简介：TheX-discontinuity,whichappearsatthedepthofapproximately300km,isanimportantseismicinterfacewithpositivevelocitycontrastsintheuppermantle.Detectingitspresenceandtopographycanbeusefultounderstandphasetransformationsofrelevantmantlemineralsunderthehigh-temperatureandhigh-pressurecircumstanceoftheEarth'sinterior.Inthisstudy,wedetecttheX-discontinuitybeneaththeRyukyusubductionzoneusingfiveintermediate-deptheventsrecordedbythedenseAlaskaRegionalNetwork(AK).TheX-discontinuityissuccessfullyrevealedfromtherobustslantstackingofthesecondarydown-goingandconvertingSdPphases.Fromthedepthdistributionofconversionpoints,wefindthattheX-discontinuity'sdepthrangesbetween269kmand313km,withanaveragedepthof295km.Alltheconversionpointsarelocatedbeneaththedown-dippingsideofthePhilippineSeaslab.Fromenergycomparisonsinvespagramsforobservedandsyntheticseismograms,thestrongconvertedenergyismorelikelyfromathinhigh-velocitylayer,andtheS-wavevelocityjumpsacrosstheX-discontinuityareupto5%to8%withanaverageof6.0%.Accordingtopreviouspetrologicalandseismologicalstudies,theX-discontinuitywedetectedcanbeinterpretedasthephasetransformationofcoesitetostishoviteineclogiticmaterialswithintheoceaniccrust.

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简介：Amapoftheaverageatomicnumberoflunarrockandsoilcanbeusedtodifferentiatelithologyandsoiltypeonthelunarsurface.Thispaperestablishesalinearrelationshipbetweentheaverageatomicnumberoflunarrockorsoilandthefluxofpositionannihilationradiation(0.512-MeVgamma-ray)fromthelunarsurface.TherelationshipisconfirmedbyMonteCarlosimulationwithdatafromlunarrockorsoilsamplescollectedbyLuna(Russia)andApollo(USA)missions.AmapoftheaverageatomicnumberofthelunarrockandsoilonthelunarsurfacehasbeenderivedfromtheGamma-RaySpectrometerdatacollectedbyChang’e-1,anunmannedChineselunar-orbitingspacecraft.Inthemap,thehigheraverageatomicnumbers(ZA>12.5),whicharerelatedtodifferenttypesofbasalt,areinthemariaregion;thehighestZA(13.2)readingsareassociatedwithSinusAestuum.ThemiddleZA(~12.1)regions,intheshapeofirregularovalrings,areinWestOceanusProcellarumandMareFrigoris,whichseemstobeconsistentwiththedistributionofpotassium,rareearthelements,andphosphorusasauniquefeatureonthelunarsurface.Theloweraverageatomicnumbers(ZA<11.5)arefoundtobecorrelatedwiththeanorthositeonthefarsideoftheMoon.