Document Type : Original Research Paper

Authors

• Mohadeseh Janbaz ¹
• Hassan Mohseni ²
• Alireza Piryaei ³
• Rudy Swennen ⁴
• Bizhan Yousefi Yeganeh ⁵
• Hassan Soradeghi Sufiani ⁶

¹ Ph.D., Department of Geology, Faculty of Science, Bu-Ali Sina University, Hamedan, Iran

² Associate Professor, Department of Geology, Faculty of Science, Bu-Ali Sina University, Hamedan, Iran

³ Ph.D., Geology Department, Exploration Division, NIOC, Tehran, Iran

⁴ Professor, Faculty of Earth and Environmental Sciences, KU Leuven, Leuven, Belgium

⁵ Assistant Professor, Department of Geology, Faculty of Science, University of Lurestan, Khorramabad, Iran

⁶ M.Sc., Geology Department, Exploration Division, NIOC, Tehran, Iran

Abstract

Middle-late Eocene Shahbazan Formation is exposed in the Lurestan area (Zagros region). The diagenetic features have been studied based on the data from five surface sections and four additional exploration wells. This investigation was carried out on the petrography of 700 thin sections, Cathodoluminescence on 40 thin polished samples, Scanning Electron Microscope on six samples and Electron Probe Micro-Analysis on 11 thin polished sections. the most conspicuous diagenetic processes affected on the Shahbazan Formation are dolomitization, cementation, neomorphism, physical and chemical compaction, dissolution and dedolomitization, of which dolomitization is the most important. Dolomite distribution in studied sections suggest that fluid flow was probably toward SW of studied area, since the extend of dolomitization waning in this direction. Since the dolomites of the Shahbazan Formation are overlain by the Asmari Formation, the dolomitization predates deposition of the Asmari Formation and occurred in eogenesis. Majority of calcite cements deposited before dolomitization in eogenesis, excluding parts of the blocky and poikiotopic calcite which may form in telogenetic and mesogenetic realms respectively. Degrading neomorphism occurred in marine realm. Part of dissolution occurred in meteoric vadose of eogenesis. Compaction commenced in meogenesis with increasing over burden due to deposition of the Shahbazan Formation and culminated after deposition of the Asmari and Gachsaran Formations. Telogentic processes caused dissolution and dedolomitization of the Shahbazan Formation due to exhumation. by the exception of dedolomitization and neomorphism, other diagenetic features are occurred in all studied sections.

Keywords

• The Shahbazan Formation
• Diagenesis
• Lurestan zone
• Eocene

20.1001.1.10237429.1397.28.109.9.7

Main Subjects

• Sedimentology