Crust and upper mantle structure of the North China Craton and the NE Tibetan Plateau and its tectonic implications

Present-Day Crustal Vertical Motion Around the Ordos Block Constrained by Precise Leveling and GPS Data

“…A high-resolution P-wave tomographic model demonstrated that under the Datong volcano in northernmost Shanxi graben, a prominent lowvelocity zone exists down to about 400 km depth (Huang and Zhao 2006). Body wave tomography (Tian and Zhao 2011) and S-wave velocity structure results Bao et al 2013) also show that low-velocity anomaly is imaged in the depths of 50-200 km beneath the northeastern margin of the Ordos block. The prominent lowvelocity zone is associated with upwelling materials from the mantle (Tian et al 2009;Yang et al 2012;Bao et al 2013), which may result in the rapid uplift around the northeastern Ordos block.…”

“…1) in the northernmost part of the Shanxi graben (Bao et al 2013). The main eruptive phase of basalts magma occurred during the middle Pleistocene (Li 1988;Bao et al 2013). …”

Two crustal low-velocity channels beneath SE Tibet revealed by joint inversion of Rayleigh wave dispersion and receiver functions

“…The mechanically weak midlower crust has also been supported by several lines of evidence from geophysical observations, such as intra-crustal LVZs (Bao et al, 2013;Ceylan et al, 2012;Fu et al, 2010;Li et al, 2008;Xu et al, 2013a;Xu and Song, 2010;Yang et al, 2012;Yao et al, 2008), low electrical resistivity in the mid-lower crust (Bai et al, 2010;Unsworth et al, 2005;Wei et al, 2001), high V p /V s ratios (Sun et al, 2014;Xu et al, 2007), high heat flow (Hu et al, 2000), and strong attenuation (Bao et al, 2011a;Zhao et al, 2013), indicating the existence of partial melt and viscosity reduction in the mid-lower crust and thus the possibility of crustal flow. In addition, strong positive radial anisotropy with faster horizontally polarized shear wave further suggests sub-horizontal alignment of mica and/or amphiboles in the crust due to ductile flow beneath SE Tibet (Huang et al, 2010;Shapiro et al, 2004;Xie et al, 2013).…”

Crustal and upper mantle structure beneath the northeastern Tibetan Plateau from joint analysis of receiver functions and Rayleigh wave dispersions

“…The NET experienced rapid uplift and active NE-SW shortening during the Late-Cenozoic (Chen et al 2000). The NET could be considered as a growing part of the plateau and the relatively higher velocity in the crustal LVZ in the NW Qilian orogen compared with that of the Songpan-Ganzi and Qiangtang terranes is considered as an indication of an early stage of the LVZ (Bao et al 2013). Based on zircon U-Pb geochronology and geochemistry study in Xiaoliugou located in the central part of NW Qilian orogen, Zhao et al (2014) reported that local monzogranite containing radioactive elements may indicate felsic magma in the crust.…”

“…Previous results of surface wave tomography and receiver functions suggest that the crust and mantle structure in the NET is very heterogeneous (e.g. Bao et al 2013;Jiang et al 2014;Li et al 2014). Magnetotelluric observations found that a finger-like crustal melt penetrates north from the Songpan-Ganzi terrane and weakens the crust beneath the Kunlun Shan (Pape et al 2012).…”