Exsolution in Iron Meteorites

1
Exsolution in Iron Meteorites

• Bands of kamacite (Fe-Ni metal low in Ni) formed
  by exsolution in taenite, Fe-Ni higher in Ni.
• The two phases have different crystal structures.
• Kamacite exsolved along octahedral planes in
  taenite.

IVA Iron Meteorite, Gibeon
Photo by Jeffrey Gillis-Davis, U. of Hawaii
2
Cooling Rates
Iron-Nickel Phase Diagram
Growth of Kamacite
3
Cooling Rates
Matching the measured profile with calculated
profiles indicates that the cooling rate of this
sample is 1000 K/My.
In total, iron meteorite cooling rates range from
about 1 to almost 10,000 K/My