Seismic imaging of crustal reworking and lithospheric modification in eastern China

Abstract

We processed teleseismic waveforms from a temporal 36-station seismic array to determine the crustal and lithospheric structure of the eastern South China Block. The NCISP-8 seismic profile spans a 480 km transect across the northeastern South China Block as well as the convergent boundary between the North China Craton and the South China Block. Common conversion point (CCP) stacking was used to image velocity discontinuities in the lithosphere along the profile. Synthetic test of CCP imaging along with forward modelling and inversion analysis of receiver function waveforms were used to identify attributes of the discontinuities obtained from CCP imaging and construct velocity models for each station. The crustal structures identified include a horizontally widespread low-velocity zone in the lower crust as well as local vertically diffuse crust–mantle boundary. These features indicate the effect of significant crustal reworking. We interpret the observed crustal fabrics as the effect of magmatism occurring since the Late Mesozoic. The thin lithosphere (57–86 km) and the heterogeneous lithospheric mantle structure provide compelling evidence of lithospheric modification in the eastern South China Block. Similarities between the lithospheric structures of the eastern South China Block and eastern North China Craton confirm that subducting ocean plate–continental lithosphere interaction controlled continental lithospheric modification in eastern China.