Abstract
The Ghare-Aghaj potash resource is one of the largest halokinetic-type potash-bearing salt deposits in the northern part of the central Iran zone, within the Zanjan Province. This near-surface deposit originates in a sedimentary environment rich in siliciclastic sediments during the relaxation phase between tectonic activities. To explore such massive evaporates, because of their low density contrast compared to the surrounding rocks, a ground-based gravity survey proves to be an ideal strategy. In this study, we use a mixed Lp–Lq norm regularization in a constrained inversion process to generate compact and smooth models in three dimensions. This approach leads to the accurate detection of deposit boundaries and also localizes the prospect zone. First, we employ this method in a synthetic case, representing a simple vertical prism shape resembling evaporates' general geometry, such as salt domes and potash mineralization. This assessment examines how well it can recover these geometric structures with lower density contrast at varying depths. Subsequently, we apply this method in a real-case scenario. The findings detect potash mineralization within a salt wall structure at about 10–20 m below the surface, considering the challenging topographical conditions. Smooth reconstructed models, while accurately recovering the background properties, fail to recover the boundaries of the target ore. Conversely, blocky reconstructed models sharply recover the geometry of the potash mineralization but with less precision in the recovery of the background properties. The inversion results illustrate a salt dome within an anticline, showing a vertical expansion of around 110 m and a lateral expansion of 160 m. These results are in good concordance with the well data, indicating a salt distribution with a vertical expansion ranging from 11 to 115 m below the surface.
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Data availability
Data are available upon reasonable request to the corresponding author via the email address maysamabedi@ut.ac.ir.
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Acknowledgements
We would like to express our sincere thanks to the School of Mining Engineering, University of Tehran, for all their support. We also express our gratitude to the faculty members of the Institute of Geophysics, University of Tehran for their invaluable guidance in the field of inverse problems. Finally, we extend our sincere appreciation to Professor Karst LaMoreaux, Editor of Carbonates and Evaporites, and the reviewers for their meticulous review of our manuscript. Their constructive comments and suggestions indeed helped us to improve the quality of the work.
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The final manuscript was a collaborative effort, with all authors contributing to the discussion of results. Bardiya Sadraeifar took responsibility of the coding process, wrote the manuscript text, and created the majority of the geophysical plots. Maysam Abedi played a guiding role in the research, providing data, geological descriptions and checked the whole manuscript.
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Sadraeifar, B., Abedi, M. 3D inversion of gravity data using mixed Lp–Lq norm regularization, a case study for potash targeting at the Ghare-Aghaj deposit in Iran. Carbonates Evaporites 39, 66 (2024). https://doi.org/10.1007/s13146-024-00978-x
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DOI: https://doi.org/10.1007/s13146-024-00978-x