赣东北朱溪铜钨矿区花岗闪长斑岩LA-ICP-MS锆石U-Pb定年及地质意义

赣东北朱溪超大型铜钨矿位于江南古岛弧带塔前—赋春成矿带中段,该矿床的发现可进一步验证"南钨北扩"观点并对"南钨北铜"格局提出挑战,但前人对与朱溪铜钨矿成矿作用有关的花岗岩缺少精确的年代学研究,导致对其地球动力学背景理解不够深入。本研究通过详细的野外调查、岩心编录和岩矿鉴定,并利用激光剥蚀电感耦合等离子体质谱(LA-ICP-MS)锆石U-Pb法对朱溪铜钨矿区侵入元古代双桥山岩群中的铜矿化花岗闪长斑岩进行测年,获得了锆石206Pb/238U加权平均年龄为847.2±9.4 Ma(MSWD=0.111),代表了其侵位结晶的年龄,属新元古代。分析认为:朱溪铜钨矿区铜矿化花岗闪长斑岩是新元古代早期华南古洋壳俯冲消减及扬子陆块与华夏陆块发生碰撞作用下的岩浆产物,这次岩浆活动与区域上塔前—赋春成矿带成矿作用关系密切,并为钦—杭成矿带提供了成矿物质基础。本次对其成岩年龄的限定,为研究朱溪超大型铜钨矿矿床提供了新证据。

LA-ICP-MS Zircon U-Pb Dating of Granodioritic Porphyry located Zhuxi Copper-Tungsten Mine in Northeast Jiangxi and Its Geological Significance

The Zhuxi ultra-large type copper-tungsten deposit in the Northeast Jiangxi province located in Taqian -Fuchun metallogenic belt which belongs to Jiangnan ancient island-arc, the discovery of the deposit has verified Southern Tungsten North Expansion perspective and challenge the viewpoint that Tungsten located in the south but the copper located in the north of Jiangxi provience, but the previous lack of accurate chronology study related to Zhuxi copper-tungsten mineralization of granite not enough, resulting in the geodynamic background of understanding. In this study, on the basis of detailed field investigation, core logging and petrology studies on the granodioritic porphyries which had intruded into the Middle Proterozoic Shuangqiaoshan group and with copper mineralization alteration, using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) zircon U-Pb dating, we obtained the granodioritic porphyries zircon ²⁰⁶Pb/²³⁸U weighted mean age of 847.2±9.4Ma (MSWD=0.111), which can represent the granodiorite porphyry magma emplacement and crystallization age, belonging to the neoproterozoic. The results reveal that the granodioritic porphyries of Zhuxi copper-tungsten mine is a product of the early Neoproterozoic Southern China ancient oceanic crust subduction and Yangtze and Cathaysian continental blocks collisional magmatism, the magmatic activity provides the basis for the metallogenic Qinzhou-Hangzhou metallogenic belt, and the magma event is close related to the Taqian-Fuchun ore belt mineralization, it also provides new evidence for the study of Zhuxi ultra-large type copper-tungsten deposit.