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SOME FIGURES FOR UNFINISHED MANUSCRIPTS (CONDENSED; FULL VERSION CAN BE REQUESTED VIA DROPBOX)
410
650
eclogiteharzburgite
cold
cold
Shear wavespeed Temperature
BL
High-T conduction geotherm
Subadiabatic geotherm
1600 C adiabat
Vs for self-compressed solid along adiabat
ObservedSeismic profile
VSH>VSV
VSV>VSH
RIDGEOIB
Tp=~1300 C
~1600 C
650 km
220 km
1
33
2
4
5
6
7
A mantle circulation model based on anisotropy, anharmonicity, absolute wavespeeds & gradients, allows for, and predicts, non adiabaticity
disconnect
LIL Sheared mélange
ridge
UPPER MANTLE
Tp
200
400kmAncient eclogite
cumulates Modern slab fragments
LVZ
TZ
LIL
THE “NEW” PARADIGM
hotspots
“the canonical box”
‘cold’
Sedimentsvolatiles
Intraplate volcanoesMidocean ridges
Residual slab components
LOWER MANTLE
*Essentially the classical model of Birch, Tatsumoto, Wilson…
200 Myr of oceanic crust accumulation
TRANSITION ZONE (TZ)
REGION BSuper-adiabatic boundary layer
Thermal max
600 km
300 km
Tp decreases with depth
600 km
Physics-Based Archimedian Paradigm*
(RIP)
(* Birch, Tatsumoto, J. Tuzo Wilson)
Shear strain
“fixed”Hawaii source
MORB source
Shear-driven magma segregation
Sources deeper than ~ 150-200 km are effectively fixed(e.g.J.T.Wilson)
OIB
(T), (V,T), TCMB(t), (V,T),U(z,t), Th(z,t)…
PebblesOld GreeksSlabs
The Eureka Solution
Archimedes & Birch
squeezing
squeezing
ISOTHERMAL
ADIA
BATI
C
ISOTHERM
ISOTHERM 100 km
HOMOGENEOUS
jet
STANDARD CONCEPTUAL MODEL (1988) No physics, no seismology
(used as reference model; Herzberg, Asimow, Humphreys, Schmandt, Victor Camp…e.g…)
No U, Th, KNo secular coolingAmbient T constrained (<1600K)
Mechanical boundary layer
Thermal boundary layer
Adiabatic interior
Lithosphere
Tp=1280o
Tp(max)~1600o
LID LLAMA subadiabat
Negative Vs gradient
0 100 200 300 Depth (km)
1600
1200
800
400
0
T (oC)
BOUNDARY LAYER
Cambridge nomenclature
UPPER MANTLE & LOWER MANTLE ARE COOLED BY LONG-LIVED FLAT (STAGNANT) SLABS
Cold slab
European, African, Asian (Changbai), Yellowstone & most continental intra-plate volcanoes (“hotspots”) are underlain by slabs
Cooled mantle
49
COLD
WARM
REGION B
TZ
Ridges & hotspots
COOL
410
650
No hotspots
LVA
STAGNANT SLABS–A FIXED REFERENCE FRAME
SLIP-FREE BOUNDARY
50There may be a concentration of CaO, Al2O3, K…U, Th…in the upper mantle…Birch
Boundary layer
Midplate
Ridge adiabat
LLAMA(shearing)
Plate (conducting)
Depth
16001400
T oC
T
Depth
B
D”
TZ
CMB
Illustrating the thermal bump and subadiabaticity
UPPER MANTLE
LOWER MANTLE
The highest potential temperature in the mantle is near 200 km. Tectonic processes (shear, delamination) are required to access this.
ridge midplate
bump
(& backarc)
400200
(Lubimova, MacDonald, Ness)
U, Th, K and other LIL are concentrated in the crust & the upper mantle boundary layer during the radial zone refining associated with accretion (Birch, Tatsumoto…). This accentuates the thermal bump.
Mesosphere (TZ)
LIDLVZ
LLAMA200
400
Intraplate (delamination, CRB, Deccan, Karoo, Siberia) magmas are shear-driven from the 200 km thick shear BL (LLAMA)
ridge
km Cold slabs
SUMMARY
OIB
Ridges are fed by broad 3D upwellings plus lateral flow along & toward ridges
subadiabatic