Japan Geoscience Union Meeting 2015

Presentation information


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

[S-CG60] Geofluids and dynamics in subduction zones

Mon. May 25, 2015 6:15 PM - 7:30 PM Convention Hall (2F)

Convener:*Ikuo Katayama(Department of Earth and Planetary Systems Science, Hiroshima University), Atsushi Okamoto(Graduate School of Environmental Studies), Tatsuhiko Kawamoto(Institute for Geothermal Sciences, Graduate School of Science, Kyoto University)

6:15 PM - 7:30 PM

[SCG60-P04] Geofluid migration process inferred from a 3-D electrical conductivity model beneath Tohoku district.

*Masahiro ICHIKI1, Yasuo OGAWA2, Toshiki KAIDA1, Tomotsugu DEMACHI1, Satoshi HIRAHARA1, Yoshimori HONKURA2, Wataru KANDA2, Toshio KONO1, Takao KOYAMA3, Masaki MATSUSHIMA2, Takashi NAKAYAMA1, Syuichi SUZUKI1, Hiroaki TOH4, Makoto UYESHIMA3 (1.Graduate School of Science, Tohoku University, 2.Volcanic Fluid Research Center, Tokyo Institute of Technology, 3.Earthquake Research Institute, The University of Tokyo, 4.Graduate School of Science, Kyoto University)

We carried out long-period MT observation using the state-of-the-art equipments. The MT impeadance responses were inverted into 3-D electrical conductivity model using WSINV3D (Siripunvaraporn et al, 2005). The 3-D model delineates vertical continuous conductive zone from subducting Pacifc plate surface to lower crust below Ou backbone range. The conductive body indicates saline fluids and/or melt pathway from the subducting slab surface to lower crust. The resistivity of the lower crust conductor is 1 Ωm or more conductive and saline fluids and/or melt volume fraction is estimated to be 7 vol. % at minimum. Other resistivity profile in the across-arc direction indicates that conductive body separated from Pacific plate surface at 80-100 km depth and assumes an overturned form towards backarc direction. The head of the conducting body attains to the lower crust just below Mt. Gassan. This suggests the backarc volcanisms are caused by saline fluids and/or melt overturn rising towards backarc direction.