Tectonophysical Features of the Hydrothermal Fields in the Middle Okinawa Trough

Key words: 
• Okinawa Trough /
• hydrothermal fields /
• tectonophysical features

Abstract: Hvdrothermal activity is widely occurring along the active plate boundaries and intraplate volcanic centers which is exchanging heat and material between the lithosphere and the oceans.Okinawa Trough is an important part of Rvukv T-A-ha system汕ich is in the collision and suhduction zone between a oceanic block and continental block and is reported to he in the early stage of back-arc spreading with a rift structure and an embryonic marginal hasin} its origin and evolution may he one of the most interseting problems in geophysics and geology today.Hvdrothermal activity as a window and clue of studying the origin and evolution of Okinawa Trough has been explored through out the Trough by scientists all over the worlds.Sever- al hvdrothermal fields have been found in the middle part of Okinawa Trough.Tectonophysical features of topography heatflow distrihution, seismicitv and magnetic anomaly of three hvdrothermal fields including southwest Amami hvdrothermal field.Iheva deep hydrothermal field and Izena caldron hvdrothermal field in the middle Okinawa Trough were studied. The results show that all the hvdrothermal fields distribute in the central grahen and locate at the slope of caldera or of central ridge with high and vary heatflow distrihution, active seismic activities and fluctuating magnetic anomaly.It is found that the hvdrothermal fields have close relationship with tectonic zoon.In the area of Rvukvu T-A-Ba svstem, the upwelling of mantal materials beneath the trough due to the suhduction of Pacific Plate provides heat energy for the hvdrothermal activity.The faults formation in the process of trough expending provides space for the hydrothermal activity.