
• Other Authors: Department of Geological Sciences Fullerton, California State University Fullerton (CSU), Department of Earth, Planetary and Space Sciences Los Angeles (EPSS), University of California Los Angeles (UCLA), University of California-University of California, Northern Arizona University Flagstaff, Department of Atmospheric and Oceanic Sciences Los Angeles (AOS), Laboratoire des Sciences de l'Environnement Marin (LEMAR) (LEMAR), Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Centre National de la Recherche Scientifique (CNRS)-Université de Brest (UBO), Centre for Geobiology Bergen, University of Bergen (UiB), College of Earth, Ocean and Atmospheric Sciences Corvallis (CEOAS), Oregon State University (OSU), Division of Geological and Planetary Sciences Pasadena, California Institute of Technology (CALTECH), Department of Earth and Space Sciences Seattle, University of Washington Seattle, Department of Earth Sciences Riverside, University of California Riverside (UCR)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2016
• Subjects: ACL; sediments; authigenic carbonates; cascadia margin; cold-seeps; convergent margin; eel river-basin; hydrocarbon seeps; norwegian sea; offshore northern california; subduction zone; envir; geo; Norwegian Sea
• Online Access: https://doi.org/10.1038/ncomms12274; https://hal.archives-ouvertes.fr/hal-02566170/file/ncomms12274.pdf; https://hal.archives-ouvertes.fr/hal-02566170

WOS:000380842800001 International audience Methane cold seep systems typically exhibit extensive buildups of authigenic carbonate minerals, resulting from local increases in alkalinity driven by methane oxidation. Here, we demonstrate that modern seep authigenic carbonates exhibit anomalously low clumped isotope values (Delta(47)), as much as similar to 0.2 parts per thousand lower than expected values. In modern seeps, this range of disequilibrium translates into apparent temperatures that are always warmer than ambient temperatures, by up to 50 degrees C. We examine various mechanisms that may induce disequilibrium behaviour in modern seep carbonates, and suggest that the observed values result from several factors including kinetic isotopic effects during methane oxidation, mixing of inorganic carbon pools, pH effects and rapid precipitation. Ancient seep carbonates studied here also exhibit potential disequilibrium signals. Ultimately, these findings indicate the predominance of disequilibrium clumped isotope behaviour in modern cold seep carbonates that must be considered when characterizing environmental conditions in both modern and ancient cold seep settings.