Research on crustal structure and lithosphere property in the Okinawa area
冲绳海槽地区地壳结构与岩石层性质研究

A mass of geological, geophysical and geochemical data and information from the Okinawa Trough area are collected for comprehensive research in the study area from East China to Okinawa Trough and then to Ryukyu Island Arc region. According to the seismic tomography result (P and S wave) and the processing result of free air and Bouguer gravity anomaly and magnetic anomaly data in the study area, the comprehensive interpretation is carried out. The Moho depth distribution of the study area is obtained by the inversion calculation based on gravity data using the Harmonious Series method. The crust properties are analyzed. Meantime, some Cenozoic basalt data from Kuandian (NE China), Hannuoba (North China), Minxi (South China), Penghu Islands (Taiwan Strait), Okinawa Trough and Japan Island Arc regions are chosen to make the comparison research on element isotopes. The result indicates that the lithosphere thickness in the Okinawa Trough area has obviously decreased, where a Low velocity layer of upper mantle has reached the Moho interface and the metasometized asthenosphere has formed. The research result on element isotopes shows that the characteristic of the crust in the Okinawa Trough area is different from that in East China area and the Ryukyu Island Arc area. It is considered that the crust in the Okinawa Trough area belongs to the transition type, which is quite similar to the feature of the oceanic crust.