First principles investigations of hydrous phases at the bottom of the lower mantle

Abstract:

The global circulation of water in the earth is important to investigate the evolution history and dynamics of the earth, since the physical properties (e.g. atomic diffusivity, melting temperature, electrical conductivity and seismic velocities) of the constituent minerals are considerably changed by the presence of water. Recently, it has been reported that the Al bearing phase H can transport water into the core-mantle boundary (Ohira et al. 2014) and the melting of phase H at the core mantle boundary may contribute to the cause of ultra-low velocity zones (Andrault et al. 2014). Therefore, there is a possibility of the existence of huge water circulation from the surface to the core-mantle boundary regions and the effects of water on the minerals at the bottom of lower mantle should be investigated. In this study, we will discuss the possible effects of water on the elasticity and seismic anisotropy on bridgmanite and post-bridgmanite, and relative phase stabilities of phase H, bridgmanite and post-bridgmanite at the bottom of lower mantle based on the first principles calculation results.