Japan Geoscience Union Meeting 2022

Presentation information

[E] Poster

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

[S-IT19] Deep Earth Sciences

Mon. May 30, 2022 11:00 AM - 1:00 PM Online Poster Zoom Room (22) (Ch.22)

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), Tsuyoshi Iizuka(University of Tokyo), Kenji Kawai(Department of Earth and Planetary Science, School of Science, University of Tokyo)

11:00 AM - 1:00 PM

[SIT19-P09] Influence of high oxygen fugacity on melting temperature of wadsleyite

*Kazutaka Yamaguchi1, Takaaki Kawazoe1, Toru Inoue1, Takeshi Sakai2 (1.Hiroshima University, 2.Ehime University)


Keywords:Wadsleyite, Mantle transition zone, Oxygen fugacity buffer, Melting temperature, Quenched crystals

About 60% of the upper part of the Earth's mantle transition zone is composed of wadsleyite, which is the high-pressure phase of olivine. It is known that water and ferric iron are supplied to the mantle transition zone by subduction of the oceanic plates. A recent study revealed that ferric iron lowers melting temperature of bridgmanite, the major mineral in the lower mantle, in the MgO-FeO-Fe2O3-SiO2 system (Sinmyo et al., 2019). However, the effect of high oxygen fugacity on melting temperature of wadsleyite has not been studied so far. Therefore, in this study, we conducted experiments to clarify the effect of high oxygen fugacity on the melting temperature of (Mg0.9,Fe0.1)2SiO4 wadsleyite using a Kawai-type multi-anvil press. The experiments were performed 11 times in the range of 13.7-16.6 GPa and 1300-1500 ℃ with controlled oxygen fugacity by Re-ReO2 or Mo-MoO2 buffer. As a result, quenched crystals were observed in the range of 1500-~1900 ℃ at high oxygen fugacity with controlled oxygen fugacity by Re-ReO2 buffer while no quenched crystals were observed at low oxygen fugacity with controlled oxygen fugacity by Mo-MoO2 buffer. Wadsleyite with the (Mg0.9,Fe0.1)2SiO4 composition melts at about 2300 ℃ at low oxygen fugacity (Ohtani et al., 1998). Therefore, this result shows that the melting temperature of wadsleyite is lowered by at least about 800 ℃ due to the influence of high oxygen fugacity.