Mineralogy of the Deep Mantle - The Post-Perovskite Phase and its Geophysical Significance

The phase equilibria, structures, and properties of a high-pressure polymorph of silicate perovskite, called post-perovskite, are discussed. This phase was discovered in 2004 and provides a viable candidate for a deep mantle phase transition in the primary lower mantle mineral, silicate perovskite. Post-perovskite may exist in regions of the lowermost mantle at temperatures below about 3,000. K, and the phase transition from perovskite to post-perovskite may explain observations of a velocity discontinuity in seismic S waves and relatively strong anisotropy of the lower most mantle D" region. The phase transition has important dynamical consequences for heat transport and boundary layer instabilities.