Lithological, Chemical and Mineralogical Revision of Ypresian Attapulgite Formations of Allou Kagne (Thi's, Western Senegal)

The chemical characterisation of Allou Kagne attapulgite ore according to the CaCO3 content, allowed to highlight three main facies attapulgites, calcareous attapulgites and marls. This lithological diversity would be the result of processes of leaching, hydrolysis and decarbonation more or less controlled by the structural context of the site. Mineralogical X-ray diffraction (XRD) and chemical X-ray fluorescence (XRF) analyses were carried out on hundreds of drillings distributed at the foot of This cliff (western Senegal). The results show that Allou Kagne attapulgite ore is a combination of several phyllosillicates (palygorskite, smectite and sepiolite) whereas they were formerly considered as hormites associated with quartz, opal and past gypsum.