Abstract The first occurrence of Mesoproterozoic carbonatite in the Rio de la Plata Craton - RDPC indicates extensional event prior to the opening of the Charrua Ocean. Nd-Sr-Hf Isotopic and U-Pb on zircon geochronological data are presented for the Tres Estradas Alkaline-Carbonatite Complex - TEC, located in southernmost Brazil. The complex consists predominantly of ultramafic rocks, carbonatites and, subordinate, deformed fenitized syenites metamorphosed under greenschist to amphibolite facies conditions. U-Pb ages between 1,110±4.8 Ma and 1,123±15 Ma, respectively derived from a dolomite metacarbonatite and an associated metasyenite, constrain the TEC emplacement timing. The Nd-Sr-Hf isotopic signatures indicate that the TEC rocks were derived from a heterogeneous mantle, isotopically depleted in Sm-Nd and slightly depleted to enriched in Rb-Sr, with little influence of ancient crust and that these rocks are derived from the same source of parental magma probably submitted to intense metasomatism. The Nd-Sr isotopic signatures and crystallization ages of the TEC allow correlating it to the carbonatitic intrusions of the Alkaline provinces of Ontario and Grenville, Canada, in Laurentia, associated with the Keweenawan magmatic event (1.11-1.09 Ga), to which extension efforts would be related causing ruptures in RDPC edge and Laurentia, probably juxtaposed in that time interval. According to paleogeographic reconstructions of Rodinia, the Kalahari Craton would only have joined Laurentia and the RDPC at 1,050 Ma. Around 920 Ma there is the generation of an oceanic crust in the Rio de la Plata Craton with the installation of the Charrua Ocean and the beginning of the formation of the Dom Feliciano Belt, concluded at 540 Ma, with peak deformation and metamorphism at 650-630 Ma.

中文翻译：

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巴西中元古代 três estradas 碱性碳酸盐岩复合体的 Nd-sr-hf 同位素和 u-pb 年龄：对 sul-riograndense 盾构演化和罗丁尼亚分裂的影响

摘要 拉普拉塔河克拉通中元古代碳酸盐岩的首次出现- RDPC 表明查鲁阿洋开放之前的伸展事件。提供了位于巴西最南端的 Tres Estradas 碱性碳酸岩复合体 - TEC 的 Nd-Sr-Hf 同位素和 U-Pb 锆石年代学数据。该复合体主要由超镁铁质岩石、碳酸岩和次要的变形的非尼特化正长岩组成，这些正长岩在绿片岩到角闪岩相条件下变质。U-Pb 年龄介于 1,110±4.8 Ma 和 1,123±15 Ma 之间，分别来自偏碳酸白云岩和相关的偏正长岩，限制了 TEC 的就位时间。Nd-Sr-Hf 同位素特征表明 TEC 岩石来自异质地幔，同位素贫 Sm-Nd 和轻微贫富 Rb-Sr，受古代地壳的影响很小，而且这些岩石来自母岩浆的同一来源，可能经历了强烈的交代作用。TEC 的 Nd-Sr 同位素特征和结晶年龄允许将其与劳伦西亚安大略省和加拿大格伦维尔碱性省的碳酸盐岩侵入体相关联，与 Keweenawan 岩浆事件（1.11-1.09 Ga）相关，扩展努力将与导致 RDPC 边缘和劳伦蒂亚破裂有关，可能在那个时间间隔内并列。根据罗迪尼亚的古地理重建，喀拉哈里克拉通只会在 1,050 Ma 加入劳伦西亚和 RDPC。