Li Li1, Donald Weidner1, Jiuhua Chen1, Paul Raterron2, Michael Vaughan1, Shenghua Mei3, and William Durham3
1 Stony Brook University, Stony Brook, NY 11794
2 Université Sciences et Technologies de Lille, Bât C6, Villeneuve d'Ascq-Cedex, 59655, France
3 Lawrence Livermore National Laboratory, Livermore, CA 94550
NSLS-X17B (MAP)
Knowledge of the rheological properties of mantle materials is critical in modeling the dynamics of the Earth. The flow law of olivine defined at mantle pressure and temperature is especially important since the pressure dependence of rheology may affect our estimation for the strength of olivine in the Earth's interior. Conventional deformation methods in defining the flow law of olivine have to face factors of large uncertainties of differential stress measurements and/or limited confining pressure for deformation. In this study, high-temperature (up to 1473 K) deformation experiments of polycrystalline olivine (average grain size < 5 micron) at pressure up to 6.5(0.2) GPa were conducted in-situ using large-volume high-pressure apparatus (Deformation DIA) and synchrotron x-ray radiation. More than 30 % strain was generated during the uniaxial compression. The sample lengths during the deformation process were monitored by x-ray radiography. The strain rate was derived with precision up to 10-6 s-1. Macroscopic differential stress was measured at constant strain rate (~ 10-5 s-1) using a multi-element solid-state detector combined with a conical slit. The new data, measured up to 1473 and 6.5 GPa, fits well an empirical power-law creep flow law under the condition that the activation energy is 440 kJ/mol and the activation volume is less than 5 cm3/mol. Consistent with TEM observations on recovered samples, tests for grain size dependence of flow, and the empirical power law exponent, we conclude that power-law creep assisted by dynamic recrystallization is the dominant flow mechanism for olivine at upper mantle conditions. This technique can be applied in defining the rheological flow laws for high-pressure materials in the Earth's interior.