Determination of PVTx properties of dense H2O+NaCl solutions to 5 GPa, 600 °C, and 50 wt% NaCl

流体系统的PVTx性质（近似于天然流体的行为）在实验地球化学和岩石学中至关重要。该项目提出的主要目标是利用布里渊光谱和改进的水热金刚石砧池，以目前可达到的最高精度，确定5 GPa， 600°C和50 wt% NaCl的致密H2O+NaCl溶液的摩尔体积。获得的数据将使数据库在压力上扩展一个数量级，并将作为导出适用于高流体密度的经验状态方程的基础，适用于这个至关重要的水-电解质系统。此外，我们打算确定液相的PT位置，这在压力超过400 MPa的H2O+NaCl体系中是鲜为人知的。另一个重要的目标是在2 GPa以上的压力下校准石英作为拉曼光谱压力传感器，这将增加同时在高压和高温下使用热液金刚石砧细胞进行定量实验研究的可能性。最后，布里渊散射测量将允许测定H2O+NaCl溶液的折射率，以及声速。

Knowledge of the PVTx properties of fluid systems, which approximate the behavior of natu-ral fluids, is crucial in experimental geochemistry and petrology. The primary goal of the project proposed here is to determine molar volumes of dense H2O+NaCl solutions to 5 GPa, 600°C, and 50 wt% NaCl with the maximum currently attainable precision using Brillouin spectroscopy and a modified hydrothermal diamond-anvil cell. The acquired data will extend the database by an order of magnitude in pressure and will serve as the basis to derive an empirical equation of state applicable to high fluid densities for this fundamentally important water-electrolyte system. Furthermore, we intend to determine the PT location of the liq-uidus, which is poorly known in the H2O+NaCl system at pressures above 400 MPa. Another important goal is the calibration of quartz as Raman spectroscopic pressure sensor at pres-sures above 2 GPa, which will enhance the possibilities of quantitative experimental studies at simultaneously high pressures and temperatures using hydrothermal diamond-anvil cells. Finally, Brillouin scattering measurements will allow the determination of the refractive index of H2O+NaCl solutions, in addition to the sound velocity.