[S-IT03_29PM1] Structure and dynamics of Earth and Planetary deep interiors

[SIT03-16] メジャーライト相がマントル対流に与える影響

*市川 浩樹¹、亀山 真典²、千秋 博紀³、河合 研志⁴、丸山 茂徳⁵ (1.愛媛大学地球深部ダイナミクス研究センター及び東京工業大学地球生命研究所、2.愛媛大学　地球深部ダイナミクス研究センター、3.千葉工業大学　惑星探査研究センター、4.東京工業大学　地球惑星科学専攻、5.東京工業大学　地球生命研究所)

キーワード：マントル対流, メジャーライト, 相転移

Influence of MgSiO₃ majorite on the mantle convection has been investigated by using numerical simulations. According to a first principles study (Yu et al., 2011), wadsleyite decomposes to an assemblage of majorite plus periclase with a large negative Clapeyron slope. Since stability field of majorite is limited at high temperature, downwellings are considered to be unaffected by this phase boundary. On the contrary, the upwelling plumes may be significantly modified by this phase boundary. The asymmetry on upwelling and downwelling caused by the phase transitions may induce strong effects on the thermal evolution and the thermal structure of the mantle. In this study, we performed 2-D numerical simulations on thermal convection of the mantle incorporating majorite stability field. According to our numerical results, very hot upwelling plumes are strongly influenced by the phase transitions related to majorite. The dynamics of these upwellings are controlled by the release and the absorption of latent heat induced by the transitions as well as interruption of currents due to the large negative Clapayron slope of the transition between wadsleyite and majorite plus periclase.