Clay Minerals as Indicator of Phosphatogenesis: A Case Study of Sokoto Basin, Northwestern Nigeria

Phosphate deposits which occur in the Sokoto Basin of northwestern Nigeria is more pronounced in the shales of Dange Formation which recorded value ranges of 32- 36% P2O5. Minor occurrences were documented in shale of Dukamaje Formation and the limestone of Kalambaina Formation. However, non phosphatic siltstone, marl, shale and sandstone also occur. Clay mineral evaluation of the phosphatic and non phosphatic units was undertaken in order to study their relationship with phosphatogenesis. Result of analysis shows that the clay mineral distribution in the phosphate bearing sediments and non phosphatic units are consistently different. Kaolinite and hydrargillites are associated with phosphate bearing sediments whereas montmorillonite is typical of non phosphatic ones. The study of clay mineral distribution appears to be a good tool in phosphate exploration in an epicontinental inland basins. Keywords: Phosphatogenesis, Clay mineral, Sokoto Basin, Kaolinite, Montmorillonite, Paleocen