新生代柴达木盆地与周缘造山带的构造耦合

新生代以来，中国西部的一系列古老造山带和盆地在印-亚板块汇聚作用下重新复活，在青藏高原外围形成了现今全球最大的陆内挤压构造域，被称为环青藏高原盆山体系，其形成过程与机制对深入认识陆-陆碰撞如何影响大陆内部变形有重要意义。柴达木盆地是中国西部重要的新生代沉积盆地，四周均被巨型造山带所围限，共同构成了环青藏高原盆山体系北东段的主体。本文利用最新的石油地震勘探数据、地表地质和已发表的深反射地震数据，将上地壳变形与岩石圈深部变形有机结合，系统刻画了柴达木盆地与周缘三大造山带之间岩石圈尺度的构造耦合关系，在此基础上探讨环青藏高原盆山体系北东段的盆山汇聚过程与机制。柴达木盆地与南侧祁曼塔格—东昆仑山、北东侧南祁连山之间在上地壳尺度发育一系列倾向造山带的基底卷入高角度逆断裂体系，自新生代早期就开始活动，以垂直的基底抬升为主，水平缩短量有限；在下地壳和岩石圈地幔深度则发育倾向盆地一侧的深大断裂，使得柴达木盆地与周缘造山带之间发生截然的莫霍面错断。这些变形特征揭示柴达木盆地与南侧祁曼塔格—东昆仑山、北东侧南祁连山之间发育岩石圈尺度的构造楔，即盆地的岩石圈楔入至增厚的造山带下地壳，其发育主要受盆地与造山带...

Structural coupling between the Qaidam basin and bordering orogenic belts in the Cenozoic

A series of old orogenic belts and basins were rejuvenated in the context of Cenozoic India- Asia convergence forming in the periphery of the Tibetan Plateau the largest intracontinental compressional zone, which is named as the circum- Tibetan Plateau basin and orogen system (CTPBOS). The formation process and underlying mechanism of the CTPBOS are of large significance in advancing our knowledge of how continental collision impacts deformation in the interior of a continent. The Qaidam basin is an important Cenozoic sedimentary basin in West China, and bordered by huge orogenic belts. They together form the main body of the northeastern part of the CTPBOS. In this study, we combined the upper- crustal and deep (Moho) deformation through latest exploration seismic data, surface geology and published deep geophysical imaging, portrayed the structural coupling between the Qaidam basin and the three surrounding orogenic belts in the lithospheric scale, and accordingly explored the basin- mountain convergence process and underlying mechanism of the CTPBOS. In upper- crustal scale, a set of basement- involved, high- angle reverse faults developed in the conjunction regions of the Qaidam basin and the Qiman Tagh- East Kunlun Shan to the south and the South Qilian Shan to the northeast. These faults, which generally dip toward the mountains, are dominated by vertical basement rise with limited horizontal shortening, and were initiated in the Early Cenozoic. In the lower crust and lithospheric mantle, deep faults dipping toward the basin developed and offset the Moho of the Qaidam basin and adjacent mountains. These observations imply lithospheric- scale wedge tectonics, which are characterized by the Qaidam lithosphere tapering into the thickened lower crust of the Qiman Tagh- East Kunlun Shan and the South Qilian Shan, and formed in response to the lateral heterogeneity of the lithospheric strength between basins and orogenic belts. Different from the above contraction- dominated basin- orogen systems, the Qaidam basin and the Altyn Shan to the northwest are simply separated by the huge sinistral lithospheric- scale Altyn Tagh fault, which served as the lateral slip boundary during the formation and deformation of the Qaidam basin.