The study area located between Figuil (Northern Cameroon) and Léré (Southwest Chad) belongs to the northern domain of the Pan-African Range of Central Africa (CPAC). The aim of this work is to highlight the petrogenesis of the hypovolcanic formations affecting the Pan-African base and the Cretaceous sedimentary basins of the study area as well as their geodynamic context. Hypovolcanic formations have a strong affinity with rocks of the continental tholeiitic series. The tholeiitic character with alkaline affinity constitutes the transition between alkaline and tholeiitic magmatisms. The low Rb/Sr ratios (0.24 - 1.24) constitute proof that the dolerites studied do not come from the partial fusion of Pan-African granitoids (Rb/Sr: 2.54 - 7.64) but rather from a mantle source as shown by the similar ratios of Zr/Hf (37.56 - 43.08), Nb/Ta (15.16 - 19.60) of dolerites from the Pan-African basement (DSP) and Zr/Hf (34.34 - 46.48), Nb/Ta (14.34 - 19.3) from dolerites from the Cretaceous sedimentary basins (DBSC). The enrichment in LREE relative to the HREE of the dolerites studied associated with the ratios (Tb/Yb)N (1.95 - 2.56), Dy/Yb (2.33 - 2.85) characterizes a mantle source of lherzolite with garnet.
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Ngarena et al. (2025) studied this question.
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