"Follow the Water": Controls on the Distribution and Preservation of Habitability from Water-Rock Interactions in the Earth's Deep Crust

作为科学家、工程师、政策制定者和公众公民，我们对地球的理解可能会在不经意间受到这样一个事实的限制：人类生活只是这个蓝色星球表面上的一层薄薄的饰面。基本的挑战仍然涉及地球地下化学、物理（和生物）相互作用的复杂性，特别是地下水的性质，即地球深层水圈。例如，地球化学家长期以来一直依赖于流体包裹体——包裹在宿主岩石和断裂矿物中的流体和气体的微观时间胶囊——来获取保存下来的成矿流体、变质流体、古代大气和水圈残留物的样本。直到最近，宏观的（流动的）地下水被认为只反映了水岩反应和地球历史的更年轻的时期，这是由于大量较年轻的流体从地表重新注入造成的稀释。在过去的6年里，我们探索并扩大了我们对前寒武纪地壳地下水的深度、分布、储存和停留时间的了解，我们的团队通过工作矿山和世界各地的地下研究实验室获取了占地球大陆岩石圈70%的前寒武纪地壳地下水。我们发现的地下水保存了数百万年甚至数十亿年前的成分，为了解地球水圈和大气的演变提供了新的样本，挑战了我们对地球可居住性的理解，并告诉我们在火星下以及太阳系其他地方的冰冷行星和卫星上可能存在的地下水和可居住性。作为一名同位素地球化学家和水文地质学家，我在这个项目中的领导作用和核心贡献是提供来自地球化学和同位素特征的见解、解释和关键约束(使用记录化学和生物介导反应历史的活性CHO元素；以及保守的稀有气体（确定不同来源成分的起源和混合），以确定地球深处的水文地质和可居住性的流体和气体。除了推进对NSE的基本理解，并激发公众对地球深部的想象之外，这项研究还具有重要的实际意义——可能提供有关成矿过程的信息，提供新的技术转让，重新了解深层地下流体的隔离程度（与拟议的核废料处理和碳捕获和储存项目有关）；并为人类探索和研究大陆岩石圈深处时将遇到的高盐深层地下流体和气体的性质提供了新的详细信息。这样的程序非常适合地球科学EG 1506的广泛的专业知识

Summary of Proposal ***Our understanding of the Earth, as scientists, engineers, policy makers and public citizens, can inadvertently be constrained by the fact that human life is just a thin veneer on the surface of the Blue Planet. Fundamental challenges remain concerning the complexities of chemical, physical (and biological) interactions in the Earth's subsurface - in particular the nature of subsurface water the Earth's Deep Hydrosphere. For instance, geochemists have long relied on fluid inclusions - microscopic time capsules of fluid and gas encased in host rocks and fracture minerals - to access preserved samples of ore-forming fluids, metamorphic fluids, and remnants of the ancient atmosphere and hydrosphere. Until recently, macroscopic (flowing) groundwaters were thought to reflect only much younger periods of water-rock reaction and Earth history, due to dilution with large volumes of younger fluids recharging from surface. Over the past 6 years we have explored and expanded our understanding of the depth, distribution, storage and residence time of groundwaters in the Precambrian crust that constitutes > 70% of the Earth's continental lithosphere accessed by our team via working mines, and underground research laboratories worldwide. Our discovery of groundwaters that preserve components that are millions and even > a billion of years old provides the opportunity for new suites of samples for understanding the evolution of the Earth's hydrosphere and atmosphere, challenges our understanding of the habitability of Earth, and informs our thinking about possible groundwater and habitability beneath Mars, and on the icy planets and moons elsewhere in the solar system. As an isotope geochemist and hydrogeologist, my leadership and core contributions to this program are to provide insight, interpretation and critical constraints from the geochemistry and isotopic signatures (using both reactive CHO elements that record the history of chemical and biologically-mediated reactions; and conservative noble gases that identify origin and mixing of components of different provenance) for the fluids and gases that define the hydrogeology and habitability of the deep Earth. In addition to advancing fundamental understanding for NSE, and capturing public imagination about the deep Earth, this research has important practical implications - potentially providing information about ore-forming processes, providing new technology transfer re understanding the degree of isolation of deep subsurface fluids (pertinent to proposed nuclear waste disposal, and carbon capture and storage projects); and providing novel detailed information about the nature of highly saline deep subsurface fluids and gases that will be encountered as humans explore and investigate the deep continental lithosphere. Such a program is well suited to the GeoSciences EG 1506's broad expertise.**