Stationary points in activation energy for heat dissipated with a power law temperature-dependent viscoelastoplastic rheology

We report that there exist a local maximum and minimum in the activation energy E_a describing mechanical heat dissipation of olivine for a given initial temperature and amount of deformation. The stationary point for the minimum dissipation is ~200 kJ/mol lower than that for the maximum. For larger activation energy than the stationary point for maximum dissipation, plastic deformation is sharply weakened and the temperature rise disappears altogether. Higher values of the initial temperature produce a larger local maximum for activation energy. The amount of heat dissipation increases with E_a in a nonlinear manner. Our results have direct ramifications on shear zone, which is governed by the amount of mechanical heat dissipation. We have observed them over a wide range of temperature and deformation boundary conditions. Our two-dimensional model study can provide valuable insight to enable greater predictive capability for the development of geodynamic shear zone in planetary-scale plate tectonics.