JpGU-AGU Joint Meeting 2020

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[E] Oral

M (Multidisciplinary and Interdisciplinary) » M-IS Intersection

[M-IS11] Expedition Earth: discovering our planet's past and future through scientific drilling

convener:Junichiro Kuroda(Department of Ocean Floor Geoscience, Atmosphere and Ocean Research Institute, the University of Tokyo), Katsuyoshi Michibayashi(Department of Earth and Planetary Sciences, Nagoya University), Kohtaro Ujiie(Graduate School of Life and Environmental Sciences, University of Tsukuba), Clive Robert Neal(University of Notre Dame)

[MIS11-17] Overview of drilling active backarc basin, Okinawa Trough: ongoing rifting of Eurasian continental margin

*Makoto Otsubo1 (1.Geological Survey of Japan, Research Institute of Earthquake and Volcano Geology)

Keywords:Normal fault, Volcanics, Fluid, Ryukyu arc, Island arc, 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?