Initial burst of oceanic crust accretion in the Red Sea due to edge-driven mantle convection

Abstract

The 500 m.y. cycle whereby continents assemble in a single supercontinent and then fragment and disperse again involves the rupturing of a continent and the birth of a new ocean, with the formation of passive plate margins. This process is well displayed today in the Red Sea, where Arabia is separating from Africa. We carried out geophysical surveys and bottom rock sampling in the two Red Sea northernmost axial segments of initial oceanic crust accretion, Thetis and Nereus. Areal variations of crustal thickness, magnetic intensity, and degree of melting of the subaxial upwelling mantle reveal an initial burst of active oceanic crust generation and rapid seafl oor spreading below each cell, occurring as soon as the lid of continental lithosphere breaks. This initial pulse may be caused by edge-driven subrift mantle convection, triggered by a strong horizontal thermal gradient between the cold continental lithosphere and the hot ascending asthenosphere. The thermal gradient weakens as the oceanic rift widens; therefore the initial active pulse fades into steady, more passive crustal accretion, with slower spreading and along axis rift propagation

Architecture of rifted continental margins and break-up evolution: insights from the South Atlantic, North Atlantic and Red Sea–Gulf of Aden conjugate margins

“…The formation of oceanic crust in the Gulf of Aden and in the Red Sea has been studied by several earlier workers (e.g., Lowell & Genik 1972;Cochran 1981Cochran , 1982Cochran , 1983Cochran & Karner, 2007;Ligi et al 2011). Although at present there are no deep seismic reflection profiles extending across the conjugate margins and imaging the spreading center, several geophysical methods, including gravity, magnetic, sidescan sonar and academic seismic profiles, have provided important clues on the structures that are forming at the embryonic stage of sea-floor spreading.…”

“…In the central and southern Red Sea, the mid-ocean ridge is characterized in the median valley with an axial trough that may reach water depths of more than 2000m, and by a basaltic oceanic crust with magnetic anomalies indicating the breakup age and formation of new crust in the last few million years (Ligi et al 2011).…”

The development of extension and magmatism in the Red Sea rift of Afar

“…10). Melting may also be enhanced by stress-driven melt segregation (e.g., Holtzman and Kendall, 2010), and/or small-scale convection (Ligi et al, 2011) induced by steep gradients on the lithosphereasthenosphere boundary beneath the narrow rift.…”

KFUPM-KAUST Red Sea model: Digital viscoelastic depth model and synthetic seismic data set

“…Its width varies, reaching a maximum of 370 km in its middle and a minimum of 30 km in the Bab al-Mandeb Strait. It is a rift system that started 30 Ma ago and continues fragmenting the Arabian-Nubian Shield (Ligi et al, 2011) (Figure 2). It occupies a long northwest-trending basin between the African and Arabian shields and is characterized by steep walls in the axial trough and irregular seafloor topography (Coleman, 1974).…”

“…The Red Sea geology is important to study because it is considered an evolving young ocean, and studying it gives insight into the early stages of mature oceans (Ligi et al, 2011). Furthermore, it contains considerable mineral resources on its floor such as zinc, copper, silver, and gold (World Ocean Review, n.d.).…”