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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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| Cunha,Maria do Carmo Lima e; Nardi,Lauro V.S.; Muller,Ingke F.. |
| This paper deals with the distribution of REE in rock, soil and plant in an area of monzonitic rocks from southernmost Brazil. The REE patterns in Schinus lensticifolius show a negative-Ce anomaly and a prominent tetrad effect, characterized as W-type that are not present in rock and soil samples. The REE patterns in the soils and rocks sampled are very similar and there is no fractionation of REE during the processes of soil formation. The W-type patterns are interpreted as indicating that REE were absorved by S. lentiscifolius as simple ions rather than as complex ions, or, alternatively, that the transport of REE in the plant metabolic processes was as free ions. The recognition of tetrads, either, M- or W-type patterns, is an additional tool for... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: REE; Tetrad effect; Schinus lentiscifolius; Southernmost Brazil. |
| Ano: 2012 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0001-37652012000400006 |
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| Nardi,Lauro V.S.; Plá-Cid,Jorge; Bitencourt,Maria de Fátima; Stabel,Larissa Z.. |
| The Piquiri Syenite Massif, southernmost Brazil, is part of the post-collisional magmatism related to the Neoproterozoic Brasiliano-Pan-African Orogenic Cycle. The massif is about 12 km in diameter and is composed of syenites, granites, monzonitic rocks and lamprophyres. Diopside-phlogopite, diopside-biotite-augite-calcic-amphibole, are the main ferro-magnesian paragenesis in the syenitic rocks. Syenitic and granitic rocks are co-magmatic and related to an ultrapotassic, silica-saturated magmatism. Their trace element patterns indicate a probable mantle source modified by previous, subduction-related metasomatism. The ultrapotassic granites of this massif were produced by fractional crystallization of syenitic magmas, and may be considered as a particular... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Post-collisional magmatism; Ultrapotassic syenites; Ultrapotassic granites; A-type magmatism; Piquiri Syenite Massif. |
| Ano: 2008 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0001-37652008000200014 |
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