赣南盘古山钨矿床锆石U-Pb和辉钼矿Re-Os年龄及其意义

摘要

The Pangushan tungsten deposit is a well-known old and large ore deposit which has attracted many researchers and exploration geologists both in China and abroad. In order to determine the ages of magmatism and mineralization in the deposit and thus to gain insights into the relationship between magmatic process and tungsten mineralization, the association of endocontact mineralization with exocontact mineralization as well as their geodynamic setting, the authors conducted LA-ICP-MS zircon U-Pb and ICP-MS molybdenite Re-Os isotopic measurement of Pangushan concealed granite and its endocontact-mineralized quartz veins discovered by 2000 m Nanling Scientific Drilling (SP-NLSD-2). The results indicate that the weighted average ages of zircon 206Pb/238U ages for Pangushan granite and of molybdenite Re-Os isotopic model ages for the quartz veins are (161.7±1.6) Ma and (155.3±2.8) Ma, respectively, both subordinate to Mid-late Jurassic. The determinations, together with previous data, suggest that the mineralized quartz veins were produced by terminal magma evolution, which is supported by the fact that the ages of mineralization and magmatism were basically in accordance, the mineralization all occurred spatially at the inner- and outer-contacts of the granite, and the gradient relationship of granite→feldspar quartz vein→quartz vein was detected in the deposit. Endocontact and exocontact ore-bearing quartz veins were both produced by the same mineralization. Geodynamically, the Pangushan tungsten deposit is one of many important tungsten-polymetallic deposits formed from 165 Ma to 150 Ma associated with large-scale lithospheric extension in South China.%盘古山钨矿是一个历史悠久、闻名国内外的大型矿床,为了厘定其岩浆活动及成矿作用时代,进而认识成岩与成矿关系、岩体内带与外带矿化关系及成岩成矿动力学背景,本研究采用LA-ICP-MS锆石U-Pb和ICP-MS辉钼矿Re-Os分析法分别对南岭2000 m科学钻探(SP-NLSD-2)所揭露的隐伏花岗岩体及其内带矿化石英脉进行了年龄测定。结果表明,隐伏花岗岩体形成于(161.7±1.6) Ma,内带矿化石英脉年龄为(155.3±2.8) Ma,均形成于中-晚侏罗世。盘古山钨矿床花岗岩浆活动与成矿作用的时代在误差范围内基本一致,矿化发育于岩体内外接触带,在空间上关系密切,并表现出花岗岩体→长石石英脉→石英脉的渐变演化关系,结合前人研究成果表明,矿化石英脉是花岗岩浆分异演化晚期的产物。岩体内带石英脉与外带石英脉的形成年龄吻合较好,形成于同一成矿作用。盘古山钨矿床及其隐伏花岗岩体均形成于165~150 Ma华南岩石圈伸展-岩体侵位-大规模成矿的动力学环境。