Palygorskite from cave sediments: case study from Wadi Haqil, United Arab Emirates

0473049 - GLÚ 2017 RIV DE eng J - Journal Article
Zupan Hajna, N. - Skála, Roman - Al-Farraj, A. - Šťastný, Martin - Bosák, Pavel
Palygorskite from cave sediments: case study from Wadi Haqil, United Arab Emirates.
Arabian Journal of Geosciences. Roč. 9, č. 17 (2016), č. článku 689. ISSN 1866-7511. E-ISSN 1866-7538
Institutional support: RVO:67985831
Keywords : palygorskite * gypsum * cave sediments * X-ray powder diffraction * scanning electron microscopy * Ras Al-Khaimah Emirate
Subject RIV: DB - Geology ; Mineralogy
Impact factor: 0.955, year: 2016

The x-ray powder diffraction identification of clay minerals both in bulk samples and in separated clay fraction confirmed the presence of palygorskite in samples of cave sediments from Wadi Haqil (the western slopes of Musandam Mountains; Ras Al-Khaimah Emirate, UAE). Samples contain quartz, gypsum, smectite, kaolinite, calcite, and palygorskite, some of them chlorite, illite, feldspars, and goethite. Calcite dominates in most samples; smectite prevails in clay fraction. After heating, the 001 reflection of chlorite shifts to higher diffraction angles and its intensity decreases; these features indicate that the chlorite represent a Fedominant species. Unit-cell dimensions of major phases as refined by the Rietveld method are in agreement with literature data. Chemical composition of palygorskite was derived from unit-cell dimensions as follows: MgO content is 1114 wt% and Al₂O₃ 10-13 wt%. Clay mineralogy is only hard to ascertain from the scanning electron microscope (SEM) images even after being combined with the energy-dispersive spectrometer data. The SEM was also used to characterize gypsum grains; they often display flow deformation features. Studied cave sediments represent palygorskite-bearing weathering products and desert soils re-deposited from the cave surroundings by slope processes and wind and/or surface runoff. The mixture with other clay minerals, quartz, feldspars, etc. supports this interpretation. Fine-grained quartz fraction is probably wind-blown. Gypsum and calcite are the precipitates (crusts and/or cements), although gypsum can also be re-deposited from omnipresent gypsum-cemented surface sediments.
Permanent Link: http://hdl.handle.net/11104/0270217