Lithostratigraphic and Geochemical Characterization of Tobene Phosphate Deposits: A Case Study of Tobene South 1

Abstract

Tobene is the third exploitation panel of the Taiba Phosphate deposits. It is divided into five sectors and its exploitation started in 2003 after the closure of the Ndomor and Keur Mor Fall panels. The Taiba phosphate deposit has been the object of several studies based on lithology, biostratigraphy, geochemistry, and petrography; however, few investigations on the variation in thickness of the phosphate layer within the Tobène sector have been conducted. This study seeks to analyze the lithostratigraphic and geochemical characteristics of the phosphate layer in the Tobène South1. Results from the lithostratigraphic study show from top to bottom the following succession: the sandy overburden, the sandstone formation, the Silico-feralitic formation, the variegated roof clays, the Taiba formation (homogeneous ore and heterogeneous ore), and the foliated attapulgite of the wall. Geochemical analysis reveals an unequal distribution of major oxides (P 2 O 5 , CaO, Fe 2 O 3 , Al 2 O 3 , and SiO 2 ). The area is dominated by P 2 O 5 concentrations between 20% and 32%, the K parameter (=CaO/P 2 O 5 ) has an average of 1.36. The iron associated with aluminum (feral) is present in the southern part and on the contours of the sector; the dominant silica concentration is 20%. Correlations established between the major oxides show a strong relationship with p-values << 0.05, nevertheless there is proportionality in the evolutions between the chemical variables CaO and P 2 O 5 , on the other hand, an opposite evolution between P 2 O 5 and the two chemical parameters silica (SiO 2 ) and feral.