PROVENANCE OF SEDIMENTS OF SAND DUNES IN THE WESTERN PARTS OF THE EUPHRATES RIVER, IRAQ

Abstract

This study is concerned with the heavy minerals (HM) of the + 63 micron fraction of the sand dune sediments, which cover 608.686 Km2 of an area from Najaf to Samawa, and the southern borders of Al-Qadissiya Governorate. Moreover, grain size analysis, chemical and XRD analysis are carried out. HM analysis indicates that the proportion of the unstable minerals makes about 12.7% for Najaf dunes and 44.83% for Samawa – Qadissiya dunes, whereas the metastable minerals make about 15.81% and 21.03% and the ultra stable minerals make about 16.83% and 3.01% for Najaf and Samawa – Qadissiya dunes, respectively. Opaques are present in high proportions reaching about 34.04% for Najaf dunes and 28.54% for Samawa – Qadissiya dunes.Grain size analysis indicates that the sediments of Najaf dunes are coarser than the sediments of Samawa – Qadissiya dunes and the sorting of sediments of Najaf dunes are medium, while sediments of Samawa – Qadissiya dunes are fine. Moreover, the sediment of Najaf dunes are more mature than the sediment of Samawa – Qadissiya dunes due to the ZTR index.Chemical and XRD analysis revealed that the sediments of the studied dune fields are composed essentially of quartz, feldspar; as the dominant minerals with a paucity of carbonate and sulphate minerals, in addition to heavy minerals. Clay minerals occur in Najaf dune fields represented by montmorillonite, palygorskite and kaolinite and the same clay minerals except montmorillonite occur in Samawa – Qadissiya dune fields.All results indicate that Najaf sand dunes are derived from felsic igneous rocks (granitoid rock), metamorphic rocks (schist and gneiss) and older sedimentary rocks, while Samawa – Qadissiya dunes are essentially derived from metamorphic rocks (schist and gneiss), basic igneous rocks (Basalt and Gabbro) and older sedimentary rocks.The Dibdibba Formation (Pliocene – Pleistocene) in Tar Al-Najaf, where the sediments are transported from the Arabian Shield, is the most important source for supplying sand forming the dune fields of Najaf, while the source area that supplies the sediments of Samawa dunes is mixed, the essential one is the surrounding formations, where the sediments are transported from Arabian Shield and the second source is the Euphrates River, where sediments are transported from the north (Syria and south of Turkey).