Ore Systems, Tectonics and the Geochemical Cycles of Metals

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Global geochemical cycles maintain the Earth in a more-or-less steady state. Fluid-rock interaction is a major process which helps maintain these geochemical cycles and is responsible for mass (e.g., elemental) transport in near-surface environments (e.g., U deposits) as well as the deeper crust (e.g., Orogenic Au deposits). Although we know a considerable amount about certain geochemical cycles such as the carbon and sulfur cycles, there are gaps in our understanding of geochemical cycles of metals and their relation to tectonics and ore systems. Identifying these gaps or inconsistencies in the global metal geochemical balance may point to similar gaps in our knowledge of potential resources. My research aims to address these gaps by understanding the processes that extract, transport and concentrate metals, and the relationship between large-scale (crustal) fluid events and mass transport at the regional, local and atomic levels. In so doing, I plan to make fundamental contributions to science that will find application in the environmental sciences and mineral exploration. Most elements of economic value (e.g., Au, U) occur in the Earth's crust in concentrations of a few parts per million (ppm) or lower. For these metals to be economically extractible they must accumulate in the Earth's crust in sufficient concentrations. Therefore, several processes must occur at the appropriate time. Isotopes can provide information on these processes that distribute and concentrate metals in natural systems. The utility of using the fractionation of traditional light stable isotopes (H, C, O, N, and S) and Pb as tracers of fluid-solid interactions, geothermometers, mass transport and contaminants is well established, and radiogenic isotopes (e.g., U-Pb) are useful chronometers of fluid events. However, the use of non-traditional light isotopes such as B and Li, and transition- (e.g., Fe) and other heavy-metal isotopes (e.g., U), is in its infancy. Therefore, during this funding period my students and I plan to combine traditional and non-traditional isotope systems to address some key questions related to uranium ore systems. We plan to combine field observations and analysis of natural samples to verify our observations and interpretations. The novelty of the work is that diverse mineralogical and isotopic techniques are combined to provide insights into the genesis of mineral deposits. 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.