The Layered Nature of Planetary Mantle

Abstract:

The formation of layered structures is a common feature within many natural system and occur on various scales (planets, Earth's oceans, magma chambers, etc.). Since the knowledge of slab stagnation in the transitions zone of the Earth's mantle the question whether the mantle is or at least has been layered to some degree is still under debate. On this basis we address two important features that lead to layered mantle convection and may affect each other and with this the thermal evolution of the mantle and the evolving heterogeneities. On the one hand we examine a double-diffusive system that is capable of the self-organised formation of layers from a previously non-layered state and on the other hand we incorporate a phase transition. In oder to determine the interaction of double-diffusive layers with a phase transition we carried out numerical simulations ranging from exothermic to endothermic conditions. Taking into account a depth and temperature dependence of the phase transition the results show that on the one hand double-diffusive layering is strongly affected by the presence of phase transition but on the other hand the equilibrium position of the phase transition is shifted depending on the properties of the considered transition. In addition to that we incorporate the chemical dependence of the phase change and determine the influence on the layer growth and the overall dynamics.