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

含水流体是地球内部质量（和热量）传递的主要载体，它们通过地壳和地幔的反应流动控制着元素和溶质物种的动员和运输/沉积。因此，对流体介导的质量传递过程的定量理解依赖于流体-岩石相互作用的精确建模，该模型将热化学描述与综合流体流动机制相结合。然而，由于相关高压-高温条件下混合盐-挥发性溶剂密度的稀疏限制，深层环境中反应流体流动的建模受到限制。因此，本提案的目的是为H2O-NaCl-CO2/SiO2体系中的混合复杂流体建立实验约束密度模型，该体系是广泛地质背景下（从洋中脊到俯冲带）深层流体的代表。我们将结合同步加速器x射线吸收和布里渊散射光谱，再加上为热液研究配备的高压容器，将可用的密度数据扩展到压力超过一个数量级，最高可达60 kbar和800⁰C。收集到的实验数据集将在连续预测密度模型中实施，该模型适用于与地壳和上地幔流体过程有关的条件。将制定新的密度模型，以确保与模拟地壳环境中反应性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.