پتروگرافی و ترکیب شیمیایی دولومیت‌ها در کانسار سرب و روی خان‌سرمه و ارتباط آن با رخداد کانه‌زایی سولفیدی در منطقه واقع در غرب اصفهان

نویسنده

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

چکیده

کانسار خان‌سرمه واقع در غرب اصفهان به عنوان یکی از ذخایر مهم در ایالت فلززایی ملایر-اصفهان در میزبان واحد کربناته کرتاسه‌زیرین (واحد K3)، قرار دارد. در این کانسار گالن، اسفالریت و پیریت فراوانترین کانه‌های سولفیدی هستند که به همراه دگرسانی‌های دولومیتی-شدن، سولفیدی و سیلیسی تشکیل شده‌اند. طبق مطالعات پتروگرافی، دست کم چهار نوع دولومیت به ترتیب شامل دولومیت‌های‌ ریزبلور خاکستری (Rd1)، متوسط بلور قهوه‌ای تا قرمز (Rd2)، درشت بلور زین اسبی (Sd) و رگه‌-رگچه‌ای تأخیری (Vd)، در سنگ میزبان کانه-زایی تشخیص داده شد. محتوای CaCO3 و MgCO3 در این دولومیت‌ها به ترتیب بین 5/58 تا wt% 3/61 و بین 6/37 تا wt% 2/40 در تغییر بوده که بیشترین نسبت مولار Ca/Mg در دولومیت‌های اولیه ریزبلور (متوسط 65/1) و کمترین آن متعلق به دولومیت‌های رگه‌ای تأخیری (متوسط 1/1)، است. همچنین، مجموع مقادیر عناصر نادرخاکی (∑REE) در دولومیت‌ها بین 8/5 تا ppm 9/13 در تغییر است که این میزان در دولومیت‌های ریزبلور و زین اسبی بیشتر از دولومیت‌های متوسط بلور و رگه‌ای، بدست آمد. بر مبنای الگوی توزیع REE بنظر می‌رسد، دولومیت‌های ریزبلور از سنگ میزبان کرتاسه‌زیرین شکل گرفته‌اند. همچنین، وجود غنی‌شدگی نسبی LREE و بویژه La در دولومیت‌های زین اسبی و رگه‌ای گویای تشکیل این دولومیت‌ها در شرایط سیال به سنگ بالا و ارتباط آنها با رخداد کانه‌زایی سولفیدی در کانسار خان‌سرمه است.

کلیدواژه‌ها


عنوان مقاله [English]

Petrography and chemical composition of dolomites in the Khan Sormeh Pb-Zn deposit (western Isfahan) and relationship with sulfide mineralization

نویسنده [English]

  • E. Tale Fazel
چکیده [English]

The Khan Sormeh deposit is located at western Isfahan, within the Lower Cretaceous carbonate rocks (K3 unit) which belongs to Malayer-Esfahan Metallogenic Province (MEMP). Galena, sphalerite and pyrite occurs as the main sulfide minerals in the study area and mostly were distinguished with dolomitization, sulfidation and silicic alterations. Based on petrographic evidence, at least four types of dolomite are recognized at carbonate host rocks, including: grey fine-grain dolomite (Rd1), brown-red medium-grain dolomite (Rd2), coarse-grain saddle dolomite (Sd) and vein and veinlet late dolomite (Vd). The CaCO3 and MgCO3 content of dolomites are varies between 58.5 to 61.3 wt% and 37.6 to 40.2 wt%, respectively. The highest and lowest molar ratio of Ca/Mg are distinguished in fine-grain dolomite (AV. 1.65) and vein-type dolomite (AV. 1.1), respectively. Also, total REE content (∑REE) of dolomite are varies between 5.8 to 13.9 ppm, which this variation have high content in fine-grain and saddle dolomites relative to medium-grain and vein-type dolomites. REE distribution in various dolomites is shown the fine-grain dolomite is very similar pattern to Lower Cretaceous host rock. Moreover, LREE enrichment (especially La) of the saddle and vein-type dolomites shows this dolomites occurs in high water rock ratio and its belong to sulfide mineralization in the Khan Sormeh deposit.

کلیدواژه‌ها [English]

  • geochemistry of dolomite
  • sulfide mineralization
  • Pb-Zn
  • hydrothermal fluid
  • Khan Sormeh

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