Chemical Properties
Another potentially important effect that needs to be better characterized for the post-perovskite phase transition is the influence of other chemical components that are known to be present to some degree in Earth's lowermost mantle. The phase transition pressure (characterized by a two-phase loop in this system), was initially thought to decrease as the FeO content increases, but some recent experiments suggest the opposite. However, it is possible that the effect of Fe2O3 is more relevant as most of iron in post-perovskite is likely to be trivalent (ferric). Such components as Al2O3 or the more oxidized Fe2O3 also affect the phase transition pressure, and might have strong mutual interactions with one another. The influence of variable chemistry present in the Earth's lowermost mantle upon the post-perovskite phase transition raises the issue of both thermal and chemical modulation of its possible appearance (along with any associated discontinuities) in the D" layer.
Read more about this topic: Post-perovskite
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