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.
1 December 2022 in Journal of the Geological Survey of Brazil