Accessory minerals in the Xihuashan Y-enriched granitic complex, southern China: A record of magmatic and hydrothermal stages of evolution

The Xihuashan granitic complex (southern China) is mainly composed of coarse-grained porphyritic biotite granite (G-a), medium-grained porphyritic biotite granite (G-b), and medium- to fine-grained porphyritic biotite granite (G-c). The G-a granite is characterized by monazite-(Ce) and xenotime-(Y), in addition to commonly observed zircon and uranoan thorite. In the G-b and G-c intrusive units, monazite-(Ce) becomes very scarce, whereas Y-bearing minerals, including Y-bearing spessartine, xenotime-(Y), gadolinite-(Y), fergusonite-(Y), and yttrian fluorite (up to 15 Wt% Y2O3), are concentrated to various extents. Spessartine exhibits chemical zoning, which is displayed, in the core, by elevated contents of Y and heavy REE (HREE) (up to 2.32 Wt% Y2O3 and 1.51% HREE2O3) and micrometric inclusions of Y-bearing minerals. Similarly, zircon from the G-b and G-c granites contains polymineralic micro-inclusions in the core. Overall, the accessory minerals point to a magmatic environment of crystallization for the G-a granite. In contrast, the crystallization of the G-b and G-c granites involved magmatic and hydrothermal stages. The late- to postmagmatic fluid is enriched in F and CO2, and appeared as a result of the final oversaturation of the granitic melt in a fluid phase.