On the implementation and usability of CPO evolution in geodynamic modelling

Abstract

Flow in the Earth's mantle causes preferred orientation of crystals called Lattice/Crystal Preferred orientation (LPO or CPO). This preferred orientation is one of the main reasons why seismic anisotropy is observed. Seismic anisotropy observations could therefore be used to constrain the mantle flow in geodynamic models through tracking CPO evolution, and computing the resulting elastic tensor and the ansiotropy predicted at the surface. Even though there are many types of CPO models, only a few studies include CPO calculations due to the complexity and computational cost. Here we implemented an extended version of the CPO model D-Rex into the open source community geodynamics code ASPECT. We show that the implementation is correct, how to use it and that it is feasible and important to use in large 3D models. We also show that it is important to calculate CPO, especially for models focusing on plate boundary of smaller scale flow because the resulting elastic directions can greatly deviate from the flow direction. The added infrastructure will also allow for future enhancement, testing and even replacement of the CPO model.