Advancements in Automated Mineralogy incorporating Micro-XRF technology

摘要

Automated mineralogy has been successfully used in the mining industry since the 1970s. Since that time a variety of companies have developed competing technologies with a range of capabilities, however, with one common aspect in that they are all based on an electron beam (e-beam) system (e.g. scanning electron microscope (SEM) with energy dispersive spectrometers (EDS)). Recent technological advancements mean it is now possible to focus X-rays to a small spot size using a polycapillary lens. Accordingly, a micro-XRF system can be operated using similar parameters as an e-beam system and thus yield results compatable with traditional automated mineralogical analysis. To confirm the micro-XRF's capabilities a variety of case studies are presented, including samples from exotic-Cu deposits in Chile, epithermal Au-Ag deposits in New Zealand, diamond deposits in South Africa, and REE deposits in Chile. The micro-XRF systems have a distinct advantage over e-beam based systems in that the sample preparation is simpler and that larger samples can be analysed. In addition, the x-ray source yields a spectral excitation with significantly lower limits of detection. However, e-beam based systems are able to obtain a smaller beam size. As with traditional automated mineralogical systems, there are fundamental parameters that impact on the mineralogical classification and analytical time; this includes (but is not limited too) x-ray beam excitation (kV and uA), detector active areas (mm~2), pixel spacing (urn), and dwell time (ms).