Remote sensing in uranium exploration

New types of multispectral data and computer enhancement of images provide a basis for quantitative analysis of ground reflectance, colour discrimination and removal of illumination-geometry effects, not possible with standard aerial photographs. These methods can be designed to take advantage of spectral characteristics of minerals such as hematite and limonite in attempting to discriminate areas of alteration around mineral deposits. The spectral bands of Landsat are not optimum for this discrimination, but several studies show that enhancement of Landsat images permits effective mapping of altered ground in some areas. Red and yellow ground may be confused, a problem where only one of these colours marks alteration related to mineralization. Altered ground in uranium areas has been successfully defined at Cameron, Arizona and Crooks Gap and the Powder River Basin in Wyoming. The Wyoming studies, described in some detail, resulted in unambiguous discrimination of red alteration at Crooks Gap but only partial distinction of red altered ground from yellow-weathering areas in the Powder River Basin. In South Texas, heavy vegetation severely limits the detection of reflectance differences in geological materials or of structural features. Thermal-infrared images of the Texas area aid in detection and mapping of channel-fill deposits, potential loci of uranium mineralization in the Miocene Catahoula Tuff. (author)