Quantitative chemical profiling of coal using core-scanning X-ray fluorescence techniques

• Detailed profiles of inorganic elements have been measured in bituminous coal cores
• Energy-dispersive XRF data obtained at intervals of 200 μm; quantified by calibration
• Profiles integrated with optical and X-radiograph images for geological interpretation
• Element quantifications cross-checked against conventional chemical analysis data
• Data useful in coal quality evaluation, mineralogical studies and geochemical research

A study has been carried out to test the possibility of measuring detailed quantitative profiles of the abundance of different inorganic elements through exploration cores of coal seams using automated energy-dispersive X-ray fluorescence (ED-XRF) core scanning instrumentation. Such an approach has potential application for rapidly determining the distribution of mineral matter in a coal seam, identifying horizons at which particular elements (such as phosphorus) may be concentrated, evaluating in detail the relationships between different elements in the coal, and maximising the data available to guide broader-scale sampling for conventional analysis programmes.Profiling was carried out on a series of segments from a 60 mm diameter core of the Goonyella Middle seam in the northern Bowen Basin of Queensland, using an Itrax core scanner (Cox Analytical, Sweden). The scanning process included high resolution optical imaging, X-radiography, and ED-XRF spectroscopy covering the principal major elements, with XRF spectra being obtained at intervals of 200 μm along the axis of each core. A series of calibration curves derived from separately-scanned pressed pellets of reference coals was used to determine the concentration of each element for each step in each sample, allowing a set of quantitative element profiles to be created for each core segment. These were evaluated in conjunction with the relevant X-radiographs and optical images to provide an integrated basis for assessing the variations in inorganic element characteristics through the core sections. The results were also compared to conventionally-determined chemical and mineralogical data for a representative core, to confirm the validity of the quantifications developed.