The Neoproterozoic evolution of the central-eastern Bayuda Desert (Sudan)

•In situ dated zircons define Saharan Metacraton and Nubian Shield boundary.•We propose extension of the Bayudian Event to 900–1000 Ma period.•Sr–Pb isotope separate juvenile and cratonic sources for Bayuda metagranitoids.•Peak of subduction magmatic–metamorphic activity occurred around 820–780 Ma.•The final terranes collision occurred between 714 Ma and 630 Ma.

In the central-eastern Bayuda Desert (Sudan), a border area between the Saharan Metacraton and juvenile Pan-African crust of the Nubian Shield, the Rahaba-Absol and the Abu Harik-Kurmut Terranes were amalgamated along suture and shear zones. U–Pb zircon ages by laser-ablation dating of metamorphosed granitoid rocks reveals ages interpreted as magmatic and metamorphic activities throughout the Neoproterozoic. The meta-granitoids are calc-alkaline porphyroblastic varieties of biotite metagranite (969 ± 5 Ma), quartzfeldspathic metagranite (914 ± 6 Ma), biotite–muscovite metagranite (912 ± 4 Ma) and coarse-grained meta-monzodiorite (909 ± 9 Ma, 818 ± 19 Ma, 669 ± 13 Ma) associated with the Rahaba-Absol Terrane, and medium-grained metagranites (813 ± 4 Ma, 808 ± 5 Ma, 799 ± 16 Ma), a meta-quartz–monzonite (810 ± 10 Ma), biotite metagranites (794 ± 15 Ma, 783 ± 13 Ma, 700 ± 7 Ma), alkali metagranite (645 ± 5 Ma), and porphyritic meta-quartz-monzonite (630 ± 4 Ma) associated with the Abu Harik-Kurmut Terranes. Th/U ratios of the zircon were used to distinguish between intrusion and metamorphic ages.The Neoproterozoic ages are interpreted as geodynamic pulses: a pre-Pan-African event 1000–900 Ma characterized by metamorphism and magmatism ending with the known Bayudian Event (920–900 Ma) in the Rahaba-Absol Terrane; a cycle between 850 and 775 Ma of subduction-related magmatism and metamorphism with a peak around 825–800 Ma; the final collision of the Rahaba-Absol and Abu Harik-Kurmut Terranes began before 714 Ma and ended probably before 645–630 Ma, documented by discordant E-W trending alkali metagranites and NE trending porphyritic meta-quartz–monzonite respectively. Theses ages of discordant intrusions constrain the post-collisional horizontal movement along the southern Keraf Shear Zone between 630 and ∼590 Ma. The existence of inherited zircon grains in some samples of Pan-African age indicated sedimentary activity contemporaneous with the island-arc magmatism and metamorphism. This was probably a period of extensive erosion of the earlier island arc material and later stacked crustal material after terminal collisional between the Abu Harik-Kurmut arc and the Rahaba-Absol continental terrane. Pb isotope data (feldspar, whole rock) and Sr isotopes corroborate the division into two terranes, the Rahaba-Absol Terrane as an old cratonic part of the Saharan Metacraton, and the Abu Harik-Kurmut Terrane as juvenile island-arc additions during the Pan-African.

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