The styles and products of interactions between faulting and magmatism are highly variable among mid-ocean ridge systems. Given much thicker axial lithosphere at ultra-slow spreading ridges than at faster-spreading ones, it is an open question how corrugated surfaces at ultraslow spreading ridges are initiated, terminated and replaced by other faulting modes. Cannat et. al. (2009) proposed an enhanced footwall weakening mechanism associated with the formation of weak shear zones coated with hydrous minerals. We tested if the proposed weakening mechanism would be necessary for the formation of corrugated surfaces. Preliminary results from our numerical models suggested that serpentinization is still the most important for the formation of corrugated surface; the talc coating helps a detachment fault survive longer but is not sufficient for initiating it. We also investigated the effects of non-uniform magma distribution through the brittle lithosphere at ultra-slow spreading ridges. Because of the scarcity of magma forming at ultra-slow spreading ridges, magma is likely to go mostly up to the shallow portion of brittle lithosphere, leaving the lower portion magma starved (Cannat et al., 2019). Our numerical models parametrizing such a magma distribution showed that magma focused on the shallow part of the brittle axial lithosphere promotes the formation of long-lived detachment faults and corrugated surfaces by increasing differential stress on and enhancing rotation of the fault planes.
Fully three-dimensional numerical models for along-axis variations in magmatic and tectonic processes at slow-spreading mid-ocean ridges
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