22strcpr

Structural Provinces

         Structural Provinces are material units of continental crust that carry a penetrative deformation fabric of a specific age. The age assigned to the Province is therefore that of the orogenic event that caused the deformation rather than the age of the rocks themselves. Where rocks bear the imprint of several deformation events (polyphase deformation), the age of the youngest event defines the age of the Province.
        The oldest structural provinces of the Canadian Shield are the Slave and Superior provinces (c. 2.7 Ga), and the youngest is the still active Cordilleran system. Structural Provinces of Early Paleozoic age include the Appalachian and Innuitian provinces marking the eastern and northern margins of the North American continent.
        Structural provinces may themselves be composed of a collage of ‘terranes’, each terrane representing an independently evolved oceanic (e.g. arc) or continental (margin; microcontinent) unit that has migrated into its present position perhaps quite far from its ‘birth’ location. The Cordilleran Province provides a good example of such a collage (Cordilleran Suspect terranes). Similarly, the Grenville Structural Province (Tectonic map of the western Grenville Province Arc ocean systems) is thought to be an accreted collage of Proterozoic arcs and successor basins that has collided with the southern margin of the Superior Province and its cover of passive margin rocks forming the Southern Province. The Grenville Province is highly deformed, metamorphosed, and injected by igneous rocks, and its plate tectonic history is therefore not easily interpreted. Nevertheless, it is not unreasonable that terranes such as the Parry Sound and Elzevir domains represent allochthonous or parallochthonous Meso-Proterozoic island arcs,
        The Precambrian structural province that most closely represents a two- sided collisional plate tectonic system is the early Proterozoic Churchill Structural Province. (The Churchill Structural Province) The Archean rocks forming the northwest margin of the early Proterozoic Churchill ocean appear to be more extensively deformed than those of the Superior margin, and in this respect the Churchill Structural Province bears a marked resemblance to the Himalayan-Tibetan collisional system, with however far more of the oceanic component preserved in the Churchill Province.

Overheads
Structural trends in the Canadian Shield
Cordilleran Suspect terranes
Tectonic map of the western Grenville Province Arc ocean systems
(Structural Provinces) of the Canadian Shield (14strprv.gif)
Tectonic units of the Canadian Shield of Manitoba and Saskatchewan.

FIGURES

Structural Provinces of North America.

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