Influence of majorite on hot plumes

Hiroki Ichikawa1, Masanori Kameyama1, Hiroki Senshu2, Kenji Kawai3 and Shigenori Maruyama4, (1)Ehime University, Matsuyama, Japan, (2)Chiba Institute of Technology, Narashino, Japan, (3)University of Tokyo, Bunkyo-ku, Japan, (4)Tokyo Inst Technology, Department of Earth and Planetary Sciences, Tokyo, Japan
Abstract:
Influence of MgSiO3 majorite on the mantle convection has been investigated by using 2-D numerical simulations incorporating stability field of majorite. According to a recent 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 to above ~2200 kelvin in a depth range of 500-660km for Mg2SiO4, very hot upwelling plumes are expected to be strongly influenced by the phase transitions related to majorite. These hot upwellings are occasionally observed in the simulations, even though the average temperature of hot plumes are far less than the stability field of majorite. The dynamics of these upwellings are modified 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 related to majorite.
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