鋯石Hf同位素-吳元保教學(xué)課件

鋯石Hf同位素-吳元保鋯石Hf同位素-吳元保鋯石Hf同位素-吳元保LuHf同位素體系及鋯石Hf同位素研究表1L、Hf元套的同位素組成元素同位素豐度(%)IrHt35.100IthaslongbeenrecognizedthatLu-HfandSm-NdisotopesystemsbehaveanalogouslyduringmostmagmaticprocessesandthatthehfandNdisotopiccompositionsshouldbebroadlycorrelatedinmostcrustalandmantlerocks/LuHf同位素體系及鋯石Hf同位素研究表1L、Hf元套的同位素組成元素同位素豐度(%)IrHt35.100IthaslongbeenrecognizedthatLu-HfandSm-NdisotopesystemsbehaveanalogouslyduringmostmagmaticprocessesandthatthehfandNdisotopiccompositionsshouldbebroadlycorrelatedinmostcrustalandmantlerocks/少常用放射性同位素體系衰變常數(shù)半妄期(t半衰期地球年齡年(G48.849.84854.947506.5445.6Lu-HfisochrondatingismoreprecisethanSm-NdHf同位素分析技術(shù)的發(fā)展TMS技術(shù)PatchettandMatsumoto,1980)但TIMS方法難以對H實現(xiàn)有效的電離,從而使得實驗過程中樣品量較大(ug級H含量)。而這又使高質(zhì)量的純化(特別是Zr、H的分離)難以進行,并限制了低H含量樣品的分析。Hot-SIMS(Salters,1994)該方法是采用離子束對脫離燈絲的H進行轟擊,其,電離效率比TM高幾個數(shù)量級,樣品用量較TMS明顯減少。但這一方法的化學(xué)分離程序更加復(fù)雜,Zr、H的有效分離仍困擾著H同位素的發(fā)展。>MC-ICPMS((Halliday,1998)開創(chuàng)H同位素分析新局面據(jù)不完全統(tǒng)計,19992004年間發(fā)表的有關(guān)Hf同位素方面的文獻大約是前20年的兩倍Iyu.AN985199019952000圖1190年以來國際雜志發(fā)表的Hf同位素地球化學(xué)文獻大致情況(未包含會議摘要LuHf同位素體系衰變方程76Hf/7HD=76Hf/hFo(7Lu/yHf4×(e-1)Todefineanisochron,allsamplesinasuitemustmeetthefollowingconditions:(1)Theymusthavethesameinitialisotopiccomposition.(Thatis,theymusthaveinitiallybeeninisotopicequilibrium.Thisisgenerallythoughttobetrueforcogeneticigneousrocks),(2)Theymusthaveclosedatthesametime,and23)theymusthaveremainedclosedsystemswith7respecttotheparentanddaughterelementsbeinganalyzedInaddition,therocksmustspanarangeofparent-daughterratiostoprovidetightconstraintsontheslopeoftheisochron030sC,BINT01-50500-12820garnet6H02B5Age=1584±55MaMSWD-545Intia6HrH=028105±33(e=260)02E07eLu/77Hf含石榴石變質(zhì)巖石LuH同位素定年0292●SesiaLanzozora2±27Ny(phangtacametl與鋯石UoDoraMairamassifPb、sm(WR-gametgametNd等同位Impure.202的a±12M素體系定年(AR,結(jié)果較為4致0292E(Ducheneetal.,1997)2960136+04Msplex.LocationsareshowninFigure2.MSWD-meansquareofweighteddeviatesVerypreciseageswereobtainedbyLu-HfisotopesystemforMiocenesamples(Plattetal.,2006)51、天下之事常成于困約，而敗于奢靡。——陸游