Unraveling the Magmatic-to-Carbothermal Processes in the Ba–Sr–REE Mineralization of the Sevattur Carbonatites, India.

The article focuses on the petrogenesis and mineralogy of the Neoproterozoic Sevattur carbonatite complex in Tamil Nadu, India, emphasizing its diverse Ba–Sr–rare earth element (REE) mineralization formed during orthomagmatic to carbothermal stages. The complex comprises calcite carbonatite, silicate-poor and silicate-rich (banded and blue) dolomite carbonatites, with geochemical and isotopic evidence indicating a primary dolomitic magma derived by direct partial melting of a metasomatized mantle, rather than liquid immiscibility or genetic linkage with associated silicate rocks. The study details the sequential crystallization and alteration of minerals such as benstonite, carbocernaite, cordylite-(Ce), and various REE fluorocarbonates, controlled by evolving fluid compositions with varying activities of F⁻, CO₃²⁻, PO₄³⁻, SO₄²⁻, and H₂O. Silicate assemblages reflect magma evolution and assimilation of clinopyroxenite xenoliths, leading to distinct lithologies and mineral parageneses, while trace element data from calcite and ferroan dolomite support a predominantly magmatic origin with minor autometasomatic reworking.