A GENERAL KINEMATIC MODEL FOR CRYSTALLOGRAPHIC PREFERRED ORIENTATION (CPO) DEVELOPMENT IN MINERALS

Crystallographic preferred orientations (CPO) provide a rich record of deformation processes in both the mantle and crust. CPOs are used to constrain lithospheric strength profiles, deformation mechanisms, and tectonic motion, and also to interpret seismic anisotropy. The interpretation of CPOs depends on a detailed understanding of how crystallographic orientations develop under different conditions and deformation geometries. Numerical models of CPO development are therefore an important complement to deformation experiments and natural observations, as they can quickly simulate CPO development under a wide range of conditions. Such models are key to interpreting measurements of CPO using electron backscatter diffraction (EBSD), and if coupled with single crystal physical properties, these models can also be incorporated into geodynamic simulations to evaluate the predictions of those models against seismic observations.

Here, I generalize the kinematic approach (D-Rex) of Kaminski et al. (2004), currently limited to olivine-enstatite assemblages. The generalized model can be applied to a broad class of mineral symmetries and slip systems. By using this kinematic approach, dislocation glide, grain boundary migration, subgrain rotation, and grain boundary sliding can all be considered in modeling CPO development. The Matlab implementation of the method interfaces closely with the MTEX toolbox, making it easy to specify the mineral symmetry and active slip systems, and plot results. The close interface with the MTEX toolbox also facilitates tensorial calculations from the resulting textures, such as seismic wavespeeds. I use the generalized model to simulate CPO texture development for various minerals such as olivine, quartz, calcite, and ice.