An integrated geochemical and isotope study to characterize the Equatorial Atlantic Magmatic Province (EQUAMP)

Abstract

This PhD proposal is part of a major project (FAPESP 2017/08423-9) whose main aim is to study the magmatic events related to the evolution of the Atlantic continental margin during the Cretaceous and therefore to the break-up of the West Gondwana, presently exposed in the northeastern Brazil. These events are represented by: (1) a continental-scale arcuate mafic (dolerites) dike swarm that crosscuts a major Precambrian basement block named the Borborema Province, and (2) a sill province intruding the Paleozoic sedimentary succession of the Parnaiba basin. The mafic dikes were until recently restrict to be a 350 km-long E-trending swarm consisting mainly of high-Ti tholeiitic dolerites closely related to the Atlantic Ocean opening. It has been known as Rio Ceara-Mirim Dike Swarm. However, recent high-resolution airborne magnetic surveys carried out on the Borborema Province have shown its continuation to SW extending about 1,000 km in length across the province, thus representing a giant dike swarm as defined in the classical work of Ernst and Buchan (1997) [AGU Geophysical Monograph, 100: 297-333]. The sill province is, in turn, located immediately west of the exposure area of the swarm, and is mostly represented by high-Ti coarse-grained basalts to basaltic andesites. They have been named as Sardinha sills. The very close spatial relationship between the dike swarm and the sills, together with the determination of Early Cretaceous ages allow us to test the hypothesis that they are part of a major continental magmatic province - the Equatorial Atlantic Magmatic Province (EQUAMP), and intend to formally characterize it as a new Gondwanan Large Igneous Province (LIP) in South America. The aim in this PhD proposal is to examine the CMDS and Sardinha sills based on geochemistry, with focus on elemental and Sr-Nd-Pb isotope data in order to understand the geochemical evolution of the EQUAMP magmas. With hope to contribute to the dynamics of the mantle (lithosphere-asthenosphere system), as well as crust, during the evolution of the Equatorial Atlantic margin in the Cretaceous as result of the Gondwana disruption. In a wider perspective, our data will be added to the data pool of international bibliography in order to extend the existing knowledge on modern plate tectonics and, consequently, how supercontinents have broken up. (AU)