Earth Science Frontiers ›› 2023, Vol. 30 ›› Issue (5): 334-357.DOI: 10.13745/j.esf.sf.2023.8.16

Previous Articles     Next Articles

Late Cenozoic deformation characteristics and mechanism of the Beishan-Alxa region

ZHANG Jin1,2(), ZHANG Beihang3, ZHAO Heng1,2, YUN Long4, QU Junfeng2, WANG Zhenyi2, YANG Yaqi5, ZHAO Shuo2   

  1. 1. MNR Laboratory of Deep Earth Sciences and Technology, Beijing 100037, China
    2. Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China
    3. Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou 730000, China
    4. Beijing Research Institute of Uranium Geology, Beijing 100029, China
    5. MOE Key Laboratory of Karst Georesources and Environment, College of Resources and Environmental Engineering, Guizhou University, Guiyang 550025, China
  • Received:2023-08-01 Revised:2023-08-16 Online:2023-09-25 Published:2023-10-20

Abstract:

The Beishan-Alxa region is located in the middle segment of the Central Asian Orogenic Belt. This region, controlled by the Indian-Eurasian collision in the Late Cenozoic, has undergone intracontinental deformation to varying degrees. It is a stress transfer area between the Qinghai-Tibetan Plateau and the Mongolian Plateau, and a key area to study the remote effects of the Indian-Eurasian collision. Differing from the Late Cenozoic deformation in the Tianshan/Altai regions in the western segment of the Central Asian Orogenic Belt, the Beishan-Alxa region developed a set of near EW-trending left-lateral strike-slip faults, and between them a series of NE-trending normal faults were developed which control faulted depression (pull-apart) basins. The much larger near EW-trending faults, with a long strike extension, become the main structure of Late Cenozoic deformation in this region. On the whole, the deformation is in the step area between the NEE-trending South Mongolian-Tianshan left-lateral strike-slip fault on the north side, and the NEE-trending Altyn Tagh fault on the south side. In this left-lateral left-step area, the deformation is manifested as nearly E-W secondary strike slip faults (P shear), derived from the boundary strike-slip faults and the NE extensional basins (such as the Ejina basin, Jiujing basin). Under sinistral transtensional setting this area develops a sinistral shear structure distinct from the dextral shear structure of the Mongolian Gobi Altai; while its flat landform, developed under regional extension within the step area, makes it the main catchment basin area in the Beishan-Alxa region. The GPS velocity field and anisotropy data of the upper mantle-lower crust indicate the Tarim Craton plays an important role in the northward expansion of the Qinghai-Tibetan Plateau. At the Tarim Craton the upper mantle-lower crust of the Qinghai-Tibetan Plateau turns northeastward along the southeastern edge of the craton while the Tarim continues to exert stress northeastward, leading to the rise of the Tianshan mountain range and northward compression of the Junggar Basin to cause NNW-trending dextral shear deformation in the Altay Mountains. On the other hand, the northward movement of the upper mantle-lower crust causes Late Cenozoic sinistral shear deformation in the Beishan-Alxa region and southern Mongolia. Deformation in the Beishan-Alxa region is widespread, which is different from Cenozoic deformation in the Tarim-Tianshan-Junggar region where deformation is concentrated in the Tianshan and Altay Mountains.

Key words: Beishan-Alxa, Late Cenozoic, Qinghai-Tibetan Plateau, intracontinental deformation, deformation mechanism

CLC Number: