Melt-induced weakening controls topography and faulting pattern of mid-ocean ridges

In the current theories of mid-ocean ridges, diking processes have been considered by using simplified models with a single permanently open central dike. Here, I instead consider long-term large-scale rheological effects of multiple dikes emplacement, which lead to rheological weakening of the forming mid-ocean ridge lithosphere. Based on 2D numerical experiments modeling multiple dikes emplacement, I derive rheological expressions representing effective strength of the melt-weakened lithosphere as the function of local melt flux. These expressions are then implemented into 3D visco-elasto-plastic mid-ocean ridge models including mantle decompression melting, crustal growth and melt flux-induced weakening of the spontaneously accreting oceanic lithosphere. Based on 3D numerical experiments, I demonstrate that the newly developed rheological theory explains well the observed mid-ocean ridge topography and faulting pattern variations with spreading rate and oceanic crust thickness. This theory may be further used for other geodynamical situations involving melt transport through oceanic and continental lithosphere such as continental and oceanic rifting, continental breakup and plume-lithosphere interaction processes.