Implications of a metal‐bearing chemical boundary layer in D″ for mantle dynamics

Abstract

At lower mantle conditions, the thermal conductivity of non‐metallic crystals is an order of magnitude lower than that of dense metallic minerals such as FeO, FeSi and Fe, which may be present in a chemical boundary layer at the base of the mantle. Because the core‐mantle boundary is nearly isothermal, variations in the thickness of a metal‐bearing layer induce lateral temperature variations of several hundred kelvin, which in turn affect the pattern of mantle convection. Upwellings should occur where the layer is thickest; the resulting stability of the metal + silicate layer with respect to the flow may also stabilize the pattern of mantle convection, and reduce its time‐dependence.