Résumé
The Tuareg Shield results from the amalgamation, during the Pan-African orogeny, of more than twenty terranes comprising Neoproterozoic juvenile oceanic terranes and reworked or well-preserved Archean and Paleoproterozoic crustal blocks. All these amalgamated terranes are limited by trans-continental N–S shear-zones. Their main relative movements resulted from a Northern transpressional tectonic escape due to their squeezing between the West African craton (WAC) to the west and the East Saharan craton to the East. This configuration hampers tectonic correlations through the shield, but gives rise to major issues including the way along which amalgamation of the terranes occurred, their respective tectonometamorphic evolution and their origin. In order tohelp unravel the tectonometamorphic evolution of the westernmost part of the shield, we performed LA-ICPMS UPb zircon geochronology on samples from key lithologies collected through the Adrar des Iforas area (Mali). Samples were selected in order to represent a Neoproterozoic Andeantype active margin developed during subduction of the WAC beneath the Iforas terrane of the Tuareg Shield. In the Central Iforas Belt, arc-related calc-alkaline magmatism occurred as early as 716±6 Ma and was coeval with the 710-730 Ma old Tilemsi intraoceanic arc. Subduction-related magmatism persisted until 634±8 Ma and possibly down to 623±6 Ma, theage of the Tafeliant metadacite. Calc-alkaline batholiths were emplaced into a pre-Panafrican gneissic basement containingPaleoproterozoic units (such as the Tafeliant syenitic gneiss dated at 1966±9 Ma) and Archean components (inheritance in granitoids at c. 2.4-2.5 Ga and up to 2.8 Ga). Emplacement of syn-kinematic granitic plutons, associated to collision with the WAC, occurred at 604±5 Ma, whereas late-kinematic emplacement of the central batholith is dated at 599±3 Ma. East of the Adrar fault, the basement of the Eastern Iforas Belt contains Paleoproterozoic granitoids (Tin Essako orthogneiss dated at 2020±5 Ma), which were intruded by pre-kinematic granitoids such as the 630±6 Ma Tamaradant metadiorite. This suggests a possible synchronism of ante-collisional events oneither sides of the Iforas Granulitic Unit.