干旱区生态环境知识资源中心

The present study focuses on the kaolin deposit in Kalabsha area south Western Desert of Egypt in an attempt to determine its possible source, tectonic setting, and weathering history by means of integrated petrographical and geochemical approaches. The petrographical study was worked by microscopic investigation and supported by X-ray diffraction analysis. X-ray fluorescence and inductively coupled plasma-mass spectrophotometry methods were used for the determination of the bulk elemental composition. Mineralogical analysis revealed that kaolinite is the main clay mineral component indicating a severe chemical weathering of Al-rich source rocks and complete leaching under warm, semiarid climatic conditions. The nonclay minerals are represented by quartz, iron oxides and hydroxides, Ti-bearing minerals, and zircon. Geochemical data show a prevalence of SiO2 and Al2O3 and enrichment of Hf, Nb, Ta, Th, U, and Zr that support the kaolinitic nature of the deposits and their derivation from a felsic granitic terrain. The high values of the chemical index of alteration and the lower values of the index of compositional variability also suggest an intensive weathered source area and the geochemical maturity of the sediments. Other relevant geochemical discriminant functions and plots reveal felsic igneous parent rock for the kaolin deposits. Q-mode hierarchical cluster analysis combined with the normalized rare earth element patterns played a crucial role in unraveling the origin of the studied deposits. The results show that the most probable source rock of the Kalabsha kaolin deposits is the intense weathering of relatively proximal Adara Adatalob granites and their similar rock types in the Arabian-Nubian Shield from the south Eastern Desert of Egypt.