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An application of Nd isotope mapping in structural geology: delineating an allochthonous Grenvillian terrane at North Bay, Ontario

Published online by Cambridge University Press:  08 October 2003

A. P. DICKIN
Affiliation:
School of Geography and Geology, McMaster University, Hamilton, Ontario L8S 4M1, Canada
R. H. MCNUTT
Affiliation:
Department of Geology, University of Toronto at Mississauga, Mississauga, Ontario L5L 1C6, Canada
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Abstract

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Fifty new Nd isotope analyses are presented from the North Bay area of the Grenville Province in Ontario. These data are used to map the extent of an allochthonous Grenvillian terrane which is an outlier of the Allochthonous Polycyclic Belt of the Grenville Province. Amphibolite facies orthogneisses from the allochthonous terrane have depleted mantle Nd model ages (TDM) below 1.8 Ga, whereas the gneisses of the structurally underlying parautochthon almost invariably have model ages above 1.8 Ga. The distribution of model ages is consistent with the distribution of distinct types of metabasic rock, used by other researchers as the criterion for recognizing rocks of the allochthonous and parautochthonous belts of the Grenville Province. The agreement between these different types of evidence demonstrates that Nd isotope mapping is a reliable and powerful tool for mapping terrane boundaries in high-grade metamorphic belts.

Type
Research Article
Copyright
© 2003 Cambridge University Press