2022-02-162022-02-162021-06-08OLIVEIRA, Pedro Guilherme Assunção. Proveniência da Formação Diamantino no sul do Cráton Amazônico: Implicações cronoestratigráficas e o contexto tectônico. Orientador: Afonso César Rodrigues Nogueira. 2021. 45 f. Trabalho de Curso (Bacharelado em Geologia) - Faculdade de Geologia, Instituto de Geociências, Universidade Federal do Pará, Belém, 2021. Disponível em: https://bdm.ufpa.br:8443/jspui/handle/prefix/3832. Acesso em:.https://bdm.ufpa.br/handle/prefix/3832The first record of Paleozoic deposits from the southern Amazon Craton was recently interpreted as deposits from epicontinental seas in the initial phase of the West Gondwana. These deposits have been interpreted as part of a weakly inverted Ediacaran-Cambrian basin filled by carbonate rocks from the Araras Group (Lower Ediacaran) and siliciclastic rocks from the Alto Paraguai Group (Cambrian-Ordovician) overlying crystalline and metamorphic rocks, respectively from the Amazonian Craton and Paraguay Belt. The lake and deltaic deposits of Diamantino Formation, upper Alto Paraguai Group, would represent the epicontinental sea closure in the context of the Araras-Alto Paraguai Basin. Facies studies have confirmed this paleoenvironmental interpretation, while petrographic and provenance data in combination with polychromatic cathodoluminescence has revealed that the Diamantino Formation is probably younger than Paleozoic and belongs to the Cretaceous strata of the Parecis Basin. The Diamantino Formation consists of lithic and sublithic sandstones, and greywacke, with subangular-subrounded and spherical quartz grains, volcanic rock fragments, pelitic intraclasts, rare feldspars, and metamorphic rock fragments indicating low compositional maturity. Quartz has embayments, vacuoles, open and filled fractures, forms mosaics, oriented white patches that indicate three distinct groups of quartz in these sandstones: volcanic, low-medium metamorphic, and plutonic. Dark and reddish luminescence of quartz indicate volcanic rocks as source-area. Thus, metamorphic rocks from the Paraguay and Brasília belts, and Goiás Massif, were not the primary source areas as previously interpreted. Eogenetic and telogenetic processes were predominate. The continental facies of the Diamantino Formation is not compatible with the Cambrian marine deposits from the West Gondwana, and previous geochronological data suggest ages no older than the Permian. The abundance of volcanic clasts in Diamantino deposits is intriguing since Ediacaran, and Paleozoic volcanic rocks are absent in the southern Amazon Craton. In contrast, Mesozoic volcanic rocks from the Tapirapuã and Anari formations (~190 Ma) occur as dikes in the Araras-Paraguay Basin and intrusive and sills bodies in the Parecis Basin. This magmatism is related to the opening of the Central Atlantic Ocean or CAMP. We considered the Diamantino Formation as a post-CAMP deposit linked to a lacustrine phase during thermal subsidence after voluminous lava flows and outpouring of tholeiitic basalts. Although the conclusions obtained in this work are not definitive, they open a perspective to guide future geological and geochronological studies to increase the resolution of the evolutionary scenario of this part of the southern Amazon Craton.Acesso AbertoPetrografiaProveniênciaLacustreConstituintes vulcânicosQuartzoPetrographyProvenanceLacustrineVolcanic constituentsQuartzCNPQ::CIENCIAS EXATAS E DA TERRA::GEOCIENCIAS::GEOLOGIATrabalho de Curso - Graduação - Monografia