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ti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，实验研究将侧重于建立一个内部一致的NaCl-H2O系统中含水物种数据库。虽然蒸汽相和盐水相都将被测量，但在共存的盐水中，气相将被用来限制含水物质的分布。实际上，水蒸气中含水组分的分布缓冲了卤水的分布，为测定高浓度卤水相中的离子活度提供了一种新的实验策略。随后，将矿物缓冲液添加到系统中，以扩大必要的成分复杂性，以模拟海洋中脊海底热液系统中蒸汽和盐水的化学演化。该研究将有许多应用，包括影响铁、铜和锌矿物在蒸汽和盐水中的溶解度的形态，硼和其他流动微量元素在相分离/分离过程中的汽卤分配等。

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.