Petrography and Mineralogy of the Eocene Phosphate Deposit of Tobène (Taïba, Senegal)

The Tobene deposit forms, with those of NdomorDiop and KeurMor Fall, the large phosphate deposit of Taïba. The Tobene site has been the subject of lithostratigraphic, biostratigraphic, mineralogical, petrographic and geochemical studies. The lithostratigraphic and biostratigraphic studies dated the series from Lutetian to Bartonian composed of five lithological units, which are assembled by [1] in three formations. The mineralogical study shows three groups of minerals associated with the different phosphatic facies identified in the various sectors of Tobene: 1) characteristic minerals of sedimentological conditions; 2) minerals of diagenetic origin; 3) minerals of alteration. The petrographic study allowed an inventory of the constituting visible grains of the microfacies as well as the different phases of diagenetic and post-diagenetic transformations that may have affected them. It thus appears that the phosphatic ore of Tobene has undergone an extensive diagenesis (compaction, dissolution-recrystallization, epigenesis) to which a relatively intense ferruginization has been added.