Petrogenesis and Geochemistry of REE of Intrusive Rocks, Skarn Zone, and Iron Ore of Shotorsang, Northwest of Neyshabour

Document Type : Research Article

Authors

• Mojtaba Heydari ¹
• Seyed Ahmad Mazaheri ²

¹ Ph.D. student, Department of Geology, Faculty of science, Ferdowsi University of Mashhad, Mashhad, Iran

² Professor, Department of Geology, Faculty of science, Ferdowsi University of Mashhad, Mashhad, Iran

10.22067/econg.2023.80972.1067

Abstract

Shotorsang iron skarn is located in 60 km northwest of Neyshabour (Khorasan Razavi, Iran) in Quchan-Sabzevar magmatic belt. Subvolcanic intrusion rocks have intruded into Cretaceous limestones and created skarnization. These rocks are divided into syenite porphyry and granodiorite porphyry based on their geochemical characteristics. They are I type oxidizing, metaluminous, and tectonic. Setting of the subvolcanic rocks are the subduction zone of the continental margin (VAG). Comparing the mineralization potential of the subvolcanic rocks of this area based on the use of the graph of SiO2 against K2O, MgO, Na2O+K2O, and Ni-V shows that they are fertile in terms of the formation of Fe and Cu skarn. Syenite porphyry is the origin of this mineralization, and magnesium in skarn is taken from hydrothermal fluid. The diagram of Eu/Eu*, Ce/Ce*, (Pr/Yb)n ratios also confirms the presence of meteoric water in the formation of the skarn zone. The primary fluid, which has a positive anomaly of Ce/Ce* and Eu/Eu* had acidic and oxidant conditions and high temperature, and formed pyroxene skarn. A part of magnetite mineralization is formed in this zone, and in this condition, the highest amount of REE entered the pyroxene skarn zone and diluted the fluid in terms of REE. This issue has led to a sharp decrease in the amount of REE in the mineralization zone. Negative Ce/Ce* and Eu/Eu* anomalies indicate alkaline conditions with less concentrated REE content, consistent with chlorite skarn. The highest amount of Fe mineralization is formed in this zone.
 
Introduction
Shotorsang iron skarn is located in 60 km northwest of Neyshabour (Khorasan Razavi, Iran) in Quchan-Sabzevar magmatic belt. Subvolcanic intrusion rocks have intruded into Cretaceous limestones and created skarnization (Amini and Khannazer, 2000(. This study found that at least four subvolcanic intrusion rocks are present in this region: Granodiorite porphyry, biotite syenite porphyry, quartz syenite porphyry, and quartz diorite to monzodiorite porphyry. These are divided into syenite porphyry and granodiorite porphyry based on the geochemical characteristics.
 
Material and methods
About 90 samples were collected for laboratory investigations of petrogenesis studies. Moreover, 25 samples were selected to be analyzed using the XRF and ICP-MS methods. Laboratory studies were carried out in Ferdowsi University of Mashhad and samples were analyzed in Acme and Zarazma laboratories.
 
Results
Subvolcanic rocks are I-type oxidizing, metaluminous, and tectonic. Setting of the subvolcanic rocks are the subduction zone of the continental margin (VAG). Moreover, some samples have been placed at the border of syn-collision due to high Rb, which is the result of high potassium. Enrichment of LILE elements such as K, Cs, Ba, Rb and incompatible elements that behave similar to them like Th compared to HFSE elements is observed in all samples compared to the primitive mantle. Enrichment of LILE relative to HFSE indicates magma related to subduction zones. The Sr element shows opposite behavior compared to the LILE elements. This issue can be justified by the high amount of CaO in magnetite ore (from 0.3% to more than 3.5%), because the two elements are similar in terms of chemical properties. Comparing the mineralization potential of the subvolcanic rocks of this area using the graph of SiO2 against K₂O, MgO, Na₂O+K₂O, and Ni-V shows that they are fertile in terms of the formation of Fe and Cu skarn Meinert, 1995(. For igneous rocks, it was confirmed that the amount of Rb increases during the fractionation and crystallization processes (Meinert, 1995 (. Granitoids with potential for iron skarn have lower Rb (39 ppm). This amount is 103 ppm for copper skarn and 69 ppm for gold skarn. The amount of Rb content for all granitoids of Shotorsang area is 80 ppm. Considering the connection of these granitoids with iron skarn in this area, the high Rb content can be justified by crustal contamination of these rocks (Martin-Izard et al., 2000). Moreover, it can be mixing of a mafic magma with a felsic magma at a shallow depth. The amounts of V and Ni in iron skarn deposits are the highest; that is, 152 and 35 ppm, respectively. Ni and V for Shotorsang syenite porphyry group are 16 and 82, respectively and for Shotorsang granodiorite porphyry are 20 and 48, respectively. These values are lower than the global average of iron skarn. In general, the high amount of Rb and the low amount of Ni and V confirm the hypothesis that the magma has been fractionated and contaminated with crust. If the amount of Rb as well as the amount of Ni and V increase, the mixing of a magma derived from the mantle or a mafic magma with a highly fractionated magma would seem to be a more acceptable hypothesis (Meinert, 1995). Therefore, according to what was stated about the tectonic setting and the cases mentioned above, as well as the process of changes in the spider diagram of the rare earth elements of the studied area, it can be expected that the fluid forming the iron skarn of this region has undergone magmatic fractionation and been contaminated with crust. (La/Yb)n, (La/Sm)n and (Gd/Yb)n ratios were used to evaluate the separation degree between REEs. (La/Yb)n determines the degree of separation between LREE and HREE (Aubert et al., 2001; Yusoff et al., 2013), while the other two ratios are used to determine the degree of separation between LREE and MREE, and between MREE and HREE, respectively (Yusoff et al., 2013). These ratios vary for (La/Yb)n from 1.12 to 1.69, for (La/Sm)n from 6.7 to 40.72, and for (Gd/Yb)n from 0.89 to 4.22. As it is known, during the skarnization process, the highest degree of separation has occurred between LREE and HREE (up to about 70 times) and the lowest degree of separation has also occurred between MREE and HREE. The highest value of these ratios is in the mineralization zone, which indicates that the highest amount of separation of REE elements has taken place in this zone. Syenite porphyry is the origin of this mineralization, and magnesium in skarn is taken from hydrothermal fluid.
 
Discussion
The diagram of Eu/Eu*, Ce/Ce*, (Pr/Yb)n ratios confirms the presence of meteoric water in the formation of the skarn zone (Kato, 1999). The primary fluid, which has a positive anomaly of Ce/Ce* and Eu/Eu*, had acidic and oxidant conditions and high temperature and formed pyroxene skarn. A part of magnetite mineralization is formed in this zone, and in this condition, the highest amount of REE entered in pyroxene skarn zone and diluted the fluid in terms of REE. This issue has led to a sharp decrease in the amount of REE in the mineralization zone. Negative Ce/Ce* and Eu/Eu* anomalies indicate alkaline conditions (Meinert, 1995) with less concentrated REE content, consistent with chlorite skarn. The highest amount of Fe mineralization is formed in this zone.
 
Acknowledgements
The authors are grateful for the cooperation of the employees of the Shotorsang iron ore mine, especially Mr. Qotbi.
 

Keywords

• skarn
• subduction zone
• Magnetite
• REE
• Shotorsang
• Quchan-Sabzevar Magmatic Belt

20.1001.1.20087306.1402.15.2.5.5

---

References

Alavi, M., 1991. Sedimentary and structural characteristics of the Paleo-Tethys remnants in northeastern Iran. Geological Society of America Bulletin, 103(8): 983–992. https://doi.org/10.1130/0016-7606(1991)103%3C0983:SASCOT%3E2.3.CO;2

Amini, B. and Khannazer, N.h., 2000. Geological map of Mashkan, scale 1:100,000. Geological Surver of Iran.

Arjmandzadeh, R., Almasi, A., Nabatian, G., Li, Q., Nourian, S. and Jafarie, T., 2022. Zircon U–Pb dating, geochemistry, and geology of Shotorsang hypabyssal granitoids, southern Quchan (northeast of Iran). Petrological Journal, 13(3): 105–130. https://doi.org/10.22108/ijp.2022.132228.1263

Arjmandzadeh, R. and Santos, J.F., 2014. Sr–Nd isotope geochemistry and tectonomagmatic setting of the Dehsalm Cu–Mo porphyry mineralizing intrusives from Lut Block, eastern Iran. International Journal of Earth Sciences, 103: 123–140. https://doi.org/10.1007/s00531-013-0959-4

Asadi, S., 2009. Study of iron mineralization in metamorphic rock in Kohe germez – Kohe sorkh (Qatruyeh). University of Shiraz, Shiraz, Iran, 154 pp.

Asadi-Avargane, M., Rezaei-Kahkhaei, M. and Ghasemi, H., 2020. Petrology and geochemistry of adakitic dacites of the Qarah Chay Neogene caldera, SE Quchan. Scientific Quarterly Journal of Geosciences, 29(114): 241–250.  https://doi.org/10.22071/gsj.2019.171867.1614

Aubert, D., Stille, P. and Probst, A., 2001. REE fractionation during granite weathering and removal by waters and suspended loads: Sr and Nd isotopic evidence. Geochimica et Cosmochimica Acta, 65(1–3): 387–406. https://doi.org/10.1016/S0016-7037(00)00546-9

Boynton, W.V., 1984. Cosmochemistry of the rare earth elements: meteorite studies. In: P. Henderson (Editor), Developments in geochemistry 2, Elsevier, Amesterdam, pp. 63–114. https://doi.org/10.1016/B978-0-444-42148-7.50008-3

Brooking, D.G., 1984. Geochemical aspects of radioactive waste disposal. Springer, New York, 374 pp.

Chappell, B.W. and White, A.J., 2001. Two contrasting granite types: 25 years later. Australian journal of earth sciences, 48(4): 489–499. https://doi.org/10.1046/j.1440-0952.2001.00882.x

Cox, K.‌G., Bell, J.D. and Pankhurst, R.J. (translated by S.A. Amini), 1979. The interpretation of igneous rocks. Mobtakeran, Tehran, 261 pp.

Crinci, J. and Jurkowic, I., 1989. Rare earth elements in triassic bauxites of Croatia (Yugoslavia). Travaux du Comité international pour l'étude des bauxites, de l'alumine et de l'aluminium, 19(22): 239–248. Retrieved June 11, 2021 from http://pascal-francis.inist.fr/vibad/index.php?action=getRecordDetail&idt=6631824  

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, 21(6): 547–550. https://doi.org/10.1130/0091-7613(1993)021%3C0547:MSHPEO%3E2.3.CO;2

Fathabadi, F., 2014. Geology, petrology and geochemistry of subvolcanic domes of Moghiseh area (SW-Sabzevar). M.Sc. thesis, Shahrood University of Technology, Shahrood, Iran, 164 pp.

Ghasemi, H., Sadeghian, M., Khanalizadeh, A. and Tanha, A., 2010. Petrology, geochemistry and radiometric ages of high silica adakitic domes of Neogene continental arc, south of Quchan. Iranian Journal of Crystallography and Mineralogy, 18(3): 347–370. (in Persian with English abstract) Retrieved June 01, 2023 from http://ijcm.ir/article-1-505-fa.html

Gholami, S., 2009. Geology, mineralization, geochemistry, and magnetometry of Shotor Sang iron deposit, NE Sabzevar, M.Sc thesis, Ferdowsi University of Mashhad, Mashhad, Iran, 240 pp.

Jamshidi, K., Ghasemi, H. and Sadeghian, M., 2014. Petrology and geochemistry of the Sabzevar post-ophiolitic high silica adakitic rocks. Petrological Journal, 5(17): 51–68. Retrieved May 7, 2022 from https://ijp.ui.ac.ir/article_16159.html?lang=en

Karimpour, M.H., Malekzadeh Shafaroudi, A., Esphandiarpour, A. and Mohammad Nejad, H., 2012. Neyshabour turquoise mine: the first Iron Oxide Cu-Au-U-LREE (IOCG) mineralized system in Iran. Journal of Economic Geology, 3 (2): 193–216. (in Persian with English abstract) https://doi.org/10.22067/econg.v3i2.11420

Kato, Y., 1999. Rare Earth Elements as an Indicator to Origins of Skarn Deposits: Examples of the Kamioka Zn‐Pb and Yoshiwara‐Sannotake Cu (–Fe) Deposits in Japan. Resource Geology, 49(4): 183‌–198. https://doi.org/10.1111/j.1751-3928.1999.tb00045.x

Kikawada, Y., Ossaka, T., Oi, T. and Honda, T., 2001. Experimental studies on the mobility of lanthanides accompanying alteration of andesite by acidic hot spring water. Chemical Geology, 176(1–4): 137–149. https://doi.org/10.1016/S0009-2541(00)00375-2

Küpeli, Ş., Arik, F. and Zedef, V., 2009. Rare earth element (REE) geochemistry and genetic implications of the Mortaş bauxite deposit (Seydişehir/Konya-Soutern Turkey). Chemie der Erde Geochemistry, 69: 143–159. https://doi.org/10.1016/j.chemer.2008.04.005

Kuşçu, İ., Kuşcu, G.G., Meinert, L.D. and Floyd, P.A., 2002. Tectonic setting and petrogenesis of the Çelebi granitoid, (Kırıkkale-Turkey) and comparison with world skarn granitoids. Journal of Geochemical Exploration, 76(3): 175–194. https://doi.org/10.1016/S0375-6742(02)00254-6

Malekzadeh Shafaroudi, A., 2018. Study of Au±Cu mineralization of Jalambadan area (NW Sabzavar) based on mineralogy of alteration and mineralization zones, and geochemistry. Iranian Journal of Crystallography and Mineralogy, 26(1): 31–46. Retrieved September 21, 2022 from http://ijcm.ir/article-1-1049-en.html

Malekzadeh Shafaroudi, A. and Karimpour, M.H., 2015. Mineralization and Fluid Inclusion Studies of the Khanlogh Iron Oxide-Apatite Deposit, Northeast of Iran. Advanced Applied Geology, 5(3): 59–71. (in Persian with English abstract) https://doi.org/10.22055/aag.2015.11825

Martin-Izard, A., Fuertes-Fuente, M., Cepedal, A., Moreiras, D., Nieto, J.G., Maldonado, C. and Pevida, L.R., 2000. The Rio Narcea gold belt intrusions: geology, petrology, geochemistry and timing. Journal of Geochemical Exploration, 71(2): 103–117. https://doi.org/10.1016/S0375-6742(00)00148-5 

Meinert, L.D., 1984. Mineralogy and petrology of iron skarns in western British Columbia, Canada. Economic Geology, 79(5): 869–882. https://doi.org/10.2113/gsecongeo.79.5.869

Meinert, L.D., 1995. Compositional variation of igneous rocks associated with skarn deposits-chemical evidence for a genetic connection between petrogenesis and mineralization. Mineralogical Association of Canada Short Course Series, 23, pp. 401–418. Retrieved June 27, 2022 from https://cir.nii.ac.jp/crid/1571698599180175232

Mohammadi, E., Ghorbani, G. and Shafaii Moghadam, H., 2015. Geochemistry and Petrogenesis of the Adakites in the Southern Domains of the Northern Sabzevar Ophiolites; With Emphasis on Sr-Nd-Pb Isotopes Results. Scientific Quarterly Journal of Geosciences, 24(95): 51–62. https://doi.org/10.22071/gsj.2015.42381

Panahi, M., 2009. Geology, petrography, alteration and geochemistry in eastern part of Hamdi kaolin of Halak Abad (southwestern Sabzevar) with view of copper porphyry exploration, and study of mineralization, geochemistry and magnetometry in eastern of Abozar iron mine, Neyshabour (northeastern of Sabzevar), M.Sc thesis, Ferdowsi University of Mashhad, Mashhad, 411 pp.

Panahi, M., Heydarianshahri, M.R. and Karimpour, M.H., 2011. Geology, petrography and genesis of shotorsang skarn, NE Sabzevar. 16^th symposium of crystallography and mineralogy, University of Guilan Rasht, Iran. Retrieved December 11, 2020 from https://civilica.com/doc/180645/

Pearce, J.A., Harris, N.B. and Tindle, A.G., 1984. Trace element discrimination diagrams for the tectonic interpretation of granitic rocks. Journal of petrology, 25(4): 956–983. https://doi.org/10.1093/petrology/25.4.956

Rard, J.A., 1988. Aqueous solubilities of praseodymium, europium, and lutetium sulfates. Journal of solution chemistry, 17: 499–517. https://doi.org/10.1007/BF00651459

Rollinson, H., 1993. Using geochemical data, Evaluation, Presentation, Interpretation. Harlow, United Kingdom, 352 pp.

Rossetti, F., Nasrabady, M., Vignaroli, G., Theye, T., Gerdes, A., Razavi, M.H. and Vaziri, H.M., 2010. Early Cretaceous migmatitic mafic granulites from the Sabzevar range (NE Iran): implications for the closure of the Mesozoic peri‐Tethyan oceans in central Iran. Terra Nova, 22(1): 26–34. https://doi.org/10.1111/j.1365-3121.2009.00912.x

Shand, S.J., 1943. Eruptive rocks: Their genesis, composition, classification, and their relation to ore-deposits with a chapter on meteorite. Nature 120: 872. https://doi.org/10.1038/120872a0

Spies, O., Lensch. G. and Mihem. A., 1983. Chemisrty of the post-ophiolithic tertiary volcanic between Sabzevar and Quchan, NE Iran, eodynamic project (geotraverse) in Iran. Geological Survey of Iran, Tehran, 20 pp.

Taylor, Y. and McLennan, S.M., 1985. The Continental Crust: Its Composition and Evolution. Blackwell, Oxford, 312 pp.

Wood, S.A., 1990. The aqueous geochemistry of the rare-earth elements and yttrium: 2. Theoretical predictions of speciation in hydrothermal solutions to 350 C at saturation water vapor pressure. Chemical Geology, 88(1–2): 99–125. https://doi.org/10.1016/0009-2541(90)90106-H

Yusoff, Z.M., Ngwenya, B.T. and Parsons, I., 2013. Mobility and fractionation of REEs during deep weathering of geochemically contrasting granites in a tropical setting, Malaysia. Chemical Geology, 349–350: 71–86. https://doi.org/10.1016/j.chemgeo.2013.04.016   

Zaree, A., Malekzadeh Shafaroudi, A. and Karimpour, M.H., 2016. Khanlogh magnetite-apetite deposit, NW Neyshabour: Mineralogy, structure and texture, alteration, and determination of model. Iranaian Journal of Crystallography and Mineralogy, 24(1): 131–144. Retrieved June 01, 2023 from http://ijcm.ir/article-1-122-fa.html