Hyperspectral mapping of regolith materials and landforms for mineral exploration, Olary Domain, South Australia

Abstract

Five runs of HyMap hyperspectral data, flown in November 1998 over a 300 km2 area of the regolith dominated Olary Domain, South Australia, were processed to extract mineral information. RGB colour composites of Minimum Noise Fraction (MNF) transforms and gamma-ray spectrometer data were used to discriminate saprolite exposure from transported alluvial and colluvial materials. Further analysis with orthoimagery and digital elevation models allowed the delineation of the MNF and radiometrics mapped features as regolith-landform units. Endmembers extracted from the processing of the hyperspectral data were identified by comparison with resampled reference library spectra and field spectra collected with a PIMA II spectrometer. The extracted endmembers and the field spectra were used to generate mineral maps using the MTMF (Mixture Tuned Matched Filtering) processing technique in ENVI, which were incorporated into the results from the MNF data to further differentiate the regolith-landform units. The HyMap data were able to differentiate different regolith-landform units and minerals in the AlOH (2.2 μm) region. However, limited success was found for mapping MgOH (2.3 μm) minerals due to dry vegetation having similar absorption characteristics at these wavelengths. Kaolinite and smectite (montmorillonite) were found to be the most commonly mapped aluminium hydroxide minerals in the shortwave region, where as hematite and goethite were the predominant minerals in the visible-near infrared region.