Domes and circular geological structures associated with Abrolhos Magmatic Province on the offshore Mucuri Basin, Brazil

Abstract

The offshore portion of the Mucuri Basin, located on the eastern Brazilian margin, was mapped employing seismic, lithological and petrophysical data. Dome structures were observable in seismic sections and circular geological structures identifiable on the seismic map. Four types of domes were identified in the seismic sections, three domic features in the 3D seismic sections (Domes I, II, and III) and another dome feature in the 2D seismic section outside the 3D seismic volume (Dome IV). The first, located in the central region of the 3D seismic volume, was interpreted as a salt dome generated by a halokinesis processes. The second was interpreted as encompassing hydrothermal vents (Dome II), formed by a conduit connecting them to the sills of the Abrolhos Magmatic Province (AMP). The third comprises subvolcanic features composed of radial dikes (Dome III). The fourth was identified outside the 3D seismic volume, on a regional 2D seismic section, interpreted as a forced fold generated by sill emplacement (Dome IV). The data indicate that all domes are in some way associated to the AMP, including the salt dome, with sills mapped below the salt layer, which may have contributed to the halokinesis process. Indirect dating through stratigraphy analyses indicates that AMP magmatism probably took place during the Neogene. This assessment contributes to a better understanding of Mucuri Basin geology, which still presents many gaps concerning stratigraphy, salt movement and AMP intrusive rock emplacement. The findings confirm that the AMP may have lasted much longer than what has been widely described in the literature, with potential associations between AMP emplacement and salt movement.