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首页> 外文期刊>Journal of South American earth sciences >Sr-Nd constraints and trace-elements geochemistry of selected Paleo and Mesoproterozoic mafic dikes and related intrusions from the South American Platform: Insights into their mantle sources and geodynamic implications
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Sr-Nd constraints and trace-elements geochemistry of selected Paleo and Mesoproterozoic mafic dikes and related intrusions from the South American Platform: Insights into their mantle sources and geodynamic implications

机译：南美平台中部分古生代和中生代铁镁质堤坝的Sr-Nd约束和痕量元素地球化学及相关侵入：地幔来源及其地球动力学意义的见解

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The study of selected mafic intrusions from cratonic areas of the South American Platform shows considerable differences among their mantle sources and geodynamic features, particularly regarding the dikes from the SW Amazonian and Sao Francisco Cratons. The tholeiites from the SW Amazonian Craton, which belong to the Serra da Providencia Intrusive Suite (1.55 Ga), the Nova Lacerda swarm (1.44 Ga), the Colorado Complex (1.35 Ga), and the Nova Brasilandia Group (1.10 Ga), originated from a mantle source composed mainly of a N-MORB end-member, with a variable addition of slab fluids (up to 30%, according to the adopted model) from oceanic lithosphere due to episodic subductions during the Mesoproterozoic. Mafic intrusions from Nova Lacerda swarm and Colorado Complex are related to arc settings formed during the 1.47-1.35 Ga closure of the oceanic domain separating the Amazonian Craton and the Paragua Terrane, whereas the tholeiites from the Serra da Providencia Intrusive Suite and the Nova Brasilandia Group are considered intracratonic. The dike swarms of the Sao Francisco Craton are associated with intra-plate events. The inferred composition of the mantle source of the Lavras swarm (1.9 Ga) has a predominant E-MORB signature, and a modest contribution of up to 10% of an OIB component. The mantle composition underwent considerable changes during the Proterozoic, as indicated by the sources of the younger dikes, represented by the Diamantina (0.93 Ga) and the Salvador -Olivenga swarms (0.92 Ga), to which considerable amount of slab derived fluids, probably from recycled crustal material, and OIB component were added. Changes in mantle composition and dikes intrusions could be related to the initial disruption of the Rodinia Supercontinent. The Florida (1.79 Ga) and Tandil (2.0 Ga) dikes are associated with extensional events of the Rio de La Plata Craton. In spite of the similarities between the tectonic framework of these swarms and that of Lavras (1.9 Ga), the composition of the Paleoproterozoic mantle of both cratons is very different. The parent mantle of the Florida dikes is more enriched and more heterogeneous than the others, probably due to the recycling of old crusts and OIB metasomatism. Isotopic data from the Tandil dikes also suggest an enriched original source, which could be a characteristic feature of the mantle of the Rio de La Plata Craton in Paleoproterozoic times. The Crixas-Goias (2.49 Ga) swarm originated from a very heterogeneous mantle source, probably contaminated by OIB metasomatic fluids and crustal addition, suggesting that crustal recycling has occurred since Archean times.
机译：对南美平台克拉通地区精选的镁铁质侵入岩的研究表明，它们的地幔来源和地球动力学特征之间存在相当大的差异，特别是在西南亚亚马逊河和圣弗朗西斯科克拉通斯的堤防方面。来自西南亚亚马逊克拉通的黄hole石起源于Serra da Providencia侵入套件（1.55 Ga），Nova Lacerda群（1.44 Ga），Colorado Complex（1.35 Ga）和Nova Brasilandia Group（1.10 Ga）。地幔源主要由N-MORB端部组成，并由于中元古生代间的俯冲作用而从海洋岩石圈中可变地添加了平板流体（根据所采用的模型，高达30％）。来自Nova Lacerda群和Colorado Complex的黑手党入侵与在1.47-1.35 Ga封闭亚马孙克拉通和巴拉圭地带的海洋领域形成的弧形环境有关，而来自Serra da Providencia入侵套件和Nova Brasilandia组的黄hole石被认为是克拉通内的。圣弗朗西斯科·克拉顿的堤防群与板内事件有关。推断的拉夫拉斯群（1.9 Ga）地幔源组成具有主要的E-MORB标记，并且贡献的OIB成分不超过10％。地幔组成在元古代期间发生了很大的变化，如年轻的堤防的来源所表明的那样，以Diamantina（0.93 Ga）和Salvador -Olivenga群（0.92 Ga）为代表，大量的板坯衍生流体，可能来自添加了回收的地壳材料和OIB组分。地幔组成的变化和堤防的入侵可能与罗迪尼亚超大陆的初始破坏有关。佛罗里达堤防（1.79 Ga）和坦迪尔（2.0 Ga）堤防与拉普拉塔克拉通河的伸展事件有关。尽管这些群的构造框架与拉夫拉斯（1.9 Ga）的构造框架相似，但两个克拉通的古元古代地幔的组成都非常不同。佛罗里达堤防的母体比其他堤防更富集和更异质，可能是由于旧地壳的再循环和OIB交代作用所致。来自坦迪尔堤防的同位素数据也表明了丰富的原始资料，这可能是古元古代的里约热内卢拉普拉塔克拉通地幔的特征。 Crixas-Goias（2.49 Ga）群起源于一个非常不同的地幔源，可能被OIB交代流体和地壳添加物污染了，这表明自古宙时代以来就发生了地壳再循环。

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