کانسار حلب، جنوب باختر زنجان: کانه زایی روی-سرب (نقره) سولفید توده ای آتشفشان زاد در ناحیه فلززایی تکاب-تخت‌سلیمان- انگوران

کانسار روی سرب (نقره) حلب در فاصله 125 کیلومتری جنوب باختر زنجان قرار‌گرفته و بخشی از ناحیه کانه دار تکاب تخت سلیمان انگوران است. توالی سنگی در محدوده این کانسار متشکل از تناوب شیست های پلیتی، مافیک و فلسیک همراه با میان‌لایه‌هایی از مرمر و کوارتزیت مربوط به پرکامبرین (معادل سازند کهر) است که در حد رخساره شیست سبز تا آمفیبولیت دگرگون شده اند. کانه زایی در کانسار حلب با درازای 300 متر و پهنای 3 تا 5 متر به صورت چینه سان و هم روند با برگ‌ وارگی درون واحدهای شیست فلسیک (کوارتز شیست) رخ‌داده است. بر اساس بررسی‌های میکروسکوپی، کانه‌های فلزی در کانسار حلب شامل کانی های درون زاد اسفالریت، گالن، پیریت و کالکوپیریت، کانی های مرحله برون زاد (اسمیت زونیت، سروزیت، کالکوسیت، کوولیت و گوتیت) و کانی های باطله شامل کوارتز، کلسیت، کلریت و اپیدوت هستند. مهم ترین بافت های کانسنگ شامل لامینه ای، دانه پراکنده، توده ای، بِرشی، جانشینی و رگهرگچه ای است. دگرسانی ها شامل کلریتی‌شدن و سیلیسی‌شدن است. دگرسانی سریسیتی در خارج از افق کانه دار توسعه‌یافته و دگرسانی های کلریتی و سیلیسی را در‌بر‌گرفته است. مقایسه الگوی عناصر نادر خاکی در کوارتز شیست میزبان و نمونه های کانه دار بیانگر غنی شدگی این عناصر (ree = 1046.8∑) در نمونه های کانه دار است. این امر را می توان به شرایط احیایی محیط تشکیل کانه زایی مرتبط دانست. با توجه به ویژگی های زمین شناسی و کانه زایی، کانسار حلب را می توان معادل دگرگون و دگرشکل شده بخش‌های لایه ای و افشان کانسارهای سولفید توده ای آتشفشان زاد نوع بتورست در‌نظر‌گرفت.

The Halab deposit, SW Zanjan: Volcanogenic massive sulfide Zn–Pb (Ag) mineralization, Takab–Takht-e-Soleyman–Angouran metallogenic district

IntroductionThe Halab Zn–Pb (Ag) deposit, 125km southwest of Zanjan, is located in the Takab–TakhteSoleyman–Angouran metallogenic district (TTAMD), SanandajSirjan zone. Several types of deposits are present in the TTAMD, including nonsulfide Zn–Pb deposits, sedimenthosted epithermal gold deposits, epithermal precious and base metal deposits, skarn and volcanosedimentary iron deposits, and massive sulfide PbZn (Ag) deposits. The most important deposits discovered to date within the TTAMD are the Angouran nonsulfide Zn–Pb deposit (Gilg et al., 2006; Boni et al., 2007; Daliran et al., 2013), Zarshuran sedimenthosted epithermal gold deposit (Mehrabi et al., 1999; Asadi et al., 2000; Daliran et al., 2002), and Agdar’reh epithermal gold deposit (Daliran, 2008). Other important deposits or occurrences include Touzlar, Ay Qalasi, Arabshah, Qozlou, Shahrak, Goorgoor, Mianaj, and Halab (Heidari et al., 2015; Mohammadi Niaei et al., 2015; Najafzadeh et al., 2017; Nafisi et al., 2019).To date, no detailed study has been reported to understand the characteristics of Zn–Pb (Ag) mineralization at the Halab deposit. This paper presents the geologic framework, mineralization characteristics, and lithogeochemical signatures of the Halab deposit with emphasis on ore genesis. Identification of these characteristics can serve as a model for exploration of Zn–Pb (Ag) mineralization in the Halab area and other parts of the TTAMD. Materials and methodsDetailed field work was carried out in the Halab deposit. Sixteen polishedthin and thin sections from host rocks and ore horizon were studied by conventional petrographic and mineralogic methods at the University of Zanjan. In addition, a total of 10 samples from barren host rocks and ore horizon at the Halab deposit were analyzed by ICP–MS for trace elements and REE compositions at Zarazma Co., Tehran, Iran. Results and DiscussionThe host rocks in the Halab area consist of Precambrian deformed metamorphic rocks (equal to the Kahar Formation) that are unconformably overlain by dolomitic marble of the Jangoutaran unit. The metamorphic sequence is composed of pelitic (garnet mica schist, biotite muscovite schist, calcite biotite schist), mafic (biotite amphibole schist and actinolite schist), and felsic (quartz schist) schists intercalated with marble, and quartzite. These rocks are metamorphosed in green schist to amphibolite facies.Mineralization in the Halab deposit occurs as NEtrending foliationparallel Zn‒Pb (Ag) stratiform horizon hosted by quartz schist units. The ore horizon reaches up to 300 m in length and 3 to 5 m in width, and it is generally 75° SE dipping. Chloritization and silicification of the host rocks are close to the ore horizon, while the sericitic alteration is envelope of the chloritization and silicification. Sphalerite, galena, pyrite and chalcopyrite are the main sulfide minerals in the Halab deposit based on mineralography. Smithsonite, cerussite, chalcocite, covellite and goethite have formed as supergene minerals. Quartz, calcite, chlorite and epidote also present as gangue minerals. The ore minerals show laminated, disseminated, massive, brecciated, replacement and veinveinlet textures. Chondritenonmineralized REE pattern of barren quartz schist host rocks and mineralized samples indicate that mineralized samples are enriched in REE.The main characteristics of the Halab deposit reveal that Zn‒Pb (Ag) mineralization at Halab is comparable with laminated and disseminated parts of Bathurst types of massive sulfide deposits. AcknowledgementsThe authors are grateful to the University of Zanjan Grant Commission for research funding. Journal of Economic Geology reviewers and editor are also thanked for their constructive suggestions and improved the early version of manuscript. ReferencesAsadi, H.H., Voncken, J.H.L., Kühnel, R.A. and Hale, M., 2000. Petrography, mineralogy and geochemistry of the Zarshuran Carlinlike gold deposit, northwest Iran. Mineralium Deposita, 5(7): 656–671.  https://doi.org/10.1007/s001260050269Boni, M., Gilg, H.A., Balassone, G., Schneider, J., Allen, C.R. and Moore, F., 2007. Hypogene Zn carbonate ores in the Angouran deposit, NW Iran. 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