GEOCHEMICAL AND MINERALOGICAL ANALYSIS OF RECENT FLOOD PLAIN AND RIVER DEPOSITS IN BAGHDAD, IRAQ

Abstract

Baghdad City, the capital of Iraq, is characterized by high population density and great variation in land use. The Tigris River divides the city into two sides: Rasafa (east) and Karkh (west). The army canal is an artificial water course in the Rasafa side. Baghdad is covered by Quaternary flood plain deposits of variable nature in which silt is the predominant fraction. Mineralogical analysis of the samples collected from the recent surface, subsurface and river deposits show wide range of heavy and clay minerals, which indicate the complexity of the depositional processes and the numerous genetic factors affecting their properties in addition to significant human influence on these sediments. The geochemical distribution of trace elements in the surface sediments of the study area show positive anomalous concentration of Pb, Zn, Co, Cu, and Sr, and negative anomalous concentration of Mn, Cr, and Ni which were observed in both sides of the city. Rasafa side is more complex due to the greater population density and dispersion of various human activities (agricultural, municipal and industrial). Comparing the activity concentrations of uranium of the studied samples, with those of the world average soils, it is clear that the Baghdad City is free from the radioactive pollution and uranium concentrations were within the normal limits. Statistical factor analysis of the sediments properties reflect the main factors controlling the mineralogy, texture and geochemistry of the studied sediments. These are mainly the parent rocks of the source area, (including sedimentary, basic igneous and metamorphic rocks in the north and northeastern parts of the country), dynamic energy of the river system as well as human activities. The mineralogy, texture and trace elements concentrations of the Tigris River sediments are comparable to those of the surrounding flood plain deposits in Baghdad which reflects the genetic relation of the two sampling media.