赣南白鹅花岗岩中锆石特征和年龄及其对多期次成矿的指示意义

Characteristics and Age of Zircons of Bai′e Granite in South Jiangxi and Its Enlightment of Multistage Mineralization

白鹅花岗岩体位于赣南于山成矿带中东部,其相关成岩年代学数据目前尚未见报道。应用激光剥蚀-多接收器电感耦合等离子体质谱法(LA-MC-ICPMS)测定该岩体具有两组成岩年龄,分别为(174.1±5.4)Ma和(152.4±1.4)Ma,表明白鹅花岗岩体至少经历两次构造岩浆活动,第一次发生在燕山早期第二阶段(170～180 Ma);第二次发生在燕山早期第三阶段(150～165 Ma),两次岩浆活动相差约22 Ma。结合已有的调查研究成果认为,白鹅花岗岩体的形成与印支造山运动后壳幔相互作用引起的岩石圈伸展、陆壳部分熔融有关。两次岩浆活动均发生在华南地区两次大规模成矿作用时间内,预示了该岩体具有较好的找矿前景;而第二次岩浆活动发生在南岭(尤其是赣南)钨锡等主要矿产的成矿高峰期,相对第一次具有更好的成矿潜力。根据于山成矿带其他岩体的成岩信息对比,白鹅花岗岩体可能也曾发生印支期岩浆活动。

There is no available petrogenic chronology data at present for the Bai＇e granitic pluton, which is located in the Yushan metallogenic belt of South Jiangxi, This paper firstly attained its two groups of petrogenic ages, （ 174.1±5.4） Ma and （ 152.4± 1.4 ） Ma by means of the Laser Ablation-Multicollector Inductively Coupled Plasma-Mass Spectrometry （LA-MC-ICPMS） method, which shows that it had experienced two periods of tectonic- magmatic activity at intervals of 22 Ma. The former occurred in the second stage （ 170 - 180 Ma） of the early Yanshanian era, while the latter occurred in the third stage （150 -165 Ma）. Combining obtained achievements, the author considers the forming of the Bai＇e granitic pluton to be related to lithosphere extension and partial melting of the continental crust resulting from crust-mantle interaction after Indosinian orogeny. Both of the magmatic activities occurred within the stages of large-scale metallogeny in southern China, which indicates their favorable ore prospecting perspective. The second time of tectonic-magmatic activity points to more potential in metallogeny due to the contribution of peak metallogeny in the Nanling area, especially that of W and Sn in southern Jiangxi. Additionally, the Bai＇e granitic pluton may have experienced Indosinian magmatic activity according to information from other plutons in the Yushan metallogenic belt.