Numerical simulations of texture development and associated rheological anisotropy in regions of complex mantle flow

The development of Lattice Preferred Orientations (LPO) within olivine aggregates under flow in the upper mantle leads to seismic and rheological (or viscoplastic) anisotropies. We compare predictions from different micromechanical models, applying several commonly used theoretical descriptions to an upwelling flow scenario representing a typical oceanic spreading center. Significant differences are obtained between models in terms of LPO and associated rheology, in particular in regions where the flow direction changes rapidly, with superior predictions for the recently proposed Second-Order approach. This highlights the limitations of ad hoc formulations. LPO-induced rheological anisotropy may have a large effect on actual flow patterns with 1-2 orders of magnitude variation in directional viscosities compared to the isotropic case. Citation: Castelnau, O., D. K. Blackman, and T. W. Becker (2009), Numerical simulations of texture development and associated rheological anisotropy in regions of complex mantle flow, Geophys. Res. Lett., 36, L12304, doi:10.1029/2009GL038027.