Plate-driven mantle dynamics and global patterns of mid-ocean ridge bathymetry

Global observations of mid-ocean ridge (MOR) bathymetry reveal a correlation between the difference in axial depth across ridge offsets and ridge migration. If upwelling and melt production rates are asymmetric across a ridge axis, three-dimensional (3-D) melt focusing and different crustal thickness across offsets may account for the observed differences in axial depth. In this article we use a 3-D numerical model to constrain the flow and thermal structure of a ridge-transform-ridge plate boundary. By coupling a model of melt focusing to our simulations we generate predictions of crustal thickness and axial depth change across offsets of different lengths. These predictions are consistent with the morphological changes observed along the global MOR system. In making these predictions we produce new constraints on the scale of melt focusing at mid-ocean ridges and on the extent of melt redistribution at the ridge axis. Results from our simulations also suggest that plate-induced mantle dynamics and melt focusing beneath a migrating MOR may produce global, systematic variations in the geochemistry of axial lavas.