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

  1. Francis Albarèdea,2
  1. aEcole Normale Supérieure, Université Claude Bernard Lyon 1, and Centre National de la Recherche Scientifique, 69007 Lyon, France;
  2. bResearch Reactor Institute, Kyoto University, Osaka 590–0494, Japan;
  3. cNatural History Museum of Denmark, and Nordic Center for Earth Evolution, 1350 Copenhagen K, Denmark;
  4. dDepartment of Earth and Planetary Sciences, Washington University, and McDonnell Center for the Space Sciences, St. Louis, MO 63130
  1. Edited* by Mark H. Thiemens, University of California San Diego, La Jolla, CA, and approved September 15, 2011 (received for review May 20, 2011)

Abstract

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?°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.

Footnotes

  • ?1Present address: Géosciences Montpellier, 34095 Montpellier, France.

  • ?2To whom correspondence should be addressed. E-mail: albarede{at}ens-lyon.fr.
  • Author contributions: M.T.R. and F.A. designed research; M.-L.P., T.F., M.T.R., B.R., F.M., C.D., and F.A. performed research; B.R. contributed new reagents/analytic tools; M.-L.P., G.Q., T.F., M.T.R., F.M., and F.A. analyzed data; and M.-L.P. and G.Q. wrote the paper.

  • The authors declare no conflict of interest.

  • *This Direct Submission article had a prearranged editor.

  • This article contains supporting information online at www.danielhellerman.com/lookup/suppl/doi:10.1073/pnas.1108061108/-/DCSupplemental.

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