Influence of pre-salt alignments in post-Aptian magmatism in the Cabo Frio High and its surroundings, Santos and Campos basins, SE Brazil: An example of non-plume-related magmatism

This study, based on interpretations of 2D and 3D seismic data, onshore satellite data, and offshore seismic mapping and well data, addresses the geological evolution of Late Cretaceous and Early Tertiary magmatism in the offshore Cabo Frio area, at the border between the Santos and Campos basins, SE Brazil. The analysis of the available data set suggests an alternative genesis for this magmatism, different from the classic mantle plume model. Seismic mapping of the main feeder dikes reveals a predominant SE–NW orientation, coincident with the alignment of the Cruzeiro do Sul deformation zone, in which the Cabo Frio High is included. This observation is coherent with the characteristics of the major onshore Precambrian strike-slip faults, which were reactivated during the Cenozoic. The largest offshore volumes of magmatic rocks occur intercalated in the sedimentary section and at the intersections of two fault alignments: a SE–NW, strike-slip fault trend and a SW–NE, normal fault trend, similar to the onshore alkaline bodies of the Poços de Caldas–Cabo Frio alignment. The possibly reactivated faults (mainly SE–NW transfer faults) could have cut through the whole lithosphere, reached the asthenosphere, and caused partial melting simply by pressure release.