فهرست مطالب

  • سال دوازدهم شماره 1 (پیاپی 24، بهار 1399)
  • تاریخ انتشار: 1399/02/29
  • تعداد عناوین: 6
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  • مهدی غارسی*، محمد یزدی، ایرج رساء صفحات 1-21

    کانسار مس-‌آهن-‌طلای مزرعه از کانسارهای مهم اسکارن واقع در کمربند فلززایی اهر-‌ارسباران است که بر اثر تزریق توده گرانیتوییدی الیگو-‌میوسن شیورداغ به داخل مجموعه آواری، کربناته قدیمی‌تر و به شکل اسکارن گارنت‌-‌اپیدوت‌دار ایجاد‌شده است. قسمت عمده کانه‌زایی شامل مگنتیت، کالکوپیریت و بورنیت و سولفوسالت‌های بیسموت و نقره، در مرحله اسکارن پس‌رونده تشکیل‌شده است. الگوی پراکندگی عناصر فرعی در زون کانه‌زایی، نشان‌دهنده تهی‌شدگی از HFSE و غنی‌شدگی از LILE است و همچنین نمودار پراکندگی عناصر نادر خاکی که با شیبی ملایم از مقادیرLREE  به سمتHREE  کاهش می‌یابد، نشان‌دهنده تاثیر سیالات با منشا آب‌های جوی بر فرایند کانه‌زایی است. مقادیر ΣREE و La/Y با دور‌شدن از توده نفوذی کاهش‌یافته است و مقادیر *Eu/Eu به عدد یک نزدیک می‌شوند که این امر نشان‌دهنده وجود شرایط اسیدی-‌احیایی در مناطق نزدیک‌تر به توده نفوذی و بازی‌-‌اکسیدان در مناطق دورتر از توده نفوذی در زون اگزو اسکارن است. بر این اساس هم سیالات با منشا ماگمایی و هم آب‌های جوی در تکوین نهایی سیال کانه‌زا در اسکارن مزرعه تاثیر داشته‌اند. آب‌های با منشا ماگمایی در مناطق نزدیک‌تر به توده نفوذی تاثیر‌گذار بوده‌اند؛ اما در مناطق دورتر از توده نفوذی زون اگزو اسکارن تاثیر آب‌های جوی بر سیال کانه‌زا طی مرحله دگرسانی پس‌‌رونده بارزتر بوده است. مقادیر اندازه‌گیری شده ایزوتوپ گوگرد در نمونه‌های پیریت و کالکوپیریت بیانگر منشا ماگمایی گوگرد در کانی های سولفیدی است. دما‌سنجی ایزوتوپی دمای کانه‌زایی در مرحله دگرسانی پس‌رونده را 369 درجه نشان می دهد.

    کلیدواژگان: سیال کانه زا، عناصر نادر خاکی، ایزوتوپ گوگرد، اسکارن مزرعه، منطقه فلززایی اهر - ارسباران
  • معصومه زارع شولی، زهرا طهماسبی*، عادل ساکی، احمد احمدی خلجی صفحات 23-45

    در مجاورت توده پلوتونیکی الوند، انواع سنگ های دگرگونی ناحیه ای و مجاورتی درجه پایین تا بالا وجود دارد. نفوذ توده مافیک باتولیت الوند در سنگ‌ های رسی دگرگون‌شده (شیست ها) سبب ایجاد هورنفلس های رسی و میگماتیت های آناتکسی در هاله دگرگونی خود شده است. پدیده ذوب‌بخشی در هاله همبری الوند فقط در سنگ های با ترکیب رسی رخ‌داده است. مشاهده های صحرایی، بررسی های میکروسکوپی و داده های ژیوشیمیایی نشان می دهد که در منطقه مورد بررسی میگماتیت ها از ذوب‌بخشی هورنفلس ها حاصل شده‌اند. اختلاف قابل‌توجه در مقادیر عناصر نادر خاکی و الگوی REE گرانیت های لوکوکرات و لوکوسوم های میگماتیت نشان می‌دهد که ارتباط ژنتیکی بین میگماتیت ها و گرانیت های هم‌جوار وجود ندارد و نفوذ گرانیت های لوکوکرات بعد از حادثه میگماتیتی‌شدن رخ‌داده است. این نشان‌دهنده آن است که آناتکسی و ذوب‌بخشی به‌دلیل حرارت ناشی از توده های گرانیتی نیست؛ بلکه گرمای حاصل از توده های مافیک قدیمی تر (گابرودیویت ها) عامل اصلی پدیده ذوب‌بخشی و میگماتیتی‌شدن در منطقه است. این یافته ها با داده های سن‌سنجی توده پلوتونیکی الوند و سنگ های میگماتیتی پیرامون آنها همخوانی دارد.

    کلیدواژگان: سنگ های میگماتیتی، ذوب بخشی، گرانیت لوکوکرات، تویسرکان، همدان، زون سنندج- سیرجان
  • ندا شفائی پور، میر علی اصغر مختاری*، حسین کوهستانی، مریم هنرمند صفحات 47-76

    کانسار آهن قوزلو در فاصله 65 کیلومتری باختر زنجان واقع‌شده و بخشی از کمان ماگمایی ارومیه-دختر در پهنه ایران مرکزی است. در این منطقه، تناوب لایه های سنگ‌آهک میکرواسپارایتی، آهک مارنی، شیل و ماسه سنگ مربوط به کرتاسه بالایی توسط توده گرانیتوییدی ایوسن بالایی مورد هجوم قرار‌گرفته و هاله دگرگونی مجاورتی و کانه زایی آهن تشکیل‌شده است. از نظر سنگ شناسی، توده گرانیتوییدی متشکل از گرانیت-‌گرانودیوریت پورفیری و کوارتزمونزودیوریت بوده و دارای ماهیت کالک آلکالن پتاسیم بالا و متعلق به گرانیتوییدهای متاآلومینوس نوع I است. در نمودارهای تمایز محیط زمین‌ساختی، این توده در محیط حاشیه فعال قاره ای قرار می گیرد. بر اساس بررسی‌های میکروسکوپی، هاله دگرگونی مجاورتی متشکل از زیرپهنه های گارنت اسکارن، گارنت-پیروکسن اسکارن، پیروکسن اسکارن، اپیدوت اسکارن، مرمر پیروکسن دار و اسکارن کانه دار است. مگنتیت کانی اصلی کانسار است که با کانی های فرعی پیریت، کالکوپیریت و پیروتیت همراهی می شود. گارنت، کلینوپیروکسن، اپیدوت،  اکتینولیت، کلسیت و کوارتز به‌عنوان کانی های غیر‌ فلزی حضور دارند. شواهد بافتی در سنگ های هاله دگرگونی مجاورتی نشان‌دهنده تشکیل هم زمان گارنت و کلینوپیروکسن در محدوده دمایی 430 تا 550 درجه سانتی گراد و 26-10- 23-10 ƒO2 =است.

    کلیدواژگان: زمین شیمی، گرانیتوئید، اسکارن آهن، قوزلو، زنجان
  • اسماعیل خان چوبان*، بهزاد حاج علیلو، محسن موید، محمدرضا حسین زاده صفحات 77-91

    نهشته منگنز قزل داش داغی در 25 کیلومتری شمال غرب شهر مرند در استان آذربایجان شرقی قرار دارد. از نظر ساختاری، این نهشته در پهنه مرکزی واقع‌شده است. میزبان کانی زایی در افق I توفیت و سنگ‌ آهک آب شیرین و در افق II کنلگومرا و ماسه سنگ حوضه آتشفشانی کواترنری است. شکل کانی زایی در افق I، لایه ای-لامینه ای و در افق II، عدسی-‌پرشدگی شکستگی هاست. ویژگی‌های زمین شیمیایی نهشته توسط مقدار عناصر اکسیدهای اصلی، جزیی مطالعه و منشا کانی زایی بحث‌ شده است. غلظت های به نسبت بالای Al (01/0 تا  39/7 درصد وزنی، متوسط = 34/1) احتمالا به‌خاطر لیتیک توف های میزبان است. مقادیر کم تیتانیوم (0 تا 28/0 درصد وزنی، متوسط = 05/0) نشانه ورود اندک مواد آواری طی کانی زایی است. داده هایی مثل Mn:Fe (متوسط 29/21)، Ba بالا (متوسط 4/1782)،Co:Ni  (متوسط 79/0)، Co:Zn (متوسط 18/1) و نمودارهای تمایز نهشته های منگنز نشان می دهد که نهشته قزل داش داغی کانی زایی آتشفشانی - رسوبی از نوع گرمابی است.

    کلیدواژگان: منگنز، زمین شیمی، گرمابی، قزل داش داغی، مرند، آذربایجان شرقی، پهنه مرکزی
  • سعیده جدیدی اردکانی، محمد علی مکی زاده*، فریماه آیتی صفحات 93-109

    در کانسار مس پورفیری علی آباد واقع در شمال‌ غرب باتولیت گرانیتی شیرکوه یزد، ماسه سنگ های آرکوزی و کنگلومراهای کرتاسه زیرین، تحت‌تاثیر نفوذ توده لوکوگرانیتی (بعد از کرتاسه)، متحمل دگرسانی های گرمابی اغلب فیلیک و کانی سازی مس پورفیری در توده نفوذی همراه شده‌ اند. تنها در یک نقطه کانی سازی اسکارن بدون مس نیز شکل‌گرفته است. کانی های پهنه دگرسانی فیلیک با همایندی زیر مشخص هستند: Sericite + quartz + pyrite + alunite + turquoise + goethite + jarucite فیروزه به شکل‌های رگچه ای، گرهک های کم‌و‌بیش مدور تا بی شکل و پوششی در رنگ های آبی، آبی-‌سبز و آبی متمایل به سفید در آرکوزهای دگرسان مشاهده می شود. هم‌پوشانی هوازدگی جوی بر پهنه فیلیک، سبب اکسیداسیون پیریت و کالکوپیریت و شکل گیری سیال اسیدی شده که فروشست Al ،Cu و P را از سنگ میزبان شکل‌داده است. عملکرد این سیال بر سنگ میزبان ضمن مراحل چندگانه سبب رخداد فیروزه شده است. خاستگاه و رخداد فیروزه ناشی از دگرسانی کانی های سنگ میزبان فیلیک-آرژیلیک (کایولینیت) است. همچنین همیافتی نزدیک آلونیت با فیروزه در برخی موارد، خاستگاه آن را به خرج آلونیت (فسفاتی شدن) نیز ممکن می سازد.

    کلیدواژگان: فیروزه، آلونیت، مس پورفیری، علی آباد، ایران مرکزی
  • سید علی مظهری*، علیرضا مظلومی بجستانی صفحات 111-127

    ترکیب خاک‌های شهری مشهد نشان می دهد که میزان عناصر سنگین در آنها به نسبت خاک‌های غیرآلوده دور از مناطق شهری به‌شدت افزایش‌یافته است. مقادیر عناصر Cd، Cu، Pb، Sn و Zn در نمونه خاک پارک‌ها چندین برابر بیشتر از خاک‌های غیرشهری است. تجزیه و تحلیل آماری داده های ژیوشیمیایی نشان‌دهنده تاثیر فعالیت‌های انسان زاد بر روی تمرکز فلزات سنگین Pb، Cd، Sn و Zn است؛ درحالی‌که، علاوه‌بر فعالیت‌های انسانی، منابع طبیعی (خاک‌های مشتق‌شده از سنگ‌های اولترامافیک) نیز در توزیع عناصر Co، Cr و Co نقش داشته اند. ترکیب و نسبت ایزوتوپ‌های Pb در خاک‌های شهری مشهد نشان‌دهنده ماهیت نسبتا غیر رادیوژنیک این خاک‌ها با نسبت‌های پایین 206Pb/204Pb (024/18- 284/17)، 207Pb/204Pb (525/15- 482/15)، 208Pb/204Pb (964/37- 405/37) و 206Pb/207Pb (116/1 و 161/1) است. ترکیب ایزوتوپ‌های سرب نشان می دهد که میانگین مشارکت منابع طبیعی و انسان زاد (مجموع منابع صنعتی و بنزین سرب دار) در پارک‌های مشهد به‌ترتیب % 6/6 و % 4/93 است که بیانگر آلودگی قابل‌ملاحظه خاک در پارک‌های این شهر است. منبع اصلی آلودگی در نمونه های خاک با میزان سرب نسبتا پایین (کمتر از mg kg-1 90)، فعالیت‌های صنعتی است؛ درحالی‌که با افزایش میزان سرب در خاک‌ها سهم بنزین سرب دار افزایش می یابد. نقشه توزیع فلزات سنگین در خاک‌های سطحی پارک‌های مشهد نیز این امر را تایید می کند. در پارک‌های مناطق مرکزی مشهد که دارای تمرکز بالاتری از فلزات سنگین به‌خصوص سرب هستند، بنزین سرب دار سهم بالاتری در آلایش خاک‌ها ایفا می کند. ترافیک سنگین در این محدوده به‌عنوان عامل اصلی در تجمع فلزات سنگین و آلودگی خاک‌های سطحی عمل‌کرده است.

    کلیدواژگان: خاک شهری، پارک، فلزات سنگین، نسبت های ایزوتوپی Pb، مشهد
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  • Mehdi Gharesi*, Mohammad Yazdi, Iraj Rasa Pages 1-21
    Introduction

    The Western Alborz - Lesser Caucasus metallogenic belt includes important Cu and Cu-Au skarn, porphyry and epithermal deposits of Tertiary age in Iran, Turkey and Armenia (Karimzadeh Somarin and Moayyed, 2002; Karimzadeh Somarin, 2004). Important deposits such as Sungun and Masjed Daghi have been situated in this zone in Iran (Ghorbani, 2011). Some researchers have called this zone in the north-western part of the Iranian Copper belt Arasbaran Copper belt (Hassanpour et al., 2010). The Mazraeh deposit is located 20 km north of Ahar city between geographical longitudes '47 ° 00 and 47 ° 08', and latitudes 38 ° 40 '. In addition, 38 ° 36' is a part of Arasbaran Copper Belt in the Kaleyber’s 1:100000 geological map. In recent years, it has become possible to study subsurface samples in this deposit to a depth of 300 meters and provide the opportunity for extensive study of mineralogy and geochemistry of this deposit by conducting systematic exploratory drillings by the National Copper Corporation. Considering the relatively high amounts of gold in cores obtained from drill holes, the study of relationship between gold mineralization and other metals in this deposit has become important for assessing the mineral potential of this deposit. Better understanding of the mechanisms of mineralization in this deposit is useful for its comparison with other similar deposits and better exploratory design for exploration of similar undiscovered deposits in this region. Nowadays, the origin of mineralizing fluids can be discussed with higher certainty with advances in experimental methods including isotopic analysis, fluid inclusion and REE studies (Bowman, 1998). We can obtain valuable information about the origin of fluids causing skarn ore deposits by studying the REE ratios in rock samples. The study of stable isotopes also provides valuable information on temperature of mineralization and physicochemical conditions of mineralizing fluids. Contrary to old beliefs that mineralizing fluids originated from magma in all deposits, the study of stable isotopes has shown that water from other sources can also play an important role in the formation of many deposits (Meinert, 1995). Previous studies have proved that both magmatic and meteoric water have been important in the formation and genesis of many skarn deposits (Taylor and Oneil, 1977). In this paper, we tried to use data from sulfur isotopic studies and the geochemistry of trace and rare earth elements to determine the source and type of fluids affecting mineralization in the Mazraeh skarn deposit.

    Materials and methods

    In order to investigate and identify the fluids effective in the process of skarn mineralization, 22 samples (20 samples from the mineralized zone and 2 samples from the intrusive body) were sent to the Binaloud laboratory for ICP-MS analysis. The results were used in geochemical diagrams. For isotopic studies, samples were taken from different parts of the mineralized skarn. 10 samples of sulfides (pyrite and chalcopyrite) were selected to study sulfur stable isotopes. After crushing the samples, the sulfides were separated under a binocular microscope from waste gangue and they were powdered in agate pounder to obtain a concentrate of mineral sulfide. Purity of the sulfides as higher than 95% and weight of the samples was 100 to 150 mg. Isotopic measurements were performed by a mass spectrometer at Ottawa University, Canada. The type of sulfides and their isotope values based on isotopic standard of the CDT are reported in Table 2.

    Results

    The results of geochemical studies of rare earth elements indicate the combined effects of magmatic and meteoric water in mineralized fluids in the Mazraeh deposit. Accordingly, magmatic fluids have influenced the mineralizing fluids in the early stages of mineralization. However, the effect of meteoric water on mineralizing fluid in the process of fluid dilution and precipitation of sulfide minerals during the retrograde alteration stage has been more effective in the main and final stages of mineralization. The results of sulfur isotope analysis indicated that sulfur in mineralized fluids has originated from magmatic sources. Also, isotopic thermometry shows temperature of 369 ° C for sulfide mineralization. This temperature indicates the beginning stage of sulfide mineralization in progressive alteration stage.

    Keywords: Mineralizing fluid, Rare Earth Elements, Sulfur isotope, Mazraeh Skarn, Ahar–Arasbaran metallogenic belt
  • Masoumeh Zare Shooli, Zahra Tahmasbi*, Adel Saki, Ahmad Ahmadi Khalaji Pages 23-45
    Introduction

    Partial melting is an appropriate correlation process between metamorphism and magmatism which plays a key role in the development of migmatites, granulites and S-type granites during crust evolution (Kriegsman, 2001; Alvarez-Valero and Kriegsman, 2008; Sawyer, 2010). In this study, we tried to address the correlation between partial melting process and metapelites migmatization and the formation of adjacent granites through microscopic and field evidence and geochemical data.

    Materials and methods

    Petrography and field studies were carried out and in order to identify minerals’ composition and determine temperature and pressure. A few spots of different minerals were analyzed by microprobe electron method with CAMECA device model SX100 at the Geosciences Research Institute of China University. Also, in order to evaluate the geochemical and the correlation between migmatites, leucocratic granite and metapelites, several samples of the mentioned rocks were selected. Their major and minor elements were respectively analyzed by the XRF and ICP-MS methods at Beijing University of China.

    Results

    While the pattern of rare earth elements (REE) in migmatite leucosome and adjacent granites shows that leucosome and leucocratic granite do not have the same origin, the leucocratic granite influence has occurred after the migmatization event, geothermobarometric calculations of migmatites and intrusive bodies as well as age measurement of Alvand Plutonic mass and migmatite rocks confirm that anatexis and partial melting do not come from granitic body heat but also heat of older mafic bodies is the cause of partial melting and migmatization in the region. Therefore, migmatites have emerged because of contact metamorphism which itself is the result of injection of the same age mafic bodies with migmatites.

    Discussion

    Migmatites of the study area are composed of quartz, plagioclase, potassium feldspar, biotite, andalusite, cordierite, spinel, and sillimanite minerals. Temperature and pressure for metamorphism peak are approximately 700 ° C and 4 kbar, respectively. Based on these data, the formation depth of these rocks is about 11 km. Therefore, their geothermal gradient is 54 °C/km which is located in the contact metamorphism zone and the Buchan type metamorphism series and it is in accordance with high temperature-low pressure metamorphisms. Migmatites are located near the leucocratic granite in some parts of Tuyserkan. However, they do not have any contact with granites in other parts but they have outcrops with hornfels rocks instead. The pattern of rare earth elements (REE) has been used to find out the migmatites protolith in the Hamadan area. Since, the pattern of rare earth elements (REE) of migmatites and metapelites has a similar process, this lithology has been used as a probable protolith. In order to identify the distributed elements inside the molten or in the residual (restite), the average chemical composition of probable protolith (cordierite hornfels) was used as a normalization standard for restite geochemistry in multi-element diagrams. According to spider diagrams pattern (mesosome, leucosome) normalized to the average metapelites based on mass balance, it can be concluded that migmatites have been formed by evolution of cordierite hornfels. In order to investigate the origin and possible relations between leucosome and adjacent granites (leucocratic granite), the chemical composition of these rocks was compared. Leucocratic granite located in the migmatites immediate contact and leucosome which is a few centimeters thick are considered in this comparison. The pattern of rare earth elements (REE) shows a significant difference in the migmatite leucosome and adjacent granites. The most important results of REE patterns is the difference in HFSE value in granites and leucosome. Thermometry has been conducted on intrusive masses (gabbro) through various methods and by Sepahi et al. (2012). The approximate temperatures of 950 ° C for gabbro and 1300 ° C for olivine gabbro are estimated. Also, due to contact metamorphism reactions, the maximum contact temperature of porphyry granites (Alvand intrusive mass) is estimated to be about 530 to 550 ° C (Sepahi and Moein Vaziri, 2001). Such a temperature is not sufficient for migmatization in the region. Shahbazi et al. (2010) have acquired the age of Alvand plutonic rocks to be 166.5 ± 1.8 Ma for gabbro, 163.0 ± 9.9 and 161.7 ± 0.6 Ma for granites and 154.4 ± 1.3 and 153.3 ± 2.7 Ma for leucocratic granite. Jafari (2018) has acquired the age of Hamadan's Migmatites to be about 160 to 180 Ma and an average of 170 million years which is almost equal to the age of Alvand Plutonic body.

    Keywords: migmatites, partial melting, leucocratic granite, Tuyserkan, Hamadan, Sanandaj-Srjan zone
  • Neda Shafaiepour, Mir Ali Asghar Mokhtari*, Hossein Kouhestani, Maryam Honarmand Pages 47-76
    Introduction

    Fe skarn deposits are one of the important Fe deposits in the Zanjan province which have been exploited in recent years. The Qozlou Fe deposit is one of these Fe skarn deposits which is located at 65 km west of Zanjan. In this area, alternation of micro-sparitic limestone, marly limestone, shale and sandstones of Upper Cretaceous were intruded by Late Eocene granitoids. This event caused to metamorphism contact and it caused the formation of Fe mineralization. Some of the Fe skarn deposits in the Zanjan province were studied during the past few years (e.g. Nabatian et al., 2017) and valuable information is present about their geological and mineralization characteristics. However, Qozlou granitoid and Fe deposit have not been studied yet. In this research, petrology and geochemistry of the Qozlou granitoid along with petrographic characteristics, mineralogy, structure and texture of Fe deposit and thermodynamic conditions for formation of contact metamorphic rocks have been studied.

    Materials and methods

    This research study can be divided into two parts including field and laboratory studies. Field studies include The recognition of different parts of granitoid intrusion and skarn aureole along with sampling for laboratory studies. Thus, 50 samples were selected for petrographic and analytical studies. 16 thin sections and 16 thin-polish sections were used for petrographical and mineralogical studies. 13 samples from granitoid and ore skarn sub-zone were analyzed by XRF and ICP-MS methods at the Zarazma laboratory, Tehran for geochemical studies.

    Results

    Based on petrographic studies, the Qozlou granitoid is composed of porphyritic granite-granodiorite and quartz monzodiorite. Porphyritic granite-granodiorite have porphyritic to porphyroidic, micro-graphic and felsophyric textures and are composed of plagioclase, quartz, K-feldspar, hornblende and biotite phenocrysts within quartz-feldspatic groundmass. Quartz monzodiorites indicate porphyroidic texture and they are composed of plagioclase, hornblende, quartz and K-feldspar. The Qozlou granitoid demonstartes high-K calc-alkaline affinity and it is classified as metaluminous I-type granitoids. Trace elements normalized by primitive mantle (Sun and McDonough, 1989) for Qozlou granitoid indicate LILE and LREE enrichment along with negative HFSE anomalies and distinctive positive Pb anomaly. Chondrite-normalized (Nakamura, 1974) REE patterns for the Qozlou granitoid demonstrate LREE enrichment (high LREE/HREE ratio). Based on tectonic setting discrimination diagrams, the Qozlou granitoid were formed in active continental margin. Microscopic studies reveal that the skarn zone in Qozlou is composed of garnet skarn, garnet-pyroxene skarn, pyroxene skarn, epidote skarn, and pyroxene-bearing marble sub-zones. The Ore zone is present as massive and lens-shaped with 300m length and up to 30m width. Magnetite is the main ore mineral along with some pyrite, chalcopyrite and pyrrhotite. Garnet, clinopyroxene, epidote, actinolite, calcite and quartz present in skarn zone. Based on field and microscopic studies, the Qozlou Fe deposit indicates massive, banded, disseminated, brecciated, vein-veinlets, replacement and relict textures. Based on mineralogical and textural studies, skarnization processes in the Qozlou deposit can be divided into 3 stages including: (1) isocheimal metamorphic stage, (2) prograde metasomatic stage and (3) retrograde metasomatic stage. Chondrite-normalized (Sun and McDonough, 1989) REE and trace element patterns for different skarn samples and porphyritic granite demonstrate similar patterns.

    Discussion

    Since all of minerals present in the Qozlou skarn aureole are located in Ca-Fe-Si-C-O-H system, we used the temperature vs. logƒO2 diagram (Einaudi, 1982) to determine possible physico-chemical conditions for skarn formation in the Qozlou. Based on this diagram and considering mineralogical and textural evidence, garnet and clinopyroxene were formed simultaneously in 430-550°C and ƒO2 equal 10-23 to 10-26. In the temperature less than 430°C and increasing ƒO2, garnet and clinopyroxene replaced by epidote, actinolite, quartz and calcite, respectively. Furthermore, in temperature of less than 430°C, fluids in equilibrium with granitic intrusion and with relatively high sulfidation (ƒS2>10-6), were not in equilibrium with andradite. Therefore, andradite was replaced by quartz, calcite and pyrite. With reducing ƒS2 (<10-6), andradite was replaced by quartz, calcite and magnetite. During the early retrograde stage, magnetite and pyrite were formed along with quartz and calcite. Mineralogical studies indicate that pyrite was formed after magnetite. Based on this, it seems that metasomatic fluids probably had ƒS2≈10-6.5 and had less than 430°C temperature in the beginning of the retrograde stage. Presence of hematite lamellae within the magnetite demonstrates that ƒO2 probably was 10-22 in the beginning of retrograde stage.

    Keywords: Geochemistry, Granitoid, Fe skarn, Qozlou, Zanjan
  • Ismail Khan Chuban*, Behzad Haj Alilou, Mohsen Moayyed, Mohammadreza Hosseinzadeh Pages 77-91
    Introduction

    It is generally understood that manganese deposits have a diverse origin, based on their mineralogy, chemical composition and tectonic setting. Marine Mn-bearing deposits are classified as hydrogenous, hydrothermal and also biogenetic-bacterial deposits (Bonatti et al., 1972; Hein et al., 1997; Bau et al., 2014; Polgári et al., 2012; Schmidt et al., 2014). Hydrogenous processes can form ferromanganese crusts, which result from slow precipitation of seawater at the seafloor often via microbial mediation (Toth, 1980; Dymond et al., 1984; Bau and Dulski, 1999; Usui and Someya, 1997; Hein et al., 2000; Jach and Dudek, 2005). Diagenetic manganese deposits occur as nodules and precipitate from hydrothermal solutions or pore water (Polgári et al., 1991; Oksuz, 2011; Polgári et al., 2012), whereas hydrothermal ore deposits are stratabound or occur as irregular bodies and epithermal veins, where they are formed in a marine environment near spreading centers, intraplate seamounts or in subduction-related island arc setting (Roy, 1992; Roy, 1997; Hein et al., 2008; Edwards et al., 2011).

    Materials and Method 

    Eighteen Ore samples (~ 500 g each) were collected systematically from the Gezeldash Daghi manganese deposit. All these ore samples were taken representatively from the surface outcrops ore beds in different places for geochemical analyses. Ore samples were powdered under 200 meshes and analyzed at Iran mineral processing research center laboratories, Tehran. After being prepared by the Lithium Borate Fusion method, their major oxide and trace element contents were determined with ICP-OES. The results of the analyses are given in Tables 1 and 2.

    Results and Discussion

    The deposit is hosted in various lithology and horizons consisting of: 1) tuffite interlayered with limestone, 2) conglomerate and sandstone lithology into volcano-sedimentary basin located at 25 km northwest of Marand city (N38°35ʹ40ʺ, E45°42ʹ40ʺ). Major and trace element assessments show that hydrothermal solutions were effective in the formation of the Gezeldash Daghi manganese deposit. Also, field observations reveal that manganese mineralization occurred as laminated-layered and fracture-filling form in limestone and tuffite at horizon I and the space-filling form between conglomerate clasts and veinlet form in sandstone at horizon II with quaternary age. Therefore, it can be concluded that hydrothermal solutions were caused in the formation of the manganese deposit which may be described as related to volcano-hydrothermal occurrence.

    Keywords: Manganese, Geochemistry, Hydrothermal, Gezeldash Daghi, Marand, Eastern Azerbaijan, Central domain
  • Saeide Jadidi Ardekani, Mohammad Ali Mackizadeh*, Farimah Ayati Pages 93-109
    Introduction

    In porphyry copper deposits, turquoise is considered to be a supergene oxidation product (John et al., 2010; Chavez, 2000). Based on Rezaian et al., 2003; Zarasvandi et al., 2005 and Eslamizadeh, 2004, the Aliabad index is introduced as a porphyry copper system. The first published report on turquoise events around Ali-Abad was presented by Momenzadeh et al., 1988. This area is located 57 km southwest of Yazd. Alterations often include siricitization, advanced argillization. Kaolinization and silicification have occurred frequently in the arkose and microcan glomerate of the Sangestan formation. The aim of this research study is to try to reconstruct and investigate the formation and origin of turquoise by using the latest mineralogical and geochemical data. Field evidence shows occurrence of turquoise in the form of a veinlet and nodules, with blue-green and blue-white colors. Jarosite, alunite, quartz and iron oxides are found together with turquoise.

    Materials and Methods

    A geological map of the area with a scale of 1/15000 was prepared. 35 samples of intrusive bodies, sandstones and altered rocks were selected to produce thin and polished sections. XRD and the EDS analyses were carried out at the central laboratory of Isfahan University and the University of Oklahoma, USA, respectively in order to identify the chemical composition of phases.

    Results

    Based on the studies, several chain processes have been involved in the form of turquoise: the initiator of the reactions is the formation of an oxidant environment (gossan), in which metal sulfides (Cu, Fe) in the phyllic zone of porphyry copper deposit have played a fundamental role. Turquoise has two species in this area. One is in the form of direct deposition in the veinlets, away from the alteration of the host rock and the mineralization center, and the other one is in the form of substitution. It is undeniable that the host rock with Kaolinite-sericite alteration is required for substitution. The close association of alunite-turquoise may imply that turquoise is a product of the phosphatization process of alunite. The Alunite Supergene event in the alteration zone and its accompaniment with turquoise indicates the mineral complex of advanced argillic alteration. The mineral chemistry highlighted the high percentages of aluminum concentration which is a property of minerals in advanced argillic zone.

    Discussion

    The phyllic zone has the largest part of the region's alteration (Taghipour and Mackizadeh, 2011; Moore et al., 2011). An advanced argillic zone with the presence of alunite-jarosite with turquoise is scattered inside the phyllic zone. To confirm microscopic observations, XRD and EDS analyses were used. These analyses prove the presence of the turquoise phase. In some analyses performed on the turquoise mineral phase, the presence of potassium and silicon probably indicates the transitional phase of conversion of sericite or alunite to turquoise. Pyrite in the oxidant condition has been disrupted by the effects of atmospheric water and created goethite and sulfuric acid. The produced ferric sulfate can induce dissolution of chalcopyrite. The occurrence of iron oxides and oxy-hydroxides will lead to the development of the gossan zone. Gossan's transformation, in addition to supplying copper, causes acidic fluids to continue the reaction. Under acidic conditions, the phosphate leaching from the arkose has been subjected to the following reaction: Ca5 (PO4)3OH + 5H2SO4 + 9/2O2 → 5CaSO4 2H2O + 3H3PO4 In addition to phosphate and copper, aluminum is the most important element in the structure of turquoise. Under an acidic environment, arkose feldspars and hydrolysis reactions during alteration will be used for the formation of sericite, kaolinite and gypsite. With the presence of sulfate and potassium released from the alteration of feldspars, alunite and turquoise can be formed. The alunite-turquoise paragenesis confirms formation of turquoise by alunite (Espahbod, 1976). Turquoise will be formed by the reaction of potassium, copper sulfate and anion phosphate with alunite: 8K+ + CuSO4 + 4H2PO4- + 2KAl3 (SO4)2(OH) 6 → CuAl6 (PO4)4(OH)8 4H2O + 5K2SO4 + 4H+ The hydrogen ions released in this reaction will lower the pH of the environment and cause progression of hydrolysis reactions. Finally, jarosite will be formed by the interaction of K+, sulfate and Fe3+. Based on these reactions, an aluminum-rich phase is needed for stabilizing phosphate and soluble copper.

    Keywords: Turquoise, Alunite, Cu-porphyry, Ali Abad, Central Iran
  • Seyed Ali Mazhari*, Alireza Mazloumi Bajestani Pages 111-127
    Introduction

    Anthropogenic activities have a high impact on urban areas and lead to severe pollution in large cities. Urban soils are huge ‘basins’ for accumulation of various pollutants. Thus, they also serve as informative media. Therefore, the study of urban soils has developed in recent years. Mashhad is the second metropolitan city in Iran which has more than 3 million residences and over 20 million annual pilgrimage tourists. This city is surrounded by numerous factories and the high growth of urbanization has led to accelerated air pollution. In this research study, new analytical data for heavy metals (Cd, Co, Cr, Cu, Ni, Pb, Sn and Zn) in soil of parks in Mashhad are presented and they are compared with unpolluted non-urban soils. Then, the origin of soil pollution in park soils is discussed by statistical methods and Pb isotope values.

    Materials and methods

    The main aim of this work is to focus on the urban areas of Mashhad and study park soil geochemistry. Twenty three parks were selected for this purpose. At each selected park, top soils (5-20 cm) were collected. In addition to park samples, 4 soil samples were collected from areas which were far from the urban areas and they were considered to be unpolluted. The concentration of heavy metals was defined by ICP-MS at the accredited Activation Laboratories (Actlabs.), Canada. To determine available and bioavailable fractions of Co, Cr and Ni, soil samples were analyzed by the DTPA method (Lindsay and Norvell, 1978). Pearson correlation coefficients and PCA are used to investigate elemental associations and extract latent factors for analyzing relationships among the observed variables. In this regard, these statistical analyses of park soils data were done with the SPSS 16.0 software package for Windows. The geochemical maps were plotted by a geographical information system (GIS) using ArcMap v.10.0 (ArcGIS) to show the overall spatial distribution patterns of total and available heavy metal concentrations. The Pb isotopes were measured in all samples by a ThermoFinnigan Neptune MC-ICP-MS instrument. Isotopic measurements were performed by the procedure proposed by Álvarez-Iglesias et al.’s (2012).

    Results and discussion

    Park soil samples have a higher concentration of heavy metals than non-urban soils. PCA analysis and Pearson correlation coefficient indicate that anthropogenic sources are the main factors controlling the Cd, Pb, Sn and Zn concentrations (PC1 component) in park soils. In other words, both anthropogenic and natural sources are responsible for Cr, Co and Ni (PC2 component) distribution in these soils. The spatial variation of heavy metals in the soil of parks in Mashhad confirm the statistical results and PC1 and PC2 heavy metals show different spatial variations. Furthermore, there is clear correlation between metals distributions, so that central parks generally have a higher content of all heavy metals which could be related to the heavy traffic and many traffic jams and air pollution in these areas. The lead isotopic ratios of the sample studied show that park soils show a distinct composition from non-urban soils. These samples are less radiogenic than non-urban soils with lower 206Pb/204Pb, 207Pb/204Pb, 208Pb/204Pb, 206Pb/207Pb and higher 208Pb/206Pb ratios. The wide range of isotope ratios in park soils indicate that the Pb content in these soils is produced by the combination of different sources including natural and anthropogenic origins and that it has also been accumulating over time because of the enormous use of Pb in fuel, industrial activities, etc. (Galušková et al., 2014). The low 206Pb/204Pb values in park soils confirm a possible anthropogenic origin from the use of fossil fuels. The three-end-member model was used to determine possible Pb sources in the soil of parks in Mashhad. The average contribution was 6.6% and 93.4% for natural and anthropogenic (industrial and leaded petrol) sources, respectively. The detailed investigation of Pb isotope and Pb content of soil of parks suggests that industrial source is the main origin of samples with relatively low Pb content (<90 mg kg-1). The contribution of leaded petrol increases in the samples with high Pb. These soils were sampled from the central parks of Mashhad which have high traffic intensity.

    Conclusion

    The concentrations of potentially toxic elements in the soil of parks in the city of Mashhad are highly enriched relative to non-urban soils. The Pb isotope composition of non-urban soils indicate that they have a natural source while park soil samples have originated from anthropogenic sources. The soils which are sampled from the central parks of Mashhad have shown the highest heavy metal pollution due to high traffic congestion in these areas.

    Keywords: Urban soil, park, heavy metals, Pb isotopic ratios, Mashhad