新疆东部莫钦乌拉山尤尔敦蛇绿混杂岩主要特征及构造意义

Main Characteristics and Tectonics Significance of the Youerdun Ophiolitic Melange in the Moqinwula Mountains,Eastern Xinjiang

莫钦乌拉山尤尔敦蛇绿混杂岩位于天山山脉东北部莫钦乌拉山,该区构造上为东准噶尔卡拉麦里构造带的向东延伸。通过野外地质调查、地球化学和年代学研究,初步查明尤尔敦蛇绿混杂岩基质与外来岩块的主要特征。基岩岩石化学特征表明,洋岩石圈残片形成于弧相关盆地,获得洋壳辉长岩锆石U-Pb年龄为(411.5±2.7)Ma。结合前人资料和区域地质特征,认为尤尔敦蛇绿混杂岩所代表的洋盆是卡拉麦里有限洋盆的向东延伸,形成于早—中泥盆世,晚泥盆世开始俯冲消减,于石炭世晚期闭合。

The geotectonics of the ophiolite melange in Yourdun is located in the Mochin Ural Mountains,northeast of the Tianshan Mountains,The structure of this area is generally considered as the eastward extension of Karamaili structur-al belt in eastern Junggar.Through field geological surveys,indoor geochemistry,and chronologic studies,The main char-acteristics of Matrix and exotic blocks of the Youerdun Ophiolitic melange have been found out preliminarily.The petro-chemical characteristics of the basic rocks indicate that the oceanic lithosphere fragments were formed in the arc-related basin,the U-Pb Zircon age of Oceanic Crust Gabbro is(411.5±2.7)Ma.Based on the previous data and the regional geo-logical characteristics,this paper holds that the Ultun ophiolitic melange represents an eastward extension of the Kara-maili Limited Ocean Basin,formed in the early-middle Devonian,and subducted and subducted in the late Devonian,and closed in the late carboniferous.