کانی‌شناسی و زمین‌شیمی عناصر خاکی نادر نهشته بوکسیت زرج‌سو، جنوب غرب رامسر، شمال ایران

نوع مقاله : مقاله پژوهشی

نویسندگان

1 دانشگاه ارومیه

2 دانشگاه تبریز

چکیده

نهشته بوکسیت زرج­سو (جنوب­غرب رامسر، استان مازندارن، شمال ایران) به صورت لایه­ها و یا عدسی­های گسسته چینه­سان در طول مرز بین سنگ­های کربناتی سازند الیکا (تریاس) و شیل­ها و ماسه­سنگ­های سازند شمشک (ژوراسیک پیشین) گسترش یافته است. دیاسپور، کائولینیت، هماتیت، آناتاز و روتیل فازهای کانیایی اصلی در این کانسنگ­ها هستند. از نظر بافتی، کانسنگ­های بوکسیتی شامل بافت­های آواری، دانه­مدور و برشی هستند که اغلب با بعضی شکل­های سخت­دانه­ای، اووئیدی و پیزوئیدی محدود همراه هستند. غلظت عناصر خاکی نادر (REE) در کانسنگ­ها در یک نیمرخ انتخابی از نهشته در گستره 10/348-97/149 گرم در تن و نسبت بی­هنجاری­های Eu/Eu*و Ce/Ce* به ترتیب در گستره­ 04/1-61/0 و 28/1-64/0 در تغییر هستند. بررسی­ها نشان دادند که تغییر مقادیر این پارامترها توسط درجه روبش هماتیت کنترل شده است. از محاسبه تغییرات جرم عناصر و بررسی روند تغییرات نسبت­های عنصری در یک نیمرخ انتخابی از این نهشته آشکار شد که توزیع REEها در کانسنگ­ها تابعی از عواملی چون تغییر pH محلول­های کانسنگ­ساز، حضور سنگ بستر کربناتی به عنوان یک بافر فعال، رسوبگذاری همزمان با اکسیدهای فلزی و تثبیت در فازهای کانیایی نوشکل است. ضرایب همبستگی بین عناصر پیشنهاد می­کنند که کانی­هایی مانند هماتیت و فسفات­های ثانویه میزبان­های احتمالی لانتانیدها در کانسنگ­های مورد بررسی هستند.    

کلیدواژه‌ها


عنوان مقاله [English]

Mineralogy and REEs geochemistry of the Zaraj-Sou bauxite deposit, southwest of Ramsar, north Iran

نویسندگان [English]

  • mahmoud Ghasemi 1
  • Ali Abedini 1
  • AliAsghar Calagari 2
1
2
چکیده [English]

The Zaraj-Sou bauxite deposit (southwest of Ramsar, Mazandaran Province, northern Iran) was developed as discontinuous stratified layers and/or lenses along the boundary between carbonate rocks of the Elika (Triassic) and shales and sandstones of the Shemshak (Lower Jurassic) formations. Diaspore, kaolinite, hematite, and anatase are the major mineral phases of the ores. Texturally, the bauxite ores have typical textures of clastic, rounded-grain, and nodular which are often accompanied by certain forms of concretions, ooids, and pisoids in restricted quantities. Concentration values of REEs within the ores in the selected profile vary from 149.97-348.10 ppm and the ratios of Eu/Eu* and Ce/Ce* are within the range of 0.75-1.04 and 0.64-1.28, respectively.  Investigations showed that changes in the values ​​of these parameters are controlled by degree of scavenging hematite. The calculation of mass changes of elements and the study of the trend of variation of elemental ratios in a selected profile across this deposit revealed that the distribution of REE in ores is a function of factors such as changes in pH of ore-making solutions, presence of carbonate bed rock as an active buffer, co-precipitation with metallic oxides, and fixation in neomorph mineral phases. Correlation coefficients among elements suggest that minerals such as hematite and secondary phosphates are the potential hosts for lanthanides in the studied ores.

کلیدواژه‌ها [English]

  • Bauxite
  • rare earth elements
  • host minerals
  • Zaraj-Sou
  • Iran
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