[MIS11-17] Overview of drilling active backarc basin, Okinawa Trough: ongoing rifting of Eurasian continental margin
キーワード：正断層、火成岩、流体、琉球弧、島弧、IODP
We introduce the outline of scientific drilling for the Okinawa Trough. The Ryukyu arc fringes Eurasian continental margin, and is subducted by the Philippine Sea plate at Ryukyu trench. The arc has an active backarc basin, called the Okinawa Trough. Although the Okinawa Trough has a thin crust (~10 km), no exposed oceanic basalts in axis of the Trough have been reported and the continental crust is thinning with the normal faulting (Arai et al. 2017, JGR, 122, 622–641; Nishizawa et al., 2019, EPS, 71:21). The backarc basin like the Okinawa Trough is rare in the world (another is the Bransfield Strait near Antarctica), and normal faulting in this region are key to understand the evolution of backarc basins. And, the Kuroshio warm current flows into the East China Sea from between the Taiwan and Ryukyu Arc, but it is unknown when it started. We are considering the ocean scientific drilling for the Okinawa Trough with three scientific targets: Q1. What are factors controlling opening of back-arc basins? Q2. How are fault-fluid-heat related in active rift zone before exposure of oceanic basalt? Q3. When did Kuroshio (warm current) flow into East China Sea?