1. Geochemical evidence for Archean plate tectonics in the 2. 7 to 3
Geochemical evidence for Archean plate tectonics in the 2.7 to 3.0 Ga Uchi Subprovince, northern Ontario
Pete Hollings
Lakehead University

2. The Uchi subprovince
Multiple assemblages ranging in age from 2.7 to 3.0 Ga
Younger assemblages formed on the margins of the ~3 Ga protocontinental North Caribou Terrane
Modified after Stott & Corfu (1991)

3. 2.9 to 3.0 Ga assemblages Komatiites Tholeiites
From Hollings et al. (1999). Lithos, 46,

4. 2.9 to 3.0 Ga assemblages Felsics
From Hollings et al. (1999). Lithos, 46, J ef
fer
son
Lak e
Bar
Gar go
yle
3 km N

5. ~2.7 Ga assemblages From Hollings & Kerrich (2000).
Contributions to Mineralogy and Petrology, 139,

6. Mantle Nb/Y vs Zr/Y arrays
Phanerozoic arcs plot along the MORB array
Archean Wawa basalts require a different source
P = slope of the Iceland plume
M = modern MORB array
Arc data from Gamble et al. (1994), Pearce et al. (1995), Elliot et al. (1997), Wyman (2003)
From Wyman & Hollings (2006)

7. Mantle Nb/Y vs Zr/Y arrays
From Wyman & Hollings (2006)

8. Mantle Nb/Y vs Zr/Y arrays
From Wyman & Hollings (2006)

9. Conclusions
Greater role for plumes from 2.9 to 3.0 Ga but still evidence of arc magmatism
Increasing evidence for Phanerozoic processes from 2.8 to 2.9 Ga
By 2.7 Ga plate tectonic processes similar to those of the Phanerozoic generate comparable suites of rocks