بافت های اسکلتی، میکرواسپینیفکس و هاریسیت در سیل ها و گدازه های کماته ایتی پالئوزوئیک بالایی مشهد- ویرانی، شمال خاوری ایران

نوع مقاله : علمی- پژوهشی

نویسندگان

1 دانشگاه صنعتی شاهرود

2 دانشگاه فردوسی مشهد

چکیده

بافت­‌های اسکلتی، میکرواسپینیفکس و هاریسیت به‌عنوان نخستین شواهد بارز از وجود گدازه‌­ها و سیل­‌های کم‌عمق کماته‌­ایتی در همتافت مشهد- ویرانی گزارش شده‌اند. این همتافت که تاکنون به‌عنوان توالی افیولیتی منظور‌ ­شده است، از نظر سنگ­‌شناسی شامل سیل­‌های ورلیتی- گابرویی و پیروکسنیتی­، سیل‌­ها و دایک­‌های آمفیبول گابرویی و روانه­‌های تفریق­‌یافته­ کماته­‌ایت بازالتی با بافت­‌های میکرواسپینیفکس است که در تناوب با لایه­‌های رسوبی دگرگون‌شده پالئوزوئیک بالایی قرار دارند. برای نخستین‌بار، بافت­‌های ناتعادلی اسپینیفکس و هاریسیت در این سیل‌­های کم‌عمق ورلیتی- گابرویی و سنگ‌­های خروجی یافت و گزارش شده‌اند. نرخ سردشدگی و گرادیان حرارتی در سنگ­‌های خروجی و اَبَرسیر­شدگی، گاززدایی و اختلاط ماگمایی در سنگ­‌های نفوذی کم‌عمق از مهم‌ترین عوامل ایجاد بافت‌های ناتعادلی بوده‌­اند. بررسی­‌های دما- فشارسنجی بر روی آمفیبول گابروهای این همتافت بیانگر فشار میانگین 4/2 کیلوبار و دمای میانگین 1222 درجه سانتی­‌گراد برای تبلور آنهاست که با شواهد صحرایی، سنگ‌­نگاری و شرایط تبلور این‌گونه از ماگماها کاملاً سازگار است.

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