ژئوشیمی ایزوتوپ های Rb-Sr و Nd-Sm و پتروژنز دایک های بازیک کوههای میشو (شمال غرب ایران)

زمین شناسی اقتصادی

مقاله 7، دوره 8، شماره 2 - شماره پیاپی 15، بهمن 1395، صفحه 399-413   

نوع مقاله: علمی- پژوهشی

شناسه دیجیتال (DOI): 10.22067/econg.v8i2.32585

نویسندگان

مریم آهنکوب^{* 1}؛ یوشی هیرو آساهارا²

¹پیام نور واحد شهرکرد

²ناگویا

چکیده

در رشته کوههای میشو، در شمال غرب ایران، مجموعه سنگهای گرانیتی توسط تعدادی دایک‌های بازیک با طول 2 تا 10 متر و پهنای 50 تا 150 سانتی متر قطع شده‌اند. این دایک‌ها دارای کانی شناسی اصلی الیوین، پلاژیوکلاز، پیروکسن هستند. داده‌های ژئوشیمیایی بیانگر ماهیت کالک‌آلکالن این دایک‌ها همراه با تهی شدگی در Nb، Ta و Ti و ویژگی بازالت‌های درون صفحه‌ای هستند که در موقعیت زمین‌ساختی مرتبط با زونهای کششی پس از برخورد تشکیل شده‌اند. نتایج آنالیزهای ایزوتوپی Rb-Sr و Sm-Nd به جای گزینی این دایک‌ها در 232 (میلیون سال) پیش، بیانگر منشأ گوشته تهی شده با کمی اختلاط پوسته‌ای است. مقادیر منفی 4- تا 1 εNd(T) = - و نسبتهای Sr 86Sr/87، انحراف ترکیب شیمیایی ماگمای مادر نسبت به ترکیب آرایه گوشته‌ای را نشان می دهد که دچار آلایش پوسته‌ای شده است. بر اساس میزان εNd(T) ، نسبت ایزوتوپ 87Sr/86Sr اولیه و نسبت ایزوتوپ 144Nd Nd / 143 اولیه سنگ کل نمونه‌ها، به‌دنبال بسته شدن پالئوتتیس در شمال غرب ایران به‌واسطه تشکیل زونهای کششی در درون پوسته قاره‌ای، ماگمای دایک‌های میشو از یک منشأ گوشته تهی شده با غنی شدگی نسبت به عناصر LILE تشکیل‌شده و به‌درون سنگهای گرانیتی تزریق شده‌اند.

کلیدواژه‌ها

داده‌های ایزوتوپی؛ Nd-Sr؛ تعیین سن؛ کالک‌ آلکالن؛ زونهای کششی دایک بازیک؛ کوههای میشو

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