地质学报2017，Vol.91Issue(12)：2638-2650,13.
西准噶尔和布克赛尔古洋盆的厘定——来自和布克赛尔蛇绿混杂岩的锆石U-Pb年代学及地球化学证据
The Determination of Hoboksar Ancient Oceanic Basin in West Junngar: Evidence from Zircon U-Pb Age and Geochemistry of the Hoboksar Ophiolitic Mé11ange
摘要
Abstract
This study carried out detailed field mapping and indoor analysis of the Hoboksar ophiolitic mélange in northern West Junggar,which was poorly reported.The ophiolitic mélange with an area of about 4 km2 consists of serpentinized peridotite,pyroxenite,gabbro,dolerite,basalt,chert,marble and andesitic volcanic elastic rocks.Matrix consists mainly of serpentinized peridotite;the other components occur as faulting blocks or fragments and exhibit irregular fault contact with the matrix,being typical of contact relation of fragments enclosed by the matrix.Wall rocks,matrix and fragments have undergone various degrees of deformation and alteration,with foliation well developed within wall rocks and matrix.Geochemical analysis shows that the gabbro fragments of the Hoboksar ophiolitic mélange have slight fractionation between LREE and HREE,with (La/Yb)N of 0.48 ～ 0.65 and negligible Eu anomalies.HFSE (Zr ～ Lu) shows no fractionation and is characteristic of near MORB,suggesting the Hoboksar ophiolitic mélange belongs to MOR type.LA-ICP-MS U-Pb dating of zircons from the gabbro blocks yields an age of 484 ± 3 Ma,indicating that the ancient oceanic crust was developed in the Early Ordovician.New determination of time and attributes of the Hoboksar ophiolite mélange not only implies the at least one ancient ocean occurring between Boshchekul-Chingiz arc and Zharma-Saur arc in the early Ordovician,but also provides an important clue for study of tectonic evolution of northern West Jungger.The Hoboksar ophi0litic mélange correlates well with the reported Kujibai and Hongguleleng ophiolitic mélanges in northern West Junggar,but is different from the Qagan Tolgoi ophiolitic mélange in many aspects.Therefore,this study provides new constraints on the determination of the tectonic suture belt in West Junggar.关键词
西准噶尔/和布克赛尔蛇绿岩/构造混杂/LA-ICP-MS锆石U-Pb定年/早奥陶世Key words
West Junngar/Hoboksar ophiolite/mélange/LA-ICP-MS zircon U-Pb geochronology/Early Ordovician引用本文复制引用
都厚远,陈家富..西准噶尔和布克赛尔古洋盆的厘定——来自和布克赛尔蛇绿混杂岩的锆石U-Pb年代学及地球化学证据[J].地质学报,2017,91(12):2638-2650,13.基金项目
本文为国家自然科学基金(编号41202161,41672217)、高校基本科研业务费(编号N140104003,N140104004)资助的成果. （编号41202161,41672217）
