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

我们进一步集中在低级，低至中压变质岩主要是镁铁质和长英质成分的碰撞带内的微板块沿着劳伦大陆东部边缘。这些微板块的不断增生是早古生代北美大陆生长的主要原因。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，我们的方法进行了详细的测试，大量的数据库被提供和制定，我们所有的地球化学主题出版。我们的主要目标是利用现有的数据库，完成岩石学和年代学数据对构造模型的检验。因此，可以对现有的沿着三个截然不同的微板块碰撞带的模式进行修正和/或改进：（1）纽芬兰东北部泥盆纪Avalonia Mélée碰撞后，地壳增厚和碰撞微板块分散较弱;（二）沿着纽芬兰中部的Iapetus缝合线，在没有高压变质作用的情况下，地壳增厚和变质作用发生在碰撞后相当长的时间内，强度逐渐减弱，这是由于进一步碰撞的远距离效应;（3）沿纽芬兰西部Baie Vert线的复杂碰撞带，代表与下板块高压岩石的硬碰撞，可以观察到异常的晚期变形，在上板块有适度的地壳增厚，低等级的高压岩石从下板块过渡到上板块。

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.