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流体含有溶解的有机化合物，这些有机化合物在通过洋壳的过程中暴露在高温高压环境中，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转化为其他有机分子。 在地球形成之初，海洋地壳中发生的类似反应和转变可能在形成地球生命所必需的有机成分方面发挥了重要作用。 本研究进行了一系列高温高压实验（分别为200至350 ℃和70至100 MPa），其中充分表征的、溶解的、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，以检查有机化合物及其转化率的变化。 变换和反应速率将被检查作为温度和压力的函数，以及在表面积，电荷分布和半导体性质方面的矿物的催化性能的函数。所得数据将用于确定基本的热力学和动力学参数，这些参数可用于作出和检验预测，并研究水-岩相互作用和矿物催化作用对海洋地壳中有机分子形成的影响。 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。 将使用热液金袋（狄克逊弹）和静态金胶囊实验装置。 实验将使用水形态建模代码（例如，SUPCRT和EQ 3/6）。将通过高精度气相色谱和气相色谱质谱法分析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。 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，实验是成功的，并产生可解释的结果。 该研究的更广泛的影响包括通过利用该研究来改变亚利桑那州立大学的本科生地球化学，有机化学和天体生物学学生的教学方式，从而实现研究和教育的重大整合。 将把研究纳入课程，并将制作一系列关于海底热液系统和热液有机地球化学专题的播客和视频，作为课程的一部分。然后将通过学生群体采购改进这些信息，并将其张贴在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，进入化学和水文学以及地热和材料科学领域。 基本的热力学参数和速率常数推导将有潜在的巨大影响，在化学和石油工程工业部门。

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.