سنگ‌نگاری و ژئوشیمی دولومیت‌های سازند شتری در برش کلمرد، ایران مرکزی

نوع مقاله: مقاله پژوهشی

نویسندگان

1 دانشجوی دکترا، گروه زمین‎شناسی، دانشکده علوم پایه، واحد تهران شمال، دانشگاه آزاد اسلامی، تهران، ایران

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

3 دانشیار، گروه زمین‎شناسی، دانشکده علوم پایه، واحد تهران شمال، دانشگاه آزاد اسلامی، تهران، ایران

4 استادیار، پژوهشکده علوم زمین، سازمان زمین‌شناسی و اکتشافات معدنی کشور، تهران، ایران

5 دکترا، مدیریت اکتشاف، اداره زمین‎شناسی سطح الارضی، شرکت ملی نفت، تهران، ایران

چکیده

توالی‌های کربناته سازند شتری به سن تریاس میانی با ستبرای 308 متر در ناحیه کلمرد شهرستان طبس در حوضه ایران مرکزی نهشته شده است. در این ناحیه مرز پایینی سازند شتری به‎طور تدریجی و همشیب روی سازند سرخ شیل و مرز بالایی آن توسط گسل قطع شده است و به‎طور عمده شامل دولومیت‌ با ستبرای کل 250 متر به‎صورت متوسط تا ستبرلایه همرا ه با میان‌لایه‌های نازک آهکی و ماسه‌سنگی است. سازند شتری به‎طور چیره شامل دولومیت‎های ریز تا درشت‌بلور است. بر پایه شواهد سنگ‎نگاری (اندازه دانه و فابریک) و ژئوشیمیایی (تجزیه‌‌های عنصری Ca, Mg, Na, Sr, Fe, Mn)5 نوع مختلف دولومیت در سازند شتری تشخیص داده شده است. دلیل گوناگونی دولومیت‌ها، تأثیر فرایندهای دیاژنزی اولیه و تأخیری است که سبب تغییر ترکیب سیال‎های دولومیت‎ساز و در نتیجه تشکیل انواع دولومیت‌ها شده است. مطالعات ژئوشیمیایی نشان می‎دهد که دولومیت‌های سازند شتری بیشتر در شرایط احیأ و تحت تأثیر دیاژنز متائوریکی تشکیل شده‎اند. مکانیسم دولومیتی شدن برای دولومیت نوع اول مدل سبخا، دولومیت‌های نوع دوم و سوم مدل پهنه مخلوط و برای دولومیت‌های نوع چهارم و پنجم مدل تدفینی در نظر گرفته شده است.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Petrography and geochemistry of the Shotori dolomites in Kalmard section, Central Iran

نویسندگان [English]

  • A. Rahimi 1
  • M. H. Adabi 2
  • A. Nabati 3
  • M. R. Majidifard 4
  • A. M. Jamali 5
1 Ph.D. Student, Department of Geology, Faculty of Basic Sciences, North Tehran Branch, Islamic Azad University, Tehran, Iran
2 Professor, Department of Geology, Faculty of Earth Sciences, Shahid Beheshti University, Tehran, Iran
3 Associate Professor, Department of Geology, Faculty of Basic Sciences, North Tehran Branch, Islamic Azad University, Tehran, Iran
4 Associate Professor, Department of Geology, Faculty of Basic Sciences, North Tehran Branch, Islamic Azad University, Tehran, Iran
5 Assistant Professor, Research Institute for Earth Sciences, Geological Survey of Iran, Tehran, Iran
چکیده [English]

Carbonate sequences of the Shotori Formations (Middle Triassic) with a thickness of 308 m, were deposited in the Kalmard region of the Tabas city in Central Iran basin. The lower contact of the formation gradually and conformably overlies the Sorkhshale Formation and upper contact is faulted. The Shotori Formation is mainly composed of thick to medium bedded fine-coarsely crystalline dolomites with a thickness of 250 m  with interbeds  of thin bedded limestone and sandstone. The Shotori Formation is mainly composed of fine-coarsely crystalline dolomite. Based on petrographic (size and fabric), and elemental studies (Ca, Mg, Na, Sr, Fe, Mn), five dolomite types were recognized. Variation in dolomite types is mainly related to early to late diagenetic processes, changing the composition of dolomitizing fluids. Geochemical studies also indicate that medium to coarse grain dolomites formed in meteoric diagenesis under reducing conditions. Mechanism of dolomitization for dolomite type 1 is sabkha model, for dolomite types 2 and 3 is mixing zone and is burial model for dolomite types 4 and 5.

کلیدواژه‌ها [English]

  • Petrography
  • Geochemistry
  • Dolomitization
  • Shotori Formation
  • Central Iran

کتابنگاری

آدابی، م. ح.، 1390- ژئوشیمی رسوبی، انتشارات آرین زمین، چاپ دوم، 504 ص.

اژدری، ع.، 1378- نقشه زمین‎شناسی رباط خان، مقیاس 1000000/1، سازمان زمین شناسی و اکتشافات معدنی کشور، تهران، ایران.

رحیمی، ا.،  1395- محیط‎های رسوبی، چینه‌نگاری سکانسی، دیاژنز و ژئوشیمی سنگ های تریاس زیرین- میانی در بلوک کلمرد (ایران مرکزی) رساله دکتری تخصصی، دانشگاه آزاد واحدتهران شمال، 303 ص.

 

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