Geochemistry of Jizan shelf sediments, southern Red Sea coast of Saudi Arabiaجيوكيميائية رواسب رصيف جيزان ، الساحل الجنوبي للبحر الأحمر - المملكة العربية السعودية

Surface sediments from the Jizan shelf, southern Red Sea, were analysed for grain size and mineralogical and elemental composition in order to establish their geochemical characteristics. Texturally, sediments are classified into sand and mud; the latter dominates the shelf. Grain size variability and mineralogical assemblages present in the sediments largely control the abundance and distribution of CaCO3, organic carbon content (OC) and the major and trace elements. Sand sediments are composed of carbonate material of marine origin and contain high concentrations of Ca, Mg and Sr. Mud sediments are relatively rich in OC and are characterised by high concentrations of Al, Fe, Ti, Mn, Cu, Cr, Co, Ni, V and Ba. Unlike the sand, Mg concentration in the mud sediments seems to be controlled by stronger contribution from non-carbonate material. Factor analysis is applied to identify the variables accounting for most of the variance in the mud sediment samples. Three factors are found to describe about 78% of the variance. The first factor which accounts for 41% of the total variance is the Fe and Mn oxides that reach the area through episodic flooding. The second and third factors are the mud (22%) and the mineralogy (15%) of the sediments, respectively.