Abundances in the Universe/Crust Fe Be Mg Al Si Pb

Melting Temperature

Goldschmidt Classification

Chondrite Siderophile (Fe, Ni...) Lithophile (Si, Mg, Ca, Al, K...) Atmophile (N, He...)

INCOMPATIBLES U Th Al He COMPATIBILITY/INCOMPATIBILITY DURING PARTIAL MELTING

From Doin Sea surface (Geoid)

Background velocity Poiseuille Stokes Guess? Measured

Background velocity Poiseuille Stokes Hawaii 7.0 t/s Bowie 0.3 t/s All hostpots 55 t/s Slabs 650 t/s

From Hofmann

" 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)

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

ISOTOPIC RATIOS

Rares Gas From Hart & Zindler

Primitive Himu EM2 EM1

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

M Mass Balance for trace elements Primitive Mantle = Crust+Morb source+Hidden res

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?? pmol/g Another K-rich reservoir? From Davies

" 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)

Hiding a layer: Density and density jumps Phase changes Coupling between chemistry and phase jumps Viscous stratification

Less density chemical density difference is required at larger depth

MINERALOGY VS SEISMOLOGY From Matas

CLAPEYRON SLOPE P T Phase Dense Light Phase AveragePhase transition depth

From Machetel

Crust density: Mineralogy

Mantle, Lithosphere and oceanic crust

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

Seismic tomography

From Grant/Van der Hilst

Seismic tomography

Paleomap

Geoid Comp. Geoid

The Mantle viscosity increases with depth by a factor Can it help preserving primitive compositions?

Poloidal/Toroidal Bercovici

Poincar₫ Section

From Ferrachat

F arnetani or Schmalzl and Hansen Hotspot (no) Entrainment

Persistance of blobs Spence, Manga

Persistance of blobs Merveilleux Stretching Reorientation

500 myrs 2 byrs

Mantle, Lithosphere and oceanic crust

MANTLE Atmosphere C. Crust D '' Residual lith.

MANTLE Atmosphere C. Crust D '' Residual lith. Flux from hotspots Uniform growth Uniform growth Degassing No crustal recycling Fractionation + Fractionation -

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 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