Geodynamic modeling on subduction-spreading interaction and implications for the South China Sea and surrounding regions

Abstract

The convergent subduction zones and the divergent spreading ridges are essential tectonic units that are widely distributed in the South China Sea and the surrounding regions, governing the regional tectonic evolution. Subduction-spreading interaction may be present between these two tectonic units, especially when they are located adjacent. Quantitative study of subduction-spreading interaction remains insufficient. Using 2D thermomechanical numeric modeling, we systematically study subduction-spreading interaction with particular attention paid on the influence of lower plate spreading versus upper plate spreading on subduction development. Our modeling results provide the following findings. (1) Intensive interaction is present between the adjacently located spreading center and subduction zone through plate motion and mantle convection, and positive feedback is present between these two units, i.e., spreading promotes subduction and vise verse. (2) The location of spreading center either on the upper or lower plate facilitates the formation of passive and active subduction, respectively, and the offset distance between the two units affects the intensity of subduction-spreading interaction. (3) Subduction-spreading interaction may be widely present in the South China Sea and the surrounding regions, where multiple subduction zones and spreading centers distribute adjacently in the present and evolved episodically in the past.

Keywords

• Subduction
• Spreading
• Tectonic interaction
• Geodynamical modeling
• South China Sea
• Southeast Asia