Coevolution of diagenetic fronts and fluid‑fracture pathways

Koeshidayatullah, A., Al‑Sinawi, N., Swart, P. K., Boyce, A. , Redfern, J. and Hollis, C. (2022) Coevolution of diagenetic fronts and fluid‑fracture pathways. Scientific Reports, 12, 9278. (doi: 10.1038/s41598-022-13186-1) (PMID:35661773) (PMCID:PMC9166768)

Abstract

Diagenetic boundaries are paleo-reaction fronts, which have the potential to archive the termination of metasomatic processes in sedimentary rocks. They have not been extensively studied, perhaps because they appear simple in outcrop. Recent work has demonstrated the significance of paleo-reaction fronts to decipher multiphase recrystallization processes and provide high porosity zones. This paper provides a detailed documentation of reaction front evolution in a tectonically active salt basin and reveals a high level of complexity, associated with multiple fluid flow and tectonic events. Here, consistent patterns of increasing dolomite stoichiometry and ordering, along with a change from seawater-derived, fabric-retentive dolomite to fracture-controlled, fabric-destructive hydrothermal dolomite are observed vertically across the stratabound dolomite bodies. These patterns, coupled with a decrease in porosity, increase in ∆47 temperature and δ18Owater values indicate multiphase recrystallization and stabilization by warm, Mg-rich fluids. The stratabound dolomite bodies apparently terminated at a fracture-bound contact, but the presence of dolomite fragments within the fracture corridor suggests that fracturing post-dated the first dolomitization event. The termination of dolomite formation is therefore interpreted to be associated with a decrease in the capacity of the magnesium-rich fluids to dolomitize the rock, as indicated by the presence of non-stoichiometric and poorly ordered dolomite at the reaction fronts. The fracture corridors are interpreted to exploit dolostone-limestone boundaries, forming prior to a later, higher temperature, hydrothermal dolomitization event, which coincided with the formation and growth of the anticline. Karstification subsequently exploited these fracture corridors, widening fractures and leading to localized collapse and brecciation. The results demonstrate that an apparently simple reaction front can have a complex history, governed by the inheritance of prior diagenetic events. These events modified rock properties in such a way that fluid flow was repeatedly focused along the original dolomite-limestone boundary, overprinting much of its original signature. These findings have implications to the prediction of structurally controlled diagenetic processes and the exploration of naturally fractured carbonate reservoirs for energy exploration globally.

• Item Type: Articles
• Additional Information: Support from the University of Manchester through Presidential Doctoral Award scheme has greatly benefited the research. Further support from IAS and AAPG postgraduate grants to A.K are acknowledged. All authors would also like to thank Petroleum Development Oman and the NARG (North Africa Research Group) sponsors.
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Boyce, Professor Adrian

Creator Roles

Boyce, A.: Formal analysis, Writing – review and editing

• Authors: Koeshidayatullah, A., Al‑Sinawi, N., Swart, P. K., Boyce, A., Redfern, J., and Hollis, C.
• College/School: College of Science and Engineering > Scottish Universities Environmental Research Centre
• Journal Name: Scientific Reports
• Publisher: Nature Research
• ISSN: 2045-2322
• ISSN (Online): 2045-2322
• Copyright Holders: Copyright © 2022 The Authors
• First Published: First published in Scientific Reports 12: 9278
• Publisher Policy: Reproduced under a Creative Commons License