Tectonic reactivation along the Florianopolis Fracture Zone, Brazil

Abstract

The Florianopolis Fracture Zone (FFZ), Brazil, delimits the Pelotas and Santos basins and marks a major change in the geology of the continental margins from south to north, along both sides of the South Atlantic Ocean. The continental prolongation of it is represented by Lower and Upper Cretaceous alkaline rocks, Paleocene hydrothermal manifestations and river catchments. Geological review along with total magnetic field reduced to the pole map (EMAG 2) were used to investigate and analyze the Florianopolis Fracture Zone. Our results indicate that the intra-continental NW-SE transfer zones control Upper Cretaceous sedimentation and Lower Cretaceous carbonatitic intrusions.  The transition from continental crust to oceanic crust is achieved by the formation of normal faults and horse tail structures near the coastline verging to the FFZ at the already attenuated crust. Alkaline rocks, including carbonatitic ones, arose in the continental crust at the southwest projection of Luis Alves Craton and at the intersection between the transfer zones and the Brusque Metamorphic Complex. The integrated analyses indicated that the location of the FFZ was governed by the geological events in the continental crust. This oceanic/continental trend was later reactivated well past the South Atlantic opening.