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ترموبارومتري آمفيبوليت‌هاي سيرجان براساس محتواي Zr در کاني اسفن(تيتانيت) و روتيل
الهام صفرزاده, فریبرز مسعودی, سید محمد پورمعافی

چکیده

بخشي از کمپلکس دگرگوني جنوب سيرجان را توده‌هاي آمفيبوليتي تشکيل داده‌است. اين توده‌ها بصورت هميافت با گارنت مسکوويت‌ شيست‌ها و هورنبلند شيست‌ها در منطقه ديده مي‌شوند. ترکيب سنگ شناسي آن‌ها شامل آمفيبول از نوع مگنزيو‌ هورنبلند تا چرماکيت، پلاژيوکلاز سديک (Ab70)، کوارتز  و کاني‌هاي فرعي اپيدوت،  بيوتيت، اسفن و روتيل است. در اين تحقيق با استفاده از محتواي Ti و Zr در کاني‌هاي اسفن و روتيل شرايط  فشار و حرارت تشکيل اين سنگ‌ها مورد بررسي قرار گرفته‌است. نتايج آناليز نقطه­اي انجام شده برروي کاني­هاي اسفن و روتيل در نمونه‌هاي انتخاب شده، بطور متوسط  Zr= 317.57 ppm, TiO2= 37.23 wt% براي کاني اسفن و Zr= 439.57 ppm, TiO2= 98.48 wt%  براي کاني روتيل است. ترموبارومتري اسفن و روتيل نشان مي‌دهد که محدوده فشار- دمايي اين آمفيبوليت‌ها براساس کاني اسفن T= 608-691ºC  و براساس کاني روتيل T=572-723ºC، P=7.6- 9 Kbar است. براساس اين نتايج و تطابق آن‌ها با محدوده رخساره‌هاي مختلف دگرگوني مي‌توان گفت اين آمفيبوليت‌ها در طي دگرگوني ناحيه‌اي و شرايط رخساره آمفيبوليت درجه بالا تشکيل شده‌اند.

 

Abstract

Part of the metamorphic complex of south of Sirjan consist of amphibolite units. In this region, amphibolites are found with garnet muscovite schist and hornblende schist. Their lithological compositions include amphibole with magnesio-hornblende and tschermakite composition, sodic plagioclase (Ab70), epidote, quartz and biotite, with sphene and rutile as minor minerals. In this study, temperature and pressure conditions of amphibolite are evaluated by using Ti and Zr content in the rutile and sphene, minerals. The electron microprobe analysis of sphene and rutile minerals on selected samples show, the average of Zr= 317.57 ppm, TiO2= 37.23 wt% in sphene and Zr = 439.57 ppm, TiO2 = 98.48 wt% in rutile. Thermobarometry of sphene and rutile show that the range of temperature and pressure of the amphibolites based on sphene is T = 608-691ºC and based on rutile is T = 572-723ºC, P = 7.6- 9 Kbar. Based on these results and compatibility with the range of different metamorphic facieses, amphibolites were formed during regional metamorphism in high grade amphibolite facies.

 

Keywords: Amphibolite, Thermobarometry, Sphene, Rutile, Sirjan metamorphic complex.

واژگان کلیدی
آمفيبوليت، ترموبارومتري، اسفن، روتيل، کمپلکس دگرگوني سيرجان.

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