How Minerals Control Hydrothermal Organic Reactivity

在海山、大陆架、洋中脊和其他地方的海底循环的液体含有溶解的有机化合物，这些化合物在穿过海洋地壳的过程中，暴露在高温高压的环境中，在那里它们转化为其他有机分子。这些有机物不仅为深层生物圈中的微生物提供食物，而且它们与矿物质的反应将它们变成了其他有机分子。这种类似的反应和转变发生在地球早期的海洋地壳中，很可能在形成导致地球上生命的基本有机成分方面发挥了重要作用。本研究开展了一系列高温高压实验（分别为200至350℃和70至100 MPa），将表征良好的溶解性、同位素标记的水性有机和手性化合物与各种常见的海底热液氧化物和硫化物矿物反应，以研究有机化合物的变化及其转化速度。转化和反应速率将作为温度和压力的函数以及矿物在表面积、电荷分布和半导体性质方面的催化性质的函数进行检查。结果数据将用于确定基本的热力学和动力学参数，这些参数可用于制定和测试预测，并检查水岩相互作用和矿物催化的含义，因为它们适用于海洋地壳中有机分子的发展。模拟海底热液系统的实验将作为pH值，离子强度和氧化还原状态的函数运行。实验将采用热液金袋（狄克逊弹）和静态金胶囊两种实验装置。实验将使用水形态建模代码（例如SUPCRT和EQ3/6）进行设计。静态和金袋实验中的有机溶质、矿物反应物和产物以及溶解气体将通过高精度气相色谱和气相色谱质谱法进行分析。x射线衍射，扫描电子显微镜和扫描透射电子显微镜。初步实验已经证明了概念的证明，即实验是成功的，并产生了可解释的结果。这项研究的更广泛影响包括通过利用这项研究改变亚利桑那州立大学本科地球化学、有机化学和天体生物学学生的教学方式，将研究和教育显著结合起来。研究将纳入课程，并将开发一系列关于海底热液系统和热液有机地球化学主题的播客和视频，作为课程的一部分。然后，这些将通过学生众包进行改进，并发布到互联网上供公众使用。该项目的成果将广泛适用于整个学术部门，包括化学、水文、地热和材料科学等领域。所导出的基本热力学参数和速率常数将对化学和石油工程工业部门产生潜在的巨大影响。

Fluids circulating through the seafloor at seamounts, continental shelves, mid-ocean ridges, and elsewhere contain dissolved organic compounds that, during the course of their transit through the ocean crust, are exposed to elevated temperature-pressure environments where they are transformed into other organic molecules. These organics not only feed microbes in the deep biosphere but their reactions with minerals change them into other organic molecules. Such similar reactions and transformations that happened in the ocean crust back during the earliest days of our planet are likely to have played a major role in the formation of the essential organic components that resulted in life on Earth. This research carries out a series of high temperature and pressure experiments (200 to 350 C and 70 to 100 MPa, respectively) in which well-characterized, dissolved, isotopically-labelled, aqueous organic and chiral compounds are reacted with a variety of common seafloor hydrothermal oxide and sulfide minerals to examine the resulting changes in organic compounds and their rates of transformation. Transformations and rates of reaction will be examined both as a function of temperature and pressure as well as a function of the catalytic properties of the minerals in terms of surface area, charge distribution, and semi-conductor properties. Resulting data will be used to determine fundamental thermodynamic and kinetic parameters that can be used to make and test predictions and examine the implications of water-rock interaction and mineral catalysis as they apply to the development of organic molecules in the ocean crust. Experiments mimicking seafloor hydrothermal systems will be run as a function of pH, ionic strength, and redox state. Both hydrothermal gold bag (Dixon bomb) and static gold capsule experimental apparatuses will be used. Experiments will be designed using aqueous speciation modeling codes (e.g., SUPCRT and EQ3/6). Organic solutes, mineral reactants and products, and dissolved gases from the static and gold bag experiments will be analyzed by high precision gas chromatography and gas chromatographic mass spectrometry. X-ray diffraction, scanning electron microscopy, and scanning transmission electron microscopy. Preliminary experiments have already demonstrated proof of concept in terms of experiments being successful and yielding interpretable results. Broader impacts of the research include significant integration of research and education by using the research to transform how undergraduate geochemistry, organic chemistry, and astrobiology students are taught at Arizona State University. Research will be incorporated into courses and a series of podcasts and videos on themes relating to submarine hydrothermal systems and hydrothermal organic geochemistry will be developed as part of course offerings. These will then be improved through student crowd sourcing and posted for public consumption on the Internet. Results of the project will be applicable broadly across the academic sector into the fields of chemistry and hydrology as well as geothermal and materials science. The fundamental thermodynamic parameters and rate constants to be derived will have a potentially large impact in the chemical and petroleum engineering industrial sectors.