1. We have been talking about minerals primarily in the earth’s crust
What About the rest??

4. Mantle composition (rheology)
Lherzolite (60%olv 40%OPX, grt)
Harzburgite (80%olv 20%OPX)
Pyrolite (lherzolite-like)
Olivine  b-spinel
Pyroxene 
b-spinel + stishovite
Spinel 
perovskite + periclase
lithosphere
asthenosphere
Upper
mantle
410
660
MOHO
dicontinuities
Lower mantle

5. Lherzolite (60%olv 40%OPX, grt) Harzburgite (80%olv 20%OPX)
Upper Mantle Minerals
Olivine (60%), Pyroxene (30%), Garnet (10%)
Rest is compositionally homogeneous
What’s different??
Lherzolite (60%olv 40%OPX, grt)
Harzburgite (80%olv 20%OPX)
Pyrolite (lherzolite-like)
Olivine  b-spinel
Pyroxene 
b-spinel + stishovite
Spinel 
perovskite + periclase
lithosphere
asthenosphere
Upper
mantle
410
660
MOHO
discontinuities
Lower mantle

6. Upper Mantle Olivine
Olivine – Thought to be about 10-12% Fe in upper mantle
At pressures around the 410-km discontinuity, Fo-rich olivine transforms to a ccp structure called wadsleyite.
Iron rich olivines do not undergo this transformation. At higher pressures, both the Fa-rich olivine and wadsleyite transform to a spinel structure, (Mg,Fe)2SiO4, called ringwoodite.
This occurs when the pressure forces the structure to become as closest-packed as it can get  in order to become more dense it must transform to a new phase.

7. Garnet, Pyroxene
As pressure increases  Pyroxene  Garnet (primarily pyrope)
Increases from 50 to 520 km
Past 520 km, Garnet Ca-perovskite
Past 720 km, more Mg rich Garnets begin to form Mg-perovskite

8. Lower Mantle Minerals
Perovskite ((Mg, Fe)SiO3, Magnesio-wüstite: ((Mg,Fe)O), and Stishovite (SiO2)
~80% Perovskite, ~20% Magnesio-wustite, minor stishovite (which doesn’t form if Mg or Fe are around)
At these high pressures, all Si is 6-coordinate (SiO6 subunits; Octahedral coordination)

9. Perovskite
(Mg, Fe)SiO3
As the major mineral in the lower mantle, possibly the most abundant earth material!

10. Do we have any Lower Mantle Minerals??NO
How do we know they are there?
METEORITES!?!?!?!
P-S waves tell us something about composition
Nuclear chemistry also tells us something about composition
EXPERIMENTS – simulate P-T  see what you get…

11. Core

12. Core Outer Core Inner Core
Liquid – made of Iron (Fe) and Nickel (Ni) (about 4%) and some S, Si, and O (enough to make the density less than Fe and Ni alone)
Movement of this liquid is responsible for earth’s magnetic field
Inner Core
Solid, Hexagonally-closest packed Fe and Ni

13. Geodynamo The inner core spins – what happens when a solid is spun
inside a liquid containing ions??
Generate an electromagnetic field!
The polarity of that field has flopped many times in earth’s history
Drag and heterogeneous convection of the lower mantle creates differential and random drag that affects the outer core, c
Model of a magnetic reversal taking ~1,000 years…

14. The electromagnetic field also protects the planet from solar sourced ionic particles (solar wind)
The geodynamo is additionally responsible for the position of magnetic north