In order to estimate the seismic anisotropy of subducted crust, polycrystalline samples of KAlSi3O8 K-lingunite (25% of the total subducted transformed sediments), were synthesized and deformed under the temperature and pressure conditions of the subducted slabs. Transmission electron microscopy characterizations of the recovered samples revealed that the microstructures were clearly dominated by [001] glide involving screw dislocations. For this reason, only {100} could be identified as glide planes, the question of [001] slip on {110} remained open. Few ½<111> dislocations were observed gliding on {110} planes, which implied that ½<111>{110} was a harder slip system than those involving [001] slip. The occurrence of sub-grain boundaries suggested that diffusion and climb might be active under these conditions. To assess the texture of polycrystalline K-lingunite, the crystal preferred orientations were calculated using visco-plastic self-consistent polycrystalline plasticity model in simple shear using the slip systems identified by transmission electron microscopy. Finally, the seismic properties of K-lingunite aggregates were calculated from the crystal preferred orientation and single crystal elasticity tensor. K-lingunite was predicted to have a high seismic anisotropy, which could combine constructively with one of the stishovite (same proportion as K-lingunite at the transition zone depth ranges).

Transmission Electron Microscopy Characterization of Dislocations and Slip Systems in K-Lingunite: Implications for the Seismic Anisotropy of Subducted Crust. A.Mussi, P.Cordier, D.Mainprice, D.J.Frost: Physics of the Earth and Planetary Interiors, 2010, 182[1-2], 50-8