文摘
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华北克拉通北缘的白云鄂博Fe-REE-Nb建造矿床是世界上已知的最大的稀土矿床,其矿床类型特殊,具有十分重要的意义,长期以来都备受国内外矿床地质学家的关注。由于其成矿作用的独特性和复杂性,国内外地质学界对此争议颇大,一直没有定论。国内外地质学家提出了多种成矿模式,但至目前为止,没有一种模型能够成功地解释区内缤纷复杂的地质现象,致使很多有关矿床成因关键性问题争论依旧。研究该矿床成因的意义不仅是解释矿床的形成条件,而且对于正确认识华北陆块北缘与西伯利亚板块碰撞条件下的壳幔相互作用以及寻找超大型矿床均有重要意义。结合我们多年的科研积累,特别是针对已获得大量岩石化学、稳定和放射成因同位素数据及相关研究成果,系统梳理及综述了白云鄂博超大型矿床的基底性质、火成碳酸岩、岩石地层及矿床形成时代,在此基础上,提出了白云鄂博矿床多阶段成矿模式。我们认为白云鄂博赋矿白云岩是沉积碳酸盐受地幔碳酸岩浆及派生的流体交代的产物,碳酸岩浆及其派生的富稀土流体与在地壳深部对沉积碳酸盐产生强烈交代,导致稀土元素在H8白云岩及其他地层的第一次富集。后来经加里东时期的板块聚合过程中的流体改造,使得稀土元素二次运移富集,形成了白云鄂博独特的Fe-REE-Nb矿床及区域性的大规模稀土矿化。至于铁矿的形成,我们认为它是在基底之上发育的一套BIF,经过中元古的碳酸岩侵入作用的改造,之后在加里东时期的板块聚合过程的再次聚集。 |
其他语种文摘
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The Bayan Obo ore deposit is the largest REE deposit,and the second largest Nb deposit in the world.It is also a large iron deposit.Therefore,the Bayan Obo ore deposit has been intensively studied on mineralogy,geochronology and ore-forming processes.Since the deposit was discovered,many researchers have studied it and made some achievements.Due to the complicated element and mineral compositions and activities of several geological events,the ore-forming mechanism is still controversial.The study of this super-large deposit formation is not only significant to the explanation of the ore-forming condition,but also for the correct understanding of regional geological evolution in the northern margin of north China Craton,leading to the knowledge of crust-mantle interaction under the condition of regional mineralization and geochemical dynamics. In this study,combined with accumulation of scientific research of many years,especially those large number of petrochemistry,stable and radiogenic isotopic data and research results,we systematically summarize the geological features of this super-large deposit,focusing on the formation of carbonatite rocks,dolomite and geochronological argues of rocks and deposits in the Bayan Obo region.We established multi-stage mineralization model of the Bayan Obo Fe-REE-Nb deposit. The paper shows that the marble in Bayan Obo deposit is the results of metasomatism of mantle fluids to sedimentary carbonates,Consequently,agenesis of the dolostone in Bayan Obo is:it was a mixture of sedimentary dolomite with carbonatite in the depth of crust,where carbonatite magma was mixed melting products of mantle REE rich fluids and sedimentary carbonate rocks in crust,leading REE enrichments in H8 dolomite and other sedimentary units.Moreover,the Fe-REE-Nb ore deposits had been formed during/after the strong hydrothermal alteration by the carbonatite magmatic events. We suggest that the ore-bearing H8 dolomite of Bayan Obo Fe-REE-Nb deposit is original sedimentary carbonate with metasomatic function caused by mantle-fluid derived from carbonatite magma,which is rich in rare earth elements in Meso-Proterozoic.This was the first period of REE mineralization.The second REE mineralization occurred in Caledonian period when Siberian plate subducted to the North China plate,during which secondary migration enrichment of rare earth elements caused the formation of this unique REE-Nb.As for the formation of iron ore,we suggest that it was first in form of BIF after Ar2-Pt1,after the carbonatite intrusion intruded along the Bayan Obo rift.Consequently,the BIF was re-formed with transformation,re-deposition by carbonatite intrusion and later plate subduction in Caledonian period. |
来源
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地质学报
,2015,89(12):2323-2350 【核心库】
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关键词
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白云岩
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碳酸岩岩浆
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Fe-REE-Nb矿化
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成因
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裂谷
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白云鄂博
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华北克拉通
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板块俯冲
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地址
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1.
中国科学技术大学地球和空间科学学院, 合肥, 230026
2.
东华理工大学地球科学学院, 南昌, 330013
3.
中国科学院广州地球化学研究所, 广州, 510640
4.
包钢(集团)公司白云鄂博铁矿, 内蒙古, 包头, 014080
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语种
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中文 |
文献类型
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研究性论文 |
ISSN
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0001-5717 |
学科
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地质学 |
基金
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广东省自然科学基金
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国家重点基础研究发展计划项目国家财政部公益性行业科研专项
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国家重点基础研究发展计划项目国家财政部公益性行业科研专项
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文献收藏号
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CSCD:5599060
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