Generally one of low temperature and pressure as up to 5 km depth from the ground surface in contrast to semi-brittle or semi-ductile or brittle ductile that occurs at greater depths with more pronounced phenomenon such as pressure solution under low grade metamorphism. Ductile regime is of highest pressure and temperature and causes permanent shape changes of rock masses by plastic permanent or ductile deformation. High grade of upper amphibolites metamorphic conditions prevail with large amount of mineral and chemical changes. Fig after P Rey of Monash, Au from online ebook on Tectonics.