Recent Advances in High Pressure and Temperature Rheological Studies

Rheological studies at high pressure and temperature using in-situ X-ray diffraction and imaging have made significant progresses in recent years, thanks to a combination of recent developments in several areas： （1） advances in synchrotron X-ray techniques, （2） advances in deformation devices and the abilities to control pressure, temperature, stress, strain and strain rates, （3） theoretical and computational advances in stress determination based on powder and single crystal diffraction, （4） theoretical and computational advances in modeling of grain-level micromcchanics based on elasto-plastic and visco-plastic self-consistent formulations. In this article, we briefly introduce the experimental techniques and theoretical background for in-situ high pressure, high temperature rheological studies, and then review recent studies of rheological properties of major mantle materials. Some currently encountered issues have prompted developments in single-crystal quasi-Laue diffraction for complete stress tensor determination and textural evolution of poly-phased composites based on X-ray microtomography. Future prospects are discussed.