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1、第26卷第3期現(xiàn)代地質(zhì)Vol26No32012年6月GEOSCIENCEJun2012福建龍巖大洋花崗巖LAICPMS鋯石UPb測年、Hf同位素組成及其地質(zhì)意義1234張承帥,李莉,張長青,王九如(1中國地質(zhì)大學(xué)地球科學(xué)與資源學(xué)院,北京100083;2中國地質(zhì)圖書館,北京100083;3中國地質(zhì)科學(xué)院礦產(chǎn)資源研究所,北京100037;4內(nèi)蒙古第七地質(zhì)礦產(chǎn)勘查開發(fā)院,內(nèi)蒙古呼和浩特010020)摘要:對福建
2、龍巖大洋花崗巖的兩期巖相進(jìn)行了LAICPMS鋯石UPb定年和鋯石Hf同位素研究。結(jié)果表明:大洋花崗巖的早期黑云母正長花崗巖年齡為(1448±09)Ma,εHf(t)值為-558~-200,二階段Hf模式年齡為1313~1530Ma,晚期微斜長石花崗巖的年齡為(1275±04)Ma,εHf(t)值為-757~-090,二階段Hf模式年齡為1246~1668Ma。同位素特征表明,大洋花崗巖兩期巖體都形成于早白堊世,是在巖石圈伸展的底侵作用下形成的,物源主要是中元古代地殼物質(zhì),但晚期有少量幔源組分的
3、加入。關(guān)鍵詞:LAICPMS鋯石UPb測年;Hf同位素;大洋花崗巖;福建龍巖中圖分類號:P58813;P5971文獻(xiàn)標(biāo)志碼:A文章編號:1000-8527(2012)03-0433-12LAICPMSZirconUPbAgesandHfIsotopicCompositionsofDayangGranitefromLongyan,FujianProvince1234ZHANGChengshuai,LILi,ZHANGChangqing,WANGJiuru(1SchoolofEarthScien
4、cesandResources,ChinaUniversityofGeosciences,Beijing100083,China;2ChinaGeologicalLibrary,Beijing100083,China;3InstituteofMineralResources,ChineseAcademyofGeologicalSciences,Beijing100037,China;4No7ExplorationandDevelopmentInstituteofGeologyandMineralResour
5、cesofInnerMongolia,Hohhot,InnerMongolia010020,China)Abstract:AcomprehensiveresearchincludingLAICPMSzirconUPbdatingandHfisotopiccompositionanalysisonDayanggraniticplutonwascarriedout.WeobtainedtheLAICPMSzirconUPbagesof(1448±09)Maand(1275±04)Mafortheea
6、rlymediumcoarsegrainedbiotitegraniteandthelatemediumfinegrainedplagioclasegraniteinDayanggraniticpluton,respectively.AccordingtozirconHfisotopeanalyses,thebothεHf(t)valuesarefrom-558to-200andfrom-757to-090,andtheircorrespondingHftwostagemodelages(TDM2)are
7、from1,313to1,530Maandfrom1,246to1,668Ma,respectively.ThesedatasuggestthatthemagmasourcesofthetwostagesinDayanggranitemainlyderivedfromMesoproterozoiccrustalmaterials,butthesecondstageinvolvedsomeportionsofmantlecomponent.DayanggraniteformedintheEarlyCretaceous
8、,whichimpliesthatitgeneratedinbasalticunderplatingunderlithosphereextensionenvironment.Keywords:LAICPMSzirconUPbdating;Hfisotope;Dayanggranite;Longyan,Fujian中生代發(fā)生了大規(guī)模多期次的巖漿活動,是我