Petrogenesis, Pre-Aptian Magmatism, Santos Basin.

The Santos Basin, located in the southeastern portion of the Brazilian continental margin, covers an area of approximately 350,000 km² down to a bathymetric depth of 3,000 meters, including the coasts of the states of Rio de Janeiro, São Paulo, Paraná and Santa Catarina. The Santos Basin originated as a rift basin that evolved

into a passive margin basin after the opening of the South Atlantic Ocean. This evolution is recorded in three megasequences or phases: Rift, Post-Rift and Drift. The Camboriú, Piçarras and Itapema formations are part of the Rift Phase, the Barra Velha (upper and lower) and Ariri formations are part of the Post-Rift Phase, while

the Drift Phase ends an extensive sequence with intercalations of rhythmically stratified calcilutites, marls and siliciclastic rocks. Magmatic events are recorded in all three megasequences. The magmatism of the Rift Phase is predominantly basaltic and tholeiitic, and its rocks are part of the Camboriú Formation. The magmatic events of the Post-Rift Phase are less known but seem to be related to the Intra-Alagoas unconformity. These magmatic events are of interest because they are directly associated with the Pre-Salt sequence, which hosts important

petroleum systems located below the salt layer deposited at the boundary between the Neo-Aptian and the Early-Albian. The Post-Aptian magmatic events, recorded in the Santonian/Campanian and Eocene, are related to the Drift Phase of the basin. The discovery of large oil and gas reserves in the Pre-Salt sequence of the Santos Basin has increased interest in petrogenetic studies of the magmatic system. This dissertation, developed in the master's degree course of the Graduate Program in Modeling and Geological Evolution (PPGMEG) of the Federal Rural University of Rio de Janeiro (UFRRJ), focused on the study of Pre-Aptian magmatism in the PreSalt sequence of the Santos Basin, with emphasis on petrogenetic processes and

regional comparisons with the Campos Basin. The lateral samples of the magmatic sections of wells 3-BRSA-1290-SPS and 3-BRSA-883-RJS, located in blocks Libra and Lula in the Santos Basin, as well as the data available in their respective well folders, obtained from the National Petroleum Agency (ANP), constituted the study material of this dissertation. The rocks of the samples selected from the The well 3-BRSA-1290-SPS presents basaltic rocks ranging from light to dark gray, with a porphyritic texture and amygdalae filled with carbonate and pyrite, suggesting circulation of hydrothermal fluids. It also presents magmatic breccias in a fine matrix. The well 3-BRSA-883-RJS presents mafic to intermediate igneous rocks with low magmatic evolution, according to geochemical data. The volcanic and subvolcanic sequences of wells 3-BRSA-1290-SPS and 3-BRSA-883-RJS can be correlated with the magmatism of the Lower Cretaceous, related to the opening of the South

Atlantic and the basaltic flows associated with the magmatism of Alagoas, in the Campos Basin.