Mineralogy and Formation Conditions of Turquoise in Ali Abad Cu Porphyry Deposit

Home , Alunite

Archive of SID زﻣﯿﻦﺷﻨﺎﺳﯽ اﻗﺘﺼﺎدي Journal of Economic Geology ﺟﻠﺪ 12، ﺷﻤﺎره 1 (ﺳﺎل Vol. 12, No. 1 (2020) (1399 ﺻﻔﺤﺎت 9 و ISSN 2008-7306 10

Saeide Jadidi Ardekani1, Mohammad Ali Mackizadeh1* and Farimah Ayati2

1) Department of Geology, Faculty of Sciences, University of Isfahan, Isfahan, Iran 2) Department of Geology, Payame Noor University, Iran

Submitted: Apr. 18, 2018 Accepted: Feb. 05, 2019

Keywords: Turquoise, Alunite, Cu-porphyry, Ali Abad, Central Iran

Introduction Results In porphyry copper deposits, turquoise is Based on the studies, several chain processes have considered to be a supergene oxidation product been involved in the form of turquoise: the (John et al., 2010; Chavez, 2000). Based on initiator of the reactions is the formation of an Rezaian et al., 2003; Zarasvandi et al., 2005 and oxidant environment (gossan), in which metal Eslamizadeh, 2004, the Aliabad index is sulfides (Cu, Fe) in the phyllic zone of porphyry introduced as a porphyry copper system. The first copper deposit have played a fundamental role. published report on turquoise events around Ali- Turquoise has two species in this area. One is in Abad was presented by Momenzadeh et al., 1988. the form of direct deposition in the veinlets, away This area is located 57 km southwest of Yazd. from the alteration of the host rock and the Alterations often include siricitization, advanced mineralization center, and the other one is in the argillization. Kaolinization and silicification have form of substitution. It is undeniable that the host occurred frequently in the arkose and microcan rock with Kaolinite-sericite alteration is required glomerate of the Sangestan formation. The aim of for substitution. The close association of alunite- this research study is to try to reconstruct and turquoise may imply that turquoise is a product of investigate the formation and origin of turquoise the phosphatization process of alunite. The by using the latest mineralogical and geochemical Alunite Supergene event in the alteration zone and data. Field evidence shows occurrence of its accompaniment with turquoise indicates the turquoise in the form of a veinlet and nodules, mineral complex of advanced argillic alteration. with blue-green and blue-white colors. Jarosite, The mineral chemistry highlighted the high alunite, quartz and iron oxides are found together percentages of aluminum concentration which is a with turquoise. property of minerals in advanced argillic zone.

Materials and Methods Discussion A geological map of the area with a scale of The phyllic zone has the largest part of the 1/15000 was prepared. 35 samples of intrusive region's alteration (Taghipour and Mackizadeh, bodies, sandstones and altered rocks were selected 2011; Moore et al., 2011). An advanced argillic to produce thin and polished sections. XRD and zone with the presence of alunite-jarosite with the EDS analyses were carried out at the central turquoise is scattered inside the phyllic zone. To laboratory of Isfahan University and the confirm microscopic observations, XRD and EDS University of Oklahoma, USA, respectively in analyses were used. These analyses prove the order to identify the chemical composition of presence of the turquoise phase. phases. In some analyses performed on the turquoise

*Corresponding author Email: [email protected] DOI: https://doi.org/10.22067/econg.v12i1.72122 www.SID.ir Archive of SID

Journal of Economic Geology Jadidi Ardekani et al. 10 mineral phase, the presence of potassium and Seal, R.R., Taylor, R.D. and Vikre, P.G., 2010. silicon probably indicates the transitional phase of Porphyry copper deposit model. Chap. B of conversion of sericite or alunite to turquoise. Mineral deposit models for resource Pyrite in the oxidant condition has been disrupted assessment. U.S. Geological Survey Scientific by the effects of atmospheric water and created Investigations, United State of America, goethite and sulfuric acid. The produced ferric Report 2010-5070, 169 pp. sulfate can induce dissolution of chalcopyrite. The Eslamizadeh, A., 2004. Petrology of Ali-Abad- occurrence of iron oxides and oxy-hydroxides will Darreh Zereshk igneous rocks and related lead to the development of the gossan zone. copper mineralization. Ph.D. Thesis, Islamic Gossan's transformation, in addition to supplying Azad University, Tehran, Iran, 231 pp. (in copper, causes acidic fluids to continue the Persian with English abstract) reaction. Under acidic conditions, the phosphate Espahbod, M.R., 1976. Le District minier de la leaching from the arkose has been subjected to the mine de Turquoise de Kuh-e-madan following reaction: (Neychabur, Iran): Mineralisations et Ca5 (PO4)3OH + 5H2SO4 + 9/2O2 → 5CaSO4 caracteres geologiques, geochimiques et 2H2O + 3H3PO4 metallogeniques de I’uranium, du cuivre et du In addition to phosphate and copper, aluminum is molylodene. Ph.D. Thesis, Univesite de Nancy, the most important element in the structure of Nancy, France, 191 pp. turquoise. Under an acidic environment, arkose Momenzadeh, M., Farjad Bastani, M. and Rashid feldspars and hydrolysis reactions during Nejad Omran, N., 1988. Primary study on alteration will be used for the formation of Yazd Province Ore Deposirs. Proceedings of sericite, kaolinite and gypsite. With the presence ore deposits and mining potential of Yazd of sulfate and potassium released from the Province, Yazd University, Yazd, Iran. (in alteration of feldspars, alunite and turquoise can Persian) be formed. The alunite-turquoise paragenesis Moore, F., Deymar, S. and Taghipour, B., 2011. confirms formation of turquoise by alunite Genetic relation between skarn mineralization (Espahbod, 1976). Turquoise will be formed by and petrogenesis of the Darreh Zerreshk the reaction of potassium, copper sulfate and granitoid intrusion, southwest of Yazd. Journal anion phosphate with alunite: of Economic Geology, 3(2):97–110. (in + - 8K + CuSO4 + 4H2PO4 + 2KAl3 (SO4)2(OH) 6 → Persian with English abstract) + CuAl6 (PO4)4(OH)8 4H2O + 5K2SO4 + 4H Rezaian, K., Noghrehiyan, M., Mackizadeh, M.A. The hydrogen ions released in this reaction will and Sherafat, Sh., 2003. Geology and genesis lower the pH of the environment and cause of Turquoise in the Ali-Abad index (Taft- progression of hydrolysis reactions. Finally, Yazd). Research Journal of University of jarosite will be formed by the interaction of K+, Isfahan "Science", 18(2): 138–145. (in Persian sulfate and Fe3+. Based on these reactions, an with English abstract) aluminum-rich phase is needed for stabilizing Taghipour, B. and Mackizadeh, M.A., 2011. phosphate and soluble copper. Petrogenesis of skarn related Cu-porphyry intrusion deposit, Ali-Abad- Darreh Zereshk, References Yazd. Journal of Economic Geology, 3(1):79– Chavez, W.X.Jr., 2000. Supergene oxidation of 92. (in Persian with English abstract) copper deposits: zoning and distribution of Zarasvandi, A., Liaghat, S. and zentill, M., 2005. copper oxide minerals. Society of Economic Geology of the Darreh-Zerreshk and Ali-Abad Geologists, 2(41):10–21. Porphyry Copper Deposits, Central Iran. John, D.A., Ayuso, R.A., Barton, M.D., Blakely, International Geology Review, 47(6): 620– R.J., Bodnar, R.J., Dilles, J.H., Gray, F., 646. Graybeal, F.T., Mars, J.C., McPhee, D.K.,