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Abstract

The dominant elements of structural style in the Canadian Cordillera are related to the Insular, Coast, Intermontane, Omineca, and Foreland morphogeological belts, of which the Coast and Omineca belts represent greatly uplifted granitic and metamorphic orogenic core zones. Structures commonly verge outward from the core zones so that, in cross-section, the Cordilleran orogen contains two symmetrical suborogens (Fig. 17.1, in pocket). The first to develop was the Omineca Belt wherein Mesozoic deformation is attributed to the collision of the Intermontane Superterrane with ancestral North America. Orogenesis in the Coast Belt is attributed to the long-lived development of a volcanic-plutonic arc perhaps coupled with collision of the Insular and Intermontane superterranes beginning in Jurassic time. Subsequent dextral strike-slip faulting greatly modified the distribution of components of the amalgamated terranes.

Mesozoic and Cenozoic structures in the Insular Belt comprise two main elements: 1) contractional, subduction or accretion related faults and folds in the Saint Elias Mountains and Vancouver Island and 2) dextral strikeslip faults and transpressive folds in the Queen Charlotte Islands. In the Saint Elias Mountains contractional structures are cut by Late Jurassic and Early Cretaceous plutons, and, in the southern Insular Belt, both extension and contraction structures are associated with hypabyssal, felsic dykes, sills and small plutons. On Vancouver Island northwest-trending anticlinoria and northerly trending Early and Middle Jurassic plutons dominate the structural grain; on the Queen Charlotte Islands, similar plutons are of Late Jurassic age.

The structurally symmetrical Coast Belt consists of a western part with westward verging

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