Orogenic development of the Adrar des Iforas (Tuareg Shield, NE Mali): New geochemical and geochronological data and geodynamic implications

摘要: Laser-ablation U–Th–Pb analyses of zircon and allanite from magmatic metamorphic rocks the Adrar des Iforas in Northern Mali allow re-examining relationships between different crustal units constituting western part Tuareg Shield, as well timing events West Gondwana Orogen. Granulite-facies metamorphism Granulitic Unit (IGU) at In Bezzeg occurred 1986 ± 7 Ma 1988 5 respectively. This age is slightly younger, but consistent with that HT granulite facies event characterizing Ouzzal granulitic unit (IOGU), thereby substantiating view these once formed a single belt c. 800 km long. High-grade basement Kidal terrane surrounding IGU contain Paleoproterozoic crystallized 1982 8 1966 9 Ma. Inherited components (2.1 Ga 2.3–2.5 Ga) have ages similar to detrital zircons IGU. taken evidence block least until 1.9 Ga. East fault, Tin Essako orthogneiss dated 2020 Ma, escaped metamorphism. During Neoproterozoic, underwent long-lived continental margin magmatism. To west, this bounded by Tilemsi intra-oceanic island arc, for which gneissic sub-alkali granite was 716 6 A synkinematic diorite extends activity arc down 643 4 and, along literature data, indicates has life span about 90 Backward docking documented migmatites 628 Subduction related processes development active responsible back-arc basin Tafeliant area, deposition sediments intruded basaltic dacitic lavas, one 623 IGU, Tamaradant domain, metagabbros meta-anorthosites emplaced within greywackes geochemical characteristics typical subduction-related environments (enrichment LILE HFSE depletion). metadiorite intruding gave an 630 tentatively Pan-African subduction took place east Collision eastern African Craton best syncollisional tonalite, provides 604 Late kinematic shortly followed 599 exemplified emplacement monzogranite belonging complex Central Batholith. The geochronological evidences provided study proposing terrane, domain belonged probably extended northward include IOGU, later dissected major lithospheric scale faults during late orogenic phases.