Distinct Transcrustal Evolutions of Komatiitic Primitive Magma: Implications for the Compositional Dichotomy of Continental Flood Basalts

Abstract

The origin of the compositional dichotomy between high‐Ti and low‐Ti basalts in continental flood basalt provinces remains debated. Most existing studies attribute this dichotomy directly to variations in primitive magma composition to circumvent the complexities of significant evolutionary processes, such as multiphase fractional crystallization. Here, we evaluate komatiite as a viable parental magma for the late Permian Emeishan Large Igneous Province to constrain its magmatic evolution. Olivine phenocrysts and spinel inclusions in the investigated picrites exhibit close affinities, consistent with derivation from a common komatiitic parental magma. Thermobarometric constraints define an olivine‐spinel‐clinopyroxene crystallization sequence and reveal two pressure regimes: 0–4.4 and 5.7–8.5 kbar. Thermodynamic modeling successfully reproduces the observed mineral assemblages and liquid lines of descent, accounting for two distinct adiabatic and multi‐stage evolutionary paths. We propose that extensive crustal differentiation along the liquid line of descent produced high‐Ti basalts, whereas limited evolution, melt‐cumulate re‐equilibrium, or incomplete crystal‐melt segregation generated low‐Ti basalts. These results demonstrate that contrasting crustal evolutionary pathways acting on a common komatiitic magma govern compositional diversities observed in global continental flood basalt provinces.