Dislocations in Naturally Deformed Quartzite

Abstract

THERE is increasing interest in the geological significance of the dislocation structures in deformed minerals. Most reported work has described laboratory deformed single crystals of synthetic quartz^1–4 or of olivine⁵, although there have been recent reports of the dislocations in naturally deformed poly-crystalline olivine⁶ and pyrope⁷. We are at present studying the dislocation structures in deformed quartzites from differing geological environments, and comparing them with materials deformed in the laboratory. We have collected extensive data on laboratory deformed alumina, and have compared the naturally deformed quartzites with this material. The comparison should be valid because quartz and alumina are both trigonal and should exhibit broadly similar dislocation structures for similar modes of deformation. The quartzites are compared with polycrystalline alumina because the dislocation structures in deformed polycrystalline materials differ appreciably from those in corresponding single crystals subjected to similar deformation⁸.