3D Crustal and Upper Mantle Model of East‐Central China From a Joint Inversion of Surface and Body Waves and Its Tectonic Implications

Abstract

AbstractAs the junction of two important tectonic units, North China Craton and South China Block, East‐Central China has undergone multi‐period tectonic events, including the Triassic continental collision and the Mesozoic and Cenozoic subduction of the western Pacific plate, which forms unique crustal and upper mantle structures in East‐Central China. In this study, by jointly inverting body and surface waves, we construct a high‐resolution 3D Vs model of East‐Central China at the depths of 0–800 km. Our results show that along the eastern Qinling‐Dabie orogen formed by past continental collision, there are significant changes in velocity patterns in the upper mantle. From the eastern Dabie to the western Dabie, velocity features mainly vary from low velocities to high velocities, implying a westward weakening of the influence of the Paleo‐Pacific tectonic domain. The high‐velocity anomaly is partially missing beneath eastern Qinling, which may be attributed to the lower crustal and lithospheric mantle delamination. In addition, we find a significant low‐velocity anomaly in the upper mantle beneath the Lower Yangtze Craton, which may represent an upwelling of thermal fluids caused by the dehydration of stagnant slabs in the mantle transition zone. This low‐velocity anomaly extends upward into the shallow lithosphere and is consistent with the area of crustal and lithospheric thinning as well as the concentrated exposure of Cenozoic continental basalts. These connections reveal the reactivation of the lithospheric mantle by the dehydration of the stagnant slab and the asthenosphere upwelling during the Cenozoic.