Spectroscopic mineral - chemical analysis of drill cores: Development of fast 2D LIBS, EDXRF and hyperspectral scanning with application to outstanding problems of the Bushveld Complex layered intrusion

激光诱导等离子体光谱分析(LIBS)、高光谱图像分析(HIS)和能量色散显微X射线荧光分析(µEDXRF)等高空间分辨率成像方法为快速、自动化分析钻芯中的矿物化学变化提供了新的可能性，这可能是解释成因模式的关键。该项目的目的是开发、优化和验证这些方法的组合，以连续分析钻芯，并将其应用于布什维尔德杂岩中具有经济意义的单矿物层的矿物学、化学和结构分析(上层带的磁铁矿层，临界区的铬铁矿层)。这一结果将为替代遗传模型提供测试。研究的第二个重点是晚期和岩浆后水熔体和流体对这些层的形成和改造的影响。方法开发将涉及建立有关矿物和矿物固溶体端元的光谱数据库，作为包括辅助相在内的模式矿物学可视化的基础。结合LIBS和µEDXRF数据，可以实现高空间分辨率(分别为200vs.25m)的矿物制图。此外，还可以显示感兴趣的矿物(磁铁矿、铬铁矿、斜方辉石)的化学变化。Li、Be、B等轻元素在LIBS上的分布是指示热液作用的重要指标，许多含水相也可以通过VNIR、SWIR和LWIR的高光谱检查来识别。LIBS、HIS和µEDXRF结果的校准和验证将使用现有数据中成分相似的表征良好的岩石进行，如果需要，还可以使用光学显微镜、电子束微探针、拉曼光谱或激光烧蚀电感耦合等离子体质谱进行额外分析。将开发和验证基于数据同化和人工智能的监测分类和评价工具，以基本上自动化的方式提供从不同方法获得的综合信息。这项研究的结果将有助于对布什维尔德和其他层状侵入体中单矿物层的形成以及晚期含水相的影响提供新的见解。更广泛地说，这项工作将展示连续、准无损扫描方法LIBS、HSI、µEDXRF在一般钻芯分析中的有用性和潜在能力。

High-spatial-resolution imaging methods of laser-induced plasma spectroscopy (LIBS), hyperspectral image analysis (HIS) and energy-dispersive micro-X-ray fluorescence analysis (µEDXRF) opens new possibilities for rapid, automated analysis of mineral-chemical variations in drill cores that can be key for interpretation of genetic models. The aims of this project are to develop, optimise and validate the combination of these methods for continuous analysis of drill cores, to apply them for mineralogical, chemical and textural analysis of mono-mineralic layers of economic signficance in the Bushveld Complex (magnetite layers in the Upper Zone, chromite layers in the Critical Zone). The results will provide tests for alternative genetic models. A second focus of investigation is the influence of late- and postmagmatic aqueous melts and fluids on the formation and modification of these layers. Methods development will involve creation of a spectral database of relevant minerals and mineral solid-solution end-members as the basis for visualization of the modal mineralogy including accessory phases. The combination of LIBS and µEDXRF data enables mineral mapping at high spatial resolution (200 vs. 25m resp.) over the entire examined core section and in addition, chemical variation of minerals of interest (magnetite, chromite, orthopyroxene) can be shown. The LIBS-based distribution of light elements such as Li, Be, B is important as an indicator of hydrothermal influence, and many hydrous phases can also be identified by hyperspectral examinations using VNIR, SWIR and LWIR. Calibration and validation of the LIBS, HIS and µEDXRF results will be done using well-characterized rocks of similar composition from existing data, augmented if needed by additional analyses using optical microscope, electron beam microprobe, Raman spectroscopy or laser ablation inductively coupled plasma mass spectrometry. Data assimilation and artificial intelligence based monitored classification and evaluation tools will be developed and validated to provide the combined information gained from different methods in a largely automated manner. The outcome of this investigation will contribute new insights on formation of monomineral layers in Bushveld and other layered intrusions and on the impact of late hydrous phases. More broadly, the work will demonstrate the usefulness and the potential power of continuous, quasi non-destructive scanning methods LIBS, HSI, µEDXRF for drill core analyses in general.