Geochemical Controls on the Composition of Coexisting Vapors and Brines: A Novel Experimental Approach to Assess Aqueous Speciation in Subseafloor Hydrothermal Systems

在这笔资金的资助下，PI将评估在亚临界沸腾和超临界盐水冷凝过程中产生的共存蒸汽和盐水中的水溶液形态。该研究将使用pH值和氧化还原传感器以及计算机控制的钛流反应器，该反应器可以保持恒定的温度，压力和流速，同时允许同时研究蒸汽和盐水相。最初，实验研究将集中在开发一个内部一致的数据库中的氯化钠-水系统的水相物种。虽然气相和盐水相都将被仪器化，但气相将被最多地用于限制共存盐水中的水性物质的分布。实际上，水相物质在蒸汽中的分布缓冲了盐水的分布，并提供了一种新的实验策略，用于确定高浓度盐水相中的离子活性。随后，将在系统中添加矿物缓冲层，以扩大模拟大洋中脊海底下热液系统中蒸汽和盐水化学演变所需的成分复杂性。这项研究将有许多应用，包括形态影响铁，铜和锌矿物在蒸汽和盐水中的溶解度，硼和其他移动的微量元素在相分离/偏析过程中的蒸汽-盐水分配，以及其他。

Under this funding, the PIs will assess aqueous speciation in coexisting vapors and brines produced during subcritical boiling and supercritical brine condensation. The study will use pH and redox sensors together with a computer controlled Ti-flow reactor, which can maintain constant temperature, pressure and flow rates, while allowing simultaneous investigation of vapor and brine phases. Initially, the experimental study will focus on development of an internally consistent database for aqueous species in the NaCl-H2O system. Although both the vapor and brine phases will be instrumented, it is the vapor phase that will be utilized most to constrain the distribution of aqueous species in the coexisting brine. In effect, the distribution of aqueous species in the vapor buffers that of the brine and provides a novel experimental strategy for determining ion activities in the highly concentrated brine phase. Subsequently, mineral buffers will be added to the system to expand the compositional complexity necessary to model the chemical evolution of vapors and brines in subseafloor hydrothermal systems at mid-ocean ridges. The study will have numerous applications, including the speciation affecting Fe, Cu and Zn mineral solubility in vapors and brines, vapor-brine partitioning of boron and other mobile trace elements during phase separation/segregation processes, and others.