بررسی نقش سولفیداسیون سنگ های کربناته آهن دار در افزایش عیار طلای کانسار زرشوران (شمال تکاب)، ناحیه فلززایی تکاب- انگوران

زمین شناسی اقتصادی

دوره 14، شماره 4 - شماره پیاپی 35، دی 1401، صفحه 89-114   

نوع مقاله: مقاله پژوهشی

شناسه دیجیتال (DOI): 10.22067/econg.2022.75417.1042

نویسندگان

شراره حشمت نیا¹؛ ابراهیم طالع فاضل^{* 2}؛ عباس اروجی³

¹کارشناسی ارشد، گروه زمین‌شناسی، دانشکده علوم پایه، دانشگاه بوعلی سینا، همدان، ایران

²استادیار، گروه زمین‌شناسی، دانشکده علوم پایه، دانشگاه بوعلی سینا، همدان، ایران

³دانشجوی دکتری، گروه زمین‌شناسی، دانشکده علوم پایه، دانشگاه بوعلی سینا، همدان، ایران

چکیده

سولفیدهای آهن و آرسنیک به­ عنوان مهم‌ترین میزبان طلا در ذخایر طلای افشان نامرئی با سنگ میزبان رسوبی محسوب می ­شوند. کانسار طلای زرشوران (ذخیره قطعی 155 تن طلا و عیار متوسط 63/2 گرم در تن)، در میزبان شیل و سیلتستون سیاه (واحد زرشوران) و کربنات ­های آهن ­دار (واحد چالداغ) به سن کامبرین زیرین شکل‌گرفته است. کانه ­های سولفید آرسنیک (نظیر رآلگار و ارپیمنت) و ­پیریت­ های آرسنی ک­دار مهم‌ترین میزبان طلا در این کانسار هستند. بر اساس شواهد تجزیه ریزکاوالکترونی، پیریت با محتوای آرسنیک زیر حد تشخیص تا 99/3 درصد وزنی در شش نوع مختلف به ­ترتیب شامل Py0 (محتوای طلاppm  01/0)، Py1 (محتوای طلاppm  02/0)، Py2 (محتوای طلا ppm 03/0)، Py3 (محتوای طلاppm  02/0)، Py4 (محتوای طلاppm  04/0) و Py5 (محتوای طلاppm  01/0) شناسایی شد. طبق نتایج به ­دست آمده، طلا اغلب به ­صورت مشارکت شیمیایی در شبکه کانی (Au¹⁺ یا Au³⁺) یا ادخال­ های نانوذرات آزاد (Au⁰) حضور دارد. همبستگی زمین‌شیمیایی ضعیف میان عناصر As و S (6/0- R² =) در پیریت­ ها نشان می­ دهد که پیریت با ترکیب پیچیده [Fe(S,As)₂Au₂S⁰] وجود دارد که در آن As⁻ جانشین S²⁻ شده است. بررسی‌های کانی­ شناسی و فراوانی آهن و گوگرد در واحدهای سنگی کانسار زرشوران نشان می ­دهد که رخداد طلا اغلب با فرایند سولفیداسیون همراه است. سولفیداسیون زمانی رخ می­ دهد که سیالات کانه ­ساز غنی از H₂S با سنگ­ میزبان کربناتی آهن ­دار واکنش داده و کانه ­های پیریت، مارکاسیت یا پیروتیت را تشکیل دهد.

کلیدواژه‌ها

پیریت؛ طلای افشان؛ فرایند سولفیداسیون؛ کربنات آهن‌ دار؛ زرشوران

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