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
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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DOI：
10.1016/j.jsames.2012.09.006
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发表时间：
2013
影响因子：
1.8
通讯作者：
V. Girardi;W. Teixeira;M. Mazzucchelli;P. C. C. D. Costa-P.-C.-C.-D.-Costa-145919449
中科院分区：
文献类型：
--
作者：
V. Girardi;W. Teixeira;M. Mazzucchelli;P. C. C. D. Costa-P.-C.-C.-D.-Costa-145919449
对南美洲地台东部基性岩体的研究表明，它们的地幔源区和地球动力学特征存在很大差异，特别是西南亚马逊和圣弗朗西斯科弗朗西斯科基性岩脉。西南亚马逊盆地的拉斑玄武岩，属于Serra da Providência侵入岩套（1.55 Ga），新Lacerda群（1.44 Ga），科罗拉多复合体（1.35 Ga）和新巴西兰迪亚群（1.10Ga），起源于主要由N-MORB端元组成的地幔源区，并有不同程度的板片流体加入（高达30%，根据所采用的模式）从海洋岩石圈由于幕式俯冲在中元古代。来自新拉塞尔达群和科罗拉多杂岩的基性岩侵入体与分隔亚马逊河流域和克拉通地体的大洋域在1.47-1.35 Ga闭合期间形成的弧环境有关，而来自塞拉达普罗维登西亚侵入岩套和新巴西兰迪亚群的拉斑玄武岩被认为是克拉通内的。弗朗西斯科岩墙群与板块内事件有关。推断组成的地幔源的Lavras群（1.9 Ga）有一个占主导地位的E-MORB签名，和适度的贡献高达10%的OIB组件。地幔成分在元古宙期间经历了相当大的变化，如较年轻的岩脉的来源所示，以迪亚曼蒂纳（0.93 Ga）和萨尔瓦多-奥利文萨岩群（0.92 Ga）为代表，其中加入了相当数量的板片衍生流体，可能来自回收的地壳物质和OIB组分。地幔成分和岩脉侵入的变化可能与Rodinia超大陆的初始分裂有关。佛罗里达（1.79 Ga）和坦迪尔（2.0 Ga）岩墙与拉普拉塔河的伸展事件有关。尽管这些群和Lavras（1.9 Ga）的构造框架之间的相似之处，古元古代地幔的组成都是非常不同的。佛罗里达岩脉的母地幔比其他岩脉更富集，也更不均匀，这可能是由于老结壳的再循环和OIB交代作用。Tandil岩脉的同位素数据也表明了一个富集的原始来源，这可能是古元古代Rio de拉普拉塔地幔的一个特征。Crixás-Goiás（2.49 Ga）群起源于一个非常不均匀的地幔源，可能受到OIB交代流体和地壳添加物的污染，这表明自太古代以来已经发生了地壳再循环。
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 São Francisco Cratons. The tholeiites from the SW Amazonian Craton, which belong to the Serra da Providência Intrusive Suite (1.55 Ga), the Nova Lacerda swarm (1.44 Ga), the Colorado Complex (1.35 Ga), and the Nova Brasilândia 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 Paraguá Terrane, whereas the tholeiites from the Serra da Providência Intrusive Suite and the Nova Brasilândia Group are considered intracratonic. The dike swarms of the São 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–Olivença 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 Crixás–Goiás (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.