Induced compositional layering in a convecting fluid layer by an endothermic phase transition

An endothermic phase change in the presence of chemical heterogeneitles can act as an efficient filter, such that heavy material is sequestered below the phase change and light material is trapped above the phase change. Due to the fact that the endothermlc phase change damps thermal convection, it can act as a "trap door" for chemical heterogeneitles Ascending flows which are chemically dense will need more thermal buoyancy to rise through the transition than ascending flows whose composition is closer to the background composition Likewise, descending flows which are chemically light need more thermal buoyancy to sink through the transition. The results of a state of numerical calculations of two-dimensional, double diffuswe convection in a fluid layer with an endothermic phase change suggests that, if the 670 km seismic discontinuity has a steep enough Clapeyron slope, compositional layering may be induced and dynamically maintained by the transition. Furthermore, these calculations also show that the phase change and compositional boundaries will approximately coincide.