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1、JOURNALOFGEOPHYSICALRESEARCH,VOL.105,NO.B7,PAGES16,651-16,664,JULY10,2000High-temperatureplasticdeformationofquartz-plagioclasemultilayersbylayer-normalcompressionShaochengJiD6partementdesG6niesCivil.G6ologiqueetdesMines,l•colePolytechniquedeMontr6al,Montr6
2、al,Qu6bec,CanadaRichardWirthandErikRybackiGeoForschungsZentmmPotsdam,Potsdam.GemsanyZhentingJiangDepartmentofEarthSciences,UniversityofLiverpool,Liverpool,England,UnitedKingdomAbstract.Itisacommonpracticeinrheologicalmodelingtotaketheextrapolatedcompressive
3、flowstrengthsofquartziteandplagioclaserockasthebulkflowstrengthsoftheupperandlowercontinentalcrusts,respectively.Suchapracticeimpliesthatthebulkflowstrengthofpolyphaserocksisidenticaltothatofthepureweakphase.Totestthisassumption,weperformeddeformationexperi
4、mentsonsyntheticlayeredandparticulatequartz-anorthite(50:50)compositesandaggregatesoftheend-membersinaPatersongas-mediumapparatusataconfiningpressureof300MPa,aconstantstrainrateof10'5s-1andtemperaturesh'om1273to1473K.Undertheseconditions,anorthitedeformsbyr
5、ecrystallization-accommodateddislocationcreep,whilequartzissemibrittle.Electronbackscatterdiffractionmeasurementsshowastronglattice-preferredorientation(LPO)ofm•orthitedevelopedindeformedspecimens,andtheLPOpatternisinterpretedasaresultofdislocationsliponthe
6、(010)[100]system.Ourexperimentalresultsshowthatthebulkflowstrengthoflayeredcompositesincreaseswithdecreasingthicknessofthelayers.Thin-layeredcompositesaresignificm•tlystrongerthm•pureanorthiteaggregatesandahomogeneousquartz-anorthitemixture(i.e.,particulate
7、composites)withthesamemodalcompositionbutweakerthanpurequartzaggregates.Ourexperimentalresultstogetherwiththetheoreticaloverviewpresentedpreviouslyinthematerialsscienceliteraturedemonstratethat(1)compressiveflowstrengthofapolyphaserockcannotberepresentedbyt
8、hatoftheweakphaseand(2)thin-layeredrockscompressednormaltothelayeringaretheologicallystrongerthanhomogeneous,isotropicmixturesunderthestonedeformationconditions.Thusweak-phase-basedrheologywillleadtoan