Geochemistry of Marl Sediments within Fat ha Formation at Selected Localities, Northern Iraq

جيوكيميائية رواسب المارل ضمن تكوين فتحة في مناطق مختارة، شمالي العراق

A total number of (32) marl samples of Fat ha Formation (Middle Miocene) was collected from four selected localities in northern Iraq. Geochemical study included the analysis of (13) major and minor oxides by x-ray fluorescence and wet chemical methods and (7) trace elements by (XRF). The study shows that the oxides (SiO2, Al2O3, TiO2, Fe2O3, FeO, most MgO, Na2O, K2O, MnO, P2O5 and H2O+) are in the detrital fraction which comprises around (58%) of total mineral phases. These are clay minerals (39%), quartz (15%), iron oxides and Ti-minerals (3%) and feldspar (1%). The oxides (CaO, some MgO and CO2) comprise the chemical fraction, the carbonates (~ 42%). The trace elements (Co, Ni, Ga, Rb, Zr and some Sr) are within the detrital fraction, mainly the clay minerals and iron oxides. The elements (Ba and the remaining Sr) are within the carbonate fraction. The oxides and elements of the detrital fraction, in general, have a negative correlation with oxides and elements of the chemical fraction. The red colour of marl sediments is primary caused by the red pigment of haematite. The green colour is secondary and resulted from the reducing environments, initiated by the presence of organic matter.