3D Sparse norm inversion of gravity and magnetic data: A case study of Gol-e-Gohar mine in Iran

Document Type : Research Paper

Authors

1 School of Mining Engineering, Faculty of Engineering, University of Tehran, Iran.

2 Institute of Geophysics, University of Tehran, Iran.

10.22059/ijmge.2024.377009.595168

Abstract

This study employs a constrained mixed Lp norm inversion to assess the efficacy of geophysical potential field methods in delineating high-grade iron mineralization zones within the Gol-e-Gohar No. 2 deposit, located in the Sanandaj-Sirjan zone of southwest Iran. Given the considerable density and susceptibility contrast between iron ore, particularly the massive Kiruna-type magnetite ± apatite mineralization, and the surrounding metamorphic host rocks, extensive ground-based gravity and magnetic data were collected across a survey area spanning 1600m × 900m.  To validate the effectiveness of the sparse norm inversion algorithm, two synthetic models were initially evaluated. These models included a dipping prism and two vertical prisms. Subsequently, after essential gravity and magnetic data corrections, the algorithm was applied to the acquired field data. The accurately recovered models obtained through the iterative inversion process were visually presented through four cross-sections covering the primary anomalous region, revealing a robust spatial correlation between high-density contrast and high-magnetization zones. Further development of 3D reconstructed models for density contrast and magnetic susceptibility demonstrated significant consistency with geological data obtained from exploratory boreholes, effectively delineating three distinct mineralization zones with vertical expansions ranging from 100 to 300 meters. These zones were characterized by magnetized regions enclosed within the dense rock formations.

Keywords

Main Subjects

References

[1] Nabatian, Gh., Rastad, E., Neubauer, F., Honarmand, M., & Ghaderi, M. (2015). Iron and Fe–Mn mineralisation in Iran: implications for Tethyan metallogeny. Australian Journal of Earth Sciences, 62(2), 211–241. https://doi.org/10.1080/08120099.2015.1002001.
[2] Bialas, T., Bohlen, T., Dannowski, A., Eisenberg-Klein, G., Gassner, L., Gehrmann, R., Heeschen, K., Hölz, S., Jegen, M., Klaucke, I., Krieger, M., Mann, J., Müller, Ch., Prüßmann, J., Schicks, J., Schünemann, E., Schwalenberg, K., Sommer, M., Smilde, P. L., Spangenberg, E., Trappe, H., & Zander, T. (2020). Joint interpretation of geophysical field experiments in the Danube deep-sea fan, Black Sea. Marine and Petroleum Geology, 121, 104551. https://doi.org/10.1016/j.marpetgeo.2020.104551.
[3] Nappi, R., Paoletti, V., D’Antonio, D., Soldovieri, F., Capozzoli, L., Ludeno, G., Porfido, S., & Michetti, A. M. (2021). Joint interpretation of geophysical results and geological observations for detecting buried active faults: The case of the “Il Lago” plain (Pettoranello del Molise, Italy). Remote Sensing, 13(8), 1555. https://doi.org/10.3390/rs13081555.
[4] Marzan, I., Martí, D., Lobo, A., Alcalde, J., Ruiz, M., Alvarez-Marron, J., & Carbonell, R. (2021). Joint interpretation of geophysical data: Applying machine learning to the modeling of an evaporitic sequence in Villar de Cañas (Spain). Engineering Geology, 288, 106126. https://doi.org/10.1016/j.enggeo.2021.106126.
[5] Milano, M., Varfinezhad, R., Bizhani, H., Moghadasi, M., Nejati Kalateh, A., & Baghzendani, H. (2021). Joint interpretation of magnetic and gravity data at the Golgohar mine in Iran. Journal of Applied Geophysics, 195, 104476. https://doi.org/10.1016/j.jappgeo.2021.104476.
[6] Afshar, A., Norouzi, G.-H., Moradzadeh, A., & Riahi, M.-A. (2018). Application of magnetic and gravity methods to the exploration of sodium sulfate deposits: Case study: Garmab mine, Semnan, Iran. Journal of Applied Geophysics, 159, 586-596. https://doi.org/10.1016/j.jappgeo.2018.10.003.
[7] Gonçalves, M. M., & Leite, E. P. (2019). Cooperative inversion of seismic reflection and gravity data: An object-based approach. Journal of Applied Geophysics, 167, 42-50. https://doi.org/10.1016/j.jappgeo.2019.05.006.
[8] Zhdanov, M.S., Tu, X. and Čuma, M. (2022), Cooperative inversion of multiphysics data using joint minimum entropy constraints. Near Surface Geophysics, 20: 623-636. https://doi.org/10.1002/nsg.12203.
[9] Abedi, M. (2022). Cooperative fuzzy-guided focused inversion for unstructured mesh modeling of potential field geophysics: A case study for imaging an oil-trapping structure. Acta Geophysica, 70, 2077–2098. https://doi.org/10.1007/s11600-022-00857-w.
[10] Hu, Y., Wei, X., Wu, X., Sun, J., Huang, Y., & Chen, J. (2024). Three-dimensional cooperative inversion of airborne magnetic and gravity gradient data using deep-learning techniques. GEOPHYSICS, 89(WB67-WB79). https://doi.org/10.1190/geo2023-0225.1.
[11] Gallardo, L. A., & Meju, M. A. (2007). Joint two-dimensional cross-gradient imaging of magnetotelluric and seismic traveltime data for structural and lithological classification. Geophysical Journal International, 169(3), 1261–1272. https://doi.org/10.1111/j.1365-246X.2007.03366.x.
[12] Fregoso, E., & Gallardo, L. A. (2009). Cross-gradients joint 3D inversion with applications to gravity and magnetic data. GEOPHYSICS, 74, L31-L42. https://doi.org/10.1190/1.3119263.
[13] Miotti, F., Zerilli, A., Menezes, P. T. L., Crepaldi, J. L. S., & Viana, A. R. (2018). A new petrophysical joint inversion workflow: Advancing on reservoir’s characterization challenges. Interpretation, 6, SG33-SG39. https://doi.org/10.1190/INT-2017-0225.1.
[14] Astic, T., & Oldenburg, D. W. (2019). A framework for petrophysically and geologically guided geophysical inversion using a dynamic Gaussian mixture model prior. Geophysical Journal International, 219(3), 1989–2012. https://doi.org/10.1093/gji/ggz389
 [15] Tavakoli, M., Nejati Kalateh, A., Rezaie, M., Gross, L., & Fedi, M. (2021). Sequential joint inversion of gravity and magnetic data via the cross-gradient constraint. Geophysical Prospecting, 69(8), 1542–1559. https://doi.org/10.1111/1365-2478.13120.
[16] Wang, K., & Yang, D. (2023). Joint inversion with petrophysical constraints using indicator functions and the extended alternating direction method of multipliers. GEOPHYSICS, 88, R49-R64. https://doi.org/10.1190/geo2022-0167.1.
[17] Fournier, D., Oldenburg, D., & Davis, K. (2016). Robust and flexible mixed-norm inversion. SEG Technical Program Expanded Abstracts, 2016, 1542-1547. https://doi.org/10.1190/segam2016-13821093.1.
[18] Fournier, D., & Oldenburg, D. W. (2019). Inversion using spatially variable mixed ℓp norms. Geophysical Journal International, 218(1), 268–282. https://doi.org/10.1093/gji/ggz156.
[19] Ardestani, V. E., Fournier, D., & Oldenburg, D. W. (2021). Correction to: Gravity and Magnetic Processing and Inversion Over the Mahallat Geothermal System Using Open Source Resources in Python. Pure and Applied Geophysics, 178, 3289. https://doi.org/10.1007/s00024-021-02805-z.
[20] Ghorbani, M. (2013). The Economic Geology of Iran. Springer Dordrecht. https://doi.org/10.1007/978-94-007-5625-0.
[21] Najmi, F., Malekzadeh Shafaroudi, A., Karimpour, M. H., & Poulson, S. R. (2023). The Bahariyeh iron oxide copper–gold deposit, Khaf-Khashmar-Bardaskan magmatic belt, NE Iran: Constraints from geochemical, fluid inclusions, and O-S isotope studies. Ore Geology Reviews, 159, 105501. https://doi.org/10.1016/j.oregeorev.2023.105501.
[22] Zaremotlagh, S., & Hezarkhani, A. (2016). A geochemical modeling to predict the different concentrations of REE and their hidden patterns using several supervised learning methods: Choghart iron deposit, bafq, Iran. Journal of Geochemical Exploration, 165, 35-48. https://doi.org/10.1016/j.gexplo.2016.02.001. Link to the article
[23] Ziapour, S., Esmaeily, D., Khoshnoodi, K., Niroomand, S., & Simon, A. C. (2021). Mineralogy, geochemistry, and genesis of the Chahgaz (XIVA Anomaly) Kiruna-type iron oxide-apatite (IOA) deposit, Bafq district, Central Iran. Ore Geology Reviews, 128, 103924. https://doi.org/10.1016/j.oregeorev.2020.103924.
[24] Alibabaie, N., Esmaeily, D., Peters, S. T. M., Horn, I., Gerdes, A., Nirooamand, S., Jian, W., Mansouri, T., Tudeshki, H., & Lehmann, B. (2020). Evolution of the Kiruna-type Gol-e-Gohar iron ore district, Sanandaj-Sirjan zone, Iran. Ore Geology Reviews, 127, 103787. https://doi.org/10.1016/j.oregeorev.2020.103787.
[25] Ansari, A., Ghari, H., Alamdar, K., & Moradi, S. (2016). Investigation of the relationship between upward continued potential fields and depth of the causative bodies: A case study from Gol-Gohar Iron ore mine. Iranian Journal of Geophysics, 5(4), 1-12.
[26] Behnam, S., & Ramazi, H. (2019). Interpretation of geomagnetic data using power spectrum and 3D modeling of Gol-e-Gohar magnetic anomaly. Journal of Applied Geophysics, 171, 103829. https://doi.org/10.1016/j.jappgeo.2019.103829.
[27] Bizhani, H., Mansour Shoar, P., & Moghadasi, M. (2023). 2D Inversion of magnetic and gravity data: a case study on Golgohar mine. International Journal of Mining and Geo-Engineering, 57(1), 41-46. doi: 10.22059/ijmge.2022.342045.594969.
[28] Liu, S., Hu, X., Zhang, H., et al. (2017). 3D Magnetization Vector Inversion of Magnetic Data: Improving and Comparing Methods. Pure and Applied Geophysics, 174, 4421–4444. https://doi.org/10.1007/s00024-017-1654-3.
[29] Shi, X., Geng, H., & Liu, S. (2022). Magnetization Vector Inversion Based on Amplitude and Gradient Constraints. Remote Sensing, 14(21), 5497. https://doi.org/10.3390/rs14215497.
[30] Cockett, R., Kang, S., Heagy, L. J., Pidlisecky, A., & Oldenburg, D. W. (2015). SimPEG: An open source framework for simulation and gradient based parameter estimation in geophysical applications. Computers & Geosciences, 85(Part A), 142-154. https://doi.org/10.1016/j.cageo.2015.09.015.
[31] Zhdanov, M. S. (2015). Inverse theory and applications in geophysics (2nd ed.). Elsevier Science. https://doi.org/10.1016/C2012-0-03334-0.
[32] Nagy, D. (1966). The Gravitational Attraction of a Right Rectangular Prism. GEOPHYSICS, 31, 362-371. https://doi.org/10.1190/1.1439779.[33] Fournier, D. (2019) Advanced potential field data inversion with Lp-norm regularization. PhD Thesis, The University of British Columbia.
[34] Plouff, D. (1976). Gravity and magnetic fields of polygonal prisms and application to magnetic terrain corrections. Geophysics, 41, 727-741.
[35] Sharma, P.V. (1966). Rapid computation of magnetic anomalies and demagnetization effects caused by bodies of arbitrary shape. Pure and Applied Geophysics, 64, 89-109.
[36] Li, Y., & Oldenburg, D.W. (1996). 3-D Inversion of Magnetic Data. Geophysics, 61, 394-408. http://dx.doi.org/10.1190/1.1443968.
[37] Li, Y., & Oldenburg, D. W. (1998). 3-D inversion of gravity data. Geophysics, 63(1), 109-119. http://dx.doi.org/10.1190/1.1444302
[38] Oldenburg, D. W. and Li, Y. (2005) Inversion for applied geophysics: A tutorial. Near-surface geophysics: Society of Exploration Geophysicists, 89-150.
[39] Rezayee, M. H., Khalaj, M., & Mizunaga, H. (2023). Structural analysis and susceptibility inversion based on ground magnetic data to map the chromite mineral resources: A case study of the Koh Safi Chromite Ore Deposit, Parwan, Afghanistan. Geoscience Letters, 10, 43. https://doi.org/10.1186/s40562-023-00298-3.
[40] Alibabaie, N., Esmaeily, D., Peters, S. T. M., Horn, I., Gerdes, A., Nirooamand, S., Jian, W., Mansouri, T., Tudeshki, H., & Lehmann, B. (2020). Evolution of the Kiruna-type Gol-e-Gohar iron ore district, Sanandaj-Sirjan zone, Iran. Ore Geology Reviews, 127, 103787. https://doi.org/10.1016/j.oregeorev.2020.103787.
[41] Berberian, M., & King, G. (1981). Towards a paleogeography and tectonic evolution of Iran. Canadian Journal of Earth Sciences, 18(2), 210-265. https://doi.org/10.1139/e81-019.
[42] Babaki, A., & Aftabi, A. (2006). Investigation on the model of iron mineralization at Gol Gohar iron deposit, Sirjan-Kerman. Geosciences, 16 (61), 40-59. SID. https://sid.ir/paper/31412/en
 [43] Badavi, M., Atapour, H., & Mohammadi, M. (2019). Mineralogy, petrography, geochemistry of magnetite ore and sulfide minerals and the possible model of mineralization at Anomaly 3, Gol-e-Gohar, iron mine, Sirjan (Kerman). Petrology, 38, 49–79. (In Persian with English Abstract).
[44] Bayati-Rad, Y., Mirnejad, H., & Ghalamghash, J. (2013). Distribution and abundance of rare earth elements in magnetite from Gol-Gohar iron ore deposit, Sirjan-Kerman. Scientific Quarterly Journal of Geosciences, 23(90), 217–224.
[45] Iran Minerals Production and Supply Company (IMPASCO). (2017). Mineral reserve estimation report for Gol Gohar Sirjan, mine 2.
[46] Beltrão, J. F., Silva, J. B. C., & Costa, J. C. (1991). Robust polynomial fitting method for regional gravity estimation. GEOPHYSICS, 56, 80-89. https://doi.org/10.1190/1.1442960.
International Journal of Mining and Geo-Engineering
Volume 58, Issue 4
December 2024
Pages 411-422

Files

Share

How to cite

Statistics