塔里木地块-柴达木地块碰撞相关的同碰撞和碰撞后构造——塔里木盆地地震资料解释成果

位于塔里木盆地南侧的阿尔金山和西昆仑山是特提斯超级造山带最北部的两条缝合带。该处的早古生代造山作用是原特提斯构造演化的重要组成部分。根据地震资料解释在塔里木盆地发现的碰撞相关构造指示, 早古生代的碰撞事件发生于塔里木地块的东南侧, 是塔里木地块与柴达木地块之间的碰撞造山作用。这次碰撞形成了阿尔金早古生代碰撞造山带。其同碰撞构造主要包括前陆褶皱冲断带(塘沽孜巴斯前陆褶皱冲断带)和大型基底卷入型背斜构造(轮南、塔东和塔中背斜), 形成于晚奥陶世-早志留世。碰撞后构造为一系列正断层及其组合成的雁列状张扭性断层带, 形成时间是中志留世-中泥盆世。根据塔里木盆地内发现的碰撞相关构造分析, 结合造山带内的蛇绿岩和俯冲-碰撞相关岩浆岩、变质岩研究成果推论, 作为原特提斯洋分支的古阿尔金洋, 其洋壳自晚寒武开始向柴达木地块之下俯冲。至中奥陶世末-晚奥陶世初, 洋壳俯冲完毕, 古阿尔金洋闭合, 塔里木地块-柴达木地块碰撞开始。该碰撞造山作用持续至早志留世末结束, 然后进入中志留世-中泥盆世碰撞后应力伸展构造演化阶段。迄今, 尚无碰撞相关构造指示塔里木克拉通西南缘曾经发生早古生代碰撞造山事件。早古生代, 阿尔金山发生的是增生-碰撞型造山, 西昆仑山发生的是增生型造山作用。

The syn- and post-collision structures related to the Tarim-Qaidam collision: Results of seismic interpretation in the Tarim Basin

The Altun and West Kunlun Mountains, located on the southeast and southwest of the Tarim basin respectively, are two of the northernmost sutures of the Tethysides. The Early Paleozoic orogenic processes occurred there are important components of the Proto-Tethys history. After careful seismic interpretation, collision-related structures were revealed in the Tarim Basin. They indicate an Early Paleozoic collsion once occured on the southeastern margin of the Tarim Craton. That is the Tarim-Qaidam collision which resulted in the Altun Early Paleozoic collisional orogenic belt. The syn-collision structures in response to this collision include foreland fold-thrust belt (the Tangguzibas fold-thrust belt) and large basement-involved anticlines (the Lunnan, Tadong and Tazhong anticlines). They were formed in the Late Ordovician to Early Silurian. The post-collision structures are normal faults and theire combination of echelon transtensional fault zones. They were formed in the Middle Silurian to Middle Devonian. Deduced from the research results of the collision-related structures in the Tarim Basin and also the ophiolites and subduction-collison related magmatic and metamorphic rocks in the Altun Mountains, we can conclude that the oceanic crust of the ancient Altun Ocean, a branch of the Proto-Tethys, subducted under the Qaidam block since the Late Cambrian when is also the beginning time of the closing history of the oceanic basin. The acient Altun oceanic basin finaly closed at the end of the Middle Ordovician and resulted in the Tarim-Qaidam collision. This collision lasted to the end of the Early Silurian and then seased and evolved into the Middle Silurian-Middle Devonian post-collsion extension tectonic stage. So far, there is no collision-related structure indicates an Early Paleozoic collision on the Tarim's southwestern margin. Therefore, in the Early Paleozoic, accretion-collision orogeny occurred in the Altun and accretionary orogeny in the West Kunlun.