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1、Lithos67(2003)191–204www.elsevier.com/locate/lithosHighlyfractionatedI-typegranitesinNEChina(II):isotopicgeochemistryandimplicationsforcrustalgrowthinthePhanerozoicFu-yuanWua,b,Bor-mingJahnb,*,SimonA.Wildec,Ching-HuaLod,eaaaTzen-FuYui,QiangLin,Wen-chunGe,De-youSunaDepartmentofGeology,JilinU
2、niversity,79Jianshejie,130061Changchun,ChinabGe´osciencesRennes(CNRS),Universite´deRennesI,AvenueduGe´neralLeclerc,35042Rennescedex,FrancecDepartmentofAppliedGeology,CurtinUniversityofTechnology,Perth,WesternAustralia6845,AustraliadDepartmentofGeology,NationalTaiwanUniversity,245ChoushanRoa
3、d,Taipei,10770,Taiwan,ROCeInstituteofEarthSciences,AcademiaSinica,P.B.Box1-55,Nankang,Taipei115,Taiwan,ROCReceived13December2001;accepted22January2003AbstractNEChinaistheeasternmostpartoftheCentralAsianOrogenicBelt(CAOB).TheareaisdistinguishedbywidespreadoccurrenceofPhanerozoicgraniticrocks
4、.Inthecompanionpaper(PartI),weestablishedtheJurassicages(184–137Ma)forthreegraniticplutons:Xinhuatun,LamashanandYiershi.WealsousedgeochemicaldatatoarguethattheserocksarehighlyfractionatedI-typegranites.Inthispaper,wepresentSr–Nd–Oisotopedataofthethreeplutonsand32additionalsamplestodelineate
5、thenatureoftheirsource,todeterminetheproportionofmantletocrustalcomponentsinthegenerationofthevoluminousgranitoidsandtodiscusscrustalgrowthinthePhanerozoic.Despitetheirdifferenceinemplacementage,Sr–NdisotopicanalysesrevealthattheseJurassicgraniteshavecommon8786isotopiccharacteristics.Theyal
6、lhavelowinitialSr/Srratios(0.7045F0.0015),positiveeNd(T)values(+1.3to+2.8),andyoungSm–Ndmodelages(720–840Ma).Thesecharacteristicsareindicativeofjuvenilenatureforthesegranites.OtherLatePaleozoictoMesozoicgranitesinthisregionalsoshowthesamefeatures.Sr–Ndandoxygenisotopicdatasuggestthatthemagm
7、aticevolutionofthegranitescanbeexplainedintermsoftwo-stageprocesses:(1)formationofparentalmagmasbymeltingofarelativelyjuvenilecrust,whichisprobablyamixedlithologyformedbypre-existinglowercrustintrudedorunderplatedbymantle-derivedbasalticmagma,and(2)exten
