Radiometric mapping of the Tondibia sector, western terminus of the Iullemenden intra-cratonic basin (Niamey, Niger)

The study area (Tondibia sector in the Niamey region of Niger) belongs to the western terminus of the vast Iullemenden intra-cratonic basin. In this basin, five (5) geological formations rest in major unconformity either on the Birimian basement or on the Pan-African basement. The most recent formation in this basin is the Terminal Continental (Ct) of Oligo-Miocene age. Only the last unit (Ct3) of this formation outcrops in the study area. This terminal unit of the Iullemmeden Basin is known for its iron mineralization, most often associated with lateritic facies. The aim of this study is to produce a surface radiometric map of the Tondibia sector (Niamey, Niger) in order to identify laterite facies zones, which are the preferred targets for iron mineralization in the Iullemenden Basin. The methodology used in this study consisted of field and laboratory work. In the field, rock outcrops were described and samples taken. In the laboratory, Surfer software was used to produce a radiometric map of the Tondibia sector. The radiometric data obtained using the SPP2 NF scintillometer in the sandy riverbeds show low values (10 to 30 cps), in contrast to the higher topography areas made up of lateritic facies (armour and carapace), where radioactivity is relatively higher (41 to 80 cps). These lateritic zones are rich in iron oxide, which has a strong affinity with the naturally radioactive elements such as thorium, potassium and uranium. As a result, the study area's high radioactive value zones are the preferred areas for prospecting iron mineralization.