Late Cryogenian-Ediacaran history of the Arabian-Nubian Shield: A review of depositional, plutonic, structural, and tectonic events in the closing stages of the northern East African Orogen

Origin and evolution of post-collisional magmatism: Coeval Neoproterozoic calc-alkaline and alkaline suites of the Sinai Peninsula

Ion-probe U–Pb dating of plutonic rocks from the northern Arabian–Nubian Shield in Sinai and southern Israel constrains the timing of late East African batholithic post-collisional calc-alkaline (CA2) magmatism and within-plate alkaline to peralkaline (AL) magmatism to c . 635–590 Ma and c . 608–580 Ma, respectively. The earliest dated CA2 rocks are slightly deformed to undeformed, indicating that penetrative deformation ceased by c . 630 Ma. Within the CA2 suite a change from mafic to felsic magmatism is manifested in most of the region, peaking in a voluminous pulse of granodiorite to granite intrusion at 610–600 Ma. The AL magmatism started contemporaneously with the peak in CA2 felsic activity at c . 608 Ma and lasted until 580 Ma. It includes mostly alkaline and peralkaline granites, probably representing variable degrees of differentiation of similar parental magmas. Thus CA2 and AL granites do not represent different tectonic settings, but coeval derivation from variable sources during crustal extension. The majority of rocks dated in this study show minor to non-existent zircon inheritance and thus indicate very minor interaction with previously formed felsic crust. The rare zircon xenocrysts span a typical East African age range (900–607 Ma) and confirm the absence of older crustal components in the juvenile Arabian–Nubian Shield. Supplementary material: Geochemical and geochronological methods, sample descriptions and data are available at http://www.geolsoc.org.uk/SUP18327.

Post-collisional tectonomagmatic evolution in the northern Arabian–Nubian Shield: time constraints from ion-probe U–Pb dating of zircon

Crustal evolution and recycling in the northern Arabian-Nubian Shield: New perspectives from zircon Lu-Hf and U-Pb systematics

Review of the Late Neoproterozoic history of the northern Arabian–Nubian Shield (ANS) reveals that rapid and extensive erosional denudation, widespread late-orogenic calc–alkaline and alkaline igneous activity and intramontane basin formation affected this terrane at 630–590 Ma. Core-complex extension is also recorded at this time interval. To account for this coupling it is suggested that the mantle lithosphere was removed/delaminated from below the northern ANS subsequent to significant crust–mantle thickening in the course of the Late Neoproterozoic orogeny. Because the physical properties of the delamination process are not clear, we use it as a conceptual term accounting for the replacement of mantle lithosphere by an asthenosphere. Removal and replacement of the thickened lithospheric mantle roots potentially caused uplift of the northern ANS to elevations of more than 3 km, thus triggering exceptionally-rapid erosional unroofing of a ca. 10 km thick rock carapace, and some lateral extension. Delamination and erosional decompression potentially caused partial melting of ANS residual upper mantle and lower crust to produce the widespread post-orogenic magmas. We emphasize that removal of the lithospheric mantle also played a key role in lowering ANS topography to sea level. Our data show that lowering ANS down to sea level was significantly accelerated by post-delamination cooling and thermal subsidence. Unlike erosional denudation which is followed by isostatic uplift, thermal contraction causes net surface lowering. We show that thermal subsidence plays a critical role in lowering mountain belts, particularly in the latest stages, when the topography reaches a threshold of ∼ 1.0 km and erosion rates greatly decrease. Post-delamination thermal subsidence can cause 1.3 km of net surface lowering within 100 m.y. regardless of the state of relief and elevation. Therefore, orogenic belts that experienced removal or delamination of their mantle lithosphere (hot orogens) would rapidly rise, but would relatively rapidly fall too.

Late Neoproterozoic rise and fall of the northern Arabian-Nubian Shield: The role of lithospheric mantle delamination and subsequent thermal subsidence

http://www.utdallas.edu/~rjstern/pdfs/Jarraretal.pdf

H. Al-Zubi

Papers

Late- and post-orogenic Neoproterozoic intrusions of Jordan: implications for crustal growth in the northernmost segment of the East African Orogen