[SCG51-P05] Single crystal elasticity of Fe-bearing phase E by Brillouin spectroscopy
Keywords:Brillouin scattering, Phase E, Seismic wave velocities
We synthesized Fe-bearing phase E single crystals in a multi-anvil apparatus. Chemical composition as well as crystal structure have been determined using electron microprobe analysis, Mössbauer spectroscopy, and single-crystal X-ray diffraction. We derived the full elastic stiffness tensor by Brillouin spectroscopy on two single crystals of selected orientations. We found phase E to have both the lowest bulk modulus and shear modulus among the DHMSs at ambient conditions. Phase E shows very low compressional and shear velocities especially when compared to the other principal minerals likely present in subducting slabs after serpentine breakdown. Modelling of seismic velocities in dry and hydrated upper mantle and transition zone rocks suggests that the presence of even small amounts of phase E can appreciably lower seismic wave velocities. Phase E could be used as seismological indicator for water stored at depth in subducting scenarios. The elasticity of phase E under mantle conditions will be explored in future research.