Kaolinite in the Upper Cretaceous-Paleogene sedimentary facies of Bahariya Oasis, Egypt: Nature and origin
Baioumy, Hassan; Mohamed Hassan, Mervat; Said,
published: Aug 1, 2009
ArtNo. ESP155025302007, Price: 29.00 €
Kaolinites in the sedimentary facies of Bahariya Oasis, Egypt were found in four formations; the Cenomanian clastics of the Bahariya Formation, the Eocene iron ore of the Naqb-Qazzun Formation, the late Lutetian - Bartonian glauconites of the Hamra Formation and the conglomerates and sandstones of the Oligocene Qatrani Formation. Kaolinites occur as beds, bands, lenses or pockets of white to gray deposits either as single phase or mixed with other clay minerals such as smectite, glauconite and halloysite. Based on their genesis the kaolinites were subdivided into authigenic and detrital kaolinites. Authigenic kaolinites occur as well-developed stacked hexagonal and book-like flakes in the sandstones of Bahariya and Qatrani Formations and rosette-like shaped in the halloysite pockets inside the iron ore of the Naqb-Qazzun Formation. These kaolinites were formed as a result of alteration of Al-rich minerals such as feldspars and glauconite. Detrital kaolinites occur as undefined, deformed and crumbled flakes in the kaolinite beds of the Hamra Formation. They were formed as a result of tropical weathering of pre-existing Al-rich rocks such as the crystalline igneous rocks that are situated south and southeast of the studied localities reflecting prevailing tropical conditions during that time.