Terra Nova, 00, 1–7, 2012


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.