西藏日土县狮泉河蛇绿混杂岩锆石U-Pb年龄及构造意义

Zircon U-Pb Age And Its Tectonic Significance of Shiquanhe Ophiolitic Mélange in Rito County,Tibet

本文对狮泉河蛇绿混杂岩中的辉长岩岩块、堆晶辉长岩岩块进行了锆石U-Pb年代学研究,确定了其形成时代,通过前人的资料及本次工作成果分析对比,探讨了狮泉河蛇绿混杂岩的构造意义。获得的锆石U-Pb谐和年龄集中在189Ma至180.2Ma,但在区内已发现的早侏罗世的花岗闪长岩,之中可见较多蛇绿岩的捕虏体,反映了狮泉河蛇绿岩形成时代可能更早。结合前人研究资料表明狮泉河洋的发育时限可能限定为晚三叠世晚期至晚白垩世早期,并可能于早侏罗世晚期已经开始发生俯冲,至早白垩世最终闭合。

In this paper,the zircon U-Pb geochronology of the gabbro and the gabbro diagene in the Shiquanhe ophiolitic mélange is studied,and the formation age is determined.The analysis and comparison of the results of the work were conducted to discuss the tectonic significance of the Shiquanhe ophiolite mélange.The obtained zircon U-Pb harmonic age is concentrated from 189 Ma to 180.2 Ma,but the early Jurassic granodiorite found in the area shows more ophiolites,which reflect the The formation of the Shiquanhe ophiolite may be earlier.Combined with previous research data,the developmental time limit of Shiquan River may be limited to the late Late Triassic to early Cretaceous,and may have begun to subduction in the late Early Jurassic,and finally closed in the early Cretaceous.