Petrography and Mineralogy of the Eocene Phosphate Deposit of Tob&amp;#232;ne (Ta&amp;#239;ba, Senegal)

Moustapha Diagne,Mouhamadou Bachir Diouf,Mamadou Fall,Ndèye Penda Dione,Pierre Giresse

doi:10.4236/gep.2018.65016

Abstract

The Tobene deposit forms, with those of NdomorDiop and KeurMor Fall, the large phosphate deposit of Ta&#239ba. 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.

Highlights

The phosphatic mineralization in Senegal has been the subject of numerous stratigraphic and paleontological studies [2]-[10] showing a variation of the characters according to the structuring and compartmentalization of the deposits.The phosphates of Taïba are with those of Matam, located in the North of Senegal, the most important phosphate deposits pointed out and exploited in Senegal [1]
The phosphatic group of Taïba (KeurMor Fall, NdomorDiop and Tobène) was formed around a NE-SW synclinal ridge [5], in a very calm tectonic basin, favourable to chemical sedimentation with formations dipping to the West [11]
The Tobène phosphate deposit in question comprises three formations: the formation of foliated attapulgite clay, on which lies the formation calcium phosphate, including the heterogeneous and homogeneous members, which is surmounted by the formation with alteration alumina phosphate with platy flint rich in Daucina, alternating with clay and phosphate sand [1]

Summary

Introduction

The phosphates of Taïba are with those of Matam, located in the North of Senegal, the most important phosphate deposits pointed out and exploited in Senegal [1]. May 25, 2018 calm tectonic basin, contains phosphatic calcic and alumino-calcic phosphatic units. It is exploited in three deposits: NdomorDiop, KeurMor Fall and Tobène (Figure 1). The Tobène panel, the last to be exploited, is located to the southeast of those of NdomorDiop and KeurMor Fall and the preliminary studies on there are relatively brief. The aim of this paper is to characterize the phosphatic ore of Tobène, from a lithostratigraphic, petrographic and mineralogical point of view, compared to the other panels

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Methods

Conclusion