简介：<正>StudiesontheaerolitefragmentsfromBaishacrater,HainanIslandprovethattheybelongtocalcium-richachondritewhicharerelictsofcrateringmeteoriteoftheBaishacrater.Theseflat-ballshapedaerolitefragments,sizebeing21cm×18.5cm×8.7cm,werefoundinacreekwithintheBaishacrater.Thishardaeroliteweigh3.75kgwithadensityof3.46g/cm3.Itismantledbya0.1-0.5cmthick,brownshellanditsfreshsectionisdark-grey.Theaeroliteischaracterizedbyporphyritictextureandnospherulitictexturehasbeenfound.Microscopicexamination,X-raydiffractionanalysisandelectronicprobeanalysis

简介：Avolcano-platformcarbonatesequence,fromCarboniferoustoPermian,iswidelytrappedinthedeepwaterdepositsinChangning—Menglianbelt.Threecomponentscanberoughlyrecognizedinas-cendingorderas:thelava,thevolcaniclasticandcarbonaterocks.Inmostcases,thesequenceisincompleteduetofaultingresultedfromthestrongorogeniccompression.Butthestratigraphicsuccessioniscontinu-ousexceptforthetwointerruptionsofpaleokarsts,whichextendedfrommiddleLateCarboniferoustoLatePermianandfromlateEarlyPermiantoLatePermianrespectively.Apreliminarystudyindicatesthatthestratigraphy,petrology,sedimentation,volcanismgeochemistryandfossilsinthesequencearequitesimilartothatinmodemandancientoceanicislandsandtheremaybetherelicsofancientoceanicislandsinthepaleo-Tethys.Thedifferencesamongthesesequencesprobablysuggestacomplexconfigu-rationoftheislandsorislandchainTheseislandswereformedunderintra-oceanicenvironmentsofthepaleo-Teth

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简介：ObjectiveUnderstandingthedynamicsofsedimentgravityflowsisofgreatimportancetocorrectlyinterprettheirrelateddeposits.Thediscoveryofsupercriticalsedimentgravityflowsprovidessomenewviewpointsfortheexplanationofcontroversialsedimentgravityflowdeposits.However,thedynamics,formation,evolutionprocessesofsupercritical

简介：0IntroductionTheJapaneseIslandsconsistoffivevolcanicarcs(Fig.1).TheNorth-EastandSouthWestJapanarcstogetherformtheHonshuarc,towhichtheKurilearcjoinsatHokkaido,whereastheIzu-MarianaarcjoinsatIzu-FossaMagna,andtheRyukyuarcjoinsatKyushu.Theseregionswherevolcanicarcsconverge,aretermed'islandarcjunctions'.

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简介：Sm-Ndisotopiccompositionsofeightlamprophyresamples,whichcomefromtheGezhengold-bearingshearzoneonwesternHainanIsland,aremeasured.TheSm-Ndisochronageis495.98±13.14Ma,(143Nd/144Nd)0=0.512094,εNd(t)rangesfrom+1.80to+2.00andTDMfrom982Mato1196Ma(average:1060Ma).Theauthorspointoutthatthewhole-rockSm-Ndisochronage(495.98±13.14Ma)reallyrepresentsthepetrogeneticageoflamprophyreandthetimeofmagmatismduringsubsequentsubduction.

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简介：EarlyPaleozoicgranodioritehasbeenidentifiedonthenorthernmarginoftheNorthChinacratonintheeastsectionofthecentral-Asianorogenicbelt,whichwaspreviouslyknownasearlyIndosinianinage.ByusingtheLA-ICP-MSmethod,theobtainedzirconU-Pbageis445.62.7Ma,whichrepresentsthecrystallizationageofthegranodiorite.Thegranodioriteneartheeastofthelarge-sizedBilihegolddepositisofthetholeiiteserieswithlowpotassium.Itisquasi-aluminousI-typegranite,enrichedinsodium(Na2O/K2O=7.299.77)andmagnesium(Mg#=0.510.67).TheΣREEvalueisrelativelylow,obviousdifferentiationisshownbetweenLREEandHREEandwithinLREE,andtheEuanomalyislowandnegative(δEu=0.740.91).Intheprimitive-mantlenormalizedspiderdiagramsoftraceelements,thegranodioriteisrelativelyrichinLREEandLILE(Ba,Sr,Th),andstronglydepletedinHFSE(Nb,Ta,TiandP),whichshowsfeaturesofsubductionzonecomponents(SZC).InthediscriminationdiagramsoftectonicsettingsofgraniteforRbvs.(Nb+Y),Rbvs.(Ya+Ta),La/Nbvs.Ba/NbandTh/Nbvs.Ba/Nb,thegranodioriteexhibitstypicalfeaturesofislandarcgranite.ThenormalizedvaluesofKandRbareextremelylow,whilethevaluesofSrandEuareveryhigh,whicharesimilartothoseofislandarcmagmathathasundergonemetasomatismoffluidfromtheoceaniccrust.ThegranodioriteisrelativelydepletedinεHf(t)(5.17.1)andlowinεHf(t)modelages(1089921Ma).IntheεHf(t)vs.age(T)diagram,thedistributionareaofthegranodioriteisaccordantwiththefieldoftheXing'anling-Mongoliaorogenicbelt,whichindicatesthatthemagmaticsourcesaremainlythemixtureofpartialmeltingofwedgedmantlesubjectedtometasomatismoffluidfromtheoceaniccrustandyoungsubstancefromthecrust.ThegranodioriteissimilartothefelsicarcmagmaintheDamaoBanner,BateObon,BoinSumandOrdorSumregions,andtheyaltogetherconstituteanearlyPaleozoicaccretionaryislandarcma