Abstract The basement of the northern Brasilia Belt, in Central Brazil, is dominated by large volumes of TTG magmatism generated during the Early Paleoproterozoic, and represents a continental block formed prior to the welding of the Sao Francisco paleocontinent during the Rhyacian, holding important information concerning the mechanisms and products of Paleoproterozoic crustal growth and amalgamation. New U-Pb zircon geochronological data was obtained from metagranitoids and mafic–ultramafic intrusions from the Almas-Conceicao do Tocantins Domain (ACTD). This was coupled with geochemical data from the metagranitoids to better constrain the processes of continental crust evolution in this region during the Siderian period. Two main plutonic episodes were recognized in the mapped area: (i) an early suite (2.47 Ga) dominated by tonalites and trondhjemites with subordinate biotite granites (Ribeirao das Areias Complex - RAC); and (ii) a later suite (2.30 Ga) including tonalites and trondhjemites (Ribeirao Itaboca Suite - RIS). Most of the RAC trondhjemite-tonalite-granodiorite (TTG) rocks are marked by fractionated REE patterns with high (La/Yb)N = 15–107 and samples have medium to high Sr/Y ratio (28–257). These TTG include both high- and low-Al types and high- and medium-pressure groups. The RIS TTG suite displays higher HREE contents with high (La/Yb)N = 65–89 and high Sr/Y ratio (59–95) and contains the high-Al type and the medium pressure group. In spite of the wide age gap between them, both RAC and RIS are characterized by TTG rocks formed in a subduction-like tectonic setting. The biotite granites are related to a magmatic stage after the TTG formation. Mafic rocks of the Gameleira Suite have an abundance of zircon, interpreted as crustal contamination, with dominant 207Pb/206Pb age populations of 2.48 and 2.30 Ga, and are interpreted to be associated with an extensional magmatic event following the Siderian period. Regional geotectonic correlations within the Sao Francisco Craton based on data compiled from the literature indicate a significant volume of Siderian crust generation that has been overlooked in continental amalgamation models and that TTG magmatism is a more common geochemical signature in Paleoproterozoic rocks than has been previously suggested.

中文翻译：

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戈亚斯地块的侧地壳 (2.47-2.3 ga) 及其作为圣弗朗西斯科古大陆基石的作用

摘要 巴西中部巴西利亚带北部基底以早古元古代产生的大量 TTG 岩浆活动为主，代表了里亚克期圣弗朗西斯科古大陆熔接前形成的陆块，蕴藏着有关古元古代地壳生长和混杂作用的机制和产物。新的 U-Pb 锆石年代学数据是从 Almas-Conceicao do Tocantins 域 (ACTD) 的变花岗岩和镁铁质-超镁铁质侵入体中获得的。这与变花岗岩的地球化学数据相结合，以更好地限制该地区在 Siderian 时期的大陆地壳演化过程。在映射区域识别出两个主要的深成期：(i) 早期组曲 (2. 47 Ga) 以斜长岩和长闪长岩为主，辅以黑云母花岗岩 (Ribeirao das Areias Complex - RAC)；(ii) 较晚的组曲（2.30 Ga），包括音调岩和长长岩（Ribeirao Itaboca Suite - RIS）。大多数 RAC 长闪长岩-辉长岩-花岗闪长岩 (TTG) 岩石以高 (La/Yb)N = 15-107 的分馏 REE 模式为标志，样品具有中高 Sr/Y 比 (28-257)。这些 TTG 包括高铝型和低铝型以及高压和中压组。RIS TTG 套件显示出较高的 HREE 含量，高 (La/Yb)N = 65–89 和高 Sr/Y 比 (59–95)，并包含高铝型和中压组。尽管它们之间的年龄差距很大，但RAC和RIS都以在类似俯冲构造环境中形成的TTG岩石为特征。黑云母花岗岩与TTG形成后的岩浆阶段有关。Gameleira Suite 的镁铁质岩含有丰富的锆石，被解释为地壳污染，207Pb/206Pb 的主要年龄群为 2.48 和 2.30 Ga，被解释为与 Siderian 时期之后的伸展岩浆事件有关。根据文献汇编的数据，圣弗朗西斯科克拉通内的区域大地构造相关性表明，大陆混杂模型中忽略了大量的 Siderian 地壳生成，并且 TTG 岩浆作用是古元古代岩石中比以前建议的更常见的地球化学特征。48 和 2.30 Ga，并被解释为与 Siderian 时期之后的伸展岩浆事件有关。根据文献汇编的数据，圣弗朗西斯科克拉通内的区域大地构造相关性表明，大陆混杂模型中忽略了大量的 Siderian 地壳生成，并且 TTG 岩浆作用是古元古代岩石中比以前建议的更常见的地球化学特征。48 和 2.30 Ga，并被解释为与 Siderian 时期之后的伸展岩浆事件有关。根据文献汇编的数据，圣弗朗西斯科克拉通内的区域大地构造相关性表明，大陆混杂模型中忽略了大量的 Siderian 地壳生成，并且 TTG 岩浆作用是古元古代岩石中比以前建议的更常见的地球化学特征。