Geochemical and statistical characterization of the phosphate facies of the Farim-Saliquinhé phosphate mineralization (Guinea-Bissau)
Résumé
The Eocene Farim-Saliquinhé phosphate mineralization (FSPM) is a buried sedimentary deposit located in the
northern part of Guinea-Bissau, discovered and spatially constrained during the 1980s by the French Geological
Survey (BRGM). In the present work some of the data collected at that time are reworked in the framework
of the development of a 3D geological and geochemical model of this mineralization. We show the usefulness
of two classical multivariate statistical methods – principal component analysis (PCA) and cluster analysis (CA)
– applied to eight geochemical variables (P2O5, SiO2, Al2O3, Fe2O3, CaO, MgO, F and CO2) measured in 247
samples from phosphate facies, for differentiation of samples taken from the different phosphate facies
recognized in the FSPM, namely the main ore FPA (30 to 35% high grade phosphate), the calcareous low grade
phosphate FPB (10 to 20% P2O5) (both Lutetian), and a mineralized Upper Eocene to Lower Oligocene cover
(mainly including the FPO level and a silico-aluminous phosphate bed), overlying the FPA, which can also be
considered a third set of phosphate facies associated with the FSPM.