The role of major rift faults in the evolution of deformation bands in the Rio do Peixe Basin, Brazil
Deformation bands; boundary faults; shear zone; reactivation
Many studies have investigated on the evolution and properties of deformation bands, but there are few studies about their occurrence and relationships with basin-boundary faults. These faults was formed by brittle re-activation of structural inheritance in crystalline basements, belonging to the major syn-rift fault zones. However, there is a pos-rift influence on these faults as well. The main objective of this study was to analyze the influence of rift and pos-rift phases and the deformation bands behavior in each one. Reactivation in early Cretaceous times of continental-scale ductile shear zones led to the development of rift basins in NE Brazil. These shear zones form a network of NE- and E–W-trending structures hundreds of kilometers long and 3-10 km wide. They were active in the Brasiliano orogeny at 540-740 Ma. Brittle reactivation of these structures occurred in Neocomian times (~140-120 Ma) prior the breakup between the South American and African plates in the late Cretaceous. The Rio do Peixe basin formed at the intersection between the NE-SW striking Portalegre shear zone and the E-W striking Patos shear zone. The brittle fault systems developed by shear zone re-activation are the Portalegre Fault and the Malta Fault, respectively. In this research we used field structural investigations and satellite images. Our results indicate that boundary faults have influence with the occurrence of deformation bands.