Isotopic and geochemical tracers of fracture fluids in Precambrian cratons: Time capsules for the deep biosphere

我们的国际团队最近在南非前寒武纪岩石勘探钻孔排放的含盐裂隙水中发现了地球上一些最孤立的微生物生态系统(Lin等人)。2006年，科学)。与海底的热液喷口一样，这些深裂隙水域是地球上最富含氢的环境，是广泛的水-岩石反应的其他产物的储存库，包括非生物成因碳氢化合物和放射性惰性气体(Sherwood Lollar等人，2002年《自然》)。我们在南非的团队的最新结果，以及我们在加拿大前寒武纪地盾现场的初步结果表明，这些自由流动的裂隙水中的惰性气体成分已有20多亿年的历史--证明了这些地下水与地表光球层在以前未被识别的时间尺度上的隔离(Lippmann-Pipke，Sherwood Lollar等人，2011年化学地质学；Holland，Sherwood Lollar等人，2012年在《自然》杂志上修订)。虽然已经学到了很多，但这些令人兴奋的结果揭示了更有趣的科学问题，这些问题对于了解地球上生命的分布和深层地下的宜居性、深部地壳流体和还原气体(甲烷、氢)的来源和年龄以及地球化学(地下水-岩石蚀变反应)支持地下生命的程度具有根本重要性。这个发现号研究项目聚焦于加拿大地盾前寒武纪岩石中尚未调查的地点，专注于解决上述问题--它们对我们理解这颗行星的宜居性、地球上生命的演化以及其他行星或卫星上亚表面生命的潜力具有深远的影响。

Some of the most isolated microbial ecosystems on Earth have recently been discovered by our international team at 2.8 km below the Earth's surface in saline fracture waters discharging from exploration boreholes in the Precambrian rocks of South Africa (Lin et al. 2006, Science). Like the hydrothermal vents on the ocean floor, these deep fracture waters are the most H2-rich environments on the planet, and are repositories of other products of extensive water-rock reaction including abiogenic hydrocarbons and radiogenic noble gases (Sherwood Lollar et al., 2002 Nature). Recent results by our team in South Africa, and preliminary results at our sites on the Precambrian Shield in Canada, indicate components of the noble gases in these free flowing fracture waters are more than 2 Billion years old - attesting to the isolation of these groundwaters from the surface photosphere on a previously unrecognised timescale (Lippmann-Pipke, Sherwood Lollar et al., 2011 Chemical Geology; Holland, Sherwood Lollar et al., 2012 in revision at Nature). While much has been learned, these exciting results have opened up yet more intriguing scientific questions of fundamental importance for understanding the distribution of life on Earth and the habitability of the deep subsurface; the origin and age of deep crustal fluids and reduced gases (methane, hydrogen); and the degree to which geochemistry (water-rock alteration reactions in the subsurface) can support subsurface life. Focused on as yet under investigated sites in Precambrian rocks on the Canadian Shield, this Discovery research program is focused on addressing the above questions - with their profound implications for our understanding the habitability of this planet, the evolution of the life on Earth; and the potential for life in the subsurface on other planets or moons.