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Oceanic detachment faults play a central role in accommodating the plate divergence at slow-ultraslow spreading mid-ocean ridges. Successive flip-flop detachment faults in a nearly-amagmatic region of the ultraslow spreading Southwest Indian Ridge (SWIR) at 64°30’E accommodate ~100% of plate divergence, with mostly ultramafic smooth seafloor.

Melt supply at the ultraslow-spreading Southwest Indian Ridge (SWIR) has been shown to vary from nearly-amagmatic, leading to ultramafic seafloor, to magmatically-robust, producing fully volcanic seafloor. The center of the SWIR 50°28’E segment represents a magmatically-robust endmember.