Palygorskite, Chlorite and Illite Minerals in the Dukhan Sabkha Deposits, Qatar

Abstract

The clay samples were studied using X-ray diffraction. The range of the run was between 2°and 40° and the run was 1.2°/min. Electronic Microscope also used in the study by using great magnification range from X20 up to 1000,000 to allow to examination the surfaces of fine grains and to takes photographs with great focus. Chemical analyses also carried out under the SEM, using energy-dispersive X-ray spectrometry to define their dominant elements. From the study, it emerged that the dominant clay minerals in the samples are palygorskite, followed by chlorite and illite. Based on the peak area measurements, the mean percentage of palygorskite in the clay deposits included dolomite and anhydrite is 59% (approximate percentage is 34%-79%). It is 23% for chlorite (approximate percentage is 7%-40%) and 9% for illite (approximate percentage is 4%-13%). After excluded dolomite and anhydrite from the samples, it is 65% for palygorskite (approximate percentage is 47%-85%), 25% for chlorite (approximate percentage is 8%-40%) and 10% for illite (approximate percentage is 6%-15%). Through EDX analyses of the palygorskite needles it was inferred that the P is the dominant element, followed by Si, Mg, Al, Ca, and K. Phosphate nodules of a globular shape (spherulites) in various sizes (1-<2 μ) also occur in most of the clay samples, especially that rich in palygorskite. In some samples, the phosphate nodules were present in small groups connected together as bunches.