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

我们进一步集中于劳伦西亚东部边缘微板块碰撞带内以镁铁质和长英质为主的低品位、低至中压变质岩。这些微板块的持续增长主要促进了北美大陆在早古生代的生长。我们使用岩石学和地质年代学方法的成功的综合和面向过程的方法现在可以在相当短的延长期内完成，因为在第一阶段，我们的方法经过了详细的测试，提供和编制了大量的数据库，我们所有的地球化学主题都发表了。有了现有的数据库，我们的主要目标是可以完成用岩石学和地质年代学数据检验构造模型。因此，沿着三个不同的微板块胶结带的现有模型可以进行实质性的修改和/或完善：(1)在纽芬兰东北部泥盆纪期间，碰撞微板的弱地壳增厚和分散成功了阿瓦隆地体的碰撞；(2)纽芬兰中部的Iaptus缝合带发生了软碰撞，没有高压变质作用，可以证明主要的变形、地壳增厚和变质作用发生在碰撞后相当长的时间内，强度降低，并由于进一步碰撞的大距离影响；(3)沿纽芬兰西部贝叶垂线与下盘高压岩石发生硬碰撞的复杂碰撞带，可观察到上板块异常晚期变形，地壳中等增厚，低品位高压岩石由下板块向上板块过渡。

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.