ژئوشیمی ایزوتوپی Sr-Nd و سن سنجی 40Ar-39Ar و Rb-Sr گرانیت‌های نوع A2 قوشچی، شمال ارومیه، شمال باختر ایران

نوع مقاله: مقاله پژوهشی

نویسندگان

1 دانشجوی کارشناسی ارشد، دانشکده علوم زمین، دانشگاه دامغان، دامغان، ایران

2 استادیار، دانشکده علوم زمین، دانشگاه دامغان، دامغان، ایران

3 دانشیار، دانشکده علوم زمین، دانشگاه دامغان، دامغان، ایران

چکیده

سنگ‌های گرانیتی مجموعه قوشچی در شمال ارومیه بیشتر شامل آلکالی­فلدسپارگرانیت‌ها، گرانیت‌ها و دایک‌های آپلیتی هستند؛ با ماهیت کالک­آلکالن پتاسیم بالا تا شوشونیتی و غنی از آهن مشخص می­شوند و به گروه گرانیت­های A تعلق دارند. این سنگ­ها دارای مقادیر K2O+Na2O، FeO/MgO، Ga/Al، Ce/Nb، Zr و Y/Nb بالا و مقادیر CaO، Ba، Sr و Eu پایین و از نوع گرانیت­های نوع A2 هستند. شواهد ژئوشیمیایی و ایزوتوپی Sr-Nd، تبلور تفریقی شدید از مذاب‌های مشتق شده از گوشته غنی ­شده همراه با آغشتگی پوسته را آشکار می­سازد و محیط تشکیل آنها با موقعیت‌های کششی پس از برخورد درون صفحه­ای همخوانی دارد. سن­سنجی آرگون- آرگون روی کانی بیوتیت و Rb-Sr سنگ کل در سنگ­های گرانیتی به ترتیب نشان­دهنده سن کمینه 27±262 و20 ±256 میلیون سال و سن تبلور 330 تا 320 میلیون سال است و احتمالاً این گرانیت­ها در پهنه­های کششی در مراحل پایانی رویدادهای زمین ساختی کوهزایی واریسکن (Variscan) شکل گرفته­اند.

کلیدواژه‌ها


عنوان مقاله [English]

Sr-Nd isotopic geochemistry and 40Ar-39Ar and Rb-Sr dating of Ghoshchi A2-type granites, N Uromiyeh, NW Iran

نویسندگان [English]

  • Sh. Shahabi 1
  • H. Shafaii Moghadam 2
  • Gh. Ghorbani 3
1 M. Sc. Student, School of Earth Sciences, Damghan University, Damghan, Iran
2 Assistant Professor, School of Earth Sciences, Damghan University, Damghan, Iran
3 Associate Professor, School of Earth Sciences, Damghan University, Damghan, Iran
چکیده [English]

The Ghoshchi granitic rocks are located in at north of Uromiyeh city and are mainly composed of alkali-feldspar granites, granites and aplitic dykes. These samples belong to calc-alkaline to shoshonitic series and show Fe enrichment and are classified as A-type granites. Ghoshchi granites have high K2O+Na2O, FeO/MgO, Gl/Al, Ce/Nb, Zr, Y/Nb, and low CaO, Ba, Sr and Eu and are A2-type granites. Geochemical and Sr-Nd isotopes evidences suggest that these rocks were generated by highly fractional crystallization of a parental magma (melts), was derived  from an enriched mantle source, which have undergone contamination by crustal materials and formed in post-collisional extentional environments in a within-plate setting. The crystallization age of these rocks, according to biotite 40Ar-39Ar and Rb-Sr dating is 262±26 Ma  and 256±20 Ma, as minimum age, respectively, and 320-330 Ma as crystallization age. Ghoshchi granites formed probably within extentional zones in at the late stages of Variscan tectonic events.

کلیدواژه‌ها [English]

  • petrology
  • 40Ar-39Ar Dating
  • Sr-Nd isotopes
  • A2-type granite
  • Ghoshchi

کتابنگاری

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