Channelised magma ascent and lithospheric zonation beneath the Songliao Basin, Northeast China, based on surface-wave tomography

Abstract

The Songliao Basin in Northeast China is located within the eastern part of the Central Asian Orogenic Belt and to the north of the accretionary belt of the North China Craton. The lithosphere beneath the basin and the surrounding region has undergone a series of complex deformation processes due to sequential interactions among different tectonic plates since the Palaeozoic. Here we construct a three-dimensional lithospheric shear-wave (S-wave) velocity model for the region via surface-wave tomography to better understand the deep dynamic processes that shaped the Songliao Basin. The S-wave velocity model highlights strong linkages between the surface geology and mantle lithospheric structures. The Baicheng–Changchun uplift (or Song-Liao watershed), which divides the basin into two river systems, is underlain by a dome-like area of uplifted crust. The central Songliao basin is underlain by a weak, thin lithosphere that is ∼80 km thick, whereas the eastern Great Xinggan Range to the northwest is underlain by a normal crust and lithosphere that is ∼100 km thick. The northern North China Craton and southern Songliao Basin are also underlain by normal crust and a lithosphere that is up to ∼150 km thick, with a low-velocity zone penetrating the high-velocity mantle lithosphere at ∼80–100 km depth. Such structural features imply that the far-field effect of Pacific Plate subduction since the Cenozoic varies across Northeast China and is dependent on the lithospheric structures that existed prior to subduction.