Determination of single-crystal elastic properties of olivine and serpentine as a function of chemical composition at conditions of subduction zones up to GPa, 1000°C

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We plan to determine the elastic properties of single-crystal olivine at conditions relevant for the subducted oceanic lithosphere up to 600 km depth along various pressure-temperature profiles corresponding to different subduction geometries. The elastic properties will be de-termined by Brillouin scattering in-situ at high pressure and high temperature (up to 25 GPa and 1000 ºC). We will synthesize and study olivine with different Fe contents and with differ-ent OH contents, covering the whole compositional range for this phase in the upper mantle. In addition, we also plan to measure the sound velocity of serpentine aggregates within the antigorite stability field, at pressures and temperatures relevant for subduction regimes. In parallel to the experimental study, we will perform numerical simulations of the same materi-als with special interest in the elastic properties in order to predict the elastic behavior at conditions outside the accessible experimental range. We will also investigate by computa-tional methods the mechanisms and conditions for plastic deformation and structural phase transitions in the olivine system. Our results will provide for the first time information about the effect of temperature, pressure and composition on the elastic anisotropy of the most abundant mineral of the upper mantle, and its most common alteration product. In fact, elas-tic anisotropy of olivine and serpentine play a crucial role in the subduction geodynamic set-ting that is characterized by the presence of large deviatoric stresses and plastic deforma-tion of rocks with development of lattice preferred orientation and seismic anisotropy.