Application of satellite and proximal hyperspectral sensing to target lithium mineralization in volcano-sedimentary deposits: A case study from the McDermitt caldera, USA

This study provides satellite and proximal hyperspectral analyses of lithium (Li)-bearing volcano-sedimentary environments aimed at determining the target absorption features of alteration assemblages to be used as exploration vectors towards analogous Li-mineralized systems. The study was applied at the McDermitt caldera (USA), which hosts volcano-sedimentary Li mineralization in the form of clay minerals originated from the alteration of glass-rich extrusive igneous rocks in endorheic lacustrine basins. The surface-exposed areas of the caldera were investigated using satellite hyperspectral imagery acquired by the German Environmental Mapping and Analysis Program (EnMAP) mission. Satellite data were validated via ground spectroscopy, performed through hyperspectral imaging, complemented by mineralogical and geochemical analyses on specimens deriving from the Jindalee McDermitt Li deposit. The Li mineralization in the Jindalee McDermitt deposit is dominated by a Mg(Li)-smectite (hectorite) + amorphous silica assemblage, showing absorption features at 2306 nm and 2200 nm that can be detected in the spectral range covered by the EnMAP sensor. The analysis of the corresponding hyperspectral feature distribution maps and the comparison with ground control samples, confirmed that the above features together can be effectively used as mineralogical-hyperspectral vectors for Li-prospective areas on a caldera-scale. This spectral footprint was used in the analysis of a similar system that lacks Li mineralization (High Rock caldera complex, USA). Results of this test show that the distinctive 2200 + 2306 nm bands association is lacking at the High Rock caldera complex, which suggests that this spectral footprint can be employed as a mappable criteria to target lacustrine sequences with mineralogical features analogous to those of Li-mineralized volcano-sedimentary deposits.