Distinct Lithospheric Structure in the Xing'an‐Mongolian Orogenic Belt

Abstract

Detailed knowledge of the lithospheric structure is essential for a better understanding of the tectonic evolution of the Xing'an‐Mongolian Orogenic Belt (XMOB). We constrained the lithospheric structure across the XMOB by receiver function imaging and shear wave splitting analysis from a dense seismic array. The lithosphere‐asthenosphere boundary (LAB) is coherently imaged in different tectonic blocks. The mid‐lithospheric discontinuity is also identified at ∼75–100 km depth over the deeper LAB (∼110–130 km) beneath the western side of the North‐South Gravity Lineament (NSGL), roughly at the same depth as the LAB beneath the eastern side of the NSGL. The distinct variations in both the lithospheric structure and fast shear‐wave polarization direction across the NSGL are likely caused by different tectonic processes in the two sides, indicating that the NSGL might represent the western boundary influenced by the subduction of the (Paleo‐)Pacific Plate. Lithosphere thinning in the XMOB is evidenced to have been limited mainly to the east of the NSGL.

Subduction‐Induced Asthenospheric Flow Around the Songliao Basin in NE China Revealed by Shear Wave Splitting Measurements of Dense Seismic Arrays

“…Beneath the southern Songliao Basin, the procedure indicates that a depth of 230 km generates the majority of the anisotropy. A recent S wave receiver function study from an ∼2,000 km E‐W profile NECSaids has detected the lithosphere‐asthenosphere boundary (LAB) west of the North‐South Gravity Linement (NSGL) at ∼110–130 km, and the LAB east of the NSGL at ∼75–100 km (He et al., 2022), generally consistent with Meng et al. (2021) and Chen et al.…”

“…The absence of mantle‐sourced magmatism and the low topography of the Songliao Basin indicate that the foundering process is still at an early age. This is supported by the migrated S‐RF profile which shows that the LAB beneath the Songliao Basin is not smooth and that several negative signals appear under the LAB (Figure 2b in He et al., 2022), suggesting that the majority of the foundering lithospheric material adheres to the lowermost lithosphere (Figure 8). After the Japan Sea opening ceased (16 Ma ∼ present), the Songliao Basin experienced intense volcanic eruptions on both sides (Liu et al., 2001).…”

“…Beneath the southern Songliao Basin, the procedure indicates that a depth of 230 km generates the majority of the anisotropy. A recent S wave receiver function study from an ∼2,000 km E-W profile NECSaids has detected the lithosphere-asthenosphere boundary (LAB) west of the North-South Gravity Linement (NSGL) at ∼110-130 km, and the LAB east of the NSGL at ∼75-100 km (He et al, 2022), generally consistent with Meng et al (2021) and Chen et al (2008). Another SRF analysis from a 1,200 km-long profile north of the study region (Zhang et al, 2014) detected the LAB at a shallower depth of around 120 km beneath the northern Songliao and at ∼160 km on both east and west sides of the basin.…”

Geophysical‐petrological modelling of the crust and upper mantle structure across the North‐South Gravity Lineament in NE China: Insights into the lithospheric thinning mechanism

“…The thickness of the detached body is 40 km, consistent with the lithospheric thinning beneath the SLB (He et al, 2022). The composition is characterized by the average composition of lithospheric and sublithospheric mantle beneath the SLB, due to the effect of surrounding mantle metasomatism.…”

Coupling Between Exhumation and Subduction: A Case Study From the Southern Great Xing'an Range, NE Asia

“…75–100 km) compared to west of this lineament (ca. 100–130 km) (He et al., 2022; Tang Z. et al., 2022; Zhang et al., 2014). Combined with the Jurassic compressional deformation (Y. Q. Zhang et al., 2022) and Phanerozoic lithospheric mantle xenoliths (Guo et al., 2017; Pan et al., 2015; Wu et al., 2003), these observations imply that the bottom of the lithosphere in NE China, which was thickened due to flat subduction during the Jurassic, underwent delamination due to roll‐back during the Cretaceous.…”