Mapping copper concentrations in tropical open cast mining fronts from X-ray fluorescence and FAAS techniques: A comparative study

Abstract

Determining copper (Cu) contents and their spatial distribution in tropical open cast mining fronts is crucial for short-term exploitation planning. However, this evaluation in a fast and accurate way can be directly impaired by methods applied. The aim of this work was to assess the analytical performance of portable X-Ray fluorescence (pXRF) for Cu analysis in the mining fronts at the Cu Sossego Mine, in the Carajás Mineral Province, State of Pará, Brazil. For this, 143 drilling samples were collected in mining fronts at the Sequeirinho pit, an area chosen as representative of the heterogeneity of the Cu levels in the deposit of Sossego Mine. The samples were analyzed with three different techniques to determine the Cu levels as follows: pXRF; wavelength-dispersive X-Ray fluorescence (WDXRF); and flame atomic absorption spectrometry (FAAS) after acid digestion with aqua regia (reference method). Results of the three analytical methods were used to generate block models through Leapfroag Geo 6.0 software. Portable XRF data presented a strong positive correlation (>0.70) with the results obtained by the FAAS. In addition, pXRF performed better than WDXRF, with less dispersed values compared to FAAS. Similar distribution maps were generated using the three methods of analysis. After correction, the average Cu content from the pXRF-generated block model was only 0.15% lower than that derived from FAAS data. Therefore, pXRF is a fast, portable, non-destructive, low-cost, accurate and recommendable method for mining front sample analysis and to assist the quality control and geoscience teams in decision-making for feeding the mineral processing plant.