Airborne geophysical data as an aid to geological mapping and target selection in the<br>Tapajós Gold Province, Brazil

Abstract

Airborne geophysical data acquired over the Tapajos Gold Province (TGP) in west Central Amazon Province display different patterns previously not identified in geological field mapping. Integrated analysis of airborne magnetic and gamma-ray spectrometric data plus available geological data was conducted to map and analyze these patterns, and to obtain insight in their regional significance. Enhancement of the airborne magnetic and gamma-ray spectrometric data have resulted in better definition of both geological structure and lithological boundaries than indicated on previous maps. Comparison of multiple geophysical signatures and known mining occurrences were particularly valuable for defining old targets and direct new ways for gold prospecting in the area. Areas with high to moderate favorableness encompass wellknown gold deposits, as well as new signatures that may have economic importance. Geophysical data were successfully used to highlight relationships between main crustal domains, as well as their internal structures and boundaries. The northeast domain bears the signature of older crustal material covered by rocks of the Uatuma Supergroup generated through partial crustal melting. The western limit of this domain is close to the supposed limit that divides the Central Amazon and Ventuari-Tapajos provinces. A large structure marked by high amplitude in the western part may record oceanic crust subduction and formation of the Cuiu-Cuiu arc.