Enhancing the Radiometric Map of Australia

Abstract

The Radiometric Map of Australia shows the distribution of potassium (% K), uranium (ppm eU) and thorium (ppm eTh) over Australia. A suite of image enhancement and data integration techniques can be used to enhance the value of these data for both mineral exploration and environmental mapping. Gradient-enhanced ternary and pseudo-colour image enhancements are now routinely used for the presentation and interpretation of gridded radioelement data. Where digital elevation data are available, these colour representations can be draped over the elevation data to form 3D perspective views, or hill-shaded derivatives of the DEM can be embedded into the ternary imagery as an intensity component. These are useful because the radioelement response can then be interpreted within the context of the relative position of anomalous features in the landscape. However, subtle variations in the concentrations of K, U, and Th are best interpreted using the ratios of the radioelements. The U/Th and U2/Th ratios are important indicators of uranium mineralization. The Th/K ratio is widely used for the detection of several styles of mineralization associated with K alteration. For the interpretation of map data, classification and clustering methods can be used to assist pattern recognition and are useful for the rapid assessment of large multivariate datasets. Automatic edge detection procedures can be used to speed up the annotation of unit boundaries. Residual modelling techniques can be used to highlight potential anomalies in the data.