2019-08-292019-08-292019-05-16VIANNA, Sâmia Queiroz. Geocronologia U-Pb e geoquímica isotópica Nd-Hf dos granitoides transamazônicos do domínio Lourenço, sudeste do Escudo das Guianas. Orientador: Jean Michel Lafon. 2019. 103 f. Dissertação (Mestrado em Geologia e Geoquímica) – Instituto de Geociências, Universidade Federal do Pará, Belém, 2019. Disponível em: http://repositorio.ufpa.br/jspui/handle/2011/11570 . Acesso em: .https://repositorio.ufpa.br/handle/2011/11570The eastern part of the Guyana Shield, northern portion of the Amazonian Craton, is located in the Maroni-Itacaiúnas Province (PMI), defined as a paleoproterozoic mobile belt added to an Archaean block during the Transamazonian event (2.26-1.95 Ga). In the state of Amapá, Northern Brazil, the Paleoproterozoic Lourenço Domain consists mainly of Rhyacian gneisses, granitoids and greenstone sequences, with some fragments of Archean rocks in its southernmost portion. To the south, the Amapá Block is defined as a continental landmass formed by Neo-Mesoarchean units (2.85-2.60 Ga) strongly reworked during the Transamazonian orogenic cycle, and by Rhyacian granitoids and supracrustal sequences. The region of Tartarugalzinho, in central-eastern sector of the state of Amapá, is located at the transition between the Paleoproterozoic Lourenço Domain and the Archean Amapá Block. Several granitoid suites were identified in this region (Flexal Intrusive Suite, Papa-Vento Tonalite and Vila Bom Jesus Granite). We performed in situ U-Pb and Lu-Hf isotope analyses on zircon byplasma induced mass spectrometry with laser ablation (LA-ICP-MS), Sm-Nd wholerock by thermal ionization mass spectrometry (TIMS), together with petrography and major and trace element geochemistry, in order to constrain the evolutionary stages of the Transamazonian orogenesis, in which these granitoids are inserted. In addition, the study aimed to contribute to insert the southern portion of the Lourenço Domain within a geodynamic models for the Southeastern Guiana Shield (SGS) and to investigate the processes of crustal growth and reworking during the Rhyacian. The U-Pb geochronology furnished cristalization ages of 2176 ± 9 Ma, 2176 ± 5 Ma e 2166 ± 15 Ma for the Flexal Intrusive Suite, 2131 ± 11 Ma for the Papa-Vento Tonalite and 2085 ± 16 Ma and 2078 ± 8 Ma for the Vila Bom Jesus Granite, that achieved the identification of the two magmatic episodes (~2.18-2.13 and ~2.08 Ga) during he Transamazonian orogeny for this sector of the Lourenço Domain. The Archean Nd-TDM (2.87-2.63 Ga) and Hf-TDM C (3.63-2.79) model ages and the negative values of εNd(t) (-2.74 to -5.43) and εHf(t) (-1.40 to -15.65) indicate the mixture of juvenile Rhyacian material with an Archean crustal component in the source of these magmas. Also, the combination of the petrographic, geochronological geochemical and isotope data allows us to recognize two distinct events. The first magmatic episode displays a calc-alkaline to high-K calcalkaline signature and peraluminous character indicating that it formed during subduction stages in a magmatic arc environment. The second magmatic episode exhibits a calc-alkaline to high-K calc-alkaline signature, metaluminous character and affinity with syn- to post-collision granites. It is still possible to correlate these magmatic events to the two main magmatic episodes that marked the Transamazonian evolution throughout the southeastern Guiana Shield; The geochronological and geochemical data suggest that this sector of the Transamazonian orogeny was built up by accretion of volcanic arcs with subsequent arc-continent collision, however the existence of a continental magmatic arc at the margin of the Archean block cannot be still totally descarded.Acesso AbertoGeocronologia U-PbZircãoEscudo das GuianasCráton AmazônicoGeocronologia U-Pb e geoquímica isotópica Nd-Hf dos granitoides transamazônicos do domínio Lourenço, sudeste do Escudo das Guianas.DissertaçãoCNPQ::CIENCIAS EXATAS E DA TERRA::GEOCIENCIASGEOCRONOLOGIA E GEOQUÍMICA ISOTÓPICAGEOQUÍMICA E PETROLOGIA