[SCG50-P05] Semi-brittle behavior of olivine single crystals under the conditions of Earth’s mantle transition zone
Keywords:olivine, phase transition, semi-brittle flow, microcrack, deep-focus earthquake
Array of microcrack parallel to either (100), (010) or (110) plane was developed at an ~50 degree to the direction of uniaxial compression. Rotation of olivine axes associating the formation of subgrain boundaries was observed around the microcrack arrays, showing that plastic deformation of the olivine single crystal inevitably associated formation of the microcracks. In most samples, microcracks coalesced and then a few throughgoing fractures were developed. Particles of wadsleyite /ringwoodite having a diameter of a few micrometer or less were preferentially nucleated on the microcrack surfaces. Ultrafine-grained domains, which consist of the wadsleyite /ringwoodite particles, were formed along the throughgoing fractures. Development of a banded ultrafine-grained domain was also observed along a throughgoing fracture, implying that shear localization could occur as a result of semi-brittle flow of olivine and a transition from dislocation creep to grain-size-sensitive creep in subducting slabs at depths > 410 km.