Dynamic recrystallization by subgrain rotation in olivine revealed by electron backscatter diffraction

We document how dynamic recrystallization by subgrain rotation (SGR) develops in natural olivine-rich rocks deformed extension to up 50% bulk finite strain (1473 K, confining pressure of 300 MPa, and stresses between 115 180 MPa) using electron backscatter diffraction (EBSD) mapping. SGR occurs preferentially highly grains (well-oriented deform dislocation glide) subjected local stress concentrations due interactions with hard neighboring (poorly-oriented olivine crystals or pyroxenes). Subgrains (misorientation <15°) are mainly delimited tilt walls composed combinations dislocations the [100](001), [001](100), [100](010) [001](010) systems, order decreasing frequency. The activation prevalence these systems agree a Schmid factor analysis data for high-T creep olivine. development closed 3D cells requires contribution at least three different slip implying high (local) stresses. transition from grain boundaries ?15°) is characterized sharp change misorientation axes that accommodate difference orientation two subgrains grains. propose this marks creation incorporation new defects (grain boundary Burger vectors and, likely, disclinations disconnections) newly-formed might be favoured increasing misalignment across boundary. Finally, we strong misorientations within parent grains, accumulation low angle boundaries, them recrystallized may thus produce dispersion crystal preferred without need sliding.