* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Composition and Structure of Earth`s Interior
Survey
Document related concepts
Viscoelasticity wikipedia , lookup
Colloidal crystal wikipedia , lookup
High-temperature superconductivity wikipedia , lookup
Heat transfer physics wikipedia , lookup
Temperature wikipedia , lookup
Superconductivity wikipedia , lookup
Shape-memory alloy wikipedia , lookup
State of matter wikipedia , lookup
Diamond anvil cell wikipedia , lookup
Thermodynamic temperature wikipedia , lookup
Sol–gel process wikipedia , lookup
Spinodal decomposition wikipedia , lookup
Condensed matter physics wikipedia , lookup
Transcript
Composition and Structure of Earth’s Interior A Perspective from Mineral Physics 7/12/04 CIDER/ITP Short Course Mineral Physics Program Fundamentals of mineralogy, petrology, phase equilibria • Lecture 1. Composition and Structure of Earth’s Interior (Lars) • Lecture 2. Mineralogy and Crystal Chemistry (Abby) • Lecture 3. Introduction to Thermodynamics (Lars) Fundamentals of physical properties of earth materials • Lecture 4. Elasticity and Equations of State (Abby) • Lecture 5. Lattice dynamics and Statistical Mechanics (Lars) • Lecture 6. Transport Properties (Abby) Frontiers • Lecture 7. Experimental Methods and Challenges (Abby) • Lecture 8. Electronic Structure and Ab Initio Theory (Lars) • Lecture 9. Building a Terrestrial Planet (Lars/Abby) Tutorials • Constructing Earth Models (Lars) • Constructing and Interpreting Phase Diagrams (Abby) • Interpreting Lateral Heterogeneity (Abby) • Molecular dynamics (Lars) • Earth as a material – – – – Outline What is Earth made of? What are the conditions? How does it respond? How do we find out? • Structure and Composition – Pressure, Temperature, Composition – Phases – Radial Structure • Origins of Mantle Heterogeneity – Phase – Temperature – Composition What is Earth made of? • Atoms – Contrast plasma ... – All processes governed by • Atomic arrangement (structure) • Atomic dynamics (bonding) • F = kx – F : Change in energy, stress – x : Change in temperature, phase, deformation – k : Material property • Beyond continuua – Measure k – Understanding What is Earth made of? • Condensed Matter – Potential Energy, i.e. bonds, are important – No simple theory (contrast ideal gas) • Pressure Scale – Sufficient to alter bonding, structure – Not fundamental state – Pbond~eV/Å3=160 GPa~Pmantle What is Earth made of? • Solid (mostly) – Response to stress depends on time scale – Maxwell relaxation time M viscosity G shear modulus M ~1000 years • Crystalline – Multi-phase – Anisotropic How does it respond? • To changes in energy – Change in temperature • Heat Capacity CP, CV – Change in Density • Thermal expansivity, – Phase Transformations • Gibbs Free Energy, G • Influence all responses in general How does it respond? • To hydrostatic stress – Compression • Bulk modulus, KS, KT – Adiabatic heating • Grüneisen parameter • =KS/cP – Phase Transformations • Gibbs Free Energy • To deviatoric stress – Elastic deformation • Elastic constants, cijkl – Flow • Viscosity, ijkl – Failure How does it respond? • Rates of Transport of – Mass: chemical diffusivity – Energy: thermal diffusivity – Momentum: viscosity – Electrons: electrical conductivity • Other Non-equilibrium properties – Attenuation (Q) – … How do we find out? • How does interior differ from laboratory? – The significance of the differences depends on the property to be probed • Equilibrium thermodynamic properties – Depend on Pressure, Temperature, Major Element Composition. – So: Control them and measure desired property in the laboratory! Or compute theoretically • Non-equilibrium properties – Some also depend on minor element composition, and history – These are more difficult to control and replicate How do we find out? 1.08 q0±1 1.07 0±0.1 1.06 Relative Volume, V/V 0 • Experiment • Production of high pressure and/or temperature • Probing of sample in situ 1.05 1.04 Bouhifd et al. (1996) 1.03 1.02 Forsterite 0 GPa 1.01 1.00 400 800 1200 1600 Temperature (K) 2000 How do we find out? 35 -1 Temperature Derivative of G, -dG/dT (MPa K ) • Theory • Solve Kohn-Sham Equations (QM) • Approximations MgSiO3 Perovskite 2500 K 30 Oganov et al. (2002) 25 S=S0 S~ Marton & Cohen (2002) 20 S~q Wentzcovitch et al. (2004) 15 10 S~q 0 20 40 60 80 100 Pressure (GPa) 120 140 Pressure, Temperature, Composition • P/T themselves depend on material properties • Pressure: Self-gravitation modified significantly by compression • Temperature: Selfcompression, energy, momentum transport • Composition – Heterogeneous – Crust/Mantle/Core – Within Mantle? Pressure, Temperature, Composition PREM 300 250 200 Transition Zone • K=bulk modulus • Must account for phase transformations… 350 Upper Mantle P (r)g(r) r • Combine P K Pressure (GPa) Pressure Lower Mantle 150 Outer Core 100 Inner Core 50 0 0 2000 4000 Depth (km) 6000 Temperature • Constraints: near surface – Heat flow – Magma source – Geothermobarometry – Phase transformations – Grüneisen parameter – Physical properties • Properties of Isentrope T≈1000 K – Verhoogen effect • Questions – Boundary layers? – Non-adiabaticity? 2600 Temperature (K) • Constraints: interior 2800 2400 2200 2000 1800 1600 0 1000 2000 Depth (km) 3000 Composition • Constraints: extraterrestrial – Nucleosynthesis – Meteorites • Constraints: near surface – Xenoliths – Magma source • Constraints: Interior – Physical properties • Fractionation important – Earth-hydrosphere-space – Crust-mantle-core • Mantle homogeneous because well-mixed? – Not in trace elements – Major elements? Pyrolite/Lherzolite/Peridotite/… Phases • Upper mantle – Olivine, orthopyroxene, clinopyroxene, plagspinelgarnet • Transition Zone – OlivineWadsleyiteRingwoo dite – Pyroxenes dissolve into garnet • Lower mantle – Two perovksites + oxide • What else? – Most of interior still relatively little explored Radial Structure • Influenced by pv capv Shear Wave Velocity (km s-1) – Pressure – Phase transformation – Temperature 6.5 6.0 ak mw ri 5.5 5.0 wa sp C2/c gt ol mj opx 4.5 cpx 4.0 3.5 0 plg 200 400 Depth (km) 600 Radial Structure of Pyrolitic Mantle • Lower mantle • Questions • Problems – Physical properties at lower mantle conditions – Phase transformations within lower mantle? 5.0 Density (g cm-3) – Homogeneous in composition, phase? 5.5 4.5 4.0 Pyrolite 100 Ma 3.5 0 1000 2000 Depth (km) 3000 Radial Structure of Pyrolitic Mantle – Role of anisotropy – Role of attenuation 4.6 4.4 Density (g cm-3) • Upper Mantle and Transition Zone • Shallow discontinuities • Local minimum • 410, 520,660 • High gradient zone at top of lower mantle • Questions 4.2 4.0 3.8 3.6 Pyrolite 100 Ma 3.4 3.2 0 200 400 600 Depth (km) 800 1000 Radial Structure of Pyrolitic Mantle • “Discontinuities” • Questions: 4.3 Density (g cm-3) – Structure as f(composition) – How well do we know phase equilibria? 4.4 4.2 4.1 4.0 3.9 3.8 600 620 640 660 Depth (km) 680 700 Origin of Mantle Heterogeneity Mantle Heterogeneity Temperature 350 C11 300 Elastic Modulus (GPa) • Most physical properties depend on temperature • Elastic constants mostly decrease with increasing T • Rate varies considerably with P, T, composition, phase • Few measurements, calculations at high P/T • Dynamics: thermal expansion drives 250 Anderson & Isaak (1995) 200 C44 150 100 C12 Periclase P=0 50 0 0 500 1000 Temperature (K) 1500 2000 Mantle Heterogeneity Phase Depth (km) 150 1.0 opx 300 450 600 750 Ca-pv C2/c cpx 0.8 Atomic Fraction • Mantle phase transformations are ubiquitous • Phase proportions depend on T: vary laterally • Different phases have different properties • Dynamics: heat, volume of transformation modifies gt il 0.6 pv 0.4 ol 0.2 wa ri Pyrolite Stacey Geotherm mw 0.0 5 10 15 20 Pressure (GPa) 25 30 Mantle Heterogeneity Composition • Physical properties depend on composition • Phase proportions depend on composition • Major element heterogeneity is dynamically active Origin of Lateral Heterogeneity Radioactivity Temperature Composition Differentiation Entropy Latent Heat Phase Chemical Potential