Japan Geoscience Union Meeting 2015

Presentation information

International Session (Oral)

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

[S-IT03] Structure and dynamics of Earth and Planetary deep interiors

Mon. May 25, 2015 4:15 PM - 6:00 PM 106 (1F)

Convener:*Takashi Yoshino(Institute for Study of the Earth's Interior, Okayama University), Satoru Tanaka(Department of Deep Earth Structure and Dynamics Research Japan Agency for Marine-Earth Science and Technology), Dapeng Zhao(Department of Geophysics, Tohoku University), Masanori Kameyama(Geodynamics Research Center, Ehime University), John Hernlund(Earth-Life Science Institute, Tokyo Institute of Technology), Chair:Takashi Yoshino(Institute for Study of the Earth's Interior, Okayama University), Yoichi Nakajima(RIKEN SPring-8 Center)

5:00 PM - 5:15 PM

[SIT03-11] First principles study on the phase stability and elasticity of potassium-host hexagonal aluminous phases

*Kenji KAWAI1, Taku TSUCHIYA2 (1.Department of Earth Science and Astronomy, Graduate School of Arts and Sciences, University of Tokyo, 2.Geodynamics Research Center, Ehime University)

Keywords:High pressure, Pottasium, Lower mantle, Aluminous phase

In order to understand the fate of the potassium-bearing phase subducted into the deep Earth's interior, we have studied the high-pressure stability and elasticity of KMg2Al5SiO12 hexagonal aluminous phase (K-Hex) by means of the density functional computation method. The K-Hex phase is found to be mechanically stable up to 150 GPa and also energetically more stable than the calcium-ferrite (K-CF) type structure up to 150 GPa. In addition, calculations indicate that when the spinel composition coexists with the K-hollandite (K-Hol) phase, the K-Hex phase becomes more stable than the K-Hol phase at pressures above ~27 GPa. This suggests that the hexagonal aluminous phase be a potential host of the incompatible large-ion elements such as potassium in the lower mantle, especially in the subducted basaltic Mg and Al rich composition. Finally, seismic velocities of the K-Hex phase are found slower than Mg-perovskite (pv) in the lower mantle pressures, while its density is larger than Mg-pv over 70 GPa