Glide Mechanisms in Experimentally Deformed Minerals.

A method for study of mechanisms of twin and translation gliding in minerals in rocks has been devised by which slip markings produced experimentally on polished surfaces are related to crystallographic planes by universal stage measurements of the crystal orientations. In specimens strained 5 to 10 percent at 5 to 7 kilobars confining pressure and 700 degrees to 850 degrees C, the glide plane and glide direction for slip and twinning have been determined in olivine, enstatite, kyanite, and diopside. Slip occurs in closest-packed directions, in which also lies the shortest Burgers vector of a unit edge dislocation in the slip plane.