Geochemical Characteristics of the Sarvak Formation in Izeh Zone, Zagros Region

The Sarvak Formation from the Bangestan Group, Late Albian to Cenomanian in age is an important petroleum reservoir in Iran. 5 outcrop sections in the Izeh zone, including the Bangestan Mountain as a type section with 831.5 m thickness, the Mangasht Mountain with 426 m thickness, the Payun Mountain with 480 m thickness, the north flank of Mish Mountain with 252 m thickness and the south flank of Mish Mountain with 348 m thickness were studied geochemically. The major elements (Ca, Mg), trace elements (Sr, Na, Fe, Mn) and carbon and oxygen isotopes studies indicate that the geochemical characteristics of the Sarvak Formation have been changed in the Izeh zone. High amount of Sr/Mn ratio and Sr content normalized to Ca and heaviest oxygen isotope of the Sarvak Formation carbonates in the north flank of Mish Mountain and some of the Bangestan Mountain carbonate samples indicate low amount of solution and closed diagenetic system in these outcrops compare to the Sarvak Formation carbonates in the south flank of Mish and Payun Mountains. The oxygen and carbon isotopes variation illustrate marine pheriatic digenesis in the north flank of Mish and Bangestan Mountains and meteoric diagenesis in the south flank of Mish, Mangasht and Payun Mountains. The geochemical difference, which observed in the studied sections at Izeh zone, could be related to the reactivation of deep seated structures such as the Hendijan and Bahregansar (Izeh) faults, which caused thickness, facies and diagenetic variations in these areas.