Speciation of yttrium in fluorine-rich brines at hydrothermal and metamorphic conditions

含水流体在许多地质过程中起着重要作用。它们是热液和变质环境中化学元素的主要输运介质。尽管这很重要，但这种流体在高温高压下的热力学性质尚不为人所知。稀土元素是溶解在流体中并被流体输送的一类重要元素。基于量子力学的分子建模方法已成为研究复杂流体结构和热力学性质的有力预测工具。在这里，我们建议使用从头算分子模拟来开发含氯和含氟流体中钇的形态模型。从头算分子动力学模拟将辅以元动力学和热力学积分方法，以预测不同溶质种类的稳定性常数作为组成，温度和压力的函数。这些信息将用于构建大多数物种图，并对含氯和含氟地质流体中含y矿物的溶解度进行预测。模拟还将为热液或变质流体对稀土元素的运移机制以及相关矿物的沉积提供新的分子尺度的见解。

Aqueous fluids play an important role in many geological processes. They are major transport media of chemical elements in hydrothermal and metamorphic environments. Despite this importance, the thermodynamic properties of such fluids at high temperatures and pressures are not well known. One important group of elements dissolved in and transported by fluids are the rare earth elements. Molecular modeling approaches based on quantum mechanics have become a powerful and predictive tool to study the structure and thermodynamic properties of complex fluids at the same time. Here, we propose to use ab initio molecular simulations to develop speciation models of yttrium in chlorine- and fluorine-bearing fluids. Ab initio molecular dynamics simulations will be complemented by metadynamics and thermodynamic integration methods to predict the stability constants of different solute species as a function of composition, temperature and pressure. This information will be used to construct majority species diagrams and to make predictions of Y-bearing mineral solubilities in Cl- and F-bearing geological fluids. The simulations will also provide new molecular-scale insight into the transport mechanisms of rare earth elements by hydrothermal or metamorphic fluids and the deposition of related minerals.