Japan Geoscience Union Meeting 2016

Presentation information

International Session (Poster)

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

[S-IT06] Interaction and Coevolution of the Core and Mantle

Mon. May 23, 2016 5:15 PM - 6:30 PM Poster Hall (International Exhibition Hall HALL6)

Convener:*Satoru Tanaka(Department of Deep Earth Structure and Dynamics Research Japan Agency for Marine-Earth Science and Technology), Taku Tsuchiya(Geodynamics Research Center, Ehime University)

5:15 PM - 6:30 PM

[SIT06-P15] Ab initio prediction of the incongruent melting relation in the MgO-SiO2 system at multi-megabar

*Takashi Taniuchi1, Taku Tsuchiya1 (1.Geodynamics Research Center, Ehime University)

Keywords:ab initio calculation, MgO-SiO2 system, incongruent melting, multi-megabar

Magnesium silicates are thought to be the major components of the mantle of terrestrial planets and the core of giant planets (Guillot, 1999; Seager et al., 2007). However, the thermodynamic phase equilibrium in the MgO-SiO2 system is still not well studied at multi-megabar, including melting relations. A recent laser shock experience reported two discontinuous phase changes in MgSiO3 at 300-400 GPa (Spaulding et al., 2012), but an ab initio molecular dynamics study identified no clear transition in MgSiO3 liquid (Militzer, 2013). Boates and Bonev (2013), on the other hand, examined a decomposition reaction of liquid MgSiO3 into solid MgO and liquid SiO2 and reported that liquid MgSiO3 is dissociated at ~300 GPa. This result implies a possible incongruent melting. However, the reaction they considered is too simple and unrealistic. The detailed phase diagram in the MgO-SiO2 system is therefore required to be clarified at multi-megabar. In this study, we perform ab initio free energy calculations based on the thermodynamic integration method (Kirkwood, 1935) and determine the melting phase relation in this binary system.