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

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.