Accretion and crustal evolution of continental margin terranes in the Appalachians of Eastern Canada: aprocess-oriented study

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We further concentrate on low-grade, low- to medium-pressure metamorphic rocks of predominantly mafic and felsic composition within collision zones of microplates along the eastern margin of Laurentia. The continuous accretion of these microplates mainly contributed to the growth of the North American continent during the early Palaeozoic. Our successful integrated and process-oriented approach using petrological and geochronological methods can now be finished within a considerably shortened prolongation period, because in the first period our methods were tested in detail, a huge data base was largely provided and worked out, and all our geochemical themes published. With the existing data base our main goal, to test tectonic models with petrological and geochronological data can be finished. Hence following existing models along three very different collison zones of microplates can substantially be modified and/or refined: (1) weak crustal thickening and dispersion of the colliding microplate succeeded the collision of the Avalonia terrane during the Devonian in northeastern Newfoundland; (2) along the Iapetus suture in central Newfoundland involving soft collision without high pressure metamorphism it can be demonstrated that predominant deformation, crustal thickening and metamorphism occurred substantial time after collision with decreasing intensity and due to large distance effects of further collisions; (3) along a complex collision zone along the Baie Vert Line in western Newfoundland which represents a hard collision with high pressure rocks in the lower plate, unusual late deformation with moderate crustal thickening in the upper plate can be observed and a transition of low-grade high pressure rocks from the lower to the upper plate.