Role of the Early Miocene Jinhe-Qinghe Thrust Belt in the building of the Southeastern Tibetan Plateau topography

Abstract

Understanding the role of southeastern Tibet thrust faults in the development of the plateau topography is key to our assessment of the geodynamic processes shaping the continental topography. Detailed structure analysis along the ~400 km long Jinhe-Qinghe thrust belt (JQTB) indicates post late Eocene thrust motion with a minor left-lateral component, inducing ~0.6 to 3.6 km of apparent vertical offset across the fault. The exhumation history of the Baishagou granite, based on the thermal modeling (QTQT) of new apatite (U-Th)/He and fission-track ages, suggests an accelerated exhumation rate (~0.42 km/Myr) between 20 and 15 Ma, corresponding to ~1.7-2.4 km of exhumation. We interpret that fast exhumation as due to the activation of the Nibi thrust, a northern branch of the JQTB resulting in the creation of significant relief across the JQTB in the Early Miocene. When compared with previous studies it appears that Cenozoic exhumation and relief creation in southeastern Tibet cannot be explained by a single mechanism. Rather, at least three stages of relief creation should be invoked. The first phase is an Eocene NE-SW compression partly coeval with Eocene sedimentation. During the Late Oligocene to Early Miocene, coevally with Indochina extrusion, the second thrusting phase occurred along the Yulong and Longmenshan thrust belts, and then migrated to the JQTB at 20-15 Ma. A third phase involved the activation of the Xianshuihe fault and the re-activation of the Longmenshan thrust belt and the Muli thrust. Uplift in the hanging wall of thrust belts appears to explain most of the present-day relief in the southeastern Tibetan Plateau.

Middle–Late Cenozoic Stepwise Deformation Propagation in Eastern Tibet

“…The Songpan–Ganzi terrane was thrust to the east onto the Yangtze Block to form a foreland basin along the Sichuan‒Xichang‒Chuxiong area during the Late Triassic–Cretaceous (Deng et al., 2018; Huang et al., 2019; Z. K. Yan et al., 2018). The Longmen Shan and Yalong thrust belts were reactivated during the Cenozoic with the eastward growth of the Tibetan Plateau (E. Wang et al., 2012; S. F. Wang et al., 2012; H. P. Zhang et al., 2016; C. Y. Zhu et al., 2021). These NE thrust faults with a series of NNW strike‐slip faults (such as the Ailao Shan–Red River, Gaoligong, and Chongshan shear zones, while the Xianshuihe–Xiaojiang and Sagaing faults [Figure 1]) dominated the deformation pattern across eastern Tibet (Chen & Wilson, 1996; Sichuan BGMR, 1991; E. Wang et al., 1998; Xu et al., 2015; Yunnan BGMR, 1990).…”

“…Furthermore, an increasing amount of data from studies on sedimentology, thermochronology, and paleoelevation across eastern Tibet indicate that surface uplift began before the Latest Eocene (Cao et al., 2019; Hoke et al., 2014; S. Y. Li et al., 2015; Liu‐Zeng et al., 2018; E. Wang et al., 2012; Z. Y. Xiong et al., 2020; Z. Yang et al., 2017; H. P. Zhang et al., 2016). The Early Cenozoic deformation in eastern Tibet could have been accommodated through deformation mainly along the major boundary faults, including the Yulong‒Yalong‒Longmen Shan thrust belt and the Ailao Shan‒Red River shear zone (Figure 1; Cao et al., 2019; Gilley et al., 2003; Leloup et al., 1995, 2001; E. Wang et al., 2012; Y. Wang et al., 2020; H. P. Zhang et al., 2016; C. Y. Zhu et al., 2021). Therefore, some studies explained that the northward indention of the Eastern Himalayan Syntaxis could have triggered the initiation of early‐stage Cenozoic faulting in eastern Tibet (Schoenbohm, Burchfiel, & Chen, 2006).…”

“…However, the Muli thrust was suggested to have underwent exhumation at ∼13 Ma (Clark et al., 2005; Pitard et al., 2021). Additionally, it was reported that the initial fast exhumation and deformation of the Jinhe‒Qinghe thrust is constrained to the Middle Miocene (20–16 Ma) (S. F. Wang et al., 2012; C. Y. Zhu et al., 2021). Therefore, the deformation time and spatial pattern of the Yalong thrust belt are still uncertain, and the formation of topographic relief across this belt is likewise unclear.…”

“…However, the Muli thrust was suggested to have underwent exhumation at ∼13 Ma (Clark et al, 2005;Pitard et al, 2021). Additionally, it was reported that the initial fast exhumation and deformation of the Jinhe-Qinghe thrust is constrained to the Middle Miocene (20-16 Ma) (S. F. C. Y. Zhu et al, 2021).…”

Hydrogeochemical origin and circulation of spring waters along the Karakorum fault, Western Tibetan Plateau: Implications for interaction between hydrosphere and lithosphere

“…The India-Eurasia continental collision, ongoing since ca. 60-50 Ma (Molnar and Tapponnier, 1975;Hu et al, 2015;Zhu et al, 2021), has created the Tibetan Plateau. Many mediumto high-temperature geothermal resources have developed in the Tibetan Plateau (Figure 1A) located in the Himalayas geothermal belt, which is an important part of the Mediterranean-Himalayas geothermal belt (Guo, 2012) and provides ideal systems for studying the deep-time interaction between the lithosphere and hydrosphere.…”