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

点击翻译按钮获取中文摘要

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.**