Petrography and Geochemistry of Dolomites in Kangan Formation, Persian Gulf

The Kangan Formation is a carbonate-evaporate sequence that is considered as a part of the largest carbonate reservoir in the South Pars Field at Persian Gulf. Petrography analysis led to the recognition of 5 different dolomite types: such as dolomicrite, dolomicrospar, dolospar, dolomite cement and saddle dolomite. Elemental studies on dolomicrite and dolomicrospar samples show a relative increase of Sr and Na and relative decrease of Fe and Mn in comparison with the dolomicrosparite samples. It is notable that the oxygen-carbon isotope trend in dolomite samples are due to slight influence of meteoric diagenesis (about dolomites type I, II and III) and burial diagenesis (about dolomites type IV and V). The dolomicrites have been undergone slight meteoric diagenesis, although they have formed in sabkha environment. The source of Mg for dolomicrites is the magnesium of seawater and interstitial waters equilibrium with seawater and on the other hand probably for the coarser grain dolomites in the Kangan Formation is connate waters and basinal brines. Based on the heaviest oxygen isotope in dolomicrite samples, paleotemperature of depositional environment of the Kangan Formation was around 44.5°C.