Ore Systems, Tectonics and the Geochemical Cycles of Metals

全球地球化学循环使地球处于或多或少的稳定状态。流体-岩石相互作用是帮助维持这些地球化学循环的一个主要过程，也是近地表环境（如铀矿床）和更深地壳（如造山带金矿）中物质（如元素）运输的原因。虽然我们对某些地球化学旋回，如碳旋回和硫旋回有相当的了解，但对金属的地球化学旋回及其与构造和矿系的关系，我们的认识还存在空白。在全球金属地球化学平衡中发现这些差距或不一致，可能会指出我们对潜在资源的认识存在类似的差距。我的研究旨在通过了解提取、运输和浓缩金属的过程，以及在区域、局部和原子水平上大规模（地壳）流体事件和质量运输之间的关系，来解决这些差距。在这样做的过程中，我计划对科学做出根本性的贡献，这些贡献将应用于环境科学和矿产勘探。

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.