Sr-Nd isotopic characteristics of the Mesozoic magmatism in the Taihang-Yanshan orogen, North China craton, and implications for Archaean lithosphere thinning

Voluminous felsic rocks (mainly monzonitic) and coeval mafic rocks (mainly monzogabbro-diorites) were emplaced in the Taihang-Yanshan orogen of eastern North China craton in Mesozoic time. The monzogabbro-diorites have high Sr (mostly > 1300 ppm) and low epsilon(Nd)(t) values (-9.5 to -15), indicating a long-term incompatible element enriched subcontinental lithospheric mantle source for their genesis. The monzonitic rocks show elemental geochemistry (e.g. high Sr, and REE patterns) and isotopic compositions similar to the monzogabbro-diorites, which leaves little doubt that the two rock suites share a similar origin. These mafic and felsic rocks thus represent a significant addition of juvenile continental crust from an enriched lithospheric mantle source in the Mesozoic, and their generation via melting of enriched portions of the subcontinental lithospheric mantle is probably an important mechanism responsible for the lithosphere thinning beneath eastern North China craton.