Department of Earth Sciences, 22 Russell Street, University of Toronto, Toronto M5S 3B1, Canada.
Department of Geosciences, Guyot Hall, Princeton University, Princeton, New Jersey 08544, USA.
Nature. 2014 Dec 18;516(7531):379-82. doi: 10.1038/nature14017.
Microbial ecosystems can be sustained by hydrogen gas (H2)-producing water-rock interactions in the Earth's subsurface and at deep ocean vents. Current estimates of global H2 production from the marine lithosphere by water-rock reactions (hydration) are in the range of 10(11) moles per year. Recent explorations of saline fracture waters in the Precambrian continental subsurface have identified environments as rich in H2 as hydrothermal vents and seafloor-spreading centres and have suggested a link between dissolved H2 and the radiolytic dissociation of water. However, extrapolation of a regional H2 flux based on the deep gold mines of the Witwatersrand basin in South Africa yields a contribution of the Precambrian lithosphere to global H2 production that was thought to be negligible (0.009 × 10(11) moles per year). Here we present a global compilation of published and new H2 concentration data obtained from Precambrian rocks and find that the H2 production potential of the Precambrian continental lithosphere has been underestimated. We suggest that this can be explained by a lack of consideration of additional H2-producing reactions, such as serpentinization, and the absence of appropriate scaling of H2 measurements from these environments to account for the fact that Precambrian crust represents over 70 per cent of global continental crust surface area. If H2 production via both radiolysis and hydration reactions is taken into account, our estimate of H2 production rates from the Precambrian continental lithosphere of 0.36-2.27 × 10(11) moles per year is comparable to estimates from marine systems.
微生物生态系统可以通过地球内部和深海喷口的产氢水岩相互作用来维持。目前，通过水岩反应（水合作用）对海洋岩石圈每年产生的全球氢气量的估计范围在 10^11 摩尔左右。最近对前寒武纪大陆内部咸水断裂水中的探索已经确定了富含氢气的环境，如热液喷口和海底扩张中心，并表明溶解的氢气与水的辐射分解之间存在联系。然而，根据南非威特沃特斯兰德盆地的深部金矿对区域氢气通量的推断表明，前寒武纪岩石圈对全球氢气产量的贡献微不足道（每年 0.009×10^11 摩尔）。在这里，我们对从前寒武纪岩石中获得的已发表和新的氢气浓度数据进行了全球汇编，并发现前寒武纪大陆岩石圈的氢气生产潜力被低估了。我们认为，这可以解释为没有考虑到其他产氢反应，如蛇纹石化作用，以及没有对这些环境中的氢气测量进行适当的比例调整，以说明前寒武纪地壳占全球大陆地壳表面积的 70%以上。如果考虑到辐射分解和水合反应都能产生氢气，那么我们对前寒武纪大陆岩石圈每年产生 0.36-2.27×10^11 摩尔氢气的估计与海洋系统的估计相当。
