Development of in-situ geochronology methods with applications to ore deposits

这项研究的重点将是开发适用于金属矿床原位U-Pb年代学的新的微观分析技术。具体地说，这项研究将致力于使用现成的玻璃参考标准来改进激光烧蚀电感耦合等离子体质谱(LA-ICPMS)对含铀矿物的U-Pb测年。这种方法在最近的初步实验中被证明是成功的，进一步改进这种方法可能会对当代矿藏中矿物测年的方法产生深远影响。特别是，这种方法可能非常适合于测定一套高铀矿物的年龄，如含铁、钛和稀土的氧化物、稀土碳酸盐和稀土硅酸盐，这些矿物可以形成与岩浆-热液矿床有关的蚀变组合。这些矿物可能含有很高的铀浓度，其放射性衰变会使这些矿物在原子尺度上变成变质物或玻璃样。因此，它们的行为可能与我建议使用的玻璃参考材料非常相似。由于激光烧蚀过程中矿物的行为不能仅用理论来准确预测(由于结晶度和化学成分的变化)，因此需要进行一系列经验测量来记录每种感兴趣的矿物的行为。因此，这项研究将涉及一系列综合的微量分析研究，使用旨在评估潜在目标矿物的化学、结晶度和铀-铅同位素组成的仪器。这些研究的结果将被用于优化激光消融设置，以获得精确和准确的U-Pb数据。这种方法的准确性将在侵入岩和相关矿化的年龄独立已知的地质环境中进行测试。因此，这项研究可以为研究目前超出常规副矿物地质年代学范围的金属矿床系统的时间和时间尺度打开大门。

The research will focus on developing new micro-analytical techniques applicable to in-situ U-Pb geochronology in metallic ore deposits. Specifically, the research will endeavour to refine laser-ablation inductively-coupled plasma mass spectrometry (LA-ICP-MS) U-Pb dating of U-bearing minerals using off-the-shelf' glass reference standards. This approach has proven successful in recent preliminary experiments and refining the method further could have a profound impact on contemporary approaches to dating minerals in ore deposits. In particular, the approach may be well-suited to dating a suite of high-U minerals such as Fe-, Ti-, and REE-bearing oxides, REE-carbonates, and REE-silicates that can form in alteration assemblages associated with magmatic-hydrothermal ore deposits. These minerals can contain high U concentrations, the radioactive decay of which can render the minerals metamict or glass-like' at the atomic scale. Hence, they may behave very similarly to the glass reference materials I propose to use. Because the behaviour of minerals during laser ablation cannot be accurately predicted using theory alone (owing to variations in crystallinity and chemistry) a series of empirical measurements needs to be made to document the behaviour of each mineral of interest. Thus, this research will involve a series of integrated microanalytical studies using instruments designed to assess the chemistry, crystallinity, and U-Pb isotopic composition of potential target minerals. The results from these investigations will be used to optimize laser ablation settings to achieve precise and accurate U-Pb dates. The veracity of this approach will be tested in geological settings where the age of the intrusions and associated mineralization is independently known. This research could, therefore, open the door to studies of the timing and timescales of metallic ore deposits systems that are currently beyond the scope of conventional accessory mineral geochronology.