论文部分内容阅读
密坑山锡矿田是南岭地区与火山-次火山作用有关锡成矿的典型代表。本文运用锆石 U-Pb、全岩 Rb-Sr 和辉钼矿Re一()s同位素之年方法,对该区成岩和成矿年龄进行了系统测定,并据此讨论了它们的成矿意义:研究结果表明,密坑山岩体锆石 U-Pb 年龄为(136.0±1.7)Ma,全岩 Rb-Sr 等时线年龄(124.5±0.7)Ma,二个计时体系之间存在明显的时差,计算的冷却速率为8.7℃/Ma,指示岩体在成岩早期冷却相当缓慢。矿田范围内2件不同矿化类型辉钼矿的 Re-Os 模式年龄变化于(114.0±1.6)Ma 和(120.2±5 3)Ma 之间,它们均明显晚于成岩年龄,指示区内具有长时间的热液循环系统,成矿时间延续也较长,并可能经历了多期次的成矿作用区域动力地质背景和岩体地球化学特征的综合分析表明,密坑山矿田深部存在地幔物质的上涌,从而维系了高的地热场环境。这一高热场环境一方面使岩体缓慢冷却,同时也维系了长时间的热液循环系统,进而引发了大规模的锡成矿作用。
Mishan Shan tin ore field is a typical representative of tin mineralization in the Nanling area and volcano-subvolcanic activity. In this paper, we use the zircon U-Pb, Rb-Sr and molybdenite Re () s isotopic dating methods to systematically determine the diagenesis and metallogenic age of the area, and discuss the significance of their mineralization The results show that the zircon U-Pb age of the Mishan Mountain is (136.0 ± 1.7) Ma, and the Rb-Sr isochron age of the whole rock is (124.5 ± 0.7) Ma. There is a significant time difference between the two timing systems , The calculated cooling rate is 8.7 ℃ / Ma, indicating that the rock mass cooled slowly in the early stage of diagenesis. The Re-Os mode ages of two different mineralized molybdenites in the ore field ranged from (114.0 ± 1.6) Ma to (120.2 ± 5 3) Ma, which were significantly later than the diagenetic age. Long time hydrothermal cycle system, the continuation of the metallogenic time is also longer, and may have undergone a multi-period mineralization region dynamic geology background and rock mass geochemical characteristics of a comprehensive analysis shows that there is a deep mantle pit mines Substance upwelling, thus maintaining a high geothermal field environment. On the one hand, this high thermal field environment causes the rock mass to cool slowly, and at the same time maintains the hydrothermal circulation system for a long time, which in turn leads to the massive tin mineralization.