The age and geochemistry of volcanic rocks of Dongtaishan Island in northern Fujian and their response to the subduction of the Paleo-Pacific Plate

Coastal islands of northern Fujian are mainly composed of volcanic rocks, which were produced by the paleo-Pacific oceanic subduction. These volcanic rocks provide critical information about the geodynamic evolution of paleo-Pacific Ocean. In this paper, the authors report new zircon U-Pb ages and whole-rock major and trace element geochemistry of the felsic rocks from the Dongtaishan Island of northern Fujian. Two geochronological samples yielded zircon ages of ~92 Ma and ~84 Ma, indicating that the volcanic rocks in Dongtaishan Island were formed in Late Cretaceous. Geochemically, all these felsic samples are calcalkaline, enriched in Rb, Ba, and depleted in Nb, Ta, Sr and Eu, suggesting a geochemical affinity with arc volcanic rocks. It is thus concluded that these volcanic rocks were derived by partial melting of ancient crustal metasedimentary sources and followed by fractional crystallization in the shallow magma chamber. These new data, combined with the oceanward migration of late Mesozoic magmatic activity, have led the authors to propose that the coastal islands of northern Fujian were triggered by the slab rollback during oceanic subduction of paleo-Pacific Ocean.