A Review of Mantle Heterogeneity and Magmatic Processes in the Vitória–Trindade Ridge System, South Atlantic Ocean, Brazil

Trindade–Martim Vaz Archipelago represents the easternmost point of intraplate volcanism in the South Atlantic and is part of the Vitória–Trindade Ridge (VTR), providing important evidence of magmatism related to a shallow mantle plume. Geochemical data indicate compositional continuity between alkaline basalts and phonolitic rocks, reflecting the complex magmatic evolution of the system. Primary melts, originating from mantle decompression beneath the oceanic crust, do not immediately ascend to the surface, remaining for long periods at lithospheric levels where they are modified by fractional crystallization, assimilation, and magma mixing. These interactions control geochemical differentiation and generate the compositional variations typical of oceanic environments. Magma chambers, therefore, play a fundamental role in thermal and compositional evolution, influencing geochemical signatures and eruptive dynamics. Petrographically and mineralogically, clinopyroxenes are distinguished by zoned green cores and euhedral rims, with strong pleochroism, suggesting crystallization under variable pressure and temperature conditions during magmatic ascent. Clinopyroxenes with green cores are associated with high-pressure environments, while partially resorbed ones reflect multiple stages of differentiation and assimilation. This evidence indicates recurrent magmatic replenishment and disequilibrium formation at variable depths, consistent with a thermally anomalous but heterogeneous mantle source. The isotopic signature demonstrates decoupling between Ar/Ar systems, implying contributions from distinct mantle domains and possible crustal contamination. Taken together, these data characterize Trindade–Martin Vaz as an essential terminal system of the Vitória–Trindade Ridge, fundamental to understanding small-scale plume dynamics and intraplate magmatic diversity in the South Atlantic.