Onset of subduction and the genesis of the continental crust in the earliest Earth | INSTITUT DE PHYSIQUE DU GLOBE DE PARIS

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  Onset of subduction and the genesis of the continental crust in the earliest Earth

Wednesday 10 December 2014
Séminaires Géochimie
Tracy Rushmer
(Macquarie University)
Extrait: 

One of the most popular theories of early continental crust development is that an older basaltic protocrust was partially re-melted to produce felsic magmas plus a residue of garnet + pyroxene + rutile, with the felsic melts are now represented by the TTG granitoids that dominate most surviving Archaean terrains. In this study we present new experimental evidence that is consistent with this model, but which also indicates that TTG magma formation was probably a more complex process than has just been described. These greenstones have compositional affinities with modern subduction zone magmas. Thus, arc-like mafic rocks appear to have been selectively involved in TTG formation, implying the involvement of crustal recycling in TTG genesis and plate interaction (subduction?) very early in Earth’s history.