A kinematic model for recrystallization and texture development in olivinepolycrystals

The interpretation of seismic anisotropy in the mantle requires a knowledge of the relationship between the lattice preferred orientation (LPO) of cry stals and the convective flow field. In order better to understand this lin k, we present a model for the evolution of LPO in olivine aggregates that d eform by both intracrystalline slip and dynamic recrystallization. Dynamic recrystallization depends on the dislocation density of the grains, which i s a function of the applied local stress. Grains with a large density of di slocations lower their bulk strain energy by nucleating strain-free sub-gra ins at a rate proportional to a dimensionless nucleation parameter lambda*. Grains with high energy are then invaded by grains with low energy by grai n-boundary migration, at a rate proportional to a dimensionless grain-bound ary mobility M*. The value of lambda* is constrained by observed LPO patter ns in experimentally deformed olivine aggregates, and M* is constrained by the temporal evolution of the strength of the LPO. For M* = 125 +/- 75 and M* > 3, the model predictions agree well with the experimental results. Num erical calculations of LPO using our model are significantly faster than th ose based on viscoplastic self-consistent or equilibrium-based theories, ma king the model especially suitable for applications for complex convective flows. (C) 2001 Elsevier Science B.V. All rights reserved.