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

[SIT03-16] Influence of majorite on mantle convection

*Hiroki ICHIKAWA¹, Masanori KAMEYAMA², Hiroki SENSHU³, Kenji KAWAI⁴, Shigenori MARUYAMA⁵ (1.GRC, Ehime University and ELSI, Tokyo Institute of Technology, 2.Geodynamics Research Center, Ehime University, 3.Planetary Exploration Research Center, Chiba Institute of Technology, 4.Department of Earth and Planetary Sciences, Tokyo Institute of Technology, 5.Earth-Life Science Institute, Tokyo Institute of Technology)

Keywords:Mantle convection, Majorite, Phase transition

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.