Cordier_dislocation and slip system of mantle minerals

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1、6DislocationsandSlipSystemsofMantleMineralsPatrickCordierLaboratoiredeStructureetPropriétésdel'EtatSolide(ESACNRS8008)UniversitédesSciencesetTechnologiesdeLille59655Villeneuved'Ascq-Cedex,FranceINTRODUCTIONThischapterfocusesondislocationsandslipsystemsthata

2、reresponsiblefortheplasticflowofhigh-pressuremantleminerals.Afterbrieflyintroducingsomebasicconceptsoncrystalplasticity,wedescribesomerecentexperimentaladvancesofthelastdecadethathavecontributedtoourunderstandingoftherheologyofmantleminerals.Amongthem,wedes

3、cribesomeprogressintheachievementofdeformationexperimentsunderhighpressure.AmoredetailedreviewispresentedbyDurhametal.(thisvolume).WepresentthenanovelTransmissionElectronMicroscopy(TEM)technique:LargeAngleConvergentBeamElectronDiffraction(LACBED),whichisver

4、ywelladaptedtothecharacterizationofdislocationsinbeamsensitivematerials,aswellasthedeterminationofdislocationBurgersvectorsandcharactersfromthefineanalysisofX-raydiffractionpeakbroadening.Thepresentreviewisinthecontinuityofthepaperentitled“PlasticRheologyof

5、Crystals”byPoirier,publishedin1995in“MineralPhysics&Crystallography—AHandbookofPhysicalConstants”(AGUReferenceShelf2).Poirier'spaperreviewedtheplasticityofsomeimportantmineralsincludingolivineandpyroxenes.Concerningthesetwominerals,thereaderisinvitedtorefer

6、toPoirier'scontribution.In1995,Poirierstatedabouthigh-pressuremantleminerals:“Despitetheirimportancefortherheologyofthetransitionzoneandthelowermantle,thereisnoinformationontheplasticityofthehigh-pressuremantlemineralsintherelevantconditionsoftemperatureand

7、pressure.”Sevenyearslater,thesituationhassignificantlyevolvedandisstillrapidlychanging.Itistheaimofthispapertohighlighttheserecentadvances.BASICCONSIDERATIONSPlasticflowisbasicallyatransportphenomenoncontrolledbythemotionofdefects:pointdefects,dislocations,

8、orgrainboundaries.Thedrivingforceisprovidedbytheappliedshearstress.Inmanycases,deformationisproducedbythemotionofdislocationsandthepresentpaperwillfocusonthisaspectonly.ThestrainratethenobeystheOrowan'