Effect of heat on the crystalline phases in sand dunes of Ouargla region

Mohammed Laid MECHRI; Smail CHIHI

Mohammed Laid MECHRI Univ Ouargla, Fac. des Mathématiques et des Sciences de la Matière, Lab. Rayonnement et Plasmas et Physique des Surfaces, Ouargla 30 000 (Algérie)
Smail CHIHI Univ Ouargla, Fac. des Mathématiques et des Sciences de la Matière, Lab. Rayonnement et Plasmas et Physique des Surfaces, Ouargla 30 000 (Algérie)

Keywords: sand dunes, diffraction of X-rays (XRD), quartz, gypsum, heat

Abstract

The XRD spectra have shown that the predominant crystalline phases in the sand dunes of Ouargla region are quartz and gypsum. The heating of this sand at temperature range 200-1200 °C affect these crystalline phases. Appearance of anhydrite and bassanite in the heated sample at 200 °C, because of continuous loss of humidity from gypsum. Transformation of all gypsum into anhydrite in the samples heated at 400, 600 and 800 °C. Appearance of new crystalline phase, wollastonite, in the sample heated at 1000 °C. This latter is resulting from the beginning of interaction between the anhydrite and quartz. The heating of original sample at 1200 °C led to the interaction of all anhydrite with quartz. The anhydrite disappeared completely, instead of it the wollastonite appeared. Another phase, cristobalite, has appeared.