Petrography and origin of dolomites of Shahbazan Formation (middle to upper Eocene) in east Eslamabade - Gharb (Kermanshah)

Main goal of this study is to reveal the petrography and origin of dolomites in Shahbazan Formation in the east of Eslamabade- Gharb. An outcrop was sampled in study area and 49 samples were collected. Two types of dolomites were identified, type I with xenotopic texture of clear dolomite crystals, type II with idiotopic texture of filthy (blurry) dolomite crystals. Type I is anhedral to subhedral, very fine-to fine-crystals (5–16 μm crystal size, dolomicrite); type II is subhedral to euhedral, and fine-to medium-crystals (16–62 μm crystal size,dolomicrosparite). According to size and shape we concluded these dolomites formed during early diagenesis, however, type II dolomites were probably recrystallized during later diagenesis and their crystal size are increased up to 220 μm. We suggest these dolomites were formed due to basinward flushing of meteoric fluids during sea-level fall in a humid climatic regime. Mixing of meteoric and marine fluids promoted dolomitization of limestones theShahbazan Formation in mixing zone. Consequently, some porosities were occluded by later calcite precipitation.