How Point Defects and Dislocations Drive Flow in the Deep Mantle

Abstract:

Large scale flows which are responsible for the dynamics of planetary interiors rely ultimately on the motion of lattice defects: point defects, dislocations, grain boundaries. A description of the defects at the atomic scale is necessary to describe how their mobility depend on pressure, temperature, stress.

A key stage in multiscale numerical modeling is the description of the collective behavior of defects which depends not only on their mobilities, but also on their interactions. Creep mechanisms usually involve interaction between different kind of defects. In diffusion creep, grain boundaries are sources and sinks for point defects. In dislocation creep dislocations not only glide, but also climb by emitting absorbing point defects.

In this presentation we describe new results on the interaction between point defects and dislocations in mantle minerals and how dislocation mobilities are affected resulting in novel deformation mechanisms in the lower mantle.