Petrology and Geochemistry of the Qozlou Granitoid and Related Fe skarn (west Zanjan)

Document Type : Research Article

Authors

• Neda Shafaiepour ¹
• Mir Ali Asghar Mokhtari ¹
• Hossein Kouhestani ¹
• Maryam Honarmand ²

¹ University of Zanjan

² Institute for Advanced Studies in Basic Sciences (IASBS)

10.22067/econg.v12i1.70568

Abstract

Introduction
Fe skarn deposits are one of the important Fe deposits in the Zanjan province which have been exploited in recent years. The Qozlou Fe deposit is one of these Fe skarn deposits which is located at 65 km west of Zanjan. In this area, alternation of micro-sparitic limestone, marly limestone, shale and sandstones of Upper Cretaceous were intruded by Late Eocene granitoids. This event caused to metamorphism contact and it caused the formation of Fe mineralization. Some of the Fe skarn deposits in the Zanjan province were studied during the past few years (e.g. Nabatian et al., 2017) and valuable information is present about their geological and mineralization characteristics. However, Qozlou granitoid and Fe deposit have not been studied yet. In this research, petrology and geochemistry of the Qozlou granitoid along with petrographic characteristics, mineralogy, structure and texture of Fe deposit and thermodynamic conditions for formation of contact metamorphic rocks have been studied.
 
Materials and methods
This research study can be divided into two parts including field and laboratory studies. Field studies include
The recognition of different parts of granitoid intrusion and skarn aureole along with sampling for laboratory studies. Thus, 50 samples were selected for petrographic and analytical studies. 16 thin sections and 16 thin-polish sections were used for petrographical and mineralogical studies. 13 samples from granitoid and ore skarn sub-zone were analyzed by XRF and ICP-MS methods at the Zarazma laboratory, Tehran for geochemical studies. 
 
Results
Based on petrographic studies, the Qozlou granitoid is composed of porphyritic granite-granodiorite and quartz monzodiorite. Porphyritic granite-granodiorite have porphyritic to porphyroidic, micro-graphic and felsophyric textures and are composed of plagioclase, quartz, K-feldspar, hornblende and biotite phenocrysts within quartz-feldspatic groundmass. Quartz monzodiorites indicate porphyroidic texture and they are composed of plagioclase, hornblende, quartz and K-feldspar. The Qozlou granitoid demonstartes high-K calc-alkaline affinity and it is classified as metaluminous I-type granitoids. Trace elements normalized by primitive mantle (Sun and McDonough, 1989) for Qozlou granitoid indicate LILE and LREE enrichment along with negative HFSE anomalies and distinctive positive Pb anomaly. Chondrite-normalized (Nakamura, 1974) REE patterns for the Qozlou granitoid demonstrate LREE enrichment (high LREE/HREE ratio). Based on tectonic setting discrimination diagrams, the Qozlou granitoid were formed in active continental margin.
Microscopic studies reveal that the skarn zone in Qozlou is composed of garnet skarn, garnet-pyroxene skarn, pyroxene skarn, epidote skarn, and pyroxene-bearing marble sub-zones. The Ore zone is present as massive and lens-shaped with 300m length and up to 30m width. Magnetite is the main ore mineral along with some pyrite, chalcopyrite and pyrrhotite. Garnet, clinopyroxene, epidote, actinolite, calcite and quartz present in skarn zone. Based on field and microscopic studies, the Qozlou Fe deposit indicates massive, banded, disseminated, brecciated, vein-veinlets, replacement and relict textures. Based on mineralogical and textural studies, skarnization processes in the Qozlou deposit can be divided into 3 stages including: (1) isocheimal metamorphic stage, (2) prograde metasomatic stage and (3) retrograde metasomatic stage. Chondrite-normalized (Sun and McDonough, 1989) REE and trace element patterns for different skarn samples and porphyritic granite demonstrate similar patterns.
 
Discussion
Since all of minerals present in the Qozlou skarn aureole are located in Ca-Fe-Si-C-O-H system, we used the temperature vs. logƒO2 diagram (Einaudi, 1982) to determine possible physico-chemical conditions for skarn formation in the Qozlou. Based on this diagram and considering mineralogical and textural evidence, garnet and clinopyroxene were formed simultaneously in 430-550°C and ƒO2 equal 10-23 to 10-26. In the temperature less than 430°C and increasing ƒO2, garnet and clinopyroxene replaced by epidote, actinolite, quartz and calcite, respectively. Furthermore, in temperature of less than 430°C, fluids in equilibrium with granitic intrusion and with relatively high sulfidation (ƒS2>10-6), were not in equilibrium with andradite. Therefore, andradite was replaced by quartz, calcite and pyrite. With reducing ƒS2 (<10-6), andradite was replaced by quartz, calcite and magnetite. During the early retrograde stage, magnetite and pyrite were formed along with quartz and calcite. Mineralogical studies indicate that pyrite was formed after magnetite. Based on this, it seems that metasomatic fluids probably had ƒS2≈10-6.5 and had less than 430°C temperature in the beginning of the retrograde stage. Presence of hematite lamellae within the magnetite demonstrates that ƒO2 probably was 10-22 in the beginning of retrograde stage.
 
Acknowledgment
This research was made by the grant of the office of vice-chancellor for research and technology, the University of Zanjan. We acknowledge their support. The reviewers and editors of the Journal of Economic G are also thanked for their constructive comments. For geochemical studies. For geochemical studies, For geochemical studies, For geochemical studies.
 
References
Einaudi, M.T., 1982b. General features and origin of skarns associated with porphyry copper plutons. In: S.R., Titley (Editor), Advances in geology of the porphyry copper deposits, south-western North America. University of Arizona Press, Tucson, pp. 185–209.
Nabatian, Gh., Li, X.H., Honarmand, M. and Melgarejo, J.C., 2017 . Geology, mineralogy and evolution of iron skarn deposits in the Zanjan district, NW Iran: Constraints from U-Pb dating, Hf and O isotope analyses of zircons and stable isotope geochemistry. Ore Geology Reviews, 84(8):42–66.
Nakamura, N., 1974. Determination of REE, Ba, Mg, Na and K in carbonaceous and ordinary Chondrites. Geochemical et Cosmochemica Acta, 38(5): 75–775.
Sun, S.S. and McDonough, W.F., 1989. Chemical and isotopic systematics of oceanic basalts: Implication for mantle composition and processes. In: A.D. Saunders and M.J. Norry (Editors), Magmatism in the Ocean Basins, Geological Society of London Publications, Special Publication 42, London, pp. 313–345.

Keywords

• Geochemistry
• granitoid
• Fe skarn
• Qozlou
• Zanjan

20.1001.1.20087306.1399.12.1.3.0

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References

Aldanmaz, E., Pearce, J.A., Thirlwall, M.F. and Mitchell, J.G., 2002. Petrogenetic evolution of late Cenozoic, post-collision volcanism in western Anatolia, Turkey. Journal of Volcanology and Geothermal Research, 102(1–2): 67–95.

Andarz, F., 2006. Investigation of mineralogy and controlling factors of iron skarn mineralization of magnesium type in the Mineralized Region of Arjin, east of Zanjan. (Zanjan province). Unpublished M.Sc. Thesis, Islamic Azad University, Science Research Branch, Tehran, Iran, 156 pp.

Aghanabati, S A., 2004. Geology of Iran. Geological survey of Iran, Tehran, Iran, 606 pp. (in Persian)

Berman, R.G., 1988. Internally-consistent thermodynamic data for minerals in the system Na2O-K2O-CaO-MgO-FeO-SiO2-Al2O3-Fe2O3-TiO2-H2O-CO2. Journal of Petrology, 29(2): 445–522.

Besharati, S., Nabatian, Gh. and Sadeghi, A, 2010. Skarn mineralization in the Arjin region (Southwest Soltanieh). The 1th Conference of the Iranian Economic Geological Society, Ferdowsi University of Mashhad, Mashhad, Iran. (in Persian with English abstract)

Chappell, B.W. and White, A.J.R., 2001. Two contrasting granite types: 25 years later. Australian Journal of Earth Sciences, 48(4): 489-499.

Cox, K.G., Bell, J.S. and Pankhurst, R.J., 1979. The interpretation of igneous rocks. Allen and Unwin, London, 450 pp.

Deer, W.A., Howie, R.A. and Zussman, J., 2013. An introduction to the rock forming minerals. Mineralogical Society of Great Britain and Ireland, London. 498 pp.

Einaudi, M.T., 1982a. Description of skarns associated with porphyry copper plutons. In: S.R., Titley (Editor), Advances in geology of the porphyry copper deposits, southwestern North America. University of Arizona Press, Tucson, pp. 139–184.

Einaudi, M.T., 1982b. General features and origin of skarns associated with porphyry copper plutons. In: S.R., Titley (Editor), Advances in geology of the porphyry copper deposits, south-western North America. University of Arizona Press, Tucson, pp. 185–209.

Einaudi, M.T., Meinert, L.D. and Newberry, R.J., 1981. Skarn deposits. In: B.J. Skinner (Editor), Economic Geology, 75th Anniversary, The Economic Geology Publishing Company, Texas, pp. 317–391.

Fakhr Shafaie, E., 2016. Petrology and geochemistry of Khakriz granitoid (S Zanjan) and its contact metamorphic aureole. Unpublished M.Sc. Thesis. University of Zanjan, Zanjan, Iran, 97 pp. (in Persian with English abstract)

Hamidvand, M, 2016. Mineralogy, geochemistry and genesis of Incheh Rahbari Fe deposit, South Zanjan. Unpublished M.Sc. Thesis. University of Zanjan, Zanjan, Iran, 127 pp. (in Persian with English abstract)

Harris, N.B.W., Pearce, J.A. and Tindle, A.G., 1986. Geochemical characteristics of collision zone magmatism. In: M.P. Coward and A.C. Ries (Editors), Collision tectonics. Geological Society of London Publications, Special Publication 19, London, pp. 67–81.

Hastie, A.R., Ker, A.C., Pearce, J.A. and Mitchell, S.F., 2007. Classification of altered volcanic island arc rocks using immobile trace elements: Development of the Th–Co discrimination diagram. Journal of Petrology, 48(12): 2341–2357.

Hosseini, F., Hemati Ahouie, H.R. and Karimi, Gh., 2017. Evaluation of intelligent estimator performance in 3D modelling of Shahrak Fe deposit (Bijar). Journal of Mineral Resources Engineering, 2(3): 15–23. (in Persian)

Hosseini, N.A., 2008. Final exploration report of Qozlou Fe deposit. Ministry of Industry, Mine and Trade, Zanjan Province, Zanjan, Iran, 74 pp. (in Persian)

Hofmann, A.W., 1988. Chemical differentiation of the earth: the relationship between mantle, continental crust, and oceanic crust. Earth and Planetary Science Letters, 90(13): 297–314.

Irvine, T.N. and Baragar, W.R.A., 1971. A guide to the chemical classification of the common volcanic rocks. Canadian Journal of Earth Sciences, 8(5): 523–548.

Kamber, B.S., Ewart, A., Collerson, K.D., Bruce, M.C. and McDonald, G.D., 2002. Fluid-mobile trace element constraints on the role of slab melting and implications for Archaean crustal growth models. Contributions to Mineralogy and Petrology, 144(1): 38–56.

Kouhestani, H., Mokhtari, M.A.A., Shafaiepour, N. and Gholizadeh, K., 2018. Mineral chemistry and formation conditions of calc-silicate minerals in the Qozlou Fe skarn deposit, Zanjan Province, NW Iran. 8th Geochemistry Symposium, Karadeniz University, Antalya, Turkey.

Kuster, D. and Harms, U., 1998. Post-collisional potassic granitoids form the southern and northwestern parts of the Late Neoproterozoic East African Orogen: a review. Lithos, 45(1–4): 177–195.

Lotfi, M., 2001. Geological map of Mahneshan, scale 1:100000. Geological Survey of Iran.

Maanijou, M. and Salemi, R., 2014. Mineralogy, chemistry of magnetite and genesis of Korkora-1 iron deposit, east of Takab, NW Iran. Journal of Economic Geology, 6(2): 355–374. (in Persian with English abstract)

Maanijou, M. and Khodaie, L., 2018. Mineralogy and electron microprobe studies of magnetite in the Sarab-3 iron Ore deposit, southwest of the Shahrak mining region (East Takab). Journal of Economic Geology, 10(1): 267–293. (in Persian with English abstract)

Meinert, L.D., 1992. Skarns and skarn deposits. Geoscience Canada, 19(4): 145–162.

Moghaddasi, S.J., Ebrahimi, M. and Mohammadi, F., 2019. Mineralogy, geochemistry and genesis of Gozaldarreh iron deposit, southeast Zanjan. Journal of Economic Geology, 11(1): 33–55. (in Persian with English abstract)

Mohammad Beigi, N., 2017. Mineralogy, geochemistry and genesis of Qavaq Fe deposit, SW of Dandi (Zanjan). Unpublished M.Sc. Thesis, University of Zanjan, Zanjan, Iran, 131 pp. (in Persian with English abstract)

Mohammadi, F., 2013. Mineralogy, geochemistry and genesis of Qozal Darreh Fe deposit (SE Zanjan). Unpublished M.Sc. Thesis, Payam Noor University, Tehran Branch, Tehran, Iran, 96 pp. (in Persian with English abstract)

Nabatian, Gh., Li, X.H., Honarmand, M. and Melgarejo, J.C., 2017 . Geology, mineralogy and evolution of iron skarn deposits in the Zanjan district, NW Iran: Constraints from U-Pb dating, Hf and O isotope analyses of zircons and stable isotope geochemistry. Ore Geology Reviews, 84(8):42–66.

Nakamura, N., 1974. Determination of REE, Ba, Mg, Na and K in carbonaceous and ordinary Chondrites. Geochemical et Cosmochemica Acta, 38(5): 75–775.

Nouri, F., Mokhtari, M.A.A., Izadyar, J. and Kouhestani, H., 2017. Geological and mineralogical characteristics of Alamkandi Fe deposit, west of Zanjan. The 35th symposium on geosciences, Geological Survey of Iran, Tehran, Iran. (in Persian with English abstract)

Pearce, J.A., 1996. Sources and setting of granitic rock. Episodes, 19(4): 120–125.

Peccerillo, A. and Taylor, S.R., 1976. Geochemistry of Eocene calc-alkaline volcanic rocks from the Kastamonu area, Northern Turkey. Contributions to Mineralogy and Petrology, 58(1): 63–81.

Perkins, E.H., Brown, T.H. and Berman, R.G., 1986. PTX-SYSTEM: Three programs for calculation of pressure- temperature- composition phase diagrams. Computers and Geosciences, 12(6): 749–755.

Rollinson, H.G., 1993. Using geochemical data: evaluation, presentation and interpretation. Longman Group UK Limited, London, 352 pp.

Saunders, A.D., Tarney, J. and Weaver, S.D., 1980. Transverse geochemical variations across the Antarctic Peninsula: implications for the genesis of calc-alkaline magmas. Earth and Planetary Science Letters, 46(3): 344–360.

Schandle, E.S. and Gorton, M.P., 2002. Application of high field strength elements to discriminate tectonic settings in VMS environments. Economic Geology, 97(3): 629–642.

Shahbazi, S., 2010. Mineralogy, Geochemistry and Genesis of Bashkand iron ore deposit, Southwest Soltanieh. Tarbiat Modares University. Unpublished M.Sc. Thesis, Tarbiat Modares University, Tehran, Iran, 134 pp. (in Persian with English abstract)

Shahbazi, S., Ghaderi, M. and Rashidnejhad Omran, N., 2015. Mineralization stages and iron source of Bashkand deposit based on mineralogy, structure, texture and geochemical evidence, Southwest of Soltanieh. Scientific Quarterly Journal, Geosciences, 24(95): 355–372. (in Persian with English abstract)

Shand, S.J., 1943. Eruptive Rocks: Their genesis, composition, classification, and their relation to ore-deposits with a chapter on meteorite. Johan Wiley and Sons, New York, 350 pp.

Sheikhi, R., 2005. Economic geology study of Shahrak Fe deposit, east of Takab. Unpublished M.Sc. Thesis, Shahid Beheshti University, Tehran, Iran, 161 pp. (in Persian with English abstract)

Sun, S.S. and McDonough, W.F., 1989. Chemical and isotopic systematics of oceanic basalts: Implication for mantle composition and processes. In: A.D. Saunders and M.J. Norry (Editors), Magmatism in the Ocean Basins, Geological Society of London Publications, Special Publication 42, London, pp. 313–345.

Taylor, S.R. and McLennan S.M., 1985. The continental crust: its composition and evolution. Blackwell Scientific Publication, Carlton, 312 pp.

Thompson, R.N., 1982. Magmatism of the British Tertiary province Scottish. Scottish Journal of Geology, 18(1): 49–107.

Whitney, D.L. and Evans, B.W., 2010. Abbreviations for names of rock-forming minerals. American Mineralogist, 95(1): 185–187.

Wilson, M., 1989. Igneous petrology. Unwin Hyman, London, 466 pp.

Wright, J.B. and McCurry, P., 1997. Geochemistry of calc-alkaline volcanic in northwestern Nigeria, and a possible PAN-AFRICAN suture zone. Earth and Planetary Science Letters, 37(1): 90–96.

Wu, F., Jahnb, B., Wildec, S.A., Lod, C.H., Yuie, T.F., Lina, Q., Gea, W. and Suna, D., 2003. Highly fractionated I-type granites in NE China II: isotopic geochemistry and implications for crustal growth in the Phanerozoic. Lithos, 67(3–4): 191–204.