塔里木盆地孔雀河斜坡尉犁断鼻构造的构造特征与形成演化

Tectonic features,formation and evolution of Yuli fault nose-shaped structure of Kongquehe slope,Tarim Basin

孔雀河斜坡位于塔里木盆地的东北部,其成因与南天山和阿尔金山的地质作用密切相关。尉犁断鼻构造位于孔雀河斜坡西北部,完整地记录了孔雀河斜坡的构造演化历史,该断鼻构造特征的解析对揭示塔里木盆地东北缘早古生代以来的地球动力学背景具有重要的意义。本文利用断层相关褶皱理论,通过对过孔雀河斜坡尉犁断鼻构造带地震剖面的精细解释,分析了该断鼻构造的构造特征与形成演化,并讨论了其成因机制。尉犁断鼻构造在北西—南东向上为一古生界背斜,北西翼较陡,南东翼稍缓,背斜核部上古生界被剥蚀,并被后期由北向南的冲断层所切割。该构造主要反映了3期构造事件的叠加:中奥陶世-晚奥陶世,受北西—南东向挤压应力的影响,形成了北东—南西向展布的背斜;志留纪—二叠纪,受南天山洋消减、闭合向南产生的挤压应力的影响,尉犁背斜北部持续地抬升剥蚀,形成鼻状构造;侏罗纪,燕山早期运动影响了古生界和中生界,并使得北西西走向的南冲断层重新活动,错断了先存的鼻状构造。研究认为,尉犁断鼻构造北东—南西向展布的背斜在中奥陶世就开始形成,其主应力可能来自盆地东南的阿尔金山方向,与北阿尔金洋在加里东期运动时的俯冲与碰撞造山对该区域的远程挤压作用有关;伴随着基底叠瓦构造往北西方向前展,背斜向北西移动了104km,基底缩短率为48.4%。

Kongque slope is located in the northeastern part of Tarim Basin, and its formation is closely related to the south Tianshan and the Altun Mountain. Yuli fault nose-shaped structure, located in the northwestern part of Kongquehe slope, completely records the tectonic evolution of Kongquehe slope, the interpretation and analysis of the fault nose-shaped structure is very important to reveal the geodynamic settings of the northeastern margin of Tarim Basin since Early Paleozoic. Through the fine interpretation of the seismic profile across Yuli fault nose- shaped structural zone, using the theory of fault-related fold, this paper analyzed the tectonic features and the formation and evolution of the fault nose-shaped structure, and discussed the genetic mechanism. Yuli fault nose-shaped structure is a Paleozoic anticline in the NW-SE direction, which is cut by the late thrust from north to south. The northwest wing of the anticline is steep and the southeast wing is a little slow, the Upper Paleozoic strata of the anticline core are denudated. This structure mainly reflects the superimposition of three tectonic events： Middle to Late Ordovician,the NE-SW direction spreading anticline formed by the affection of the NW-SE direction stress; Silurian to Permian, being affected by the compressive stress generated in the subtractive and the closure of the south Tianshan ocean, the Yuli anticline became to the nose-shaped structure with the uplift and denudation of its northern part; Jurassic,the Early Yanshanian movement affected the Paleozoic and Mesozoic strata,and madethe southward thrust whose strike direction is NWW removed,which offset the pre-exist noseshaped structure. This research thinks the NE-SW direction spreading anticline of Yuli fault nose-shaped structure was being formed in Middle Ordovician, the principle stress may came from the Altun Mountain, southeast to Tarim Basin, the formation was related to the remote compression generated in the subduction and collision of the north Ahun ocean in Caledonian ; Combined with the basement imbricate structure breaking-forward northwestwardly, the anticline moved 104 kilometers northwestwardly,the basement shortened 48.4%.