Hydrogen and methane from precambrian shield rocks and microbiological sinks for gases produced by water-rock interactions: energy for the deep biosphere

对地球深层地下微生物环境能量基础的科学调查是地质学家、行星科学家、微生物学家和天体生物学家之间跨学科合作的前沿，也是我在地球和环境同位素地球化学研究项目中的一个主要重点。我们对加拿大、南非和芬兰稳定的前寒武纪克拉通进行的深层生物圈研究表明，基于化学合成而不是光合作用的微生物生命并不局限于地球上那些发生显著岩浆或热液活动的地区。在高度裂隙的地质静止的盾构地形中，在数万到数百万年的时间尺度上，低温(&lt；约.200oC)，水-岩相互作用(WRI)可以积累并作为深层微生物群落的底物。特别是，我们正在研究的前寒武纪地盾遗址含有毫米级的溶解H2-水平将这些水域置于地球上最富H2的环境中。我们的研究还涉及开发诊断环境参数，以区分由WRI产生的非生物成因碳氢化合物，与微生物过程产生的碳氢化合物气体，或在沉积盆地天然气矿床中发现的碳氢化合物。这些发现扩大了我们对地球地下环境宜居性的概念，并可能大大增加对地下生物圈相对重要性的估计。出现了两条调查路线，这两条路线将构成本次Discovery应用程序的两个总体目标的基础。目的I：重新评估在北方寒冷环境中微生物CH4同位素特征的框架和目标II：通过对裂隙地下水中溶解的活泼气体和惰性气体的耦合研究，在全球范围内调查前寒武纪盾构岩石中H2和CH4的意义。

Scientific investigations of the energy basis for deep subsurface microbial environments on earth are at the forefront of interdisciplinary collaboration between geologists, planetary scientists, microbiologists and astrobiologists and a major focus of my research program in Isotope Geochemistry of the Earth and Environment. Our deep biosphere research on the stable Precambrian cratons of Canada, South Africa and Finland has demonstrated that microbial life based on chemosynthesis rather than photosynthesis is not limited to those parts of the earth where significant magmatic or hydrothermal activity occurs. In the highly fractured geologically quiescent Shield terrains, over timescales of tens of thousands to millions of years, the products of low temperature (< approx. 200oC) water-rock interaction (WRI) can accumulate and serve as substrate for deep microbial communities. In particular, the Precambrian Shield sites we are studying contain mM levels of dissolved H2 - levels that place these waters among the most H2-rich environments on the planet. Our research also addresses developing diagnostic environmental parameters to distinguish between abiogenic hydrocarbons produced by WRI, from hydrocarbon gases produced by microbial processes, or found in sedimentary basin natural gas deposits. These discoveries have expanded our conception of the habitability of the earth's subsurface environment and may significantly increase estimates of the relative importance of the subsurface biosphere. Two lines of inquiry have arisen that will form the basis for the two Overall Objectives for this Discovery application. Objective I: Reevaluating frameworks for interpreting microbial CH4 isotopic signatures in cold environments in the North and Objective II: Investigating the significance of H2 and CH4 from Precambrian Shield rocks on a global scale through a coupled study of active gases and noble gases dissolved in fracture groundwaters.