华北克拉通南缘大庄铌-稀土矿床地质、地球化学和Sr、Nd、Pb同位素特征  

Geological,geochemistry and Sr,Nd,Pb isotopic characteristics of the Dazhuang Nb-REE deposit in southern margin of the North China craton

作　　者：李志丹[1,2,3] 李山坡 曾威[2,3] 李效广[2,3] 潘小娜 张哨波[4] 郭虎 刘文刚 LI Zhidan;LI Shanpo;ZENG Wei;LI Xiaoguang;PAN Xiaona;ZHANG Shaobo;GUO Hu;LIU Wengang(School of Earth Sciences and Resources,China University of Geosciences,Beijing 100083,China;Tianjin Center,China Geological Survey,Tianjin 300170,China;North China Center of Geoscience Innovation,Tianjin 300170,China;Henan Geological Survey Institute,Zhengzhou,Henan 450001,China;Henan Provincial Institute of Natural Resource Sciences,Zhengzhou,Henan 450016,China)

机构地区：[1]中国地质大学(北京)地球科学与资源学院,北京100083 [2]中国地质调查局天津地质调查中心,天津300170 [3]华北地质科技创新中心,天津300170 [4]河南省地质调查院,河南郑州450001 [5]河南省自然资源科学研究院,河南郑州450016

出　　处：《地质学报》2023年第1期82-108,共27页Acta Geologica Sinica

基　　金：河南省自然资源科研项目(编号豫财招标采购-2020-165-3);中国地质调查局项目(编号DD20211191,DD20200148,DD20160129,DD20190119);国家自然科学基金项目(编号41502082)联合资助的成果。

摘　　要：碱性岩型铌-稀土矿床是重要的铌-稀土矿资源类型。河南省方城县大庄铌-稀土矿位于华北克拉通南缘,是近年来新发现的一例赋存于霞石正长岩中的,具有中型规模的碱性岩型矿床。大庄矿区内共圈定17个NW—SE向带状展布的,呈囊状、不规则状、透镜状产出的铌-稀土矿体。铌-稀土矿石主要赋存于角闪霞石正长岩和黑云母正长岩中。矿石矿物主要为烧绿石、氟碳铈镧矿、褐钇铌矿和富铌榍石等。矿石的结构主要有斑状结构、他形粒状结构、半自形粒状结构、包含结构、交代结构、共生结构、伟晶结构等。矿石构造分为块状、脉状和片麻状构造等。热液蚀变包括萤石化、绢云母化、绿帘石化和绿泥石化等。碱性岩样品具有低SiO2、富碱、高铝的特征,稀土元素总量较高,轻重稀土分异明显,具有明显的负Eu异常,富集Nb、Ta、Th、U、Zr、Hf等高场强元素,明显亏损Ba、Sr、P、Ti等元素。碱性岩全岩(87Sr/86Sr)i=0.68158~0.71090,εNd(t)=―1.11~―0.37,两阶段模式年龄(tDM2)为1601~1540 Ma,(206Pb/204Pb)i=16.018~17.502、(207Pb/204Pb)i=15.358~15.489、(208Pb/204Pb)i=36.684~40.340。地球化学特征显示方城地区碱性岩的岩石类型为A型岩套A1亚型,岩浆演化主要受分离结晶控制,其原始岩浆形成于富金云母的地幔源区。总体上看,华北克拉通南缘大庄铌-稀土矿成矿主体受岩浆结晶分异控制,Nb、REE在岩浆结晶晚期大量富集,后期热液活动对铌-稀土成矿有一定的制约作用。方城地区碱性岩形成于板内拉张的构造背景,推测是Rodinia超大陆裂解的响应。Alkaline rock type Nb-REE deposit is an important type of Nb-REE mineral resources.The Dazhuang is a newly discovered medium-scale alkaline rock type Nb-REE deposit,which hosted in nepheline syenite on the southern margin of the North China craton,Fangcheng County,Henan Province.A total of 17 NW—SE trending Nb-REE orebodies with cystic,irregular and lenticular shapes are distributed in the Dazhuang deposit.The Nb-REE ores mainly occurs in hornblende nepheline syenite and biotite syenite.The ore minerals are mainly pyrochlore,bastn?site-(Ce,La),fergusonite and niobium-rich titanite.The texture of ores mainly includes porphyritic structure,heteromorphic granular structure,semi-automorphic granular structure,inclusion structure,metasomatic structure,symbiotic structure,pegmatite structure,etc.Ore structure is divided into massive structure,vein structure,gneiss structure and so on.Hydrothermal alteration includes fluorite,sericitization,epidote and chlorite.Alkaline rock samples have the characteristics of low SiO2,rich alkali,and high aluminum.The total amount of rare earth elements is high,the light and heavy rare earths are fractionated obviously,and they have obvious negativeδEu anomalies.They are enriched in high field strength elements such as Th,U,Zr,and Hf,obvious depleted in Ba,Sr,P and Ti.The Sr,Nd,and Pb isotopes of the whole alkaline rock are calculated as(87Sr/86Sr)i=0.68158~0.71090,εNd(t)=-1.11~-0.37,the two-stage model age(tDM2)is 1601~1540 Ma,(206Pb/204Pb)i=16.018~17.502,(207Pb/204Pb)i=15.358~15.489,(208Pb/204Pb)i=36.684~40.340.The geochemical characteristics show that the alkaline rock in the Fangcheng area belongs to the A1 subtype of the A-type rock suite.The magma evolution is mainly controlled by fractional crystallization.The original magma was derived from mantle where rich in phlogopite.Alkaline rocks in the Fangcheng area were formed under the tectonic setting of intraplate tension,which was a response to the breakup of the Rodinia supercontinent.On the whole,the main ore of the Dazhuang

关 键 词：岩石地球化学 矿床地质 Sr、Nd、Pb同位素 大庄铌-稀土矿 华北克拉通南缘 

分 类 号：P618.7[天文地球—矿床学]