天山两侧山前新生代构造变形特征及其成因刍议

摘要：天山两侧山前新生代构造变形强烈,是研究盆山耦合动力学机制的理想场所。文中在综合分析前人资料基础上,结合作者的野外观测和分析,综述了天山两侧盆山转换部位不同段的新生代构造变形特征,并进行对比分析。结果显示,新生代构造变形在天山南北山前相似性和差异性共存:变形由山体向盆地扩展,时间逐渐变新;但是南侧比北侧变形起始时间早,地壳缩短量和缩短率大。在东西方向上新生代构造变形也存在明显的分段相似性特征,整体上显示出斜方对称的变形图像:东天山博格达山前为基底式逆冲推覆,南侧为走滑变形;中天山南北两侧为多排子的褶皱 逆冲推覆构造,西天山南侧也为基底式的逆冲推覆,北侧为走滑变形。综合前人研究,认为印度和亚洲大陆的碰撞及其随后陆陆汇聚作用的远程效应,是形成天山两侧山前新生代构造变形在南北方向上相似性和差异性的主要原因;而天山山体内部先存的相对刚性地块和大型断裂,则导致了新生代构造变形的东西向分段差异性和斜方对称的特征。

Characteristics of the Cenozoic deformation in basin/range coupling regions on both sides of Tianshan Mountains and its geodynamics

Abstract: Cenozoic deformation is well developed in the basin/range coupling regions on both sides of Tianshan Mountains, where is also a natural laboratory for studying the coupling dynamics of basin and range. Based on the comprehensive analysis of prior data and field measurements, and the analyses by ourselves, we mainly present in this paper the characteristics of Cenozoic deformation in both sides of Tianshan Mountains. It is obvious that the Cenozoic deformation in the south and north sides of Tianshan Mountains are both similar and different. The deformation transferred from the range to the basin, and the initiative time of the deformation in the south side is older than that in the north, and the crustal shortening and its rate in the south are larger than those in the north. The deformation in both sides also shows a segmental similarity in EW direction, displaying a special deformation pattern of rhombic symmetry. Basement thrust systems are developed in the north side of Bogda Mountain (eastern Tianshan Mountains) and in the southwest side of western Tianshan Mountains. Strike slip faulting took place not only in the south of the eastern Tianshan Mountains, but also in the north of the western Tianshan Mountains. Series of rows composed of folds and thrust systems grow on both sides of the central Tianshan Mountains. The comprehensive study suggests that the similarity and difference of the deformation resulted from the far distance effect of the collision between the India and Asia Blocks and convergence afterward, and the early preserved relatively rigid pre Paleozoic blocks and large scale fault systems within the Late Paleozoic Tianshan orogeny led to the formation of the Cenozoic deformation pattern of rhombic symmetry.