Electronic Thesis and Dissertation Repository

Thesis Format

Monograph

Degree

Master of Science

Program

Geology

Supervisor

Jiang, Dazhi

2nd Supervisor

Moser, Desmond

Joint Supervisor

Abstract

Zircon strain chronometry can allow correlation of isotopic ages with microstructural fabrics to place an absolute age on the timing of deformation. However, the general applicability of zircon strain chronometry to problems in regional continental tectonics is still being tested and this study is the first effort to apply the approach to the ~1 Ga (billion year old) Grenville Province of the Precambrian Canadian Shield. Samples were analyzed from the 1747 +6/-5 Ma Wanapitei Complex, a poly-deformed mafic metaplutonic body that preserves fabric evidence for several stages in the tectonic history of the Grenville Front. This study is the first to combine in situ strain measurements of zircon with independent measurements of past differential stress using quartz grain size piezometry. Zircon grains in Wanapitei Complex samples exhibiting the latest, D3, ductile deformation were analyzed using electron backscatter diffraction whereas grain size piezometry was completed on a cross-cutting dyke and a marginal gneiss. It was determined that the stress conditions in the Grenville Front near the Wanapitei Complex were not sufficient to deform the generally small (< 50 microns) zircon grains seen in thin sections and result in discordance that would date deformation. Future work targeting significantly larger zircon grains as well as other accessory phases such as baddeleyite and monazite would more thoroughly test the viability of U-Pb strain chronometry in the Grenville Front region.

Summary for Lay Audience

The Grenville Front is an area of complex deformation near Sudbury, Ontario resultant from events that occurred around 1 billion years ago. This thesis explores whether it is possible to date this deformation with increased confidence than previous work. The method examined in this thesis is zircon strain chronometry. Zircon strain chronometry is an underexamined method whereby plastically deformed zircons can be used to provide ages to the events in which the zircons were deformed. It was determined through this study that the conditions of deformation in the Grenville Front were not sufficient to cause zircon strain and therefore zircon strain chronometry is not an applicable method in this case. Justifications for these findings and suggestions for further work are provided.

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