Effect of Redox and pH on the Reaction Kinetics of Anhydrite in a Coupled Chemical System: An Experimental Study with Implications for Modeling Vent Fluid Evolution at EPR 9-10 N

摘要-0813861知识价值：拟议实验研究的目的是获取动力学和热力学数据，以加强地球化学模型的开发和应用，这些模型是限制EPR 9-10°N和其他R2 K IS站点热液喷口流体扩展数据库的时空演变所需的。现有的喷口流体数据表明，硬石膏与斜长石、磁铁矿和含钙铝硅酸盐共存，可能提供氧化还原缓冲作用，以应对海洋中脊海底下反应区部分海水硫酸盐的增加。然而，这种化学系统特有的氧化还原缓冲能力是硬石膏与溶解的H2和亚铁之间的反应速率的函数，硬石膏和溶解的H2和亚铁是来自玄武岩中的原生和次生矿物水解的主要还原剂。目前对该体系的动力学和热力学知之甚少。该研究项目将获得必要的动力学/热力学数据，并将这些数据应用于地球化学模型，这些模型将用于限制东太平洋海隆9 N洋脊2000综合研究场址热液喷口流体的时空演变，并适用于其他洋脊2000国际空间站。该项目将利用新开发的水热流反应器，监测pH值和氧化还原条件。更广泛的影响：该项目将提供山脊2000整合和综合工作所需的基本数据，包括随后开发反应-迁移模型所需的基线数据。获取热液条件下的动力学和热力学数据将有助于开发反应-迁移模型，以耦合大洋中脊海底下反应区的物理和化学过程。考虑到硬石膏对洋中脊地壳渗透性的潜在作用，这一点就更有意义了。拟议的研究将受益于本科暑期实习生的参与与NSF/REU计划在地质与地球物理系在UM题为？地球上的液体？同时也加强研究生的培训和指导。此外，在拟议的研究过程中进一步开发钛流反应堆，增强了参与地质学、生物学和化学以及广泛的工程学科研究和培训的科学家可用的研究基础设施。

ABSTRACTOCE-0813861Intellectual Merit: The objective of the proposed experimental study entails acquisition of kinetic and thermodynamic data to enhance the development and application of geochemical models needed to constrain the temporal and spatial evolution of the expanding database for hydrothermal vent fluids at EPR 9-10°N and at other R2K IS Sites. Existing vent fluid data suggest that anhydrite coexisting with plagioclase, magnetite and calcic-bearing aluminosilicates may provide redox buffering in response to the addition of seawater derived sulfate into portions of subseafloor reaction zones at mid-ocean ridges. The redox buffer capacity unique to this chemical system, however, is a function of reaction rates between anhydrite and dissolved H2 and ferrous iron, the principle reducing agents derived from hydrolysis of primary and secondary minerals in basalt. At present little is known about the kinetics and thermodyamics of this system. The research project will obtain the requisite kinetic/thermodynamic data, and will apply these to geochemical models that will be used to constrain the temporal/spatial evolution of hydrothermal vent fluids at the East Pacific Rise 9N Ridge2000 Integrated Study Site, with applicability to the other Ridge2000 ISS as well. The project will make use of a newly-developed hydrothermal flow reactor with monitored pH and redox conditions. Broader Impacts: The project will provide essential data required for Ridge2000 integration and synthesis efforts, including the baseline data required for subsequent development of reaction-transport models. The acquisition of kinetic and thermodynamic data under hydrothermal conditions will help to develop reaction-transport models designed to couple physical and chemical processes in subseafloor reaction zones at mid-ocean ridges. This takes on added significance considering the potential role of anhydrite on crustal permeability at mid-ocean ridges. The proposed research will benefit from the participation of undergraduate summer interns in connection with the NSF/REU program in the Department of Geology and Geophysics at the UM entitled ?Fluids in the Earth?, while also enhancing graduate student training and mentoring. Moreover, the further development of the Ti-flow reactor in the course of the proposed study enhances the research infrastructure available to scientists involved in research and training in geology, biology and chemistry, as well as in a broad range of engineering disciplines.