| 研究実績の概要 |
Xie Longjian completed PhD degree September 2018. He summarized his achievements during the recent five years. It consists three aspects: boron-doped diamond (BDD) heater development in multi-anvil apparatus, viscosity measurement of silicate melts up to ~30 GPa using in-situ falling sphere method and discussion on the evolution of the magma ocean (MO) based on the silicate melt viscosity newly measured in his study. Highlights of his study were (1) generation of ~4000 K temperature (world highest) in the Kawai multi-anvil apparatus by using BDD heater, (2) world first measurements of silicate melt viscosity under the lower mantle condition by applying BDD heater in the in-situ falling sphere viscometry, (3) the viscosity data first time reproduces, experimentally, all the four pressure induced densification mechanisms proposed by molecular dynamic simulation, (4) the viscosity data also suggests a fractional solidification of magma ocean, and (5) the fractional solidification model suggests that the primary upper mantle may be the residual of a ~900 km MO after a combination fractionation of bridgmanite and CaSiO3 perovskite (mass ratio: 94:6), which formed a cumulate layer (~660-900 km depth) at the bottom of MO.
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