Neotectonic activity on continental fragments in the Southwest Indian Ocean: Agulhas Plateau and Mozambique Ridge

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Abstract
The Agulhas Plateau and Mozambique Ridge are composed in part of continental fragments embedded within oceanic crust of the southwest Indian Ocean. Recent studies of the plateaus and their vicinity have discovered significant evidence for neotectonic activity. In both areas, newly obtained seismic reflection profiles indicate possibly young basaltic intrusions in the northern, oceanic parts of the plateaus. Small rock fragments recovered from the southern Mozambique Ridge comprise metamorphic and volcanic lithologies. The volcanic rocks are made of extremely fresh quenched glasses. Although no radiometric dates are available for the volcanic glasses, their lack of any significant alteration suggests that eruption took place in the last few tens of thousands of years, supporting the seismic reflection evidence for magmatic activity in this region. The active crustal stretching and tensional stresses implied by this relatively recent tectonism probably cannot be generated by distantly applied plate‐driving torques, such as ridge push, but appear to require buoyancy‐related forces originating in the underlying upper mantle.