Investigating water-to-rock exchanges (W/R) in carbonate system Using Petrographic and Elemental Geochemistry Evidence (An example of the Asmari Formation, Southwestern Lorestan)

Authors

1 Department of Petroleum Engineering, Mining and Geology, Ma.C., Islamic Azad University, Mashhad, Iran

2 M. Sc. Student, Department of Petroleum Engineering, Mashhad Branch, Islamic Azad University, Mashhad, Iran

3 National Iranian Drilling Company

Abstract

This study utilized textural and elemental geochemical analyses to investigate diagenetic processes, paragenetic sequences, and the dolomitization model of the Asmari Formation deposits. The studied section, with a thickness of 106 meters, consists of carbonate-dolomitic units, from which 106 thin sections were prepared for petrographic analysis. Twelve dolomite samples were analyzed for elemental composition using EDX to determine the dolomitization model of the formation. Petrographic studies identified several diagenetic processes including micritization, neomorphism, cementation, compaction, dissolution, and replacement, ultimately establishing the diagenetic model and paragenetic sequences. Based on petrological evidence, the paragenetic sequence of the Asmari Formation deposits in the Qawar Anticline section was interpreted in four environments: marine, burial, uplift, and freshwater. These processes occurred during three diagenetic stages: early (eogenesis), middle (mesogenesis), and late (telogenesis). The most significant diagenetic process in the studied section was dolomitization, which has converted a major portion of the Asmari Formation's carbonate sequences into dolomite. Two groups of dolomites were identified based on textural and elemental geochemical studies: primary dolomites (with low Fe and Mn concentrations and high Mg and Sr concentrations) and secondary dolomites (with high Fe and Mn concentrations and low Mg and Sr concentrations). The primary dolomites are of sedimentary origin and related to the tidal zone, while the secondary dolomites are of diagenetic origin and associated with shallow-to-intermediate burial diagenetic environments.

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History

  • Receive Date: 25 August 2025
  • Revise Date: 18 October 2025
  • Accept Date: 25 October 2025

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