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Were ancient granitoid compositions influenced by contemporaneous atmospheric and hydrosphere oxidation states?

Authors

  • Oliver Jagoutz

    1. Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts, MA 02139-4307, USA
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Dr. Oliver Jagoutz, Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge, Massachusetts, MA 02139-4307, United States. Tel.: 001 617 324 5514; e-mail: jagoutz@mit.edu

Abstract

Terra Nova, 00, 1–7, 2012

Abstract

A feedback loop between subducted oceanic plate composition, subduction zone processes, arc magma chemistry, and the newly formed continental crust composition links to atmospheric and hydrosphere oxidation conditions through the low temperature weathering mechanisms of seafloor basalts. Sea-floor weathering and the Na/K of the altered oceanic crust strongly depends on f(O2) conditions during alteration, that changed with earth history. The rise of oxygen at ∼2600–2400 Ma triggered associated changes in f(O2) seafloor alteration conditions providing a possible explanation for the observed change from the Na-rich tonalite-trondhjemite-granodiorite (TTG) rocks in the Archean to the K-rich granodiorite-granite (GG) granitoids in post-Archean times.

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