Low-temperature plastic rheology of olivine determined by nanoindentation

Low-temperature plasticity is a deformation mechanism that occurs mainly at high stress and low temperatures and may be important in the shallow lithosphere, at the tips of cracks, and in laboratory experiments. Previous studies investigating the low-temperature plasticity of the mineral olivine have exhibited wide variability in their extrapolations to the athermal flow strength or Peierls stress. To better constrain the rheology of olivine, nanoindentation tests were performed on samples in the temperature range of 0-175°C. The indentation properties were converted to uniaxial properties using a finite element-based method. The data were fit to a standard flow law for low-temperature plasticity, and Peierls stresses between 5.32 and 6.45 GPa were obtained. These results provide increased confidence in the extrapolation of high-pressure and high-temperature laboratory experiments to low-temperature conditions and illustrate the applicability of nanoindentation methods to the study of mineral rheology.