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

Abstract

The North‐South Gravity Lineament (NSGL), characterized by an abrupt variation in both the Bouguer gravity anomaly and topography, acts as a significant geological boundary in eastern China. The formation of such a lateral feature is believed to be associated with lithospheric thinning. The Songliao Basin (SLB) is considered to mark the centre of the lithospheric thinning in Northeast China, whereas its thinning mechanism remains unclear. Here we perform integrated geophysical‐petrological modelling of the crust and upper mantle structure along a passive‐source seismic profile crossing the NSGL, to understand the thinning mechanism beneath the SLB based on the constructed lithospheric extension and delamination models. Our delamination model identifies the compositional variation across the NSGL and the S‐wave velocity signature dominated by high velocity beneath the SLB, which are compatible with previous geochemical and geophysical results. The multidisciplinary analyses suggest that the lithospheric delamination is a plausible mechanism to account for the thinning to the east of the NSGL. The resulting model also shows that the NSGL is a lithospheric‐scale geophysical and geochemical boundary separating two distinct structural domains. In combination with previous evidence, structural discrepancies across the NSGL can be attributed to the lithospheric delamination driven by the subduction of the Palaeo‐Pacific plate.