Two Mesozoic volcanic activities in Fujian Province, China: constraints on the transformation of tectonic domain in Southeastern China

Abstract

Two representative geologic sections of the late Mesozoic “Nanyuan Formation” volcanic rocks in eastern Fujian Province have been dated by zircon SHRIMP U-Pb tecnonique. Two volcanic activities have been identified, i.e. the earlier at 162-150 Ma and the latter at 142-130 Ma. Basaltic rocks of the earlier period have geochemical features similar to those of OIB with significant crustal contamination and fractional crystalization of olivine and clinopyroxene, while the counterpart of the latter period are rich in Al, Fe, LILE and LREE and depleted in HFSE. It seems that the two volcanic activities should not be grouped into the same Formation and the magmas may have been generated in different tectonic settings. The above data may indicate a transformation of Mesozoic tectonic domain in Southeastern China in a period of 150-142 Ma. It is suggested that the earlier volcanic activity was generated by local extension resulted from the combining action of Tethyan tectonic dynamic system and Paleo-Pacific tectonic system whereas the latter was attributed to the regional extension induced by high-angle subduction of the Paleo-Pacific plate.