白云鄂博矿床研究若干问题的探讨  

Addressing Some Problems on Research of the Bayan Obo Deposit

作　　者：王凯怡[1] 杨奎峰[1] 范宏瑞[1] 胡芳芳[1] 胡辅佑[1] 

机构地区：[1]中国科学院地质与地球物理研究所,北京100029

出　　处：《地质学报》2012年第5期687-699,共13页Acta Geologica Sinica

基　　金：国家自然科学基金项目(编号40625010和40902028)资助的成果

摘　　要：白云鄂博巨型稀土-铌-铁矿床是与火成碳酸岩(即H8)有关的矿床。在碳酸岩岩浆阶段,在其蚀变围岩(霓长岩)中以及晚期的热液阶段都有稀土、铌和铁等的富集。因此,白云鄂博矿床不是单一矿床类型,其涵盖了稀土-铌-铁碳酸岩岩浆型矿床、稀土-铌-铁交代蚀变岩型和热液型矿床,这种复合类型的矿床是十分罕见的,可称之为白云鄂博式矿床。根据已发表的年代数据,白云鄂博大规模碳酸岩的形成时代和伴随的稀土矿化的高峰期在1.3～1.4Ga。加里东构造热事件对本区的影响广泛和强烈,不仅有广泛发育的大型褶皱、冲断层和韧性剪切作用,并伴有广泛的流体交代作用和局部的热液活动,某些稀土矿物的同位素体系受到重置,表现为其Sm-Nd年龄和Th-Pb年龄的不一致。本区的碱性岩在基底杂岩中即有出露,随后在白云鄂博群中和1.3～1.4Ga白云鄂博碳酸岩形成时皆有产出。目前所获资料表明,至少1.3～1.4Ga的碱性杂岩在成因上与碳酸岩有密切的联系。本区基底杂岩显示了白云鄂博地区在2.0Ga左右曾经有一个弧地质体,该区在2.0～1.9Ga间经历了从被动大陆边缘到活动大陆边缘增生碰撞的一个完整的造山过程。The Bayan Obo giant REE-Nb-Fe deposit is the one genetically related to igneous carbonatic rock.Rare earths,niobium and iron were enriched from carbonatitic magma intrusion stage,altered country rock stage（fenite）,to late-stage hydrothermal stage.Therefore,the Bayan Obo deposit is not a unitary type of deposit,but a mixed deposit containing REE-Nb-Fe carbonatite-type mineralization,REE-Nb-Fe replacement alteration,and hydrothermal effect.The deposit of such kind is very rare,and thus can be called Bayan Obo-type deposit.Based on age data published,the formation time of larges-scale carbonatite of the Bayan Obo deposit and the peak period of associated rare earth mineralization are around 1.3 or 1.4 Ga.The Caledonian tectonic thermal event had wide and extensive effect on this area,resulting in the development of large folding,thrust faulting and ductile shear,and extensive fluid metasomatism and regional hydrothermal activities.Isotopic composition systems of some rare earth minerals were relocated,suggested by disagreement of Sm-Nd ages and Th-Pb ages.Alkaline rock is not only present at basement complex of this area but at subsequent 1.3 or 1.4 Ga carbonatite of Bayan Obo Group.Current data available at least shows a genetic relation between alkaline complex and carbonatite.The basement complex in this area indicates that there existed an arc mass at the Bayan Obo area at 2.0 Ga,and during the Paleoproterozoic time（2.0~1.9 Ga） the Bayan Obo area experienced a complete orogenic process from passive continental margin to accretion collision of active continental margin.

关 键 词：白云鄂博式矿床 成矿时代 碱性杂岩 基底杂岩 

分 类 号：P618.7[天文地球—矿床学]