Mesozoic dike swarms in Borborema Province (NE Brazil): A structural analysis based on airborne geophysical data and field work

Abstract

Mapping and analysis of dike swarms support a detailed understanding of the orientation, geometry, spatial distribution, geochronology, emplacement mechanism, structural control, and environments at the time of the magmatic events. Therefore, dike swarms have become a key tool for studying mantle plume activity, large igneous provinces, and continental breakup. Before the Pangea breakup, the Neoproterozoic Borborema Province (NE Brazil) was intensively intruded by sets of dike swarms, whose precise mapping and classification are essential for understanding the tectonic plate movements and evolution of the South American and African continents. In this sense, we promoted a regional mapping of dike swarms and their relationships between orientation, emplacement mechanism and structural control to provide a better understanding of the role of Mesozoic and Cenozoic large magmatic events in their tectonic evolution. We apply anomaly enhancement techniques to high-resolution airborne magnetic data to obtain the geometry and estimate the depth of causative sources. A structural analysis was carried out integrating magnetic patterns, field data and a compilation of previous geological maps to describe the detailed distribution of dike swarms in Borborema Province. Our study demonstrated that dike swarms extend over 5.4 × 105 km2. The 1388 mapped mafic dikes are grouped into three distinct dike swarms (DS): 1135 – Rio Ceará-Mirim DS; 168 – Canindé DS; and 85 – Riacho do Cordeiro DS. The dike swarms show three preferential trends: NE-SW, E-W and NW-SE. The geometry and structural analysis of the dikes allowed us to establish the paleostress field active at the time of intrusion. For the Rio Ceará-Mirim DS, the paleostress trajectories represent an N–S extension, rotating to NW-SE in the western portion of the swarm. For the Canindé DS, the paleostress orientation shows a NW-SE extension rotating to NE-SW. For the Riacho do Cordeiro DS, the trajectories are similar to those traced for the Rio Ceará-Mirim DS, showing a predominant NW-SE trend.