Arquitetura crustal, tectônica e magmatismo da Bacia de Campos e sua influência no intervalo Pré-sal

Abstract

The Campos Basin is an important Brazilian oil province, holding voluminous reservoirs in the Pre-salt interval. Emerging as a key area for studying the evolution of deep rifted margins, this region requires a detailed investigation of its structural configuration to better understand the processes of lithospheric extension and sedimentary deposition during rifting. In this work, the crustal architecture and structural domains of the Campos rifted margin were investigated using 2-D and 3-D seismic reflection interpretation, analysis and modeling of potential field data, and exploratory wells. The results revealed an along-strike variability in terms of margin architecture and magmatism, which segments the basin into three main sectors: Southern, Central and Northern Campos. This lateral variability is interpreted as a product of alternations between lower and upper-plate configurations and different magmatic inputs, where the Southern Campos margin represents a lower-plate setting, while the Central and Northern Campos margins represent an upper-plate configuration. In this scenario, it is proposed that the Vitória-Colatina Transfer Zone played a fundamental role in the margin segmentation, accommodating important lateral changes in the structural style. A detailed investigation indicated that the distal domain of the Southern Campos is characterized by the formation of the Gávea Supradetachment Basin, associated with the development of a metamorphic core-complex and lower crust exhumation. The Central Campos margin is characterized by a massive residual block (keystone block) and by a crust altered by magmatism. These results suggest that this segment experienced a high magma input throughout the rift evolution, characterized by the formation of Seaward-Dipping Reflectors and a magmatic crust in a transitional domain that extends to the first Penrose-type oceanic crust. A detailed analysis of this segment revealed that, from the necking to the distal domain, the extension was accommodated by three main detachment faults that resulted in the exhumation of different crustal levels, evidencing a complex interaction between tectonic and magmatic processes. The Northern Campos margin represents an upper-plate setting but characterized by a progressively delaminated residual block. Finally, the potential field model of the Northern Campos margin also indicated the presence of a magmatic crust in the transitional domain, suggesting that both the Central and Northern Campos margins experienced a more magmatic break-up when compared to the Southern segment. Thus, the results of this work show that rifted margins cannot solely be classified as either magma-poor or magma-rich, with the Campos margin revealed as an excellent laboratory for the investigation of hybrid rifted margins.