The role of fault structures in accomodation and separation of mineral veins in the Zizgan and Amre mines, southeast of Tafarsh

Document Type : Research Article

Authors

Somayyeh Oroji ¹

Ali Yassaghi ²

¹ M.Sc. student, Department of Tectonic Geology, Faculty of Basic Sciences, Tarbiat Modares University, Tehran, Iran

² Professor, Department of Geology, Faculty of Basic Sciences, Tarbiat Modares University, Tehran, Iran

10.22067/econg.2025.1143

Abstract

Interpretive study of geological structures is one of the main pillars of exploration operations of mineral deposits. Considering the spatial relationship of vein mineralizations with fault zones, this study has been conducted to investigate such a relationship in the Zizgan and Amreh mining areas located in the Urmia-Dokhtar volcanic belt. Faults in this belt play an important role as the accommodation controller of mineralization as well as the displacement of mineral veins. The metallic and non-metallic mineralization identified in these mines is mainly lead metallic minerals as veins in tuff, andesite, and andesite-basaltic tuff rock units of the Eocene. Field investigation of the spatial relationship of mineralization and fault structures showed that the mineral veins were mainly injected and emplaced under the influence of dextral faulting. These faults and veins have been cut and displaced by younger sinistral faults. These results indicate that in the Zizgan and Amreh mines, dextral and sinistral faults play a significant role in the placement and displacement of mineral veins, respectively.
 
Introduction
Igneous activity in the Urmia-Dokhtar volcanic belt, due to the subduction of the Young Tethys oceanic plate beneath central Iran, began in the Paleocene and reached its peak during the Eocene (Stöcklin, 1968). These activities have been associated with the formation of metal and non-metal deposits in central Iran (Kazemi et al., 2019). Zizgan and Amreh Mines, under investigation in this study, are located in this belt. The accommodation of metallic and non-metallic ores within fault zones indicates the importance of structural studies in mineral exploration in these mines. Spatial relationship of faults with veins, which can control both accommodation and displacement of veins, shows that mineralization in these mines is of veins and often fills fractures and faults (Hosseini and Asghari, 2019). This study aims to perform geometrical and kinetic analyses of faults in the Zizgan and Amreh mines, as well as to find their spatial and temporal relationship with mineral veins.
 
Material and methods
In order to analyze the relationship between fault structures and vein mineralization in the studied mines, interpretation of satellite images and field mapping has been carried out to identify the relation between fault structures and mineral veins, as well as measuring their location and spatial relationship.
 
The host rock for mineralization in Amreh and Zizgan mines is located in tuff and andesitic tuff of unit E_5 of Eocene rock units. This mineralization, which has mainly taken place along existing faults and fractures, includes numerous veins of barite, so galena and lead are located inside a waste of barite. The veins under investigation in this study are in line with the general trend of northeast and southeast faults. Examples of this correlation between faults and the main veins of Zizgan Mine include vein 2 with the FL5 fault and vein 4 with the FR6 fault. Most of these faults, which are parallel to the veins, have a dextral mechanism. Sinisteral faults, however, have cut and displaced mineral veins and also some dextral faults. Examples of these vein-cutting faults are the interruption and displacement of veins 1 and 3 of Zizgan mine by FL2 and FL10 faults, respectively. Therefore, from the point of view of the relationship between faults and mineral veins, the faults are classified into two categories: host mineralization with a dominant dextral fault mechanism and sinistral fault mechanisms that cut and displace mineralized veins with a dominant left-lateral separation. Such a connection of vein with sinistral faults indicates the young activity of these faults in the Urmia Dokhtar belt. This interpretation can be used as a standard in the exploration of this vein in the mines of the study area and the belt.
 
Disscusion
Strike-slip faults, as the main structures controlling the accommodation of veins, have two different dextral and sinistral mechanisms. The dextral faults have been cut and displaced by sinistral faults. Some sinistral faults have been cut and displaced by other sinistral faults. Therefore, these faults are younger than the dextral ones. An example of this is the displacement of the FL17 fault by the FL16 fault (Figure 1). Therefore, sinistral faults are younger than dextral ones. The dominant azimuth of strike of the sinistral faults is consistent with the trend of the Tafaresh and Kushek-Nusrat faults as the main fault zones in the Urmia Dokhtar belt (Khodaparast et al., 2024). There is much recorded evidence on changing the mechanism of faults from dextral to sinistral in the Urmia Dokhtar zone. The most important of which is the Kushek Nusrat fault zone, which is located in the northeast of the study area (Figure 2). The presented evidence on the relationship between veins and faults in the region shows that their trends are dominantly consistent (Figure 12C).  Therefore, these mineralized veins have been accommodated as hydrothermal veins in fault zones. In addition, the changes in the thickness of the veins and their disruption by layering indicate that mineralization in this area is not simultaneous with sedimentation.

Keywords

Faults hosting mineral veins

Strike-slip faults

Zizgan and Amreh mines

Urmia-Dokhtar belt

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References

Blenkinsop, T.G., Oliver, N.H.S., Dirks, P.G.H.M., Nugus, M., Tripp, G. and Sanislav, I., 2020. Structural Geology Applied to the Evaluation of Hydrothermal Gold Deposits. In: J.V. Rowland and D.A. Rhys (Editors), Appled structural geology of ore-forming hudrothermal systems, Society of Economic Geologists, V. 21, pp. 1–23. https://doi.org/10.5382/rev.21.01

Fossen, H., 2010. Extensional tectonics in the North Atlantic Caledonides: a regional view. In: D.L. Law, R.W.H. Butler, R.E. Holdsworth, M. Krabbendam and R.A. Strachan (Editor), Continental Tectonics and Mountain Building: The Legacy of Peach and Horne, Geological Society, Londan, Special Publication, V. 335. https://doi.org/10.1144/SP335.31

 Hadjian, H., 1970. Geological map of Tafresh, scale1:100.000, Geological Survey of Iran. 

Johri, M.D., Zoback, M. and Hennings, P., 2014. A scaling law to characterize fault-damage zones at reservoir depths. AAPG Bulletin, 98(10)‌: 2057–2079. https://doi.org/10.1306/05061413173

Haddadpour, A., Mohammadi, R. and Golzar, H., 2012. Petrography, geochemistry and lead mineralization in the Hezarabad (Ashtian) region. Journal of Environmental Geology, 6(20): 49–63. Retrived November 10, 2025 from https://sanad.iau.ir/en/Article/931402

Hashemi, F., 2015. Mineralogy, geochemistry and genesis of the Varandan Ba- Pb- Cu deposit in the Urumieh-Dokhtar Zone, South of Kashan. M.Sc. Thesis, Shahrood University of Technology, Faculty of Earth Sciences, Shahrood, Iran,  251 pp. Retrived November 10, 2025 from https://shahroodut.ac.ir/en/thesis/thesis.php?thid=QE247

Hosseini, S.A. and Asghari, O., 2019. Multivariate geostatistical simulation on block-support in the presence of complex multivariate relationships: iron ore deposit case study. Natural Resources Research, 28(1): 125–144. https://doi.org/10.1007/s11053-018-9379-2

Kazemi, K., Kananian, A., Xiao, Y. and Sarjoughian, F., 2019. Petrogenesis of Middle-Eocene granitoids and their Mafic microgranular enclaves in central Urmia-Dokhtar Magmatic Arc (Iran): Evidence for interaction between felsic and mafic magmas. Geoscience Frontiers, 10(2): 705–723. https://doi.org/10.1016/j.gsf.2018.04.006

Khodaparast, S., Madanipour, S., Enkelmann, E., Hessami, K. and Nozaem, R., 2024. Time constraints on the late Cenozoic fault evolution along the northern margin of the Iranian Plateau in the Arabia‐Eurasia collision zone. Tectonics, 43(8): e2023TC008034.  https://doi.org/10.1029/2023TC008034

Micklethwaite, S., Ford, A., Witt, W. and Sheldon, H.A., 2015. The where and how of faults, fluids and permeability – insights from fault stepovers, scaling properties and gold mineralization. Geofluids, 15: 240–251. https://doi.org/10.1111/gfl.12102

Pezeshki Gharache, F., Mousivand, F., Rezaei-Kahkhaei, M. and Fardoost, F., 2021. Ore facies, mineralogy, alteration, geochemistry and genesis of the Vanakan (Sokan) barite-zinc-lead-copper deposit, north east of Semnan. Journal of Economic Geology, 13(1): 29–55. (in Persian with English abstrac) https://doi.org/10.22067/econg.v13i1.82657

Stöcklin, J., 1968. Structural history and tectonics of Iran: a review. AAPG bulletin, 52(7): 1229–1258.  https://doi.org/10.1306/5D25C4A5-16C1-11D7-8645000102C1865D

Sheykholeslami, M.R., Javadi, H.R. and Asadi, M., 2013. Iran Fault Map on Provincial Subdivisions. Geological Survey & Mineral Explorations of Iran (GSI), Tehran, Iran.

Yildırım, E., Yildırım, N., Dönmez, C. and Günay, K., 2021. Geology of the Yeşilyurt gold deposit: an example of low-angle normal fault related mineralization, Eastern Anatolia-Turkey. Bulletin of the Mineral Research and Exploration, 164: 261–279. https://doi.org/10.19111/bulletinofmre.797729