青藏高原中部阿索蛇绿岩岩石学与同位素年龄

    Petrology and geochronology of Asuo ophiolite in central Tibetan Plateau

    • 摘要: 阿索蛇绿岩位于尼玛县阿索乡西南,大地构造上归属于狮泉河-永珠-嘉黎蛇绿岩带中段。蛇绿岩以岩片形式混杂在晚侏罗世-早白垩世复理石中,岩石组合较齐全,由下至上为蛇纹岩、辉石岩、堆晶辉长岩、席状岩墙及火山熔岩,同时存在蛇绿岩上覆沉积岩系。辉长岩获得LA-ICP-MS锆石U-Pb谐和年龄为117.5±0.5Ma,时代为早白垩世。狮泉河-永珠-嘉黎蛇绿岩带中的蛇绿岩形成于晚三叠世-早白垩世,主要分布在219~178Ma、165~149Ma和117~114Ma三个年龄段,代表了大洋演化的扩张、俯冲、弧后拉张3个阶段。

       

      Abstract: Asuo ophiolite belongs to Shiquanhe-Yongzhu-Jiali ophiolite zone, located in southwestern Asuo County. The rock combination is complete, and consists from the bottom to the top of serentine, pyroxenite, cumulate gabbro, mafic dyke swarms and volcanic lava, with the existence of sedimentary rocks overlying ophiolite. In this paper, LA-ICP-MS U-Pb dating was carried out for the zircons of the gabbro dyke of Asuo ophiolite. LA-ICP-MS zircon U-Pb dating of gabbro dyke yielded a concordant age of 117.54±0.58Ma, indicating that it was formed in the Early Cretaceous.The ophiolite of Shiquanhe-Yongzhu-Jiali ophiolite zone was formed in Late Triassic to Early Cretaceous and mainly distributed in three age groups of 219~178Ma, 165~149Ma and 117~114Ma, representing the ocean expansion, subduction and back-arc extension respectively.

       

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