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Lecture 3

Lecture 3.docx


Department
Earth and Environmental Sciences
Course Code
EARTH 108
Professor
Jie Li
Lecture
3

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Lecture 3
Early solar system processes
1. Condensation:
a. Cooling below melting temp.
b. Silicate and metal dust; ice
2. Accretion
a. Small scale: clinging dust particles
b. Large scale: asteroid impacts
3. Differentiation
a. Ex: separation of iron to form metal core
4. Fractionation
Meteorites: classification
oBy composition
Iron: mostly Fe w/ some Ni, S
Stony
Stony-iron
oBy origin
Primitive
Differentiated
Separation of Fe and silicates
Meteorites: age dating
oUses predictable decay of radiogenic elements
Change in ration btwn mother and daughter isotopes
Half life
oUseful isotope systems for geology:
U, Th, K
Half life of ~ billion yrs
Not: C-14
Half life of 6,000 yrs
Primitive meteorites (chondites)
oAge: 4.5 +/- 0.05 Byr
oChondrules
Oldest ‘rock’
4.567 Byr old
ocomposition of most chondrites:
10-30% Fe
Si, O, Mg, S
oCarbonaceous chondrities:
Very little Fe
Water and organic compounds
Differentiated meteorites (achondrites)
oIrons
Often w/ crystal pattern (Widmanstaetten)
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