Lithospheric structure in the Cathaysia block (South China) and its implication for the Late Mesozoic magmatism

Abstract

Mesozoic granitoids are widely distributed in South China, but the mechanism for generating the felsic magmas is still in debate. To understand the possible origin of the granitoids, we use joint inversion methods and forward modelling of receiver functions to reveal the lithospheric structure in the Cathaysia block. The joint inversion of receiver functions and surface wave dispersion with P-velocity constraints is applied to a dense array in the Cathaysia block, and the specific crustal Vp/Vs ratios obtained from a generalized H-κ stacking method are introduced to the traditional joint inversion for passive seismic stations. The detailed structures provide valuable knowledge of the geological processes: 1) The present-day lithosphere is 60–70 km thick, which has been thinned since the Late Mesozoic with reference to geochemical data; 2) there is a lack of high Vp and Vs in the lower crust in this region. The results may have limited resolution on the localized magmatic underplating, but they do not support the extensive magmatic underplating at the Late Mesozoic. Other factors could be the mechanism for the granitoid formation in this region.