Underthrusting of Tarim Lower Crust Beneath the Tibetan Plateau Revealed by Receiver Function Imaging

• Published in: Geophysical research letters Vol. 51; no. 2
• Main Authors: Wu, Chenglong, Xu, Tao, Tian, Xiaobo, Mitchell, Ross N., Lin, Jiyan, Yang, Jianfeng, Wang, Xin, Lu, Zhanwu
• Format: Journal Article
• Language: English
• Published: Washington John Wiley & Sons, Inc 28.01.2024; Wiley
• Subjects: Altyn Tagh Range; Arrays; Crustal structure; Deformation; eclogitization; Extrusion; Fault lines; Geological faults; Interfaces; Miocene; Moho; Plateaus; receiver function; Seismic data; Seismological data; Thrust faults; Tibetan Plateau; underthrust; Uplift; Tibetan Plateau
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1029/2024GL108220

The left‐lateral Altyn Tagh Fault (ATF) system is the northern boundary of the Tibetan Plateau resulted from the India–Eurasia continental collision. How intracontinental deformation across the central ATF responds to the distal collision remains elusive, primarily due to unclear crustal structure. We obtained detailed crustal structure across the central ATF using receiver functions recorded by ∼NW–SE oriented linear dense array. The images reveal the Tarim lower crust is underthrusting beneath the Tibetan Plateau and reaches to a maximum depth of ∼75 km and undergoing partial eclogitization. The two south‐dipping interfaces imaged beneath the Altyn Tagh Range (ATR) represent the thrusting Northern Altyn Fault and its branch fault. Oblique convergent forces extruded upper crustal materials along the thrust faults, creating the pop‐up structure of ATR, supported by low Vp/Vs ratios. Our balanced cross‐section for the Moho suggests intracontinental deformation in the ATR has accelerated since the late Miocene. Plain Language Summary The Altyn Tagh Fault (ATF), serving as the northern boundary of the Tibetan Plateau, demarcates the Tarim Basin from the Qaidam Basin. Understanding how intracontinental deformation across the boundary region would better inform the uplift and expansion of the plateau. This study reveals the fine crustal structure by analyzing seismic data from a ∼NW–SE oriented linear dense array across the central ATF. Combined with fault slip rates, we propose that the Tarim lower crust is underthrusting beneath the Tibetan Plateau, leading to the extrusion of upper crustal materials and the rapid uplift of the Altyn Tagh Range since the late Miocene, which provides insight into the lateral growth of the plateau. Key Points Detailed crustal structure beneath the central Altyn Tagh Fault was imaged by receiver functions of a dense 2‐D seismic array The Tarim lower crust is underthrusting to ∼75 km depth beneath the Tibetan Plateau The Altyn Tagh range was uplifted rapidly since late Miocene through the thickening of the upper crust