Continental crust formation by crustal delamination in subduction zones and complementary accumulation of the enriched mantle i component in the mantle

Abstract

A possible mechanism for continental crust formation, which includes slab-dehydration-induced mantle melting, basalt magma generation, remelting of the initial basaltic crust, followed by delamination of the residue, is examined by geochemical modeling of dehydration, partial melting, and fluid-solid reactions. The results suggest that such processes can explain the major and trace element compositions of the andesitic bulk continental crust. Isotopic modeling suggests that a pyroxenitic delaminated component formed at 3-4 Ga possesses Sr-Nd-Pb isotopic compositions typical of the EMI component, one of the enriched geochemical endmembers in the mantle. Continental crust formation and complementary accumulation of the EMI reservoir in the deep mantle may have taken place simultaneously in Archean subduction zones.