13:45 〜 14:00
[SIT19-01] Electrical conductivity of hydrous silicate melt atop of the 410 km seismic discontinuity
キーワード：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.