GEOCHEMISTRY OF THE GULF OF ADEN BEACH SANDS, AL-MUKALLA, YEMEN: PROVENANCE AND TECTONIC SETTING IMPLICATIONS

This research concerns with the mineralogical and geochemical composition of the Gulf of Aden shallow subsurface beach sands to identify the composition and tectonic setting of source area. The study discusses the limitation of using weathering indices and the factors hampered using these indices. Three shallow cores (1-1.5 m long) were collected from the coastal area at the mouth of wadis. Fuwwah (I), Ar Rukayb (II) and Shuhair (III) near Al-Mukalla, Yemen. The sediments are dominated by well to moderately well sorted fine-grained sands. The mineralogical composition is dominated by quartz followed by calcite with traces of plagioclase, k-feldspars, dolomite, clay minerals and amphiboles. The chemical composition is consistent with the mineralogy where the SiO2, CaO, Zr and Sr are the dominant oxides and trace elements, whereas other major and trace elements are strongly depleted. The sediments are compositionally mature and geochemically classified as quartz arenite to sublitharenite derived mainly from recycled sedimentary rocks that is consistent with the passive margin tectonic setting. The Chemical Index of Alteration (CIA) values suggest a low to moderate degree of weathering for the sediments of core I, whereas they show unweathered to poorly weathered source rocks of the sediments of cores II and III. Recycled sandstones mixed with carbonate sources and the hydraulic sorting minimized the effective usage of weathering indices in this study.