Silva, Daniel Adelino daMotoki, AkihisaSantos, Anderson Costa dosMendes, JulioJourdan, FredGeraldes, Mauro CésarLana, Cristiano de Carvalho2021-06-072021-06-072020SILVA, D. A. da. et al. Multiple processes of geochemical evolution for the alkaline rocks of Rio Bonito intrusive complex, Rio de Janeiro State, Brazil: 40Ar/39Ar and U-Pb ages and Lu-Hf isotopes on zircon and constraints on crustal signature. Geologia USP. Série Científica, São Paulo, v. 20, n. 4, p. 221-234, dez. 2020. Disponível em: <http://www.ppegeo.igc.usp.br/index.php/GUSPSC/article/view/13729>. Acesso em: 19 fev. 2021.2316-9095http://www.repositorio.ufop.br/handle/123456789/13262This article presents geochemical characteristics of the alkaline rocks of Rio Bonito intrusive complex, State of Rio de Janeiro, Brazil, which is constituted mainly by nepheline syenite. The fractional crystallisation of this magma decreases K2 O/(Na2 O + K2 O) and increases (Na + K)/Al. The TiO2 , Fe2 O3 *, MgO, CaO, and P2 O5 contents indicate fractionation of titanite, ilmenite, and clinopyroxene or amphibole. The total rare earth elements (REEs) are high, and the REE pattern is linear with negative gradient. The nepheline syenite aplite has low REEs, concave REE pattern, and positive Eu anomaly. The ultrabasic and basic mela-nepheline syenite samples have total REEs and light REEs higher than the felsic alkaline rocks. Therefore, the nepheline syenite magma is not derived directly from the alkaline ultrabasic magma. Laser-spot step-heating 40Ar/39Ar ages for biotite and amphibole are 65.03 ± 0.70 and 65.03 ± 0.46. U-Pb ages LA-ICP-MS for two samples are 65.49 ± 0.30 and 65.18 ± 0.30. Values of εHf are negative for both samples, indicating an important crustal component in the evolution of Rio Bonito.en-USabertoNepheline syeniteRio BonitoFractional crystallisationCrustal assimilation40Ar/39Ar and U-Pb datingMultiple processes of geochemical evolution for the alkaline rocks of Rio Bonito intrusive complex, Rio de Janeiro State, Brazil : 40Ar/39Ar and U-Pb ages and Lu-Hf isotopes on zircon and constraints on crustal signature.Múltiplos processos de evolução geoquímica para as rochas alcalinas do complexo intrusivo de Rio Bonito, Estado do Rio de Janeiro, Brasil : idades 40Ar/39Ar e U-Pb e isótopos Lu-Hf em zircão – considerações sobre assinatura crustal.Artigo publicado em periodicoO periódico Geologia USP. Série Científica permite que o Repositório Institucional da Universidade Federal de Ouro Preto (UFOP) deposite uma cópia eletrônica dos artigos publicados por esse periódico em que ao menos um dos autores faça parte da comunidade cientifica da UFOP. Fonte: Licença concedida mediante preenchimento de formulário enviado em 20 ago. 2014.http://dx.doi.org/10.11606/issn.2316-9095.v20-151049