Ongoing Asthenospheric Upwelling and Delamination‐Style Down‐Welling Beneath Northeast China: Evidence From High‐Resolution Magnetotelluric Profiles

Abstract

Northeast China was formed during the progressive closure of the Paleo‐Asian Ocean before the Early Mesozoic, and was then later affected by the westward subduction of the Paleo‐Pacific Plate and the west‐to‐east closure of the Mongolia‐Okhotsk Ocean. Huge volumes of granites were emplaced across this region during the Mesozoic, and widespread Cenozoic volcanism is still active in the Quaternary. To study past and present magmatic processes in this region, two parallel high‐resolution magnetotelluric profiles were collected to produce lithospheric resistivity models. Northwest of the Greater Xing'an Range, the lithosphere has a relatively low resistivity. The resistivity of the upper mantle low‐resistivity anomaly (C2) is consistent with the presence of a few percent of basaltic melt. This feature connects with a shallower low‐resistivity zone (C1) that extends into the crust. Its properties are consistent with 5–10% shoshonitic melt. The lithosphere in the southeast part is highly resistive. The upper mantle high‐resistivity zones (R1 and R2) are interpreted as regions of thickened lithosphere that may be undergoing delamination. The lower crust exhibits localized low‐resistivity zones (C3, C4, and C5), and they are interpreted as partial melt which may have originated in the ongoing upwelling. The overall pattern of magmatism appears to be driven by asthenosphere upwelling which might have been triggered by the Paleo‐Pacific Plate retreat, but the upper mantle low‐resistivity zone originates and rises from the northwest. Down‐welling in the southeast might be the combined effect of the subduction and retreat of the Paleo‐Pacific Plate and the instability of thickened lithosphere.

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

“…seismic velocity, temperature, density) in Northeast China (NE China) using 2D forward modelling. We find different structural features on the two sides of the NSGL, which reflect distinct Fan et al, 2021;Guo et al, 2016;Tang et al, 2014;Tao et al, 2014;Yang et al, 2022;Ye et al, 2022) and petrological and geochemical studies (e.g. Dong et al, 2019;Guo et al, 2019Guo et al, , 2020Ji et al, 2019;Xu et al, 2019) to investigate the deep structures in NE China, which have great significance for further understanding the tectonic evolution in NE China.…”

“…These high‐velocity anomalies beneath the SLB generally represent detached lithosphere fragments (Zhang et al, 2022), and the calculated S‐wave velocity distribution also reproduces the significant high velocity of ~4.55 km/s at depths of the detached lithosphere (Shen et al, 2016; Figure 5c). Moreover, extensive evidence involving petrological and geochemical analyses (Dong et al, 2019; Ji et al, 2019, 2020; Wu et al, 2003), electrical resistivity models (Tian et al, 2022; Ye et al, 2022), seismic anisotropy structures (Liu et al, 2016; Yang et al, 2022) and lithospheric thermal structure (Wang & Li, 2018) collectively supports that the SLB may have experienced lithospheric delamination. The widespread adakitic lavas and A‐type rhyolites in the SLB indicate that this delamination is associated with the rollback of the Palaeo‐Pacific slab (Ji et al, 2019, 2020).…”

“…It seems to suggest a potential link between lithospheric thinning to the east of the NSGL and Palaeo‐Pacific plate subduction. In addition, various dynamical mechanisms have been proposed to interpret the lithospheric thinning beneath the SLB, including pure lithospheric extension (Xu et al, 2000; Zhang et al, 2014), lithospheric delamination (Dong et al, 2019; Wu et al, 2003; Ye et al, 2022), mantle plume (He et al, 2014), and, however, there is still a lack of consensus.…”

“…In recent years, many researchers have conducted abundant geophysical (e.g. Fan et al, 2021; Guo et al, 2016; Tang et al, 2014; Tao et al, 2014; Yang et al, 2022; Ye et al, 2022) and petrological and geochemical studies (e.g. Dong et al, 2019; Guo et al, 2019, 2020; Ji et al, 2019; Xu et al, 2019) to investigate the deep structures in NE China, which have great significance for further understanding the tectonic evolution in NE China.…”

A Potential Mode of the Lithospheric Growth and Delamination of Orogenic Belts: Evidence From High‐Resolution Magnetotelluric Data

“…The Pacific plate subduction commenced in the Jurassic and retreated during the Cretaceous, creating an extension setting that triggered the asthenospheric materials convection and deep material upwelling (Zhu et al., 2017). The previous MT study characterized the electrical structure in the central and southern segments of the GXAR, and identified a conductive structure connected to the asthenosphere, as well as local conductors within the lithosphere of the orogenic belt (Ye et al., 2022). The conductive features, consistent with the molten fluid, were recognized as magma driven from the asthenosphere.…”