DEGEO - Departamento de Geologia

URI permanente desta comunidadehttp://www.hml.repositorio.ufop.br/handle/123456789/8

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20002

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Autor: search.filters.author.Nalini Júnior, Hermínio AriasAssunto: search.filters.subject.Granitoids

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    Syn-collisional peraluminous magmatism in the Rio Doce region : mineralogy, geochemistry and isotopic data of the Urucum suite (eastern Minas Gerais state, Brazil).
    (2000) Nalini Júnior, Hermínio Arias; Bilal, Essaid; Neves, José Marques Correia
    The Urucum Suite granitoids (Rio Doce region, southeastern Brazil) contains four main facies: megafeldspar granites, deformed medium- to coarse-grained granites, tourmaline, and pegmatitic facies. They intrude both the staurolite-garnet-muscovite-biotite schist of the São Tomé Formation (Rio Doce Group) and the Galiléia metaluminous suite (596 ±4 Ma). Detailed structural studies suggest that the Urucum Suite emplaced during an important dextral strike-slip movement (Dl phase) of the Brasiliano orogeny (650-450Ma). Modal and chemical mineralogical variations suggest an evolution from the megafeldspar facies to the pegmatitic facies. Whole-rock geochemistry indicates the peraluminous character of the Urucum Suite granitoids, the evolution from the megafeldspar facies granites to pegmatitic facies granites and suggests the syn-collisional character of this suite. U-Pb zircon (582 ± 2 Ma) and monazite (576-573 ± 4Ma) data indicate that the Urucum Suite emplaced during the Brasiliano orogeny. The peraluminous nature of the Suite and isotopic-rich character in the Rb-Sr (87Sr/86Sr = 0.7114 to 0.7165) and Sm-Nd (eNd = -7.4 and -8.2) systems indicate that it formed by partial melting of older intermediate to felsic crustal sources. Based on early Proterozoic model-ages (2.3 to 1.8 Ga) and on 2.0 Ga U-Pb inherited signature, granitoids of the Suite are probably derived from a rocks with a long crustal residence (Transamazonian basement), without extensive mantle contribution.
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    Neoproterozoic granitoid suites in southeastern Brazil.
    (2000) Bilal, Essaid; Horn, Adolf Heinrich; Nalini Júnior, Hermínio Arias; Mello, Fernando Machado de; Neves, José Marques Correia; Giret, Andre Roger; Moutte, Jaques; Fuzikawa, Kazuo; Fernandes, Maria Lourdes Souza
    Neoproterozoic granitoid suites in southeastern Brazil are closely related to the different tectonic events. Petrography, geochemistry and structural features allow to separate these rocks into pre-, syn-, late and post-tectonic granitoids. The whole emplacement process lasted less than 100 Ma: from 595 Ma for the pre-tectonic granitoids, to 500 Ma for the post-tectonic ones. During this interval a 45 Ma magmatic quiet period (from 582 to 537 Ma) can also be characterized. Detailed field observations and mapping, coupled with petrological and geochemical observations, indicate an important role of the Archaean and Paleoproterozoic crust in the genesis of these granitoids, showing even evidences of some mantle interactions.