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Texture and grain size distribution of minerals in drill cores based on µXRF mapping (spatially resolved X-ray fluorescence spectroscopy)

µXRF is a versatile technique that has been used in various geoscientific fields, particularly for the mapping of larger hand specimen or drill cores. It is easy to use, non-destructive and requires only little sample preparation, enabling the acquisition of 2D element distribution and mineral identification via EDX spectra. However, a limitation is the diffraction of the X-ray beam by the crystal lattice, which can produce peaks that overlap with actual element peaks, thereby affecting chemical quantification and mineral identification. Previous research, such as Nikonow et al. (2016), has demonstrated methods to eliminate these diffraction peaks from µXRF spectra. Additionally, diffraction can be used to identify individual grains within a mono-mineralic domain, such as quartz, without the need for thin section preparation. Since diffraction depends on the angle between the crystal lattice and the X-ray beam, differently oriented grains will produce diffraction peaks at different energies in the spectrum and can be distinguished from each other in the energy-dispersive µXRF spectrum. This technique enables not only the identification of optically similar minerals in the drill core (e.g. magnetite and ilmenite), but also the extraction of grain shapes and measurement of their 2D size, area, and orientation in the cutting plane and allows for quantitative textural analysis, helping to understand e.g. igneous processes (Higgins 1998). The application of this method is demonstrated on drill core sections from magnetitite layers of the Upper Zone of the Bushveld Igneous Complex, South Africa.

Details

Author
Wilhelm Nikonow1, Dieter Rammlmair2
Institutionen
1Bundesanstalt für Geowissenschaften und Rohstoffe (BGR), Germany; 2Leibniz Universität Hannover, Germany
Veranstaltung
GeoSaxonia 2024
Datum
2024
DOI
10.48380/0kz9-1f25