Viscous relaxation of grain-scale pressure variations

Abstract

In the presence of grain-scale pressure variations, there will be a natural tendency for deformation to flatten pressure gradients to establish pressure equilibrium. We explore the time-scale of the survival of pressure variations in the presence of power-law creep. Such viscous relaxation turns out to be strongly dependent on the exponent in the power-law creep constitutive relation. For larger exponents, there is the possibility of maintaining pressure variations for the order of a million years, orders of magnitude longer than the viscoelastic relaxation time that is commonly used as a proxy for the pressure relaxation time. Petrologically, this means that while pressure variations may on..