Mineralogy and geochemistry of Mishrif Formation from selected oilfield, south east of Iraq

Mishrif Formation (Late Cenomanian) has been studied in four oilfields in southern Iraq, and studied samples were examined by mineralogy and geochemistry analysis using XRF and XRD techniques. The mineralogical study reveals that dolomite and calcite are the main minerals in the rock formation in studied oil fields, whereas quartz and clay minerals (kaolinite, montmorillonite and illite) represent secondary minerals composition. For geochemical classification of Mishrif rock, Ca/Mg ratio was applied and this reveals that Calcitic Limestone is a major type in studied samples. The paleo - salinity has been examined by using Ca/Mg and Mg/Ca ratios and they referred to moderate salinity during deposition. Mg/Ca and Mn/Ca ratios have been applied to measure paleo-temperature, so infer a moderate paleo-temperature for Mishrif Formation in studied samples. Based on the comparison between low Sr/Ca and the relatively high Ca/Mg ratios, infer that a dolomitization process played the main role among diagenesis processes.