The accretionary history of southern South America from the latest Proterozoic to the Late Palaeozoic: some palaeomagnetic constraints
The accretionary history of southern South America from the latest Proterozoic to the Late Palaeozoic: some palaeomagnetic constraints
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DOI：
10.1144/gsl.sp.2005.246.01.12
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发表时间：
2005
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影响因子：
--
通讯作者：
A. Rapalini
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文献类型：
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作者：
A. Rapalini
摘要 现在人们普遍认为，南美洲南部是由几个具有不同起源和演化的地体形成的。然而，增生过程的详细历史尚未解开。古地磁学可以在这一努力中发挥重要作用。综述和讨论了古地磁对该地区元古界和古生界构造演化的制约。来自拉普拉塔河克拉通的数据表明，到元古代末期，该地块已经附着在大多数主要的冈瓦纳地块上，并且可能与刚果-圣弗朗西斯科、西尼罗河和阿拉伯整个文迪亚地区形成了一个单一的大陆块。现有的古地磁数据支持在冈瓦纳大陆组装之前将这些克拉通与亚马逊和西非分隔开的大洋。拉普拉塔克拉通以西是潘皮亚地体。尽管缺乏古地磁数据，但地质证据支持这些块体之间早寒武世碰撞的模型。早奥陶世岩浆弧，即法马蒂纳-东普纳带，在已增生的潘皮亚地体的西缘上发育，显示出大顺时针旋转的系统模式，这被解释为整个地体的代表。受欢迎的构造模型描绘了一个大陆岩浆弧，其东部有一个弧后盆地，当地体旋转时该盆地关闭。鉴于证据的数量和多样性，包括古地磁学，毫无疑问 Cuyania (Precordillera) 地体的劳伦斯起源。增生的构造机制及其发生时间仍存在争议。来自库亚尼亚晚奥陶世岩石的新古地磁数据支持“劳伦西亚高原”假说，该假说表明库亚尼亚在奥陶纪仍与劳伦西亚存在着联系。尽管如此，这些新数据并不排除更普遍青睐的“微大陆模型”。库亚尼亚以西是智利地体，被一条晚奥陶世的蛇绿岩带隔开。尽管一些 U-Pb 年龄和 Nd 模型年龄表明其基底是劳伦斯起源，但人们对这个地体知之甚少。缺乏古地磁数据无法确定其运动演化。阿雷基帕-安托法拉地块实际上可能是一个复合地体。迄今为止获得的古地磁数据仅来自安托法利亚地块南部。最近在阿根廷普纳西部获得的数据证实了最初提出的早古生代古地磁极的分布，尽管存在一些不确定性，但它描绘了一种显着的逆时针旋转模式，并且晚寒武世的古纬度可能存在异常。数据表明，早古生代阿根廷东普纳和西普纳之间存在重大构造不连续性。来自北巴塔哥尼亚地块的泥盆纪至二叠纪时代的四个古地磁极在位置和年龄上与冈瓦纳大陆明显的极漂移路径一致，表明自泥盆纪以来，两个大陆块都没有经历过重大的相对位移。然而，这些数据并不排除巴塔哥尼亚在早古生代或中古生代与其北部边界正交的有限分离以及随后在晚古生代的碰撞。
Abstract It is now accepted that southern South America was formed from several terranes of diverse origin and evolution. However, a detailed history of the accretionary processes has not been unravelled yet. Palaeomagnetism can play an important role in such an endeavour. Palaeomagnetic constraints on the tectonic evolution of this region in the Proterozoic and Palaeozoic are reviewed and discussed. Data from the Rio de la Plata craton suggest that this block was already attached to most major Gondwana blocks by the end of the Proterozoic and may have formed a single continental mass with Congo-Sao Francisco, West Nile and Arabia throughout most of the Vendian. A large ocean separating these cratons from Amazonia and West Africa, prior to Gondwana assembly, is supported by available palaeomagnetic data. To the west of the Rio de la Plata craton is the Pampia terrane. Despite lack of palaeomagnetic data, geological evidence supports a model of Early Cambrian collision between these blocks. An Early Ordovician magmatic arc, the Famatina-Eastern Puna belt, which had developed on the western margin of the already accreted Pampia terrane, shows a systematic pattern of large clockwise rotation that has been interpreted as representative of the whole terrane. The favoured tectonic model portrays a continental magmatic arc with a back-arc basin to the east that was closed when the terrane rotated. There is little doubt of a Laurentian origin for the Cuyania (Precordillera) terrane, given the amount and diversity of evidence, including palaeomagnetism. The tectonic mechanism for accretion and its timing are still controversial. New palaeomagnetic data from Late Ordovician rocks of Cuyania support the ‘Laurentian plateau’ hypothesis, which suggests that Cuyania was still linked to Laurentia well into the Ordovician. Nevertheless, these new data do not rule out the more generally favoured ‘microcontinent model’. To the west of Cuyania is the Chilenia terrane, separated by a belt of ophiolites of Late Ordovician age. Very little is known about this terrane, although some U-Pb ages and Nd model ages point to a Laurentian origin for its basement. Lack of palaeomagnetic data precludes determining its kinematic evolution. The Arequipa-Antofalla block may actually be a composite terrane. Palaeomagnetic data obtained so far come exclusively from the southern Antofalla block. Recently acquired data in the western Puna of Argentina confirm the originally proposed distribution of Early Palaeozoic palaeomagnetic poles, which, despite several uncertainties, delineate a pattern of significant counterclockwise rotations with a possible anomaly in palaeolatitude for the late Cambrian. The data suggest a major tectonic discontinuity between the Eastern and Western Puna of Argentina in the Early Palaeozoic. Four palaeomagnetic poles of Devonian to Permian age from the North Patagonian Massif are consistent in position and age with the Gondwana apparent polar wander path, suggesting that both continental masses have not experienced major relative displacement since the Devonian. The data do not, however, rule out a restricted separation of Patagonia orthogonal to its northern boundary in the Early or Middle Palaeozoic and subsequent collision in the Late Palaeozoic.