Japan Geoscience Union Meeting 2015

Presentation information

International Session (Oral)

Symbol S (Solid Earth Sciences) » S-CG Complex & General

[S-CG14] Mixed volatiles in subduction zones; Physical and chemical properties and processes

Mon. May 25, 2015 4:15 PM - 6:00 PM 303 (3F)

Convener:*Bjorn Mysen(Geophysical Laboratory, Carnegie Inst. Washington), Eiji Ohtani(Department of Earth and Planetary Materials Science, Graduate School of Science, Tohoku University), Dapeng Zhao(Department of Geophysics, Tohoku University), Chair:Eiji Ohtani(Department of Earth and Planetary Materials Science, Graduate School of Science, Tohoku University)

4:30 PM - 4:45 PM

[SCG14-10] Deep slab structure, dehydration and the Changbai intraplate volcanism

Chuanxu Chen1, *Dapeng ZHAO1, You Tian2, Jianshe Lei3, Akira HASEGAWA1, Shiguo Wu4, Jung-Ho Park5, Ik-Bum Kang5 (1.Tohoku University, Department of Geophysics, 2.Jilin University, 3.China Earthquake Administration, 4.Chinese Academy of Sciences, 5.Korea Institute of Geoscience and Mineral Resources)

Keywords:Northeast Asia, Changbai volcano, Pacific plate, slab dehydration, deep earthquakes

We obtained a new 3-D P-wave tomography model down to 800 km depth beneath NE Asia by assembling a large number of arrival-time data of local, regional and teleseismic events recorded by ~2500 seismic stations in Japan, China and South Korea. The data from a portable seismic network (NECESSArray) in NE China are also collected and used. Our updated model shows a sharper image of the volcanism-related asthenospheric upwelling and the stagnant Pacific slab in the mantle transition zone (MTZ) beneath the Changbai intraplate volcano. The main findings are summarized as follow.
(1) Relative travel-time residuals of teleseismic events alone are not able to recover the flat stagnant slab in the MTZ, and a slab gap in the MTZ beneath the Changbai volcano imaged by relative travel-time tomography is an artifact.
(2) The low-velocity anomaly in the big mantle wedge (BMW) becomes the most prominent near the hinge of the stagnant slab, which is located slightly east of the Changbai volcano and may reflect focused hot upwelling in the BMW. This low-velocity feature coincides with the depression of both 410-km and 660-km discontinuities and a cluster of very deep earthquakes (> 500 km depth) in the Pacific slab.
(3) Besides the deep dehydration of hydrous minerals within the stagnant slab, additional fluids released through deep-earthquake faulting and a stronger mantle flow circulation near the hinge of the Pacific slab have made Changbai the largest and most active intraplate volcano in NE Asia.
(4) The BMW origin of the Changbai volcanism agrees well with other geophysical, geochemical and numerical-modeling studies.