An evaluation of NS-001 and TIMS data for lithological mapping and mineral exploration in weathered vegetated terrain

Abstract

This thesis evaluates the combined use of multispectral remotely sensed data from the 0.45-2.35µm and 8µm-12µm wavelength regions for lithological mapping and mineral exploration in weathered, vegetated terrain. The area studied is located in N. E. Queensland, Australia, and consists of a mixture of igneous, metamorphic and sedimentary rocks. The extrusive and intrusive igneous rocks of acid to intermediate composition are currently the focus of active exploration for gold mineralisation. The results from this study indicate data from the 0.45-2.35µm wavelength region are of more use for mineral exploration than data from the 8-12µm wavelength region in this terrain. Evaluation of data from the 0.45-2.35µm wavelength region resulted in the discovery of an area of epithermal alteration with potential for gold mineralisation at Blackfellow Mountain. Data from both wavelength regions proved useful for litholgical mapping but certain lithological units could only be discriminated with the data from the 8-12µm wavelength region. In order to obtain these results the data were reduced to physically meaningful parameters (reflectance, temperature and emittance). This necessitated the removal of radiometric and geometric distortions. The techniques used to remove these distortions are outlined, including two new methods for the removal of atmospheric effects from data from the 8-12µm wavelength region. After correction, the data from the 0.45-2.35µm wavelength region were analysed by a variety of techniques to extract the relevant reflectance information. These included compositing, channel ratios, log residuals, directed principal components and least squares fit residuals (LRES). The log residual and LRES techniques proved most effective for lithological mapping and mineral exploration respectively. The corrected data from the 8-12µm wavelength region were also analysed by several techniques for extracting emittance and temperature information. These techniques were the decorrelation stretch, model emittance calculation and thermal log residuals. The latter technique, developed during this study, proved most effective for lithological mapping.