Petrogenesis of Late Permian Mafic Rocks in the Western Guangxi Area, SW China: Implications for the Emeishan Mantle Plume Magmatism

Mafic rocks in western Guangxi exhibit pronounced spatiotemporal correlation with the Emeishan Large Igneous Province (ELIP), providing critical constraints on its magmatic distribution, petrogenetic mechanisms, and evolutionary history. This study presents zircon U-Pb geochronology, whole-rock geochemistry, and Sr-Nd isotopic data for Tianlin mafic rocks from the outer zone of the ELIP. These rocks yield a concordant zircon U-Pb age of 258.3 Ma, contemporaneous with the main eruptive phase of the ELIP. Geochemically, they comprise a high-Ti series (TiO₂ = 2.79-4.74 wt %; Ti/Y = 507-1229), exhibiting ocean-island basalt (OIB)-like chondrite-normalized REE patterns but subtle negative Nb-Ta-Zr-Hf anomalies on primitive mantle-normalized diagrams. Moderately enriched Sr-Nd isotopic signatures [(⁸⁷Sr/⁸⁶Sr)_i = 0.705522-0.705891; εNd-(t) = +0.43 to +0.81] indicate derivation from an enriched mantle source. Integrating regional geology with these data, we propose that interaction between the Late Permian Emeishan mantle plume and Neoproterozoic oceanic slab generated the ELIP's compositional diversity.