The Transition Zone Slabs’ Purgatory - CIDER过渡区板炼狱-苹果酒.pptVIP

TheTransitionZone:

Slabs’PurgatoryCIDER,2006-GroupAGarrettLeahy,VedLekic,UrskaManners,ChristineReif,JoostvanSummeren,Tai-LinTseng,MagaliBillen,Wang-PingChen,AdamDziewonski

TongaSeismicity

PredictedSlabPositionsDegree45and24sphericalharmonicexpansionsoflocationsofslabsbasedonplatehistoryreconstructionsassumingnostagnationintransitionzone.

TomographicModelsHarvardBerkeley

PreliminaryConclusionsTomographyrevealslargerfastregionsinthewesternPacifictransitionzone.Deepearthquakestressaxesshowevidenceofresistancetocrossingthe660kmdiscontinuity.Structurebelowandabove660kmdiscontinuityhasdifferentspectralcharacter.Implication:slabsstagnateinthetransitionzoneforsomelengthoftime.

ASimpleForceBalanceforslabsintheTransitionZone

Fb=∫??gdxdz????????????xz

ConstraintsonDrandClapeyronslopesDensitycontrastsSeismicconstraintsLabexperimentsonmantleminerals/rocksLatticedynamicssimulationClapeyronslopesLabexperimentsonphasetransformationCalorimatricCalculations

SummaryPhaseTransitionData?SeismicConstrainsCalculations(Pyrolite)Simulations(MgSiO3)Dr4105%to6%About3%?Dr6607%to9%6%to7%About8%?LabExperimentsCalorimatricCalculationdP/dT410(Mpa/K)atob2.5to4dP/dT660(Mpa/K)gtoMw+Pv–3to–1About-3dP/dT660(Mpa/K)Pyrolite-0.5?DensityContrastClapeyronSlopeForClapeyronSlopeofOlivinePolymorphs:Duffy,T.,SynchrotronfacilitiesandthestudyoftheEarthsdeepinterior.Rep.Prog.Phys.68(2005)1811-1859.

SlabThermalAnomalyGaussianCross-slabProfileExponentialDecreaseInPeakAnomalyMax.SlabDepth:1000kmMax.SlabDepth:500km

PhaseTransitionAnomalyTemperatureAnomalyTransitionHeight(km)410:?=3.0MPa/K ??=3-6%660:?=-1.3MPa/K ??=7-9%410:=4.0MPa/K??=4%660:=-2MPa/K ??=3%

EffectofDiponSumofThermalAndPhaseChangeForces010---Dip(degrees)--8090TotalForce(x1012N/m)