Synchronous Seafloor Spreading and Subduction at the Paleo-Convergent Margin of Semail and Arabia

Abstract

The Semail ophiolite is the largest and best-exposed ophiolite, having preserved intact record of a precollision system related to Neotethyan Ocean closure. Breaking with the alternative models of ophiolite exhumation and emplacement, this paper builds on integrating the joined contribution of tectonic evolution of the continental margin in the premise of the ophiolite obduction. Connecting the along-strike segmentation of the ophiolite recorded in the lithospheric flow structure, and recent high-precision dating, results in a 3-D model of evolution of the ophiolite and its continental margin during Jurassic-Cretaceous time. Among the relevant characteristics newly accounted, (1) the contamination of the ophiolite by fluids and magmas of continental origin; (2) the discrimination of different types of metamorphics associated to the ophiolite, and conventionally classified metamorphic soles; (3) the instability of the Arabian margin during the Late Jurassic-Cretaceous times; (4) the new precise ages relating to overlapping of spreading and detachment; and (5) the inferred vergence of Neotethyan closure during late Mesozoic are stressed. The complex stem revealed may relate to processes associated with spreading center subduction at ridge-trench-transform (RTT) triple junction, as documented along a convergent margin. The Semail ophiolite emplacement on the Arabia continental margin would result from a temporary Arabian platform-directed subduction zone that consumed the southern Tethyan plate during Late Jurassic-Cretaceous time.