Petrogenesis of Cretaceous volcanic rocks from islands off Fujian Province, East China Sea, and implications for episodic slab rollback of the paleo-Pacific plate

Abstract

This study constrains the petrogenesis and regional tectono-magmatic evolution of volcanic rocks from Fuying and Dayushan Islands, northeast Fujian Province, southeast (SE) China, using petrological, zircon U–Pb geochronological, whole-rock geochemical and Sr–Nd–Pb isotopic data. New zircon U–Pb data show that volcanism occurred between 118 and 99 Ma. The volcanic rocks are dominantly alkalic to alkali-calcic, ferroan, and peraluminous in composition, and are characterized by strongly fractionated LREE and HREE, with depletion in Nb, Ta, Sr, and Eu. These features, together with their relatively enriched Sr–Nd–Pb isotopic compositions, imply that the volcanic rocks were derived from ancient lower crust and experienced extensive assimilation and fractional crystallization in the shallow crust. Taking into account previously published data, we conclude that the Fuying and Dayushan volcanic rocks were generated in a back-arc extensional setting in response to episodic slab rollback after flat subduction of the paleo-Pacific plate during the Cretaceous.