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Abstract

Inherited rheological structure of the lithosphere is expected to exert a significant influence on the architecture of continental rift systems. The eastern and western segments of the northern continental margin of the South China Sea (SCS) exhibit distinct differences in terms of thinning degree, structural style, and magmatic activity. In this paper, we combine 3D analog and 2D numerical models to investigate the influence of lithospheric heterogeneity caused by Mesozoic magmatism on the segmentation of this region. The analog and numerical modeling results, viewed from top and cross-sectional perspectives show that the northwestern margin, characterized by a Mesozoic magmatic arc, experienced greater deformation, resulting in a notably thinner crust compared to the northeastern margin hosting a forearc basin. This difference demonstrates that the local inherited lithospheric heterogeneities along the margin play a fundamental role in controlling the rift-related segmentation of the margin. Furthermore, our analog experiments successfully reproduce a scenario where a pre-existing NW-trending fault zone separates the northeastern and northwestern margins of the SCS, elucidating its role in the differential extension process of the region. This zone acted as a transfer fault zone, adjusting fault displacement and fault spacing in response to differential extension. Numerical simulations complement analog models incorporating variable lithospheric rheology between the northwestern and northeastern segments, providing, for the first time, three-dimensional dynamic insights into how pre-existing lithospheric heterogeneity controlled the temporal evolution and characteristic deformation of the northern SCS margin. These findings have major implications for structural styles and thinning processes in passive rift margins in the presence of crustal heterogeneity.