简介：Hydrothermalchimneyisaproductofhydrothermalactivityontheseabed.ChimneysamplesdredgedfromJadehydrothermalareainIzenadepressionoftheOkinawaTrough,arecharacterizedbyrelativelyenrichedlightrareearthelements(LREE)andstronglypositiveEuanomalies.87Sr/86Srand143Nd/144Ndofthesesamplesareexactlybetweenthoseofseawaterandofacidicpumice,averagedat0.708928and0.512292,respectively.ThesecharacteristicsimplythatthemainsourceofhydrothermalsulfideatJadeareaispossiblytheundersurfaceacidicrocks.Themineralizingmechanismcanbesummarizedasfollows:LargeamountofmineralizedmaterialwouldbeleachedoutandLREEenrichedhydrothermalsolutionwouldbesubsequentlyproducedasaresultofthermo-chemicalexchangereactionbetweenacidicvolcanicrocksandheatedseawaterthatpenetratedinadvancefromupperwatermass.ThespurtingoutfromtheseabedandquicklycrystallizingintheseawaterofhydrothermalsolutionareresponsiblefortheformationofCu-Znsulfideandbarite-amorphousSiO2mineralsthatarecharacterizedbyenrichedLREEandpositivelystrongEuanomalies.

简介：Themajorelements,traceelements,K-ArageandSr-Nd-PbisotopicsystemsoftheCenozoicvolcanicrocksinDaheishanIslandandCishan,Penglai,ShandongProvincearemeasured.Thevolcanicrocks(olivine-nepheliniteandnepheline-basanite)inDaheishanIslanderuptedperiodicallyinanintervalof0.32Ma,from8.72Ma,8.39Ma,8.08Mato7.73Ma.ThevolcanicrocksareallrichinlightREEs.TheyaresimilartotheOIB-typealkalibasaltinthetraceelementsnormalizedmodelbyprimordialmantle:richinhighfieldelementssuchasNbandTa,andimcompatibleelementssuchasCs,Rb,Ba,Th,U.ThevolcanicrocksshowadepletionofKandRbelements.Itissuggestedbythetraceelementsthattheolivine-nepheliniteinDaheishanIslandisoriginatedfromdeepresourcesunderthecontinentalmantle.εNd(0)valuesofthevolcanicrocksinDaheishanIslandandCisbanare5.31～8.51and7.33respectively,suggestingthatthevolcanicrocksarefromthedepletedmantleresources,whichhavehigherSm/NdratiosthantheCHUR.143Nd/144NdratiosofDaheishanIslandolivine-nepheliniteandCishanalkalibasaltsare0.512910～0.513074and0.513014respectively.The87Sr/86SrofDaheishanIslandvolcanicrocksarelowerthanthatofCishan,0.703427～0.703482and0.703895respectively.TheDaheishanIslandolivinenephelinitehasthePbisotopicvaluesasfollows:206Pb/204pb=18.0289～17.9728,207Pb/204pb=15.4358～15.4022and208Pb/204Pb=38.0876～37.9975,lowerthanthoseofCishanbasanite.TheCishanbasanitehas206Pb/204pb=18.2401,207Pb/204Pb=15.5645and208Pb/204pb=38.535.Theauthorssuggestthattheolivine-nepheliniteinDaheishanIslandissimilartotheE-typeMORBorHawaiiOIB,andthealkalibasaltsinCishansimilartotheKerguelenOIB.ThedominantmantlecomponentsofDM+PREMAandperhapsDM(Dupaltype)arethedominantmantlecomponentsforvolcanicrocksinDaheishanIslandandCishan.ThePREMAcomponentplaysanimportantrole.