Mid-crustal low-velocity zones beneath Southeastern Coastal China revealed by multimodal ambient noise tomography: Insights into Mesozoic magmatic activities

Abstract

Southeastern Coastal China, located at the southeastern margin of the Eurasian continent, is an essential part of the South China Block. It is characterized by extensive Mesozoic magmatism and polymetallic mineralization. To explore the potential impact of Mesozoic magmatic events on the crust, we analyzed inter-station cross-correlation functions from 878 seismic stations. Utilizing the recently developed frequency-Bessel transform method, we extracted multimodal Rayleigh wave dispersion curves and constructed an updated 3D shear-wave velocity model. Our model reveals prominent and widespread mid-crustal low-velocity zones (MCLVZs) across the study area, likely attributable to the alpha-beta quartz phase transition. Additionally, a strong correlation is observed between MCLVZs characteristics and Jurassic-Cretaceous magmatic activities, with a southwest-to-northeast variation in MCLVZs continuity and intensity, reflecting the spatiotemporal migration of magmatism. These findings offer new constraints on the tectonic evolution of Southeastern Coastal China.