Investigating grain boundary sliding in olivine by in situ nanomechanical testing in a transmission electron microscope

Abstract:

The partial mechanical coupling between the lithosphere and asthenosphere is controlled by the mechanical properties of olivine-rich rocks. Previous investigations of olivine polycrystals deformed in the Paterson press and in a multianvil apparatus have shown that at relatively low temperature (ca. 1000°C) and high stress, amorphization takes place at grain boundaries under stress and that the onset of ductility of olivine-rich rocks is due to the activation of grain boundary mobility on these amorphous layers. From these observations, a new mechanism behind the lithosphere-asthenosphere transition layer was proposed, which is the onset of GBS controlled by the glass transition temperature of amorphous olivine. Here specimens containing pristine, crystalline grain boundaries are deformed in situ in a transmission electron microscope (TEM) to follow the crystal to amorphous transformation by high-resolution TEM and study the mechanisms at play.