The role of diagenesis in clay mineral forming: Middle Jurassic deposits, northeast Iran

Clay minerals are important for interpretation and understanding of burial diegenesis in mudrocks and cementation history of sandstones during diagenesis. The clay mineral from 11 samples from the Middle Jurassic, Kashafrud Formation in east Kopet Dagh Basin, analyized by X-ray diffraction. The identified clay minerals in these samples include kaolinite, illite, vermiculite, motmorellonite, mixed layer montmorillonie/illite and mica/illite. Also 5 thin sections of sandstones were analyzed by microprobe to identify clay minerals in cements. Kaolinite, illite and chlorite are the most abundant clay minerals in sandstones. Additionaly, high abundance of stable clay minerals, such as illite and chlorite, and small amounts of kaolinite and mixed layer clay minerals in kashafrud deposits, particularly in mudrocks, interpreted that had formed as result of high temperature during deep burial diagenesis.