Abstract The Cristalândia do Piaui Block, located in the northwestern margin of the Sao Francisco Craton, represents the basement of the Rio Preto Fold Belt. It is composed of Archean orthogneisses of ca. 3.2 Ga reworked at 2.81 and 2.68 Ga with juvenile to moderately juvenile eHf values between -1.51 and -8.07, and high-K syenogranites dated at 2.65 Ga with crustal eHf values between -10.37 and -19.54, both with model ages (TDMc) varying from 3.57 to 4.33 Ga, indicating cryptic Paleo- to Eoarchean and even Hadean sources. Metamafic-ultramafic rocks, iron formations, metacherts, and graphite schists occur in association with the Archean orthogneiss. The whole set is intruded by Paleoproterozoic (ca. 2.2 Ga) metagranitoids with compositions varying from granodioritic with sanukitoid-type signatures to monzogranitic, and alkali-feldspar granitic with crustal signatures. They are related to the Rhyacian-Orosirian orogeny, responsible for the complex deformation patterns printed in the Archean basement. Orosirian metasedimentary rocks are represented by garnet-biotite paragneiss with maximum depositional age of ca. 1.95 Ga. Intrusive mafic dikes in the complex show ages of ca. 2.07 Ga and isotopic features of mantle-derived magmas. Considering the presented data, the Cristalândia do Piaui Block represents a metacratonic domain corresponding to part of the Guanambi-Correntina Paleoplate, wich had been involved in crustal accretion and reworking from the Archean to the Paleoproterozoic. Many of the elements of the evolutionary stages wicha are present in the Sao Francisco-Congo Paleocontinent can be recognized, suggesting an evolution of this crustal segment amounts to the Eoarchean era and disclosing the existence of cryptic Paleoarchean or even Hadean nuclei, reworked in at least three metamorphic events during the Rhyacian-Orosirian orogeny.

中文翻译：

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巴西圣弗朗西斯科克拉通西北部的太古宙和古元古代地壳演化和神秘古太古代-哈德宙源的证据：Cristalândia do Piauí 地块的岩石化学、地质年代学和同位素系统学

摘要 Cristalândia do Pauui 地块位于圣弗朗西斯科克拉通西北边缘，代表了里约普雷图褶皱带的基底。它由大约的太古代正片麻岩组成。3.2 Ga 在 2.81 和 2.68 Ga 处重新加工，幼年到中等幼年 eHf 值介于 -1.51 和 -8.07 之间，高 K 正长花岗岩的年代为 2.65 Ga，地壳 eHf 值介于 -10.37 和 -19.54 之间，两者都具有不同的模型年龄（TDM）从 3.57 到 4.33 Ga，表明神秘的古至始太古代甚至冥界的来源。变镁铁质-超镁铁质岩石、铁地层、变质岩和石墨片岩与太古代正方麻岩一起出现。整个集合被古元古代（约 2.2 Ga）变花岗岩侵入，其成分从具有 sanukitoid 型特征的花岗闪长岩到二长花岗岩，和具有地壳特征的碱长石花岗岩。它们与 Rhyacian-Orosirian 造山运动有关，负责打印在太古代基底中的复杂变形模式。奥罗斯纪变沉积岩以石榴石-黑云母副片麻岩为代表，最大沉积年龄约为 1.95 Ga。复杂的侵入性镁铁质岩脉显示约 1.95 年的年龄。2.07 幔源岩浆的 Ga 和同位素特征。考虑到所提供的数据，Cristalândia do Pauui 地块代表了一个与关那比-科伦蒂纳古板块的一部分相对应的变克拉通域，该域参与了地壳增生和从太古代到古元古代的改造。可以识别出圣弗朗西斯科-刚果古大陆中存在的许多进化阶段的元素，