江南古陆西段木瓜园钨矿床成矿流体演化过程研究  

Geological and ore-forming fluids characteristics of the Muguayuan tungsten deposit in the western part of the Jiangnan massif

作　　者：李洪英[1] 杨磊 陈剑锋 陈文辉 李杰[5] LI HongYing;YANG Lei;CHEN JianFeng;CHEN WenHui;LI Jie(MNR Key Laboratory of Metallogeny and Mineral Assessment,Institute of Mineral Resources,CAGS,Bejing 100037,China;CNOOC International Ltd.,Bejing 100028,China;Hunan Institute of Geology Survey,Changsha 410116,China;No.418 Geological Brigade of Geology and Mineral Exploration Bureau in Hunan Province,Loudi 417000,China;PetroChina Research Institute of Petroleum Exploration and Derelopment,Bejing 100083,China)

机构地区：[1]中国地质科学院矿产资源研究所,自然资源部成矿作用与资源评价重点实验室,北京100037 [2]中国海洋石油国际有限公司,北京100028 [3]湖南省地质调查院,长沙410116 [4]湖南省地质矿产勘查开发局418队,娄底417000 [5]中国石油勘探开发研究院,北京100083

出　　处：《岩石学报》2021年第3期911-926,共16页Acta Petrologica Sinica

基　　金：国家自然科学基金项目(41602074、41430314);中国地质调查局项目(DD20190606);中央级公益性科研院所基本科研业务专项资金(YYWF201510)联合资助。

摘　　要：木瓜园白钨矿位于江南古陆钨矿带西段,矿体主要产于花岗闪长斑岩中,局部产于侵入围岩(岩性主要为粉砂质板岩、砂质板岩,局部绢云母板岩)的石英脉中,是揭示该区成矿规律的重要组成。本文利用显微测温和阴极发光图像技术对木瓜园钨矿床不同成矿阶段的流体包裹体及白钨矿原位微量元素特征进行了系统研究。结果显示:(1)钨矿床包裹体类型有富液相气液两相包裹体、含子晶包裹体和CO2包裹体,此外还有少量的富气相包裹体和液相包裹体;流体包裹体盐度范围为3.39%~12.18%Na Cleqv,均一温度范围为161~396℃,属于Na Cl-H_2O体系。(2)白钨矿微量元素研究显示以富集Mo、Nb、Sr、Ba为特征,白钨矿的铕异常(δEu)由早期的钾硅酸阶段(0.46)到晚期的硫化物阶段(2.98)逐渐由负异常到正异常,表明成矿流体氧逸度逐渐减弱。白钨矿的稀土元素配分模式与矿区的花岗闪长斑岩的稀土元素配分模式相似,白钨矿中正的Eu异常可能是短期相对还原条件造成的,推测形成木瓜园白钨矿的流体继承了母岩浆的稀土元素特征,白钨矿是在相对还原和微弱波动的氧化还原条件下沉淀。白钨矿Zr/Hf比值0.93~50.84,平均16.88,Y/Ho介于62.57~21.96,平均为33.34,变化幅动较大,指示成矿阶段存在不同程度的外来流体混合。白钨矿的Nb/Ta比值变化范围为1.75~42.72,平均为23.57,指示成矿物质可能来源为壳幔混合;白钨矿中LREE/HREE变化范围为0.12~11.37,具有斑岩型钨矿床的特征。The Muguayuan deposit has a total resource of more than 10,000 t WO3 deposit in the western part of the Jiangnan massif,ore bodies mainly occur in granodiorite porphyry,and locally exist in quartz veins of country rocks(mainly silty slate,sandy slate and sericite slate),which is an important component to reveal the metallogenic regularity of Jiangnan massif.The Muguayuan W deposit located in Taojiang County of Hunan Province is a newly discovered large W deposit in the western part of the Jiangnan massif,the deposit is hosted in the Sanxianba granite porphyry.The main ore-forming types in the deposit include disseminated,veinlet,and stockwork,and the major alteration types of wall rocks comprise potassic alteration,silicification,sericitization,pyritization,and carbonatation etc.,which constitute typical ore-forming and alteration characteristics of porphyry W deposits.Five main types of primary fluid inclusions are present in quartz,including two-phase aqueous,one-phase aqueous,multi-phase,CO2-dominated,twophase vapor-rich fluid inclusions.The homogenization temperatures of inclusions range from 161~396℃,estimated salinities of the ore-forming fluids range from 3.39%to 12.28%Na Cleqv.The ore-forming fluids are thus characterized by medium to high temperatures and moderate to low salinities H2 O-Na Cl fluids.Our research shows that the scheelite is characterized by rich in Mo,Nb,Sr,and Ba,the Eu negative anomaly of scheelite decreases gradually from the early stage of potassium-silicate stage to the late stage of sulfide stage(from 0.03 to 2.85,average 0.41).The chondrite-normalized REE patterns of the scheelite are corresponding to that of diorite porphyry,which might inherit from the parental magma.Scheelite is precipitated under relatively reducing and weakly fluctuating redox condition.The Zr/Hf ratio of scheelite ranges from 0.93 to 50.84,with an average of 16.88,and the Y/Ho ratio ranges from 62.57 to 21.96,with an average of 33.34,indicating that there were different degrees of exotic fluid mixing in the

关 键 词：成矿流体 白钨矿 原位微量元素分析 木瓜园钨矿床 江南古陆 

分 类 号：P618.67[天文地球—矿床学]