In search of the biosphere underneath the Lost City hydrothermal vent field using in-situ sulphur and multiple sulphur isotope signatures

拟议的项目计划使用岩相学、原位硫和块状岩石多硫同位素特征作为工具，以确定亚特兰蒂斯地块超镁铁岩中的微生物活动，并进一步深入了解这一橄榄岩赋存的热液系统的热液历史。亚特兰蒂斯地块是一个由超镁铁质和镁铁质岩性组成的海洋核心杂岩。它拥有Lost City热液气田，从碳酸盐-水镁石烟囱中排出高pH值、富含H2的低温流体。这些流体支持碳酸盐烟囱内和附近独特的微生物群落。然而，超镁铁质次表层内的生物活动程度并没有受到很好的限制。最近对亚特兰蒂斯地块进行的IODP第357次探险利用浅层钻探技术，从Lost City热液油田附近的浅层地下恢复了超镁铁质和镁铁质岩性。这些样品为研究超镁铁质地下发生的过程提供了一个特殊的机会。在拟议的研究中，将使用块状岩石的多种硫同位素(32S、33S、34S、36S)和单个硫化物颗粒的原位硫同位素特征来识别过去微生物活动的过程，如微生物硫酸盐还原，并测量与蛇纹岩作用相关的各种非生物成因过程。硫同位素数据将与拟议研究中进行的矿物学观察(例如硫化物矿物组合)以及从实验科学党其他成员收集的数据结合在一起。357，提供了对碳酸盐和蛇纹岩脉中保存的流体化学的洞察。这将对超镁铁质岩石内微生物活动的程度提供更好的限制，并可能为了解有利于地下生物圈微生物活动的条件提供新的见解。

The proposed project plans to use petrography, in-situ sulphur and bulk rock multiple sulphur isotope signatures as tools to identify microbial activity in ultramafic rocks of the Atlantis Massif and to give further insights into the hydrothermal history of this peridotite-hosted hydrothermal system. The Atlantis Massif is an oceanic core complex made up of ultramafic and mafic lithologies. It hosts the Lost City hydrothermal field, which vents high-pH, H2-rich, low-temperature fluids from carbonate-brucite chimneys. These fluids support a unique microbial community within and in the vicinity of the carbonate chimneys. However, the extent of biological activity within the ultramafic subsurface is not well constrained. The recent IODP Expedition 357 to the Atlantis Massif recovered ultramafic and mafic lithologies from the shallow subsurface of the vicinity of the Lost City hydrothermal field using shallow drilling techniques. These samples provide an exceptional opportunity to study the processes that take place within the ultramafic subsurface. In the proposed study bulk rock multiple sulphur isotopes (32S, 33S, 34S, 36S) and in-situ sulphur isotope signatures of individual sulphide grains will be used to identify processes of past microbial activity, such as microbial sulphate reduction, and to measure various abiogenic processes associated with serpentinization. The sulphur isotope data will be combined with mineralogical observations performed in the proposed study (e.g. sulphide mineral assemblages) as well as data collected from other members of the science party of Exp. 357 that provide insight into the fluid chemistry preserved within carbonate and serpentine veins. This will provide better constraints on the extent of microbial activity within the ultramafic rocks and may provide new insights into the conditions that favour microbial activity in the subsurface biosphere.