Master Thesis Mineralogy and Geochemistry of the Sabkha Sediments Along the Mediterranean Coast from Surman to Ras Jdeir, Jifarah Plain, NW Libya

Abstract

The present work attempts to characterize the mineralogy and geochemistry of the sabkha brines and sediments along the Mediterranean Coast from Surman to Ras Jdeir, Jifarah Plain, NW Libya. the shuttle radar topography mission (SRTM) data were principally used in topographic analysis of the study area, to delineate the slope area, complete drainage network, watershed and cross section profile to identify morphology in the Jifarah Plain digitizing by computers programs by Arc GIS, Remote sensing data uses by landsat 8 operational land imager (OLI) is the new product from NASA under Landsat open source series which has been launched in February 2013, uses for interpretation of surface features and produce new geology mapping (determined location of all sabkha) in the study area. The studied sabkha sediments are composed essentially of gypsum, halite, calcareous sands, soil and algal limestone. The mineral composition for the studied sabkha sediments is chiefly composed of variable proportions of calcite, aragonite, quartz, microcline, orthoclase, gypsum and halite, clay minerals and heavy minerals such as ilmenite, magnetite, hematite, goethite, zircon, augite, tourmaline, rutile, biotite, garnet, monazite, hornblende, staurolite and pistachite. The Cl-/Na+ ratios in the studied waters range from 1.66 to 1.85, all slightly higher than the average seawater value (Cl-/Na+=1.17), suggesting that the studied brines may have not only marine but also terrigenic and anthropogenic origins. The studied brine water samples show high concentration of K+. This may be attributed to partial dissolution of detrital illite which constitutes part of the clay mineral assemblages of the studied sabkha. In the studied sediments, the major oxides CaO and MgO are the main constituents of the carbonate minerals. SiO2 is mainly in the form of quartz. Sometimes a high quotient of SiO2 together with the oxides Al2O3, K2O and partly of Na2O, TiO2 and Fe2O3 are essentially allocated within the structure of the feldspars and clay minerals. Part of Na2O and the content of Cl belong mainly to halite. Part of Fe2O3 and TiO2 may be accommodated as iron oxyhydroxides. Part of CaO and the content of SO3 are allotted within the gypsum structure. Ba, Sr, Pb and Cd are basically controlled by the carbonate fraction, while Br, Ni, Co, Cu, Zn, V and Cr are strongly correlated with Na2O and Cl. The studied sabkha sediments show low Cu/Zn, V/Cr, V/Ni and Ni/Co and U/Th ratios which suggest that these sediments were deposited in a well oxygenated environment.