A geochronological study of granite and related mineralization of the Zhangjiadi molybdenite-tungsten deposit in Xingguo County, southern Jiangxi Province, China, and its geological significance

The Xingguo-Ningdu ore cluster in southern Jiangxi Province, located in the convergent zone of the eastern Nanling EW-trending metallogenic belt and the western Wuyishan NE-trending metallogenic belt, possess several different type of W-Sn polymetallic deposits. However, little research has been done for these deposits. Based on detailed field investigations, high-precision isotope dating on the Zhangjiadi Mo-W deposit, the time-space distribution of W-Sn ore deposits in Cathaysia Block and their geodynamic settings are studied in this paper. SHRIMP zircon U-Pb age for porphyritic fine to medium-grained biotite granite from the Zhangjiadi ore deposit is 154.1 +/- 1.8Ma. Molybdenites separated from the quartz vein type orebody in the Wangnipai ore block and the greisen orebody in the Liujiazhuang ore block yield Re-Os isochron ages of 158.4 +/- 3.1Ma (weighted mean age 157.7 +/- 1.4Ma) and 161.9 +/- 3.2Ma (weighted mean age 157.9 +/- 1.6Ma), respectively, which are corresponding to Late Jurassic period. The studied molybdenites show quite low Re contents (9.58 x 10(-6) similar to 22.65 x 10(-6)), suggesting a continental crustal source of the ore metals. Integrated with the latest research results, it is concluded that the W-Sn deposits formed during 240 similar to 210Ma, 170 similar to 150Ma and 130 similar to 90Ma, and are centered by the largest scale in southern Jiangxi Province and southern Hunan Province, and become younger in the east, west, south and north directions. We suggest that the Yanshanian large-scale magmatic and ore-forming processes may have occurred in a Jurassic intraplate extensional geodynamic setting during the Mesozoic lithosphere extension in South China.