Another way of looking to an alkaline province

Abstract The Mesozoic Alkaline Magmatism on the South American Platform is related to the Gondwana breakup and the opening of the South Atlantic Ocean. This event, known as the Mesozoic Activation phase, was responsible for five magmatic pulses, among them the Late Cretaceous-Eocene Alkaline Magmatism, which implemented ten alkaline provinces, eight of which are in the south-central portion of Brazil. Some authors claim that the reactivation of old zones of weakness from the Precambrian basement, Brasiliano orogeny, may have been responsible for the structuring of few bodies in these provinces. This work used geophysical processing techniques to interpret magnetic and gravity data and 2.5 D forward modeling to contribute with the knowledge on the tectonic control over the Goias Alkaline Province. The geophysical data processing show a tectonic control over the Goias Alkaline Province, along the Brasiliano and Mesozoic structures, and there was no predominance of alkaline bodies along the Azimuth 125. We observe that the Brasiliano orogeny structures limited the crustal block that contains this Province and Gondwana breakup possibly create and reactivate these structures. We interpret the continuity of large structures, at different depths, related to the Tocantins Province, mainly in the Brasilia belt, and some of them can be observed up to approximately 20 km depth. The forward gravity modeling beneath the Goias Alkaline Province shows a thicker crust and we believe that the primitive mantle lithospheric below this province was not altered during the Brasiliano orogen stages, like the adjacent crustal blocks, allowing the generation of alkaline rocks. Along the section modeled the Arenopolis Magmatic Arc was separated in two different crustal blocks, Arenopolis Magmatic Arc-West, where it is located the Goias Alkaline Province, and Arenopolis Magmatic Arc-East, whose mantelic characteristics were altered due to collision with the Sao Francisco Paleocontinent. Thus, the geophysical data proved to be another way to study tectonic structures and alkaline provinces.