A Decapitated Inside-Corner High of the Discovery Fracture Zone Ridge-Transform Intersection, SW Indian Ridge

Abstract:

The northern inside-corner high of the Discovery FZ (Southwest Indian Ridge) consists of an oceanic core complex that advanced 15 km northward across the rift valley, forcing its volcanic axis to move out of alignment with the main rift axis to the east and presumably the underlying zone of mantle upwelling. This, in turn, appears to have shifted the main volcanic axis in the east to also shift northward, where it now lies close to the northern wall of the rift valley. Consequently, a deep, nascent 2.5-km wide volcanic rift developed 10 km to the south of the detachment fault termination, paved with pillow lavas, that has bisected the core complex into northern and southern portions. The southern wall of this new rift is in alignment with the southern wall of the main rift valley to the east, suggesting westward propagation of a neovolcanic zone located near the southern rift valley wall across the nose of the core complex. This was or is evidently fed by magmas intruded near the southern rift valley wall to the east driving rifting across the core complex. This sequence of events illustrates the complex interaction of forces associated with detachment faulting, the axis of mantle upwelling in the asthenosphere, and melt transport through the lithosphere.