%0 Journal Article
%T GeochemicalCharacteristicsofVolcanicRocksfromODPSite794,YamatoBasin:ImplicationsforDeepMantleProcessesoftheJapanSea
%A CHEN
%A Shuangshuang
%A LIU
%A Jiaqi
%A *GUO
%A Zhengfu
%A CHEN
%A Shengsheng
%A and
%A SUN
%A Chunqing
%J µØÖÊѧ±¨
%P 1189-1212
%D 2015
%X DeepmantleprocessesandthedynamicmechanismofmagmatismintheJapanSeaBasinareimportantprocessesthathavenotbeenstudiedindetail.Inthispaper,systematicevaluationofbasaltsamplesfromtheoceandrillingprogramSite794intheJapanSeawasperformed,whichincludedpetrography,whole-rockmajor-andtrace-elementanalysis,Sr?Nd?Pbisotopiccomposition,andelectronmicroprobeanalysisofplagioclaseandclinopyroxene.ThesebasaltsbelongtothetholeiiticserieswithporphyritictextureandmassiveCa-richplagioclase,clinopyroxene,andminorolivinephenocrysts.Thebasaltsarecharacterizedasflatrareearthelementsandhigh-field-strengthelementswithremarkablylowratiosof(La/Yb)N(0.75£¿2.51),significantpositiveanomaliesofBa,Sr,andRbandnoEuanomaly(¦ÄEu=0.99£¿1.36).Thesamplesshowedrelativelyhigh87Sr/86Sr(0.70425£¿0.70522),207Pb/204Pb(15.511£¿15.610),and208Pb/204Pb(38.064£¿38.557)valuesandalow143Nd/144Ndratio(0.51271£¿0.51295).ThebasaltsfromSite794canbedividedintoupper,middle,andlowervolcanicrocks(UVR,MVR,andLVR)onthebasisoftheirstratigraphiclevel.TheMVRwasgeochemicallyderivedfromthedepletedmantle,whereastheUVRandLVRoriginatedfromanondepletedandrelativelyenrichedmantlesourcewithcontributionsfromsubductedPacificplatefluidandsediments.UseofgeothermobarometersindicatesthatthecrystallizationpressurefortheUVRandLVR(6.25£¿11.19kbar)wassignificantlyhigherthanthatoftheMVR(3.48£¿5.84kbar).TheUVRandLVRmayhavebeenderivedfromthelow-degree(5%£¿10%)partialmeltingofspinellherzolite,whiletheMVRoriginatedfromashallowermantlesourcewithahighdegree(10%£¿20%)ofpartialmelting.Inaddition,thegeochemicalcharacteristicsofthesamplesareconsistentwithayoungerage(13£¿17Ma)andthedepletedcompositionoftheMVRandanolderage(17£¿23Ma)andslightlyenrichedcompositionoftheUVRandLVR.Therefore,temporalchangesinthemantlesourcefromoldandenrichedtoyounganddepletedandsubsequentlytooldandnondepletedmayhavebeenassociatedwithprogressivelithosphericextensionandthinning,aswellasatleasttwoepisodesofdiverseasthenosphericupwellingandpull-aparttectonicmotionintheYamatoBasin.
%K Basalt
%K deepmantleprocess
%K geothermobarometer
%K YamatoBasin
%U http://www.geojournals.cn/dzxb/ch/reader/view_abstract.aspx?file_no=201504010&flag=1