Provenance and Source Area Weathering Derived from the Geochemistry of Pre-Cenomanian Sandstones, East Sinai, Egypt

The study aimed at characterizing the geochemical compositions of the pre-Cenomanian sandstones of Gebel Ghazalani area, east Sinai. X-Ray Fluorescence (XRF), Induced Coupled Plasma-Mass Spectrometry (ICP-MS) and Induced Coupled Plasma-Emission Spectrometry (ICP-ES) analyses were used to determine the sandstone composition. Major, trace and rare earth element compositions of the sandstones have been investigated to determine their provenance, tectonic setting and the influence of weathering conditions. The studied succession (~214 m thick) starts by undifferentiated pre- Carboniferous sediments that unconformably overlies the Katherina Volcanics and followed upwards by the Lower Cretaceous sandstones of the Malha Formation. The pre-Cenomanian sandstones are enriched in SiO2 and High Field Strength Elements (HFSE) and are depleted in mobile elements, Large-Ion Lithophile Elements (LILE), transition metals and possess low contents of TiO2 and Fe2O3. Their Rare Earth Elements (REE) pattern displays high Light REE/Heavy REE (LREE/ HREE) ratio, flat HREE and a significant negative Eu anomaly. The source area may have contained quartzose sedimentary rocks. The geochemical data support deposition in a passive continental margin and the sediments were derived from felsic (granitic) source rocks. Trace and REE data as well as the high values of the weathering indices: Chemical Index of Alteration (CIA), Plagioclase Index of Alteration (PIA) and Chemical Index of Weathering (CIW) suggest moderate to extreme weathering conditions in the source area or during transportation. Also, they indicate that recycling processes might have been significant. Clay content, zircons and quartz dilution are responsible for the variation in REE contents.