بررسی ریزساختار کانی‌ها و الگوی جایگیری توده گرانیتوئیدی گراغه بر اساس ناهمسانگردی پذیرفتاری مغناطیسی (AMS)

نوع مقاله : مقاله پژوهشی

نویسندگان

1 گروه پترولوژی و زمین شناسی اقتصادی، دانشکده علوم زمین، دانشگاه صنعتی شاهرود، شاهرود، ایران

2 موسسه زمین شناسی، آکادمی علوم زمین چین، پکن، چین

3 دانشکده علوم زمین، دانشگاه اسلو، اسلو، نروژ

چکیده

توده گرانیتوئیدی گراغه در 90 کیلومتری شمال غرب زاهدان و در شمال­غربی ترین بخش از نوار ماگمایی زاهدان- سراوان قرار دارد. این توده بیشتر از سنگ­های بیوتیت گرانیت و گرانودیوریت تشکیل شده است. سنگ­های تشکیل دهنده بخش­های شمالی و جنوبی توده دارای بافت­های ماگمایی- نیمه ماگمایی هستند. افزون بر آن، این توده دگرشکلی­های دماهای پایین تا بالا چون جوانه زدن و خاموشی صفحه شطرنجی در کوارتز، بافت میرمیکیتی و لغزش در ورقه­های بیوتیت را نشان می­دهد. برای بررسی ناهمسانگردی مغناطیسی، تعداد 519 مغزه جهت­دار از 70 ایستگاه تهیه شد. کانی بیوتیت در این توده عامل اصلی ایجاد پذیرفتاری مغناطیسی بوده که مقدار آن در بخش­های مختلف توده متغیر است. میانگین مقادیر پذیرفتاری مغناطیسی مغزه­های تهیه شده بین 10 تا µSI 301 متغیر است. فاکتور دگرشکلی آن­ها (P < span lang="AR-SA" style="font-size:12.0pt">) بین 8/0 تا 5/15 درصد متغیر است. متغیر شکل در بیشتر نمونه­ها دارای مقادیر مثبت و شکل کلوچه­ای است. شیب برگوارگی­های مغناطیسی در سراسر توده بطور متوسط 31 تا 60 درجه بوده و روند شمال­غرب- جنوب­شرق را نشان می­دهند. موازی بودن راستایی برگوارگی­ها با حاشیه توده و وجود سنگ­های دگرگونی مجاورتی نشان می­دهد که هنگام تزریق ماگما، بیوتیت گرانیت و گرانودیوریت موازی با لایه بندی سنگ میزبان جای گرفته­اند. خطواره­های مغناطیسی با شیب زیاد محل­ اصلی تزریق ماگما تشکیل دهنده توده گرانیتوئیدی گراغه را نشان می دهند که در مرکز توده قرار دارد؛ و سایر بخش­ها می­توانند محل­های فرعی ماگمای تغذیه کننده توده باشد. بر پایه شواهد صحرایی و مغناطیسی به دست آمده، به نظر می رسد که ماگمای مادر توده گرانیتوئیدی گراغه بصورت لاکولیت با شیب 45 درجه در راستایی شمال­شرق به درون سنگ­های میزبان و موازی با لایه بندی آنها جایگیری کرده است.

کلیدواژه‌ها

عنوان مقاله [English]

Microstructure of minerals investigation and the emplacement pattern of Garagheh granitoid pluton using Anisotropy of Magnetic Susceptibility (AMS)

نویسندگان [English]

  • Mehdi Rezaei-Kahkhaei 1
  • Yuruo Shi 2
  • Muriel Erambert 3
  • Habibollah Ghasemi 1
  • Mahmoud Sadeghian 1
1 Department of Petrology and Economic Geology, Faculty of Earth Sciences, Shahrood University of Technology, Shahrood, Iran
2 Institute of Geology, Chinese Academy of Geological Sciences No. 26 Baiwanzhuang Road, Xicheng District, Beijing100037, PR China
3 Department of Geosciences, University of Oslo, PB1047 Blindern, N-0316 Oslo, Norway
چکیده [English]

The granitoid pluton is located about 90 km northwest of Zahedan, in the highest part of the Zahedan-Saravan magmatic belt. Compositionally, the pluton is biotite granite and granodiorite. The rocks forming the northern and southern parts of the pluton have magmatic to sub-magmatic fabric. In addition, our study show low to high temperatures solid-state deformation, such as bulging and chessboard in quartz, myrmikite texture and sliding in biotite. 519 directional cores from 70 stations were collected from the studied area for anisotropy of magnetic susceptibility studies. The mean susceptibility (Km) is from 10-301 µSI. Biotite is the main mineral for magnetic susceptibility in the pluton; where the percentage varies in different parts of the pluton. The P values vary from 0.8-15.5 percent. The T values in most samples are positive and show planner nature. The high degree of dipping of magnetic foliation and lineation, magnetic foliation throughout the pluton are on average from 31 and 60 degrees and shows the northwest-southeast trend. The parallel extension of the lineation with the margin of the pluton and the presence of nearby metamorphic rocks show that during the injection of magma, biotite granite and granodiorite were emplaced parallel to the schistosity of the host rock. In the pluton, the area has magnetic lineation, where a high dip is the main place of magma injection, which is located in the center of the pluton, and other parts can be sub-sites of feeding the pluton. Based on the field observations and magnetic evidence, the parent magmas of the Garagheh granitoid pluton are emplaced as a laccolith with a dip of 45 degrees in the northeast.

کلیدواژه‌ها [English]

  • Zahedan-Saravan magmatic belt
  • Magmatic fabric
  • Anisotropy of magnetic susceptibility (AMS)

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  • تاریخ دریافت: 29 آذر 1402
  • تاریخ بازنگری: 19 دی 1402
  • تاریخ پذیرش: 02 بهمن 1402

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