1. The mass of continental crust has not changed
significantly since the early Archean

5. The mass of continental crust has not changed
significantly since the early Archean

6. Formation of continental crust
Differenciation of primitive mantle
Enriched continental crust
Undifferenciated
primitive mantle
Proto-Archean
Depleted mantle
Formation of the bulk of the continental crust in the Proto-Archean
Proto-Archean depleted mantle

7. Geochemical evidence Nb/U Both incompatible elements
U more incompatible than Nb
Differenciation  higher Nb/U in continental crust
lower Nb/U in depleted mantle
Primitive mantle
Nb/U ~30
Continental crust
Nb/U ~10
Modern MORB
Nb/U ~47
Archean basalts
Nb/U ~

8. Late Archean basalts Lunnon Formation Yilgarn Craton
Crustal contamination curve
 Depleted mantle source
 Amount of continental crust extracted
is the same as today
Sylvester et al. (1997)

9. 3.5 Ga basalts and komatiites
Barberton Montain Land, South Africa
Average Nb/U : 43
Suggest an early depleted mantle and and amount of continental crust extracted similar as today
Campbell (2003)

10. 3.5 Ga Basalts from Pilbara Craton
Sylvester ()

11. ? Isotopic evidence Depleted mantle at 3.8 Ga Isua 3.8 Ga
Porpoise Cove 3.8 Ga
Isua 3.8 Ga
Depleted mantle at 3.8 Ga

12. Recycling
McCulloch and Bennett (1994)