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  

Trace element and rare earth element geochemistry of the scheelite and ore genesis of the Yangjingou large scheelite deposit in Yanbian area,northeastern China.

作　　者：任云生[1] 赵华雷[1] 雷恩 王辉[1] 鞠楠[1] 吴昌志[3] 

机构地区：[1]吉林大学地球科学学院,长春130061 [2]重庆地质矿产研究院,重庆400042 [3]南京大学内生金属矿床成矿机制研究国家重点实验室,南京210093

出　　处：《岩石学报》2010年第12期3720-3726,共7页Acta Petrologica Sinica

基　　金：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);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

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Mo、B i、Sn、Nb、Ta等,具有很低的Rb/Sr、Nb/Ta和Zr/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(δEu 2.21~4.43),基本未见Ce元素异常(δCe为0.92~1.08),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CO2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N2,最终形成富含W等成矿物质的NaC l-H2O-CO2-N2流体体系。随着构造减压作用,CO2不断逸出,破坏了矿液内物理化学体系的平衡,导致WO42-与Ca2+在适当物理化学条件下形成白钨矿。In order to trace the ore-forming material of Yangjingou large scheelite deposit,trace elements and rare earth elements(REE) compositions of the scheelite mineral were determined by ICP-AES.The results show that the scheelite is depleted with Mo,Bi,Sn,Nb and Ta,and with very low ratios of Rb/Sr,Nb/Ta and Zr/Hf,indicating that primitive ore-forming materials of the Yangjingou deposit mainly came from the crust instead of the deep magmatic crystallization and differentiation.The scheelites picked from different samples possess very similar REE composition,obviously positive Eu anomalies(δEu 2.21~4.43) and little Ce anomalies(δCe 0.92~1.08),suggesting that intensive REE differentiation occurred between the scheelites and the ore-forming fluid.Moreover,both the scheelite and wall-rocks of the Wudaogou Group have similar dextral-inclined chondrite-normalied patterns,indicating low-grade metamorphic rocks of the Wudaogou Group supplied major ore-forming material.The conclusion may be drawn in this paper that the primitive ore-forming fluid derived predominantly from the upper mantle,and rich in CO2.The wall rock alteration resulted in decomposing of potassic minerals(i.e.biotite) and forming of N2.The NaCl-H2O-CO2-N2 fluid system rich in such ore-forming matarial as tungsten,with the ascending of the fluid,decompressed rapidly and caused the escaping of CO2 from the fluid.The breaking of physical-chemical balance of mineralizing fluid gave birth to the scheelite in Yangjingou deposit.

关 键 词：白钨矿 微量元素 稀土元素 成矿物质 杨金沟钨矿 

分 类 号：P618.67[天文地球—矿床学]