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

开发原位地质年代学方法及其在矿床中的应用

• 批准号: RGPIN-2016-04320
• 负责人: McFarlane, Christopher
• 金额: $ 1.75万
• 依托单位: University of New Brunswick
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2017
• 资助国家: 加拿大
• 起止时间: 2017-01-01 至 2018-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=633697
• 关键词: Development; situ; geochronology; methods; applications

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.

研究的重点是开发适用于金属矿床现场U-Pb年代学的新的微分析技术。具体而言，该研究将努力完善激光烧蚀电感耦合等离子体质谱法（LA-ICP-MS）U-Pb测年的铀含矿物使用“现成的”玻璃参考标准。这种方法在最近的初步实验中证明是成功的，进一步改进这种方法可能会对当代矿床中矿物的定年方法产生深远的影响。特别是，该方法可能非常适合于一套高铀矿物，如铁，钛，稀土氧化物，稀土碳酸盐，稀土硅酸盐，可以形成在与岩浆热液矿床有关的蚀变组合。这些矿物可能含有高浓度的铀，其放射性衰变可以使矿物在原子尺度上变晶或“玻璃状”。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单独使用理论准确预测（由于结晶度和化学性质的变化），因此需要进行一系列经验测量以记录每种感兴趣矿物的行为。因此，这项研究将涉及一系列综合微分析研究，使用旨在评估潜在目标矿物的化学，结晶度和U-Pb同位素组成的仪器。这些调查的结果将用于优化激光烧蚀设置，以实现精确和准确的U-Pb测年。这种方法的准确性将在侵入体和相关矿化的年龄独立已知的地质环境中进行测试。因此，这项研究可以打开大门，研究的时间和时间尺度的金属矿床系统，目前超出了传统的辅助矿物地质年代学的范围。