Hyperspectral analysis of lacquer peel profiles as quasi-in-situ analysis for tailings exploration

Three lacquer peel profiles were prepared from a copper tailings deposit in Central Chile. The peels were taken from two sides at varying depths of the tailings heap. Parallel to that, samples were taken from each layer within the peels for bulk XRF analysis and particle size analysis. The peels were analysed by Hyperspectral Imaging (HSI, VNIR- SWIR, 400 – 2500 nm wavelength) with the Specim SisuRock system and µXRF mapping using M4 Tornado Plus from Bruker for chemical comparison. The lacquer peel method worked well for sandy tailings with the polyvinyl alcohol Mowiol as glue with a peel size of 50 x 30 cm. All peels were stable, transportable and ready to be measured by HSI after about one day of drying. The HSI data shows that reflectance of the different material layers within the peels is correlated with particle size data from sieving (Camsizer, Retsch and Sedigraph, Micromeritics). This is important information for a possible reprocessing of copper sulfides, since tailings deposition works as a particle sorting process and, flotation efficiency depends on particle size. Furthermore, endmember classes were extracted from the HSI data using the Pixel Purity Index on lacquer profile 2, which were used to classify the remaining profiles. The HSI classification was registered to the µXRF mappings and the HSI classes were attributed the copper concentration from µXRF. With this information, zones of copper enrichment could be localized using the HSI data in combination with µXRF. This process is also applicable on tailings drill cores.