Research on Crust Structure and Lithosphere Property Beneath the Okinawa Through Area

Abstract

AbstractA 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 through Okinawa Trough to the Ryukyu Island Arc region. According to the seismic tomography results (P and S wave) and the processing results of free‐air and Bouguer gravity and magnetic 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 (Northeast 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 indicateic that the lithospheric thickness in the Okinawa Trough area has obviously decreased, where a low ‐velocity layer of the 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 below the Okinawa Trough area is different from that beneath East China area and the Ryukyu Island Arc area. It is considered that the crust under the Okinawa Trough area belongs to the transition type, which has features quite similar to the those of the oceanic crust.