Mineralogical and physicochemical characterization of the Jbel Rhassoul clay deposit (Moulouya Plain, Morocco)

This study aims at the mineralogical and physicochemical characterization of clays of the Missour region (Boulemane Province, Morocco). For this, three samples were collected in the Ghassoul deposit. The analyses were carried by X-ray diffraction (XRD), X-ray fluorescence (XRF) and Scanning Electron Microscopy (SEM). The thermal analysis from 500 to1100°C was also performed on studied samples, and the fired samples were characterized by XRD and SEM. The XRD results revealed that raw Ghassoul clay consists mainly of Mg-rich trioctahedral smectite, stevensite-type clay, which represents from 89% to 95% of the clay fraction, with a small amount of illite and kaolinite. The associated minerals are variable amount of quartz, dolomite, hematite, gypsum and K-feldspars. The chemical analysis confirms the presence of Mgrich smectite (stevensite) with largest amount in sample containing the highest MgO. The SEM micrographs revealed the presence of automorphous structures with petalslike shape typical of smectite. The Thermal transformations determined by X-ray diffraction indicated that stevensite was transformed to enstatite from 800ºC. Diopside starts to appear from 700°C, which is confirmed by SEM observations, and the quartz is transformed to cristobalite when the temperature exceeds 1100°C.