Asthenospheric Flow Channel From Northeastern Tibet Imaged by Seismic Tomography Between Ordos Block and Yangtze Craton

Abstract

The Tibetan Plateau has been formed by the collision between India and Eurasia since the early Cenozoic, and the crust between them has been shortened more than 1,400 km since the onset (Yin & Harrison, 2000). The crustal shortening after the collision is accommodated by the uplift and thickening of the crust and large strike-slip faults, resulting in a plateau of 5,000 m high on average with up to 80-km thick crust. Models have been proposed to explain the surface uplift and the crustal deformation, such as the shear between coherent lithospheric blocks (e.g., Tapponnier et al., 2001), continuous deformation across the plateau (England & Houseman, 1986), and lower crustal flow (e.g., Royden et al., 2008). All the models predict an eastward extrusion of crustal or upper-mantle lithospheric materials beneath the Tibetan Plateau. The collision and shortening have also inevitably led the asthenosphere to escape eastward from the Tibetan Plateau

Uppermost Mantle Seismic Pn‐Velocity in Continental China and Its Tectonic Implications

“…We attribute these relatively lower Pn ‐velocities to the possible extrusion of hot asthenospheric flow from the Tibetan Plateau, likely related to far‐field effects of the India‐Eurasia collision (Liu et al., 2004; Ren et al., 2002; Tang et al., 2006). Such an interpretation is consistent with reported high‐conductivity bodies in the lower crust and the uppermost mantle (Dong et al., 2014; Li et al., 2022; Xue et al., 2019), low body wave velocity anomaly at depths ranging from 150 to 300 km (Hu & Wang, 2018; Lei & Zhao, 2016; Yu et al., 2021), anomalous SKS delay time and fast polarization direction (Huang et al., 2008; Yu & Chen, 2016), and rapid rock exhumation (Enkelmann et al., 2006; Shi et al., 2016, 2019; Su et al., 2021; Yang et al., 2013, 2017; Zheng et al., 2006) in the regions.…”

“…In the east, the subduction and rollback of the Paleo‐Pacific plate probably induced upwelling of hot materials in a mantle wedge (e.g., Lei & Zhao, 2005, 2006; Lei et al., 2013; Li et al., 2015; Zhu et al., 2011, 2012) and extensive magmatism in the region (e.g., Deng et al., 2017; Pirajno et al., 2009; Zhou et al., 2006), which may have modified the thermochemical structure of the lithosphere. In the west, the India‐Eurasia collision probably resulted in underthrusting of the Indian lithosphere beneath the Tibetan Plateau (e.g., Bao & Shen, 2020; Ceylan et al., 2012; M. Chen et al., 2017; He et al., 2018; Replumaz et al., 2014; Zhao et al., 1993), northward subduction of the Lhasa block beneath the Qiangtang block (e.g., Bao & Shen, 2020; Ding, 2003; Yin & Harrison, 2000; Yue et al., 2012), extrusion of asthenospheric flow (e.g., Flower et al., 2001; Huang et al., 2008; Yu & Chen, 2016; Yu et al., 2021), lithospheric removal (e.g., Chung et al., 2005; Ding et al., 2022; Huang et al., 2019; Lei & Zhao, 2007; Royden et al., 2008; Yin, 2010), subduction of the Indian oceanic slab beneath the Burma arc down to the mantle transition zone (e.g., Lei & Zhao, 2016; Lei et al., 2009; Li et al., 2008; Xu et al., 2018), upwelling of hot materials in a mantle wedge beneath the eastern Tibetan Plateau (e.g., Lei & Zhao, 2016; Lei et al., 2009, 2013, 2019) and large relative movement between adjacent blocks (e.g., Gan et al., 2007; Pan et al., 2018). On a local scale, the interaction between the North China, Yangtze, and northern Tibetan blocks during the closure of the Paleo‐Tethys ocean resulted in a drastic orogeny in the Songpan‐Ganzi block during the Triassic (e.g., Pullen et al., 2008; Roger et al., 2010; Yin & Harrison, 2000) and possibly caused lithospheric thickening and removal of the lithosphere (e.g., Yuan et al.,…”

“…northward subduction of the Lhasa block beneath the Qiangtang block (e.g., Bao & Shen, 2020;Ding, 2003;Yin & Harrison, 2000;Yue et al, 2012), extrusion of asthenospheric flow (e.g., Flower et al, 2001;Huang et al, 2008;Yu & Chen, 2016;Yu et al, 2021), lithospheric removal (e.g., Chung et al, 2005;Ding et al, 2022;Huang et al, 2019;Lei & Zhao, 2007;Royden et al, 2008;Yin, 2010), subduction of the Indian oceanic slab beneath the Burma arc down to the mantle transition zone (e.g., Lei & Zhao, 2016;Lei et al, 2009;Li et al, 2008;Xu et al, 2018), upwelling of hot materials in a mantle wedge beneath the eastern Tibetan Plateau (e.g., Lei & Zhao, 2016;Lei et al, 2009Lei et al, , 2013Lei et al, , 2019 and large relative movement between adjacent blocks (e.g., Gan et al, 2007;Pan et al, 2018). On a local scale, the interaction between the North China, Yangtze, and northern Tibetan blocks during the closure of the Paleo-Tethys ocean resulted in a drastic orogeny in the Songpan-Ganzi block during the Triassic (e.g., Pullen et al, 2008;Roger et al, 2010;Yin & Harrison, 2000) and possibly caused lithospheric thickening and removal of the lithosphere (e.g., Yuan et al, 2010;.…”

Distinct Lithospheric Structures of the Ordos Block and Its Margins From P and S Receiver Functions and Its Implications for the Cenozoic Lithospheric Reworking

“…Previous studies show contrary lithospheric structures beneath the Qinling orogen (Bao et al., 2015; Huang et al., 2009; Jiang et al., 2013; Zhao et al., 2012). Our observations of dramatically thin lithosphere beneath the Weihe rift and northern Qinling orogen provide direct evidence for the asthenospheric flow channel as suggested in SKS splitting and body wave tomography (Yu & Chen, 2016; Yu et al., 2021). Although the body wave tomography usually has low vertical resolution compared to RFs, both body wave tomography and receiver function results reveal relatively thin lithosphere beneath the Weihe rift and northern Qinling orogen and thick lithosphere beneath the northern Yangtze block and Ordos (Figure 4b).…”

“…The red arrows denote the different mantle flow patterns at the northern and southern margins of the Ordos. (b) S‐wave tomographic image along the longitude 109°E (Yu et al., 2021). The LAB depth identified from our SRFs migration image is projected onto the cross‐section as yellow dashed lines.…”