Zircon U–Pb and Lu–Hf isotopic systems in ediacaran to Fortunian “Taourirt” granitic ring complexes (Silet and In Tedeini terranes, Tuareg shield, Algeria)

International audienceThe Tuareg shield in North-West Africa is composed of an assembly of Neoproterozoic continental and oceanic terranes, as well as Archean and Paleoproterozoic terranes separated by major continental shear zones. In the Silet terrane, the igneous suite of Silet-Taourirts is composed of post-collisional ring-complexes of ferroan alkaline and alkali-calcic granites. Six ring-complexes have been dated using the U–Pb SHRIMP technique on zircon. The alkaline Tin Erit (584.8 ± 2.0 Ma), Tihoiiarene (569.8 ± 4.8 Ma) and Tioueine (561 ± 6 Ma) complexes are older than the alkali-calcic Issedienne (538.7 ± 2.9 Ma), Tesnou (536.5 ± 6.7 Ma) and Ait Oklan (529.3 ± 3.1 Ma) complexes. Sharing an enriched mantle source, the complexes display a secular variation of crustal contamination marked by decreasing εHf(t). The oldest alkaline complexes are related to the tectonic escape of the Tuareg terranes to the north after the climax of Pan-African orogeny, while the youngest alkali-calcic complexes were emplaced after the 575-555 Ma intra-continental Murzukian event