ABSTRACT: Isotopic study of carbonate and dolomite facies in the Kangan and Dalan formations in the south of Iran
Rabbani, Ahmad Reza , V. I. Vernadsky institute of geochemistry and analytical chemistry, Moscow, Russia
Dalan (upper Permian) and Kangan (lower Triac) formations were deposited in an extensive carbonate platform under an arid climate. These formations makes up the essential part of the Nar and Kangan reservoirs of gas and gas condensate in the south of Iran. Detailed field and pertrographic investigation of over 1200 meter carbonate sequence of the Kangan and Dalan formations led to the recognition of several shallow marine (tidal flat, sabtidal, lagoon; bar and open marine) facies.Environment of deposition of these limestones were a showaling-upward. The transition from Dalan to Kangan denotes a period of drastic change in the depositional environment and the chemical milieu of the sedimentation basine. These changes are reflected by a marked positive excursion of carbon and oxygen isotopes. Petrographic, chemical and isotopic studies of the dolomites in the Kangan and Dalan formation reveal that dolomitization was the result of several diagenetinc events, and the neomophic alteration of these dolomites significantly modified their original chemical signatures. Dolomite in the Kangan and Dalan formed in two stages by different mechanisms:in Dalan formation dolomitization occur in the early phase of syngenetic (penecontemporaneous) replacement of pre-existing carbonate in an arid climate on a supratidal flat. In Kangan, dolomite formed during deep burial.
AAPG Search and Discovery Article #90913©2000 AAPG International Conference and Exhibition, Bali, Indonesia