Texture development in experimentally deformed two-phase aggregates of calcite and anhydrite

Fully quantitative textures have been measured from experimentally deformed two-phase aggregates of calcite and anhydrite. Two sets of deformation experiments were performed. Firstly, to investigate the development of microstructure and texture with composition, samples with varying volume proportions of calcite and anhydrite were deformed to 20% strain al identical conditions. Secondly, to study the texture development of the two materials with strain and explore the possible use of texture index as a strain gauge in polyphase materials, pure calcite and pure anhydrite were deformed at the sane conditions as the two-phase rocks to strains of 6%, 12% and 20%. The textures in both calcite and anhydrite were found to be similar, but not identical, to those reported in previous studies for pure samples. Our experimental investigations and measured textures show that the textures both of the pure materials and of the two-phase rocks depend not only on strain but also on stress and grain size, through their influence on the deformation mechanisms. The dependence of texture index wit:? change in deformation mechanism is particularly pronounced in the anhydrite component, where the texture index decreases with grain size, which decreases with anhydrite content. The texture in the pure calcite and in the calcite component of the two-phase rocks was influenced by a preexisting fabric. The intensity of the texture in the deformed samples seems to correlate with the stress in the calcite rather than with strain. (C) 1997 Elsevier Science Ltd.