Origin of giant Fe-Ti-V oxide deposits in layered gabbroic intrusions, Pan-Xi district, Sichuan Province, SW China

Abstract

The Pan-Xi region, SW China, is part of the Emeishan large igneous province, which comprises voluminous flood basalts and spatially associated mafic-ultramafic intrusions. The ~260 Ma gabbroic intrusions at Pan-Xi host giant Fe-Ti-V oxide deposits. Unlike the oxide deposits in classic layered intrusions, such as the Bushveld Complex, those in the Pan-Xi region occur as layers and/or lenses within the gabbros and are generally concentrated in the lower parts of the intrusions. Available geochemical evidence suggests that the intrusions were formed from highly evolved Fe-Ti-V-rich ferrogabbroic or ferropicritic magmas. Ore textures and associated mineral assemblages indicate that the orebodies were formed by late-stage crystallization of V-rich titanomagnetite from oxide liquids. The abundant accessory hydrous phases suggest that addition of fluids from upper crustal rocks might have induced the separation of the immiscible oxide melts and subsequently gave rise to the oxide orebodies.