Geochemical and mineralogical study of the fluvial deposits at Abul Khasib area, south east of Iraq

Abstract

Nine sediment samples were collected from three sites at the banks (levees) of Sarraji, Hamdan and Abul khasib creeks branching from Shatt Al-Arab river, southeastern Basrah with depths of 0.5, 1.0 and 1.5m, respectively. Grain size distribution and statistical parameters revealed that the deposits are mainly composed of silt and clay with very small portion of sand, and have mud type texture. There is a tendency of increasing in silt percentage from Sarraji toward Abul Khasib area and decreasing in clay percentage with depth. Generally, the sediments are poorly sorted, coarse to strongly coarse skewed and platykurtic to very platykurtic deposited in quiet environment and low energy conditions. Chemical analysis showed that all samples have high concentration in SiO₂ and CaO in comparison with Al₂O₃, Fe₂O₃, MgO, SO₃, K₂O and Na₂O. These results are generally in agreement with the mineral composition. Mineralogically, the sediments understudy consists of quartz, feldspar, calcite, dolomite and gypsum. Clay minerals assemblages are: chlorite-montmorillonite mixed layers 37%, Illite 20%, Chlorite 18%, Kaolinite 14% and Palygorskite 11%. Increasing in Ch-Mont. percentage could be an evidence of high intensity of diagenetic alteration processes in depositional environment. The clay mineral assemblages proved that the recent sediments of the studied samples were derived from the basic igneous and metamorphic rocks, while acidic igneous and sedimentary rocks sources are less important. The deposition environment of these minerals may be characterized by an arid to semi-arid climate in the source area.