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

我们计划沿着不同的俯冲几何形状对应的压力-温度剖面，在600公里深的俯冲洋岩石圈相关条件下确定单晶橄榄石的弹性特性。弹性性能将通过高压和高温（高达25 GPa和1000℃）下的原位布里渊散射来确定。我们将合成和研究不同Fe含量和不同OH含量的橄榄石，覆盖上地幔这一阶段的整个组成范围。此外，我们还计划在与俯冲机制相关的压力和温度下测量反长岩稳定性场内蛇形岩聚集体的声速。在实验研究的同时，我们将对相同的材料进行数值模拟，特别关注其弹性特性，以预测其在实验范围之外的弹性行为。我们还将通过计算方法研究橄榄石体系中塑性变形和结构相变的机制和条件。我们的研究结果将首次提供温度、压力和成分对上地幔最丰富矿物及其最常见蚀变产物的弹性各向异性影响的信息。事实上，橄榄石和蛇纹石的弹性各向异性在俯冲地球动力学背景中起着至关重要的作用，其特征是存在较大的偏应力和岩石的塑性变形，并发展为晶格优先取向和地震各向异性。

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.