Late Neoproterozoic adakitic magmatism of the eastern Arabian Nubian Shield

Abstract

Late Neoproterozoic adakitic magmatism within the Eastern Arabian Nubian Shield has been dated at 633.2 ± 9.0 Ma (2σ). These magmas intrude the forearc Ad Dawadimi Basin, which is composed of metapelitic schists and greywacke along with ophiolitic mélanges of boninitic affinity which underwent inversion and deformation by ∼620 Ma. This adakitic magmatism, while intruding parts of the Ad Dawadimi Basin, predates this deformation, but is possibly coincident with basin closure. As adakitic magmatism requires melting of an amphibolite or eclogitic source, empirical and experimental constraints require anomalously hot supra-subduction zone mantle. Considering that this magmatism immediately predates basin inversion, these magmas possibly pinpoint the timing of the slab breaking, marking the terminal stages of arc magmatism, terrane accretion and the influx of hot oceanic asthenospheric mantle. This influx of hot asthenospheric mantle may also be responsible for post-collisional A-type magmatism.