| Summary: | The Masirah Ophiolite (Sultanate of Oman) was part of an oceanic basin (Proto-Indian Ocean) formed by the break-up of Gondwana in Late Jurassic times similar to the Somali basin. It was obducted onto the Arabian continental margin in the Early Paleocene, 100 Ma after its formation. Hence, it is possible to investigate the different tectonic and magmatic processes that have affected the oceanic lithosphere during these 100 Ma. Tithonian ridge magmatism, tectonism and hydrothermal alteration are responsible for the formation of the oceanic crust of the Masirah Ophiolite. In the Early Cretaceous (Hauterivian-Barremian), after 20 Ma of normal drift and subsidence, the oceanic lithosphere underwent extensional tectonics and renewed magmatism. Geometry, kinematics, intrusion mechanisms and related sedimentation during this intra-oceanic rifting are widely described and illustrated by field observations. Exhumation of deep-seated oceanic lithosphere, alkaline volcanism, intrusion of a hornblende gabbro-dolerite-granite suite and uplift of crustal blocks to sea level with the unconformable deposition of platform carbonates are the processes characterising this intra-oceanic rifting. The Hauterivian-Barremian age of oceanic rifting coincides with an important reorganisation of the motion of the Indian plate relative to Africa, Antarctica and Australia. We interpret the rifting recorded in the Masirah Ophiolite as the local response to the motion of the Indian plate due to the opening of the South Atlantic and the spreading in the Eastern Indian Ocean.
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