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1、2009年12月矿床地质第28卷第6期December,2009MINERALDEPOSITS28(6):785~792文章编号:02587106(2009)0607858藏西班公湖斑岩铜矿带成矿斑岩地球化学及Pb、Sr、Nd同位素特征111212辛洪波,曲晓明,王瑞江,刘鸿飞,赵元艺,黄玮(1中国地质科学院矿产资源研究所,北京100037;2西藏自治区地质调查院,西藏拉萨850000)摘要对班公湖铜矿带2个具有代表性的斑岩铜矿床多不杂铜矿床和尕尔穷铜矿床进行了详细的岩石地球化
2、学和Pb、Sr、Nd同位素特征研究表明,与冈底斯铜矿带相比,该铜矿带含矿斑岩大离子不相容元素的富集程度相对减弱,而高场强元素和重稀土元素的亏损程度明显减轻,轻、重稀土元素的分馏程度减弱,且具有Eu的弱正143异常,岩石在氧化性上更强一些;从Pb、Sr、Nd同位素特征来看,班公湖铜矿带含矿斑岩更富含放射性成因铅,Nd/144Nd比值明显降低,其源区更接近印度洋沉积物区域,表明该铜矿带含矿斑岩的岩浆源区更浅,有更多的地壳物质加入;班公湖铜矿带含矿斑岩形成的构造环境属于活动大陆边缘区域,而冈底斯铜矿带明显偏离了活动大陆
3、边缘区域,表明班公湖斑岩铜矿带形成于碰撞后地壳隆升阶段,而冈底斯铜矿带则形成于碰撞后地壳伸展阶段。关键词地球化学;构造环境;Pb、Sr、Nd同位素;班公湖铜矿带中图分类号:P618.41文献标志码:AGeochemistryandPb,Sr,NdisotopicfeaturesoforebearingporphyriesinBangongLakeporphyrycopperbelt,westernTibet111212XINHongBo,QUXiaoMing,WANGRuiJiang,LIUH
4、ongFei,ZHAOYuanYiandHUANGWei(1InstituteofMineralResources,ChineseAcademyofGeologicalSciences,Beijing100037,China;2TibetInstituteofGeologicalSurvey,Lhasa850000,Tibet,China)AbstractDetailedgeochemicalandPb,Sr,NdisotopicresearchesontheDuobuzacopperdepositandtheG
5、arqiongcopperdepositwereconductedintheBangongLakecopperbelt.Theresultshowsthat,comparedwiththeporphyriesoftheGandesecopperbelt,theorebearingporphyriesoftheBangongLakecopperbeltareweakerintheenrichmentoflargeionlithophileelements(LILE)andarealsoweakerinthede
6、pletionofhighfieldstrengthelementsandhighrareelements,thushavingweakpositiveEuanomaly.ViewedfromPb,Sr,Ndisotopicfeatures,theorebearingporphyriesarecharacterizedbytheenrichmentofradiogenicPb,theobviouslylowratios143144ofNd/Nd,andthesourcenearertotheIndianO
7、ceansedimentaryarea,indicatingthatthemagmasourceoftheorebearingporphyriesismuchshallower,withthemixtureofmorecrustalmaterials.TheformingtectonicenvironmentoftheorebearingporphyriesintheBangongLakecopperbeltbelongedtotheactivecontinentalridge,whereasthatin
8、theGangdesecopperbeltwasfarawayfromtheactivecontinentalridge.TheBangongLakeporphyrycopperbeltwasformedinapostcollisionalcrustalupliftstage,whereastheGangdiseporphyry本文得到十一五!国家科技支撑计划项目(
