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，私人投资促进机构将评估在亚临界沸腾和超临界卤水冷凝过程中产生的共存蒸汽和卤水中的水的形态。这项研究将使用pH和氧化还原传感器以及计算机控制的钛流动反应堆，该反应堆可以保持恒定的温度、压力和流速，同时可以同时研究蒸汽和盐水相。最初，实验研究将侧重于开发一个关于氯化钠-水体系中水相物种的内部一致的数据库。虽然汽相和盐水相都将被仪器测量，但它将被最大限度地利用来限制共存卤水中含水物种的分布。实际上，水在蒸汽中的分布缓冲了卤水的分布，并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，将在该系统中增加矿物缓冲剂，以扩大对大洋中脊海底以下热液系统中蒸汽和卤水的化学演化进行模拟所需的成分复杂性。这项研究将有许多应用，包括影响铁、铜和锌矿物在水蒸气和卤水中溶解度的形态，在相分离/分离过程中硼和其他可移动微量元素的蒸气-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.