Effects of the Compositional Viscosity Ratio on the Long‐Term Evolution of Thermochemical Reservoirs in the Deep Mantle

Numerical experiments of thermochemical mantle convection in 2‐D spherical annulus geometry are performed to investigate the effects of compositional viscosity ratio (Δ η C ) on the long‐term evolution of reservoirs of dense, primordial material in the lowermost mantle of the Earth. The internal heating rate in the primordial material is larger than in the ambient mantle by a factor of 10, accounting for the fact that this material may be...