Dislocation microstructures in majorite garnet experimentally deformed in the multi-anvil apparatus

Majorite garnets with the composition Mj70Py30 have been deformed in the multi-anvil apparatus at 17 GPa and 2000 degrees C. The microstructure has been characterized by transmission electron microscopy. It is shown that under these conditions majorite garnet is ductile. Dislocations with < 100 > and (1)/(2)< 111 > Burgers vectors are observed with a density 1-5 x 10(12) m(-2). The absence of clear glide planes and the occurrence of subgrain boundaries suggest the importance of diffusion and climb in the plasticity of majorite garnets in mantle transition zone conditions.