From Mantle to Cratonic Reactivation: Petrological Insights from Kimberlites and Lamproites of the São Francisco Craton, Brazil

This study redefines the Nordestina Kimberlite Province (PKN), in the northeastern sector of the São Francisco Craton (SFC), as a composite kimberlitic–lamproitic system that hosts two genetically distinct magma types: (1) the primitive Braúna kimberlite and (2) hybridized phlogopite-rich lamproites belonging to the SFC lamproite variety. Braúna kimberlites represent an olivine-rich kimberlite sourced from a metasomatized lithospheric mantle, as reflected by its high MgO (15%–30.6%), Ni (up to 1172 ppm), and Cr (up to 2500 ppm). These geochemical signatures are consistent with a primitive melt capable of preserving diamond stability conditions. In contrast, the SFC lamproite variety exhibits strong crustal overprinting, marked by hydrothermal barite–carbonate–silica veining, cristobalite, elevated SiO2 (up to 80 wt.%), and high LOI (up to 27.5%). These features indicate significant post-magmatic alteration, felsic crust assimilation, and melt hybridization. Textural and mineralogical features found in both magma types, including olivine-phlogopite aggregates, irregular zoning, and disequilibrium assemblages, suggest magma mingling between compositionally distinct melts and/or crystallization under polybaric conditions. These findings clarify long-standing classification controversies by demonstrating that PKN magmatism is not represented by a single rock type but instead spans a continuum spectrum from primitive kimberlite to strongly hybridized lamproite. Regionally, the data reveal that PKN magmatism reflects Paleoproterozoic mantle metasomatism reactivated during Neoproterozoic tectonism. This dual-stage evolution explains the contrasting degrees of primitiveness and hybridization melt signatures observed across the province.