The Rio Apa Block, a crustal fragment of 20,000 km2 in the southern portion of the Amazonian Craton, is a Paleoproterozoic terrain, making up the basement of the Neoproterozoic Paraguay Belt. The block is not often considered in the evolution models of the Columbia supercontinent. Different hypotheses of the evolution of the Rio Apa Block consider this segment as part of the Amazonian Craton, and its correlation with other Paleoproterozoic accretionary systems remains controversial. We present new U-Pb and Sm-Nd data that suggest that the Rio Apa Block constitutes a continental arc system built around 1.8–1.7 Ga that can be a correlation element in supercontinent models. Recorded orogenic accretionary events and continental crust reworking divide the block into three main sectors. The western and central sectors comprise parts of the 1.88–1.71 Ga Amoguijá arc. The eastern sector consists of Orosirian high-K calc-alkaline and postcollisional A-type granites. The western segment comprises Orosirian banded orthogneisses of the Porto Murtinho Complex, intruded by initial phase granitoids of the Amoguijá arc. The central sector is characterized by weakly to moderately deformed granites of the Amoguijá Suite, Serra da Bocaina Formation metavolcanic rocks, Serra da Alegria gabbro-anorthosite suite, and Morro do Triunfo gabbro, overlain by the Amolar Group sedimentary rocks. The eastern segment comprises the backarc basin generated Alto Tererê Group, intruded by late to postorogenic granites of the Rio Apa Complex, including A-type granites. Mafic dikes and sill swarms related to a late extensional event intrude the preceding rocks. Two important metamorphic-deformational events are recorded in the opening of the Rb-Sr system in biotite around 1670 Ma, followed by thrust deformation and metamorphism probably related to the ca. 1300 Ma Rondonian-San Ignácio event, as indicated by Ar-Ar muscovite and U-Pb monazite ages.

中文翻译：

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Rio Apa 地块：西南亚马逊克拉通的幼年地壳碎片及其对哥伦比亚超大陆重建的影响

Rio Apa 地块是亚马逊克拉通南部 20,000 平方公里的地壳碎片，是古元古代地形，构成新元古代巴拉圭带的基底。哥伦比亚超大陆的演化模型中并不经常考虑该区块。Rio Apa 地块演化的不同假设认为该段是亚马逊克拉通的一部分，它与其他古元古代增生系统的相关性仍然存在争议。我们提出了新的 U-Pb 和 Sm-Nd 数据，表明 Rio Apa 地块构成了一个建立在 1.8-1.7 Ga 附近的大陆弧系统，可以作为超大陆模型中的相关元素。记录的造山增生事件和大陆地壳改造将地块分为三个主要部分。西部和中部包括 1.88-1 的部分。71 Ga Amoguijá 弧线。东段由奥罗斯纪高钾钙碱性花岗岩和碰撞后 A 型花岗岩组成。西段包括 Porto Murtinho 杂岩的 Orosirian 带状正片麻岩，被 Amoguijá 弧的初始阶段花岗岩侵入。中部地区的特征是 Amoguijá 组、Serra da Bocaina 组变质火山岩、Serra da Alegria 辉长岩-斜长岩组和 Morro do Triunfo 辉长岩的弱至中度变形花岗岩，被 Amolar 组沉积岩覆盖。东段包括弧后盆地产生的 Alto Tererê 群，被 Rio Apa 杂岩体的晚生花岗岩侵入，包括 A 型花岗岩。与晚期伸展事件相关的基性岩脉和窗台群侵入了前面的岩石。在 1670 Ma 左右黑云母中 Rb-Sr 系统的开口中记录了两个重要的变质变形事件，其次是可能与大约 1670 Ma 相关的逆冲变形和变质作用。1300 Ma Rondonian-San Ignácio 事件，如 Ar-Ar 白云母和 U-Pb 独居石年龄所示。