藏东拉荣斑岩钨钼矿床辉钼矿Re-Os定年及地质意义

Molybdenite Re-Os dating of the Larong porphyry W-Mo deposit in eastern Tibet and its geological significance

拉荣钨钼矿床位于类乌齐-左贡成矿带的东南部,是藏东地区发现的首例大型斑岩型钨钼矿床。其成矿地质背景尚缺乏成矿年龄制约。本文对拉荣矿床含矿石英脉中的辉钼矿进行Re-Os定年,6件样品的模式年龄集中于91.5±1.3~92.3±1.3 Ma,其加权平均年龄为91.8±0.5 Ma,等时线年龄为90.6±2.1 Ma,表明拉荣钨钼矿床成矿时代为晚白垩世。辉钼矿样品的Re含量为53.0×10^-6~86.1×10^-6,表明成矿物质具有壳幔混源的特征。拉荣钨钼矿床成矿年龄指示了班公湖-怒江构造带北东侧类乌齐-左贡成矿带内存在一期晚白垩世的钨多金属成矿事件,成矿作用发生于拉萨-羌塘地体碰撞造山阶段。

The Larong W-Mo deposit, located in the southeastern part of the Leiwuqi-Zuogong metallogenic belt, is the first giant porphyry W-Mo deposit discovered in eastern Tibet. The metallogenic setting of this deposit is unclear due to lack of constraints on metallogenic chronology. Six samples of molybdenite from ore-bearing quartz veins were carried out for Re-Os isotopic dating, and the model ages obtained range from 91.5±1.3 Ma to 92.3±1.3 Ma, with an isochron age of 90.6±2.1 Ma and a weighted mean age of 91.8±0.5 Ma, indicating that the mineralization of the Larong deposit occurred at the Late Cretaceous. The Re content of molybdenite ranges from 53.0×10^-6 to 86.1×10^-6, suggesting that the metallogenic material originated from a crust-mantle mixed source. The metallogenic age of the Larong W-Mo deposit indicates that the Later Cretaceous tungsten polymetallic mineralization event occurred in the Leiwuqi-Zuogong metallogenic belt in the northeastern section of Bangonghu-Nujiang tectonic belt, with mineralization occurring in the Lhasa-Qiangtang collisional orogenic setting.