Abstract: How the continental crust is formed has long been a fundamental scientific question for the international academic community. Magmatic origin and density filtering of arcs at active continental margins are crucial to understanding formation and evolution of continental crust. The Cretaceous Cordilleran continental margin arc in North America may have formed through partial melting of lower crust and magma mixing associated with mantle-derived magmatic underplating, or two-stage compositional differentiation of mantle-derived initial basaltic magma. The vertical crustal compositional section that is dominantly granitic in the Nevada region of North America is most likely related to the delamination of eclogite facies residues or cumulates. It is currently not clear that why the Mesozoic Gangdese arc in southern Tibet is characterized by the occurrence of a large amount of hornblendites and the presence of an arc crust with basaltic andesitic composition in average at ca. 200 Ma and ca. 90 Ma. This problem may be resolved more or less by exploring the magmatic origin, vertical crustal compositional profile, and crustal formation mechanism of the Mesozoic Gangdese arc.

Key words: crustal formation, Mesozoic Gangdese arc, Cretaceous Cordilleran arc, southern Tibet, North America