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| Pierosan,Ronaldo; Lima,Evandro F.; Nardi,Lauro V.S.; Campos,Cristina P. de; Bastos Neto,Artur C.; Ferron,José M.T.M.; Prado,Maurício. |
| The Iricoumé Group correspond to the most expressive Paleoproterozoic volcanism in the Guyana Shield, Amazonian craton. The volcanics are coeval with Mapuera granitoids, and belong to the Uatumã magmatism. They have U-Pb ages around 1880 Ma, and geochemical signatures of α-type magmas. Iricoumé volcanics consist of porphyritic trachyte to rhyolite, associated to crystal-rich ignimbrites and co-ignimbritic fall tuffs and surges. The amount and morphology of phenocrysts can be useful to distinguish lava (flow and dome) from hypabyssal units. The morphology of ignimbrite crystals allows the distinction between effusive units and ignimbrite, when pyroclasts are obliterated. Co-ignimbritic tuffs are massive, and some show stratifications that suggest deposition... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Amazonian Craton; Caldera complex; Ignimbrite; Iricoumé volcanism; Surge deposits; Uatumã magmatism. |
| Ano: 2011 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0001-37652011000300012 |
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