Geology, mineralization, geochemistry, and fluid inclusion characteristics of the Bagh Khoshk copper deposit, Sirjan, southeast Iran

Document Type : Original Article


Petrology and Economic Geology Department, Faculty of Earth Sciences, Shahrood University of Technology, Shahrood, Iran


Bagh Khoshk deposit is located 35 km northeast of Sirjan in the southern Urmia- Dokhtar magmatic belt (Kerman metallogenic area). The magmatic activities and copper mineralization in this belt are attributed to the Eocene-Oligocene, middle-late Oligocene, and middle-late Miocene. Meanwhile, fertile porphyry copper deposits are genetically associated with middle-late Miocene granitoids (adakitic intrusive rocks). In Kerman metallogenic area, intrusive rocks are divided into productive with Miocene age (Kuh-Panj type) and semi-productive to barren groups with Eocene-Oligocene age (Jebal Barez type). Bagh Khoshk copper deposit has not been studied in terms of mineralization and genesis. In addition, it is not clear whether the Bagh Khoshk granitoid intrusion is a productive or semi-productive to barren magmatic system in the Kerman region. In this research, Bagh Khoshk deposit has been studied from the perspective of lithology, alteration, geochemistry, mineralization and fluid inclusion and by determining the geochemical nature of Bagh Khoshk granitoids, the origin of copper mineralization has been investigated.
Materials and methods
In this research, the number of 21 samples from the outcrops and 24 samples of drilling cores have been selected for petrographic and mineralogical studies. 13 unaltered to less altered rock samples were taken from the outcrops and drilling cores for petrological studies and analyzed using XRF and ICP-OES/MS methods for major and trace elements. Ore geochemistry study has been done on 491 rock samples from drilling cores. To study the fluid inclusion, 4 mineralized samples were selected from the potassic and phyllic alteration zones and after preparation of double polished sections, micro-thermometry studies were done on quartz crystals.
Results and discussion
The Eocene andesite to basaltic andesite lava flows and tuffs are the most widespread rock units in the Bagh Khoshk area. Late Miocene hypabyssal porphyry granodiorite and diorite stocks are intruded into the volcanic rocks. The alterations include potassic, prophylitic, phyllic, and argillic zones from the inside out. This deposit includes sulfide minerals (pyrite, chalcopyrite, bornite, molybdenite, chalcocite, and covellite), iron oxides (magnetite, olygiste, hematite, and goethite) and malachite which are mostly observed as disseminated and vein-veinlet forms in the potassic and phyllic zones. Copper is the major element, which has a positive correlation with molybdenum. Fluid inclusions in quartz crystals include LV, VL, and LVH types. The homogenization temperature of the LV, VL, and LVH fluid inclusions ranging from 180 to 289, 331 to 565, and 207 to 276 ⁰C. Their salinity varies from 0.35 to 10.24, 0.88 to 11.22, 33.55 to 42.66 wt.% NaCl eq., respectively. The Bagh Khoshk magmatic system in the Urmia-Dokhtar belt, was formed by partial melting of mantle source and thickening of lower crust, where the share of lower crust has been dominant. Finally, the Bagh Khoshk mineralization is a porphyry copper deposit, which is associated with adakitic and productive late Miocene magmas.
The late Miocene granodiorite intrusions host copper mineralization in the Bagh Khoshk area. These intrusions have the geochemical properties of adakitic magmas and are located in a normal continental arc environment. Enrichment in LREE, high Sr/Y and La/Yb ratios, enrichment in LILE and Sr, and depletion in HFSE are prominent geochemical features of Bagh Khoshk granitoids. Chalcopyrite is the most important copper-bearing mineral that is found as disseminated and vein- veinlets forms in the potassic and phyllic alteration zones. Based on fluid inclusion studies, the normal cooling of magmatic fluids and their mixing with meteoric waters has been one of the most important factors of metal deposition and the average depth of fluid inclusions entrapment and placement of the Bagh Khoshk porphyry stock is estimated at about 1200 m. The Bagh Khoshk magmatic system consists of partial melting of a mantle source with garnet amphibolite composition and a thickened lower crust, in which the share of lower crust has been dominant. The rapid rise of productive adakitic magma has led to the formation of economic copper deposit in this area.


Main Subjects

Persian References:
-Ghorbani, M., 2008. Economic Geology of Iranian Mineral Deposits and Signs, First Edition, Arian Zamin Publications, Tehran, 674 p.
-National Iranian Copper Industries Company, 2010. Report on geological studies and alteration of dry garden area on a scale of 1.1000, internal and unpublished report.
English References:
-Aghazadeh, M., Hou, Z., Badrzadeh, Z. and Zhou, L., 2015. Temporal–spatial distribution and tectonic setting of porphyry copper deposits in Iran: Constraints from zircon U–Pb and molybdenite Re–Os geochronology: Ore Geology Reviews, v. 70, p. 385-406.
-Alavi, M., 1994. Tectonics of the Zagros orogenic belt of Iran: new data and interpretations: Tectonophysics, v. 229, p. 211-238.
-Asadi, S., Moore, F. and Zarasvandi, A.R., 2014. Discriminating productive and barren porphyry copper deposits in the southeastern part of the central Iranian volcano-plutonic belt, Kerman region, Iran: A review. Earth Sciences Reviews, v. 138, p. 25-46.
-Barnes, H.L., 1997. Geochemistry of Hydrothermal Ore Deposits: John Wiley & Sons, New York, 972 p.
-Berberian, F. and Berberian, M., 1981. Tectono-plutonic episodes in Iran. In: Gupta, H.K., Delany, F.M. (Eds.), Zagroz–Hindu Kush–Himalaya Geodynamic Evolution: American Geophysical Union & Geological Society of America, Washington, p. 5-32.
-Bodnar, R.J., Lecumberri-Sanchez, P., Moncada, D. and Steele-MacInnis, M., 2014. Fluid Inclusions in hydrothermal ore deposits: In Holland H.D. and Turekian K.K. (eds.) Treatise on Geochemistry, Second Edition, Oxford, Elsevier, v. 13, p. 119-142.
-Brown, G.C., Thorpe, R. and Webb, P.C., 1984. The geochemical characteristics of granitoids in contrasting arcs and comments on magma sources: Journal of the Geological Society, v. 141, p. 413-426.
-Candela, P.A., 1991. Physics of aqueous phase evolution in plutonic environments: American Mineralogist (United States), v. 76(7-8), p. 1081-1091.
-Defant, M.J. and Drummond, M.S., 1993. Mount St. Helens: potential example of the partial melting of the subducted lithosphere in a volcanic arc: Geology, v. 21, p. 547-550.
-Defant, M.J. and Drummond, M.S., 1990. Derivation of some modern arc magmas by melting of the subducted lithosphere in a volcanic arc: Geology, v. 21, p. 547-550.
-Dimitrijevic, M.D., 1973. Geology of Kerman region: Geological Survey of Iran, v. 52, 334 p.
-Haas, J.L., 1971. The effect of salinity on the maximum thermal gradient of a hydrothermal system at hydrostatic pressure: Economic Geology, v. 66(6), p. 940-946.
-Han, Z.Z., Liu, H., Li, M., Sun, X.X., Lai, Z.Q., Bian, Y. and Lin, X.H., 2018. Mantle source features of the basalts and magma activity along the equatorial regions in the East Pacific Rise: Period Ocean University of China, v. 48, p. 63-75, (In Chinese with English Abstract).
-Hassanzadeh, J., 1993. Metallogenic and tectono-magmatic events in the SE sector of the Cenozoic active continental margin of Iran (Shahr e Babak area, Kerman province): Unpublished Ph.D. Thesis, University of California, Los Angeles, 204 p.
-Hofmann, A.W., Jochum, K.P., Seufert, M. and White, W.M., 1986. Nb and Pb in oceanic basalts: new constrains on mantle evolution: Earth and Planetary Science Letters, v. 79, p. 33-45.
-Hosseini, S.Z. and Arvin, M., 2020. Geochemistry and Sr-Nd Isotopes of the Oligo-Miocene Bagh-e-Khoshk Granitoid in SE of the UDMA, Iran: Implications for Petrogenesis and Geodynamic Setting: Journal of Sciences, Islamic Republic of Iran, v. 31(3), p. 245-257.
-Hou, Z.Q., Gao, Y.F., Qu, X.M., Rui, Z.Y. and Mo, X.X., 2004. Origin of adakitic intrusives generated during mid-Miocene east–west extension in southern Tibet: Earth and Planetary Science Letters, v. 220, p. 139-155.
-Irvine, T.N.J. and Baragar, W.R.A.F., 1971. A guide to the chemical classification of the common volcanic rocks: Canadian Journal of Earth Sciences, v. 8(5), p. 523-548.
-John, D.A., Ayuso, R.A., Barton, M.D., Blakely, R.J., Bondar, R.J., Dilles, J.H., Gray, F., Graybeal, F.T., Mars, J.C., McPhee, D.K., Seal, R.R., Taylor, R.D. and Vikre, P.G., 2010. Porphyry copper deposit Model, chapter B of mineral deposit models for resource assessment: Scientific Investigations Report 2010–5070–B.  U.S. Geological Survey, Reston, Virginia, 169 p.
-Lottermoser, B.G., 1992. Rare earth elements and hydrothermal ore formation processes: Ore Geology Reviews, v. 7(1), p. 25-41.
-Martin, H., Smithies, R.H., Rapp, R., Moyen, J. and Champion, D., 2005. An overiview of adakite, tonalite-trondhjemite-granodiorite (TTG), and sanukitoid—Relationships and some implications for crustal evolution: Lithos, v. 79, p. 1-24.
-McInnes, B.I.A., Evans, N.J., Fu, F.Q., Garwin, S., Belousova, E., Griffin, W.L., Bertens, A., Sukama, D., Permanadewi, S., Andrew, R.L. and Deckart, K., 2005. Thermal history analysis of selected Chilean, Indonesian, and Iranian porphyry Cu–Mo–Au deposits. In: Porter T.M. (Ed.), Super Porphyry Copper and Gold Deposits: A Global Perspective. PGC Publishing, Adelaide, p. 1-16.
-McInnes, B.I.A., Evans, N.J., Belousova, E. and Griffin, W.L., 2003. Porphyry copper deposits of the Kerman belt, Iran: timing of mineralization and exhumation processes: CSIRO Science Research Report, 41 p.
-Middlemost, E.A.K., 1994. Naming materials in the magma and igneous rock system: Science Reviews, v. 37, p. 215-224.
-Mohebi, A., Sepidbar, F., Mirnejad, H. and Behzadi, M., 2020. Molybdenite Re–Os dating, petrology, and geochemistry of granitoids in the Bondar Hanza porphyry Cu deposit (Urumieh-Dokhtar magmatic arc), Iran: Insight into petrogenesis, mineralization, and tectonic setting: Geological Journal, v. 55(11), p. 7499-7516.
-Nedimovic, R., 1973. Exploration for ore deposits in Kerman region. Geological Survey of Iran: v. 53, 247 p.
-Rapp, R.P. and Watson, E.B., 1995. Dehydration melting of metabasalt at 8–32 kbar: Implications for continental growth and crust-mantle recycling: Journal of Petrology, v. 36(4), p. 891-931.
-Reich, M., Parada, M.A., Palacios, C., Dietrich, A., Schultz, F. and Lehman, B., 2003. Adakite-like signature of late Miocene intrusions at the Los Pelambres giant porphyry copper deposit in the Andes of Central Chile—Metallogenic implications: Mineralium Deposita, v. 38, p. 876-885.
-Richards, J.P., Spell, T., Rameh, E., Razique, A. and Fletcher, T., 2012. High Sr/Y magmas reflect arc maturity, high magmatic water content, and porphyry Cu-Mo-Au potential: example from the Tethyan arcs of central and eastern Iran and western Pakistan: Economic Geology, v. 107(2), p. 295-332.
-Richards, J.P. and Kerrich, R., 2007. Adakite-like rocks: Their diverse origins and questionable role in metallogenesis: Economic Geology, v. 102, p. 537-576.
-Roedder, E., 1984. Fluid inclusion review in mineralogy: Mineralogical Society of America, Book Crafters, Inc., Chelsea, Michigan.
-Sajona, F.G., Maury, R.C., Prouteau, G., Cotton, J., Schiano, P., Bellon, H. and Fontaine, L., 2000. Slab melt as metasomatic agent in island arc magma mantle sources, Negros and Batan (Philippines): Island Arc, v. 9, p. 472-486.
-Shafiei, B., Haschke, M. and Shahabpour, J., 2009. Recycling of orogenic arc crust triggers porphyry Cu mineralization in Kerman Cenozoic arc rocks, southeastern Iran: Mineralium Deposita, v. 44, p. 265-283.
-Shahabpour, J., 2005. Tectonic evolution of the orogenic belt in the region located between Kerman and Neyriz: Journal of Asian Earth Sciences, v. 24, p. 405-417.
-Sillitoe, R.H., 2010. Porphyry Copper Systems: Society of Economic Geologists, Inc. Economic Geology, v. 105, p. 3-41.
-Sillitoe, R.H., 1997. Characteristics and controls of the largest porphyry copper-gold and epithermal gold deposits in the circum-Pacific region: Australian Journal of Earth Sciences, v. 44(3), p. 373-388.
-Simpson, M.P., Palinkas, S.S., Mauk, J.L. and Bondar, R.J., 2015. Fluid inclusion chemistry of adularia-sericite Au-Ag deposits of the Southern Hauraki goldfield, New Zealand: Economic Geology, v. 110, p. 763-786.
-Soheili, M., 1995. Geological quadrangle map of Sirjan, 1:250,000 series, No. I11, Geological Survey of Iran (GSI), Tehran.
-Stӧcklin, J., 1968. Structural history and tectonics of Iran: a review, American Association of Petroleum Geologists Bulletin, v. 52(7), p. 1229-1258.
-Taghipour, N., Aftabi, A. and Mathur, R., 2008. Geology and Re–Os geochronology of mineralization of the Miduk porphyry copper deposit: Resource Geology, v. 58 (2), p. 143-160.
-Thompson, R.N., 1982. Magmatism of the British Tertiary volcanic province: Scottish Journal of Geology, v. 18(1), p. 49-107.
-Waterman, G.C. and Hamilton, R.L., 1975. The Sar-Cheshmeh porphyry copper deposit: Economic Geology, v. 70, p. 568-576.
-Whitney, D.L. and Evans, B.W., 2010. Abbreviations for names of rock-forming minerals: American Mineralogist, v. 95, p. 185-187.
-Wilkinson, J.J., 2001. Fluid inclusions in hydrothermal ore deposits: Lithos, v. 55, p. 229-272.
-Yugoslavian Group, 1971. Geological quadrangle map of Pariz, 1:100,000 series, No. 7149, Geological Survey of Iran (GSI), Tehran.
-Zhang, Z.H., Mao, J.W., Wang, Y.B., Pirajno, F., Liu, J.L. and Zhao, Z.D., 2010. Geochemistry and geochronology of the volcanic rocks associated with the Dong’an adularia-sericite epithermal gold deposit, Lesser Hinggan Range, Heilongjiang province, NE China: constraints on the metallogenesis: Ore Geology Reviews, v. 37, p. 158-174.
-Zhu, Y., An, F. and Tan, J., 2011. Geochemistry of hydrothermal gold deposits: A review: Geosciences Frontiers, v. 2, p. 367-374.