MINERALOGICAL, GEOCHEMICAL AND SEDIM-ENTOLOGICAL CHARACTERISTICS OF LAKE NASSER SEDIMENTS, EGYPT

Abstract

Generally, the clay fraction of the bottom samples of Lake Nasser can be classified according to the total trace elements content into three geochemical sectors; southern sector (El- Genina, Abu- Simbil & Kostol), middle sector (El­ Madiq, Singari. & Amada) and northern sector (High Dam, Kalabsha, Wadi Abyad & Garf- Hussein). The southern sector of the studied clay fractions exhibits a relatively higher concentrations of the analyzed total trace elements (1645 ppm) followed by the northern sector (1393 ppm), whereas the middle sector shows a noticeable decrease in the concentration of the analyzed total trace elements •. (1121 ppm). The relatively higher concentrations of trace elements at the northern and southern sectors of Lake Nasser, may be explained by their adsorption onto clay minerals, their association with organic carbon content, their co- precipitation with iron oxides, relatively higher content of opaques, the weathering of basic and ultrabasic country rocks and to the local pollution due to the presence of high density of boats for fishing, particularly at Wadi Abyad area and Abu- Simbil Harbour. In contrast, the relative deficiency ofthe analyzed trace elements in the middle sector, may be attributed to the strong currents as compared with the more stagnant hydrodynamics prevailing at the most northern sector as well as the most southern sector (where sudden reduction in water velocity occurs). Moreover, the middle sector is less polluted relative to the other sectors, hence the observed deficiency in trace element concentrations.