The density of H2O-NaCl-CO2/SiO2 fluids in the crust and upper mantle

水流体是地球内部质量(和热)传递的主要载体，它们在地壳和地幔中的反应性流动控制着元素和溶质物种的动员和迁移/沉积。因此，对流体介导的质量传输过程的定量理解依赖于流体-岩石相互作用的准确建模，该模型将热化学描述与集成的流体流动状态相结合。然而，由于在相关的高压-高温条件下对盐水-挥发性混合溶剂密度的稀疏限制，对深层环境中的反应流体流动的模拟是有限的。因此，这项建议的目的是开发H2O-NaC l-CO2/SiO_2系统中混合复杂流体的实验约束密度模型，该系统是从大洋中脊到俯冲带等广泛地质环境中深部流体的替代。我们将把同步加速器X射线吸收和布里渊散射光谱与为热液研究配备的高压容器结合起来，将现有的密度数据扩展到一个数量级的压力，高达60kbar和800⁰C。收集的实验数据集将在连续预测密度模型中实施，该模型在与地壳和上地幔流体过程有关的条件下有效。新的密度模型将被制定，以确保与模拟地壳环境中反应流体流动的数值代码兼容。最终，这将允许应用目前的结果来限制流体化学对流体路径和时间尺度的影响，从而限制对大型金属矿床的形成。

Aqueous fluids are major vector for mass (and heat) transfer in the Earth’s interior and their reactive flow through the crust and mantle controls the mobilization and transport/deposition of elements and solute species. A quantitative understanding of fluid-mediated mass transport processes thus relies on an accurate modeling of fluid-rock interactions that couples the thermochemical description with the integrated fluid flow regimes. Modeling of reactive fluid flow in deep settings is however limited due to sparse constrains on the density of mixed saline-volatile solvents at relevant high pressure-high temperature conditions. The aim of this proposal is thus to develop experimentally constrained density models for mixed complex fluids in the H2O-NaCl-CO2/SiO2 system that is a proxy for deep fluids in a broad range of geological settings, from mid-oceanic ridges to subduction zones. We will apply a combination of synchrotron X-ray absorption and Brillouin scattering spectroscopy coupled with high pressure vessels outfitted for hydrothermal studies to extend the available density data over one order of magnitude in pressure, up to 60 kbar and 800 ⁰C. The gathered experimental datasets will be implemented in continuous predictive density models valid at conditions that pertain to fluid processes in the crust and upper mantle. The new density models will be formulated to ensure compatibility with numerical codes that simulate reactive fluid flow in crustal settings. Ultimately, this will permit the application of the present results to constrain the effect of fluid chemistry on the fluid pathways and time scales and hence, on the formation of large metal deposits.