اسم المؤلف:
صفوك عاصي حسین العبیدي
اسم المشرف:
صالح محمد عوض
المستخلص:
Rock geochemical survey was conducted on the exposures of Upper Oligocene - Middle Miocene successions (Anah, Euphrates, and Fatha formations) along the western bank of the Euphrates River from Al - Qaim to Abu - Jir village near Al - Ramadi. Soil geochemical survey was also carried out in area located between Al - Baghdadi and Abu - Jir village. A total of 113 Samples were analyzed for major, minor components (CaO, MgO, SiO2, Al2O3, Fe2O3, Na2O3, K2O, TiO2, MnO, P2O5, SO3, and loss on ignition (LOI)), also some trace elements were analyzed (Rb, Ba, Sr, V, Cr, Ni, Cu, Zn, Ga, Cd, Th and U). Seven (7) samples were collected from Anah Formation from its exposure in Haqlan site; Thirty two (32) samples were collected from the Euphrates outcrops along the traverses of about 192 km, twenty nine (29) samples also of Euphrates Formation were collected from six stratigraphic sections (Al - Khaniq, Samndan, Al - Fuhaimi, Haqlan, Raghadan, and Al - Baghdadi); Twenty five (25) samples were collected from Fatha Formation along a traverseof about 253 km. In addition, twenty (20) soil samples had been collected as well.Mineral investigation showed a prevalence of pure calcite (97.14%) in Anah Formation, pointing out a non - dolomitzed typical reef facies, whereas, in the Euphrates Formation, the predominant mineral in traverse samples is dolomite of (82.02%) average. The vertical distribution of minerals in Euphrates Formation also emphasized the prevalent of dolomite in all stratigraphic sections, except in Haglan and Al - Baghdadi sections, where calcite is a predominant (94.13% and 58.47% respectively). The lateral mineralogical distribution in the Fatha Formation reveals that the dolomite (36.5%) is the main mineral, followed by gypsum (32.5%), then calcite (16.9%), clay minerals and quartz (12 %). The main mineral constituents of soil are calcite (30.2%), gypsum (28.03%), clay minerals and quartz (21.81%), dolomite (12.12%). The Rocks in these Formations are geochemically classified according to Ca/Mg ratio. Consequently, Anah Formation is considered as calcitic limestone of high purity, Euphrates Formation rockswere classified to slightly calcareous dolomite, calcareous dolomite, and dolomite and Fatha Formation carbonate rocks were classified to highly dolomitic limestone, dolomite, slightly calcareous dolomite, and calcareous dolomite.The vast majority of major, minor oxides (Al2O3, SiO2, Fe2O3, Na2O3, K2O, TiO2, MnO, P2O5) and trace elements (Rb, V, Cr, Ni, Cu, Zn, Ga, and Th), in Anah, Euphrates, Fatha and soil samples are mainly incorporated within clay minerals. The Ba, Cd, have weak relationship with alumina because they didn't incorporate within clay minerals, but may exist within organic matter and carbonate minerals, while Sr incorporated in carbonate rocks and gypsum and U in dolomite.The geogenic is the main factor controlling the soil chemistry in the study area. It is a residual deposits that had been mostly derived from the parent rocks of Fatha Formation, rather than the Euphrates Formation forming sedimentary overburden of different thickness. The dominance of trace elements in soil as compared to Fatha and Euphrates samples can be ordered as follow : V, Zn, Cr, Ni, Cu, Sr, Rb, Ga, Th, is ordered as : Soil> Fatha Formation > Euphrates Formation.The spatial distribution of major, minor and trace elements are presented on dot maps, and their lateral variations are graphically presented and explained. Then, by application the accumulative probability curve method, the geochemical background, threshold and anomaly of minor and trace elements in Euphrates, Fatha formations and soil samples are computed and determined. The most determined anomalous values of elements are represent local and insignificant anomalies and not traced to mineralization. However significant anomalies recorded in certain soil samples, such as samples no. 42s display Ba significant anomaly (2988 ppm), 6H is characterized by peculiar high concentration of Sr (5680 ppm) which considered as anomalous soil sample of celestite mineralization, and Sample no. 65s exclusively was characterized by high abundance of pure native sulfur (69.19%) potentially indicates a significant sulfur mineralization.The study showed that the Anah Formation had been deposited in reef environment. Sr was used as an evidence of the depth of the sedimentary basin, the low Sr content in the Euphrates Formation as a result of dolomitization impact that released Sr from calcite lattice. The Euphrates Formation was deposited in the shallow lagoon environment. In the Middle Miocene, circumstances of the sedimentary basin have been changed to shallow, semi - restricted highly evaporitic, hypersaline lagoon environment of Fatha Formation.
