The building blocks of continental crust: Evidence for a major change in the tectonic setting of continental growth at the end of the Archean

摘要: Abstract Oceanic arcs are commonly cited as primary building blocks of continents, yet modern oceanic mostly subducted. Also, lithosphere buoyancy considerations show that (even those with a felsic component) should readily subduct. With the exception Arabian–Nubian orogen, terranes in post-Archean accretionary orogens comprise  50%) produced continental arcs. Felsic igneous rocks depleted incompatible elements compared to average crust and from They have lower Th/Yb, Nb/Yb, Sr/Y La/Yb ratios, reflecting shallow mantle sources which garnet did not exist restite during melting. The bottom line these geochemical differences is does begin life On other hand, remarkable similarity element distributions granitoids volcanics consistent being During Archean, however, may been thicker due higher degrees melting mantle, would be more buoyant. These accreted each plateaus, process eventually led production Archean crust. After was thinner cooling less melt at ocean ridges, hence, subductable. Widespread propagation plate tectonics late only rapid crust, but change site plateaus primarily thereafter.