This study focuses on the petro-structural characterization of the Pan-African terrane of Tchilit in the Gofat-Tafadek sector, within the Aïr Massif (Northern Niger). The Aïr Massif consists of metamorphic rocks intruded by granitoids. Previous works related to the petrographic characterization and structural analysis of the Pan-African terrains in this region are superficial and fragmentary. The general objective of this study is to analyze the petro-structural characteristics of the Pan-African formations. Specifically, the study aims to: (i) determine the petrographic characteristics of different facies, (ii) identify the deformation structures that have affected them, and (iii) establish a relative chronological relationship between the main deformation phases. To achieve these objectives, a methodological approach was implemented, incorporating petrographic analysis and structural measurements. The schistosity/foliation planes, fault planes, and fractures were analyzed using the Win-tensor and Stereonet programs. Petrographic analysis shows that in the Gofat-Tafadek sector, the Tchilit terrane consists of phyllites, chlorite schists, biotite quartzites, mica schists, muscovite quartzites, quartz schists, paragneiss, biotite orthogneiss, amphibolites, metarhyolites, meta-arkoses, two-mica granites, heterogeneous granites, and pegmatites. Structural analysis of the Tchilit terrane in the Gofat and Tafadek sectors reveals three deformation phases: D0, D1 and D2. The extensional deformation phase D0, characterized by a NNE-SSW extension direction (N20°), is evidenced by normal microfault mirrors observed in quartzites. The first deformation phase, D1 (Pan-African), is ductile to semi-ductile and comprises two episodes: D1a (ductile) and D1b (semi-ductile to brittle). The first ductile episode (D1a), related to Pan-African shortening, is characterized by an ENE-WSW shortening direction (N70° on average), while the second semi-ductile to brittle episode (D1b) is marked by an average shortening direction of NE-SW (N40°). The second deformation phase, D2, marked by a shortening direction of N10° (NNE-SSW), is late to post-Pan-African. It is characterized by the development of a fracture schistosity. The structural evolution over time of the shortening direction in the Tchilit terrane highlights a sinistral counterclockwise rotation, from the ENE-WSW direction (Phase D1) to the NNE-SSW direction (Phase D2). This indicates a deformation continuum during the Pan-African event, associated with the convergence between the West African Craton, the São Francisco Craton, the Congo Craton, and the Saharan Metacraton.

The Ayorou and Kandadji sectors are located in northern Niger’s Liptako in the Téra-Ayorou pluton, composed mainly of granodiorites and various granites. This study investigates the structural characteristics of the granitoids of the Téra-Ayorou pluton in the Ayorou and Kandadji areas. Field and laboratory work revealed two major deformation phases, D1 and D2. Tectonic structures observed on granodiorites and synkinematic biotite granite (foliation, mineral lineation, shear corridors, folds and boudins identified) were assigned to deformation phase D1, which is ductile to semi-ductile. Other structures (quartzo-feldspathic, pegmatitic and doleritic fractures and veins) affecting all lithologies, have been linked to deformation phase D2, which is frankly brittle. The average direction of shortening of the compressive stress responsible for setting up the foliation (S) is generally N-S (Z N185° in Ayorou) and NNE-SSW (Z N225° in Kandadji). The shear zones were controlled by a shortening of average direction Z N195° (dextral shear zones) and Z N135° (senestial shear zones).