Geological mapping in the proterozoic Mt. Isa Inlier, Queensland, Australia, using radiometric and multispectral remotely sensed data

Landsat Thematic Mapper, NSOOl Aircraft Thematic Mapper, Geoscan Mk. II. Multispectral Scanner and Airborne Gamma Radiometric data have been used to address a variety of geological problems in the Mary Kathleen area, 60 km east of Mt. Isa, NW Queensland. This area forms part of the Cloncurry Complex, a structurally complicated mass of diverse igneous and metamorphic rocks in the Precambrian Mt. Isa Inlier for which many stratigraphic problems remain to be solved. The Landsat Thematic Mapper data have been the most extensively used in this study. They are the least problematic data type and provide new geological information at scales up to 1:50 000. The NSOOl Aircraft Thematic Mapper data have similar spectral but superior spatial resolution in comparison with the satellite data. They suffer from increased geometric and noise-related problems, but the increase in spatial resolution has allowed the solution of problems, at scales up to 1:10 000, which could not be comprehensively addressed with the satellite data. The higher spectral resolution Geoscan Mk. II Multispectral Scanner aircraft data used in the latter part of the study can be used to remotely identify surface mineralogy. The logarithmic residual technique has proved the most successful approach to enhancing the radiance data sets. When applied to the lower spectral resolution data the technique achieves good discrimination of most lithologies, produces an albedo image useful for structural mapping and yields more information than can be extracted using conventional techniques. When applied to the higher spectral resolution data the technique allows remote mineral identification. Many of the geological problems in the area have been wholly or partially solved using suitably processed radiance data. The Airborne Gamma Radiometric data have the lowest spatial resolution. Only discrimination has been possible with this data set. These data contain no terrain information and are therefore difficult to use in the field. Integration of the gamma radiometric data with satellite data has been successful in overcoming this problem. The gamma radiometric data have allowed the separation of some lithologies which cannot be separated using the radiance data sets but have contrasting radiometric counts.