بررسی همیافتی کانی‌های زوئیزیت و کلینوزوئیزیت در سنگ‌های دگرگون؛ مثالی از اپیدوت-آمفیبولیت‌های جنوب سلماس- شمال غرب ایران

نویسندگان

دانشگاه تبریز

چکیده

زوج کانی­های زوئیزیت و کلینوزوئیزیت به صورت همزیست در اپیدوت- آمفیبولیت­های منطقه سلماس حضور دارند. در این سنگ­ها، زوئیزیت در مقایسه با کلینوزوئیزیت از فراوانی بیشتری برخوردار است. ترکیب این زوج کانی­ها، با یکدیگر متفاوت بوده و دارای مقادیر مختلفی از XPs (عضو انتهایی پیستاسیت) هستند. این مقدار در زوئیزیت کم بوده و در حدود %65/10-46/6 است. مقدار عضو نهایی پیستاسیت برای کلینوزوئیزیت در حدود %73/18-72/16 است. جانشینی Al-Fe3+ در این کانی­ها جانشین مهم و مؤثر در ایجاد تغییرات ترکیب کانی­شناسیست. بررسیهای دما- فشار اپیدوت- آمفیبولیت­های منطقه­ی سلماس، بر اساس مبادلات فازی و واکنش تبدیل زوئیزیت به کلینوزوئیزیت و مقدار عضو انتهایی پیستاسیت در زوج کانی­ها، حاکی از دگرگونی این سنگ­ها در شرایط دمای 20±500 درجه­ی سانتیگراد و فشار7-5/6 کیلوبار است.

کلیدواژه‌ها


عنوان مقاله [English]

Investigations on coexistence of zoisite- clinozoisite in metamorphic rocks; an example from Salmas epidote- amphibolites- NW of Iran

چکیده [English]

Zoisite and clinozoisite are coexistent in the Salmas epidote- amphibolites, NW Iran. The frequency of zoisite is higher than clinozoisite in the studied epidote- amphibolites. The pistacite content of zoisite is lower than clinozoisite. XPs in zoisite is about 6.46-10.65% while for clinozoisite it is about 16.72-18.73%. Al-Fe3+ substitution was effective to create the mineral compositional changes in the Salmas epidote group minerals. Composition of coexisting zoisite and clinozoisite is a function of pressure, temperature and whole rock composition. According to zoisite and clinozoisite phase relations and compositions, epidote- amphibolite metamorphism in the Salmas area occurred at temperature of 500±20 ◦C and pressure of 6.5-7 Kbar conditions.

کلیدواژه‌ها [English]

  • zoisite-clinozoisite coexistence
  • Geothermobarometery
  • epidote- amphibolites
  • Salmas
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