Influence of Variable Thermal Expansivity and Conductivity on Deep Subduction

This chapter uses numerical models to investigate the dynamics of slabs subducted in the lower mantle in dependence of three important factors that strongly affect their behavior, namely the viscosity contrast between lower and upper mantle, the two major phase transitions at 410- and 660-km depth, and, for the first time, and the pressure and temperature dependence of the coefficients of thermal expansion and conduction. It presents subduction simulations that include pressure-, temperature-, and phase-dependent thermal expansivity and conductivity, and demonstrates that these parameters exert a dramatic effect on the dynamics of lower-mantle slabs. The coefficients of thermal expansion and conduction are the two key thermodynamic parameters of the mantle that control the way heat is transported in the interior by advection and diffusion. The chapter suggests that global-scale subduction models should routinely account for the pressure and temperature variations of these two parameters.