Abstract
A high‐resolution 3D crustal and upper‐mantle shear‐wave velocity model of Northeast China is established by joint inversion of receiver functions and fundamental‐mode Rayleigh wave phase velocities. The teleseismic data used to calculate receiver functions are collected from 107 CEA permanent sites and 118 NECESSArray portable stations. Rayleigh wave dispersion measurements are extracted from an independent tomographic study. Our model exhibits significant detail in S wave velocity structure. Particularly, we observe a nearly constant S wave velocity of 3.4–3.6 km/s from shallow to deep crystalline crust under the study area, which we attribute to a high thermal gradient. Some modestly positive S wave velocity anomalies in the crust beneath the Songliao basin are interpreted as solidified late‐Mesozoic mafic intrusions. In the upper mantle, we confirm the local presence of low‐velocity zones below the Changbai mountains and Lesser Xing'an mountain range, consistent with asthenospheric mantle upwelling models. Furthermore, moderately low shear velocities imaged beneath the Halaha and Abaga volcanoes indicate possible pathways of magma ascent through the lithospheric mantle from the asthenosphere. At a regional scale, the average lithosphere‐asthenosphere boundary depth increases from ∼70 km under the greater Changbai mountains to ∼100 km below the Songliao basin, and reaches ∼110–120 km beneath the Greater Xing'an mountain range in the west. The conjectured dense mantle lid under the Songliao basin, characterized by fast S velocities, may have prevented sublithospheric melts from migrating to the surface.
Plain Language Summary
Northeast China is a unique region with a combination of ancient Precambrian geology, active seismicity, and volcanism. The presence of widely distributed volcanoes in this region is enigmatic and their origin has been widely debated. We use available seismic data to create a high‐resolution 3D shear‐wave velocity model for the crust and upper mantle of Northeast China. Our model reveals significant multiscale seismic velocity anomalies in the crust, mantle lithosphere and asthenosphere that we associate with the volcanic/magmatic processes. The lithospheric thickness gradually increases from ∼70 km beneath the Changbai mountains to ∼120 km some 1,000 km to the west. Our results provide novel constraints on the crustal and upper‐mantle structure of Northeast China and help to interpret the mechanism behind active volcanism and the geodynamic setting.
Key Points
A nearly constant velocity in the crust may be due to a high thermal gradient and local high crustal velocities may denote mafic intrusions
Low S velocities are imaged in the upper mantle below the largest active volcanoes and locally the lithospheric mantle is thinned or absent
The lithosphere is ∼70 km thick below the greater Changbai mountains and thickens to ∼120 km under the Great Xing'an mountains in the west