Understanding the Earth's Interior: A Perspective from Mineral Physics, Slides of Geochemistry

Download Understanding the Earth's Interior: A Perspective from Mineral Physics and more Slides Geochemistry in PDF only on Docsity!

Composition and Structure of

Earth’s Interior

A Perspective from Mineral

Physics

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)

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– P

bond

~eV/Å

3 =160 GPa~P

mantle

How does it respond?

-^

To changes in energy– Change in temperature

-^

Heat Capacity

C

, P

C

V

• Change in Density -^

Thermal expansivity,



• Phase Transformations -^

Gibbs Free Energy,

G

-^

Influence all responsesin general

How does it respond?

-^

To hydrostatic stress– Compression

-^

Bulk modulus,

K

, S K

T

• Adiabatic heating -^

Grüneisen parameter

-^

=

 K

/ S  c

P

• Phase Transformations -^

Gibbs Free Energy

-^

To deviatoric stress– Elastic deformation

-^

Elastic constants,

c

ijkl

• Flow -^

Viscosity,



ijkl

• Failure

How do we find out?

-^

How does interior differ fromlaboratory?– The significance of the differences

depends on the property to beprobed

-^

Equilibrium thermodynamicproperties– 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?

•^

Experiment

•^

Production of highpressure and/ortemperature

•^

Probing of sample insitu

1.08 1.07 1.06 1.05 1.04 1.03 1.02 1.01 1. 0 Relative Volume, V/V

2000

1600

1200

800

400

Temperature (K)

Forsterite0 GPa

Bouhifd et al.

(1996)

±0.1^0

q^ ±1^0

Pressure, Temperature,

Composition

-^

P/T themselves depend onmaterial properties

-^

Pressure: Self-gravitationmodified significantly bycompression

-^

Temperature: Self-compression, energy,momentum transport

-^

Composition– Heterogeneous– Crust/Mantle/Core– Within Mantle?

Pressure, Temperature,

Composition

Temperature

-^

Constraints: near surface– Heat flow– Magma source– Geothermobarometry

-^

Constraints: interior– Phase transformations– Grüneisen parameter– Physical properties

-^

Properties of Isentrope^ 

T

≈1000 K

• Verhoogen effect -^

Questions– Boundary layers?– Non-adiabaticity?

2800260024002200200018001600 Temperature (K)

3000

2000

1000

0

Depth (km)

Composition

-^

Constraints: extraterrestrial– Nucleosynthesis– Meteorites

-^

Constraints: near surface– Xenoliths– Magma source

-^

Constraints: Interior– Physical properties

-^

Fractionation important– Earth-hydrosphere-space– Crust-mantle-core

-^

Mantle homogeneousbecause well-mixed?– Not in trace elements– Major elements?

Pyrolite/Lherzolite/Peridotite/…

Radial Structure

•^

Influenced by– Pressure– Phase

transformation

• Temperature

6.5 6.0 5.5 5.0 4.5 4.0 3. )-1 Shear Wave Velocity (km s

600

400

200

0

Depth (km)

sp plg

ol wa

ri

opx

cpx

C2/c

gt^

mj

capv

pv akmw

Radial Structure of Pyrolitic

Mantle

-^

Lower mantle

-^

Questions– Homogeneous in

composition, phase?

-^

Problems– Physical properties at

lower mantle conditions

• Phase transformations

within lower mantle?

5.5 5.0 4.5 4.0 3. )-3 Density (g cm

3000

2000

1000

0

Depth (km)

Pyrolite100 Ma