Crustal Deformations of the Central North China Craton Constrained by Radial Anisotropy

Abstract

Situated in a transition zone between the western and eastern North China Craton (NCC), the central NCC exhibits complex dynamics features. Significant lithosphere thinning is observed beneath the eastern NCC and the northern segment of the central NCC. To study how the crust responses to the distinct lateral variations of the lithospheric mantle, we develop a method for joint inversion of Rayleigh and Love dispersion curves based on a transverse‐isotropic (or radial anisotropy) medium and obtain a 3‐D crustal radial anisotropy model. The results reveal significant heterogeneities along the Cenozoic Fenhe‐Weihe Rift (FWR). In the northern FWR, the discretely distributed lower crust positive anisotropy and upper crust negative anisotropy suggest the rifting is mainly dominated by the active mantle upwelling resulting in the Datong volcanoes. Similarly, the northern segment of the Taihang Mountain is also strongly affected by the magmatic activities and exhibits different anisotropy properties compared to its central‐to‐southern counterpart. Based on the negative anisotropy observed in the middle‐to‐lower crust beneath most parts of the Taihang Mountain, we speculate that a lower‐crust compression model can be applied to the Taihang Mountain, which is totally different to that of the adjacent Bohai Bay Basin. Possibly, the root of the Taihang Mountain is pushed by the westward moving lower crust coupled with the lateral escaping mantle flow beneath the Bohai Bay Basin. The Taihang Mountain and the Bohai Bay Basin are formed in similar tectonic environments, but are deformed in different ways.

Anisotropic Tomography and Dynamics of the Big Mantle Wedge

“…Beneath the eastern North China craton, negative RANs are revealed in the asthenosphere (J. Wang et al, 2014), which are consistent with our model beneath the North China basin, although some models show positive RANs in the crust (Ai et al, 2020;Cheng et al, 2013;Fu et al, 2015).…”

“…Previous seismic studies focused on the azimuthal anisotropy (AAN) structure of variable scales in East Asia (H. Chen et al., 2017; X. Fan et al., 2020; Z. Huang et al., 2014; Lü et al., 2019; J. Ma et al., 2019; Tian & Zhao, 2013; Wei et al., 2015; Jia et al., 2022) and radial anisotropy structure beneath the North China craton (Ai et al., 2020; Cheng et al., 2013; Fu et al., 2015; J. Wang et al., 2014). However, there has been no study of 3‐D P ‐wave radial anisotropy of the BMW in East Asia, especially in its asthenosphere.…”

Lithospheric Conductors Shed Light on the Non‐Uniform Destruction of North China Craton

“…The conductive direction of anisotropy is perpendicular to the profile, consistent with the strike of the stripes in 3‐D isotropic inversion (Figure 5c). The positive seismic radial anisotropy in the lower crust (∼10%) beneath SNCP (Ai et al., 2020) provides an important clue for the presence of the horizontally oriented sills rather than dykes that will produce negative anisotropies (C. Jiang et al., 2018). If the sills contain electrically conductive phases and elongate along a preferred orientation, electrical anisotropy occurs and its most conductive direction represents the orientation of the sills (S. Liu et al., 2021).…”

“…Although it is difficult to distinguish the two conductive phases by MT and seismic methods in tectonic active regimes, saline fluids are more prevalent in the middle crust (Wanamaker, 2005). We thus prefer the hypothesis of partial melt, which is often used to explain crustal anisotropy beneath Cenozoic volcanos (Ai et al., 2020; C. Jiang et al., 2018).…”

Radial Anisotropy and Sediment Thickness of West and Central Antarctica Estimated From Rayleigh and Love Wave Velocities

“…In our imaging, the EM shows 5 ± 2% positive anisotropy throughout the crust, but the adjacent Whitmore Mountains (WM) only show strong positive radial anisotropy in the upper crust, and the middle to lower crust does not have a clear anisotropic pattern. Strong positive radial anisotropy in the middle to lower crust is broadly observed in other regions that have undergone extensional deformation, such as the North American Basin and Range, California, Tibet, Central North China, and Madagascar (Ai et al, 2020;Dreiling et al, 2018;Moschetti et al, 2010b;Wilgus et al, 2020;Xie et al, 2013). Positive crustal anisotropy is usually ascribed to highly anisotropic mica or amphibole minerals with a preferential orientation from horizontal compression or extension (Brownlee et al, 2017;Erdman et al, 2013;Lloyd et al, 2009).…”