HIGH-RESOLUTION, GROUND-BASED HYPERSPECTRAL IMAGING OF GEOLOGICAL OUTCROPS AND HAND-SPECIMENS

Our ongoing research is integrating high resolution hyperspectral data in visible near-infrared and shortwave-infrared wavelengths, and high resolution terrestrial laser scanning (TLS) for the study of geological outcrops. Ground-based hyperspectral sensors could scan the objects at close range, thus provide very high spatial resolution (millimeters to centimeters) with the potential to characterize rocks and minerals with great precision. Several case studies demonstrating successful use of TLS and hyperspectral data will be presented.

For one such study, a couple of mineral alteration zones with gold mineralization are identified using multispectral remote sensing data. These alteration zones are associated with sulphide mineralization in quartz veins in volcanic, metavolcanic, and dioritic rocks near Shyok Suture Zone in northern areas of Pakistan. Representative samples from the alteration zones are collected and analyzed. The reflectance spectra of the rock samples are obtained by a spectroradiometer, samples are also scanned using the Specim visible-near infrared and shortwave infrared hyperspectral sensors in the laboratory. Subsequently, the data are evaluated in an empirical framework. Comparison of reflectance spectroscopy and imaging spectroscopy data provide a method for evaluating presence and spatial distribution of minerals in the rock samples with high resolution. The minimum noise fraction transformation and spectral angle mapper algorithms have been employed for evaluation of high-resolution imaging spectroscopy data. Dominant minerals in the alteration zone include malachite, azurite, pyrite and chalcopyrite. Remote sensing results are confirmed by Quantitative Evaluation of Minerals by SCANning electron microscopy (QEMSCAN). Geochemical analysis of samples for gold concentrations show promising results with gold concentration up to 90 ppm. Further work is in progress to evaluate economic feasibility of these sites and to locate more mineralization zones.