تعیین منشأ پریدوتیت‌های میزبان کانسارهای کرومیت بر اساس داده‌های کانی‌شناسی در افیولیت نیریز، منطقه آباده‌طشک، استان فارس

نوع مقاله : مقاله پژوهشی

نویسندگان

1 استادیار بخش علوم زمین دانشگاه شیراز

2 دانشجوی کارشناسی ارشد زمین شناسی اقتصادی بخش علوم زمین دانشگاه شیراز

چکیده

    افیولیت نیریز در منطقه آبادهطشک عمدتاً از سنگهای اولترامافیک (لرزولیت ، هارزبورژیت و دونیت) باقیمانده از ذوببخی گوشت فوق العاده تشکیل شده است افزایش درجه ذوببشی برای ترتیب از سنگ لرزیت به سمت هارزبورژیت و سپس دونیت به استفاده از ترکیب مودال کانیشناسی این سنگها نشان می دهد. تغییر در مادال کانیشناسی سنگهای میزبان کانسارهای کرومیت با تغییر در ترکیب شیمیایی کانیهای اولیوین و اسپینل در سنگهای میزبان متناسب نیست. میزان Fo اولیوین از لرزولیت (79 / 90-5 / 91) به سمت هارزبورژیت (23 / 91-56 / 91) و دونیت (75 / 91-68 / 94) افزایش می یابد. این تغییر شیمیایی برای افزایش میزان Cr # (از 34/56 در لرزولیت به 36/79 در دونیت) و کاهش Mg # (از 05/41 در لرزولیت به 56/32 در دونیت) در اسپینلهای همان سنگها وجود دارد. مقادیر Cr # ، Mg # ، Al 2 O 3 و TiO 2 در ترکیب کانیهای اسپینل میکرومدار سنگهای پریدوتیتی نشانگر تشکیل مجموعه افیولیتی در یک حوضه پیشکمانی (Forearc) بر روی منطقه منطقه فرورانش (منطقه فوق فرورانش) وجود ندارد.

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