Tectono-magmatic reactivation of Téfidet Cretaceous trough during Cenozoic (Aïr, Niger)

Abstract

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.

Application of Spatial Techniques for the Identification of Discontinuous Aquifers of the Basement in Semi-Arid Environment: A Case of Bagzan Mount Plateau, Aïr Massif (North, Niger)

“…This direction is the second largest direction that has found Bagzan mount [46]. Moreover, in Tefidet trough North-South (NS) of Bagzan, N60˚-N70˚ accident is associated with dykes [47].…”

Contribution of Geophysical Prospecting (1D) to Characterize a Precambrian Basement Aquifers Agadez Region (North, Niger)

“…Many veins of quartz, micro grained rocks or porphyry fill the fractures. Tectonics is manifested by the presence of characteristic structural directions of general orientation: N0˚, N70˚ and N160˚ [27] [28] [29].…”

“…Several hydrogeological studies [1] [13] [21] [33] have shown the importance of Digital Elevation Model (DEM and satellites images) in the mapping of fractures related to tectonics fracturing and alteration in a location of aquifers in basement area. The DEM stumpage technique has proven its worth in mapping discontinuity of tectonic origins [27]. This approach allowed to improve the visibility of lines and these are reported by manual methods (digitalization).…”

“…Structural SynthesisThe synthesis of structural studies and fracturing mapping work resulting from the[27] studies in Aïr area show that the main directions of fracturing affecting Aïr massif over long distances are N-S (N0˚ -N10˚), NE-SW (N30˚ -N50˚) and DOI: 10.4236/ijg.2023.1411060 1184 International Journal of Geosciences N130˚ -N140˚. These orientations affect the land over several kilometers and these lineaments are organized according to N-S orientations in accordance with…”

Geotechnical Risk Assessment and Geological Origin of Building Fracturation in Agadez City (North Niger)

“…The Raghane shear system, passing to the eastern part of Agadez city (Figure 8, was the focus of a seismic event on 4 th July 1969 from geophysics interpretation map [15] . There is also a potential seismic zone corresponding to a system of strike slip faults oriented ~N75° (Figures 1 and 8), called "Agadez Lineament" [16] or the Guinean-Nubian Lineament (GNL) [17,18] that passed through the southern part of Agadez city [19,20] .…”