AIRBORNE RADAR DATA - UTILITY FOR GEOLOGICAL MAPPING IN TROPICAL ENVIRONMENTS, SERRA-PELADA, PARA, BRAZIL

Airborne Synthetic Aperture Radar (SAR) was acquired over the Carajas Mineral Province, within the rainforests af The Amazon, which hosts th e world's largest Fe-ore deposit (Santos, 1986). Significant chemical weathering exists in this humid environment. Prevalent Aii mineralizat ion is thought to be generally associated with deformation zones in Ar chean schists. Radar data have proven to be very useful as an aid to g eological mapping in the tropical rainforests of the Amazon Basin in B razil. in these densely vegetated areas, a sense of regional structura l trends is obtained as a consequence of the sensor/terrain geometry. The top forest canopy is the main terrain reflector of X-band radar en ergy, and consequently is the main terrain surface feature expressed i n processed radar imagery. Radar is important for extending the contin uity ai mapped structural lineaments. Differential weathering is relat ed to variations in radar image texture which is used to infer gross l ithologic variations and relative age relationships of major rock unit s. Specifically, quartzites and banded iran formation are highlighted in the radar imagery due to their unique tonal and textural appearance , in contrast to schists, gneisses and metavolcanic rocks. As tropical areas aip typically enveloped in cloud or mist, radar data are invalu able in providing information for logistical planning of field mapping activities.