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地表以下2.8公里处发现了地球上一些最孤立的微生物生态系统，这些微生物生态系统位于南非前寒武纪岩石勘探钻孔排放的含盐裂缝沃茨中（Lin等人，2006，Science）。像海底的热液喷口一样，这些深断裂沃茨是地球上最富H2的环境，并且是广泛的水-岩石反应的其他产物的储存库，包括非生物成因的碳氢化合物和放射成因的惰性气体（舍伍德罗拉尔等人，2002 Nature）。我们在南非的团队最近的结果，以及我们在加拿大前寒武纪地盾上的站点的初步结果表明，这些自由流动的断裂沃茨中的惰性气体成分的年龄超过20亿年-证明了这些地面沃茨在以前未被认识的时间尺度上与表面光球隔离（Lippmann-Pipke，舍伍德Lollar等人，2011化学地质学;荷兰，舍伍德Lollar等人，2012年，在Nature上修订）。 虽然已经了解了很多，但这些令人兴奋的结果已经开辟了更多有趣的科学问题，这些问题对于理解地球上生命的分布和深层地下的可居住性至关重要;深层地壳流体和还原气体（甲烷，氢）的起源和年龄;以及地球化学（地下水-岩石蚀变反应）可以支持地下生命的程度。这个发现研究计划的重点是加拿大地盾上前寒武纪岩石中尚未调查过的地点，重点是解决上述问题-它们对我们理解这个星球的可居住性，地球上生命的进化有着深远的影响;以及其他行星或卫星上地下生命的潜力。

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.