Origin of the early Cretaceous Liucheng OIB-type dolerite sill in Zhejiang Province, coastal region of SE China: Implications for recycling of the Paleo-Pacific slab

Abstract Both early Cretaceous ocean island basalt (OIB)-type and subduction-related mafic magmatism occurred in coastal region of SE China. However, whether there existed a genetic relationship between the OIB-type magmatism and contemporary subduction of the Paleo-Pacific Ocean remains unclear. Here we present a comprehensive geochemical dataset of the Liucheng dolerite sill (∼ 108 Ma) from coastal SE China, with aims to investigate the possible genetic link between them. The dolerite displays OIB-like trace element features and contains moderately radiogenic Sr-Nd-Pb-Hf compositions and light Ca isotopes. The nearly identical Sr-Pb isotopes between plagioclase and bulk rock indicate a minor role of crustal assimilation during magmatic evolution. The remarkable positive Ba anomalies, similar Sr and Pb isotopic compositions to the contemporary arc-type mafic rocks and light Ca isotopes suggest a source metasomatized by recycled sediments. Additionally, the low La/Nb and Zr/Nb ratios indicate the involvement of an oceanic crust component that experienced dehydration and metamorphism to retain rutile. Further element-isotopic modeling suggests derivation of the parental magma from a depleted mantle that had been modified by melts from both the sediments and altered oceanic crust. Considering that SE China was mainly influenced by subduction of the Paleo-Pacific Ocean during late Mesozoic, the subducting Paleo-Pacific slab was therefore the most likely candidate for such recycled components. Interaction of the melts from the recycled oceanic slab with the asthenospheric mantle, possibly as a consequence of rollback and tearing of the subducting Paleo-Pacific slab, formed the OIB-type source of the Liucheng dolerite sill.