Accomplishment Based Renewal: An experimental study of phase separation and mineral fluid equilibria on iron and hydrogen transport in mid-ocean ridge hydrothermal systems

基于成就的更新：洋中脊热液系统中铁和氢传输的相分离和矿物流体平衡的实验研究

基本信息

批准号：
1736679
负责人：
William Seyfried
金额：
$ 43.1万
依托单位：
University of Minnesota-Twin Cities
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2017
资助国家：
美国
起止时间：
2017-08-15 至 2023-07-31
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1736679&HistoricalAwards=false
关键词：
Accomplishment Based Renewal experimental study

项目摘要

Hydrothermal circulation at mid-ocean ridges constitutes the largest geothermal system on Earth. Venting of spectacular plumes of hot, metal-bearing, fluid into seawater from sulfide structures on the seafloor along the volcanically active global mid-ocean ridge system is the end result of heat and chemical transfer between the ocean crust and the overlying ocean. As a result, the composition of seafloor hydrothermal vent fluids places a major control on ocean chemistry, as it has throughout Earth history. Seafloor hydrothermal fluids also provide dissolved gases and other chemicals to sustain microbial ecosystems that provide clues to the origin of life on Earth. The discovery of submarine hydrothermal venting and their accompanying microbial communities that do not require sunlight or organic matter created by photosynthesis to live, remains one of the most significant discoveries in modern science. The mechanisms, however, by which seawater is transformed to compositionally distinct hydrothermal vent fluids are uncertain, owing to the extreme temperatures and pressures of these processes. This research uses novel laboratory reactor and in-situ sensor systems to carry out first-of-a-kind experiments at the temperatures and pressures of seafloor hydrothermal venting to determine the effect of oxidation-reduction reactions and pH on mineral solubility at temperatures and pressure not previously studied. Goals of the work are to provide fundamental geochemical thermodynamic and kinetic parameters involving iron and hydrogen in water-rock interaction at high temperatures and pressures. The broader impacts of the work to research and science education include (1) Involvement of undergraduate science majors; (2) graduate student training in experimental and theoretical studies of mineral-fluid reaction which enhances their career opportunities; (3) development of new models to predict more accurately the links between the physical and chemical processes in natural multi-component hydrothermal systems; (4) physical infrastructure enhancement with the development of new equipment and techniques to conduct experiments and collect data in the area of phase separation of H2O; and, (5) public outreach in cooperation with K-12 programs at the Bell Museum of Natural History at the University of Minnesota. This research will acquire data to advance knowledge of mineral-fluid reactions that control the chemical evolution of mid-ocean ridge hydrothermal fluids. The experiments specifically address changes in dissolved Fe and H2 in fluids coexisting with mineral buffers at temperatures and pressures sufficient to cause phase separation in the NaCl-H2O system. The research will examine the possibility that fixing dissolved Fe and H2 in mineral-buffered reactions increases the solubility of these components in both fluid phases. This strategy contrasts sharply with previous fluid-only phase separation experiments where the inventory of dissolved Fe was limited. High Fe/Cl and Fe/Mn ratios and high dissolved H2 and H2S concentrations in vapor-rich vent fluids at mid-ocean ridges, especially in the aftermath of magmatic activity, implicate mineral buffering. Thus, the results of this experimental work will provide quantitative rigor to the presently qualitative observations of the temporal evolution of hydrothermal vent fluids at subseafloor temperatures approaching 500°C. These high temperature fluids have some of the highest dissolved Fe and H2 concentrations yet reported; but, in the absence of the experimental data, are difficult to interpret unambiguously in terms of subseafloor redox and pH controlling reactions. Scientific implications of the research will enable the development of theoretically-based predictive approaches for modeling aqueous speciation and mineral solubility in the low density and two-phase regions in the NaCl-H2O system. These conditions also apply to many continental hydrothermal systems. These terrestrial systems have immense scientific, economic, and practical significance and have critical importance to the Earth's thermal budget and geochemical cycles.

海脊中的水热循环构建了地球上最大的地热系统。沿着火山活跃的全球中洋山脊系统从海底的硫化物结构中排出壮观的热，金属含量，将液体从海水中排出，这是海壳和上覆的海洋之间的热量和化学转移的最终结果。结果，海底热液排气流体的组成对海洋化学的重大控制，就像它在地球历史上一样。海底水热液还提供溶解的气体和其他化学物质，以维持微生物生态系统，从而为地球生命起源提供线索。在现代科学中发现不需要光合作用的阳光或有机物的潜在水热通风及其参与的微生物群落的发现之一仍然是现代科学中最重要的发现之一。但是，由于这些过程的极端温度和压力，将海水转化为合成的水热流体的机制尚不确定。这项研究使用新型实验室反应器和原位传感器系统在海底水热通风的温度和压力下进行首次实验实验，以确定在温度和压力下未经研究的温度和压力下氧化还原反应和pH值对矿物质溶解度的影响。这项工作的目标是提供基本的地球化学热力学和动力学参数，这些参数涉及在高温和压力下在水岩相互作用中铁和氢的基础。这项工作对研究和科学教育的更广泛影响包括（1）本科科学专业的参与；（2）矿物流体反应实验和理论研究的研究生培训，从而增强了他们的职业机会；（3）开发新模型，以更准确地预测天然多组分氢基系统中物理和化学过程之间的联系；（4）随着新设备和技术的开发，可以增强物理基础设施，以进行实验并收集H2O相分离领域的数据；（5）明尼苏达大学贝尔自然历史博物馆与K-12计划合作的公共宣传。这项研究将获取数据，以促进对控制中山脊的化学演化水热液的化学演化的了解。该实验专门针对溶解的Fe和H2在FLUS中与矿物缓冲液在温度和压力上共存的FLU中的变化，足以在NACL-H2O系统中引起相位分离。该研究将研究固定矿物质缓冲反应中溶解的Fe和H2的可能性，这会增加两个流体相中这些成分的溶解度。该策略与以前仅流体相位分离实验的形成鲜明对比，在这些实验中，溶解的Fe库存受到限制。高Fe/Cl和Fe/Mn的比例以及富含蒸气的通风液在中山脊的蒸气液中的高溶解的H2和H2S浓度，尤其是在岩浆活性之后，暗示了矿物缓冲。这是这项实验工作的结果将为目前对接近500°C的亚eeploor温度下的水热流体暂时演化的定性观察提供定量严格的观察。这些高温液体具有迄今报告的最高溶解的Fe和H2浓度。但是，在没有实验数据的情况下，很难用层状氧化还原和控制反应的pH值来明确解释。这项研究的科学意义将使基于理论上的预测方法开发，以建模NaCl-H2O系统中低密度和两相区域中的水平规格和矿物溶解度。这些条件也适用于许多连续的热液系统。这些陆地系统具有巨大的科学，经济和实际意义，并且对地球的热预算和地球化学周期至关重要。