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Abundances in the Universe/Crust Fe Be Mg Al Si Pb
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Melting Temperature
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Goldschmidt Classification
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Chondrite Siderophile (Fe, Ni...) Lithophile (Si, Mg, Ca, Al, K...) Atmophile (N, He...)
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INCOMPATIBLES U Th Al He COMPATIBILITY/INCOMPATIBILITY DURING PARTIAL MELTING
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From Doin Sea surface (Geoid)
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Background velocity Poiseuille Stokes Guess? Measured
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Background velocity Poiseuille Stokes Hawaii 7.0 t/s Bowie 0.3 t/s All hostpots 55 t/s Slabs 650 t/s
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From Hofmann
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" DEPLETED MORB SOURCE " ENRICHED HIMU, EM, CC SOURCES " PRIMITIVE/DEPLETED LOIHI SOURCE? " CC and MORB SOURCE complementary " Nb, Pb, Ti anomalies due to subduction (CC, MORB and OIB)
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D/N=D 0 /N+P 0 /N(1-exp(t/T)) D=daughter P=parent N=reference stable isotope of D T=time constant
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ISOTOPIC RATIOS
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Rares Gas From Hart & Zindler
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Primitive Himu EM2 EM1
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MORB Midocean ridge basalt extracted from MORB source or DMM OIB Oceanic ridge basalt extracted from????? Primitive Mantle (PREMA) Loihi-Icelandic Type (Primitive HE Mantle) EM1 (Enriched Mantle=oceanic sediments?) EM2 (Enriched Mantle=continental sediments?) HIMU (high U/Pb=oceanic crust?) FOZO-C
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M Mass Balance for trace elements Primitive Mantle = Crust+Morb source+Hidden res
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40 Argon Produced in the Earth 940 pmol/g Atmosphere 44% Crust 3.5% Upper mantle.9 % (25 pmol/g) Lower mantle 52 % (720 pmol/g) But K/U?? 50-200 pmol/g Another K-rich reservoir? From Davies
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" OIBs are more heterogeneous than MORBs " But the same trends are seen in MORBs and OIBs " There is a hidden reservoir = Slightly depleted=lower mantle = Primitive=50% of the mantle = Enriched (D'' with MORBs composition)
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Hiding a layer: Density and density jumps Phase changes Coupling between chemistry and phase jumps Viscous stratification
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Less density chemical density difference is required at larger depth
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MINERALOGY VS SEISMOLOGY From Matas
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CLAPEYRON SLOPE P T Phase Dense Light Phase AveragePhase transition depth
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From Machetel
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Crust density: Mineralogy
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Mantle, Lithosphere and oceanic crust
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DOUBLE PHASE CHANGES P T Dense Phase A Light Phase A Average Phase transition depths for A and B Light Phase B Dense Phase B
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Seismic tomography
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From Grant/Van der Hilst
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Seismic tomography
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Paleomap
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Geoid Comp. Geoid
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The Mantle viscosity increases with depth by a factor 10-100 Can it help preserving primitive compositions?
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Poloidal/Toroidal Bercovici
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Poincar₫ Section
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From Ferrachat
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F arnetani or Schmalzl and Hansen Hotspot (no) Entrainment
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Persistance of blobs Spence, Manga
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Persistance of blobs Merveilleux Stretching Reorientation
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500 myrs 2 byrs
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Mantle, Lithosphere and oceanic crust
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MANTLE Atmosphere C. Crust D '' Residual lith.
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MANTLE Atmosphere C. Crust D '' Residual lith. Flux from hotspots Uniform growth Uniform growth Degassing No crustal recycling Fractionation + Fractionation -
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No real geochemical indication of the existence of primitive material Strong indications that the 670 km depth boundary is permeable Strong indications of a viscosity increase with depth by 10-100 This viscosity increase does not stratify the mixing 3D convection more efficient mixer with, than without plates Highly viscous, small, primitive blobs may survive(?) Need of a reservoir to store incompatible elements Seems difficult to hide a dense reservoir in the mantle Crust segregation in D'' may be the deep enriched reservoir (EM, HIMU) The remaining lithosphere may be the depleted (''primitive-like'') reservoir
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