Mantle Zone beneath the North China and Some Implication for the Origin of the Datong Volcano

Abstract:

We analyzed a total of 97727 receiver-function data recorded by 590 stations in North China from 711 teleseismic events. We used a common-conversion-point stacking (CCP) method to generate a 3D reflectivity volume in the area between 108°-125°E and 36°-43°N, in the depth range of 200 to 800 km. We found significant topography on both the 410-km and 660-km discontinuities. It is well known that estimating the depths of the two discontinuities from Ps conversion times are very sensitive to the reference P- and S-wave velocity models. We used the EARA2014 model, which was derived from a waveform adjoint tomography study of East Asia (Chen et al., 2015) and had comparable resolutions for both P- and S-wave velocity, as the 3D reference model in computing the Ps moveouts for the CCP stacking. We found that the 660-km discontinuity is depressed up to 25 km along the east coast of China, indicating the presence of the subducted Pacific slab in the region. We found a strong and localized anomaly beneath the Quaternary Datong volcano located at the northeastern edge of the Ordos plateau in north China. The 410-km and the 660-km discontinuities are, respectively, depressed and uplifted by a few kilometers beneath the volcano, resulting in a transition zone approximately 15 km thinner than the global average. This observation suggests a deep origin of the Datong volcano, although it was usually attributed to edge driven convection by most of the literatures.