Reverse magmatic evolution series of the Xiangshan volcanic intrusive complex

Abstract：The Xiangshan area as the largest volcanic-hosted uranium ore occurrence in China has received great attention. From eruption→viscous lava extrusion→intrusion, the SiO2 content, Rb/Sr and Rb/Ba of the Xiangshan volcanic-intrusive complex decreased, while the TFe (Fe2O3+FeO), CaO, MgO, P2O5 and TiO2 contents and the solidification index SI and δEu increased progressively, showing that the magmatic evolution has an antithetic relationship with the magmatic differentiation trend reflected by increasing acidity in the normal magma chamber, which is called the reverse magmatic evolution series. The incompatible element radios such as Th/U, Rb/Ba, Th/Nb, Th/Ta, Nb/Ta and La/Nb vary widely, showing no distinct synthetic or antithetic relationship with the major components such as SiO2. The REE distribution patterns also vary. These suggest that the volcanic eruption facies, viscous lava extrusion facies and intrusive facies were derived from different sources.