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A Suíte Intrusiva Rio Dourado - um granito tipo A de 1,88 Ga - sudeste do Craton Amazônico - Mato Grosso - Brasil

2011; UNIVERSIDADE DE SÃO PAULO; Volume: 11; Issue: 1 Linguagem: Inglês

10.5327/z1519-874x2011000100005

2316-9095

Márcia Aparecida de Sant’Ana Barros, Márcio Martins Pimentel, Mara Luiza Barros Pita Rocha, Fernanda Rodrigues da Silva, Rosilene Aparecida Padilha, Elton Luiz Dantas, Evelin de Moura,

Geochemistry and Elemental Analysis

The Rio Dourado Intrusive Suite (RDIS) is composed of granitic rocks which are exposed in the southeastern Amazon Craton, Central Amazon Province. These granites intruded into the Paleoproterozoic granites of the Vila Rica Intrusive Suite. The predominantly pyroclastic felsic volcanic rocks of the Iriri Group are coeval and spatially associated with the intrusive granites. Petrographic studies allow us to divide the Rio Dourado granites into: biotite granites, amphibole-bearing biotite granites and granophyric granites. Modal compositions range from monzo to syenogranites. The oxidized A-type granite is characterized by FeO/FeO+MgO ranging from 0.8 - 0.95, high contents of FeO T and low contents of CaO, as well as peraluminous composition. In the tectonic discrimination diagrams, samples of these granites plot in the post-collisional field. REE patterns show enrichment in the LREE relative to HREE and negative Eu anomalies. Negative anomalies of Ta and Nb, as well as depletion in the HREE, features which are typical of A-type granites of post-collisional settings, are observed in multi-element diagrams,. Ce, Yb, Nb and Ga contents are transitional between those of A2 and A1-type granites. U-Pb zircon dating by TIMS yielded an age of 1876 ± 39, whereas negative values of εNd (-3 to -10) and model ages (T DM) between 2.6 and 2.8 Ga indicate it was formed by re-melting of older (possibly Archean) crust.