Department of Earth Sciences, University of Toronto, Toronto, ON, M5S 3B1, Canada.
Department of Earth Sciences, University of Oxford, Oxford, OX1 3AN, UK.
Nat Commun. 2022 Jun 30;13(1):3768. doi: 10.1038/s41467-022-31412-2.
Deep within the Precambrian basement rocks of the Earth, groundwaters can sustain subsurface microbial communities, and are targets of investigation both for geologic storage of carbon and/or nuclear waste, and for new reservoirs of rapidly depleting resources of helium. Noble gas-derived residence times have revealed deep hydrological settings where groundwaters are preserved on millions to billion-year timescales. Here we report groundwaters enriched in the highest concentrations of radiogenic products yet discovered in fluids, with an associated Kr excess in the free fluid, and residence times >1 billion years. This brine, from a South African gold mine 3 km below surface, demonstrates that ancient groundwaters preserved in the deep continental crust on billion-year geologic timescales may be more widespread than previously understood. The findings have implications beyond Earth, where on rocky planets such as Mars, subsurface water may persist on long timescales despite surface conditions that no longer provide a habitable zone.
在地球的前寒武纪基底岩石深处，地下水可以维持地下微生物群落，是地质封存碳和/或核废物以及氦等迅速枯竭资源新储层的研究目标。稀有气体衍生的停留时间揭示了深层水文环境，地下水在数百万到十亿年的时间尺度上得以保存。在这里，我们报告了富含放射性产物的地下水，这是迄今为止在流体中发现的最高浓度，同时自由流体中的 Kr 过剩，停留时间>10 亿年。这种卤水来自南非地表以下 3 公里的金矿，表明保存在大陆地壳深处的古老地下水可能比以前认为的更为普遍。这些发现不仅对地球有意义，在火星等岩石行星上，尽管表面条件不再提供宜居区域，但地下水可能会在很长时间内持续存在。
