C. Laukamp, M. Legras, R. Didonna, J. Stromberg
Pegmatites are a major source of lithium (Li), a critical metal enabling the transition from a fossil fuel-based energy sector to a sustainable, renewable energy future. The Greenbushes Li deposit in Western Australia is the world’s largest single source of Li, and many other geological environments across Australia are highly prospective for pegmatite-hosted Li deposits. The recent Li rush has highlighted that downstream industries underestimate the complexity of pegmatite-hosted Li deposits, particularly regarding the wide range of Li-bearing minerals present in a single pegmatite. This paper presents an overview of Li-pegmatite mineral assemblages from various regions across Australia, including the southwestern part of Western Australia (WA), hosting Greenbushes, the Eastern Yilgarn Craton (Londonderry), the Pilbara Craton (Pilgangoora, King Col), Queensland’s Georgetown Inlier (Buchanan’s Creek) and the Dorchap Pegmatite Swarm in Victoria. Mineral assemblages from said localities are examined using publicly available hyperspectral drill core analyses (HyLogger3™). These findings are compared with those of Greenbushes drill core C3DD0024, supported by whole-rock geochemistry, Fourier transform infrared (FTIR) spectroscopy and X-ray diffractometry (XRD). Reflectance spectral characteristics of Li-bearing, gangue and alteration minerals are evaluated across the visible near-infrared (VNIR), shortwave infrared (SWIR) and thermal infrared (TIR) wavelength ranges to identify suitable unmixing and feature extraction algorithms for inferring relative mineral abundances and mineral chemistry. Newly developed algorithms—most notably the spodumene abundance index, show a significant correlation with XRD validation and whole-rock geochemistry, demonstrating their effectiveness for mineral detection. Furthermore, the distribution of other Li-bearing minerals, such as petalite and eucryptite, was mapped across the study sites using reference library spectra. The applied hyperspectral mineral abundance and composition indices provide key insights into mineral assemblages and their variations by (1) tracing variations of mineral assemblages within pegmatites and country rocks at centimetre scale, (2) showing that spodumene is predominantly associated with quartz ± plagioclase (without K-feldspar), whereas petalite is mostly associated with quartz and K-feldspar in the absence of plagioclase, (3) confirming that most white mica in pegmatites exhibits an Al-rich composition, (4) demonstrating that phengitic alteration halos around pegmatites are narrow and (5) indicating that chlorite ± biotite ± epidote alteration is common in mafic–ultramafic and metasedimentary wallrocks. The algorithms and workflows provided in this study offer significant potential for expanding applications to large-scale hyperspectral drill core datasets, furthering the understanding of pegmatite genesis, supporting Li-exploration and guiding metallurgical processes by characterising Li-host minerals.