东准噶尔晚古生代洋陆转换过程:来自沉积学的约束

Late Paleozoic ocean-continent conversion in eastern Junggar:constraints from sedimentology

东准噶尔卡拉麦里造山带是中亚造山带西段一个很重要的构造单元,其构造演化为区域构造过程、动力机制等问题的研究提供关键证据,也为研究中亚造山带提供了重要的物质基础和理论依据。本文在前人研究的基础上,通过对卡拉麦里造山带野外剖面实测、构造现象描述、典型岩石观察,选取典型复理石、磨拉石建造剖面及古生物化石开展系统研究,结果表明:①白碱沟—红尖山卡拉麦里组复理石建造为巨厚的海相地层,是碰撞前的产物;②双井子地区松卡尔苏组顶部发育磨拉石建造,是造山后快速堆积的产物,基本代表了区内碰撞作用的开始,巴塔玛依内山组火山岩的形成时间晚于磨拉石盆地的形成时间;③卡拉麦里地区洋陆转换时间为343.5 Ma—339.0 Ma±,之后随着板片断离和俯冲板块后撤,区内进入后碰撞演化阶段。

The Kalamaili orogenic belt is a very important tectonic unit in the western part of the central Asian orogenic belt.Based on the previous studies it's tectonic evolution,regional tectonic process,dynamic mechanism and sedimentology are systematically studied in this paper.Sections were measured,structural phenomenon described,typical flysch,molasse sections of Kalamaili formation and paleontological fossils were dealt with detailly.The results show that the tremendous thick flysch formation of Kalamaili formation in Baijiangou-Hongjianshan area is marine strata of the pre-collision sediments,the molasse formation on top of Songkalsu formation in Shuangjingzi area is post-orogenic product of rapid sedimentation representing beginning of collision of the area,volcanic rock of the Batamayinnei shan formation was formed later than the molasse basin combined with the chronological dats,the ocean-continent conversion took place about 343.5 Ma-339.0 Ma ago then the subduction retreated with separation of the plate slice.