Transcript Stratigraphy & geochemistry of the Nipigon basin

Geochemical evidence for Archean plate
tectonics in the 2.7 to 3.0 Ga Uchi Subprovince,
northern Ontario
Pete Hollings
Lakehead University
• 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)
The Uchi subprovince
2.9 to 3.0 Ga assemblages
Komatiites
Tholeiites
2.9 to 3.0 Ga assemblages
Felsics
N
Gargoyle
Lak e
Jefferson
Lak e
Bar
Lak e
3 km
~2.7 Ga assemblages
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)
Mantle Nb/Y vs Zr/Y arrays
Mantle Nb/Y vs Zr/Y arrays
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