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1、Sr-Pb同位素地球化学特征1000-0569/2006/022(05)一1215-24ActaPetrologicaSinica岩石博格达裂谷双峰式火山岩地质年代学与Nd-Sr-Pb同位素地球化学特征王银喜顾连兴张遵忠吴昌志张开均李惠民杨杰东WANGYinXi,GULianXing2,ZHANGZunZhong2,WUChangZ~,ZHANGKaiJun,LIHuiMin'andYANGJieDong'1.南京大学现代分析中心,南京2100932.成矿作用国家重点实验室(南京大学),南京2100933.南京大学地球
2、科学系,南京2100934.中国科学院广州地球化学研究所,广州5106401.CenterofModemAnalysis,NanjingUniversity,Nanjing210093,China2.StateKeyLaboratoryofMineralDepositResearch,NanjingUniversity,Nanjing210093,China3.DepartmentofEarthScience,NanjingUniversity,Nanjing210093,China4.GuangzhouInstitu
3、teofGeochemistry,LaboratoryofMa~inalSeaGeology,ChineseAcademyofSciences,Guangzhou510640,China2005—12-20收稿.2006-03-22改回.WangYX,GuLX,ZhangZZ,WuCZ,ZhangKJ,LiHMandYangJD.2O06.GeochronologyandNd-Sr-PbisotopsofthebimodalvolcanicrocksoftheBogdarift.ActaPeWo~gicaSinica,
4、22(5):1215—1224AbstractTheBogdaorogen.whichislocatedbetweentlleJunggarandTurpan.HamiPrecambrianblocks.hasbeenprovedtobeaLatePalaeozoiccontinentalriftbymanylinesofgeologicalandgeochemicalevidence.SiO,contentofLowerCarboniferousvolcanicrocksinthisorogenexhibitsaga
5、pbetween55%and64%.BimodalvolcanicsuiteoftlleCimeitouformationatQijiaojingiscomposedofbasaltandalessamountofrhyolite.TheRb—Srisochronagesoftllebasaltsandrhyoliteare342.04-3.2Ma和340.34-3.4Ma,respectively.Theserockswereformedduringstrongextensionoftllerift.Theseage
6、sareconsistentwiththoseindicatedbyfossil.BasaltsoftheQijiaojingformationarecharacterizedby8Nd(t)=+6.4～+6.7,(盯Sr/86Sr);=0.703261～0.703328,(206Pb/2o4Pb);=17.70317.989.(Pb/埘Pb);=15.40715.498and(Pb/拟Pb);=37.14737.825,whilerhyolitesofthisformationarecharacterizedby8N
7、d(t)=+6.4～+6.6,(87Sr/86Sr)i=0.703368～0.703469,(06Pb/2o4Pb);=17.827～18.114,(2o7Pb/04Pb)i=15.46015.517and(Pb/Pb):=37.077—37.973.ThesedataindicatetllattherhyolitesissimilarinNd.Sr-Pbisotopestobasaltsandtllatthebasaltswerederivedfromadepletedmantle.whiletlleassociat
8、edrhyoliteswereformedbyfractionalcrystallizationofthebasalticmagma.Itisacommonideathatfractionalcrystallisationcanonlyproduceacontinuouslydifferentiatedrockseries.How
