The PI will investigate ductile deformation of polymineralic rocks with emphasis on evaluating inter and intragrain heterogeneities. Among polycrystal plasticity theories used to model deformation, the viscoplastic self-consistent theory is particularly attractive for anisotropic rocks. As a model system the PI plans to investigate first quartz in quartzo feldspathic rocks and use the development of preferred orientation as an indicative parameter in comparisons of models with experiments and naturally deformed rocks.