Abstract
The combination of the mineralogical and geochemical composition of shales is considered a key to decipher their environment evolution, weathering, climatic conditions, and provenance. The Upper Cretaceous-Lower Tertiary succession is extensively dispersed in Egypt. The present work is devoted to studying the Dakhla shales of (Maastrichtian- Danian), Duwi (Campanian) and Quseir (pre-Campanian) formations. Chemical and mineralogical analyses were conducted by using seven representative surface sections from Dakhla Oasis. Dakhla shales are dominates by Smectite and kaolinite. The average percentages of SiO2, Al2O3, CaO, MgO, Na2O and K2O are subordinate values. In contrast, Al2O3 contents of Dakhla shale, TiO2, P2O5 and Fe2O3, contents are relatively higher than common shale composition. The CIA and CIW high values due to clay minerals and the absence of feldspars. This is also confirmed by the smectite domination and subordinate kaolinite in these formations. The ICV values for Dakhla and Duwi shales are 0.59 and 0.74 (ICV < 1). The shale is mature and deposited in a quiescent environment. Whereas the ICV for Quseir shale is 1.24, it can be incidental that it is immature. The shale is wholly detrital and a product of moderate to intensive weathering. The provenance was constituted of granitic and basaltic source rocks, and the parent provenance is basalt. Consequently, the shale is deposited under fluvio-marine environments, and the prevailed condition was of alkaline chemical affinity probably passed through different environments varying from a fluvial, eolian and shallow marine.
Highlights
Geochemical analysis of shale can introduce information on the environment, provenance, weathering conditions, and sediment recycling (Peng et al, 2014)
differential thermal analysis (DTA) and Therrmogravimetry (TG) results are explained by the form of derivatograph (Fig. 2)
The formation of smectite requires the presence of Na & K, and silicates formed by the hydrolysis of Ca, Mg and Fe tend to combine with silica to form smectite (Millot, 1970; and Keller, 1970). Kaolinite It predominates in studied Dakhla shales, but it present as a minor in Quseir and Duwi shales
Summary
Geochemical analysis of shale can introduce information on the environment, provenance, weathering conditions, and sediment recycling (Peng et al, 2014). The geochemistry imitates mostly the principal mineralogy of the parent rock and the overlaid belongings of pre- and post-depositional chemical weathering, well-ordered by element mobility and founding secondary phases such as clays (Philippe Négrel et al, 2021). Their mineralogical and chemical composition were influenced by factors such as weathering, source provenance, and diagenetic processes. The shales geochemistry and mineralogy, especially clay minerals, are used to estimate the environments and provenance. The novelty in the present study, the shale is represented different stratigraphic ages, Dakhla shales (Maastrichtian-Danian), Duwi (Campanian), and Quseir (pre-Campanian) formations and various locations, Seven representative surface sections from Dakhla Oasis were measured, chemically and mineralogical analysed (Fig. 1)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
