Mapping Mineralogical and structural relationships with satellite-borne ASTER and airborne geophysics at Broken Hill

Abstract

The recent availability of 14 band multi-spectral and 15 metre DEM data from the satellite borne ASTER (Advanced Spaceborne Thermal Emission Reflection Radiometer) instrument has introduced new possibilities for geological mapping and integration with traditional geophysical data sets. Calibrated radiance at the sensor data and atmospheric corrected ASTER products, such as surface reflectance and emissivity imagery, have been made available by NASA/USGS and the Japanese agency, ERSDAC. ASTER radiance data measures five bands at 30 metre resolution, within the short-wave infrared 2.1 to 2.5 mm wavelength region, and also five bands at 90 metre resolution within the 8 to 12 mm thermal infrared region. This compares with only one band as measured by Landsat TM for each of these regions. An investigation into the capabilities of ASTER and strategies for its integration with geophysical data (using ER Mapper) was undertaken at Broken Hill, given its high spatial geological control and extensive airborne geophysical data sets. Mineral (group) maps derived from multi-scene ASTER data, collected over the Broken Hill Block, proved useful for discriminating stratigraphic units, regolith and areas of alteration. In particular ASTER imagery highlighted several sericite-rich as well as quartz-rich colluvial regolith. Variations in ASTER?s derived AlOH mineral spectral signatures correlated with higher potassium radiometric responses and indicated a change in the muscovite chemistry, possibly due to retrograde metamorphic alteration. However structural features associated with retrograde shear zones were identified most clearly using aeromagnetics. Overall ASTER data products provided complementary mineralogical information to the structural interpretation afforded by geophysical data sets.