دانشگاه فردوسی مشهدزمین شناسی اقتصادی2008-730610220190220Mineralogy, alteration, fluid inclusion and geochemical constraints of the Tappeh-Khargoosh Cu-Au deposit (SW Ardestan)کانی شناسی، دگرسانی، میان بارهای سیال و زمین شیمی کانسار مس- طلای تپه خرگوش (جنوب غرب اردستان)2993243328210.22067/econg.v10i2.62445FAالهام هاشمیاناصفهانحمایت جمالیاصفهان0000-0002-8551-6473جمشید احمدیانپیام نورJournal Article20170207Introduction
The Tappeh-Khargoosh area is located at the 15 km SW of Ardestan, in the middle section of the Urumieh-Dokhtar magmatic arc (Aghanabati, 2004). Exploration in the study area began in 2006 by Kani Pajohan-e- Spadana Company and continued in detail by the Ardestan Copper-Gold Company. Their exploration activities consist of preparing the geological map (1:5000 in scale), drilling trenches and boreholes. Also minor extraction has been done. In this paper, our focus is on mineralogy, alteration, geochemistry and fluid inclusion of the Tappeh-Khargoosh deposit for determining the genesis of mineralization. The results of this study can be used for more exploration in the study and adjacent areas.
Methodology
Samples collected along a traverses perpendicular to the mineralized veins and their alteration haloes. The geometry, morphology, mineralogy and texture of mineralization were examined. After careful microscopic studies, 7 samples were analyzed by the XRF method in the laboratory of the Tarbiat Modarres University and Iranian Mineral Processing Research Center (IMPRC) in Karaj. Six thin-polished sections and 8 polished sections were examined. Also, 32 samples of mineralized and altered zones were analyzed by Inductively Coupled Plasma with optical emission spectrometer (ICP-OES) in IMPRC. Six samples were analyzed for gold by Atomic Absorption Spectroscopy (A.A.S) method in the Kimia Pajoh Alborz laboratory. Three double polished sections prepared from mineralized quartz vein and micro thermometric studies had been analyzed by a model HF-S90 microscope in the University of Isfahan. For detail understanding of mineral composition and determination of some fine and rare minerals, the electron microprobe analyzing (EMPA) technique (model SX100) is used in IMPRC.
Discussion and results
The Tappeh-Khargoosh deposit consist of quartz vein and veinlets which occur as open space filling in Eocene andesite and dacite. The mineralized veins mainly occur in the fault zones. The subparallel fault systems of dextral strike sleep Qom-Zefreh crustal scale fault (Tajmir Riahi et al., 2012) has had the main role in localization of mineralizing fluids.
The alteration mainly consist of silicificaion, propylitization with minor sericitization and argillization represented as vein-veinlets, dissemination and pervasively in host volcanics. These alteration assemblages are indicative of near neutral to little alkaline hydrothermal fluids (Simmons et al., 2005). The silicic alteration has occurred in a wide range of pH and temperature, while the argillic alteration has occurred in low temperature and a wide range of pH. So where the silicic and argillic alterations have occurred together, the temperature of the causing fluid must be lower in the range of clay mineral stability field (Robb, 2005). The fluid inclusion in the quartz shows the low temperature (137-194˚C) and low to medium salinity (4-12.5 %) which coincide with low to medium sulfidation epithermal deposit conditions. According to fluid inclusion data, bisulfides were the main ligand for metals transportation. The absence of halite/sylvite daughter minerals in fluid inclusions and low salinity of fluid inclusions show that the chloride complexes not act as effective ligands. Opposed to high sulfidation epithermal deposits in which the magmatic waters are common, in the low sulfidation type, the meteoric waters are dominant (Foster, 1991; Vahabi Moghadam, 1993). Dilution by cold and low salinity meteoric water has the main role in mineral deposition. Pyrite, chalcopyrite, bornite, chalcocite and native gold are the primary minerals and hematite, goethite, covellite, chalcocite, cuprite, malachite, chrysocolla, azurite and atacamite are the secondary minerals, which have occurred as veinlets, open space filling, colloform, amygdal filling and dissemination in quartz vein and host rocks. Fine grain gold had be seen in the colloidal secondary Fe-oxides, which indicate that the gold probably occurred primarily in sulfide minerals and was released in the supergene process. According to microprobe analysis, Ag was measured as impurity in chalcocite. These features coincide with high correlation coefficient between precious metals and copper. So, the Cu can be used as a pathfinder element for gold exploration in this and adjacent areas. The abundance of Cu-bearing secondary minerals in the surface, indicate that the Cu has not leached effectively as a result of the little amount of pyrite and aridity of the area. In this condition, Cu which was created by oxidation of primary Cu minerals was fixed in the surface as silicate, carbonate and oxide minerals (Chavez, 2000). Geology, geometry, texture and structure, geochemistry, alteration schema, fluid inclusion and mineralogical data of the Tappeh-Khargoosh make it similar to low sulfidation (L.S) epithermal deposits.
References
Aghanabati, A., 2004. Geology of Iran. Geological Survey of Iran Publications, Tehran, 709 pp. (in Persian)
Chavez, W.X., 2000. Supergene oxidation of copper deposits: Zoning and distribution of copper oxide minerals. Society of Economic Geologists Newsletter, 41(1): 10–21.
Foster, R.P., 1991. Gold metallogeny and exploration. Springer, London, 431 pp.
Robb, L., 2005. Introduction to ore- forming processes. Blackwell Publication, Australia. 373 pp.
Simmons, S.F., White, N.C. and John, D.A., 2005. Geological characteristics of epithermal precious and base metal deposits. In: J.W. Hedenquist, J.F.H. Thompson, R.J. Goldfarb and J.P. Richard (Editors), Economic Geology, 100th Anniversary Volume: 1905-2005. Society of Economic Geologists, Littleton, Colorado, pp. 485–522.
Tajmir Riahi, Z., Beigi, S., Safaei, H. and Nadimi, A., 2012. Identification active faults and seismic tectonic Shahreza area. 31th Geosciences Conference, Geological survey and mineral explorations, Tehran, Iran. (in Persian)
Vahabi Moghadam, B., 1993. Petrographic and petrology metamorphic- magmatic rocks south of Nain. M.Sc. Thesis, University of Tarbiat Moalem, Tehran, Iran, 250 pp.کانسار تپهخرگوش در 15 کیلومتری جنوبغرب اردستان قرار دارد. رخنمونهای سنگی منطقه شامل آندزیت پورفیری، داسیت و ریولیت با سن ائوسن است که در میان آنها توف و ایگنمبریت نیز دیده می شود. در شمال محدوده نیز سنگهای رسوبی الیگو- میوسن دارای رخنمون هستند. رگههای سیلیسی کانه دار در سنگهای ائوسن (آندزیت پورفیری، داسیت و توف های ریولیتی) تشکیل شدهاند. دگرسانیها از نوع سریسیتیک، آرژیلیک، پروپلیتیک و سیلیسی هستند. رگههای سیلیسی دارای ساخت و بافتهای نواری، رگه- رگهچهای، برشی و پرکننده فضاهای خالی بوده و حاوی کانههای اولیه پیریت، کالکوپیریت، بورنیت، کالکوسیت و طلا هستند. دمای همگنشدن میانبارهای سیال از 137 تا 194 درجه سانتیگراد و شوری از 4 تا 5/12 درصد معادل وزنی نمک طعام متغیر است. ترکیب سنگ میزبان، نوع کانهها، ساخت و بافت، ژئومتری، دمای تشکیل، انواع دگرسانیها و زمینشیمی کانسار، مشابه کانسارهای اپیترمال سولفیداسیون پایین است.دانشگاه فردوسی مشهدزمین شناسی اقتصادی2008-730610220190220Alteration, mineralization, geochemistry and fluid inclusion study of the Firouzeh mine, NW Neyshabourدگرسانی، کانی سازی، زمین شیمی و مطالعه سیالات درگیر در معدن فیروزه، شمال غرب نیشابور3253543329510.22067/econg.v10i2.62579FAعلیرضا غیاثوندفردوسی مشهدمحمد حسن کریم پورفردوسی مشهد0000-0002-8708-562Xآزاده ملکزاده شفارودیفردوسی مشهد0000-0002-7373-561Xمحمد رضا حیدریان شهریفردوسی مشهدJournal Article20170305Introduction
The Firouzeh mine is located in the Northwest of Neyshabour in the Khorasan Razavi province, Northeast of Iran, and eastern side of the Quchan-Sabzevar Cenozoic magmatic arc. Widespread magmatic activity in the Quchan-Sabzevar arc, is spatially and temporally associated with several types of mineralizations such as IOCG, Cu-Au porphyry and Kiruna types (Ghiasvand et al., 2016; Karimpour et al., 2011; Fatehi, 2014; Zarei et al., 2016). The aim of this investigation is to provide an understanding of the geology, alteration, mineralization, geochemistry, fluids evolution and genesis of the Firouzeh mine.
Materials and methods
Two hundred and fifty thin and polished sections were prepared for microscopic study. Twenty-nine samples were analyzed by X-ray fluorescence (XRF) method at the laboratory of Zar Azma company, Tehran, Iran. Twenty-one samples were analyzed by the X-ray Diffraction (XRD) method at the laboratory of Kansaran Binalood company, Tehran, Iran. Sixty samples were selected for 55-elemental analysis by composition of ICP-AES (Inductively coupled plasma atomic emission spectroscopy) and ICP-MS (Inductively coupled plasma Mass Spectrometry). Moreover, Sixty samples were selected for Au analysis by Aqua Regia Digestion at the SGS Laboratories, Canada. Six doubly polished sections of quartz mineralization were prepared for microthermometric analysis. Homogenization and last ice-melting temperatures were measured using a Linkam THMSG 600 combined heating and freezing stage at the Ferdowsi University of Mashhad.
Result
The Firouzeh mine contains various Middle-Eocene subvolcanic rocks as dykes which have intruded into Paleocene-Eocene volcanic rocks. Important altrations consist of silicified, argillic and carbonate among which silicified is the most extensive. Primary minerals are magnetite, specularite, pyrite, chalcopyrite and bornite and secondary minerals are hematite, alunite, covellite, turquoise and limonite. Mineralization has occurred in the cracks and fractures at the surface and in tunnels, mainly as disseminated, stockwork, vein-veinlet and hydrothermal breccia. Geochemical explorations showed anomalies of copper (up to ppm 1074), gold (up to ppb 699), iron (up to over percent 30), cerium (up to ppm 464), lanthanum (up to ppm 227), uranium (up to ppm 243) and cobalt (up to over ppm 10000) that has many similarities with IOCG type deposits (Corriveau, 2007; Zamora and Castillo, 2001; Marschik et al., 2000(. Fluid inclusions are relatively simple liduid+vapor types, with homogenization temperature from 147 to 278ºC and average temperature of 203ºC and Salinity containing 5.56 to 17.08 wt. percent NaCl equiv. which has resulted from fluids with KCl, CaCl2, MgCl2 and NaCl compositions. Mixing process between hot and saline fluid with cold and low saline fluid and also, boiling process can caused deposition of elements.
Discussion
Firouzeh mineral deposit has magmatic-hydrothermal source and is related to tertiary magmatic activities of subduction of Neothetys Sabzevar oceanic crust beneath the Turan crust. Fluid mixing has played an important role for precipitation during mineralization and includes the source of hot and saline magmatic fluids with high contents of metallogenic elements and the mixing with cold and low saline meteoric waters resulting in the formation of deposit (Bastrakov et al., 2007; Simard et al., 2006; Wilkinson, 2001; Beane, 1983). Based on geological characteristics, alteration, mineralization, geochemistry, geophysics and fluid inclusion studies, Firouzeh mine is a great mineralization of iron oxide copper-gold-U-LREE which has similarities to the hematite-dominant section of Olympic Dam IOCG deposit.
Acknowledgments
The Research Foundation of the Ferdowsi University of Mashhad, Iran, supported this study (Project No. 3/18303). We would like to thank the Iranian mineral processing research center and laboratories of Zar Azma, Kansaran Binalood, ACME and SGS. We also thank rural cooperation of Firouzeh mine for its liaison in field survey.
References
Bastrakov, E.N., Skirrow, R.G. and Davidson, G.J., 2007. Fluid evolution and origins of Iron Oxide Cu-Au prospects in the Olympic Dam district, Gawler craton, South Australia. Economic Geology, 102(8): 1415–1440.
Beane, R.E., 1983. The Magmatic-Meteoric Transition. Geothermal Resources Council, California, Report 13, 253 pp.
Corriveau, L., 2007. Iron oxide copper gold deposits: A Canadian perspective. In: W. Goodfellow (Editor), Mineral deposit of Canada: A synthesis of major deposit- types, district metallogeny, the evolution of geological provinces, and exploration methods. Geological Association of Canada Mineral deposits Division, Vancouver, pp. 307–328.
Fatehi, H., 2014. Geology, mineralization and geochemistry of Jalambadan deposit, NW Sabzevar. M.Sc. Thesis, Ferdowsi University of Mashhad, Mashhad, Iran, 240 pp. (in Persian)
Ghiasvand, A., Karimpour, M.H., Heidarian Shahri, M.R. and Malekzadeh Shafaroudi, A., 2016. Mineralization and ground magnetic survey for mineralization prospecting and identify of intrusive bodies in the Neyshabour Firouzeh mine, Khorasan Razavi province. Journal of Advanced Applied Geology, 20(6): 86–103. (in Persian)
Karimpour, M.H., Malekzadeh Shafaroudi, A., Sfandiarpour, A. and Mohammadnejad, H., 2011. Neyshabour turquoise mine: The first IOCG-U-REE. Journal of Economic Geology, 2(3): 193–216. (in Persian)
Marschik, R., Leveille, R.A. and Martin, W., 2000. La Candelaria and the Punta del Cobre district, Chile, Early Cretaceous iron oxide Cu-Au (-Zn-Ag) mineralization. In: T.M. Porter (Editor), Hydrothermal iron oxide copper-gold and related deposits, A global perspective. Australian Mineral Foundation, Adelaide, pp. 163–175.
Simard, M., Beaudoin, G., Bernard, J. and Hupe, A., 2006. Metallogeny of the Mont-de-l’Aigle IOCG deposit, Gaspé Peninsula, Québec, Canada. Mineralium Deposita, 41(6): 607–636.
Wilkinson, J.J., 2001. Fluid inclusions in hydrothermal ore deposits. Lithos, 55(1–4): 229–272.
Zamora, R. and Castillo, B., 2001. Mineralizacio´ n de Fe-Cu-Au en el distritoMantoverde, Cordillera de la Costa, III Regio´n de Atacama, Chile. Proc 2ndCongrInt de Prospectores y Exploradores, Inst de Ingenieros de Minas del Peru´, Lima, Peru.
Zarei, A., Malekzadeh Shafaroudi, A. and Karimpour, M.H., 2016. Geochemistry and genesis of iron-apatite ore in Khanlogh deposit, eastern Cenozoic Quchan-Sabzevar magmatic arc, NE Iran.
Acta Geologica Sinica, 90(1): 121–137.
معدن فیروزه در شمالغرب نیشابور و در شرق کمربند ماگمایی قوچان- سبزوار قرار دارد و از نظر ساختاری جزو بخش غربی زون بینالود است. زمینشناسی این منطقه متشکل از گدازه و پیروکلاستیکهایی با سن پالئوسن- ائوسن است که تودههای نفوذی نیمهعمیق با سن ائوسن میانی در آنها نفوذ کرده اند. مهمترین دگرسانیهایی که واحدهای آتشفشانی و نفوذی منطقه را تحت تأثیر قرار داده شامل سیلیسی، آرژیلیک و کربناتی است. کانی سازی در سطح و تونلها در درز و شکستگیها اغلب به شکلهای افشان، استوکورک، رگه- رگهچه و برش گرمابی دیده میشود. کانیهای اولیه شامل اسپکیولاریت، مگنتیت، پیریت، کالکوپیریت و بورنیت و کانیهای ثانویه شامل هماتیت، آلونیت، کوولیت، فیروزه و لیمونیت هستند. اکتشافات ژئوشیمیایی، ناهنجاریهای عناصر مس (تا ppm 1074)، طلا (تا ppb 699)، آهن (تا 30 درصد)، سریم (تا ppm 464)، لانتانیم (تا ppm 227)، اورانیوم (تا ppm 243) و کبالت (تا بیش از ppm 10000) را نشان میدهد. بر مبنای بررسیهای سیالات درگیر، دمای تشکیل کانسار بین 147 تا 278 درجه سانتیگراد با میانگین 203 درجه سانتیگراد بوده و از محلولی شامل نمکهای KCl، CaCl2، MgCl2 و NaCl با درجه شوری بین 56/5 تا 08/17 درصد وزنی معادل نمک طعام بهوجود آمده است. فرایند اختلاط بین محلول ماگمایی گرم و شور با محلول سرد و کمشور جوی و نیز فرایند جوشش توانسته است باعث تهنشینی عناصر شود. این کانسار منشأ ماگمایی- گرمابی دارد و مرتبط با فعالیتهای ماگماتیکی ترشیری وابسته به زون فرورانش ورقه اقیانوسی نئوتتیس سبزوار به زیر صفحه توران است. بررسیهای زمینشناسی، دگرسانی، کانیسازی، ژئوشیمی، ژئوفیزیکی و سیالات درگیر در معدن فیروزه نیشابور نشاندهنده حضور کانیسازی بزرگی از نوع اکسید آهن مس- طلا- اورانیوم- عناصر نادر خاکی سبک مشابه با بخش هماتیت- غالب کانسار IOCG المپیک دم است.دانشگاه فردوسی مشهدزمین شناسی اقتصادی2008-730610220190220Petrology of porphyritic quartz monzodiorite stock and Eocene dykes with adakitic nature from SW of Jandaq (NE of Isfahan province); Evidence of oceanic crust subduction around the Central-East Iranian Microcontinentپترولوژی استوک کوارتز مونزودیوریت پورفیری و دایک های ائوسن با ماهیت آداکیتی جنوب غرب جندق (شمال شرق استان اصفهان)؛ شاهدی بر فرورانش پوسته اقیانوسی اطراف خرد قاره شرق- ایران مرکزی3553793332710.22067/econg.v10i2.63996FAاحمد جمشیدزائیاصفهانقدرت ترابیاصفهان0000-0002-4952-2614Journal Article20170426Introduction
The “adakite” term was used for the first time by Defant and Drummond (1990) to display Cenozoic arcs igneous rocks with intermediate composition (SiO2> 56 wt.%), which were produced by partial melting of subducted oceanic crust. The adakites are series of intermediate to acidic rocks, with composition range from hornblende-andesite to dacite and rhyolite; and basaltic composition are lacking. In adakitic magmas, phenocrysts are mainly plagioclase, hornblende and biotite; while orthopyroxene and clinopyroxene phenocrysts are known only in mafic andesites (Calmus et al., 2003). Geochemically, adakites are identified with SiO2> 56 wt.%, Al2O3> 15 wt.%, MgO< 3 wt.%, Sr> 400 ppm and enriched LILE and LREE and depleted Y and HREE (Y< 18 ppm, Yb< 1.9 ppm) and high ratios of Sr/Y> 40 and La/Yb> 20 (Castillo, 2006 and Castillo, 2012). By using geochemical data, adakites were classified into high silica adakites (HSA, SiO2> 60 wt.%) and low silica adakites (LSA, SiO2< 60 wt.%) main groups. The high silica adakites were produced by partial melting of subducted oceanic crust basalts and the resulting melts also interact with peridotite during their ascent through the mantle wedge. While, low silica adakites were produced by melting of mantle peridotite that were metasomatized by melts resulting from slab (Martin and Moyen, 2002).
The intrusion bodies with porphyritic texture has been studied and reported in different areas (e.g. Lan et al., 2012; Zhang et al., 2015). This intrusion bodies are often in a stock shape and the texture is porphyritic due to fast crystallization.
The study area (Kuh-e- Godar-e Siah) is located in southwest of Jandaq (northeast of Isfahan province) and northwest of Central-East Iranian Microcontinent. The quartz monzodiorite intrusion with stock shape cross cutting by Eocene dykes swarm with trachy andesitic composition. In this paper, the petrology and chemical characteristics of quartz monzodiorites and trachy andesitic dykes are discussed.
Material and methods
The chemical compositions of minerals from quartz monzodiorites and dykes were conducted by a JEOL JXA-8600 (WDS) electron probe microanalyzer (EPMA) at the Kanazawa University, Japan. Analyses were performed by an accelerating voltage of 20 kV and a beam current of 20 nA. The Fe2+ and Fe3+ contents of minerals were calculated by assuming mineral stoichiometry. The Fe2+# and Mg# parameters of minerals are Fe2+/(Fe2++Mg) and Mg/(Mg+Fe2+) atomic ratios, respectively. Representative chemical analyses of the minerals are listed in Table 1 and 2. To obtain whole rock chemical data, eighteen samples of the studied rocks were analyzed at the ALS-Mineral Company of Canada, by a combination of inductively coupled plasma spectrometry (ICP-MS) and inductively coupled plasma atomic emission spectroscopy (ICP-AES) methods. The whole rocks geochemical data are presented in Table 3 and 4. Also, X-ray diffraction analyses were carried out in order to typify the K-feldspar mineral using an XRD D8 ADVANCE, Bruker machine, at the Central Laboratory of the University of Isfahan. The FeO and Fe2O3 concentrations are recalculated from Fe2O3*, using recommended ratios of Middlemost (1989). Mineral abbreviations are from Whitney and Evans (2010).
Results and discussion
The main texture in quartz monzodiorites is porphyritic; and Eocene dykes are granular, intergranular and porphyritic in texture. The quartz monzodiorites consist of plagioclase (albite), sanidine, quartz, biotite, muscovite, chlorite, magnetite, calcite and apatite. The minerals in trachy andesitic dykes are plagioclase (andesine and labradorite), clinopyroxene (diopside and augite), sanidine, phlogopite, quartz, amphibole, magnetite, calcite and apatite. The chondrite-normalized REE patterns and primitive mantle-normalized multi-elemental diagram of the quartz monzodiorites and trachy andesitic dykes show enrichment in LREE and LILEs and depletion in HFSEs such as Ta, Nb and Ti. There is no evident positive or negative anomaly of Eu. Petrographical and geochemical characteristics of quartz monzodiorites and trachy andesitic dykes show that these rocks have been derived from different sources. The quartz monzodiorites have high content of La/Yb= 17.49-41.89, SiO2= 64.60-68.80 wt.%, Sr= 434-1855 ppm, Sr/Y= 53.58-168.63 and low content of MgO= 0.16-1.10 wt.%, Y< 11 ppm and Yb< 0.95 ppm that show characteristics of high silica adakites which have been produced by melting of subducted oceanic crust. The trachy andesitic dykes have La/Yb= 33.45-59.76, SiO2= 53.40-57.60 wt.%, Sr= 859-2050 ppm, Sr/Y= 50.82-125, MgO= 1.93-4.53 wt.%, Y< 13.8 ppm and Yb< 1.14 ppm, which display characteristics related to low silica adakites, produced by melting of metasomatized mantle peridotite.
Acknowledgments
The authors thank the University of Isfahan for financial supports.
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Middlemost, E.A., 1989. Iron oxidation ratios, norms and the classification of volcanic rocks. Chemical Geology, 77(1): 19–26.
Whitney, D.L. and Evans, B.W., 2010. Abbreviations for names of rock-forming minerals. American Mineralogist, 95(1): 185–187.
Zhang, J.Q., Li, S.R., Santosh, M., Wang, J.Z. and Li, Q., 2015. Mineral chemistry of high-Mg diorites and skarn in the Han-Xing Iron deposits of South Taihang Mountains, China: Constraints on mineralization process. Ore Geology Reviews, 64(1): 200–214.توده نفوذی نیمه عمیق کوارتز مونزودیوریت پورفیری که توسط دایکهای تراکیآندزیتی ائوسن قطعشده است، در جنوبغرب جندق (کوه گدارسیاه، شمالغرب خرد قاره شرق- ایران مرکزی) رخنمون دارد. بافت اصلی در کوارتز مونزودیوریتها بافت پورفیریتیک بوده و کانیهای آن شامل پلاژیوکلاز (آلبیت)، سانیدین، کوارتز، بیوتیت، مسکویت، کلریت، مگنتیت، کلسیت و آپاتیت است. دایکهای ائوسن بافت گرانولار، اینترگرانولار و پورفیریتیک دارند و کانیهای آن پلاژیوکلاز (آندزین و لابرادوریت)، کلینوپیروکسن (دیوپسید و اوژیت)، سانیدین، فلوگوپیت، کوارتز، آمفیبول، مگنتیت، کلسیت و آپاتیت هستند. دادههای ژئوشیمیایی سنگ کل از توده نفوذی و دایکهای این منطقه ماهیت متاآلومین را برای این سنگها مشخص میکند. آنالیزهای سنگ کل ماهیت کالکآلکالن سنگهای توده نفوذی و ماهیت کالکآلکالن پتاسیم بالا تا شوشونیتی را برای دایکها نشان میدهد. الگوهای بهنجارشده با کندریت و نمودار چند عنصری بهنجارشده با گوشته اولیه در کوارتز مونزودیوریت پورفیری و دایکهای تراکیآندزیتی، غنیشدگی از LREE و LILEها و تهیشدگی از HFSEها مانند Ta، Nbو Ti نشان میدهند. در این سنگها آنومالی مثبت یا منفی مشخص عنصر Eu وجود ندارد. این سنگها احتمالاً در محیط فرورانشی متعلق به کمان آتشفشانی تشکیل شدهاند. کوارتز مونزودیوریت پورفیری دارای مقادیر بالای 89/41-95/17 =La/Yb، wt.%80/68- 60/64 =SiO2، ppm 434-1855=Sr و 63/168-58/53 =Sr/Y و مقادیر پایین wt.%10/1- 16/0 =MgO، ppm 11 > Yو ppm 95/0 >Yb هستند و ویژگیهای آداکیتهای غنی از سیلیس را نشان میدهند که از ذوب اسلب اقیانوسی فرورونده ایجاد شدهاند. دایکهای تراکیآندزیتی دارای مقادیر 76/59-45/33 =La/Yb، wt.%60/57- 40/53 =SiO2، ppm 859-2050 =Sr و 125-82/50 =Sr/Y و مقادیر wt.%53/4- 93/1 =MgO، ppm 8/13 > Yو ppm 14/1 >Yb هستند و ویژگیهای مرتبط با آداکیتهای فقیر از سیلیس را نشانداده که در نتیجه ذوب پریدوتیت گوشتهای متاسوماتیسمشده، حاصل شدهاند. با درنظر گرفتن زمان و مکان تشکیل این سنگها میتوان نتیجه گرفت که سنگهای مورد بررسی مرتبط با فرورانش پوسته اقیانوسی اطراف خرد قاره شرق- ایران مرکزی (مثلاً پوستههای اقیانوسی عشین و نائین) هستند.دانشگاه فردوسی مشهدزمین شناسی اقتصادی2008-730610220190220Geological and mineralogical evolution of Lower Paleozoic (Late Cambrian) Corundum-Rich Metabauxite in the Southeast Sirjan, Sanandaj-Sirjan Zoneتحولات زمین شناختی و کانی شناختی متابوکسیت غنی از کرندوم پالئوزوئیک زیرین (کامبرین پایانی) در جنوب خاوری سیرجان، پهنه سنندج- سیرجان3814023335410.22067/econg.v10i2.60677FAمحسن مباشریصنعتی شاهرودفردین موسیوندصنعتی شاهرود0000-0003-0305-0794مجتبی رستمی حصوریصنعتی شاهرودJournal Article20161129Introduction
Bauxite deposits in Iran are dominantly hosted by Late Triassic-Early Jurassic sequences in the Alborz zone and Late Cretaceous in the Zagros zone (e.g., Zarasvandi et al., 2008). Metamorphosed bauxite deposits in Iran are very rare, such as Heidarabad corundum-rich deposit (Emamali-pour, and Mirmohammadi, 2011). The Qale-Kham ore deposit is the first report of bauxite mineralization in the Early Paleozoic sequences of Sanandaj- Sirjan zone. In southeastern Sirjan (Qale-Kham area), karstic pockets of Late-Cambrian metabauxites embedded in carbonate rocks. The corundum-rich metabauxites are very rare in the world. Bauxite deposits can be classified into three main groups: lateritic, sedimentary and karstic-types. The karstic bauxite deposits have formed on the paleokarstic surface of carbonates (Bárdossy, 1982; Bárdossy and Aleva, 1990; Bogatyrev et al., 2009). The aim of this paper is to discuss genesis of the Qale-Kham bauxite deposit based on geological, petrographic, mineralogical and geochemical evidences.
Materials and Methods
A number of 95 samples were collected from the bauxite lenses in the Qale-Kham ore deposit. Optical microscopic investigations were conducted on 40 thin sections, 35 thin-polished sections and 20 polished sections of the samples using a Zeiss optical microscope equipped at the Shahrood University of Technology. Mineralogical analyses were done by X-ray diffractometer equipped with a CuKα tube and monochrometer (XRD Philips PW 1800) at the Kansaran Binaloud Company. The concentration of the major elements in the samples was determined using a wavelength X-ray fluorescence spectrometer (XRF Philips PW 1480) at the Kansaran Binaloud Company.
Discussion
In the Qale-Kham area, the rock units consist of amphibolite, mica schist, chlorite schist, epidotic schist and marble. The ores are mainly massive; however, pisolitic texture was observed in the deposit. Detailed mineralogical analyses of the Qale-Kham metabauxite deposit have been performed by optical microscopy and X-ray diffraction (XRD) studies. XRD results show that ore at the metabauxite deposits is composed of corundum, diaspore, chloritoid, opaque minerals (magnetite, hematite, ilmenite, and rutile), white mica (margarite, muscovite), goethite and limonite.
Mineralogy of ores (such as corundum) and textures are representative of the impact of a metamorphic event on bauxite ores. This metamorphism and deformation has created structures, textures and formation of new minerals such as corundum and magnetite in the Qale-Kham ore deposit. The ores are mainly composed of Al2O3 (25–58%), SiO2 (3–15%), Fe2O3 (15–34%) and TiO2 (2–5%). Alkalis and alkali earth elements show low values, probably because these elements are highly mobile and have usually leached out during chemical weathering (Gu et al., 2013).
The triangular variation diagrams of Al2O3–SiO2–Fe2O3 are commonly used to show the degree of lateritization, mineral control and bauxite classification. Based on the mineralogical classification of Aleva (1994), most of the bauxite samples in the studied areas fall within the bauxite and ferritic bauxite fields. The chemical composition of corundum-rich metabauxites in Qale-Kham is nearly similar to those of other karst bauxite and karstic metabauxite such as corundum-rich metabauxites of the Menderes Massif (e.g., Özlü, 1983). They show generally strong enrichment in Al2O3, Fe2O3 and strong depletion in K2O, Na2O contents. Overal, the studied corundum-rich metabauxites at Qale-Kham can be classified as karstbauxites based upon their geological, mineralogical and geochemical characteristics.
Results
Corundum-rich metabauxite of Qale-Kham in the best outcrop is located at the SE Sirjan town. The metabauxite formed in the Paleozoic metamporphosed carbonate sequences of the South Sanandaj-Sirjan zone as karst-type deposits. Based on petrological and X-ray studies, the Qale-Kham ores consist of corundum, diaspore, chloritoid, opaque minerals (magnetite, hematite, ilmenite and rutile), white mica (margarite and muscovite), goethite and limonite.
These studies suggest that the Qale-Kham ore deposit has been formed under suitable climatic conditions in the late Cambrian. This deposit has been metamorphesd and deformed due to the effect of early Cimmerian orogenic movements. References
Aleva, G.J.J., 1994. Laterites: concepts, geology, morphology and chemistry. International Soil Reference and Information Centre (ISRIC), Wageningen, Netherlands, 169 pp.
Bárdossy, G., 1982. Karst bauxites. Elsevier, Amsterdam, 441 pp.
Bárdossy, G. and Aleva, G.J.J., 1990. Lateritic bauxite. Elsevier, Amsterdam, 624 pp.
Bogatyrev, B.A., Zhukov, V.V. and Tsekhovsky, Y.G., 2009. Formation conditions and regularities of the distribution of large and superlarge bauxite deposits. Lithology and Mineral Resources, 44(2): 135–151.
Emamali-pour, A. and Mirmohammadi, M.S., 2011. Mineralogy and geochemistry of corundum-bearing metabauxite- laterite from Heydarabad, SE Urmia, NW Iran. Iranian Journal of Crystallography and Mineralogy, 19(1): 59–72. (in Persian with English abstract)
Gu, J., Huang, Z., Fan, H., Jin, Z., Yan, Z. and Zhang, J., 2013. Mineralogy, geochemistry, and genesis of lateritic bauxite deposits in the Wuchuan–Zheng'an–Daozhen area, Northern Guizhou Province China. Journal of Geochemical Exploration, 130(6): 44–59.
Özlü, N., 1983. Trace-element content of ‘Karst Bauxites’ and their parent rocks in the Mediterranean Belt. Mineralium Deposita, 18(3): 469–476.
Poosti, M., Khakzad, A. and Fadaeian, M., 2011. Bauxite and deposits in Iran. University of Hormozgan, Hormozgan, 229 pp.
Zarasvandi, A., Charchi, A., Carranza, E.J.M. and Alizadeh, B., 2008. Karst bauxite deposits in the Zagros Mountain Belt, Iran. Ore Geology Reviews, 34(4): 521–532.کانسار قلعه خم نخستین گزارش از وجود ذخایر بوکسیتی در توالی پالئوزوئیک آغازین پهنه سنندج- سیرجان است. این کانسار بهصورت عدسیهای نامنظم در درون مجموعه مرمرهای کلسیتی- دولومیتی متراکم و تودهای کامبرین پایانی جایگرفته است. کانسار قلعه خم از دو بخش غنی از هماتیت و کرندوم (افق بالا) و بخش حاوی آلومینوسیلیکاتهای ورقهای (افق پایین) تشکیلشده است. بر اساس نتایج آنالیز XRD و بررسیهای میکروسکوپی، حضور کانیهایی نظیر کرندوم، مگنتیت، دیاسپور و کلریتوئید در این کانسار به اثبات رسیده است. این همیافت بیانگر تأثیر رخداد دگرگونی پس از فرایند بوکسیتیشدن در این کانسار است، بهعلت دگرگونی اعمالشده، کانسنگ بوکسیتی اولیه به نهشتههای متابوکسیتی و یا ذخایر اِمری تبدیلشده است. نتایج حاصل از آنالیزهای XRF نیز بیانگر آن است که بوکسیتهای قلعه خم حاوی مقادیر 25 تا 58 درصد Al2O3، 15 تا 34 درصد Fe2O3، 3 تا 15 درصد SiO2 و 2 تا 5 درصد TiO2 هستند. بررسی نمونههای بوکسیتی در نمودار تغییرات Al2O3 – Fe2O3 – SiO2 نشاندهنده آن است که اغلب این نمونهها در گستره بوکسیت و بوکسیتهای آهن دار قرار میگیرند. بر اساس نتایج پژوهش حاضر، در کامبرین پایانی و در شرایط اقلیمی مناسب، بوکسیتهای جنوب خاور سیرجان تشکیلشده و سپس تحت تأثیر دگرگونی و دگرشکلیهای ناشی از حرکات کوهزایی سیمیرین پیشین به متابوکسیتهای غنی از کرندوم تبدیل شدهاند.دانشگاه فردوسی مشهدزمین شناسی اقتصادی2008-730610220190220Comparison of mineralization of the Sungun and Kighal porphyry copper deposits, NW Iran: with an emphasis on fluid inclusion studiesمقایسه سیستم های مس پورفیری سونگون و کیقال، شمال غرب ایران : با تأکید بر مطالعه سیالات درگیر4034243337910.22067/econg.v10i2.61340FAطیبه رمضانیبوعلی سینامحمد معانی جوبوعلی سینا0000-0001-7843-419Xسینا اسدیشیرازدیوید لنتزنیوبرونزویکناصر پیروزنیامجتمع مس سونگونJournal Article20161226Introduction
Nowadays, more than half of the word’s copper production is obtained from porphyry copper deposits, large (greater than 100 Mt), low- to moderate-grade, disseminated, stockwork-veinlet, carrying at least trace elements, such as molybdenum, gold, and silver (Sillitoe, 1972). Porphyry Cu systems are related to granitoid porphyry intrusions and adjacent wall rocks and most of them form at convergent plate margins (John et al., 2010). The deposits are often localized within calc-alkaline porphyry magmatic systems in subduction zone settings. Some PCDs have been formed in post-subduction settings. Ahar-Arasbaran metallogenic zone is one of the most productive metallogenic zones in Iran. Mineralization in the area is mainly associated with Tertiary magmatic events. In order to perform a comparative study of mineralization, Sungun and Kighal porphyry copper deposits (PCDs) were selected. The Sungun copper deposit is located in the north Varzaqan and the Kighal copper deposit lies 10 km to the south of the Sungun PCD (Calagari, 2003; Calagari, 2004).
As recent studies show there are some similarities between the Sungun and Kighal deposits in terms of the parent intrusions, the host rocks, age and geological setting. However, the grade of copper in the Sungun PCD is 0.62 % Cu and in the Kighal PCD is 0.2 % Cu. Therefore, what are the key factors that have made the Kighal PCD sub-economic?
Material and methods
Geochemical, fluid inclusion, and mineralogical studies were done on collected samples of the two porphyry copper deposits. In order to mineralogically study the Sungun and Kighal PCDs, 100 thin and polished thin sections were prepared. Eleven doubly polished sections of different quartz veins of the two PCD borehole samples were prepared for fluid inclusion studies. The measurements of 205 fluid inclusions were conducted at the Iranian Mineral Processing Research Center (IMPRC) by ZEISS microscope and Linkam TMH600, at temperature limits of -196 to +600 °C. The precision was ±0.6 °C at 414 °C (melting point of Cesium nitrate), and ±2°C at -94.3 (melting point of n-Hexane). SPSS 17 and Flincor computer programs (Brown, 1989) were used for data analysis.
Discussion and Results
In addition to some similarities of parent intrusions and host rocks (Hassanpour, 2010), there are similar fluid inclusion types and even nearly identical salinity and homogenization temperatures in these deposits (Simmonds, 2013). However, some differences in geochemical and mineralogical features, such as different low zonality index, less sulfide minerals and CO2 contents of the Kighal PCD, are notable. Some researchers have pointed out erosion (Hassanpour, 2010) and uplifting (Simmonds, 2013) as the main reasons for the sub-economic nature of the Kighal (non-productivity), comparison of Moho depth in the two deposits shows a greater crustal thickness in the Sungun PCD area (Fig. 10). The thickness of the lower crust is thought to be critical for governing arc mineralization potential, because it leads to an increase of the amount of water, metal, sulfur in adakitic magma forming arc-related bodies that is known to affect the origin of more productive (economic) porphyry copper deposits. Also low-CO2 fluid inclusions of the Kighal can have originated from a CO2-rich fluid immiscibility at depth (Simmonds, 2013). Lack of CO2 can inhibit (delays) bulk volatile saturation and in turn boiling, which influences the efficiency of metal removal from melt as well (Candela, 1997). CO2 contents of mineralizing fluids is important in increasing of pH during boiling event and ore deposition. The non-productivity of the Kighal PCD may have resulted from all these factors.
Acknowledgement
This work was supported by Bu-Ali Sina University and Iranian Mines and Mining Industries Development and Renovation Organization (IMIDRO). The authors would like to thank of the Sungun and Ahar copper companies. Special thanks to all the staff for their kind help. Thanks to the reviewers for their suggestions.
References
Brown, P.E., 1989. FLINCOR; a microcomputer program for the reduction and investigation of fluid-inclusion data. American Mineralogist, 74(11): 1390–1393.
Calagari, A.A., 2003. Stable isotope (S, O, H and C) studies of the phyllic and potassic–phyllic alteration zones of the porphyry copper deposit at Sungun, East Azarbaidjan, Iran. Journal of Asian Earth Sciences, 21(7): 767–780.
Calagari, A.A., 2004. Fluid inclusion studies in quartz veinlets in the porphyry copper deposit at Sungun, East-Azarbaidjan, Iran. Journal of Asian Earth Sciences, 23(2): 179–189.
Candela, P.A., 1997. A review of shallow, ore-related granites: textures, volatiles, and ore metals. Journal of Petrology, 38(12): 1619–1633.
Hassanpour, S., 2010. Metallogeney and mineralization of Cu-Au in Arasbaran Zone, NW of Iran. Ph.D. Thesis, Shahid Beheshti University, Tehran, Iran, 320 pp.
John, D., Ayuso, R., Barton, M., Blakely, R., Bodnar, R., Dilles, J., Gray, F., Graybeal, F., Mars, J. and McPhee, D., 2010. Porphyry copper deposit model, chap. B of Mineral deposit models for resource assessment, US Geological Survey Scientific Investigations Report, 169 pp.
Sillitoe, R.H., 1972. A plate tectonic model for the origin of porphyry copper deposits. Economic geology, 67(2): 184–197.
Simmonds, V., Calagari, A.A. and Kyser, K., 2013. Fluid inclusion and stable isotope studies of the Kighal porphyry Cu–Mo prospect, East-Azarbaidjan, NW Iran. Arabian Journal of Geosciences, Fluid inclusion and stable isotope studies of the Kighal porphyry Cu–Mo prospect, East-Azarbaidjan, NW Iran. Arabian Journal of Geosciences, 8(1): 1–17.منطقه فلززایی اهر- ارسباران یکی از مهمترین زونهای فلززایی ایران در ترشیاری بهشمار میرود. کانهزایی در منطقه اغلب وابسته به سنگهای ماگمایی ترشیاری است. از این منطقه، دو سیستم مس پورفیری سونگون و کیقال برای بررسی مقایسهای نحوه کانهزایی انتخاب شدند. بر روی این دو کانیسازی بررسی زمینشیمی، سیالات درگیر و کانیشناسی انجامشد. انواع سیالات درگیر دو معدن مشابه و شامل نوع دو فازی مایع- گاز (L-V)، نوع دو فازی گاز- مایع (V-L)، نوع سه فازی مایع- گاز- جامد (گاهی هماتیت) (L-V-S)، نوع سه فازی مایع- گاز - نمک (L-V-H) و نوع چهار فازی مایع- گاز- نمک- جامد (L-V-H-S) است. نتایج نشان داد که با وجود شباهت سنگ درونگیر، سنگ مادر و انواع سیالات درگیر و حتی شوری و دمای همگن سازی تقریباً مشابه، در وسعت دگرسانی، ضخامت پوسته و میزان CO2 سیالات آنها تفاوتهایی وجود دارد. به بیان دیگر معدن سونگون بهعلت ضخامت بیشتر لیتوسفر شرایط بهتری در تأمین فلزات و تشکیل کانیهای سولفیدی داشته است. همچنین حضور CO2 و تشکیل فرایند نامیژاکی سیال در افزایش pH و تهنشینی کانسنگ سونگون مؤثر بوده است و این موجب بارور بودن معدن سونگون و نیمه بارور بودن اندیس کیقال شده است.دانشگاه فردوسی مشهدزمین شناسی اقتصادی2008-730610220190220Geochronology, Petrology and Geochemistry of Intermediate and Mafic Rocks of Bornaward Plutonic Complex (Northwest Bardaskan, Iran)سن سنجی، پترولوژی، ژئوشیمی و تکتونوماگماتیسم سنگ های حدواسط و مافیک کمپلکس پلوتونیک برنورد (شمال غرب بردسکن)4254483340210.22067/econg.v10i2.66703FAرضا منظمی باقرزادهفردوسی مشهدمحمد حسن کریم پورفردوسی مشهد0000-0002-8708-562Xجی لنگ فارمرکلرادوچارلز استرنکلرادوژوزه فرانسیسکو سانتوسآویروسارا ریبیروآویروبهنام رحیمیفردوسی مشهد0000-0001-9325-5958محمد رضا حیدریان شهریفردوسی مشهدJournal Article20170808Introduction
The study area is located in the northeast of Iran (the Khorasan Razavi province) and 28 km northwest of Bardaskan city and in position of 57˚ 46΄ to 57˚ 52΄ latitude and 35˚ 21΄ to 35˚ 24΄ longitude. The study area is a part of Taknar zone. The Taknar geological-structural zone is situated in the north Central Iranian microcontinental and it is a part of Lut block (Fig.1). Taknar plutonic complex that is situated in the Taknar structural zone is located in the northern part of Iranian microcontinent.
Materials and methods
Chemical analysis of REE and minor elements of samples of the Bornaward diorites and gabbro’s took place in the ACME Lab. in Vancouver, Canada, by the ICP-MS method (Table. 1). For the Bornaward diorite dating by the U-Pb method, zircon grains of material remaining in the sieve, Bromoform were isolated from light minerals by cleaning and were isolated with a minimum size of 25 microns, and then studies took place in the Crohn's Laser Lab Arizona (Gehrels et al., 2008). Measurement of Rb, Sr, Sm and Nd isotopes and (143Nd/144Nd)i , (87Sr/86Sr)i ratios and ƐNd (T=552), ƐNd (T=0), ƐSr (T=552) and ƐSr (T=0) took place in radioisotope Laboratory, University of Aveiro in Portugal.
Discussion
Geology of study area
The study area forms the central part of the Bornaward plutonic complex. This complex is a granitoid assemblage including granite, granodiorite, tonalite and granophyre.tscentral part has been formed by intermediate and basic intrusive rocks such as diorite, quartz diorite and gabbro units (Fig. 2). From the genetic point of view, the intermediate and mafic rocks of the Taknar plutonic complex does not have any relationship with granitoid rocks of this assemblage, and they are related to a similar magmatic phase but are separated from this granitoid assemblage. However, these mafic and intermediate units are older than granitic units at the rim of the complex that are called Bornaward granite.
Petrography
The main minerals in the diorite and quartz diorite rocks are plagioclase and hornblende and we can see biotite in the quartz dioritic rocks. Quartz exist as tiny grains and anhedral and in the matrix rock. The amount of Quartz in the quartz diorites is 5 to 20%. Plagioclases usually have normal zoning and are highly altered to sericite. Most of the plagioclases were saussuritized. Altered minerals resulted from plagioclase and hornblende are sericite, epidote, chlorite, zoisite and clinozoisite.
The main minerals in the gabbro are pyroxene, hornblende, and fine grains plagioclase. Minor minerals in the rocks are apatite, magnetite and other opaque.
The main texture of intermediate and mafic rocks in this assemblage is medium granular to coarse grain and especially in the intermediate rocks and gabbro rocks, we can see scattered poikilitic, intersertal, sub-ophitic and porphyroid texture.
Geochemistry
The area diorite and gabbro is located locate in Tholeiitic and Calc-alkaline series (Fig. 9). Shand index (Al2O3/(CaO+Na2O+K2O)) is obtained under 1.1, in Metaluminous field (Fig. 7) and I-type granite field (Chappell and White, 2001). Based on the TAS diagram (Middlemost, 1985), all the diorite and gabbro samples are located in diorite, gabbro-diorite and gabbro-norite groups (Fig. 6). The diorite and gabbro’s show enrichment LREE and low ascending pattern ((La/Yb)N =1.40-6.12 and LaN =12.26-75.81).
U-Pb zircon geochronology
Measurement of U-Th-Pb isotopes of the Bornaward diorite zircons of BKCh-03 sample (Table 2) show that its age is related to 551.96±4.32 Ma ago (Upper Precambrian (Neoproterozoic) (Ediacaran) (Fig. 14).
Sr-Nd isotopes
The (87Sr/86Sr)i and (143Nd/144Nd)i content of Bornaward diorite and gabbro rocks is located in the range of 0.7038 to 0.7135 and 0.51203 to 0.51214, respectively (Tables 3 and 4). It shows that the diorite and gabbro rocks can be affected by hydrothermal alteration because their (87Sr/86Sr)i is above (Fig. 16). The numeral amounts of ƐNd(T=552) of Bornaward diorite and gabbro are 2.0 to 4.0.
Petrogenesis
The Bornaward diorite and gabbro rocks show a widespread enriched pattern of Rb, U, K, Pb, La and Th elements than chondrite, while Ba, Ti, Ta, Sr and Nb elements show reduction as a result of fractional crystallization (Fig. 11). The rocks of this complex are formed at the continental margin and VAG environment (Fig. 18) which is related to the subduction of the oceanic crust that exists between the Iranian microcontinent and the Afghan Block.
Results
This assemblage with age of Late Neoproterozoic is the result of extensive magmatism in the northern part of the Iranian microcontinent due to Katangahi orogeny event. The similar magmatism in the northern part of the Iranian microcontinent is existing as Khaf-Kashmar-Bardeskan volcano-plutonic belt.
Based on the geochemical investigations, the magmatism of these rocks has been tholeiitic and calk-alkaline and have formed the coexistent rocks with I-type granites. Alumina saturation index for intermediate and mafic rocks of Bornaward complex is metalumina. These are medium-K rocks and enriched in the LILE such as Rb, Pb, U and Th while depleted of the Nb, Ti, Ta, Sr and Ba. Therefore, it shows that these rocks have resulted from the mixing by the lower crust.
The low (87Sr/86Sr)i Bornaward diorite and gabbro rocks and the numeral amounts of Ɛ0Nd(present) of these rocks from -0.2 to 4.0 show that production of such intrusive masses can be attributed to the source of upper mantle or contaminated lower continental crust. Environment of formation of the intermediate and basic rocks of the Bornaward plutonic complex is active continental margin and
volcanic arc environment.
References
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.
Gehrels, G.E., Valencia, V.A. and Ruiz, J., 2008. Enhanced precision, accuracy, efficiency, and spatial resolution of U–Pb ages by laser ablation– multicollector– inductively coupled plasma-mass spectrometry. Geochemistry, Geophysics, Geosystems, 9(3): 1–13.
Middlemost, E.A.K., 1985. Magmas and Magmatic Rocks. An Introduction to Igneous Petrology. Longman, London, New York, 266 pp.کمپلکس پلوتونیک برنورد واقع در زون ساختاری تکنار، در شمال خرد قاره ایران مرکزی و در20 کیلومتری شمالغرب شهرستان بردسکن قرار دارد. این مجموعه با سنی معادل اواخر پرکامبرین (نئوپروتروزوئیک)، نتیجه فعالیت ماگمایی وسیع شمال خرد قاره ایران مرکزی در اثر پدیده کوهزایی کاتانگاهی است. مشابه این ماگماتیسم در شمال خرد قاره ایران مرکزی بهصورت کمربند ولکانو- پلوتونیک خواف- کاشمر- بردسکن همچون گرانیتوئیدهای کاشمر وجود دارد. این کمپلکس بزرگ مقیاس در واقع مجموعهای گرانیتوئیدی شامل سنگهای گرانیتی، گرانودیوریتی، تونالیتی و گرانوفیری است که بخش مرکزی آن از یک گروه واحدهای گابرویی، دیوریتی و کوارتزدیوریتی تشکیلشده است. بافت اصلی این سنگهای حدواسط و مافیک، گرانولار متوسط تا درشتبلور است و بافتهای پورفیروئید بهویژه در سنگهای حدواسط و بافتهای پوئیکلیتیک و سابافیتیک در سنگهای گابرویی بهصورت پراکنده به چشم میخورد. کانی اصلی فرومنیزیندار سنگهای مافیک و حدواسط، کانی هورنبلند است و در نمونههای کوارتزدیوریتی، بیوتیت نیز دیده میشود. سنگهای حدواسط و مافیک کمپلکس پلوتونیک برنورد از لحاظ ژنتیکی با سنگهای گرانیتوئیدی این مجموعه ارتباطی مستقیم دارند. از لحاظ ارتباط صحرایی و بررسیهای سنی چنین مشخص میشود که این واحدهای مافیک و حدواسط نسبت به واحد گرانیتی و دیگر واحدهای نفوذی اسیدیی این کمپلکس قدیمیتر بوده و توسط این واحدها قطع شدهاند.
بر اساس سنسنجی دیوریتهای منطقه برنورد با استفاده از کانی زیرکن بهروش U-Pb، سن این تودههای نفوذی 32/4± 96/551 میلیون سال قبل (اواخر پرکامبرین) بهدست آمده است. بر پایه بررسیهای ژئوشیمیایی، تحولات ماگمایی این سنگها از نوع تولئیتی و کالکآلکالن بوده و شاخص اشباع از آلومین این سنگها متاآلومین است. دیوریتها و گابروهای برنورد از نوع پتاسیم متوسط بوده و از لحاظ ویژگیهای ژئوشیمیایی نسبت به عناصر ناسازگار La, Rb, K, U, Pb بههمراه Th غنیشدگی نشان میدهند؛ در حالیکه عناصری مانند Nb, Ti, Ta, Sr, Ba تهیشدگی شاخصی را در مقایسه با کندریت ارائه میدهند.
ویژگی ایزوتوپی i(143Nd/144Nd) دیوریتها و گابروهای برنورد در گستره 51203/0 تا 51214/0 بهدست آمده است. مقدار عددی نسبت i(87Sr/86Sr) این تودههای نفوذی در گستره 7038/0 تا 7135/0 اندازهگیری شده است. مقدار عددی ƐNd(T=552) دیوریتها و گابروهای برنورد از 0/2 تا 0/4 بهدست آمده است. مقادیر پایین i(87Sr/86Sr) نمونههای دیوریت و گابروهای منطقه برنورد و مقادیر Ɛ0Nd(present) این تودههای نفوذی که 2/0- تا 0/4 محاسبهشده است، نشاندهنده آن است که تولید چنین تودههای نفوذی میتواند به منبعی از گوشته بالایی یا پوسته قارهای زیرین تحت آلایش قرارگرفته شده، نسبتداده شود. محیط تشکیل این دسته از سنگهای کمپلکس پلوتونیک برنورد، حاشیه فعال قاره و محیط کمان آتشفشانی است که میتواند به فرورانش پوسته اقیانوسی موجود بین خرد قاره ایران مرکزی و بلوک افغان مرتبط باشد.دانشگاه فردوسی مشهدزمین شناسی اقتصادی2008-730610220190220Petrography and mineral chemistry of the Eocene granodiorites in the Toveireh area (Southwest of Jandaq, Isfahan province)پتروگرافی و شیمیکانی گرانودیوریت های ائوسن تویره (جنوب غرب جندق، استان اصفهان)4494703342410.22067/econg.v10i2.60825FAمعصومه سرگزیاصفهانقدرت ترابیاصفهان0000-0002-4952-2614Journal Article20161206Introduction
Granitoids are the most common igneous rocks that are found in all parts of the continental crust and play an important role in the formation and evolution of the Earth’s continental crust (Clarke, 1992). Granitoid plutons contain useful information on factors and processes related to their generation and differentiation (Castro, 2013). The wide range of sources and processes that may be involved in the formation of granitoids is reflected in their compositional range. Although yet there is a long way to achieve a consensus about the origin of granite, different interpretations of the geochemical granitoid data represents geological understanding of the complexities of these rocks.
Large parts of Iran and Central - East Iranian Microcontinent (CEIM) structural zone have suffered from the Eocene granitoid magmatism. Toveireh granitoid intrusive body cropped out in the southwest of the Jandaq city (NE of Isfahan Province) and is one of the Eocene granitoid bodies. It is hoped that this mineralogical and petrological research will be useful in understanding the nature of Eocene acidic magmatism of Central Iran.
Material and methods
Chemical analyses of minerals in the Toveireh granodiorites were carried out by a JEOL JXA-8800R (WDS) electron probe micro-analyzer (EPMA) at the Cooperative Center of Kanazawa University, Kanazawa, Japan. The analyses were performed under an accelerating voltage of 20 kV and a beam current of 20 nA with a counting time limit of 40 seconds. Natural minerals and synthetic materials were used as standards. The ZAF program was used for data correction. The amounts of Fe2+ and Fe3+ contents of minerals were estimated by assuming ideal mineral stoichiometry in structural formula. Mineral abbreviations in petrographic photomicrographs and tables are taken from Whitney and Evans (2010).
Results and discussion
Petrographic studies show that the Middle Eocene Toveireh granitoid intrusive consists of granodiorite and granite. Granodiorites are coarse grained, mesocratic and have microgranular mafic enclaves in hand specimen. They are composed of plagioclase, amphibole, quartz, orthoclase and biotite. Accessory minerals are zircon, apatite, sphene and magnetite. Chlorite, actinolite, epidote and sericite are present as the secondary minerals. In the study area, the most dominant texture of the granodiorites are granular but graphic, perthite, anti-perthite, anti-rapakivi textures are common. The plagioclase (An0.8-48) occurs mainly as medium to coarse grains, subhedral, with zoning and polysynthetic twinning that represent varying degrees of saussuritization. Quartz occurs commonly as medium to fine anhedral grains. Graphic texture intergrowths of quartz and feldspars are present. Graphic texture possibly indicate rapid and simultaneous crystallization of quartz and K–feldspar from an under-cooled liquid at shallow depths (Clarke, 1992; Barker, 1983). Hornblende is present as subhedral to anhedral grains and in some cases partly altered to chlorite and actinolite. Biotites are subhedral and sometimes altered to chlorite, titanite and epidote. Based on mineral chemistry data, amphiboles in the investigated plutons are calcic in composition and classify as magnesio-hornblende and actinolite. Amphiboles are characterized by Mg# 0.67 to 0.47 and present geochemical features of subduction zone-related amphiboles. Biotite is characterized by variable and high Fe contents, with Fe# [Fe2+/(Fe2+ + Mg)] ratios between 0.52 to 0.60. Using the nomenclature scheme of Foster (1960), they are Mg-biotite, and have composition range of the calc-alkaline granites among the different granitoid suites in discriminative trend defined by Abdel-Rahman (1994). Chlorites are brunsvigite in composition and have negligible K2O and TiO2 but show similar Fe/(Fe+Mg) ratios with amphibole and biotite. Therefore, it can be concluded that they are alteration products of mafic minerals. Chlorite alteration temperature is estimated to be 245 to 262°C from chlorite geothermometry. The chemistry of hornblende and biotite imply that Toveireh granodiorites have I-Type nature and are products of crust-mantle, mixed-source magma crystallization. Barometry calculations of amphiboles indicate that these rocks were emplaced at an average pressure of 1-1.5 kbars corresponding to approximately 3.5-6 Km depth. Plagioclase-amphibole and biotite thermometry suggests an equilibrium temperature of 700 to 800°C. Estimation of Oxygen fugacity by Fe# of amphibole and biotite indicate high value of Oxygen fugacity (+1< ∆FQM < +2.0) and suggest that the Toveireh granitoids belong to the magnetite-series of granites. Petrography and mineral chemistry of the studied rocks indicated their subduction-related tectonic setting.
Acknowledgments
The authors thank the University of Isfahan and Kanazawa University for financial supports and laboratory facilities.
References
Abdel-Rahman, A., 1994. Nature of biotites from alkaline, calcalkaline and peraluminous magmas. Journal of Petrology, 35(2): 525–541.
Barker, D.S., 1983. Igneous rocks. Prentice Hall, New Jersey, 417 pp.
Castro, A., 2013. Tonalite –granodiorite suites as cotectic systems: A review of experimental studies with applications to granitoid petrogenesis. Earth-Science Reviews, 124: 68–95.
Clarke, D.B., 1992. Granitoid Rocks. Chapman and Hall, London, 283 pp.
Foster, M.D., 1960. Interpretation of the composition of the trioctahedral micas. United States Geological Survey Professional Paper, 354(B): 11-49.
Whitney, D.L. and Evans, B.W., 2010. Abbreviation for names of rock-forming minerals. American Mineralogist, 95(1): 185–187.توده نفوذی گرانیتوئیدی تویره با سن ائوسن میانی در جنوبغرب جندق و در حاشیه غربی خرد قاره شرق– ایران مرکزی قرارگرفته است. این توده نفوذی در قسمتهای جنوبی و شرقی، سنگهای آتشفشانی ائوسن را قطعکرده و خود نیز توسط بازالتهای آلکالن الیگوسن زیرین قطعشده است. سنگهای سازنده این توده نفوذی گرانیت و گرانودیوریت است که گرانودیوریتها از فراوانی بیشتری برخوردارند. کانیهای اصلی و فرعی تشکیلدهنده واحد گرانودیوریتی شامل پلاژیوکلاز، کوارتز، ارتوکلاز، آمفیبول، بیوتیت، آپاتیت، زیرکن و اسفن است. آمفیبولهای گرانودیوریتها از نوع کلسیک، با Mg# (میانگین 61/0) و ترکیب مگنزیوهورنبلند تا اکتینولیت دارند. دامنه ترکیب پلاژیوکلازهای این توده نفوذی از آلبیت تا آندزین در نوسان است و مرکز برخی از بلورهای پلاژیوکلاز ترکیب لابرادوریت دارند. بررسی شیمیکانی بیوتیتهای این توده نفوذی نشان میدهد که بیوتیتهای آن شبیه بیوتیتهای متبلورشده از ماگماهای کالکآلکالن هستند. با استفاده از دما– فشارسنجی زوج کانی هورنبلند- پلاژیوکلاز، دمای تبلور 700 – 800 درجه سانتیگراد و فشار 1- 15/1 کیلوبار (معادل عمق 5/3 – 6 کیلومتر) محاسبهشده است دماسنجی کلریتها دمای دگرسانی حدود 245- 262 درجه سانتیگراد را نشان میدهد. بررسیهای پتروگرافی و شیمیکانی بیوتیتها و آمفیبولهای توده نفوذی نشاندهنده I-Type بودن این گرانیتوئید است که از ماگمایی با منابع مختلط پوسته- گوشته شکلگرفته است. فوگاسیته بالای اکسیژن (+1< ∆FQM < +2.0) در مذاب سازنده آن شاهدی برای ارتباط آن با فرورانش است.دانشگاه فردوسی مشهدزمین شناسی اقتصادی2008-730610220190220Relation of alkali-metasomatism and Ti-REE-U (Th) mineralization in the Saghand mining district, Central Iranارتباط دگرنهادی قلیایی و کانی سازی عناصر Ti-REE-U(Th) در منطقه معدنی ساغند، ایران مرکزی4714963344510.22067/econg.v10i2.61553FAصالح دیمرشهید بهشتیمهرداد بهزادیشهید بهشتیمحمد یزدیشهید بهشتی0000-0002-7948-0478محمدرضا رضوانیان زادهسازمان انرژی اتمی ایرانJournal Article20170102Introduction
The Saghand mining district is a part of Bafq-Saghand metallogenic zone in the Central Iranian geostructural zone which is located in northeast of city of Yazd. This area is known to be more susceptible to mineralization of U and Th radioactive elements, but in fact is that its main importance is for relatively large iron deposits. However, in this region similar to some of the ore deposits within the Bafq area, rare earth elements have a high anomaly.
Alkali-metasomatism occurs in a large variety of environments and geological periods. It can be spatially associated with ore deposits, as for some IOCG deposits or exists in barren systems such as metasomatism within the ocean crust (Johnson and Harlow, 1999). Although average U and REEs contents of the ore bodies associated with alkali-metasomatism are not high, they represent a promising exploration target because the resources of such deposits are relatively large (Cuney et al., 2012). The alkali-metasomatism could take place in all kinds of rocks. In addition to wide distribution in granite and granodiorite, it could be also identified in all kinds of metamorphic rocks, pegmatites, subvolcanic and volcanic rocks, and they all have mineralization (Zhao, 2005).
Materials and methods
After field studies, host rocks and metasomatites were sampled from outcrops, trenches, and core drillings. Since the rare earth elements and radioactive elements are present within the same mineralogy (Samani, 1985), surface spectrometry measurements were used in the selection of appropriate samples. For microscopic studies, 210 samples were prepared and studied. Ore minerals were investigated in polished and polished thin sections using optical microscope and Scanning Electron Microscopy (SEM) analysis was done in the Iranian Mineral Processing Research Center. An LEO-1400 SEM with energy dispersive X-ray spectrometry and back-scatter electron (BSE) imaging capabilities was used (accelerating voltage, 17-19 kV, and beam current of 20 nA). The 16 samples were analyzed by the ICP-MS method at Zarazma Mineral Studies Company, Iran, for major and trace elements at the various radiations and lithological ranges. The detection limit and precision for determination of REE, U and Th concentration were 0.2 to 1 ppm and 1 to 0.1 ppm, respectively.
Discussion and results
Based on field evidence and microscopic studies, four main stage of metasomatism with continuous evolution have been distinguished in the Saghand area, including: 1) Na-metasomatism, 2) Ca-Mg metasomatism, 3) K-metasomatism, and 4) Epidote±chlorite±calcite±quartz vein and veinlets. All metasomatic zones are generally enriched in U and REE and compared with the host rocks but economic grades are less widespread and limited to Ca-Mg metasomatite zones near pinkish to red color albitites.
The major Ti-REE-U(Th) minerals are davidite and brannerite, which have mainly crystallized during the Ca-Mg metasomatic stage. Ti or Ti-bearing minerals as paragenesis with davidite and brannerite are also deposited in amphibole-albite metasomatic zones. All these minerals are usually fractured and along fractures and its margin is replaced by titanite, leucoxene and rutile.
In this study, geochemical analysis results of igneous rocks in the Saghand ore deposit, confirm the active continental margin arc setting and the nature of calc-alkaline magmatism in the region. The good adaptation of the REEs patterns in granites with the quartzdiorite-diorite rocks, can be a strong reason for their common tectono-magmatic origin. This Geodynamic environment had been the appropriate background in terms of protolith, heat engine for metasomatism cycle and supply hydrothermal solution and controlling structural pathways. The proximity of mineralized metasomatic rocks with the granitic rocks and intrusion of the granite apophysises into the metasomatic rocks, mobility of REE elements in the metasomatic environments, adaptation of geochemical properties of REE, U and Th elements in the mineralized metasomatitic rocks with the granitic rocks and finally, there was no evidence of intrusion of unusual magmas such as the carbonatite or alkaline magmas at the current level of ore deposit outcrops. Thesesuggest a close relationship between mineralization and metasomatic events with the granite intrusion.
Fluids differentiated from the Douzakh-Darreh granite have entered the fault and crushed zones in a tectonically active regime of marginal continental arc. Due to reaction of the high temperature fluid with the protolith rocks, the ratios of Na+/K+ and Na+/H+ in fluid in equilibrated to feldspars of protolith rock elevated (Cuney et al., 2012). A basically alkaline medium to low temperature hydrothermal fluid is a suitable environment for the activation and transfer of U and REE in the form of hydroxyl complex (Romberger, 1984). Conversely, Th remained essentially immobile during the metasomatic processes (Cuney et al., 2012) and therefore, cannot be in abundance carried by this fluid. Hematite pigmentation of albite and transfer of U shows that oxygen fugacity in the early hydrothermal fluid has been quite high. These geochemical conditions simply allow U, and REEs enter from wall rocks to fluids and form hydroxyl complex of these elements, which are sustainable and are portable. Titanium bearing minerals within the quartzdiorite-diorite rocks and Douzakh Dareh granite easily decompose under hydrothermal activity and form titanium hydroxides, which is a very strong absorbent for U. After mineralization of albite and hematite, oxidation degree of fluid quickly drops and as a result, conditions for instability of complexes containing Ti, REE and U are provided.
Acknowledgements
This paper is based on a part of the first author's Ph.D thesis at Shahid Beheshti University. This research was also supported by Skam Company and Iranian Mines & Mining Industries Development & Renovation Organization.
References
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Johnson, C.A. and Harlow, G.E., 1999. Guatemala jadeitites and albitites were formed by deuterium-rich serpentinizing fluids deep within a subduction zone. Geology, 27(7): 629–632.
Romberger, S.B., 1984. Transport and deposition of uranium in hydrothermal systems at temperatures up to 300 °C: geological implications. In: B. DeVivo, F. Ippolito, G. Capaldi and P.R. Simpson (Editors), Uranium Geochemistry, Mineralogy, Geology, Exploration and Resources. Institution of Mining and Metallurgy, London, pp. 12–17.
Samani, B., 1985. Preliminary study of ore samples from the Saghand area (Central Iran). Atomic Energy Organization of Iran, Tehran, Report 168, 17 pp. (In Persian)
Zhao, F., 2005. Alkali-metasomatism and uranium mineralization. 8th Biennial meeting, Society for Geology Applied to Mineral Deposits; Mineral deposit research meeting the global challenge, Beijing, China.منطقه معدنی ساغند بخشی از پهنه زمینساختی کاشمر- کرمان در خرده قاره ایران مرکزی است که در استان یزد واقعشده است. کانسار Ti-REE-U(Th) دگرنهادی ساغند، در مجاورت توده گرانیتوئیدی زریگان و در مجموعهای از سنگهای نفوذی نیمه عمیق دیوریتی- کوارتزدیوریتی تشکیلشده است. تحول زمانی دگرنهادی از مبدأ سنگهای میزبان، بهسمت دگرنهادهای آلبیتی، آمفیبولی و در نهایت دگرنهاد فلوگوپیتی توسعه پیداکرده است که با رگه- رگهچه های اپیدوت± کلریت± کوارتز± کلسیت قطع شدهاند. کانههای اصلی کانسار ساغند، ایلمنیت، دیویدایت، برانریت، روتیل و اسفن هستند که در دگرنهادهای آمفیبولی- آلبیتی نهشته شدهاند. سیال دگرنهادکننده منشأ تفریق ماگمایی دارد که در آغاز اکسیده و بهشدت قلیایی بوده و برای نهشت آلبیت و حمل و مجموعهسازی U و REEها بسیار مناسب بوده است. تفسیر ویژگیهای زمین شیمیایی عناصر U، Th و REE در سنگهای دگرنهادی کانهزایی شده، سنگهای مادر و گرانیتهای مجاور کانسار و نیز نبود شواهدی از نفوذ ماگماهای کربناتیتی یا آلکالن در محدوده کانسار، بیانگر وجود ارتباط میان دگرنهادی و کانهزایی با ماگماتیسم گرانیتوئیدی کالکآلکالن در منطقه است.دانشگاه فردوسی مشهدزمین شناسی اقتصادی2008-730610220190220Petrology, geochemistry and tectonic setting studies in magmatic complex generating the Takht Fe-skarn deposit, NE Hamedanمطالعات پترولوژی، ژئوشیمی و جایگاه زمین ساختی مجموعه ماگمایی مولد کانسار اسکارن آهن تخت، شمال شرق همدان4975353346810.22067/econg.v10i2.67313FAسید نعمت اله حقیقی بردینهلرستانرضا زارعی سهامیهلرستانحسن زمانیانلرستاناحمد احمدی خلجیلرستانJournal Article20170908Introduction
The Urumieh-Dokhtar Magmatic Assemblage (UDMA) forms a distinct NW-SE linear intrusive–extrusive complex Magmatism of the UDMA that occurred from Eocene to Quaternary, although the maximum activity was in the middle Eocene (Berberian and King, 1981; Ghasemi and Talbot, 2006). Collision of Arabian and Iranian plates led to termination of Neo-Tethys crust subduction and magmatism activity was abated in the UDMA, although there is no common agreement on collision timing. The Takht magmatic complex is located in the north of the Hamedan province (west Iran), and it belongs to the UDMA. The assemblage of volcano-plutonic rocks is present in the study area. The volcanic rocks include dacite, rhyodacite and trachyandesite with some tuff and agglomerated and the plutonic rocks are mostly occupied by granodiorite and diorite (containing mafic micro-granular enclaves) with some gabbro. These bodies are mostly intruded in Jurassic schists and are in contact with Cretaceous limestone leading to the formation of a skarn iron-ore deposit. The detailed geochemical and isotopic data is lacking and the age of the Takht granodiorite has not been determined. In the present study, the authors mainly have focused on the geochemistry and Sr-Nd isotopic ratios of the Takht magmatic complex to clarify questions regarding pterogenesis and its geodynamic evolution. We also reported U–Pb zircon ages for Takht granodiorite to study the relationship between its genesis and geological evolution history of the UDMA.
Materials and methods
A total of about 80 samples from the Takht plutonic-volcanic rocks were collected. 16 plutonic-volcanic samples were selected for whole-rock chemical analysis. Major element oxides were analyzed by the X-ray fluorescence spectrometry (XRF) method using an Optima 7300DV XRF instrument in the Lab West laboratory, Australia. Trace elements were also analyzed in this laboratory with the inductively-coupled plasma mass spectrometry (ICP-MS) method using a NeXION 300 ICPMS instrument. Three chip samples with equal weight (4.5 kg) were collected from the Takht granodiorite. Then upon mixing, average samples were obtained for U–Pb dating of zircon. Hand-picked zircon crystals were supplied to the ALC (Arizona Laser Chron Center) in Arizona University. The 14 selected samples for Nd-Sm and Rb-Sr isotope analysis were crushed to less than 60µm. All isotope analyses were performed on a Nu Instruments Nu Plasma HR in the MC-ICP-MS facility, in the University of Cape Town, Rondebosch, South Africa.
Results
The plutonic rocks have metaluminous nature and are of calc-alkaline affinity. The Sr/Nd, Nb/La and Th/U ratios of the granodiorite show that its magma was formed mainly by melting of continental crust, and that its enclaves were formed from a mantle derived mafic magma. The samples have negative anomalies in Nb, Sr, Ti, P and Eu and positive anomalies in Th, K, Zr, Yb and Rb thus indicating contribution of mantle and crustal materials in their generation. The Takht granodiorite has geochemical features of I and A-type granites and also shows properties of both volcanic arc and within plate magmatism association granitoids (high levels of LILEs and HFSEs). In order to obtain better results, all the data were plotted on a common 206Pb/238U versus 207Pb/235U diagram. The results show an age of 16.8 ± 0.24 Ma (Middle Miocene) for the Takht granodiorite. Based on the results, the Takht granodiorite was generated in Miocene. In the Takht magmatic complex initial 87Sr/86Sr range from 0.70678 to 0.70778 and εNd also changes from -0.79398 to -5.83370. Nd-Sm isotopic contents and trace element ratios indicate that the Takht magmatic complex has originated from oceanic slab break-off with continental crust mingling in the post-collision stage. The εNd (16.8 Ma) vs. initial 87Sr/86Sr ratios diagram reveals, the role of continental crust materials in the generation of the granodiorite samples, while where the enclaves lie are plotted in the mantle evolution array field.
Discussion
The Takht magmatic complex has geochemical properties of arc related igneous rocks such as Ba, Nb, Sr, P, Ti and Y negative anomalies and for Rb, Th, U, K, Nd and Zr positive anomalies. Most of the Takht area samples are plotted in the triple junction of volcanic arc granites (VAG), within plate granites (WPG) and syn-collision (syn-COLG) on Y versus Nb and the Y+Nb versus Rb diagrams (Pearce et al., 1984). These data suggest post-collisional tectonic setting for the Takht magmatic complex. Field, microscopic and geochemical evidences indicate that simple fractional crystallization of a mafic magma was not the only processes involved in the generation of the studied rocks. On this basis, continental crust material had extensive contribution in the generation of the granodiorites whereas the enclaves are from mantle derived magmas. Relatively high fractionated REE patterns of the granodiorite samples with high LREE/HREE indicate an amphibole-bearing, garnet-free source for the samples while small to moderate negative Eu anomalies require residual plagioclase in the source. The granodiorite samples basically have geochemical properties of I-type granites and it is confirmed by their Nd and Sr isotopic ratios. However, relatively high HFSE contents make them similar to A-type granites. Melting of a former continental arc crust and contamination with mantle derived magmas led to both volcanic arc and within plate geochemical properties of the granodiorites that make them similar to I-type and A-type granitoids. The age of 16.8 ± 0.24 Ma (Middle Miocene) of the Takht granodiorite is consistent with the other post-collisional igneous rocks of the area and regarding its post-collisional geochemical properties the age of collision and related orogeny must be considered at least before Miocene.
References
Berberian, M. and King, G.C.P., 1981. Towards a paleogeography and tectonic evolution of Iran. Canadian Journal of Earth Science, 18(2): 210–265.
Ghasemi, A. and Talbot, C.J., 2006. A new tectonic scenario for the Sanandaj–Sirjan Zone (Iran). Journal of Asian Earth Sciences, 26(6): 683–693.
Pearce, J.A., Harris, N.B.W. and Tindle, A.G., 1984. Trace element discrimination diagrams for the tectonic interpretation of granitic rocks. Journal of Petrology, 25(4): 956–983.مجموعه ماگمایی و کانسار آهن تخت در شمالشرق شهر همدان و در شمال کمربند ماگمایی ارومیه- دختر قرار دارد. این مجموعه شامل سنگهای آتشفشانی- درونی است که سنگهای آتشفشانی از داسیت، ریوداسیت، تراکیآندزیت و سنگهای آذرآواری (توف و آگلومرا) تشکیل شدهاند و سنگهای درونی بهطور غالب عبارتند از: گرانودیوریت و دیوریت آنکلاودار و بهمقدار کمتر گابرو. نفوذ تودههای درونی یادشده بهدرون آهک کرتاسه، کانیسازی آهن اسکارن کلسیک را سببشده است. سنگهای آذرین درونی اغلب از نوع متاآلومین و گروه کالکآلکالن هستند. نسبتهای Sr/Nd، Nb/La و Th/U نشان میدهد گرانودیوریت اغلب از ذوب پوسته قارهای شکلگرفته است و آنکلاوها بیشتر منشأ ماگمای مافیک جبهای را نشان میدهند. نمودارهای عنکبوتی عناصر کمیاب و REE در نمونهها دارای آنومالی منفی Nb, Sr, Ti, P و Eu و آنومالی مثبت در Th, K, Yb و Rb بوده که بیانگر نقش مواد جبهای و پوستهای در منشأگیری ماگماست. ویژگیهای همزمان گرانیتوئیدهای I و A و نیز ویژگی ماگماتیسم درون و حاشیه قاره نشان میدهد، ماگمای تخت هیبریدی است و امکان حضور همزمان مذابهای گوشتهای و پوستهای وجود دارد (سطح بالایی از LILEs وHFSEs). سنسنجی U-Pb زیرکن برای توده گرانودیوریتی، سن 2/0 ± 8/16 میلیون سال (دوره میوسن) را نشان میدهد. در مجموعه ماگمایی تخت مقادیر ایزوتوپ اولیه 87Sr/86Sr بین 70678/0 تا 70778/0 در هزار است و مقدار εNd نیز مقادیر منفی داشته و بین 79398/0- تا 83370/5- هستند. ویژگیهای ایزوتوپی Sr و Nd نشان از منشأگرفتن مجموعه ماگمایی تخت از پوسته اقیانوسی شکستهشده همراه با آلایش پوسته قارهای در مرحله پس از برخورد است. نتایج این پژوهش نشان میدهد برخورد صفحه عربی و ایران قبل از میوسن رخداده و ماگماتیسم در کمربند ماگمایی ارومیه- دختر بعد از بستهشدن نئوتتیس نیز ادامه داشته است؛ بهطوریکه بررسیهای ایزوتوپی، سنسنجی و ژئوشیمیایی منطقه مورد بررسی که بخشی از کمربند ارومیه- دختر شمالی محسوب میشود، بیانگر این موضوع است.
دانشگاه فردوسی مشهدزمین شناسی اقتصادی2008-730610220190220Distribution of Potentially Toxic Elements in the Tailings, Mine and Agricultural Soils around the Irankuh Pb-Zn Mine, SW Esfahanبررسی توزیع عناصر بالقوه سمّی در باطله های فراوری، خاک های معدنی و کشاورزی محدوده معدنی سرب- روی ایرانکوه، جنوب غرب اصفهان5375593348610.22067/econg.v10i2.62158FAمژده داودی فردصنعتی شاهرودگیتی فرقانی تهرانیصنعتی شاهرود0000-0002-6644-5120هادی قربانیصنعتی شاهرودحبیب الله قاسمیدانشگاه صنعتی شاهرودJournal Article20170128Introduction
Pollution of soils with potentially toxic elements (PTEs) is one of the most important hazards threatening the health of natural ecosystems. In recent decades, the anthropogenic activities have led to the disruption of the geochemical and biochemical circles of these elements. Mining activities are one of the most important anthropogenic sources for PTEs. The mine tailings are the most important pollution sources of surrounding soils and groundwater (Ferreira da Silva et al., 2004; Boularbah et al., 2006). Indeed, agricultural activities have a significant impact on the soil pollution with PTEs (Keskin, 2010). Soil plays a vital role in human life. Thus, the monitoring and assessment of soils pollution is of great importance. The Irankuh Pb-Zn mine, located in the SW of Esfahan, is one of the most important mines of Iran. Mining and subsequent processing of ores in this region generates high volumes of mine wastes which are deposited near the mine site. On the other hand, agricultural activities in the Irankuh area are extensive and the mine's tailing ponds usually neighbor the farms. The present study aims to investigate the concentration, mobility and availability of PTEs in the Irankuh mine tailings and to determine the source of these pollutants in the surrounding soils.
Material and Methods
After the preliminary field studies, 28 soil samples including 8 mine- and 20 agricultural soils as well as two representative tailing samples were collected. One manure sample was also collected to identify the impact of agricultural activities on the concentration of PTEs in the soils, if any. First, the soil samples were air-dried at room temperature. Then, the large fragments and plant residuals were removed from the samples and the remaining portion was passed through a 2 mm stainless steel sieve. The sieved samples were ground to about 0.074 mm using an agate mortar and pestle and finally stored in polyethylene bags prior to laboratory analysis. The total concentrations of elements were measured by ICP-OES instrument after digesting by strong acids. The five-stage method of Tessier et al. (1979) was employed for sequential extraction analysis. In order to assess the pollution of the soils and tailings, the enrichment factor was calculated. Having obtained the results of the analysis, descriptive and multivariate data analyses were conducted.
Results and discussion
The average concentration of Ag, As, Ba, Cd, Co, Mn, Pb, Sb and Zn in the mine soils are higher than the agricultural soils. The application of manure to the agriclutural soils led to increase in Cu and Cr concentration of the soils; the high concentration of these two elements in the manure sample is indicative. The concentration of Ag, As, Cd, Ba, Pb, Ni, Zn and Sb in both agricultural and mine soils are higher than the average world soil composition (Kabata-Pendias, 2011), pointing to the impact of anthropogenic activities on the PTEs concentrations in the soils. The tailing samples are highly encirched with respect to As, Cd, Cu, Sb, Mn, Pb and Zn. Enrichment factor values confirms pollution of soils with respect to Ag, As, Cd, Pb, Sb and Zn. Tailing samples are also extremly contaminated by these elements.
On the basis of the analysis of variance, there is a significant statistical difference between the element concentrations in mine and in agricultural soils. The cluster analysis indicates the impacts of mining activity on the PTEs concentrations in soils. On the basis of principal component analysis, the elements originate from three sources: 1- geogenic stable elements 2- anthropogenic elements and 3- the weathering products of carbonate units. Total concentrations of PTEs provide no information on their likely environmental impacts. The speciation studies through sequential extraction analysis could be used to determine the mobility and availability of PTEs. By employing sequential extraction procedure, it is possible to predict occurrence manner, mobility, solubility, bioavailability, toxicity and transport as well as the origin of PTEs (Favas et al., 2011). The results show that, on the average, 24.9, 20.3, 18.6, and 15.2 % of Cu, Mn, Cd and As, respectively, are present as exchangeable fraction. Therefore, the weathering of mine tailings may increase the bioavailability of these elements in agricultural soils and groundwater around the mining area. The mobility of arsenic and iron is lower than other studied elements. Chromium and nickel are not mobile.
Acknowledgement
This research has been funded by the Research Office of the Shahrood University of Technology.
References
Boularbah, A., Schwartz, C., Bitton, G. and Morel, J.L., 2006. Heavy metal contamination from mining sites in South Morocco: 1. Use of a biotest to assess metal toxicity of tailings and soils. Chemosphere, 63(5): 802–810.
Favas, P.J.C., Pratas, J., Gomez, M.E.P. and Cala, V., 2011. Selective chemical extraction of heavy metals in tailings and soils contaminated by mining activity. Journal of Geochemical Exploration, 111(3): 160–171.
Ferreira da Silva, E., Zhang, C., Serrano Pinto, L., Patinha, C. and Reis, P., 2004. Hazard assessment on arsenic and lead in soils of Castromil gold mining area, Portugal. Applied Geochemistry, 19(6): 887–898.
Kabata-Pendias, A., 2011. Trace Elements in Soils and Plants. Chemical Rubber Company Press, BocaRaton, Florida, 413 pp.
Keskin, T., 2010. Nitrate and heavy metal pollutin resulting from agricultural activity: a case study from Eskipazar (Karaabuk, Turkey). Environmental Earth Sciences, 61(4): 703–721.
Tessier, A., Campbell, P.G.C. and Bisson, M., 1979. Sequential extraction procedure for the speciation of particulate trace metals. Analytical Chemistry, 51(7): 844–851در این پژوهش، غلظت، تحرک و دسترسپذیری عناصر بالقوه سمی در باطلههای فراوری و همچنین منشأ آنها در خاکهای اطراف معدن سرب- روی ایرانکوه ارزیابیشده است. نتایج حاصل از تحلیل واریانس نشان میدهد که تفاوت آماری شاخصی بین غلظت عناصر در خاکهای معدنی و کشاورزی وجود دارد. آنالیز خوشهای نیز نشاندهنده تأثیر معدنکاری بر افزایش غلظت PTEs در خاک است. بر اساس نتایج تحلیل مؤلفه اصلی، عناصر دارای سه منشأ است: 1- عناصر پایدار زمینزاد؛ 2- عناصر انسانزادی که نشاندهنده ژئوشیمیایی کانهزایی سرب و روی هستند و 3- محصولات هوازدگی واحدهای کربناتی. آنالیز عنصری باطلههای فراوری، نشاندهنده غنیشدگی شدید باطلهها نسبت به آرسنیک، کادمیم، آنتیموان، روی و سرب است. نتایج آنالیز استخراج ترتیبی نشان میدهند که درصد نسبتاً بالایی از مس، منگنز، کادمیم و آرسنیک (بهترتیب 9/24، 3/20، 6/18 و 2/15 درصد) به شکل تبادلپذیر حضور دارد. بنابراین، فرسایش باطلههای فراوری میتواند زیستدسترسپذیری این عناصر را در خاک کشاورزی و آبهای زیرزمینی اطراف محدوده معدنی افزایش دهد.دانشگاه فردوسی مشهدزمین شناسی اقتصادی2008-730610220190220Physicochemical Attributes of Parental Magma in Collisional Porphyry Copper Systems; Using Biotite Chemistry, Case Study: Chahfiruzeh Porphyry Copper Depositتعیین شاخصه های فیزیکوشیمیایی ماگمای مولد در سامانه های پورفیری برخوردی با استفاده از شیمی بیوتیت: مطالعه موردی کانسار مس پورفیری چاه فیروزه5615863351110.22067/econg.v10i2.65652FAمجید حیدریشهید چمران اهوازعلیرضا زراسوندیشهید چمران اهواز0000-0001-9821-6747محسن رضاییشهید چمران اهواز0000-0002-3380-0632یوهان رایتمونتانعادل ساکیشهید چمران اهوازJournal Article20170702Introduction
Almost all of the well-known porphyry copper deposits in Iran occur within the Kerman Cenozoic magmatic arc (KCMA) (Fig 1) in the southeastern part of Cenozoic Urumieh–Dokhtar magmatic belt (Hassanpour et al., 2015). The Miocene Chahfiruzeh porphyry copper deposit as an example of collisional porphyry intrusion is located in the Kerman Cenozoic magmatic arc (Fig 2) (Einali et al., 2014). In this research, we attempt to characterize the physicochemical attributes of parental magma in the Chahfiruzeh porphyry deposit, using chemistry of magmatic biotite.
Materials and methods
Samples from various rocks were collected from drill cores belonging to 123.1-667.1m depths. The chemical compositions of magmatic biotites were obtained by analyzing the carbon coated polished thin sections using electron probe microanalyzer (EPMA). All samples were prepared and analyzed in the Montanuniversität Leoben, Austria using a superprobe Jeol JXA 8200 instrument. The analyses were conducted with 15 kV accelerating voltage and 10 nA beam and beam size of about 1 μm. The counting times (upper and lower) were 100 and 20 s, respectively.
Results
Chahfirouzeh porphyry deposit containing 100 Mt ore reserves (Mohammaddoost et al., 2017), and 0.4-0.8% Cu is located at the 95 km NW of Sarcheshmeh deposit and 35 km NE of Shahr-e- Babak in the Kerman province. (Einali et al., 2014). The compositions of analysed magmatic biotites from the Chahfiruzeh porphyry copper deposit are summarized in Table 1. According to (Mg–Li) vs. (Fetot + Mg + Ti–AlVI) and Mg–(Fe2+ + Mn)–(AlVI + Fe3+ + Ti) diagrams, the biotite from Chahfiruzeh deposit are Mg-rich (Fig. 5-A,B). Chemical compositions of biotites on the ternary diagram of Beane (1974) shows a magmatic origin for the analysed samples (Fig 7). Magmatic biotites are characterized by high SiO2 values ranging from 37.44-44.71 (Wt. %). Also, MgO and FeO vary between 12.54-14.36 (Wt. %) and 14.94-16.3 (Wt.%), respectively. Moreover, TiO2, K2O, and Na2O range from 4.53-5.97, 8.3-9.38, 0.15-0.29 (Wt.%), respectively (Fig 6-A-D). Fluorine and Cl contents in biotite range from 0.3 to 1.52 wt.% and 0.03 to 0.04 wt.%, respectively.
Discussion
Chemical compositions of selected biotites on the classification diagrams of Abdel-Rahman (1994) indicate that magmatic biotites from the Chahfiruzeh porphyry copper deposit belong to calc-alkaline (C) series (Fig. 8). Also, according to ternary Xpdo-Xan-Xph diagram (Wones and Egster , 1965), Oxygen fugacities of Chhfiruzeh and other pre-collisional porphyry deposits (e.g., Reagan) occur in NNO distinct (Fig 9). It is evident that granitic rocks of both studied deposits are formed in relatively similar oxidiant conditions. Moreover, the preformed geothermometry on the magmatic biotites in the Chahfiruzeh porphyry the copper deposit shows a range of temperatures between 478-632 ° C (average 565.3 °C). Moreover, XMg/XFe values confirm that Mg is enriched in Chahfiruzeh (collisional porphyry) compared to that of Reagan (pre-collisional porphyry; Fig 10-A). Also, fluorine has the highest concentration in collisional porphyry copper deposits. The plot of the Chahfiruzeh biotites on the log (XMg/ XFe) versus log (XF/XOH) discrimination diagram of Brimhall and Crerar (1987) represent that the intrusion crystallized from a weakly to strongly crustal-contaminated, I-type granitic magma (Fig 11). The log fH2O/fHF and fH2O/fHCl ranges between 4.69-4.84 and 4.09-4.28 having an average value of 5.14 and 4.14, respectively (Table 1). According to XFe vs. XF/XOH and XCl/XOH, Cl fugacities in Chahfiruzeh are analogous to that of Reagan porphyry (Fig 12). The calculated halogen fugacity ratios (log fH2O/fHCl vs. log fH2O/fHF and fHF/fHCl) and log fH2O/fHCl vs. IV(Cl) of magma in equilibrium with biotite for Chahfiruzeh porphyry and comparison with Reagan and other known porphyry of the world show that Chafiruzeh and Ragan deposits are analogous to those of Sarcheshmeh and Bingham porphyry deposits (Fig 13 and 14). Finally, Chahfiruzeh deposit as collisional porphyry has higher IV(F) than Reagan deposit (pre-collisional). In comparison with collisional porphyry copper systems (Chahfiruzeh), poor mineralization in the Reagan pre-collisional deposit may be due to lower Cl content of the magma in Reagan deposit.
Acknowledgements
This research was made possible by the help of the office of vice-chancellor for Research and Technology, Shahid Chamran University of Ahvaz. We acknowledge their support. Authors highly appreciate the efforts of Prof. Johann. Raith and Dr. Federica Zaccarini for EMPA analysis. We also gratefully acknowledge the staff of the National Iranian Copper Industries Company (NICICO), for helping us in sampling.
References
Abdel-Rahman, A.M., 1994. Nature of biotites from alkaline, calc-alkaline, and peraluminous magmas. Journal of Petrology, 35 (2): 525–541.
Beane, R.E., 1974. Biotite stability in the porphyry copper environment. Economic Geology, 69(1): 241–256.
Brimhall, G.H. and Crerar, D.A., 1987. Ore fluids: magmatic to supergene. Reviews in Mineralogy and Geochemistry, 17(1): 235–321.
Einali, M., Alirezaei, S. and Zaccarini, F., 2014. Chemistry of magmatic and alteration minerals in the Chahfiruzeh porphyry copper deposit, south Iran: implications for the evolution of the magmas and physicochemical conditions of the ore fluids. Turkish Journal of Earth Sciences, 23(1): 147–165.
Hassanpour, Sh., Alirezaei, S., Selby, D. and Sergeev, S., 2015. SHRIMP zircon U–Pb and biotite and hornblende Ar–Ar geochronology of Sungun, Haftcheshmeh, Kighal, and Niaz porphyry Cu–Mo systems: evidence for an early Miocene porphyry-style mineralization in northwest Iran. International Journal of Earth Sciences, 104(1): 45–59.
Mohammaddoost, H., Ghaderi, M., Kumar, T.V, Hassanzadeh, J. and Alirezaei, S., 2017. Holly J. Stein e,f, E.V.S.S.K. BabuZircon U–Pb and molybdenite Re–Os geochronology, with S isotopic composition of sulfides from the Chah-Firouzeh porphyry Cu deposit, Kerman Cenozoic arc, SE Iran. Ore Geology Reviews, 88 (1): 384–399.
Wones, D.R. and Eugster, H.P., 1965. Stability of biotite: experiment, theory, and application. American Mineralogist, 50(1): 1228–1272.کانسار مس پورفیری چاه فیروزه از جمله کانسارهای مربوط به مراحل انتهایی فرورانش- برخورد در زون ماگمایی ارومیه- دختر و در ارتباط با واحدهای سنگی دیوریت/ گرانودیوریت تا کوارتزمونزونیت با سن میوسن پایانی در کمان ماگمایی سنوزوئیک کرمان است. هدف از این پژوهش بهرهگیری از شیمی بیوتیتهای ماگمایی برای بررسی شاخصهای فیزیکوشیمیایی ماگمای کانسار چاه فیروزه و مقایسه با پورفیریهای پیش از برخوردی (پورفیری ریگان) است. دماسنجی بیوتیت در پورفیری چاه فیروزه، کمینه و بیشینه 478 تا 632 درجه سانتیگراد و میانگین دمایی 3/565 درجه سانتیگراد را نشان می دهند. بر مبنای شیمی بیوتیتهای ماگمایی، شرایط فوگاسیته اکسیژن در ماگمای مادر چاه فیروزه در محدوده نیکل- نیکل اکسید قرار دارد که مطابق با شرایط فوگاسیته اکسیژن در کانسار ریگان است.log fH2O/fHF و log fH2O/fHCl, برای کانسار چاه فیروزه بهترتیب 69/4-84/4 و 09/4-28/4 با میانگین 14/5 و 14/4 است که بیانگر آب بالاتر سیالات اولیه نسبت به محتوای هالوژنی است. افزایش نسبی F در پورفیری چاه فیروزه نسبت به ریگان را میتوان ناشی از غنیشدگی این سامانه پورفیری از منیزیم دانست. نمودارهای XFe و XMg در مقابل XF/XOH و XCl/XOH در چاه فیروزه و ریگان نشانداد که با وجود افزایش اندک کلر در کانسار چاه فیروزه، هر دو پورفیری برخوردی و پیش از برخوردی، تحت شرایط فوگاسیته کلر تقریباً یکسان شکل گرفته اند. مقایسه نسبت fH2O/fHCl در مقابل fHF/fHCl و fH2O/fHF در چاه فیروزه و ریگان با سایر پورفیریهای جهان، نزدیکی این کانسارها با کانسار سرچشمه و مس Santa Rita را نشانداد. همچنین fH2O/fHCl در مقابل IV(Cl) نشاندهنده شباهت فوگاسیته هالوژنی کانسار چاه فیروزه با مس پورفیری بینگهام است. مقادیر IV(F) و IV(Cl) و IV(F/Cl) تأیید می کنند که پورفیری چاه فیروزه به همراه ریگان در زمره توده های مس پورفیری کانه زا قرار میگیرند. افزایش اندک کلر در نمونههای چاه فیروزه نسبت به ریگان را شاید بتوان مستندی در رابطه با عدم کانهزایی قابلتوجه در پورفیری پیش از برخوردی ریگان دانست.دانشگاه فردوسی مشهدزمین شناسی اقتصادی2008-730610220190220Geochemistry, mineralization and alkali-Fe oxide alteration of the Lake Siah iron±apatite deposit (northeastern Bafq), Bafq-Saghand metallogenic provinceژئوشیمی، کانه زایی و دگرسانی قلیایی- اکسیدآهن در کانسار آهن± آپاتیت لکه سیاه (شمال شرق بافق)، ایالت فلززایی بافق- ساغند5876163352910.22067/econg.v10i2.63377FAمهین رستمیبوعلی سیناابراهیم طالع فاضلبوعلی سینا0000-0002-8776-1405Journal Article20170319Introduction
Ore deposits of the Bafq-Saghand metallogenic province (IRAN) with Proterozoic age represent that they belong to classic genetic model for hydrothermal iron oxide (Cu, Au, U, REE) deposits, which is widely referred to as iron oxide copper-gold (IOCG) and iron oxide-apatite (IOA) deposits (Samani, 1988; Daliran et al., 2007; 2010; Jami et al., 2007; Nabatian et al., 2015; Rajabi et al., 2015). According to the structural zone of Iran, the Bafq mining district is part of Central Iran and therein Kashmar-Kerman tectonic zone (Zarigan-Chahmir basin), and Lake Siah deposit occurs in Early Cambrian Volcano-Sedimentary Sequence (ECVSS). According to Förster et al. (1988) and Torab (2008), the Bafq mining district is composed of a huge volcanic suite in which sedimentary structures, fossils, and even glassy volcanics a surprisingly are well preserved. Calderas are important features in all volcanic environments and are commonly the sites of geothermal activity and mineralization (Cole et al., 2005). The Lake Siah iron±apatite deposit is located between Kusk and Esfordi deposits and 40 km northeastern Bafq (31°46´47² N and 55°42´56² E).
Materials and methods
A total of 50 samples were collected from the Lake Siah mine district. Ten samples of least-altered igneous rocks were analyzed for major, trace and rare earth elements by inductively coupled plasma spectrometry (ICP-MS), and X-ray fluorescence (XRF) at the Acme laboratory (Canada). The detection limit for major oxide analysis is 0.01%. Electron microprobe analyses (EMPA) and backscattered electron (BSE) images of minerals were obtained using a Cameca SX100 electron microprobe at the Iran Mineral Process and Research Center (IMPRC). An accelerating voltage of 15 to 25 kV and beam current of 20 mA was used for all analyses.
Results and discussion
The Lake Siah deposit with a covering area of about 5 km2 is located in the Central Iran Block and therein Kashmar-Kerman tectonic zone (Zarigan-Chahmir basin). The Nb/Y versus Zr/TiO2 diagram shows a typical trend from rhyolite and evolving to andesite/trachyandesite compositions, with few data plotting in the dacite/rhyodacitic rocks. Most of the igneous rocks plot within the high-potassic calc-alkaline to shoshonitic fields in the Th/Yb versus Ta/Yb diagram (Pearce, 1983). All studied rocks show similar incompatible trace element patterns with an enrichment of large ion lithophile elements (LILE: K, Rb, Ba, Th) and depletion of high field strength elements (HFSE: Nb and Ti), which are typical features of magmas from convergent margin tectonic settings. The Lake Siah deposit is composed of the hematite and magnetite as major minerals and apatite, goethite, pyrite and chalcopyrite as minor minerals. The deposit is controlled by NE-SW normal faults and occurs within early Cambrian trachyte, trachyandesite and rhyolite of the Lake Siah caldera. Intermediate argillic, sodic (albitic), silisic, potassic-calcic, hydrolytic (acidic), and sodic-calcic (Fe) alterations occur near the ore deposit. Lipman (1992) identifies a number of stages in the development of a caldera which includes: 1) pre-collapse volcanism, 2) caldera subsidence, 3) post-collapse magmatism and resurgence, and 4) hydrothermal activity and mineralization. Flow of dacite and andesite into the shallow magmatic system is facilitated by regional fault systems which provide pathways for magma ascent. Dacite and remobilized rhyolite rise buoyantly to form domes by collapse of the chamber roof and producing surface resurgent uplift. The resurgent deformation caused by magma ascent fractures the chamber roof, increasing its structural permeability and allowing rhyolite magmas to intrude and/or cause eruption. Explosive eruption of high viscosity magma is the cause of creating fractures and breccia in the host rocks and facilitated percolation Fe-P bearing magmatic fluids.
References
Cole, J.W., Milner, D.M. and Spinks, K.D., 2005. Calderas and caldera structures: a review. Earth Science Reviews, 69(1): 1–26.
Daliran, F., Stosch, H.G. and Williams, P., 2007. Multistage metasomatism and mineralization at hydrothermal Fe oxide-REE-apatite deposits and apatitites of the Bafq District, Central-East Iran. In: C.J. Andrew (Editor), Proceedings of the 9th Biennial Society for Geology Applied meeting, The Society for Geology Applied, Dublin, pp. 1501–1504.
Daliran, F., Stosch, H.G., Williams, P., Jamali, H. and Dorri, M.B., 2010. Early Cambrian iron oxide- apatite-REE (U) deposits of the Bafq District, east-central Iran. In: L. Corriveau and H. Mumin (Editors), Exploring for Iron Oxide Copper–gold deposits: Canada and global analogues. Geological Association of Canada, Canada, pp. 147–160.
Förster, H., Knittel, U. and Sennewald, S., 1988. Resurgent cauldrons and their mineralization, central Iran. Economic Geology, 74(6): 1485–1510.
Jami, M., Dunlop, A.C. and Cohen, D.R., 2007. Fluid inclusion and stable isotope study of the Esfordi apatite–magnetite deposit, Central Iran. Economic Geology, 102(6): 1111–1128.
Lipman, P.W., 1992. Ash-flow calderas as structural controls of ore deposits-recent work and future problems. United State Geological Survey Bulletin, 104(2): 32–39.
Nabatian, G., Rastad, E., Neubauer, F., Honarmand, M. and Ghaderi, M., 2015. Iron and Fe-Mn mineralization in Iran: implications for Tethyan metallogeny. Australian Journal of Earth Siences, 62(2): 211–241.
Pearce, J.A., 1983. Role of the sub-continental lithosphere in magma genesis at active continental margins. In: C.J. Hawkesworth and M.J. Norry (Editors), Continental Basalts and Mantle Xenoliths. The Royal Society, London, pp. 230–249.
Rajabi, A., Canet, C., Rastad, E. and Alfonso, P., 2015. Basin evolution and stratigraphic correlation of sedimentary-exhalative Zn-Pb deposits of the Early Cambrian Zarigan-Chahmir Basin, Central Iran. Ore Geology Reviews, 64(1): 328–353.
Samani, B., 1988. Metallogeny of the Precambrian in Iran. Precambrian Research, 39(1): 85–106.
Torab, F.M., 2008. Geochemistry and metallogeny of magnetite-apatite deposits of the Bafq mining district, central Iran. Unpublished Ph.D. Thesis, Technical University of Clausthal, Clausthal, Germany, 131 pp.کانسار آهن±آپاتیت لکهسیاه در ایالت فلززایی بافق- ساغند و پهنه ساختاری ایران مرکزی قرار دارد. کانسار لکهسیاه طی اواخر کامبرین پیشین در ارتباط با فعالیتهای مجموعه کالدرایی لکهسیاه شکلگرفته است که مجموعه سنگهای پیروکلاستیک، آندزیت/ تراکیآندزیت و ریولیت سنگ میزبان ذخیره را تشکیل میدهند. بر اساس نسبت Th/Yb (بین 7/2 تا 17) و Ta/Yb (بین 33/0 تا 8/1)، ریولیتهای میزبان کانیسازی جزو دستههای ماگمایی کالکآلکالن غنی از پتاسیم تا شوشونیتی قرار میگیرند. طبق شواهد بهنظر میرسد تبلور ماگمای ریولیتی پر آب موجب آزادشدن حجم زیادی از عناصر فرار شده که به افزایش گرانروی ماگمای باقی مانده منجر میشود. در این شرایط، سیال احیایی با شوری و دمای بالا که حاوی لیگاندهای کلریدی حامل آهن و فسفر بوده، به سمت بالا و مناطق کم فشار حرکت می کند. فورانهای انفجاری تشکیلدهنده کالدرا، شکستگی و سیستم گسلی مناسبی برای تهنشست ماده معدنی و رخداد کانهزایی فراهمکرده است. شواهدی مثل: 1- وجود هالههای دگرسانی قلیایی غنی از کلر (مانند سدیک و سدیک- کلسیک و پتاسیک- کلسیک) در اطراف کانسنگ آهن، 2- وجود سنگهای ماگمایی پتاسیم بالا مرتبط با یک سیستم کالدرایی فعال و 3- تهیشدگی عناصری نظیر Ti، V، Al و Mn در ترکیب شیمیایی مگنتیتها، گویای وجود منبع گوشتهای دگرنهادی در منطقه لکهسیاه بوده که اغلب طی تکوین و جایگیری با سنگهای پوستهای اطراف نیز دچار آغشتگی شدهاند.دانشگاه فردوسی مشهدزمین شناسی اقتصادی2008-730610220190220Mineralization, fluid inclusions and genesis of the Bagher Abad and Darreh Badam fluorite ore deposit, southeast of Mahallatمطالعه کانی سازی، میان بارهای سیال و شرایط رخداد کانسارهای فلوریت باقر آباد و دره بادام، جنوب شرق محلات6176373354910.22067/econg.v10i2.61971FAسید جواد مقدسیپیام نورابراهیم طالع فاضلبوعلی سینا0000-0002-8776-1405عالیه سادات بنی فاطمیپیام نورJournal Article20170120Introduction
Fluorite ore deposits are classified into three main groups: (1) magmatic deposits, (2) structures related deposits, and (3) sedimentary deposits (Dill, 2010). More than 30 fluorite occurrences with approximately 1.35 million tons of reserves have been recognized in Iran (Miller, 2014). Bagher Abad and Darreh Badam fluorite ore deposits, located in the southeast of Delijan (Markazi province) occur between the central Iran structural zone from the north and the Sanandaj-Sirjan structural zone from the south. The geology of the area is dominated by folded and faulted structures of Jurassic carbonates and shales (Thiele et al., 1968). The main host rocks for fluorite mineralization in the studied area are the Lower-Upper Jurassic carbonates and shales of Shemshak and Badamu Formations.
Materials and Methods
In this study, 70 samples from the various rock types including fluorite veins, host rocks and related alterations were collected. 25 thin- and polished thin-sections were prepared and studied to explain the mineralogy and paragenetic sequence of the ore body. Eight double-polished sections were also prepared for micro-thermometric analysis. The micro-thermometric analyses were conducted on primary fluid inclusions using Linkam THM600 heating-freezing stage connected to a TMS94 temperature controller and a liquid nitrogen pump (LNP) cooling system.
Results
The main host rocks for fluorite mineralization in the studied area are composed of the lower Jurassic slate and phyllite (Shemshak Formation) and the Middle to Upper Jurassic dolomitic limestone and calcareous sandstone (Badamu Formation). The main alterations associated with fluorite mineralization are sericitization, silicification and argillization.
According to the fluid inclusions data, fluorite mineralization in Bagher Abad and Darreh Badam deposits were precipitated because of pressure reduction of ore bearing fluids and mixing of a primary moderate-salinity brine with less saline meteoric water. Estimation of trapping pressure-temperature of the mineralizing fluid in Bagher Abad fluorite deposit using the intersecting CO2 and H2O isochors for aqueous, aqueous-carbonic and carbonic fluid inclusions indicated that fluorite mineralization occurred at 180-260°C and 1-2 kbar pressure.
According to the present study, circulation and upward flow of hydrothermal fluids (containing H2O and CO2) that originated from underlying altered bedrock provided appropriate conditions for increasing the solubility of metals and formation of halide (Cl¯ and F¯) metal complexes. Reaction with wallrock and gradual decrease in temperature due to mixing and dilution of the above-mentioned fluids with low-salinity meteoric water resulted in fluorite mineralization in favorable structures such as veins.
Discussion
Bagher Abad and Darreh Badam fluorite ore deposits are examples of epigenetic mineralizations which are not related to igneous activities in Iran. The mineralization is formed in nearly vertical veins, which are relevant to local fractures hosted in the Lower-Upper Jurassic carbonates and shales with east-west trend. The main ore textures are open-space fillings, breccias, veins and cavities associated with sericitic, silicic and argillic alterations.
Micro-thermometric measurements were carried out on primary fluid inclusions in fluorite, calcite and barite minerals from both Bagher Abad and Darreh Badam deposits. Three types of fluid inclusions were distinguished: (1) two phase aqueous fluid inclusions (LV), (2) liquid (L) or vapor (V) mono phase inclusions, and (3) aqueous-carbonic (L1+L2+V) fluid inclusions.
The first ice melting temperatures (Te) of two phase aqueous inclusions (LV) in fluorite, calcite and barite from Bagher Abad and Darreh Badam deposits vary between -32 to -15°C and -35 to -24°C, respectively, which represents a H2O+NaCl±KCl multiphase fluid (Van den Kerkhof and Hein, 2001). The last ice melting temperatures (Tmice) vary between -10.5 to -2.3°C and -12.0 to -5.6°C which are equal to salinities of 5.6-14.7 and 8.3-15.2 wt% NaCl equivalent for Bagher Abad and Darreh Badam deposits, respectively. The final homogenization temperatures (Thtotal) vary between 127 to 188 °C and 176 to 270°C for Bagher Abad and Darreh Badam deposits, respectively. The CO2 melting temperatures (TmCO2) of aqueous-carbonic inclusions in fluorite, calcite and barite show a range of -58.3 to -56.6°C which suggests CH4 and/or N2 impurities (Burruss, 1981). The clathrate melting temperatures (Tmclath) ranging from -6.0 to +1.0°C represent salinities between 5.5 to 18.2 wt% NaCl equivalent for both Bagher Abad and Darreh Badam fluorite deposits.
References
Burruss, R.C., 1981. Analysis of phase equilibria in C–O–H–S fluid inclusions. In: L.S. Hollister and M.L. Crawford (Editors), Fluid inclusions: applications to petrology. Mineralogical Association of Canada Short Course Series, Ontario, pp. 39–74.
Dill, H.G., 2010. The chessboard classification scheme of mineral deposits: mineralogy and geology from aluminum to zirconium. Earth-Science Reviews, 100(1): 1–420.
Miller, M.M., 2014. Fluorspar. In: S.M. Kimball (Editor), Mineral commodity summaries 2014. U.S. Geological Survey, Reston, Virginia, pp. 56–57.
Thiele, O., Alavi, M., Assefi, R., Hushmand-zadeh, A., Seyed-Emami, K. and Zahedi, M., 1968. Explanatory text of the Golpaygan quadrangle map, scale 1:250,000. Geological Survey of Iran, Geological quadrangle E7, Tehran, 24 pp.
Van den Kerkhof, A.M. and Hein, U.F., 2001. Fluid inclusion petrography. Lithos, 55(1–4): 27–47.کانسارهای فلوریت باقرآباد و دره بادام در جنوبشرق محلات (استان مرکزی)، نمونهای از ذخایر اپیژنتیک در ایران محسوب میشوند. کانیسازی بهصورت رگههایی با شیب تقریبی قائم و در ارتباط با شکستگیهای محلی با راستای شرقی- غربی در سنگ میزبان کربناتی- شیلی با گستره زمانی ژوراسیک زیرین تا میانی شکلگرفته است. ساخت و بافتهای پرکننده فضای خالی، برشی و حفرهای همراه با دگرسانیهای دماپایین سرسیتی، سیلیسی و آرژیلیک در این ذخایر دیده میشوند. طبق شواهد بهدست آمده، میانبارهای سیال بر مبنای فازهای تشکیلدهنده، بهترتیب فراوانی شامل سه نوع: 1- میانبارهای دوفازی آبگین غنی از مایع (L+V)، 2- میانبارهای تکفاز مایع (L) و گاز (V) و 3- میانبارهای آبگین- کربنیک حاوی فاز CO2 (L1+L2+V)، در کانیهای فلوریت، باریت و کلسیت هستند. با استفاده از تقاطع منحنیهای همچگال در میانبارهای آبگین و آبگین- کربنیک، کانیسازی فلوریت در کانسار باقرآباد در فشار تقریبی 1 تا 2 کیلوبار و دمای 180 تا 260 درجه سانتیگراد تشکیلشده است. در کانسارهای باقرآباد و درهبادام سیالات گرمابی H2O+CO2 بالاآمده از سنگ بستر دگرسانشده، شرایطی مناسب برای افزایش انحلالپذیری فلزات و تشکیل کمپلکسهای هالیدی (Cl¯ و F¯) فراهم کردهاند. شورابههای یادشده طی واکنش با سنگ دیواره و کاهش دمای تدریجی سیال ناشی از رقیقشدگی با آبهای جوی، کانیسازی رگهای فلوریت در فضای مناسب را ایجاد کردهاند.دانشگاه فردوسی مشهدزمین شناسی اقتصادی2008-730610220190220Geophysical signatures of the gold rich porphyry copper deposits: A case study at the Dalli Cu-Au porphyry depositویژگی های ژئوفیزیکی کانسارهای مس پورفیری غنی از طلا: مطالعه موردی در کانسار مس- طلای پورفیری دالی، استان مرکزی6396753356810.22067/econg.v10i2.69539FAمسلم فاتحیصنعتی اصفهانهوشنگ اسدی هارونیصنعتی اصفهانJournal Article20171219Introduction
Geophysical exploration is an inexpensive, fast and efficient tool to provide valuable information about the sub-surface geological complications (Dentith and Mudge, 2014). Modern geophysical methods are widely used to identify and characterize porphyry copper deposits on various scales (Holden et al., 2011; Hoschke, 2011; Clark, 2014). It is often an indirect exploration method; therefore, an accurate data interpretation is required to extract the proper information associated with mineralization (Clark, 2014). For efficient interpretation of geophysical data in mineral exploration, it is initially important to understand the geological properties of a deposit (i.e., host rock, hydrothermal alteration system, mineralogical characteristics, texture, structural controls, zones of outcropping mineralization, etc.). Then, according to these properties and other genetic information, a conceptual model is defined to choose the proper exploration criteria and geophysical exploration methods to identify real anomalies associated with mineralization. Finally, the geophysical data are interpreted by considering the physical properties of the conceptual model. The conceptual model and the interpretation of geophysical data could be updated by using the new information acquired from the exploratory boreholes.
This paper discusses the effectiveness of several geophysical methods in exploration of gold-rich porphyry copper deposits, and presents the exploration models related to the geophysical features of such deposits. We mostly used the related papers published in the same field to prepare these models. Then, on the basis of the defined geophysical signatures of the porphyry deposits, the IP&RS and magnetic data of the Dalli Cu-Au porphyry deposit were interpreted.
Materials and methods
Porphyry deposits are the most important source of copper, molybdenum and rhenium (Sillitoe, 2010) and provide significant amount of gold, silver and some other metals (Cooke et al., 2014). These are intrusion- related deposits which are geometrically symmetrical and are affected by different hydrothermal potassic, phyllic, argillic and propylitic alterations that often show a spatial zonation. Copper-gold mineralization mostly occur in the potassic alteration zone within the contact of the intrusive body and its adjacent wall rock.
The physical properties of minerals and hydrothermal alterations associated with porphyry deposits near the surface are very variable, and therefore allow the use of various geophysical methods for exploration of such deposits. In porphyry deposits, sulfide minerals are present in different alteration zones with varying abundance, which could provide the use of electrical resistivity (RS) and induction polarization (IP) surveys to detect them. In gold-rich porphyry copper deposits, phyllic alteration zone often contain sulfide mineralization, therefore, this zone could be identified by high chargeability anomalies and low resistivities in the induced polarization surveys. The potassic alteration zone also contains sulfide minerals and is characterized in IP data with moderate to high-chargeability values. The IP method is the most extensively used geophysical approach in exploration of porphyry deposits.
Magnetic minerals are enriched and destroyed respectively in potassic and phyllic alteration zones. Therefore, a high circular or elliptical magnetic anomaly is detected at the potassic alteration zone and is surrounded by a low magnetic anomaly related to the phyllic alteration zone. Hence, the airborne and ground magnetic surveys are useful for targeting the copper-gold porphyry deposits. The potassic alteration zone consists of the radiometric K element facilitating the application of the radiometric survey for targeting this zone. Nevertheless, the investigation depth of the radiometric approach is less than a few centimeters, and therefore, it is suitable only for mapping the deeply eroded deposits in which the mineralization occurred in the potassic alteration zone.
Result
The ground magnetic and IP-RS geophysical data of the Dalli Cu-Au porphyry deposit were interpreted based on the proposed conceptual model of the geophysical signature of Cu-Au porphyry systems. Integrating and evaluating the geophysical processes with the result of preliminary drillings indicated that in the Dalli Cu-Au porphyry deposit, the zones with positive and strong magnetic anomalies, high to moderate chargeability and high conductivity, are associated with copper and gold mineralization. Therefore, these criteria should be considered in designing the additional/infill boreholes in further exploration plans for this deposit.
Discussion
The magnetic, IP and RS surveys are the most important and common geophysical methods for targeting the porphyry copper and gold deposits. In particular, implementation and integration of these three methods can be more effective. Other geophysical approaches such as gravity, electromagnetic and seismic methods are also applicable for this purpose, but they are more expensive and complicated than the afore-mentioned approaches.
For proper analysis of the geophysical data, first, it is necessary to recognize the geological model, hydrothermal alteration and mineralization systems of the studied deposits and the geophysical signatures of each alteration zone. Then, an appropriate interpretation of geophysical data is provided through combining the geological information of the deposit with the geophysical data.
References
Clark, D.A., 2014. Magnetic effects of hydrothermal alteration in porphyry copper and iron-oxide copper–gold systems: A review. Tectonophysics, 624–625 (1): 46–65.
Cooke D.R., Hollings P., Wilkinson J.J. and Tosdal, R.M., 2014. Geochemistry of Porphyry Deposits. In: H.D. Holland and K.K. Turekian (Editors), Treatise on Geochemistry. Elsevier, USA, pp. 357–381.
Dentith, M. and Mudge, S., 2014. Geophysics for the Mineral Exploration Geoscientist. Cambridge University Press, New York, 454 pp.
Holden, E.J, Fu, S.C., Kovesi, P., Dentith, M., Bourne, B. and Hope, M., 2011. Automatic identification of responses from porphyry intrusive systems within magnetic data using image analysis. Journal of Applied Geophysics, 74(4): 255–262.
Hoschke, T.G., 2011. Geophysical Signatures of Copper-gold Porphyry and Epithermal Gold Deposits, and Implications for Exploration. ARC Centre of Excellence in Ore Deposits, University of Tasmania, Tasmania, 47 pp.
Sillitoe, R.H., 2010. Porphyry-copper systems. Economic Geology, 105(1): 3–41.ژئوفیزیک اکتشافی روشی ارزان، سریع و کارآمد برای شناخت عوارض زیر سطحی است. اما ژئوفیزیک روشی غیرمستقیم است و بهرهبرداری از اطلاعات ژئوفیزیکی مستلزم تفسیر دقیق و هدفمند دادههای برداشتشده است. برای تفسیر کارآمد دادههای ژئوفیزیکی در اکتشاف کانسارها، ابتدا باید شناخت کاملی از مدل کانسار و ویژگیهای زمینشناسی از قبیل سنگهای میزبان، آلتراسیونها، کانیشناسی و جایگاه کانیسازی در آن نوع کانسار داشت. قبل از حفر گمانههای اکتشافی، با استفاده از مطالعات ژنتیکی و دادههای اکتشافی اولیه و همچنین شواهد سطحی باید یک مدل مفهومی برای کانسار مورد بررسی ارائهکرد و با توجه به ویژگیهای آن مدل مفهومی، روشهای ژئوفیزیکی مناسب، انجام و دادههای اکتسابی تعبیر و تفسیر میشوند. در این پژوهش با توجه به مدل مفهومی و کنترل کنندههای کانیسازی عمومی کانسارهای مس- طلای پورفیری نظیر اهمیت زون پتاسیک با توجه به حضور کانیهای همیافت مگنتیت، کالکوپیریت، بورنیت و پیریت در استوکهای دیوریتی، دادههای ژئوفیزیکی مغناطیسسنجی، مقاومت ویژه الکتریکی و پلاریزاسیون القایی کانسار مس- طلای پورفیری دالی در ایران مورد بررسی قرارگرفت. بهدلیل غنیشدگی کانی مگنتیت در زون دگرسانی پتاسیک و تهیشدگی آن در زون دگرسانی فیلیک، روش مغناطیسسنجی روشی کارآمد برای زونبندی دگرسانیهای مختلف در کانسارهای مس- طلای پورفیری است. همچنین با توجه به وجود کانیهای سولفیدی بهصورت افشان، روش پلاریزاسیون القایی، روشی مناسب برای تعیین گستره کانیهای سولفیدی است. روش مقاومت ویژه الکتریکی نیز برای ردیابی لیتولوژی، دگرسانی و کانیهای فلزی مفید است. این پژوهش نشانداد که در کانسار مس– طلای پورفیری دالی، زونهای با آنومالی مثبت و قوی مغناطیسی معیار بسیار مناسبی برای ردیابی کانسار است. شارژپذیری بهشدت متأثر از درصد پیریت است و زونهای با رسانایی و شارژپذیری خیلی زیاد و آنومالیهای منفی مغناطیسی، منطبق بر هالههای زونهای دگرسانی فیلیک و آرژیلیک است و دارای کانیسازی ناچیز است. آنومالی مغناطیسی، رسانایی بالا (رسانایی کم نیز زونهای سیلیسی را نشان میدهد که حاوی کانیسازی هستند) و شارژپذیری متوسط تا بالا منطبق بر زون دگرسانی پتاسیک که حاوی کانیسازی سولفیدی مس و طلاست، دارند. این ویژگیهای ژئوفیزیکی مهمترین ردیاب کانیسازی در این کانسار است.دانشگاه فردوسی مشهدزمین شناسی اقتصادی2008-730610220190220New hypothesis on time and thermal gradient of subducted slab with emphasis on dolomitic and shale host rocks in formation of Pb-Zn deposits of Irankuh-Ahangaran beltنظریه جدید در خصوص زمان و گرادیان حرارتی پوسته اقیانوسی فرورانده شده با تأکید بر سنگ میزبان دولومیت و شیل در تشکیل کانسارهای سرب و روی کمربند ایرانکوه- آهنگران6777063359110.22067/econg.v10i2.76528FAمحمد حسن کریم پورفردوسی مشهد0000-0002-8708-562Xآزاده ملکزاده شفارودیفردوسی مشهد0000-0002-7373-561Xزهرا اعلمی نیااصفهان0000-0002-0018-2428عباس اسمعیلی سویریفردوسی مشهدچارلز استرنکلرادوJournal Article20181110Introduction
Mississippi Valley-Type (MVT) deposits are epigenetic zinc and lead deposits with minor copper hosted by dolostone, limestone, and locally sandstone in platform carbonate sequences inboard of major orogenic belts (Leach and Sangster, 1993; Leach et al., 2010).
The Irankuh-Ahangaran Belt, which is the most important Pb-Zn mineralized zone of Iran, is situated within the Sanandaj-Sirjan tectonic zone. This belt is 400 km in length and 100 km in width. Three deposits including Irankuh mininig district, Ahangaran and Hosseinabad deposits were studied in this article (Fig. 1).
The aim of this research is study of thermal gradient of subducted slab and age of formation of Pb-Zn deposits at Irankuh-Ahangaran belt, which is contrary information has been published so far on the type and their formation. Also, chemistry of ore-fluid in MVT deposits and impact of dolomitic and shale host rock on paragenesis, alteration, style, reserves and grade of deposits were discussed.These parameters will certainly be useful for exploration of the hidden MVT type deposits in the Irankou-Ahangan belt.
Result and Discussion
The Irankuh mineralization is hosted by Cretaceous dolostone and minor Jurassic shale rocks as epigenetic. The constructive thrust fault, which has been cut the Jurassic and Cretaceous host rocks, has played a major role in the rising of fluid and formation of mineralization. Mineralization is occurred as replacement and open space filling (fault breccia, veinlets and cavity of rock) in dolostone and breccia, veinlet and open space filling in shale host rock. The mineral assembelages are Fe-rich sphalerite, Fe- and Mn-rich dolomite, ankrite, galena, minor pyrite, bituminous, calcite ± quartz ± barite within carbonate host rocks, whereas quartz, pyrite, Fe-rich sphalerite, galena, minor chalcopyrite, low Fe-dolomite, bituminous, ± barite ± calcite are important primary minerals at clastic hos rocks (Karimpour et al., 2018).
The Ahangaran deposit is very similar to Irankuh in host rock, alteration, paragenesis, and form of mineralization. Thrust fault has a constructive role for occurrence of mineralization and later destructive strike slip and normal faults have caused the displacement and destruction of mineralization.
The Hosseinabad deposit is hosted by Jurassic shale, siltstone, and sandstone rocks as vein-veinlets, breccia and open space filling with structural control. Alteratin consists of silicification, chlorite, bituminous, and minor siderite, dolomite and ankerite similar to mineralization hosted by shale in Irankuh district. The mineral assemblages are galena, Fe-rich sphalerite, pyrite, chalcopyrite and minor phyrotite. Due to the lack of a proper dolostone unit in the Husseinabad deposit, mineralization is concentrated in particular areas with low-grade and low-reserves.
Based on lithology, alteration, mineralization style, structural control by thrust faults, mineral paragenesis, and comparison with differnet types of Pb-Zn deposits, all deposits of Irankuh-Ahangaran belt are MVT-type. Deep-seated thrust faults formed during the early stages of subduction (~ 70 to 75 Ma), and played an important role in the upward migration of hydrothermal fluids from the basement to shallow depths. The geochronology of pyrite in Irankuh district based on Re-Os method indicate age of Irankuh Pb-Zn mineralization is 66.5 ± 1.6 Ma (Liu et al., 2019). Since the thrust faults have been cut the Jurassic to Upper Cretaceous rocks, and according to the absoulte age determined in Irankuh, the mineralization of this belt have been formed in the age range of 66 to 56 million years ago, mainly in the Paleocene (Fig. 15).
Karimpour and Sadeghi (2018) suggested the hydrothermal fluid originated from the dehydration of a hot and young oceanic subducted slab, which liberated Pb, Zn, and other metals, and may have removed metals from rocks and organic material of the continental crust. More than 90% of all the water within the oceanic slab was released in the depth zone of the forearc region (depth of 30 to 50 km) (Karimpour and Sadeghi, 2018). In the depth zone, Mg-rich silicate minerals (such as antigorite, hornblende, chlorite, talc) have broken and the produced fluid is rich in Mg and Fe (Fig. 17).
The ore-fluid of MVT deposits is Si-poor and Fe- and Mg- rich. Such fluid is mineralized on the hosts of the dolstone (Irankuh and Ahangaran) or Shale-Siltstone (Hossein Abad, and part of Irankuh and Ahangaran). There are significant differences in the type of paragenesis, alteration, shape, dimensions, reserves and grade in the deposits of this belt, which is controlled by the host rock type.
Based on all lithological evidence, alteration, shape of mineralization, existence of thrust faults, mineral paragenesis and specific geological and geographic location, it can be used to exploration of the hidden MVT deposits in this belt.
References
Karimpour, M.H., Malekzadeh Shafaroudi, A., Esmaeili Sevieri, A., Shabani, S., Allaz, J.M. and Stern, C.R., 2018b. Geology, mineralization, mineral chemistry, and ore-fluid conditions of Irankuh Pb-Zn mining district, south of Isfahan. Journal of Economic Geology, 9(2): 267–294. (in Persian with English abstract)
Karimpour, M.H. and Sadeghi, M., 2018. Dehydration of hot oceanic slab at depth 30–50 km: KEY to formation of Irankuh-Emarat Pb-Zn MVT belt, Central Iran. Journal of Geochemical Exploration, 194: 88–103.
Leach, D.L. and Sangster, D., 1993. Mississippi Valley-type lead-zinc deposits. Geological Association of Canadian. Specific Paper, 40: 289–314.
Leach, D.L, Taylor, R.D., Fey, D.L., Diehl, S.F. and Saltus, R.W., 2010. A Deposit Model for Mississippi Valley-Type Lead-Zinc Ores, Chapter A of Mineral Deposit Models for Resource Assessment. U.S. Geological Survey, Reston, Virginia, Scientific Investigations Report 2010–5070–A., 64 pp.
Liu, Y., Song, Y., Fard, M., Zhou, L., Hou, Z. and Kendricke, M.A., 2019. Pyrite Re-Os age constraints on the Irankuh Zn-Pb deposit, Iran, and regional implications. Ore Geology Reviews, 104: 148–159.کمربند ایرانکوه- آهنگران یکی از مهمترین زونهای کانیسازی سرب و روی ایران است که با روند شمالغربی- جنوبشرقی در مرکز زون ساختاری سنندج- سیرجان واقعشده است. سه منطقه ایرانکوه، آهنگران و حسینآباد بهعنوان مثال موردی در این مقاله بررسی شدهاند. بر پایه شواهد زمینشناسی، ساختاری، شکل و نوع کانیسازی، شیمی محلول هیدروترمالی، آلتراسیون و پاراژنز مینرالی و مقایسه با انواع ذخایر سرب و روی، کلیه کانسارهای سرب و روی کمربند ایرانکوه- آهنگران از نوع MVT هستند. این کانسارها با گسلهای تراستی مرتبط بوده و در زون ساختاری جلوی کمانی مربوط به پوسته اقیانوسی فرورونده جوان و داغ تشکیل شدهاند. در چنین پوستههایی قبل از رسیدن به اعماق 40 کیلومتری، بیش از 90 درصد آب اقیانوسی آزاد و سیلیکاتهای غنی از منیزیوم شکسته میشوند. فلزات بخشی از پوسته اقیانوسی و بخشی از پوسته قارهای تأمین شده است. از آنجاییکه گسلهای تراستی سنگهای ژوراسیک تا کرتاسه بالایی را قطع کردهاند و با توجه به تعیین سن دقیق انجامشده در ایرانکوه، کانیسازیهای این کمربند در دامنه سنی بین 66 تا 56 میلیون سال پیش اغلب در پالئوسن شکل گرفتهاند.
شیمی محلول کانهدار ذخایر MVT فقیر از Si و غنی از Mg و Fe است. چنین سیالی همراه با فلزات از طریق گسلهای تراست بالا آمده است و در سنگ میزبان دولستون (ایرانکوه و آهنگران) یا شیل- سیلتستون (حسین آباد و بخشی از ایرانکوه و آهنگران) کانیسازی انجامشده است. تفاوتهای فاحشی در نوع پاراژنزها، آلتراسیون، شکل، ابعاد، میزان ذخیره و عیار در کانسارهای این کمربند دیده میشود که توسط نوع سنگ میزبان کنترلشده است.
با استناد به تمام شواهد سنگشناسی، آلتراسیون، شکل و حالت کانیسازی، وجود گسلهای تراست، پاراژنز مینرالی و موقعیت خاص زمینشناسی و جغرافیایی ارائهشده، میتوان برای اکتشاف ذخایر MVT پنهان در این کمربند اقدام کرد.