Interpreting Geophysical Data for Mantle Dynamics

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Interpreting Geophysical Data for Mantle Dynamics

• Wendy Panero
• University of Michigan

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Chemical Constraints on Density Distribution
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Chemical Constraints on Density Distribution
Stacy Geotherm
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Cold Slabs, Clapeyron Slopes and Whole Mantle
Convection
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Clapeyron Slope
Equilibrium DG1DG2
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Cold Slabs, Clapeyron Slopes and Whole Mantle
Convection
Clapeyron slope must be greater than ask a
geodynamicist
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Determination of Clapeyron Slopes
Phase Equilibria ex-situ in-situ Thermodynamic
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Determination of Clapeyron Slopes
Ringwoodite (Smyth)
Phase Equilibria ex-situ in-situ Thermodynamic
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Multi-Anvil Press
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Determination of Clapeyron Slopes
Ito and Takahashi 1989
Phase Equilibria ex-situ in-situ Thermodynamic
Clapeyron slope -2.8 MPa/K
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Determination of Clapeyron Slopes
Ringwoodite (Smyth)
Phase Equilibria ex-situ in-situ Thermodynamic
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The Laser-Heated Diamond Anvil Cell
X-ray
Heating laser
Pressure Force/Area
0.1 mm
2 cm
X-ray diffraction (pressure, structure, density)
Spectroradiometry (temperature)
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Techniques
X-ray Diffraction
Diffraction condition
l2dsin(2q)
2q
e.g. Cullity
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Techniques
X-ray Diffraction
Ringwoodite
Perovskite periclase
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Temperature Measurements
hotspot
gasket
O2
ruby
(Benedetti et al, unpublished)
top view
side view
Kavner and Panero, PEPI 2004
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Pressure MeasurementsEquations of State
Lee et al., 2004
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Constant Temperature Equations of State
Bulk Modulus
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Constant Temperature Equations of State
Lee et al., 2004
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PVT Equations of State
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PVT Equations of State
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Determination of Clapeyron Slopes
Shim et al., 2001
Phase Equilibria ex-situ in-situ Thermodynamic
Clapeyron slope -3 MPa/K (Irifune et al.,
1998) Clapeyron slope no constraint (Shim et
al., 2001 Chudinovskikh et al., 2001)
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Sources of Error
Non-hydrostatic stresses Pressure
standards Temperature and pressure gradients
Diffracted x-ray
Incoming x-ray
VhydrostaticltVnon-hydrostatic
diamond
diamond
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Sources of Error
Non-hydrostatic stresses Pressure
standards Temperature and pressure gradients
Kavner and Duffy, 2003
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Sources of Error
Non-hydrostatic stresses Pressure
standards Temperature and pressure gradients
Gold relative to Platinum
Shim et al., 2001
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Sources of Error
Non-hydrostatic stresses Pressure
standards Temperature and pressure gradients
hotspot
gasket
O2
ruby
(Benedetti et al, unpublished)
top view
side view
Kavner and Panero, PEPI 2004
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Determination of Clapeyron Slopes
Phase Equilibria ex-situ in-situ Thermodynamic
Clapeyron slope -42 MPa/K
Ito et al., 1990
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Interpretation of TomographyThermal Variations
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Interpretation of TomographyCompositional
Variations
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Interpretation of TomographyCompositional
Variations
Perovskite Composition K0 (GPa) r (Mg/m3)
(km/s)
7.974
MgSiO3
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4.12
7.851
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4.25
MgSiO310 FeO
7.956
4.123
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MgSiO3 3.25 Al2O3
256
4.088
7.913
MgSiO3 3.25 Al2O3H2O
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Theory

• Quantum mechanical or classical
• effects of a priori assumptions
• size of calculation, time for calculation

General approach G of each phase PT-space for
lowest energy
Limitations Temperature Multi-component systems
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Theory
MgSiO3 perovskite
Wentzcovitch et al., 2004
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