Extreme-resolution synchrotron X-Ray fluorescence mapping of ore samples

In order to maximise profit and sustainability of a mining operation, knowledge of the chemistry, mineralogy, texture, and structure of the ore is essential. Continuous advancements in analytical techniques enable studying these features with increasing detail. Synchrotron radiation X-ray fluorescence is unparalleled in its simultaneously high spatial resolution and detection range. Yet, its application in ore geology research and the mining industry is still in its infancy. This study investigated opportunities of extreme-resolution synchrotron X-ray fluorescence mapping of ore samples. Analysis was performed at the NanoMAX beamline at the MAX IV synchrotron facility in Lund, Sweden. The samples investigated are from the Liikavaara Östra Cu-(W-Au) deposit, northern Sweden. Analysis covered areas of several hundreds of μm² in grains of molybdenite, pyrite, and native Bi. Key results included successful mapping of the lattice-bound distribution of Re, Se, and W in molybdenite at 200 nm spot/step size and detection of nanometre inclusions of Au in native Bi at 50 nm spot/step size. Challenges were encountered concerning data acquisition and processing. In order to achieve satisfactory resolution of both light and heavy elements and to limit mapping artefacts, repeated scans of the same area with varied experimental parameters and very thin (quasi-2d) samples are required. For complex geological samples, the software used for analysing spectral data (PyMCA) requires a considerable degree of human examination, which may be a source of error. Overall, synchrotron X-ray fluorescence mapping has a strong analytical potential for ore geology research, in analysing and imaging trace elements that would constitute potential by-products in mining operations. Detailed knowledge of how trace elements occur in the ores will inform the development of appropriate metal extraction programs thus ensuring that a larger part of the ore may then be utilized.