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

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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.