Collaborative Research: Submarine Fluid Recharge - The Role of Anhydrite and Reactive Transport Modeling of the Endeavour Segment, Juan de Fuca Ridge

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ABSTRACT Intellectual Merit: The proposed research targets advancing our understanding of the structure and evolution of the recharge zone on a well-explored section of the Juan de Fuca Ridge through reactive transport modeling calculations. The research involves: (1) development of numerical computer models of hydrothermal circulation that simulate a variety of geometries (spatial extent, distance of recharge from the ridge), physical properties (porosity, permeability and fault distribution) and recharge styles (along axis, cross-axis); (2) use of improved geochemical models of anhydrite precipitation including the role of low-temperature mineral precipitation, competing chemical reactions, kinetic effects and microbial activity (sulfate reduction) during fluid recharge and subsequent sediment/basalt-seawater reactions as a function of temperature (processes such as different rock composition and varying water rock ratios will also be explored), and (3) incorporation of the geochemical model into the hydrothermal model to obtain a 2-D reactive transport model to further investigate the theoretical nature of hydrothermal recharge controlled by anhydrite precipitation, basalt-seawater reactions and subsequent porosity changes. The work focuses on the deep circulation system related to high-temperature hydrothermal venting and will explore the feedback between anhydrite precipitation and the hydrologic evolution of a recharge zone. Methods include use of finite-element numerical computer modeling techniques to simulate heat and fluid transport in the hydrothermal systems encountered at the Endeavor Segment under varying conditions based on field data (temperature, heat output, geologic structure) and other published material and use of geochemical modeling software to improve our understanding of the complex geochemical processes that characterize the hydrothermal system by including effects of low- and high-temperature mineral precipitation/ dissolution, and kinetic effects with microbial metabolism. Broader Impacts: The research is a multidisciplinary inter-institutional collaboration between institutions in the states of Maryland, Georgia, and Massachusetts as well as international collaboration with the University of Tasmania. The work supports the research of three faculty, one of whom is female, and involves cross training of a postdoc. It also leverages funds by sharing the cost of a postdoc with the University of Tasmania. The models developed in this program are readily transportable to other areas of research such as weathering and soil development, sediment diagenesis, petroleum migration, ore deposit genesis, radioactive-waste disposal, carbon sequestration, reactive barriers in geoenvironmental engineering, geomicrobiology of hot springs, and life in extreme environments.