CONTINENTAL CRUST FORMATION AS CONSTRAINED BY MODERN ARC PROCESSES

The formation of continental crust remains an active area of research. In this presentation I review process that lead to the formation of continental crust in modern (Mesozoic) arcs and what we can learn from these studies for crust formation through time.

In the last decades the studies of exposed arc section have significantly further our understanding of the process that lead to Continental crust formation. Detailed estimates for the bulk composition of arc crust has revealed, in contrast to previous estimates, that the arc crust can be andesitic equally to the bulk continental crust. The process that lead to the formation of this arc crust mainly occur in the lower crust and are dominated by magmatic fractionation processes and metamorphic densification reaction that ultimately produce a lower crust more dense than the underlying mantle, which triggers delamination. In the Himalayan system intra-oceanic arc subduction was followed by continent-continent collision. The transition from subduction volcanism to post-collisional magmatism is associated with a pronounced shift in isotopes. The question is if such collisional event can be also seen in the Detrital zircon record.