2023-09-142023-09-142021-12-06GONÇALVES, Renato Cantão. Geoquímica e Geocronologia U-Pb-Hf do Magmatismo Meso- Neoarqueano da Borda Norte do Bloco Amapá, Sudeste do Escudo das Guianas. Orientador: Jean Michel Lafon. 2023. 166 f. Dissertação (Mestrado em Geologia e Geoquímica) – Programa de Pós-Graduação em Geologia e Geoquímica, Instituto de Geociências, Universidade Federal do Pará, Belém, 2023. Disponível em: https://repositorio.ufpa.br/jspui/handle/2011/15929. Acesso em:.https://repositorio.ufpa.br/jspui/handle/2011/15929The southeastern portion of the Guiana Shield (SEG), in the northern region of the Amazonian Craton, is defined as a broad Paleoproterozoic orogenic belt added to an Archean block strongly reworked during the Transamazonian Cycle (2.26–1.95 Ga). This Archean block in the central portion of the state of Amapá, called the Amapá Block, is made up of a mesoneoarchean granulite-gneiss-migmatite association (~2.85 Ga and ~2.70-2.60 Ga) and by Rhyacian granitoids and metavolcanosedimentary sequences. The Amapá Block is delimited to the south and north by the Carecuru and Lourenço Rhyacian domains with Archean crustal relics. The Lourenço Domain is formed by Rhyacian granitoids, gneisses and metavolcanosedimentary sequences formed in magmatic arcs (2.20-2.12 Ga), followed by syncollisional to late orogenic magmatism (~2.11-2.07 Ga) and late granulitic metamorphism (~2.06-2.04 Ga). On the boundary between the Amapá Block and Lourenço Domain, Mesoarchean units (Gnaisse Porfírio - 3.19 Ga and Complexo Tumucumaque - 2.85 Ga) and Neoarchean units (Complex Guianense - ~2.65 Ga and Metagranitoid Pedra do Meio - 2.59 Ga) occur. Near Vila Bom Jesus village, (municipality of Tartarugalzinho - AP), at the transition between Archean and Rhyacian domains, orthogneisses and metagranitoids were dated by the U-Pb method in zircon by ICP-MS mass spectrometry and laser ablation (LA-ICP- MS) to investigate the geographic extension of the Porfírio Gneiss and Pedra do Meio Metagranitoid. Additionally, petrographic data, geochemical analyzes in whole rock and Lu-Hf isotopic geochemistry in zircon by LA-ICP-MS were used, together with previous data from orthogneisses and granitoids of the northern portion of the Amapá Block, to investigate the geodynamic context of formation of these granitoids and the episodes of generation and reworking of the continental crust during the Archean in this portion of the SEG. U-Pb dating of a biotite granodiorite orthogneiss provided a 207Pb/206Pb crystallization age of 2846 ± 36 Ma (MSWD = 1.3) for the orthogneiss magmatic precursor, indicating a Mesoarchean magmatic episode. Three samples of orthogneiss and metagranitoids provided 207Pb/206Pb crystallization ages of 2654 ± 12 Ma (MSWD = 1.4), 2618 ± 31 Ma (MSWD = 1.15) and 2618 ± 22 Ma (MSWD = 0.71) respectively, indicating a protracted Neoarchean magmatic episode. The U-Pb dating of a biotite granodiorite orthogneiss with crystallization age 207Pb/206Pb of 2096 ± 24 Ma (MSWD = 0.75) indicates the presence of imbricated Paleoproterozoic rocks in the Archean units of the investigated sector. These results lead to reconsider the configuration of the Archean units on the north edge of the Amapá Block. The Porfírio Gneiss and the Tumucumaque Complex must constitute only enclaves or xenoliths of the Mesoarchean basement in Neoarchean orthogneisses and granitoids. The Pedra do Meio Metagranitoid represents intrusive charnockitic plutons in the Guianense Complex, which is the dominant unit in the investigated sector. The geochemical data showed that the Mesoarchean samples have signature of biotite granites of crustal derivation. Neoarchean magmatism is also dominated by crustalderived biotite granites, but also includes granitoids with sanukitoids and high-pressure TTG affinities, in addition to hybrid granites. The geochemical signatures of biotite granites, the subchondrite values of ƐHf(t) (-11.3 < ƐHf(t) < -0.4) with Hf-TDM model ages between 3.9 and 3.2 Ga, and the presence of inherited zircons in most Neoarchean samples, with Mesoarchean (3.0, 2.89, 2.84 Ga) and Neoarchean (2.77, 2.74, 2.72 Ga) ages, indicate that this protracted Neoarchean magmatic episode reworked older units from the basement of the Amapá Block (Meso-Paleoarchean), in a collisional context with no evidence of crustal growth during the Neoarchean. However, it is still open which continental masses collided to form this portion of the Amapá Block, considering that the other Archean domains of the Amazonian (Carajás Province; Imataca Complex) and West African (Leo-Man Domain; Reguibat Shield) present a different geological history from the Amapá Block during the Neoarchean.Acesso AbertoAttribution-NoDerivs 3.0 Brazilhttp://creativecommons.org/licenses/by-nd/3.0/br/Transição arqueano-paleoproterozoicoMagmatismo arqueanoGeoquímica elementarGeocronologia U-Pb-Hf em zircãoSudeste do Escudo das GuianasBloco AmapáArchean-paleoproterozoic transition;Archean magmatismElemental geochemistryU-Pb-Hf geochronology in zirconSoutheast Guyana ShieldAmapá BlockDissertaçãoCNPQ::CIENCIAS EXATAS E DA TERRA::GEOCIENCIAS::GEOLOGIA::GEOQUIMICAGEOCRONOLOGIA E GEOQUÍMICA ISOTÓPICAGEOQUÍMICA E PETROLOGIA