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

Articles in Press

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

10.22084/nfag.2025.31382.1687

Abstract

In order to investigate water-to-rock exchanges and subsequent to the diagenetic systems and the primary mineralogy of the carbonate units of the Asmari Formation, a 131-meter-thick surface stratigraphic section located in the Rit anticline (southwestern Lorestan) was selected and sampled. The lithology of this formation comprises alternating layers of carbonate and dolomitic carbonate rocks. In this study, 23 samples were analyzed using elemental EDX analysis to determine the major and trace element composition and interpret the diagenetic systems and original mineralogy. Elemental geochemical evidence indicates that the studied samples fall within the compositional range of aragonitic limestones from Gordon, Tasmania, and aragonitic carbonates of the Mozduran Formation. This supports the interpretation that the original mineralogy of the Asmari limestones in the studied section was aragonitic. Plotting Sr/Ca ratios against Mn contents reveals a predominantly closed to slightly open diagenetic system, characterized by weak water–rock interaction (W/R), for the Asmari carbonates in the Rit anticline section. The presence of primary aragonitic mineralogy, the lack of significant discontinuities, the prevailing climatic conditions, and intrinsic rock properties such as permeability, original mineralogy, and diagenetic potential appear to have played key roles in controlling the water-to-rock ratio. These factors contributed to the limited impact of meteoric diagenesis in the upper part of the sequence, as evidenced by the scarcity of meteoric cement and the partial dissolution of bioclasts in the studied samples. Thus, it can be concluded that the diagenetic system within the carbonate succession of the Asmari Formation at the Rit anticline is dominantly closed, becoming weakly open towards the top of the sequence.

Keywords

New Findings in Applied Geology

Articles in Press, Accepted Manuscript
Available Online from 16 September 2025

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History

  • Receive Date: 05 July 2025
  • Revise Date: 15 August 2025
  • Accept Date: 16 September 2025

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