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

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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.