西藏泽当蛇绿岩物质组成、年代格架及地质意义

Material composition,chronological framework and geological significance of the Zedang ophiolites in Tibet

蛇绿岩带出现于全球大多数碰撞构造带上,通常是板块缝合带的标志。泽当蛇绿岩位于雅鲁藏布江蛇绿混杂岩带的东段,沿雅鲁藏布江河谷南侧断续出露,由地幔橄榄岩、辉长岩、玄武岩等组成。本文在研究区内对泽当蛇绿岩进行了系统的调查,采集了大量的薄片及同位素年龄样。结合前人研究,结果显示,泽当蛇绿岩物质组成较复杂,由不同的岩石构造单元组成,其中地幔橄榄岩以方辉橄榄岩为主,泽当蛇绿岩的形成时代主要集中在162~130Ma之间,属晚侏罗-早白垩世,岩石学、岩石地球化学等表明,泽当蛇绿岩属俯冲带上盘型(SSZ)蛇绿岩。

Ophiolites belt occur in most of collisional chains around the world and generally mark the suture zone between plates of geological distinctive origins.Zedang ophiolite is located in the eastern part of the Yarlung Zangbo ophiolite melange belt,intermittently exposed along the southern side of the Yarlung Zangbo River Valley.The Zedong ophiolite is composed of mantle peridotite,gabbro and basalt.With the Zedang ophiolite has been systematically investigated,a large number of slice and isotopic age samples have been collected.Based on the previous literature,the results showed that,Zedang ophiolite is composed of different rock formation units,and the composition of matter is more complicated.The peridotite is the main body of mantle peridotite,the age of Zedong ophiolite is mainly concentrated in 130~162 Ma,belong to Late Jurassic-Early Cretaceous.Petrology and petrogeochemistry indicate that the Zedang ophiolite belongs to the Suprasubduction-zone(SSZ)type ophiolite.