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 hydro-thermal stages. The late- to postmagmatic fluid is enriched in F and CO2, and appeared as a result of the final oversaturation of th