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首页> 外文期刊>Geological Magazine >Brittle fault evolution of the Montreal area (St Lawrence Lowlands, Canada): rift-related structural inheritance and tectonism approached by palaeostress analysis
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Brittle fault evolution of the Montreal area (St Lawrence Lowlands, Canada): rift-related structural inheritance and tectonism approached by palaeostress analysis

机译：蒙特利尔地区（加拿大圣劳伦斯低地）的脆性断层演化：古地应力分析探讨与裂谷有关的构造遗传和构造

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The Montreal area belongs to the St Lawrence Lowlands, a Cambrian Early Ordovician passive margin of the Iapetus Ocean, later covered by Appalachian Middle to Upper Ordovician foreland deposits. A structural and palaeostress analysis has been carried out in order to reconstruct its tectonic evolution. The structural map has been revised with new data. Palaeostresses are reconstructed based on inversion of fault slip data, and these results are independently corroborated by the microstructural study of calcite mechanical twinning. Field relationships are used to establish the relative chronology of fractures and to deduce the motion on regional faults. The reconstructed structural and tectonic evolution brings to light some relationships between structural inheritance and tectonic events that have affected the area since Early Paleozoic times. An early NW-Se extension is responsible for N040-trending faults along the northern border of the St Lawrence Lowlands, and for N090-and N120-trending faults cross-cutting the Montreal area. This extension is followed by WNW-ESE and NNW compression, which have induced reverse motion on pre-existing faults and generated strike-slip conjugate faults. Subsequent NE-SW and NNW-SSE-directed extensions have reactivated previous faults with normal to strike-slip motions. A late NE-SW compression is recorded in the Monteregian pluton. Compress ions in WNW-ESE and NNW directions are consistent with Appalachian collision tectonism, but N040-and N090-trending faults cross-cut Appalachian folds and foreland deposits. Although the early NW-SE extension is consistent with the collapse of the Iapetan margin in Early Palaeozoic times, most of the present geometry of the St Lawrence Lowland could be attributed to Mesozoic tectonism, recorded as nearly N-S-directed extensional events.
机译：蒙特利尔地区属于圣劳伦斯低地，这是伊帕特斯海洋的寒武纪早期奥陶纪被动边缘，后来被阿巴拉契亚中奥陶纪前陆沉积物所覆盖。为了重建构造演化，已经进行了结构和古应力分析。结构图已使用新数据进行了修订。基于断层滑动数据的反演重建古应力，方解石机械孪晶的微观结构研究独立地证实了这些结果。场关系用于建立裂缝的相对年代，并推论区域断层的运动。自古生代以来，重建的构造和构造演化揭示了结构继承与影响该地区的构造事件之间的某些关系。 NW-Se的早期延伸是沿着圣劳伦斯低地北部边界的N040断裂，以及横穿蒙特利尔地区的N090和N120断裂。此扩展之后是WNW-ESE和NNW压缩，它们在已存在的断层上引起了反向运动并生成了走滑共轭断层。随后的NE-SW和NNW-SSE导向的扩展重新激活了以前的断层，并具有正常的走滑运动。蒙特利安岩体中记录了晚期NE-SW压缩。 WNW-ESE和NNW方向上的压缩离子与阿巴拉契亚碰撞构造一致，但N040和N090趋势断层横切了阿巴拉契亚褶皱和前陆沉积物。尽管早期的西北-东南伸展与古生代早期伊帕坦边缘的塌陷相一致，但圣劳伦斯低地目前的大多数几何形态都可归因于中生代构造运动，记录为近北-南向伸展事件。

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