Electronic Thesis and Dissertation Repository

Degree

Doctor of Philosophy

Program

Geology

Supervisor

Dazhi Jiang

Abstract

The Grenville Front Tectonic Zone (GFTZ) is a polyphase deformation belt in the northwest of the Grenville Province which was shaped in the continent-continent-collision-induced Grenvillian Orogeny.

This thesis focuses on the evolution of deformation fabrics in the GFTZ between the Sudbury Basin and French River in Ontario, Canada. Geological mapping using a new digital mapping system was conducted within this segment of the GFTZ, in its northwest vicinity in the Southern Province, and in its southeast vicinity in the Grenville Province. The new digital mapping system includes a personal digital assistant equipped with an internal GPS and a mobile GIS mapping software, and the ArcGIS software, which together worked seamlessly in the whole mapping process. Mapping in Whitefish Falls in the Southern Province enables us to identify two generations of folds in the Gowganda Formation of the Huronian Supergroup. The first generation is explained by bedding-parallel shear perhaps in a fold-and-thrust belt system in the Penokean Orogeny between 1850 and 1830 Ma. The second generation folds are km-to-tens-of-km-scale folds which compose the fold belt of the Penokean Orogeny. Mapping in the Grenville Province allows us to establish three phases of deformation which correspond respectively to a mid- to lower crustal sub-horizontal flow in a thickened crust, a regional folding during the NW-SE lithosphere extension, and a NW-SE crustal shortening and top-to-the-NW thrusting. The GFTZ underwent all three phases of deformation. Regional structural correlation and zircon dating suggest that the three phases of deformation occurred during 1079-1030 Ma, 1028-1018 Ma, and 1000-953 Ma respectively. Mylonite zones were developed at the NW margin of the GFTZ. Detailed structural analysis of deformation fabrics within and in the vicinity of the mylonite zones south of Coniston, Ontario, Canada shows that these mylonite zones were developed in the third deformation phase accompanying the development of at least one generation of folds in the GFTZ. Although kinematics of many mylonite zones has been “quantified” by various vorticity analysis methods in the literature, none of these methods is adopted here. Numerical modeling was used to investigate these methods, and it was found that current vorticity analysis methods have uncertainties too large for them to be useful.


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