The Vitória Dike Swarm: A Key Piece in the Puzzle of Low-Ti Tholeiitic Magmatism Related to the South Atlantic Rift System

During the Lower Cretaceous, a significant tectonomagmatic activity around the South Atlantic Rift System led to the formation of numerous sedimentary basins, continental volcanism (basaltic and silicic), dike swarms, sill complexes, alkaline intrusions, and volcanic margins. In the northern Mantiqueira Province (Espírito Santo, Brazil), the Vitória-Ecoporanga belt is characterized by intense NW-SE-oriented faulting and fracturing zone, that hosts the Vitória Dikes, the northernmost low-Ti tholeiitic plumbing system of the Paraná Magmatic Province. These dikes exhibit microgabbroic textures and mineralogy composed mostly of plagioclase, clinopyroxenes, and Fe-Ti oxides. Geochemically, they have MgO = 3.83-7.2 wt.%, aligning with subalkaline tholeiitic basalts to basaltic andesites (total alkalis = 2.4-4.8 wt.%). These tholeiites are enriched in large ion lithophile elements, showing pronounced negative anomalies of Nb(-Ta) in comparison to Rb, Ba, U, Th, K, La, Ce, and Pb. They have ⁸⁷Sr/⁸⁶Sr_(i) ranging from 0.70994 to 0.70575, and εNd_(i) varying from -0.95 to -11.4, combined with heterogeneous values of Pb isotopes: ²⁰⁶Pb/²⁰⁴Pb_(m) (18.2-16.7), ²⁰⁷Pb/²⁰⁴Pb_(m) (15.6-15.4), and ²⁰⁸Pb/²⁰⁴Pb_(m) (38.9-37.6), thus suggesting some degree of lithospheric/crustal contribution. New ⁴⁰Ar/³⁹Ar and K-Ar geochronology confirms an Early Cretaceous filiation to the Vitória Dikes. After comparing the multidata types of the Vitória tholeiites with the existing dataset of the Riacho do Cordeiro Dikes of the Equatorial Atlantic Province, it is possible to suggest that both were interconnected during the Early Cretaceous. This reinforces therefore that the Vitória and Riacho do Cordeiro Dikes would constitute one of the largest low-Ti tholeiitic plumbing systems in the South Atlantic area associated with the Cretaceous breakup of the West Gondwana supercontinent. In this context, a parental E-MORB magma mixed with melts derived from the West Gondwanan lithosphere to form the low-Ti tholeiites. Although tracing a mantle plume as a direct geochemical contributor to low-Ti basalts is challenging and not straightforward, it cannot be completely dismissed. A smaller contribution from the plume may have been involved in the formation of potential parental liquids with signatures analogous to E-MORBs.