Minerals such as silicates, aluminosilicates (feldspar), magnesium silicates (serpentine) and olivines are among the most commonly encountered in the environment. Airborne mineral mapping of these minerals using conventional visible-near infrared (VNIR, 0.4-1.4 μm) and shortwave infrared (SWIR, 1.4-3 μm) sensors can be very challenging, since the Si-O bounds are featureless or exhibit very weak spectral features in these spectral ranges. The fundamental vibrations associated with most functional groups composing the different ores mostly occur in the thermal infrared (TIR, 8-12 μm) spectral range.
In order to illustrate the benefits of thermal infrared hyperspectral imaging (HSI) for mineral mapping, an airborne survey was carried out over an open-pit mine in the Thetford Mines (Qc, Canada) area. The results show how the high spectral resolution data provided by the Telops Hyper-Cam airborne system facilitates temperature emissivity separation (TES) and atmospheric correction in order to retrieve a thermodynamic temperature map of the area and its associated spectral emissivity datacube. Mineral mapping of various minerals such as lizardite, serpentinite and quartz was achieved through linear unmixing of the emissivity data using reference emissivity curves found in spectral libraries. The results illustrate the potential of TIR HSI for airborne mapping of silicate minerals.