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)

Backgroundvelocity

Poiseuille

Stokes

Guess?

Measured

Backgroundvelocity

Poiseuille

Stokes

Hawaii 7.0 t/sBowie 0.3 t/s

All hostpots 55 t/sSlabs 650 t/s

From Hofmann

DEPLETED MORB SOURCEENRICHED HIMU, EM, CC SOURCESPRIMITIVE/DEPLETED LOIHI SOURCE?CC and MORB SOURCE complementaryNb, Pb, Ti anomalies due to subduction (CC, MORB and OIB)

D/N=D0/N+P

0/N(1-exp(t/T))

D=daughterP=parent

N=reference stable isotope of DT=time constant

P D N106

87 Sr 86 Sr 49

40 K 1U 0.7

Tln(2) Ga

147 Sm 143 Nd 144 Nd87 Rb

40 Ar 36 Ar4 He 3 He

ISOTOPIC RATIOS

Rares Gas

From Hart & Zindler

Primitive

Himu

EM2

EM1

MORB Midocean ridge basaltextracted from MORB source or DMM

OIB Oceanic ridge basaltextracted 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

40Argon

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

OIBs are more heterogeneous than MORBsBut the same trends are seen in MORBs and OIBsThere is a hidden reservoirSlightly depleted=lower mantlePrimitive=50% of the mantleEnriched (D'' with MORBs composition)

Hiding a layer:

Density and density jumpsPhase changesCoupling between chemistry and phase jumpsViscous 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 depthsfor 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 10-100

Can it help preserving primitive compositions?

Poloidal/Toroidal

Bercovici

Poincar₫ Section

From Ferrachat

Farnetani or Schmalzl and Hansen

Hotspot (no)Entrainment

Persistance of blobs

Spence, Manga

Persistance of blobs

Merveilleux

Stretching StretchingStretching Stretching

Reorientation Reorientation

500

myr

s

2 byrs

Mantle, Lithosphere and oceanic crust

MANTLE

Atmosphere

C. Crust

D ''

Residual lith.

MANTLE

Atmosphere

C. Crust

D ''

Residual lith.Flux fromhotspots

Uniformgrowth

Uniform growth

Degassing

No crustalrecycling

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 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