Field tests of this method in the Pilbara were conducted during 1995-96. The geochemical data aid correlations between the image data and the compositions of the rocks in the areas sampled. In the Pilbara study, the following choices of RGB components promoted maximum discrimination between weathering materials, and reflected the morphological features of the terrain. Drainage arteries throughout the region are characterised by abundant eucalypts and low clay contents. Consequently, the drainage system is marked by dark to black outlines.
Materials yielding the highest reflectance in all bands include quartz and silcrete.
In particular, coarse quartz in granitoid rocks, and abraded clastic quartz in mature arenite and in alluvial sands in creek beds, reflect strongly in all bands, as confirmed by field correlations. The sum of reflectance values of bands 1 and 7 can be used in this regard. By contrast, use of only the lower or higher band will favour clay or iron oxide respectively. Further field and laboratory spectrometric measurements should allow fine tuning of satellite and airborne multispectral correlations as one of the essential prerequisites for the next generation of geoscientific maps. The phyllosilicate alteration is associated with pods of sulphide, facilitating field and remote scanner-based economically oriented alteration mapping.