3-D convection studies on the thermal state in the lower mantle with post-perovskite phase transition

Sensitivity study of the thermal state in the lower mantle by 3-D convection with post-perovskite phase transition

Phase Transition and Thermal Expansion of MgSiO3 Perovskite.

Results from in situ x-ray diffraction experiments with a DIA-type cubic anvil apparatus (SAM 85) reveal that MgSiO(3) perovskite transforms from the orthorhombic Pbnm symmetry to another perovskite-type structure above 600 kelvin (K) at pressures of 7.3 gigapascals; the apparent volume increase across the transition is 0.7%. Unit-cell volume increased linearly with temperature, both below (1.4...

Tradeoffs in chemical and thermal variations in the post-perovskite phase transition: Mixed phase regions in the deep lower mantle?

The discovery of a phase transition in Mg-rich perovskite (Pv) to a post-perovskite (pPv) phase at lower mantle depths and its relationship to D′′, lower mantle heterogeneity and iron content prompted an investigation of the relative importance of lower mantle compositional and temperature fluctuations in creating topographic undulations on mixed phase regions. Above the transition, Mgrich Pv m...

Dynamic effects of a step-wise increase in thermal conductivity and viscosity in the lowermost mantle

[1] We present numerical models of mantle convection incorporating changes in viscosity and thermal conductivity at depth. Increasing the viscosity and/or thermal conductivity by a factor of 5 at depths below 2000 km increases the size and stability of thermal upwellings. Decreasing the thermal conductivity beneath 2000 km, in contrast, has comparatively little effect on thermal upwellings. Inc...

Mantle dynamics with pressure- and temperature-dependent thermal expansivity and conductivity

In numerical simulations of mantle convection it is commonly assumed that the coefficients of thermal expansion a and thermal conduction k are either constant or pressure-dependent. Pressure changes are generally computed using parametrizations that rely on extrapolations of low-pressure data for a single upper-mantle phase. Here we collect data for both the pressure and temperature dependence ...