延边杨金沟大型钨矿床白钨矿的微量和稀土元素地球化学特征与矿床成因

延边杨金沟大型钨矿床白钨矿的微量和稀土元素地球化学特征与矿床成因

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任云生1

赵华雷1

雷恩2

王辉1

鞠楠1

吴昌志

3

REN Y unSheng 1

,Z HAO H uaL ei 1

,LE I En 2

,W ANG H ui 1

,J U N an 1

and WU ChangZh i

3

11吉林大学地球科学学院,长春 13006121重庆地质矿产研究院,重庆 400042

31南京大学内生金属矿床成矿机制研究国家重点实验室,南京 21009311C olle ge of E art h Sciences ,Jilin Universit y,C hang c hun 130061,Ch i na

21Ch ong qi ng In stit u t e of G eolo gy and M i n e ral R esources ,Ch ong qi ng 400042,Ch i na

31S tate K e y Labora tory for M inera lDe p osits R esearc h,N anjing Un i v e rsit y,N anji ng 210093,Ch ina 2010-10-01收稿,2010-11-11改回1

R en YS ,Zhao HL,L ei E,W ang H,Ju N and W u CZ 120101Trace e l em en t and rare earth elemen t geoche m istry of th e scheelite and ore genesis of the Yangji ngou l arge scheelite d eposit in Y anb i an area ,northeastern Ch i na 1Ac t a Petrolog ica S in ica ,26(12):3720-3726

Abstrac t In order to trace the ore -form i ng m ater i a l o f Y ang ji ngou large schee lite depos it ,trace e le m ents and rare eart h e l e m ents (REE)co m positions of t he scheelite m i neral w ere dete r m ined by ICP-AES 1T he results s how that the schee lite i s depleted w ith M o ,B,i Sn ,N b and T a ,and w it h very l ow rati os of R b /Sr ,N b /T a and Z r /H ,f ind i cati ng t hat pr i m itive ore -form i ng m ater i a ls o f the Y ang ji ngou depo sitm a i n l y cam e fro m t he crust i nstead of the deep m agma ti c crysta lli zati on and d ifferentiati on 1The schee lites picked fro m d ifferent sa m ples possess very si m ilar REE compositi on ,obv i ousl y positi v e Eu anom ali es (D Eu 2121~4143)and little C e ano m a lies (D C e 0192~1108),suggesti ng tha t i ntensive R EE differentiati on occurred bet ween the scheelites and t he ore -fo r m i ng fl u i d 1M o reover ,both the schee lite and w al-l ro cks o f the W udaogou G roup have si m ilar dextra -l i ncli ned chondr ite -nor m a lied patte rns ,ind i cati ng l ow-grade me ta m orphic rocks o f t he W udaogou G roup supplied m a j o r o re -for m i ng m ate rial 1T he conc l usi on m ay be dra w n in this paper that t he pri m iti ve o re -f o r m i ng fl u i d der i ved predom inantl y fro m t he upper m antl e ,and rich i n CO 21T he w a ll ro ck a ltera ti on resu lted i n decomposi ng o f potassic m i nera ls (i 1e 1biotite)and for m i ng of N 21T he N aC-lH 2O-CO 2-N 2fl u i d system r i ch i n such ore -for m i ng ma taria l as t ungsten ,w it h the ascendi ng o f the fluid ,deco m pressed rap i d l y and caused the escap i ng o f CO 2from the flui d 1T he break i ng of physica-l chem ica l balance o fm i neralizi ng fl u i d gav e b irt h to the schee lite in Y ang ji ngou depo sit 1

K ey word s Schee lite ;T race ele m ents ;R are eart h e le m engt (REE );O re -f o r m i ng m ater i a ;l Y ang ji ngou schee lite deposit 摘 要 为确定杨金沟大型钨矿的成矿物质来源,本文运用白钨矿单矿物的微量元素、稀土元素特征加以示踪。ICP-AES 测定结果显示:白钨矿亏损M o 、B i 、Sn 、N b 、T a 等,具有很低的R b /Sr 、N b /T a 和Z r /H f 值,指示其成矿物质具有壳源特征,而并非主要来自深源岩浆的结晶分异作用;不同白钨矿样品的REE 组成基本一致,Eu 元素出现明显的正Eu 异常(D Eu 2121~4143),基本未见Ce 元素异常(D Ce 为0192~1108),表明白钨矿与流体之间稀土元素发生了强烈分异;白钨矿与赋矿围岩的REE 球粒陨石标准化配分曲线形态相似,进一步显示五道沟群浅变质岩对杨金沟钨矿成矿物质的贡献。综合分析认为,杨金沟钨矿的成矿流体为源自上地幔的富含CO 2的中高温流体,沿构造上升并与五道沟群浅变质岩发生交代作用引起黑云母等含钾矿物分解产生N 2,最终形成富含W 等成矿物质的N aC-lH 2O-CO 2-N 2流体体系。随着构造减压作用,CO 2不断逸出,破坏了矿液内物理化学体系的平衡,导致W O 2-4

与Ca 2+在适当物理化学条件下形成白钨矿。1000-0569/2010/026(12)-3720-26A cta P etro log ica Sinica 岩石学报

*本文受中国地质调查局项目(资[2010]矿评01-20-06)、吉林大学科学前沿与交叉学科创新项目(421030414422)和南京大学内生金属矿床成矿机制研究国家重点实验室开放基金(14-08-11)联合资助.

第一作者简介:任云生,1969年生,博士,教授,主要从事矿床学的教学与研究工作,E-m ai:l renys @jl u