Japan Geoscience Union Meeting 2022

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[E] Oral

S (Solid Earth Sciences ) » S-IT Science of the Earth's Interior & Techtonophysics

[S-IT19] Deep Earth Sciences

Sun. May 22, 2022 1:45 PM - 3:15 PM Exhibition Hall Special Setting (2) (Exhibition Hall 8, Makuhari Messe)

convener:Kenji Ohta(Department of Earth and Planetary Sciences, Tokyo Institute of Technology), convener:Kenji Kawai(Department of Earth and Planetary Science, School of Science, University of Tokyo), Tsuyoshi Iizuka(University of Tokyo), convener:Jun Tsuchiya(Geodynamics Research Center, Ehime University), Chairperson:Kenji Ohta(Department of Earth and Planetary Sciences, Tokyo Institute of Technology), Jun Tsuchiya(Geodynamics Research Center, Ehime University)

1:45 PM - 2:00 PM

[SIT19-01] Electrical conductivity of hydrous silicate melt atop of the 410 km seismic discontinuity

*Takashi Yoshino1, Ran Wang1 (1.Institute for Planetary Materials, Okayama University)

Keywords:electrical conductivity, mantle, hydrous silicate melt

A formation of dense hydrous melt layer atop of 410 km seismic discontinuity can account for the difference of geochemical affinity between mid ocean ridge basalt and oceanic island basalt. The low velocity layer with a certain thickness observed at this depth has been regarded as partial molten layer. Here we measured the electrical conductivity of the hydrous silicate melt with composition of incipient melt expected from dehydration melting of hydrous mantle transition zone to constrain the thickness of melt layer and melt fraction. The extremely high electrical conductivity of the hydrous silicate melt requires the formation of very thin melt layer that cannot be seismologically detected. If the partial melting is considered as the origin of the low velocity layer, a very small amount of melt needs to be trapped in the upwelling mantle and rise together. In this case the 410 km seismic discontinuity would not act as a water filter.