بررسی رشد بلورهای مونازیت و تامین عناصر خاکی نادر از کانی آپاتیت: مطالعه موردی در کانسار آهن-آپاتیت اسفوردی (شمال شرق بافق)

نوع مقاله : مقاله پژوهشی

نویسندگان

1 سازمان زمین‌شناسی و اکتشافات معدنی کشور

2 دانشگاه بوعلی سینا همدان

چکیده

کانسار اسفوردی واقع در شمال شرق بافق و از مهمترین کانسارهای مگنتیت-آپاتیت در منطقه بوده که دارای کانه‌های عناصر خاکی نادر (REE Minerals) است. در این میان، کانی آپاتیت از نظر دارا بودن بودجه عنصری (بویژهREE )، پایداری در شرایط مختلف دما و فشار و تبادل­های یونی در شرایط محیطی جدید، اهمیت دارد. همه این ویژگی‌ها باعث شده است تا کانی آپاتیت در طی دگرسانی گرمابی، رفتار ویژه‌ای در هستک‌زایی کانی مونازیت داشته باشد. بر پایه بررسی­های سنگ نگاری و زمین­شیمیایی، چهار نسل آپاتیت در این کانسار شناسایی شده که در هر نسل، مقدار عنصری با کاهش مقادیر عناصر خاکی نادر کل (∑REE) و افزایش عناصری چون Ca و P < /span> همراه است. در مقابل، افزایش مقدار REE، Na، F و تاحدی Cl درون سیال گرمابی سبب هستک‌زایی و رخداد دو نسل مونازیت شده است. بر اساس تصاویر الکترونی پس پراکنده (BSE)، مناطق تهی‌شده از عناصر Na، Si و REE در آپاتیت منطبق بر کانال‌های میکرونی، منافذ و ریزشکستگی‌هایی بوده که ادخال‌های مونازیت در آن شکل گرفته‌ است. تشکیل مونازیت نسل اول و انحلال بعدی آن سبب تشکیل مونازیت‌های بین بلوری نسل دوم شده است.     

کلیدواژه‌ها

عنوان مقاله [English]

Apatite as a main source of REE during crystallization of monazite mineral in Esfordi Fe-Apatite deposit, northeast of Bafq

نویسندگان [English]

  • Iranmanesh 1
  • Tale Fazel 2
  • Hezareh 1
  • Majidy 1
1 Geological Survey of Iran
2 Bu-Ali Sina University
چکیده [English]

The Esfordi deposit is located at northeastern Bafq and is one of the well-known magnetite-apatite deposits in the area which consists of ore minerals hosted REE. Among the various ore minerals, apatite is one of the unique minerals because of its significant properties such as providing a budget of elements (especially in the case of REE), stability over widespread temperature and pressure domains and exclusively ionic interchanges as a respond to re-equilibrium with new environment. All of which can fit the apatite as a main source feeding the new mineral nucleation like monazite during a hydrothermal alteration. Based on petrography and geochemistry studies, mineralization of four generation apatite accompanied with dropping of REE amount in each stages and increasing of residual Ca and P in the next generations. In contrast, culminating amount of REE beside Na, F and limited Cl reached in nucleolus monazite and led to the formation of two generation of monazites. On the BSE images of apatite, the depleted areas are associated with micro-channels and micro-pores containing monazite. Consequently dissolution of nucleolus monazites provides a well chance to form the second generation of monazite as bigger grain than the first ones. 

کلیدواژه‌ها [English]

  • apatite
  • monazite
  • rare earth elements
  • Esfordi Fe-Apatite deposit
  • hydrothermal alteration

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  • تاریخ دریافت: 02 آبان 1397
  • تاریخ بازنگری: 07 دی 1397
  • تاریخ پذیرش: 07 بهمن 1397

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