Earth Materials VI The Core (Li)

Transcription

1 CIDER 12 Deep Time Earth Materials I Introduction to Earth Materials (Hirschmann) Earth Materials II Exp. Studies Related to Early Earth Proc (Rubie) Earth Materials III The Mantle (Li) Tutorial IV: Equations of State (Li) Earth Materials IV Models of Core Formation in Terrestrial Planets (Rubie) Tutorial V: Molecular Dynamics (Caracas) Earth Materials V Transport Properties (Williams) Earth Materials VI The Core (Li) KITP, Santa Barbara CA July 16-28, 2012

2 Earth s Core P: GPa T: K x: Fe-Ni-L t: Core formation, IC age 1.6

3 Discover the Core Oldham 06 Lehmann 36 Chondrites Taenite & Kamacite. Fe-Ni Widmanstätten Pattern Mantle xenolith Birch 1952

4 Light Elements Play Key Roles in Core Dynamics Dziewonski and Anderson 81 PEPI Li and Fei 07 ToG Phase Diagram Density Velocity Anisotropy Partitioning McDonough & Sun 95 after Buffett 03 Science

5 Simulate Core Conditions in Laboratory

6 Simulate Core Conditions in Laboratory Mao-Bell Symmetric Hydrothermal Panoramic

7 Simulate Core Conditions in Laboratory Li and Fei, in press, ToG

8 Phase Diagram of Iron fcc hcp bcc Li and Fei, in press, ToG

9 Phase Diagram of Iron Li and Fei, in press, ToG

10 Phase Diagram of Iron Tateno et al. 10 Science

11 ICB Temperature and IC Growth T ( T/ P) S (Maxwell relation) = ( V/ S) P P Melting Adiabat (Chain) = ( V/ T) P / ( T/ S) P α P = [( V/V)/ T] P C P = [(T S)/ T] P ( T/ P) S = α P V T/C P ~ 0.3 K/km

12 ICB Temperature and IC Growth Melting gradient 10 K/ GPa K/km Li et al. in prep. Adiabatic gradient 0.3 K/km

13 Snowfall in Earth s Core Li et al. in prep. Zou et al. 08

14 Light Elements Influence Melting Temperature Li and Fei, in press, ToG

15 Match Seismic Profiles with Fe-Ni-L Composition Li & Fei 07 ToG Density deficits Density jump at ICB Density gradient

16 Match Seismic Profiles with Fe-Ni-L Composition Velocity difference Velocity gradient Birch s law slope

17 Matching Density Doesn t Provide Unique Solution Li and Fei, in press, ToG

18 Apply Lattice Vibration to Determine Sound Velocities Phonon Dispersion Curve

19 Apply Lattice Vibration to Determine Sound Velocities Phonon Density of States Vibrational Spectrum

20 Measure Sound Velocities Shock Compression Nuclear Resonant Scattering Front View Side View Duffy and Wang 1998, UHPM

21 Simultaneously Match Density and Sound Velocities Li and Fei, in press, ToG

22 Simultaneously Match Density and Sound Velocities Gao et al. 11 EPSL

23 Simultaneously Match Density and Sound Velocities Must be oxygen-poor! Huang et al. 11 Nature

24 IC Growth and Fe-L Binary Phase Diagrams Li and Fei, in press, ToG

25 Multi-Component Iron-Rich Systems Li and Fei, in press, ToG

26 Multi-Component Iron-Rich Systems Sakai et al. 06 GRL Takafuji et al. 05 GRL

27 Decipher Earth s History from IC anisotropy Ishii & Dziewonski 02 PNAS Vp anisotropy IMIC East-west dichotomy Vs anisotropy Sun and Song 08 EPSL

28 Account for Inner Core Anisotropy Mao et al. 98 Science Steinle-Neumann et al. 01 Nature Vocadlo et al. 09 EPSL Sha and Cohen 10 PR

29 Account for Inner Core Anisotropy Tateno et al. 10 Science Nikolussi et al. 08 SM Gao et al. 09 JSC

30 Decipher Earth s History from IC anisotropy Strain rate Thermal Chemical Stress Gubbins et al. 12 Nature Wookey & Helffrich 08 Nature Light element Deguen and Cardin 09 NG Monnereau et al. 10 Science Aubert 08 Nature

31 Probe Core Dynamics from Various Observations Mosaic Topography Mosaic Cao et al. 07 PNAS Zhang et al. 05 Science Krasnoshchekov et al. 05 Nature Walker & Walker 05 EoS Hayden and Watson 08 PNAS

32 Gain Insights from Planetary Cores Earth and Mercury Galileo Satellites Weber et al. 11 Science Margot et al. 07 Science

33 Conclusions and Outlook New data on Fe-L phase relation, EoS, PDoS and CMB/ICB partitioning add constraints on core s thermal-chemical state Iron adopts hcp structure under IC conditions Core oxygen content limited Snowfall near ICB? High thermal conductivity calls for major revisions in thermal evolution model Large uncertainties in MP data at core pressures Insufficient data to determine composition of cores, esp. L and K Large uncertainties on ICB temperature and core T m gradient Partitioning not well understood New approaches may shed light on core composition and evolution Geoneutrino (U) Stable isotope (Si, Fe)