سنگ‌نگاری، ژئوشیمی و جایگاه زمین ساختی گدازه‌های ائوسن زندیه-راویز (شمال غرب رفسنجان)

نویسندگان

دانشگاه شهید باهنر کرمان

چکیده

منطقه­ی مورد بررسی، در 35 کیلومتری شمال غرب رفسنجان (استان کرمان) قرار دارد و بخشی از مجموعه آتشفشانی همبافت هزار (کمربند ارومیه-دختر) بوده و شامل تناوب چین خورده­ای از گدازه­ها (بازالت، پیروکسن آندزیت و آمفیبول آندزیت)، و پیروکلاستیک­های ائوسن است. بررسی­های سنگ نگاری نشان می­دهد که در این سنگ ها از درشت بلورهای پلاژیوکلاز با بافت­های غیر تعادلی از قبیل غربالی، تحلیل یافتگی و منطقه بندی نوسانی تشکیل شده­اند. شواهد یاد شده نشانگر وجود فرآیندهایی نظیر اختلاط ماگمایی و تغییرات فشار بخار آب و کاهش فشار، هنگام صعود ماگماست. بررسی­های ژئوشیمیایی نشان می­دهد که گدازه­های منطقه در سری آهکی-قلیایی قرار داشته و جدایش گسترده­ای در آن­ها صورت نگرفته است. غنی شدگی از عناصر نادر خاکی سبک (LREE) در مقایسه با عناصر نادر خاکی سنگین (HREE)، و بالا بودن مقدار عناصر ناسازگار LIL نسبت به HFS و نیز بی هنجاری منفی شاخص Ti ,Nb و P < /span> در گدازه­های منطقه، از نشانه­های سنگ­های وابسته به محیط فرورانش است. ترکیب شیمیایی این سنگ­ها و مجموعه­ی درشت بلورها، نشان دهنده­ی آن است که ماگماهای مادر آن­ها ترکیب بازی­تری داشته و احتمالاً خاستگاه گوشته­ای دارند و در یک محیط قوس آتشفشانی قاره­ای فوران کرده­اند. ماگماهای مورد نظر بخشی از تاریخ تبلور خود را در مخازن پوسته­ای پشت سر گذاشته و ضمن تبلور بخشی در این شرایط، دستخوش آلودگی پوسته­ای نیز شده­اند.

کلیدواژه‌ها


عنوان مقاله [English]

Petrography, geochemistry and tectonic setting of volcanic rocks in Zandiyeh- Raviz (northwest of Rafsanjan)

چکیده [English]

The studied area is located about 35 KM north-west of Rafsanjan (Kerman Province) and belongs to Hezar volcanic complex (in Uromieh-Dokhtar volcanic belt) and consists of Eocene folded lava flows (basalt, basaltic andesite, andesite) and pyroclastic rocks. Plagioclase phenocrysts show evidences of disequilibrium textures such as sieve texture, resorption and oscillatory zoning. These features can be formed by magma mingling, P < sub>H2O variations and decompression, as magma rises to the surface. Geochemical Studies indicate that lava flows belong to calc-alkaline magmatic series and their parent magmas have not extensively fractionated. The highly enrichment of LREE compared to HREE, high contents of LILE to HFSE and significant anomalies of Nb, Ti and P suggest a subduction-related volcanism. Chemical composition and phenocryst assemblages of these rocks indicate that these magmas probably derived from mantle, and then, have been erupted in a form of continental volcanic and they have passed some stages of their crystallization´s history in the crustal reservoirs During these stages, crustal contamination affected them.

کلیدواژه‌ها [English]

  • Urumieh-Dokhtar magmatic belt
  • magma mixing
  • calc-alkaline
  • crustal contamination
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