Formation mechanism of the North–South Gravity Lineament in eastern China

Abstract

Gravity lineaments are well recognized along plate boundaries and in the interiors of oceanic plates. However, the formation mechanism of intracontinental gravity lineaments remains poorly understood. The North–South Gravity Lineament (NSGL), which extends >4000 km from Russia to South China, is characterized by an abrupt change in the observed Bouguer gravity anomaly, ranging from −100 mGal in the west to −40 mGal in the east over a distance of <100 km. Here we employ gravity modeling along a deep seismic sounding profile that transects the NSGL to delineate the relative contributions of the thickness and composition of the crustal and upper mantle and the stagnant slab in the mantle transition zone to the observed gravity anomaly, and to ultimately constrain the formation mechanism of the NSGL. Our results indicate that crustal thickness is the dominant factor in the formation of the NSGL, with lithospheric composition also playing a role. Combining our results with those of previous studies, lateral variations in the lithospheric mantle composition and crustal/lithospheric thickness across the NSGL can be attributed to lithospheric thinning and mantle replacement in the eastern part of the North China Craton during the late Mesozoic. This was triggered by the subduction of the Paleo-Pacific plate and subsequently led to the persistence of a stagnant slab and big mantle wedge. This study highlights the fundamental need for integrated geophysical–petrological analyses to better understand the surface response to deep tectonic processes.