Large-scale quantification of Li in spodumene pegmatite using Laser Induced Breakdown Spectroscopy

Spatially detailed surface analysis of geological samples and drill cores offers insight into element and mineral distributions on large scales, an important information in ore exploration processes. Laser Induced Breakdown Spectroscopy (LIBS) is an uprising technology that allows fast in-situ geochemical measurements directly on a sample surface under atmospheric conditions. Since nearly no sample preparation is needed, the technology is suitable for spatially-resolved measurements on large samples such as drill cores. LIBS also allows the detection of light elements like Li, an important element due to the increasing amounts needed for battery production of all kinds. Nevertheless, interpreting LIBS data is challenging, since various physical and chemical matrix effects do not allow a straightforward analysis of heterogeneous material. Especially quantification remains problematic. We used a LIBS drill core scanner (Nd:YAG Q-switched 20Hz 1064nm laser and a high-resolution 285-964nm Echelle spectrometer) for 1D profile measurements of 10 consecutive drill core meters from the Rapasaari Li-deposit in Finland. The deposit covers Li-bearing spodumene and muscovite pegmatite, from which five large samples were measured with high resolution in 2D, as well. Small-scale ICP-MS mappings were used as pixel-matched quantitative reference measurements of Li concentrations. They were successfully co-registrated with the LIBS measurements, which enabled matrix-matched quantification using chemometric quantification models.