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简介：Calculations,accordingtosomeopen-systemmodels,pointoutthatwhileastatisticallysignificantdiscrepancybetweentheresultsoftwoU-seriesmethods,^230Th/^234Uand^227Th/^220Th(or^231Pa/^235U),attestsarelativelyrecentandimportanturaniummigration,concordantdatescannotguaranteecloses-systembehaviorofsample.Theresultsof20fossilbonesfrom10Chinesesites,19ofwhicharedeterminedbytwoU-seriesmethods,aregiven,Judgingfromindependentagecontrols,8outofthe11concordantagesetsareunacceptable,Theresultsinthispapersuggestthaturaniummaycycleintooroutoffossilbones,suchgeochemicaleventsmaytakeplaceatanytimeandnoknownpreservingconditionmaysecurelyprotectthemfrombeingaffected.Soforthesitewwehavestudied,theU-seriesdatingoffossilbonesisoflimitedreliability.