Geochemistry of sands along the Ain Soukhna and Ras Gharib beaches, Gulf of Suez, Egypt: implications for provenance and tectonic setting

Abstract

Provenance, tectonic setting, and weathering condition of sands from the Ain Soukhna (AS) and Ras Gharib (RG) beaches along the Gulf of Suez, Egypt, have been studied using mineralogy and major and trace element data. The textural study reveals that the proportion of quartz is higher in RG (65–81 %) than in AS (47–54 %) sands. The compositional similarity between the AS and RG sands is tested statistically by the application of analysis of variance (ANOVA) at 95 % confidence level to avoid misinterpretation. The analyses of heavy minerals reveal that the AS sands are higher in ultrastable minerals (zircon, rutile, and tourmaline) than in RG sands. All sand samples of AS are classified as intermediate using (SiO2)adj content, while samples of RG are felsic in composition. The variations in SiO2, Fe2O3, MgO, and TiO2 contents and Al2O3/TiO2, K2O/Na2O, and SiO2/Al2O3 ratios among the two study areas reflect differences in source rock characteristics. The low Chemical Index of Alteration values in the AS and RG sands (CIA; 43.16–51.54) indicate low degree of chemical weathering, which may reflect cold and/or arid climate conditions in the source area. The A-CN-K diagram for AS and RG sands define a non-steady state-weathering trend, which indicates balanced rates of chemical weathering and erosion and indicates that AS and RG sands derived from granodioritic and granitic sources, respectively. The tectonic discriminate diagrams provide a good evidence for the rifting of Gulf of Suez, which is consistent with the general geology of Egypt.