Download ppt - Pete Hollings Lakehead University

Geochemical evidence for Archean plate tectonics in the 2.7 to 3.0 Ga Uchi

Subprovince, northern Ontario

Pete HollingsLakehead University

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)

2.9 to 3.0 Ga assemblages

From Hollings et al. (1999). Lithos, 46, 137-161

Komatiites

Tholeiites

2.9 to 3.0 Ga assemblages

From Hollings et al.

(1999). Lithos, 46, 137-

161

Jefferson Lake

Bar Lake

Gargoyle Lake

3 km

N

Felsics

~2.7 Ga assemblages

From Hollings & Kerrich (2000). Contributions to Mineralogy and Petrology, 139, 208-226

Mantle Nb/Y vs Zr/Y arrays

• Phanerozoic arcs plot along the MORB array

• Archean Wawa basalts require a different source

From Wyman & Hollings (2006)

• 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)





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