Early Archean serpentine mud volcanoes at Isua, Greenland, as a niche for early life

• Published in: Proceedings of the National Academy of Sciences
• Main Authors: Pons, Marie-Laure, Quitté, Ghylaine, Fujii, Toshiyuki, Rosing, Minik T., Reynard, Bruno, Moynier, Frédéric, Douchet, Chantal, Albarède, Francis
• Other Authors: Laboratoire de Géologie de Lyon - Terre, Planètes, Environnement Lyon (LGL-TPE), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-École normale supérieure - Lyon (ENS Lyon), Research Reactor Institute, Kyoto University Kyoto, Natural History Museum of Denmark, Faculty of Science Copenhagen, University of Copenhagen = Københavns Universitet (KU)-University of Copenhagen = Københavns Universitet (KU), Nordic Centre of Earth Evolution (NORDCEE), University of Copenhagen = Københavns Universitet (KU), Department of Earth and Planetary Sciences St Louis, Washington University in Saint Louis (WUSTL), Géosciences Montpellier, Université des Antilles et de la Guyane (UAG)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), National Science Foundation, INSU : Institut National des Sciences de l'Univers; Carslberg Foundation, Danish National Research Foundation, ENS LYON / Ecole Normale Superieure de Lyon
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2011
• Subjects: hydrothermal fluids; serpentinization; origin of life; subduction zone; [SDU.STU]Sciences of the Universe [physics]/Earth Sciences; Greenland
• Online Access: https://hal-insu.archives-ouvertes.fr/insu-00674714; https://doi.org/10.1073/pnas.1108061108

International audience The Isua Supracrustal Belt, Greenland, of Early Archean age (3.81-3.70 Ga) represents the oldest crustal segment on Earth. Its complex lithology comprises an ophiolite-like unit and volcanic rocks reminiscent of boninites, which tie Isua supracrustals to an island arc environment. We here present zinc (Zn) isotope compositions measured on serpentinites and other rocks from the Isua supracrustal sequence and on serpentinites from modern ophiolites, midocean ridges, and the Mariana forearc. In stark contrast to modern midocean ridge and ophiolite serpentinites, Zn in Isua and Mariana serpentinites is markedly depleted in heavy isotopes with respect to the igneous average. Based on recent results of Zn isotope fractionation between coexisting species in solution, the Isua serpentinites were permeated by carbonate- rich, high- pH hydrothermal solutions at medium temperature (100-300 degrees C). Zinc isotopes therefore stand out as a pH meter for fossil hydrothermal solutions. The geochemical features of the Isua fluids resemble the interstitial fluids sampled in the mud volcano serpentinites of the Mariana forearc. The reduced character and the high pH inferred for these fluids make Archean serpentine mud volcanoes a particularly favorable setting for the early stabilization of amino acids.