Lateral Seismic Anisotropy Variations Record Interaction Between Tibetan Mantle Flow and Plume‐Strengthened Yangtze Craton

Abstract

The southeastern Tibetan Plateau experienced intense Cenozoic shortening and extrusion along the western Yangtze Craton, SW China, where the Permian Emeishan flood basalts were emplaced. Seismic anisotropy along a dense E–W‐trending linear seismic array across the west Yunnan is determined by shear‐wave splitting analysis to characterize the deformation associated with these processes. Interestingly, a strong N–S‐oriented anisotropic zone collocated with the Eocene–Oligocene potassic magmatism is observed between two weak anisotropic zones in the Three‐River Orogenic Zone and the western Yangtze Craton, respectively. The lateral anisotropy variation and distinct upper mantle structures collectively suggest that the western most Yangtze Craton, strengthened by the Permian mantle plume, acted as a rigid barrier to divert the Cenozoic Tibetan mantle flow into the Three‐River Orogenic Zone. Consequently, the western edge of the Yangtze Craton has been partially eroded and its anisotropic orientation was realigned to the direction of the mantle flow. This observation indicates that both the remodeled anisotropy in the lithosphere and the dynamic flow in the asthenosphere contribute to the mantle anisotropy at the lateral lithosphere‐asthenosphere transition, which is usually hard to seismologically resolve from the vertical lithosphere‐asthenosphere boundary.

Crustal SiO2 Content of the Emeishan Large Igneous Province and its Implications for Magma Volume and Plumbing System

“…The mafic crust composition of the INZ coincides with a region of high seismic wave velocity (Guo et al., 2017; T. Xu et al., 2015; Zhang et al., 2020), high density (Y. F. Deng et al., 2014), and high resistivity (X. Li et al., 2020). It is also consistent with the previous speculation that the INZ of the Emeishan LIP was significantly modified by the strong vertical deformation accompanied with magmatic emplacement (Chen et al., 2015; W. Li et al., 2021; Y.‐G. Xu & He, 2007).…”

“…Li et al, 2020). It is also consistent with the previous speculation that the INZ of the Emeishan LIP was significantly modified by the strong vertical deformation accompanied with magmatic emplacement (Chen et al, 2015;W. Li et al, 2021;.…”

Panoptic View of Mantle Flow Beneath Trans‐Continental Northeast Asia: Distinct Variation Detected From ∼2,000 km Shear Wave Splitting Profile

“…There is an apparent low wave velocity anomaly in the crust and upper mantle below the CBM (Figure 3a). We argue that the upwelling of hot material from the deep mantle resulted in the change of the horizontal flow direction of the asthenosphere (Figure 4b) and thus induced the vertical seismic anisotropy that is undetectable for the steeply propagating SKS waves and would be ultimately featured as weak or nonsplittings (Li et al., 2021). Anisotropy investigation using over 20 years of seismic records showed that in this subduction region, a kind of convection flow associated with the BMW as deep as the MTZ might also contribute to the observed seismic anisotropy (Bi et al., 2020; G. R. Guo et al., 2021).…”

A Generalized Strategy From S‐Wave Receiver Functions Reveals Distinct Lateral Variations of Lithospheric Thickness in Southeastern Tibet

“…Previous studies have employed receiver function, ambient noise tomography, and body‐wave and surface‐wave tomography methods to clarify both the Moho discontinuities and LAB near our study region (Wang et al., 2021; Wei et al., 2022; Zhou et al., 2012), with each of these studies suggesting a thin crust and thin lithosphere beneath Tengchong Volcano. A thick (150–180 km) lithosphere that underlies a crustal lid (35–50 km) has also been observed beneath the Sichuan Basin (Wang et al., 2018; Zhang et al., 2010, 2018), with the thick lithosphere beneath the basin being a typical characteristic of this ancient craton (Li et al., 2021; Wang et al., 2022).…”

“…Permian Emeishan flood basalts have been emplaced beneath the Chuandian region, with the lack of a detectable LAB aligning directly beneath the inner zones of the Permian Emeishan Large Igneous Province. The mantle plume model is a popular approach for explaining the geophysical and geochemical observations (Chen et al., 2015; Deng et al., 2016; Li et al., 2021; Xu et al., 2007) in large igneous provinces. The plume head could undergo strong changes and erode the overlying lithosphere owing to high temperatures and push it upward, with this being a common type of lithospheric thinning caused by a rising plume (Burov et al., 2007; Hawkesworth et al., 2017); this phenomenon is known as plume‐induced lithospheric destruction.…”