The Mg isotopic systematics of granitoids in continental arcs and implications for the role of chemical weathering in crust formation.

ABSTRACT: Continental crust is too Si-rich and Mg-poor to derive directly from mantle melting, which generates basaltic rather than felsic magmas. Converting basalt to more felsic compositions requires a second step involving Mg loss, which is thought to be dominated by internal igneous differentiation. However, igneous differentiation alone may not be able to generate granites, the most silicic endmember making up the upper continental crust. Here, we show that granites from the eastern Peninsular Ranges Batholith (PRB) in southern California are isotopically heavy in Mg compared with PRB granodiorites and canonical mantle. Specifically, Mg isotopes correlate positively with Si content and O, Sr, and Pb isotopes and negatively with Mg content. The elevated Sr and Pb isotopes require that a componen

SUBMITTER: Shen B 

PROVIDER: S-EPMC2791568 | biostudies-literature | 2009 Dec

REPOSITORIES: biostudies-literature