Navegando por Assunto "Magmatismo - Pará, Noroeste"

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    Geoquímica e geocronologia U-Pb, Sm-Nd e Rb-Sr dos granitoides orosirianos do domínio Erepecuru-Trombetas, Província Amazônia Central, Noroeste do Pará
    (Universidade Federal do Pará, 2015-08-10) LEAL, Rafael Estumano; COSTA, Lúcia Travassos da Rosa; http://lattes.cnpq.br/3352314623448523; https://orcid.org/0000-0002-2666-9824; LAFON, Jean Michel; http://lattes.cnpq.br/4507815620234645
    The granitic rocks of the northwestern Pará State are part of two large volcano- plutonic associations that marked the central region of the Amazonian Craton during Orosirian. The area of this study is located in the southwest portion of the Erepecuru- Trombetas Domain, south of the Guyana Shield. The oldest association recently mapped and dated at about 2.0-1.95 Ga, is formed by volcanic rock of Igarapé Paboca formation and granitoids of Caxipacoré Suite. The youngest association (1.90-1.86 Ga) is related to the Água Branca and Mapuera suites and the effusive and pyroclastic rocks of Iricoumé Group. Petrographic studies in the Caxipacoré, Água Branca and Mapuera granitoids allowed the definition of five granitoids varieties (quartz-monzonite, monzonite, monzogranites, syenogranites and ácali-feldspar granites) with variable content of hornblende and biotite, the main mafic phases. In general, they are isotropic rocks, leucocratic, inequigranular, medium- to coarse-grained with hypidiomorphic granular, rapakivi, granophyric and micro-porphyritic textures. The geochemical characterization allowed the distinction of two rock groups with different signatures. The first group formed by Caxipacoré and Água Branca suites, shows high-K to shoshonitic, magnesian, metaluminous to peraluminous calc-alkaline trends. LILE- enrichment (e.g. K, Rb, Ba and Sr), strong negative Nb anomalies, moderate heavy REE- fractionation and weak Eu anomalies are common characteristics of these granites. The second lithological group formed by Mapuera Suite, comprises acid rocks (71.29
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