Opaque phase petrology and geochemical modeling as a guide to abiotic organic synthesis in the Mid-Atlantic Ridge 15°N area

橄榄岩赋存的热液系统最有趣的方面之一是喷口流体的强烈还原性质，这是由于超镁铁质寄主岩石中的亚铁通过水解产生氢。这些体系中的溶解氢水平很高，因此还原的溶解碳物种比溶解的无机碳更稳定。虽然还不确定有机合成在水热系统中发生的程度，但它对现代和古代水热系统中的微生物生态系统的碳流以及碳和能源具有潜在的重要影响。在这里，我建议用磁性和电子探针技术来确定大西洋中脊北侧蛇纹岩中氧化物/硫化物/自然金属相的矿物学清单。这些相不仅指示蛇纹石化反应的温度和氧化还原条件，也是有机合成反应的重要表面催化剂。样品包括来自Logatchev热液油田和大洋钻探计划(ODP)第209段的蛇纹岩。用电子探针和透射电子显微镜分析了硫化物、氧化物、金属合金和蛇纹石-水镁石相的组成和共生。将使用相岩石学和地球化学模型来估计蛇纹岩作用过程中的温度、流体流量、pH和氧化还原条件。这些约束被用于一个配套项目，以计算水-超镁铁质岩石相互作用的普遍条件下有机合成反应的化学亲和力。

One of the most intriguing aspects of peridotite-hosted hydrothermal systems is the strongly reduced nature of the vent fluids, due to the production of hydrogen by hydrolysis on ferrous iron in the ultramafic host rock. The levels of dissolved hydrogen in these systems are so high that reduced dissolved carbon species are more stable that dissolved inorganic carbon. While it is uncertain to what extent organic synthesis takes place in hydrothermal systems, it has potentially important ramifications for carbon flow and carbon and energy sources for microbial ecosystems within modern and ancient hydrothermal systems. Here, I propose to determine the mineralogical inventory of oxide/sulfide/native metals phases in serpentinites from the Mid-Atlantic Ridge 15ºN area by magnetic and electron microprobe techniques. These phases are not only indicative of temperature and redox conditions during serpentinization, they are also important surface catalysts for organic synthesis reactions. Samples include serpentinites from the Logatchev hydrothermal field and from Ocean Drilling Program (ODP) Leg 209. Electron microprobe and transmission electron microscope analyses are employed to characterize the composition and intergrowth of sulfides, oxides, metal alloys as well as serpentine-brucite phases. Phase petrology and geochemical modelling will be employed to estimate temperature, fluid flux, pH, and redox conditions during serpentinization. These constraints are used in a companion project to calculate the chemical affinities of organic synthesis reactions under the prevailing conditions of water-ultramafic rock interaction.