رمزگشایی تغییرات میدان تنش با استفاده از واکاوی زمین‎ساخت شکننده در گستره شهربابک

نوع مقاله: مقاله پژوهشی

نویسندگان

1 دکترا، گروه زمین‌شناسی، دانشکده علوم زمین، دانشگاه شهید بهشتی، تهران، ایران

2 استاد، گروه زمین‌شناسی، دانشکده علوم زمین، دانشگاه شهید بهشتی، تهران، ایران

3 دانشیار، پژوهشکده علوم زمین، سازمان زمین‌شناسی و اکتشافات معدنی کشور، تهران، ایران

چکیده

در این مقاله بخشی از گستره شهربابک، در شمال باختر استان کرمان مطالعه می‌شود که از دید زمین‌شناسی بخشی از ایران مرکزی و کمربند ارومیه- دختر است. واحدهای سنگی این حوضه در دوران میوسن تحت تأثیر تنش‌های فشاری با روند شمال ‌خاوری قرار گرفته‌اند و دگرشکلی با گسترش چین‌ها وگسل‌ها با روند شمال ‌باختری- جنوب‌ خاوری مشخص می‌شود. هدف این مقاله رمزگشایی دگرشکلی چند مرحله‌ای و تاریخچه تنش دیرینه در بخشی از ایران مرکزی در گستره شهربابک است و اینکه چطور ابعاد مختلف زمین‌شناسی با میدان‌های تنش در طول زمان ارتباط پیدا می‌کنند. از سوی دیگر نشان داده می‌شود که چگونه دگرشکلی‌های شکننده و تحلیل تنش دیرینه می‌تواند در تفسیر تکامل زمین‌ساخت پس از برخورد سودمند باشند. رمزگشایی توالی رویدادها دگرشکلی، که ساختارهای امروزه‌ گستره مورد مطالعه را شکل داده‌اند؛ با استفاده از تحلیل زمین‌ساخت شکننده صورت می‌گیرد که شامل وارون‌سازی تنسور تنش است و از داده‌های لغزش گسل به دست می‌آید. از این رو مطالعه آماری روی رابطه میان میدان‌های تنش مختلف و چین‌خوردگی‌ها صورت گرفت تا از این راه، درک بهتری از تاریخ دگرشکلی فشاری حاکم بر گستره به دست آید. بازسازی سامانه‌ای زمین‌ساخت شکننده اجازه می‌دهد تا یک چرخش پادساعت‎گرد در مسیر اصلی فشارش در طول زمان مشخص شود. به‌طوری ‌که دو مسیر فشاری N55E و N84E از اواخر کرتاسه تا اواخر میوسن پیش از چین‌خوردگی ایجاد شده و فشارش همزمان با چین‌خوردگی N40E در اواخر میوسن شکل گرفته است. پس از چین‌خوردگی، در پلیوسن مسیر فشارش به N29E تغییر وضعیت داد و در پایان در زمان پلیستوسن مسیر فشارش به N3E رسید. اگر چه این چرخش پادساعت‌گرد مسیر تنش فشاری، در طول زمان پیشرونده بوده است؛ تحلیل‌ها نشان می‌دهد که سه رژیم تنشی مشخص؛ پیش، همزمان و پس از چین‌خوردگی وجود داشته و با رویداد فشاری منطبق است. از این رو با تحلیل تنش و مشاهدات صحرایی مشخص شد که بسیاری از گسل‌های راستالغز راست‌بر نسل اول به عنوان گسل‌های معکوس با روند شمال باختر- جنوب خاور در بخش جنوب باختر ایران مرکزی از ناحیه شهربابک فعال شده‌اند. این نتایج می‌تواند توسط فرضیه تغییر چرخش پادساعت‎گرد در مسیر صفحه عربی با توجه به صفحه اوراسیا و چرخش بلوکی ایران مرکزی حمایت شود.

کلیدواژه‌ها


عنوان مقاله [English]

Deciphering the stress field changes in Shahr-e-Babak area using brittle tectonic analysis

نویسندگان [English]

  • L. Ebadi 1
  • S. A. Alavi 2
  • M. R. Ghassemi 3
1 Ph.D., Department of Geology, Faculty of Earth Sciences,Shahid Beheshti University, Tehran, Iran
2 Professor, Department of Geology, Faculty of Earth sciences, Shahid Beheshti University, Tehran, Iran
3 Associate Professor, Reaserch Institute for Earth Sciences, Geological Survey of Iran, Tehran, Iran
چکیده [English]

In this paper a part of the Shahr-e-Babak area in NW-Kerman is studied, which is geologically located in Central Iran and Urumiyeh- Dokhtar Belt. The basin was strongly affected by compression in Miocene times, in which deformation is characterized by development of NW-SE trending fold and thrust belt. In this paper, we aim atdeciphering polyphase deformation and paleostress history of part of the Central Iran in the Shahr-e-Babak area, and that how various geological aspects may be related to a stress field that has been reoriented through time. Also, we indicate how the brittle deformation studies and paleostress analyses may contribute in the interpretations of the post-collisional tectonic evolution of this area. In this paper, by using systematic brittle tectonic analyses, including stress tensor inversion form fault-slip data, we decipher the succession of deformational events that resulted in present-day structures. Therefore, a statistical view of the brittle tectonic reconstructions taken as a whole leads one to better understand the relationships between the different stress fields and folding events that governed the history of compression in this area .The systematic reconstruction of brittle tectonic regimes led us to characterize an anticlockwise change in the main direction of compression through time. Thus, it can be seen that the late Cretaceous to late Miocene pre-folding N055° and N084° compression was followed by syn-folding N040° compression in the Miocene. The Miocene compression then continued into the Pliocene post-folding N029° direction, and changed afterward to the Pleistocene-Recent post-folding N003° direction. Although this general anticlockwise rotation of compression has probably been progressive through time, our data suggest three distinct stress regimes that (1) predate, (2) are contemporaneous with, and (3) post-date the more consistent compressional stress regime of the folding and thrusting process. According to this reconstruction, it is confirmed that many  local right-lateral strike–slip faults were reactivated from NW-SE reverse faults in the Sahahr-e-Babak area of SW Central Iran .These results could properly support the hypothesis of a significant anticlockwise change in the movement direction of the Arabian plate with respect to the Eurasian plate and block rotation in Central Iran.

کلیدواژه‌ها [English]

  • Paleostress
  • brittle tectonic
  • rotation
  • Fold
  • Shahr-e-Babak

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