Trace-element imaging at macroscopic scale in a Belgian sphalerite-galena ore using Laser-Induced Breakdown Spectroscopy (LIBS)

Abstract

Laser-Induced Breakdown Spectroscopy (LIBS) is a fast in-situ analytical technique based on spectroscopic analysis of atomic emission in laser-induced plasmas. Geochemical mapping at macroscopic scale using LIBS was applied to a decimetric Zn-Pb ore sample from east Belgium, which consists of alternating sphalerite and galena bands. A range of elements was detected with no or minimal spectral correction, including elements of interest for beneficiation such as Ge, Ag and Ga (although the detection of gallium could not be confirmed), and remediation, especially As and Tl. The comparison between LIBS and Energy Dispersive Spectroscopy (EDS) analyses showed that LIBS intensities reliably relate to elemental concentration although differences in spot size and detection limits exist between both techniques. The elemental images of minor and trace elements (Fe, Cu, Ag, Cd, Sb, As, Tl, Ge, Ni and Ba) obtained with LIBS revealed with great detail the compositional heterogeneity of the ore, including growth zones that were not visible on the specimen. In addition, each mineral generation has a distinct trace-element composition, reflecting a geochemical sequence whose potential metallogenic significance at the district scale should be addressed in further work. Although qualitative and preliminary, the obtained LIBS dataset already produced a wealth of information that allowed to initiate discussion on some genetical and crystallochemical aspects. Above all, LIBS appears as a powerful tool for screening geochemically large samples for the selection of zones of particular interest for further analysis.

Laser-Induced Breakdown Spectroscopy Imaging for Material and Biomedical Applications: Recent Advances and Future Perspectives

“…In a study from Fabre et al, megapixel elemental maps with a spatial resolution of 15 μm of more than 20 elements were produced, most with a sensitivity close to the ppm level. 101 In another study, Baele et al successfully correlated EDS quantitative measurements with LIBS imaging signals for 8 elements, including As and Sb, 102 as shown in Figure 4b. However, quantification appears challenging when no standards are available, as external methods may not be sensitive enough for some elements.…”

“…Belg . 2021 , 24 , 125–136, Baele, J.-M.; Bouzahzah, H.; Papier, S.; Decrée, S.; Verheyden, S.; Burlet, C.; Pirard, E.; Franceschi, G.; Dejonghe, L. Trace-Element Imaging at Macroscopic Scale in a Belgian Sphalerite-Galena Ore Using Laser-Induced Breakdown Spectroscopy (LIBS) (ref ). (c) Elemental and plasma-induced luminescence maps from a blue kyanite crystal.…”

“…In another study, Baele et al successfully correlated EDS quantitative measurements with LIBS imaging signals for 8 elements, including As and Sb, as shown in Figure b. However, quantification appears challenging when no standards are available, as external methods may not be sensitive enough for some elements.…”

Enhanced Laser-Induced Breakdown Spectroscopy for Heavy Metal Detection in Agriculture: A Review

“…In LIBS analysis, qualitative and quantitative analysis can be performed based on the elemental spectral lines’ information and the elements’ chemical reference values. The characteristic spectral lines of specific elements can be found in the Atomic Spectral Database (ASD) of the National Institute of Standards and Technology (NIST) [ 35 , 36 ]. In quantitative analysis, in addition to traditional methods, such as internal and external scaling [ 37 ], machine learning methods, such as support vector machines (SVM) [ 38 ], principal component analysis (PCA) [ 39 ], the back propagation (BP) neural network [ 40 ], and partial least square (PLS) [ 41 ], are also becoming widely used.…”

Metal deportment in Pb-Zn mine wastes from a historic tailings pond, Plombières, East Belgium

“…The mine waste material represents residues of the pyrometallurgical processing of Mississippi Valley-type (MVT) ores (Dejonghe et al, 1993;Kucha et al, 1996). The primary mineralogy of the Plombières ore consisted mostly of the sulfide minerals galena (PbS), sphalerite (ZnS) and pyrite/marcasite (FeS2), with gangue minerals including quartz and carbonates (Dejonghe et al, 1998;Baele et al, 2021). Bulk geochemical analysis (XRF) showed that the different types of mine waste material dominantly consist of SiO2, Al2O3 and Fe2O3, while the lead and zinc contents vary from 51 ppm to 24 wt % and from 10 ppm to 10.1 wt %, respectively (Bevandić et al, 2021).…”