The Guposhan ore district, located in the southwestern Nanling Range of South China, is characterized by its large-scale Yanshanian granitic batholith and significant Sn (W) mineralization, with a number of medium to large scale skarn-, and quartz vein-type Sn-W deposits. However, the geology and genesis of wollastonite mineralization in the Guposhan ore district and its relationship to the multi-stage granitic magmatism and associated Sn-W mineralization remain poorly understood. The absence of precise age constraints for wollastonite deposit impedes recognition of the key factors contributing to this non-metallic mineralization. In this study, we present LA-ICPMS U-Pb dating and trace element analysis of garnets from Qingshuitang wollastonite deposit in the southern Guposhan ore district. The garnets from high-grade (QST-4) and skarn-type low-grade (QST-5) wollastonite ores both belong to the andradite-grossular series, and yield lower intercept ages of 166.8±2.0 Ma and 165.9±2.1 Ma, with U contents of 2.89-3.26 ppm and 3.04-3.60 ppm, respectively. These ages are directly linked with the formation of skarn assemblages, and can be interpreted as the age of Qingshuitang wollastonite mineralization, which are consistent with the major peak magmatism and Sn-W mineralization (ca. 165~160 Ma) of the Guposhan district. Combined with geological features of the Qingshuitang deposit, we propose that the critical factors controlling the formation of wollastonite mineralization through thermal contact metamorphism are the large volumes of Lower Carboniferous limestone intercalated with chert nodules and bands serving as source rocks, and being almost parallel to the Guposhan intrusion-wallrock interface, as well as the substantial and abundant heat input caused by the large scale Guposhan granite. Besides, our study suggests that LA-ICP-MS U-Pb geochronology has the potential for significantly broader applications in dating non-metallic mineralization than its current utilization.
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