Radionuclide and mass transport in surface and in near-surface environments

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Global geochemical cycles maintain the Earth in a more-or-less steady state. Fluid-solid interaction is a major process which helps maintain these geochemical cycles and is responsible for mass (chemical, elemental, nutrient) transport in near-surface environments (e.g., basin-hosted uranium deposits) as well as the deeper crust (e.g., Archean lode-gold deposits). The importance and potential impact of fluid-solid interaction is not only limited to natural geochemical cycles such as the formation of ore deposits, but also applies to man-made systems that can impact the environment. For example, evaluating the potential impact of fluid-solid interaction on the disposal of high-level radioactive waste in geological repositories and at tailing sites is of global concern and is being actively investigated in many countries. Although the signatures of fluid-solid interactions can be monitored at geologic scales up to those affecting 1000s of km3 of rock (e.g., sedimentary basins, metamorphic haloes around batholiths), these interactions are ultimately governed by processes occurring at the atomic scale. The long term objective of the work is to determine the nature of these processes and the relationship between large-scale (crustal) fluid events and mass transport at the regional, local and atomic level, with implications for both environmental science and mineral exploration. This problem is addressed by detailed studies of the chemical and isotopic composition, paragenesis, and timing (geochronology) of the minerals associated with both mineral deposits and tailing sites using a variety of techniques. The novelty of the work is that diverse mineralogical, and isotopic techniques are combined to provide insights into the genesis of mineral deposits and the release of potentially toxic elements from tailing sites into the environment. This proposal involves extensive training of Highly Qualified Personnel in the form of graduate and undergraduate students, and collaborative work with visiting scientists from other Universities and government institutions. In particular, the collaborative work proposed will give students an unusually wide and diverse background in science, preparing them to develop the research of the future.