Diagenetic evolution and geochemical controls on carbonate platform development in the Middle Eocene Jahrum Formation, Zagros Basin

The Jahrum Formation constitutes one of the most extensive middle Eocene shallow‐marine carbonate successions of the Zagros Basin and preserves an exceptional record of carbonate diagenesis associated with the evolution of the eastern Neo‐Tethyan platform. Although previous investigations have documented its lithostratigraphy and larger benthic foraminiferal assemblages, the diagenetic pathways responsible for modifying its primary mineralogical, petrographic and geochemical characteristics remain insufficiently constrained. This study integrates petrographic observations, X‐ray diffraction (XRD), cathodoluminescence (CL), scanning electron microscopy coupled with energy‐dispersive spectroscopy (SEM–EDS), stable carbon and oxygen isotope analyses and pyrite framboid characterisation to reconstruct the diagenetic evolution of the Jahrum Formation in the Lapoie and Kelestan sections of the Zagros Basin. Petrographic observations reveal multiple generations of carbonate cementation, pervasive dolomitisation, recrystallisation of skeletal grains, dissolution and late‐stage meteoric alteration. Mineralogical and geochemical analyses demonstrate systematic variations in carbonate mineralogy and isotopic composition associated with successive diagenetic environments. SEM–EDS analyses confirm the occurrence of framboidal pyrite within micritic matrices, whereas pyrite morphology and elemental composition indicate formation under dysoxic to locally anoxic early diagenetic conditions. Stable isotope compositions further suggest progressive modification of primary marine signatures during burial diagenesis and subsequent meteoric fluid interaction. Integration of petrographic, mineralogical and geochemical evidence enables reconstruction of a comprehensive paragenetic sequence linking depositional environments with post‐depositional alteration of the carbonate platform. The resulting diagenetic model provides new insights into the evolution of Eocene carbonate systems within the eastern Neo‐Tethys and establishes a robust framework for interpreting diagenetic processes affecting shallow‐marine carbonate successions throughout the Zagros Basin.