بررسی چگونگی تشکیل گارنت‌های صنعتی در گارنت میکاشیست‌های جنوب الوند، همدان، ایران

نوع مقاله : مقاله پژوهشی

نویسندگان

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

چکیده

منطقه جوکار  در جنوب شرق استان همدان در پهنه سنندج-سیرجان واقع است. واحدهای سنگی منطقه شامل واحدهای سنگی گارنت شیست و فیلیت هستند. در بررسی­های میکروسکوپی، کوارتز، بیوتیت، مسکویت وگارنت دیده شد. گارنت­ها دو نسل شامل گارنت‌های پیش از همزمان با  فعالیت زمین­ساخت و گارنت‌های همزمان با  فعالیت زمین­ساخت دارند. تجزیه به روش ریزپردازش الکترونی (EPMA) نشان داد که منطقه­بندی گارنت‌ها ازنوع آلماندین، گراسولار، اسپسارتین و آندرادیت است. گارنت­ها بدون منطقه­بندی فیزیکی ولی دارای منطقه­بندی شیمیایی هستند. مقدار عناصر Mn و Ca از مرکز به سمت لبه بلور کاهش و Fe افزایش می‌یابد. پنج نوع میانبار تک فازی مایع (L)، تک فازی گازی (V)، دوفازی مایع و بخار (L+V)، سه فازی جامد (L+V+S) و چهارفازی جامد (L+V+S1+S2) دیده شده است. دمای همگن­شدگی میانبارهای سیال در نمونه­ها 322 تا oC 485  است. همچنین مقادیر شوری میانبارهای سیال 7/5 تا 6/19 درصد وزنی معادل نمک طعام بدست آمد. چگالی سیال سازنده گارنت­ها 569/0 تا gr/cm3 842/0 است. سیال سازنده گارنت­ها خاستگاه ماگمایی و دگرگونی دارد.

کلیدواژه‌ها


عنوان مقاله [English]

Study of the formation of industrial garnets in garnet micaschists south of Alvand, Hamadan, Iran

نویسندگان [English]

  • Mehrdad Barati
  • Sosan Ebrahimi
  • Behrouz Rafiei
Department of Geology, Faculty of Science, Bu-Ali Sina University of Hamadan, Hamedan, Iran
چکیده [English]

The Jokar region is located in the southeast of Hamedan province in the Sanandaj-Sirjan zone. The rock unit of the region includes garnet schist and phyllite rock units. Quartz, biotite, muscovite and garnet were observed in microscopic examination. Garnets have two generations including garnets before and during tectonic activity and garnets during tectonic activity. EPMA analysis showed that the zoning of garnets is almandine, grossular, spessartine and andradite. Garnets have no physical zoning but have chemical zoning. Mn and Ca elements decrease from the center to the crystal edge and Fe increases. Five types of intercalation (L), (V), (L+V), (L+V+S) and (L+V+S1+S2) have been observed. The homogenization temperature of the inclusions in the samples is between 322 and 485 oC. Also, the salinity values ​​of the inclusions were found to be between 5.7 and 19.6% by weight equivalent to table salt. The density of the fluid forming garnets is between 0.569 and 0.842 g/cm3. The fluid forming garnets has a magmatic and metamorphic origin.Keywords: Micaschist garnet, chemical zoning of garnet, magmatic metamorphic origin.

کلیدواژه‌ها [English]

  • Micaschitic garnet
  • chemical zoning of garnet
  • magmatic and metamorphic origins
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