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Crustal-scale Deformation and Late Archean Terrane Suturing Keith Benn University of Ottawa kbenn@uottawa.ca Southeastern Superior Province Canada
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Conclusions 1.2.7 Ga plate tectonics required to explain a documented terrane boundary 2.Probable accretion of oceanic LIP to margin of older crustal block 3.There is a very specific structural signature in the suture and in the accreted plateau 4.The structural signature is best explained by a crustal strength profile including a stiff lower crust, probably mafic granulites
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SE Superior Province
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SE Superior Province: Geology > 3000 Ma rocks below Pontiac (Carignan et al., Chem Geol, 1993)
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Tectonic delamination
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Tectonic delamination: why ? Geothermal gradient calculated incorporating crustal heat production (Sandiford et al., 2004; Afonso and Ranalli, 2004)
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Magmatic modification NS
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Two of the Tonalite Suites 2723 Ma 2713 Ma
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Synmagmatic tectonic deformation of ca 2696 Ma Granodiorite Granodiorite 2700 Ma to 2696 Ma
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Differing granitoid chemistry Provided by J.-F. Moyen
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Remelting of diorites
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Testing the model Positively identify surrounding terrane boundaries Crustal rheological profile –Strong lower crust (shear zones, faults) to be verified in the Kapuskasing zone Modified oceanic LIP –Detailed petrology / geochemistry of granitoids Define limits and nature of the old terrane
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Buy. This. Book. Geophysical Monograph Series, Volume 164, 370 pages, 2005, AGU Member Price - $ 62.30
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