Experimental investigation of the creep behavior of garnet at high temperatures and pressures

To provide constraints on the rheological properties of garnet, we have experimentally investigated the creep behavior of garnet at high pressures and temperatures using a deformation-DIA. Samples were cold-pressed from a garnet powder and deformed at constant displacement rates ranging from 1.1×10^-5 to 2.6×10^-5 s^-1 at high temperatures (1 273-1 473 K) and high pressures (2.4-4.1 GPa). Differential stress and pressure were measured using X-ray diffraction techniques based on the elastic strain of various lattice planes as a function of orientation with respect to the applied stress field. The plastic strain of a deforming sample was monitored in-situ through a series of radiographs. Our results provide a measure of the dependence of creep rate of garnet on the temperature with an activation energy of ~280 kJ/mol and on pressure with an activation volume of ~10×10^-6 m³/mol. The flow behavior of garnet quantified by this study provides the basis for modeling geodynamic processes occurring within subducted lithosphere.