یافته‌های نوین زمین‌شناسی کاربردی

یافته‌های نوین زمین‌شناسی کاربردی

بررسی شرایط دما- فشار- سیال گابروی ناحیه سیلوانا در جنوب ارومیه بر اساس شیمی بلورها

نویسنده
دانشیار گروه زمین‌شناسی، دانشکده علوم‌پایه، دانشگاه ارومیه، ارومیه، ایران
چکیده
در این نوشتار بر روی گابروی مرتبط با افیولیت سیلوانا در جنوب ارومیه تمرکز شده است. هدف از این مطالعه، بررسی شیمی کانی­های تشکیل­دهنده و احصاء اطلاعات از نحوه تشکیل این گروه سنگی با استناد به شیمی بلورها می­باشد. گابروی منطقه سیلوانا به­ صورت توده­ای درون واحدهای الترامافیک سرپانتینی شده در منطقه نفوذ کرده و به­ همراه سایر اجزاء افیولیت درون آمیزه رنگی در امتداد گسل اسبی­بنار برونزد یافته است. گروه سنگی غالب از نوع گابرو تا هورنبلند گابرو بوده و فازهای اصلی آن شامل کلینوپیروکسن، آمفیبول، پلاژیوکلاز و کانی­های تیره می­باشد. به­علاوه مقادیری بیوتیت، تیتانیت، کلسیت و آپاتیت نیز در حد فرعی و متفرقه در سنگ­ها دیده می­شوند. نتایج تجزیه نقطه­ای نشان می­دهد ترکیب کلینوپیروکسن در این گابرو، دیوپسیدی، آمفیبول از نوع پارگازیتی-کرسوتیتی، پلاژیوکلاز آنورتیتی، کانی تیره ایلمنیتی و بیوتیت فلوگوپیتی بوده است. ترکیب شیمیایی دو فاز آمفیبول و کلینوپیروکسن معرف تشکیل این توده گابرویی در یک محیط فرافرورانشی/جلوی قوسی می­باشد. همچنین فشاربخشی سیال اکسیژن/آب در ماگمای مولد بالا ارزیابی شده است. دمای تبلور آمفیبول در این گابروها 800 تا 1000 درجه سانتی­گراد در فشار حدود 5 تا 8 کیلوبار و دمای تبلور برای کلینوپیروکسن 1150 درجه سانتی­گراد در فشار پایین ارزیابی شده است.
کلیدواژه‌ها

عنوان مقاله English

Investigations on the Silvana region gabbro, south of Urmia, pressure- temperature- fluid conditions based on the crystal chemistry

نویسنده English

M. Modjarrad
Assoc. Prof., Dept., of Geology, Faculty of Science, Urmia University, Urmia, Iran
چکیده English

In this manuscript, we focused on the Silvana ophiolite-related gabbro, south of Urmia. The essential aim is studying constituent minerals classification and understanding formation conditions of this rock type based on the mineral chemistry. The mentioned gabbro was intruded in the serpentinized ultramafic unit in the area and outcropped along the Asbi Bunar fault as colored mélange accompanied by other ophiolitic members. Abundant rock types are gabbro and hornblende gabbro with clinopyroxene, amphibole, plagioclase, and ore minerals as major minerals. Additionally, some biotite, calcite and apatite as minor or accessory phases exist. Clinopyroxenes composition in these rocks is diopsidic, amphiboles are parasitic-kaersutite, plagioclases are anorthite-rich, opaque minerals are ilmenite and biotites are phlogopitic, based on the EPMA analyses. Mineral chemistry of both amphibole and clinopyroxene in the studied gabbro, shows a supra subduction zone/fore-arc setting for them. Also, the oxygen/water fugacity of the parent magma was high. The crystallization temperature of 800-1000 ⁰C at the 5-8 kbar pressure using amphibole composition and 1150 ⁰C at low pressure by clinopyroxene are evaluated.

کلیدواژه‌ها English

gabbro
supra subduction zone setting
crystal chemistry
fluid fugacity
Silvana
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  • تاریخ دریافت 31 تیر 1403
  • تاریخ بازنگری 21 مهر 1403
  • تاریخ پذیرش 23 مهر 1403