The Thickness of Phase Transformation Layers in the Earth’s Mantle
Differences in regional temperature distributions in the mantle induce deviations of phase equilibrium surfaces from the spherically symmetrical shape.
A complex mineral composition of transformable materials (e.g. olivine(Mgx Fe1−)2SiO4, x ≃0.9) results in the formation on the p, T (pressure, temperature) plane, instead of the phase equilibrium line determined by the Clausius-Clapeyron equation, of an area of low- and high-pressure phase coexistence in the Earth’s interior (Fig. 1, a).
In areas with vertical displacements (mid-oceanic ridges, subduction zones) phase transition kinetics leads to the transformation of the equilibrium surfaces into a layer even for minerals of simple chemical composition like Mg2SiO4 (Fig. 1, b).
KeywordsSiO2 Magnesium Silicate Posit Olivine
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