Characteristics and evolution of post-rift magmatism in the Zhongjiannan Basin, western South China Sea

The spatio-temporal evolution of magmatism provides critical insights into the influence of regional tectonic events on the continental margin. Post-rift magmatism is widespread along the South China Sea margin， with volcanoes and magma intrusions on the northern margin being well-investigated. However， the distributions， timing， and evolutionary characteristics of post-rift magmatism along the western margin， particularly in the Zhongjiannan Basin， remain poorly constrained. This inhibits the comprehensive understanding of the post-rift evolution along the South China Sea margin. In this study， high-resolution 2D seismic data in the Zhongjiannan Basin are used to investigate the morphology and spatial distribution of volcanoes and magma intrusions. Post-rift magmatism in the Zhongjiannan Basin can be divided into three stages (Stage1-3). Stage 1 (Early-Middle Miocene) was featured by eruptions of a large volcano (the Guyue Seamount)， and small-scale volcanoes in the Central Depression and Northern Uplift， accompanied by magma emplacement. Stage 2 (Late Miocene) exhibited scattered， small-scale volcanic activities. Stage 3 (since Pliocene) was characterized by widespread magma intrusions in the Central Depression， and volcanism concentrated in the eastern part of the basin. The eastward intensification of magmatism during Stage 3 may be related to mantle readjustment triggered by the strike-slip reversal of the Red River Strike Zone. This study provides new constrains on the spatio-temporal evolution of post-rift magmatism along the South China Sea margin， and can also help understand the intense Late Cenozoic magmatism among the Southeast Asia.