A fine crustal structure and geodynamics revealed by receiver functions along the Guangchang-Putian line in the Cathaysia Block, South China

Abstract

The Cathaysia Block is located in South China, along the western margin of the Pacific plate, and well known for its widespread granitoids and rich poly-metallic mineralization. Despite the numerous studies conducted in this region, some key questions are still in debate, which revolve around the detailed crustal architecture, the boundary between the western and eastern part of Cathaysia Block, and the geodynamic evolution and metallogenic settings in the Cathaysia Block. In this study, we have conducted a dense broad-band seismic observation in the Cathaysia Block, and obtained the fine crustal structure of it by using P-wave receiver functions and analyzing other geophysical and geological studies comprehensively. Our study has following findings: (1) the crust of the Cathaysia Block is ~31.5 km thick, thinner than that of the global continent, and is interpreted to have been thinned since the Late Mesozoic; (2) the Vp/Vs ratio of the Cathaysia Block is lower than that of the global continent, which implies there is no extensive underplating beneath the Cathaysia Block, or that the magma may be confined at bottom of the crust and formed a velocity gradient belt around Moho; (3) Zhenghe-Dapu fault is marked as the structural boundary between the western and eastern Cathaysia Block; (4) the western and eastern Cathaysia Block have different intra-crustal structures, petrochronology features and mineralization settings; (5) the subduction of the paleo-Pacific plate and the following roll-back could be responsible for the geodynamic evolution of the crustal deformation, as well as the widespread magmatism and mineralization.