On spreading modes and magma supply at slow and ultraslow mid-ocean ridges
Résumé
The ultraslow eastern Southwest Indian Ridge (SWIR) offers an opportunity to study the effect of magma supply on an ultraslow mid-ocean ridge starting from quasi-melt-free detachment-dominated spreading, and transitioning to volcanic spreading as one nears prominent axial volcanos. Detachments in the quasi-melt-free mode extend along-axis 60 to 95 km and have a lifetime of 0.6 to 1.5 myrs. They ultraslow ridges and propose that rheological changes induced by magma (melt itself is weak, hydrothermally altered gabbro-peridotite mixtures are weak, and melt heat sustains more vigourous hydrothermal circulation) also play a key role, resulting in contrasted potentials for strain localization, footwall flexure on faults and the development of detachment faults.
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