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本文主要对出露与西藏多龙矿集区铁格隆南矿区荣那矿段的安山岩开展了锆石U-Pb定年、岩石地球化学测试,旨在确定该套火山岩的成岩年龄及其形成的构造背景。安山岩的LA-ICP-MS锆石U-Pb加权平均年龄为(110.1±0.7)Ma(MSWD=2.3),代表了其成岩年龄。岩石Si O2为59.5%~61.48%;Al2O3为16.14%~17.11%;Na2O+K2O为6.02%~6.63%;Mg#值中等,微量元素富集Ba、Rb、Th、K等大离子亲石元素,相对亏损Ta、Nb、P、Ti等高场强元素,具有Rb正异常和明显的Zr、Hf负异常,据此认为该安山岩属高钾钙碱性系列岩石,具有活动大陆边缘火山岩的性质,是班公湖—怒江洋北向俯冲,拉萨地体与羌塘地体碰撞拼贴过程中所诱发的岩浆产物。结合其他资料分析认为,此安山岩的成岩时间应晚于铁格隆南高硫型浅成低温热液铜(金)矿床的成岩和成矿时间,是该矿床得以良好保存的重要条件。
In this paper, zircon U-Pb dating and geochemical tests were carried out on andesite exposed from the Rongna ore section of the Tiegulongnan mining area in the Dailong Ore Concentration Area of Tibet to determine the diagenetic age and formation of the set of volcanic rocks Tectonic background. The LA-ICP-MS zircon U-Pb weighted average age of andesite is (110.1 ± 0.7) Ma (MSWD = 2.3), representing the age of diagenesis. Rock Si O2 is 59.5% ~ 61.48%, Al2O3 is 16.14% ~ 17.11%, Na2O + K2O is 6.02% ~ 6.63%, and Mg, Mg, Mg and Pb are enriched in large ion lithophile elements such as Ba, Rb, Th, , Relative depletion of high field strength elements such as Ta, Nb, P, Ti, with positive Rb anomaly and obvious negative anomalies of Zr and Hf suggest that this andesite is a high-K calc-alkaline series of rocks with active continental margin volcanic rocks Is the magmatic product induced in the process of collision and collage between Lhasa terrain and Qiangtang terrain in the north of Bangong Lake-Nujiang Ocean. According to other data analysis, the diagenesis time of this andesite should be later than the diagenesis and metallogenic time of the high-low-temperature epithermal copper (gold) deposit in the Tiegulongnan deposit, which is an important condition for the deposit to be well preserved.