Dynamics and timing of metamorphic processes in exhumation channels at thecontinent-continent interface:comparative target areas in NW Newfoundland and W Argentina

在北美大陆东北边缘的阿巴拉契亚山脉北部，出现了四个不同地体(从北到南，达什伍德，甘德里亚，阿瓦洛尼亚，梅古马)的拼贴。在那里，大陆岩浆弧形成，随后从涉及的主要大陆板块(冈瓦那、劳伦西亚)分离(Abb.1；van Staal 2009；Zagorevski等人)。2010)。特别是在纽芬兰，这座拼贴画被一致地暴露出来，成为研究涉及微板的碰撞过程的优秀自然实验室。这些微板随后与劳伦西亚的边缘相撞。例如，达什伍德地体首先沿着奥多维西期的Baie Vert-Brompton Line(BVBL)附着到劳伦蒂亚。随后，达什伍德地体以南的更多微板块的增加导致了额外的变形和地壳增厚，即使在这个古老的碰撞带上也是如此。已经详细研究了这些微板块的结构和早期地质历史，包括碰撞带的结构(van Staal，2007；Zagorevski等人)。在被片麻岩包裹的BVBL榴辉岩体以西，发育中级高压变质岩。根据申请人的观点，这些岩石是在一条挖掘通道中挖掘出来的。在BVBL以东，暴露出上板块极低到低品位的岩石。关于高压岩石的变质条件和相应的年龄(Jamieson，1990；例如，Ar/Ar冷却年龄为429-375 Ma)，只有粗略的信息。在DFG项目框架内对这种高压岩石(见建议1.2)的研究证实了折返通道的想法，这对了解全球范围内的碰撞过程具有重要意义。更多的高压岩石将在应用的额外研究年内进行调查。

In the northern Appalachians at the NE margin of the N-American continent a collage of four different terranes (from north to south Dashwood, Ganderia, Avalonia, Meguma) occur. There, continental magmatic arcs evolved which were subsequently separated from the involved major continental plates (Gondwana, Laurentia) (Abb.1; van Staal 2009; Zagorevski et al. 2010). Especially in Newfoundland this collage is coherently exposed being an excellent natural laboratory to study collisional processes involving microplates. These microplates collided subsequently with the margin of Laurentia. For instance, the Dashwood terrane was firstly accreted to Laurentia along the Baie Vert-Brompton Line (BVBL) in the Ordovizian. The following accretion of further microplates south of the Dashwood terrane led to additional deformation and crustal thickening even at this old collisional zone. The structure and the early geological history of these microplates including the structure of the collisional zones had been already investigated in detail (van Staal 2007; Zagorevski et al. 2010).West of the BVBL eclogite bodies, which are enveloped by gneisses, and medium-grade high-pressure metapelites occur. According to the view of the applicant, these rocks were exhumed in an exhumation channel. East of the BVBL very low to low grade rocks of the upper plate are exposed. Only rough information exist on the metamorphic conditions and the corresponding ages of the high-pressure rocks (Jamieson, 1990; e.g. Ar/Ar cooling ages of 429-375 Ma). The study of such high-pressure rocks (see 1.2 of the proposal) in the frame of this DFG project has confirmed the idea of the exhumation channel, which is of major importance to understand collisional processes on a global scale. Additional high-pressure rocks will be investigated during the applied additional research year.