- © The Mineralogical Society Of America
This chapter focuses on dislocations and slip systems that are responsible for the plastic flow of high-pressure mantle minerals. After briefly introducing some basic concepts on crystal plasticity, we describe some recent experimental advances of the last decade that have contributed to our understanding of the rheology of mantle minerals. Among them, we describe some progress in the achievement of deformation experiments under high pressure. A more detailed review is presented by Durham et al. (this volume). We present then a novel Transmission Electron Microscopy (TEM) technique: Large Angle Convergent Beam Electron Diffraction (LACBED), which is very well adapted to the characterization of dislocations in beam sensitive materials, as well as the determination of dislocation Burgers vectors and characters from the fine analysis of X-ray diffraction peak broadening.
The present review is in the continuity of the paper entitled “Plastic Rheology of Crystals” by Poirier, published in 1995 in “Mineral Physics & Crystallography— A Handbook of Physical Constants” (AGU Reference Shelf 2). Poirier’s paper reviewed the plasticity of some important minerals including olivine and pyroxenes. Concerning these two minerals, the reader is invited to refer to Poirier’s contribution. In 1995, Poirier stated about high-pressure mantle minerals: “Despite their importance for the rheology of the transition zone and the lower mantle, there is no information on the plasticity of the high-pressure mantle minerals in the relevant conditions of temperature and pressure.” Seven years later, the situation has significantly evolved and is still rapidly changing. It is the aim of this paper to highlight these recent advances.
Plastic flow is basically a transport phenomenon controlled by the motion of defects: point defects, dislocations, or grain boundaries. The driving force is provided by the applied shear stress. In many cases, deformation is produced by the motion of dislocations and the present paper …