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首页> 外文期刊>Journal of geodynamics >The South Connemara Group reinterpreted: a subduction-accretion complex in the Caledonides of Galway Bay, western Ireland
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The South Connemara Group reinterpreted: a subduction-accretion complex in the Caledonides of Galway Bay, western Ireland

机译：南康尼马拉集团重新诠释：西爱尔兰戈尔韦湾喀里多尼德一个俯冲-增生复合体

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The Caledonian geology of western Ireland records the collision of two arc complexes with the Laur-entian Margin during the closure of the lapetus Ocean. An earlier complex collided with this hitherto passive margin in the mid-Ordovician during the Grampian Orogeny. Subsequently, arc magmatism developed along the Laurentian margin and continued until the late Silurian collision between Laurentian and Avalonia. The Ordovician volcanic and sedimentary rocks comprising the South Connemara Group lie along the Southern Uplands Fault, the terrane boundary separating these two arc complexes. Palaeon-tological dating indicates an Arenig-Llanvirn age for part of this complex (Williams, Armstrong and Harper, 1988), making it contemporaneous with the earlier arcs. However, most authors correlate this complex with the northern belt of the Southern Uplands (Morris, 1983; Williams, D.M., 1984. The stratigraphy and sedimentology of the Ordovician Party Group, south-eastern Murrisk, Ireland. Geological Journal, 19, 173-186; Williams et al., 1988), associated with post-Grampian subduction of north directed polarity. We present new field evidence that the South Connemara Group is tectonically disrupted by bedding parallel shear zones and that contacts previously interpreted as conformable are marked by units of tectonic melange. We present structural and provenance arguments consistent with the melanges forming above a north-dipping subduction zone after 463Ma. This Group is reinterpreted as occurring within a subduction-accretion complex that was generated by the accretion of early Ordovician mafic seamounts into a post-Grampian trench, thus reconciling the age of the Group with its generally accepted tectonic setting. We discuss the regional significance of this finding with respect to the Caledonide-Appalachian orogeny and argue that this is the site along which the lapetus Ocean closed.
机译：西爱尔兰的加里东地质学记录了在拉普拉特斯海洋封闭期间，两个弧形复合体与劳伦-恩蒂恩边缘的碰撞。在格兰屏造山运动中，一个早期的复合体在奥陶纪中期与这种迄今的被动边缘相撞。随后，沿洛伦山脉边缘发展成弧岩浆作用，一直持续到洛伦山脉和阿瓦隆山脉之间志留纪晚期碰撞为止。组成南康尼马拉群的奥陶纪火山岩和沉积岩沿南高地断裂，地界将这两个弧复合体隔开。古生物学定年表明该综合体的一部分处于Arenig-Llanvirn年龄（Williams，Armstrong和Harper，1988年），使其与早期的弧线同时存在。但是，大多数作者将此复杂地带与南部高地的北部带相关联（Morris，1983； Williams，DM，1984。爱尔兰东南部Murrisk的奥陶纪党组的地层和沉积学。GeologicalJournal，19，173- 186； Williams等，1988），与北格兰特后南格兰普俯冲作用有关。我们提供了新的野外证据，表明南康尼马拉群被层理平行的剪切带破坏了构造，并且先前被认为是顺应性的接触以构造混杂岩为标志。我们提出的构造和物源论证与463Ma之后北倾俯冲带上方形成的混杂岩一致。该组被重新解释为发生在俯冲-增生复合体内，该复合体是由早期奥陶纪镁铁质海山增生到后格兰屏海沟而产生的，因此使该组的年龄与其普遍接受的构造环境相协调。我们讨论了有关Caledonide-Appalachian造山作用的这一发现的区域意义，并认为这是Lapetus海洋关闭的地点。

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