Benjamin S. Andrew and Shaun L. L. Barker report that the composition of carbonate minerals infilling hydrothermal veins can vary as a function of factors including fluid chemistry, temperature and pressure. If effectively quantified, carbonate vein chemistry can represent an important tool in mineral exploration. They present a method for determining carbonate vein chemistry using portable X-ray fluorescence analysis ( pXRF) utilising matrix matched certified reference materials (CRMs) to assess pXRF analyser performance, before establishing strict QA/QC procedures, along with linear calibration equations for Mg, S, Mn, Fe, Zn, Sr and Pb. However, low concentrations of mineralization-related elements in commercially available CRMs meant raw S, Zn and Pb concentrations determined for case study samples could not be reliably corrected.
Their new workflow was then applied to carbonate vein samples collected from Mount Isa, Northwest Queensland, Australia. Though complexity of this system limited the interpretation of results, the case study showed that pXRF can also be used to identify veins with multiple generations of carbonate infill. Portable X-ray fluorescence analyses, used in conjunction with robust QA/QC processes is a powerful tool that can quickly and cost-effectively inform decisions during exploration programs.
Carbonate minerals are ubiquitous vein-infilling materials associated with many styles of hydrothermal mineralization, including skarn, Carlin-type gold, mesothermal gold, porphyry, low-sulphidation epithermal gold and Mount Isa-type sediment hosted Cu deposits. Commonly considered gangue minerals of little or no significance, understanding how the composition of carbonate minerals can vary as a function of fluid chemistry, temperature and pressure means that carbonate minerals could be an important tool in mineral exploration. Recognition that the composition of calcite veins differed around ore deposits dates back to at least the late 1950s, with Stone (1959) recognizing that the very well-known Naica carbonate replacement deposit in Mexico contained fluorescent calcite in the regions adjacent to Pb-Zn-Ag mineralization, whereas distal marbles did not fluoresce.
Modern, handheld analytical technology such as portable X-ray fluorescence ( pXRF) allows direct and quantitative chemical measurements to be made in the field. These can be used to support UV fluorescence observations, which are common mineral industry practise. Here we present a method for quantifying carbonate vein chemistry using pXRF analysis, which can be quickly and cost-effectively employed during mineral exploration.
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