This study uses field observations and new U-Pb ages of detrital zircon grains from three samples to question the stratigraphic position of the Firgoun and Niamey siliciclastic sediments, presumed to be Neoproterozoic in age. Sharing several lithological similarities with the Late Cryogenian ''Triad'' of the Taoudenni, Gourma, and Volta basins, the uppermost siliciclastic sediments of the Firgoun and Niamey areas were likely also deposited during this period. This is corroborated by matrix-supported diamictites with faceted or striated pebbles as well as by structures resembling cryoturbation processes. However, the detrital zircon U-Pb age record that we present here for the lowermost deposits of Firgoun and Niamey provides mainly Paleoproterozoic ages, and very few Archean ages, altogether in a range from 1822 AE 9 to 3392 AE 9 Ma. Therefore, the new data only show that the Firgoun and Niamey sediments were deposited before about 1800 Ma. Nevertheless, the U-Th-Pb zircon age data allows examining the possible provenance of the sediments. We show that the latter was likely in the westerly close vicinity of the studied areas. The Archean zircons are likely inherited, and possibly originating from a more westerly source. The nearby source of the Niamey and Firgoun sediments suggests that a high topographic relief was still existing in the south-central part of the West African Craton in the Mid Neoproterozoic.

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The Téfidet trough (eastern Niger) belongs to the Ténéré megasystem set of Cretaceous rifts N130°E to N170°E oriented, corresponding to the direction of the Lake Chad-Hoggar tectonic axis. The study of the relationship between the structure of the trough and alkaline fissural volcanism that developed there from the Oligocene to Plio-Quaternary shows the uniqueness of the Téfidet trough compared to the neighboring contemporary volcanic areas of Hoggar, Cameroon, and southern Aïr. The tectono-magmatic reactivation of the Cretaceous Téfidet trough developed in two steps: – a period contemporaneous with the Tuareg shield bulging (Aïr, Hoggar, Iforas);– a subsequent extension period generally N060°E, which has persisted since the opening of the South Atlantic (upper Jurassic to Plio-Quaternary). The fissural volcanism, due to the reactivation of Pan African and Cretaceous faults evolved concomitantly with the N060°E extension (syn-magmatic micro-fractures with basaltic filling), in several steps, from Oligocene to Plio-Quaternary. This study highlights the existence of periods of quietness and recovery of volcanic activity, for which two assumptions can be made: – no enough absolute datings,– apolyphased extension of the rift. The latter hypothesis seems to be supported by three periods of volcanic quietness, 28–24 m.y., 20–14 m.y. and 8–5 m.y., observed in the northern and the southern Aïr, Gréboun and Todgha, respectively.

The study area is located at the southern end of the Gorouol greenstone belt, northwestern Niger. This region contains significant deposits of Copper and Molybdenum hosted in intrusive rocks metamorphosed in the green shale facies. This deposit was previously considered a porphyry system of Copper (Cu) and Molybdenum (Mo) without having been the subject of advanced research. The objective of this study is to confirm or refute this hypothesis and to date the mineralisation in an absolute manner in order to readjust the mineralising episode in the history of the West African Craton. The methodology used within the framework of this study is the isotopic dating by the Re-Os method carried out on the pyrites of the host rock. The results of this analysis give an age range between 2158 ± 50 Ma and 2110 ± 51 Ma for the Cu-Mo mineralisation. This age range represents the West African Craton scale to an episode of magmatic accretion. During this accretion, the subduction phenomena between the Crusts (Oceanic and Continental) would have been favourable for the formation of the Cu and Mo mineralisation of Kourki.

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