نشریه علوم زمین خوارزمی

نشریه علوم زمین خوارزمی

آنالیز تکتونیکی مرز خمیده شمالی پهنه سیستان با بلوک لوت در شمال بیرجند

نویسندگان
شهریار کشتگر 1
محمودرضا هیهات 1
ساسان باقری 2
ابراهیم غلامی 1
سیدناصر رئیس السادات 1
1 دانشگاه بیرجند
2 دانشگاه سیستان و بلوچستان
10.22034/KJES.2024.9.2.104162
چکیده
ساختار ‌چین‌خورده-رانده خمیده شمال بیرجند متشکل از رخنمون‌های اندکی از سازندهای پالئوزوئیک بالایی، تریاس و کرتاسه همراه با توالی‌های سنوزوئیک است که دچار چندین مرحله دگرریختی شده‌اند. راندگی، چین‌های موازی و شعاعی بزرگ مقیاس، تورق برشی نافذ، بازمانده‌های تکتونیکی، شکستگی‌های کششی وگسل‌های امتدادلغز مزدوج، در این قوس ساختاری رخنمون دارند. منطقه چاه‌حوض که در یال شرقی ساختار چین رانده وجود دارد، متشکل از برگه‌های راندگی متوالی در ملانژها و لیستونیت‌های کرتاسه بالایی است که امتداد شمال غرب و شیب به سمت شمال شرق دارند. درمنطقه موسویه، سه توالی مجزا شامل سنگ‌های دگرگونی قدیمی‌تر از کرتاسه مربوط به پی‌سنگ لوت، مجموعه افیولیت و توربیدایت کرتاسه، و سنگ آهک‌های پلاتفرمی ائوسن وجود دارد. شیب صفحات راندگی در بخش بیرونی قوس به سمت SSE و در بخش درونی قوس عموماً به سمت NNW است که جهت انتقال زمین‌ساختی به سمت داخل قوس نشان می‌دهند. مرز ناگهانی بین نهشته­های قاره­ای ائوسن- الیگوسن در شمال این قوس یا از نوع راندگی است و یا توسط چین‌های با دامنه­های بزرگ مشخص می­شود که از دو نوع هستند: نوع اول چین‌های موازی با حاشیه قوس می­باشند که اغلب سیلندری بوده اما تحت تأثیر نسل جوان‌تر چین­خوردگی، غیرسیلندری شده­اند و نوع دوم چین‌های مخروطی با آرایش شعاعی هستند که رأس مخروط آنها به سمت NNW پلانژ دارد. بنابراین به نظر می‌رسد ساختارهای مرز خمیده شمالی لوت و سیستان از مدل ساختارهای رایج در کوهزادهای برخوردی خطی (بازشدگی پوسته قاره‌ای شرق ایران و برخورد خطی بلوک‌های لوت و افغان) تبعیت نمی‌نماید. بر اساس نتایج این پژوهش، به نظر می‌رسد حرکت رو به شمال­غرب پلاتفرم شمال بیرجند و خمش همزمان آن در اواخر ائوسن- الیگوسن عامل ایجاد دگرشکلی‌های متنوع بوده است.
کلیدواژه‌ها
آنالیز تکتونیکی
خمش
راندگی
چین مخروطی
لوت
شرق ایران

عنوان مقاله English

Tectonic analysis of curved northern border of the Sistan zone with the Lut Block, north of Birjand

نویسندگان English

shahriar keshtgar 1
Mahmoud Reza Heyhat 1
Sasan Bagheri 2
Ebrahim Gholami 1
Seyed Naser Raiisosadat 1
1 University of Birjand
2 University of Birjand
چکیده English

The curved fold-thrust belt of North Birjand contains some outcrops of Upper Paleozoic to Cenozoic sequences that have undergone several stages of deformation. Thrusting, large-scale parallel and radial folds, penetrative shear cleavage, tectonic klippes, tensile fractures, and conjugate strike-slip faults are exposed in this structural arc. The Chah-hoz region consists of Upper Cretaceous mélanges and listvenites with NW-trending thrust sheets dipping to the NE. The Mousavieh area includes pre-Cretaceous metamorphic rocks belonging to the basement of the Lut block, Cretaceous ophiolite, and turbidite complex, and Eocene platform limestone. The dip of thrust planes in the outer part of this arc is SSE and in the inner part of the arc is generally NNW indicating the direction of regional tectonic transport towards the interior of the arc. The abrupt boundary between the Eocene-Oligocene continental deposits in the north of this arc is either thrust or characterized by two types of major folds: The first type is the parallel folds with the edge of the arc, which are often cylindrical, but under the influence of the younger generation folds, they have become non-cylindrical, and the second type is the conical folds with a radial arrangement, the apex of the cone is plunged towards the NNW.

Therefore, it seems that the structures of the northern curved border of the Lut and Sistan terrains do not follow the model of common structures in linear collision mountains i.e., eastern Iran continental crust rifting and subsequent linear collision of the Lut and Afghan blocks. According to this research, it seems that the NW movement of the North Birjand platform was caused by buckling in the Late Eocene-Oligocene.

کلیدواژه‌ها English

Tectonic analysis
Buckling
Thrust
Conical fold
Lut Block
eastern Iran
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