内蒙古乌努格吐山铜钼矿床Cu、Mo同位素组成及绢云母Ar-Ar测年对区域成矿作用的启示  

Compositions of Cu and Mo isotopes,sericite Ar-Ar ages of Wunugtushan Cu-Mo deposit in Inner Mongolia:Implications for regional mineralization

作　　者：宓奎峰 吕志成[1,2] 柳振江 颜廷杰[1,2] MI KuiFeng;LüZhiCheng;LIU ZhenJiang;YAN TingJie(Development and Research Center,China Geological Survey,Beijing 100037,China;Technical Guidance Center for Mineral Resources Exploration,Ministry of Natural Resources,Beijing 100083,China;School of Earth Sciences and Resources,China University of Geosciences,Beijing 100083,China)

机构地区：[1]中国地质调查局发展研究中心,北京100037 [2]自然资源部矿产勘查技术指导中心,北京100083 [3]中国地质大学(北京)地球科学与资源学院,北京100083

出　　处：《岩石学报》2021年第6期1785-1798,共14页Acta Petrologica Sinica

基　　金：国家重点研发计划项目(2018YFC0603806);国家自然科学基金项目(41802115、41702098)联合资助。

摘　　要：内蒙古乌努(奴)格吐山铜铅锌矿整装勘查区位于得尔布干成矿带西南段,是我国北方重要的Cu-Mo-Fe-Au-AgPb-Zn成矿带。近年来随着多接收电感耦合等离子体质谱(MC-ICP-MS)的广泛应用,使Mo、Cu、Fe、Zn等同位素的研究应用于矿床学研究中。本文通过对乌努格吐山斑岩型矿床黄铜矿Cu同位素、辉钼矿Mo同位素组成,绢云母Ar-Ar年龄进行研究,借此探讨该矿床的形成时代、矿床成因。结果显示,矿床成矿早阶段的绢云母坪年龄为181.9±1.1Ma,等时线年龄为181.0±2.3Ma,与辉钼矿Re-Os等时线年龄相一致。而石英+钾长石+辉钼矿+黄铜矿+黄铁矿脉中和石英+黄铜矿+黄铁矿脉中黄铜矿的δ65 Cu平均值分别为0.31y‰和0.40‰,显示黄铜矿的δ65 Cu值从早到晚逐渐增高,这可能为流体出溶过程中63 Cu优先进入富气相流体,残余岩浆流体逐渐富集65 Cu的结果。辉钼矿的δ98 Mo/δ95 Mo介于-0.16‰~0.35‰之间,说明在成矿作用的过程中Mo进入不同的矿物组合中并发生了同位素分馏,可能受到了氧化还原条件、温度等物理化学条件的变化,或者是辉钼矿的多型特征的影响。得尔布干成矿带矿床的形成与蒙古鄂霍次克洋的演化密切相关,结合前人研究成果,将成矿带斑岩型矿床分为240~230Ma、180~200Ma、150~160Ma三期。The Wunugetushan Cu-Pb-Zn exploration area,located in the southwest of the De’rbagan metallogenic belt,is an important Cu-Mo-Fe-Au-Ag-Pb-Zn ore concentration area in North China.In recent years,with the widespread application of multireceive inductively coupled plasma mass spectrometry(MC-ICP-MS),the studies of Mo,Cu,Fe,Zn and other isotopes have been applied to the ore deposits to reveal its mineral resources and genesis.In this study,we conducted the Cu isotopic composition of chalcopyrite,Mo isotopic composition of molybdenite,and the Ar-Ar age of sericite in the Wunugetushan porphyry deposit.We obtained a plateau age of 181.9±1.1 Ma and an isochron age of 181.0±2.3 Ma for the sericite at its early-stage mineralization,which is consistent with the molybdenite Re-Os isochron age.Theδ65 Cu of chalcopyrite from quartz+potash-feldspar+molybdenite+chalcopyrite+pyrite and quartz+chalcopyrite+pyrite veins are 0.31‰and 0.40‰,respectively,showing a gradually increases from early stage to later stage as a result of the enrichment of the 65 Cu in the residual magma since the 63 Cu preferentially enters the gas-rich fluid during the process of fluid exsolution,while the residual magma gradually enriched in 65Cu.Theδ98Mo/δ95 Mo ranges from-0.16‰to 0.35‰,indicating that the Mo entered different mineral phases and the isotopic fractionation occurred during the process of mineralization,which may be affected by the change of redox conditions,temperature and other physical and chemical conditions,or the types of molybdenite.Tectonically,the Mongol-Okhotsk ocean opened during Silurian,it subducted under the Siberia plate and China-Mongol continent from Triassic to Middle Jurassic,and finally closed at the time period from Later Jurassic to Early Cretaceous to form the Mongol-Okhotsk belt when the porphyry Cu-Mo deposits occurred at the north of Mongol-Okhotsk Ocean.The Cu-Mo mineralizations in this belt can be divided into three periods,namely:Middle-Late Triassic(240~230 Ma),Early Jurassic(200~180 Ma),Later Jura

关 键 词：Cu同位素 MO同位素 绢云母Ar-Ar测年 乌努格吐山铜钼矿床 得尔布干成矿带 蒙古-鄂霍次克洋 

分 类 号：P597.2[天文地球—地球化学] P618.41[天文地球—地质学]