بررسی زمین شیمی و کانه‌زایی در آمیزه افیولیتی‌ غرب رودان با تاکید بر کانه کرومیت

نوع مقاله : پژوهشی

نویسندگان

1 گروه زمین شناسی معدنی و آب، دانشکده علوم زمین، دانشگاه شهید بهشتی، تهران، ایران

2 گروه زمین شناسی، دانشکده علوم پایه، دانشگاه سیستان و بلوچستان، زاهدان، ایران

چکیده

آمیزه افیولیتی رودان در استان هرمزگان در مرز پهنه‌های ساختاری زاگرس در جنوب و مکران- سنندج - سیرجان در شمال واقع است. سنگ‌های فرامافیک به عنوان یکی از تشکیل دهنده­های اصلی این آمیزه بیشتر شامل دونیت، هارزبورژیت و کمی کرومیتیت هستند که به شدت سرپانتینی شده‌اند. در این پژوهش، از روش­های زمین­شناسی (ساختارهای زمین شناسی و دگرسانی‌های در ارتباط با کانه‌زایی) و زمین شیمی در پـی­جـویی کانه‌ های مربوط به رخنمون‌های افیولیت‌ غرب رودان استفاده شده است. این بررسی‌ها شامل تجزیه­های شیمیایی فلورسانس پرتو ایکس (XRF)، ذوب قلیایی (AF)، طیف‌سنجی پلاسمای جفت‌شده القایی (ICP) و روش ملغمه سربی (FA)، نشان می‌دهند که افیولیت‌های غرب رودان مستعد کانی‌زایی‌ آهن ماگمایی، مس و کرومیت بوده و در مقابل، از نظر غنی شدگی از فلزهای گروه پلاتین و طلا ضعیف هستند. کانه‌زایی کرومیت در بخش‌های فرامافیک و درون سنگ میزبان هارزبورژیت‌های سرپانتینیتی شده و سرپانتینیت‌ها به صورت دانه پراکنـده، عدسی شکل و رگه-رگچه‌ای دیده می‌شوند. بافت‌های اولیه کرومیت در سنگ‌های میزبان پریدوتیتی شامل بافت دانه‌ای، مشبک و افشان و بافت‌های ثانویه سنگ­های کرومیت دار در انواع برشی، میلونیتی و تنش آواری هستند. براساس نتایج طیف­سنجی فلورسانس پرتو ایکس (XRF) در نمونه‌های کرومیتی، مقدار اکسید کروم (Cr₂O₃) بین 37/21 تا 08/55 درصد وزنی (wt.%)، مقدار اکسید آهن (Fe₂O₃) بین 13/7 تا 88/15 درصد وزنی و مقدار اکسید آلومینیوم (Al₂O₃) بین 44/5 تا 87/16 درصد وزنی است. مقادیر بالای اکسید کروم (Cr2O3) در کرومیتیت‌های منطقه مورد بررسی با کرومیتیت‌های پرعیار و نوع آلپی همخوانی دارد. بر پایه بررسی­های صحرایی و آزمایشگاهی، افزایش سرپانتینی‌شدن با افزایش پتانسیل کرومیت همراه است، این افزایش سرپانتینی‌شدن به‌ویژه در هارزبورژیت‌ها مشاهده شد. عیار کرومیت در رخدادهای اقتصادی بین ۲۰ تا ۷۵ درصد متغیر بوده و در صورت وجود ذخیره کافی، معدن‌کاری امکان‌پذیر است.

کلیدواژه‌ها

عنوان مقاله [English]

Geochemical and mineralogy study of the West Rudan ophiolite Melange with emphasis on chromite ore

نویسندگان [English]

  • hajar karimi haghighi 1
  • Bahman rahimzadeh 1
  • Sasan Bagheri 2
1 Department of Geology, Faculty of Scinces, Shahid beheshti university, Tehran
2 2- Department of Geology, Faculty of Basic Sciences, University of Sistan and Baluchistan, Zahedan, Iran
چکیده [English]

The Rudan ophiolite complex in Hormozgan Province is located at the boundary between the Zagros structural zone in the south and the Makran-Sanandaj-Sirjan zone in the north. The ultramafic rocks, as the main constituents of this complex, consist mainly of dunite, harzburgite with minor chromitite, which are heavily serpentinized. In this study, geological methods (structural geology and alteration related to mineralization) and geochemical analyses were employed to explore minerals associated with the ophiolite exposures in western Rudan. Geochemical analyses including X-ray fluorescence (XRF), alkaline fusion (AF), induced coupled plasma spectrometry (ICP), and fire assay (FA) were conducted. Results indicate that the western Rudan ophiolites are prospective for magmatic iron, copper, and chromite mineralization. Conversely, they are poor in platinum group elements and gold enrichment. Chromite mineralization occurs in ultramafic units and within the host harzburgite rocks, appearing as disseminated grains, lens-shaped bodies, and vein-veinlet structures. Primary textures of chromite in peridotitic host rocks include granular, mesh, and disseminated types, while secondary textures of chromite-bearing rocks include shear, mylonitic, and cataclastic textures. Based on XRF analysis of chromitite samples, the Cr₂O₃ content ranges from 21.37 to 55.08 wt.%, Fe₂O₃ ranges from 7.13 to 15.88 wt.%, and Al₂O₃ ranges from 5.44 to 16.87 wt.%. The high Cr₂O₃ content in the chromitites of the studied area is consistent with high-grade alpine-type chromitites. Field and laboratory studies show that increased serpentinization correlates with increased chromite potential, especially in harzburgites. The grade of chromite in economic occurrences varies between 20% and 75%, making mining feasible given sufficient reserve.

کلیدواژه‌ها [English]

  • ophiolite mélange. Zagros welded zone
  • Zagros Outer Belt Ophiolite
  • Mineralization
  • Alpine chromitite

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  • تاریخ دریافت: 01 مرداد 1404
  • تاریخ بازنگری: 18 شهریور 1405
  • تاریخ پذیرش: 06 مهر 1404

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