نشریه علوم زمین خوارزمی

نشریه علوم زمین خوارزمی

بررسی دگرشکلی در میکاشیست‌های منطقه غرب سیلوانا، جنوب غرب ارومیه: با نگرشی بر ساختارها و ریزساختارهای تکتونیکی

نویسندگان
شهناز حاتمی نوی
اکرم علیزاده
معصومه آهنگری
دانشگاه ارومیه
10.22034/KJES.2024.9.2.106731
چکیده
میکاشیست‌های رخنمون یافته در منطقه سیلوانا بخشی از مجموعه آمیزه رنگین سیلوانا واقع در جنوب غرب شهرستان ارومیه است. این منطقه از لحاظ تقسیم‌بندی‌های ساختاری جزئی از بخش انتهایی کمربند دگرگونی سنندج- سیرجان در نظر گرفته می‌شود. با توجه به مطالعات سنگ‌شناسی و کانی‌شناسی میکاشیست‌ها را می‌توان به سه گروه مسکویت شیست، بیوتیت مسکویت شیست و فیبرولیت بیوتیت مسکویت شیست تقسیم نمود. وجود برگوارگی میلونیتی و ریزساختارهایی همچون میکای ماهی، تجدید تبلور دینامیکی کانی‌ها، پورفیروکلاست‌های دنباله‌دار، کینک‌باند و چین‌خوردگی نشان از وجود پهنه‌های میلونیتی و عملکرد نیروهای برشی در این منطقه است. با توجه به روابط بافتی و ریزساختارهای موجود، میلونیت‌های موجود از نوع میلونیت‌های درجه پایین تا متوسط هستند. بر اساس روابط ساختاری مشاهده شده در صحرا و ریزساختارهای موجود در سنگ‌ها به نظر می‌رسد سه فاز دگرشکلی مهم در منطقه عمل کرده است. فاز اول به صورت دگرریختی فشارشی عمل کرده و منجر به تشکیل برگوارگی S1 شده است. فاز دوم با مؤلفه اصلی برش ساده راست‌گرد مشخص شده و پهنه‌های میلونیتی و برگوارگی S2 را به وجود آورده است. چین‌ها و ریزچین‌های متعددی در طی این فاز توسعه پیدا کرده است. فاز سوم به صورت دگرشکلی شکننده عمل کرده و شکستگی‌‌ها و ریزگسل‌های متعددی را به وجود آورده است
کلیدواژه‌ها
دگرشکلی
ریزساختار
میلونیت
میکاشیست
سیلوانا
ارومیه

عنوان مقاله English

Investigations of deformation in west of Silvana mica schists, southwest of Urmia: Implications for tectonic structures and microstructures

نویسندگان English

Shahnaz Hatami Noy
Akram Alizadeh
Masoumeh Ahangari
Urmia University
چکیده English

The outcropping mica schists from the Silvana region, which are a component of the Silvana colored mélange complex, are situated southwest of Urmia. This region is located in the northwesternmost part of the Sanandaj-Sirjan metamorphic belt. Mica schists can be classified into three sub-types based on petrographic studies: muscovite schists, biotite-muscovite schists and fibrolite-biotite-muscovite schists. Mylonitic zone can be identified by the presence of mylonitic foliation and microstructures such as mica fish, dynamic recrystallization, asymmetrically tailed porphyroclasts, kink bands, and microfolds. The Silvana mylonites are categorized as low to medium grade mylonites based on textural and microstructural evidence. According to the structural and microstructural relations, the study area appears to have been impacted by three main phases of deformation. The first phase can be characterized by a transpressional deformation regime, leading to the formation of S1 foliation in mica schists. The dextral main simple shear component can be attributed to the second phase. During this phase, S2 foliation, mylonite zones and various folds and microfolds were developed. Ultimately, multiple fractures and microfaults were caused by the third phase of brittle deformation that affected the study area.

کلیدواژه‌ها English

deformation
microstructure
mylonite
mica schist
Silvana
Urmia
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