Control of Sub-Crustal Mush Dynamics on 3D Stress Fields in Mid-Ocean Ridges: An FSI Modelling Approach

Abstract

Using a novel thermo-mechanical model, this study explores the role of multi-ordered 3D convective dynamics of the mushy region in modulating the strongly heterogeneous stress fields in mid-ocean ridge (MOR) systems. This model couples the sub-ridge mushy (fluid) regions with the elastic (solid) crustal layer within a mathematical framework of fluid–structure interaction (FSI) mechanics. Model-based calculations of the total stress tensor provide quantitative estimates of the across- and along-axis horizontal tension/compression (and σ^∥) and across-axis horizontal shear stress (σ^#) that dominantly control the ridge-axis morphologies. The stress analysis forms an alternative explanation for the off-axis ridge-parallel second-order hill topography, located at a distance of 20–50 km. This study also shows how along-axis compressional σ^∥ can localise a row of ridge-normal narrow, 10–30 km wide stripes on a wavelength of 40–150 km. Their overall patterns conform to the second-order magmatic segmentation structures of MORs. The σ^# mapping suggests that ridge-transverse discontinuities, including transform offsets, transpression and transtension zones, originate spontaneously from FSI interactions during MOR evolution. The article finally presents a set of MOR examples from modern plate tectonic settings to support model interpretations.

Keywords

abyssal hills / convective upwelling / fluid–structure interaction / magmatic segmentation / MOR stress fields / mush complexes

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2026 Geological Society of China.