Layered convection and the impacts of the perovskite‐postperovskite phase transition on mantle dynamics under isochemical conditions

The issue of the style of the mantle convection process remains important to the understanding of Earth's deep interior and surface processes. While results from structural seismology may be interpreted to support the existence of a whole mantle convection regime, in several geographic regions high‐resolution reconstructions of Benioff zone body wave heterogeneity demonstrate that the downgoing slab appears to be “trapped” in the transition zone rather than continuing to penetrate unimpeded into the lower mantle. The presence of the recently discovered exothermic perovskite‐postperovskite (Pv‐pPv) phase transition that appears to define the top of the D ″ layer adjacent to the core‐mantle boundary may be expected to exert considerable impact on the mixing process. On the basis of the use of the most recent mantle parameters derived on the basis of mineral physics and a viscosity model inferred from glacial isostatic adjustment and Earth rotation observables, we reinvestigate the impact of the Pv‐pPv transition on mantle mixing. Our analyses are based on a newly constructed axisymmetric control volume model, which is described in detail. Analyses with this model demonstrate that the action of the Pv‐pPv transitions slightly decreases the tendency to layered flow due to the endothermic transitions that occur at 660 km depth and enhances the absolute radial mass flux especially in the lower mantle. However, the results also demonstrate that the episodically layered style of mantle mixing persists in models in which the strength of the Pv‐pPv transition is significant.