Tectonothermal Evolution of the Cadomian Orogen in the North Armorican Massif and Circum-Atlantic Correlations

北美洲地块是早古生代与北美洲、波罗的海和冈瓦纳分离的美洲板块的一部分。阿莫里卡的大部分地区受晚前寒武纪卡多米期造山运动的影响，该地块是少数在晚古生代瓦里斯坎造山运动中没有明显卡多米期古岩石叠加的地区之一。因此，该地区对于解决与相关的阿瓦洛纪和/或泛非层序的构造联系至关重要。尽管最近的野外工作表明，卡多米期造山活动发生了复杂的多期前寒武纪变质/构造事件，但现有模型的地球化学数据库有限。本研究将与在该地区工作的英国野外地质学家合作，对地块内具有代表性的岩性单元的40Ar/39Ar矿物年龄和选定的U-Pb锆石年龄进行系统测定。已安排与法国当地地质学家合作。这项研究的结果将允许对前寒武纪构造热事件进行详细的评估，并将有助于限制该地区的构造模型。

The North Armorican Massif is part of the Armorican Plate that separated from N. America, Baltica and Gondwana in the early Paleozoic. Large segments of Armorica were affected by the late Precambrian Cadomian orogeny, and the massif is one of very few areas where there is no apparent overprinting of Cadomian aged rocks during the late Paleozoic Variscan orogeny. This area is thus critical for resolution of tectonic linkages with correlative Avalonian and/or Pan-African sequences. Existing models for the Cadomian orogeny have a limited geochemical data base, although recent field work has shown that complex polyphase Precambrian metamorphic/structural events occurred. This study will make systematic determination of 40Ar/39Ar mineral ages and selected U-Pb zircon ages from representative lithological units within the massif, and will be conducted in collaboration with British field geologists working in the area. Co-operation with local French geologists has been arranged. The results of this research will permit detailed evaluation of Precambrian tectonothermal events and will help constrain tectonic models for the region.