内蒙古东珺银铅锌矿床成矿时代与地质背景:来自富碱花岗斑岩地球化学、锆石U-Pb及闪锌矿Rb-Sr年代学的制约  

Metallogenic Age and Geological Setting of the Dongjun Ag-Pb-Zn Deposit,Inner Mongolia:Constraints from Geochemistry,Zircon U-Pb and Sphalerite Rb-Sr Chronology of the Alkali-rich Granite Porphyry

作　　者：宋天骄 王策 梁细荣[1,2] 梁新权[1,2] SONG Tianjiao;WANG Ce;LIANG Xirong;LIANG Xinquan(State key Laboratory of Isotope Geochemistry,Guangzhou Institute of Geochemistry,Chinese Academy of Sciences,Guangzhou 510640,Guangdong,China;Center for Excellence in Deep Earth Science,Chinese Academy of Sciences,Guangzhou 510640,Guangdong,China;University of Chinese Academy of Sciences,Beijing 100049,China;School of Marine Sciences,Sun Yat-sen University,Zhuhai 519082,Guangdong,China)

机构地区：[1]中国科学院广州地球化学研究所,同位素地球化学国家重点实验室,广东广州510640 [2]中国科学院深地科学卓越创新中心,广东广州510640 [3]中国科学院大学,北京100049 [4]中山大学海洋科学学院,广东珠海519082

出　　处：《大地构造与成矿学》2024年第5期1040-1059,共20页Geotectonica et Metallogenia

基　　金：国家自然科学基金项目(41702115,41576040)资助。

摘　　要：东珺银铅锌矿床位于大兴安岭中北部内蒙古额尔古纳市,是近几年发现的大型银铅锌多金属矿床。该矿床的成矿时代、成矿岩石以及构造背景一直不明确,本文对矿区内的出露的安山岩和隐伏的花岗斑岩开展了LA-ICPMS锆石U-Pb定年及岩石地球化学研究,并对银铅锌矿体中闪锌矿进行了Rb-Sr同位素定年。结果显示,安山岩喷出年龄为170.2±1.0 Ma、花岗斑岩结晶年龄为145.0±1.2 Ma以及矿体的成矿年龄为141.1±3.4 Ma。成矿年龄稍晚于花岗斑岩成岩年龄,表明成矿作用与晚侏罗世-早白垩世的岩浆活动具有密切的成因联系。花岗斑岩具有高硅(SiO_(2)=71.79%~72.88%)和富碱(Na_(2)O+K_(2)O=6.47%~8.23%)的特征,属于高钾钙碱性-钾玄岩系列。岩石的稀土元素总量较高(∑REE=195×10^(-6)~217×10^(-6)),具明显的Eu负异常(δEu=0.28~0.33),微量元素富集大离子亲石元素Rb、Th、U、K,明显亏损高场强元素Nb、Ta、Ti和过渡元素Sr、Ba,且具有高的10^(4)×Ga/Al(2.68~2.84)值,其全岩(^(87)Sr/^(86)Sr)i和ε_(Nd)(t)分别为0.704423~0.704768和+0.01~+1.94,锆石的ε_(Hf)(t)为+1.37~+8.29,表明该岩体具有A型花岗岩特征,其岩浆源区可能由地幔熔体和新生地壳熔体混合形成。结合区域地质和前人研究成果,认为东珺矿区花岗斑岩及相关的矿化作用形成于后碰撞伸展的构造环境,与晚侏罗世-早白垩世鄂霍茨克洋闭合后碰撞密切相关。The Dongjun Ag-Pb-Zn deposit,located in Erguna City,Inner Mongolia,the north-central section of the Great Hinggan Mountains,was discovered in recent years.The ore-forming age,the ore-forming rocks,and the tectonic setting of the Dongjun deposit are unclear.In this study,LA-ICPMS zircon U-Pb and sphalerite Rb-Sr isotopic dating,major and trace element concentrations,and Sr-Nd and zircon Hf isotopic compositions of the hidden granite porphyry and exposed andesite were analyzed.The results show that the eruption age of andesite is 170.2±1.0 Ma,the crystallization age of granite porphyry is 145.0±1.2 Ma,and the ore-forming age of the lead-zinc ore body is 141.1±3.4 Ma.Among them,the metallogenic age was slightly younger than that of the granite porphyry,indicating that the mineralization was closely related to the post-magmatic hydrothermal activity during the Late Jurassic-Early Cretaceous.The granite porphyry is characterized by high SiO_(2)(SiO_(2)=71.79%-72.88%)and alkali(Na_(2)O+K_(2)O=6.47%-8.23%),and belongs to the high-K calc-alkaline and shoshonite series.The granite porphyry has high total REE(ΣREE=195×10^(-6)-217×10^(-6))and is enriched in large-ion lithophile elements such as Rb,Th,U,and K,depleted in high field strength such as Ta,Nb,and Ti and transition elements such as Sr and Ba,with strong negative Eu anomalies(δEu=0.28-0.33)and high Ga/Al.The(87 Sr/86 Sr)i,ε_(Nd)(t),andε_(Hf)(t)ratios range from 0.704423 to 0.704768,+0.01 to+1.94,and+1.37 to+8.29,respectively.These characteristics indicate that the granite porphyry is A-type granite and originated from the mixing of mantle and juvenile crust melts.Based on the results of this study and the regional geodynamic evolution,we propose that the Dongjun granite porphyry and associated deposit formed in an extensional setting related to the closure of the Mongol-Okhotsk Ocean during the Late Jurassic-Early Cretaceous.

关 键 词：东珺银铅锌矿床 锆石年代学 闪锌矿Rb-Sr 地球化学 蒙古-鄂霍茨克洋 

分 类 号：P595[天文地球—地球化学] P597[天文地球—地质学]