بررسی سنگ نگاری و شیمی کانی‌ها درآپلیت-پگماتیت‌های دره سیمین (جنوب همدان)

نوع مقاله : مقاله پژوهشی

نویسندگان

دانشگاه بوعلی سینا

چکیده

دایک­های آپلیتی -پگماتیتی موجود در جنوب شرقی همدان، در منطقه سیمین از لبه به سمت مرکز دو منطقه بافتی ویژه دارند که به خوبی اثر پیشرفت تبلور را در این دایک­ها نشان می­دهند: 1- منطقه حاشیه با ساخت­های ناهمسان شامل واحدهای دانه­ریز، هم رشدی گرافیکی و ساخت­های انجماد یک جهته و 2- منطقه داخلی با ساخت­های توده­ای و درشت بلور. تجزیه­­های ریزپردازشی برای کانی­های تورمالین، پلاژیوکلاز و فلدسپار پتاسیم انجام شد. تورمالین­ها دارای ترکیب شورلیت هستند. در نمودار FeO/(FeO+MgO) نسبت به MgO که خاستگاه تورمالین­ها را مشخص می­کند، تورمالین­های مورد بررسی دارای Fe# بین 8/0 تا 1 هستند که نشان دهنده­ی تشکیل آنها در یک سیستم ماگمایی و دخالت نداشتن سیال­های خارجی در تشکیل آنها­ست. ترکیب پلاژیوکلازهای مورد بررسی  غنی از آلبیت (Ab90-100) بوده و فلدسپارهای پتاسیم نیز دارای 97-92 درصد فلدسپار پتاسیم هستند. این امر نشان دهنده پیشرفت تبلور جدایشی در ماگمای وابسته است. منطقه بندی موجود در تورمالین­های مورد بررسی هم در مقاطع نازک و هم در تجزیه های شیمیایی به خوبی مشهود است. در فلدسپارهای مورد بررسی، مقادیر نسبتاً بالای Rb (ppm 1319) و همچنین Cs (ppm 205) نشان دهنده­ی درجه جدایش بالا در  ماگمای وابسته است.     

کلیدواژه‌ها

عنوان مقاله [English]

The study of petrography and mineral chemistry in aplite-pegmatites from Simin valley (south of Hamedan)

نویسندگان [English]

  • Ali Asghar Sepahi
  • Sedigheh Salami
  • Mohammad Maanijou
چکیده [English]

Aplitic and pegmatitic dykes  exposed in southeast of Hamedan in the Simin area. From the margin to the center of these dykes, two typical textural areas present that obviously indicate effect of crystallization progress: 1- In the marginal zone, fabrics consist of anisotropic textures of the outer zones, including fine-grained units, graphic intergrowths, and unidirectional solidification textures and 2- In the interior zone that have coarse, blocky textures. Microprobe analysis performed on tourmaline, plagioclase and K-feldspar minerals. Tourmalines have schorlite composition. In the FeO/(FeO+MgO) vs. MgO diagram that determine origin of tourmalines, the studied tourmalines have Fe# between 0.8 to 1 that indicates they formed in magmatic conditions and external hydrothermal fluids and don’t take part in their genesis. Compositions of analyzed plagioclases are albite-rich (Ab90-100) and K-feldspars have 92-97 percent K-feldspar. This  indicates  progress of fractional crystallization  which is related to magma. Studied of tourmaline zoning is well visible at thin sections and in the chemical analyses. In the analyzed feldspars, high amount of Rb (1319 ppm) and also Cs (205 ppm) indicate high degree of fractionation which is related to magma.

کلیدواژه‌ها [English]

  • aplite
  • pegmatite
  • fractional crystallization
  • zoning
  • Simin
  • Sanandaj-Sirjan Zone

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  • تاریخ دریافت: 01 اسفند 1397
  • تاریخ بازنگری: 03 اردیبهشت 1398
  • تاریخ پذیرش: 12 خرداد 1398

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