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Registros recuperados: 5
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Biogeochemistry of REE elements and tetrad effect in the soil-plant system: a study on volcanic rock covers in southernmost Brazil Anais da ABC (AABC)
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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Geochemistry and petrogenesis of post-collisional ultrapotassic syenites and granites from southernmost Brazil: the Piquiri Syenite Massif Anais da ABC (AABC)
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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Paleoproterozoic (~1.88Ga) felsic volcanism of the Iricoumé Group in the Pitinga Mining District area, Amazonian Craton, Brazil: insights in ancient volcanic processes from field and petrologic data Anais da ABC (AABC)
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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Petrology of dioritic, tonalitic and trondhjemitic gneisses from Encantadas Complex, Santana da Boa Vista, southernmost Brazil: paleoproterozoic continental-arc magmatism Anais da ABC (AABC)
Philipp,Ruy P.; Lusa,Marcelo; Nardi,Lauro V.S..
The Encantadas Complex is a unit composed of dioritic, tonalitic and trondhjemitic gneisses with minor hornblendite. This complex is intruded by granites of Neoproterozoic age. Major and trace element data indicate metaluminous to slightly peraluminous composition related to the medium-K calc-alkaline series. Compositional parameters are consistent with a common evolution from less differentiated magmas, probably through fractional crystallization. The orthogneisses show LaN/YbN ratios from 10 to 50, K2O/Na2O varying from 1.1 to 3.0, Y contents from 3 to 39 ppm, Yb from 0.3 to 3.7, and Lu with contents in the range 0.06 and 0.54 ppm. Such geochemical features are similar to those of Archaean tonalitic rocks and are usually described in rocks formed by...
Tipo: Info:eu-repo/semantics/article Palavras-chave: Continental arch; Crustal evolution; Encantadas gneisses; Paleoproterozoic; Petrology; TTG.
Ano: 2008 URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0001-37652008000400013
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Petrology of Gameleira potassic lamprophyres, São Francisco Craton Anais da ABC (AABC)
Plá Cid,Jorge; Campos,Cristiani S.; Nardi,Lauro V.S.; Florisbal,Luana.
Gameleira lamprophyres are dykes and mafic microgranular enclaves associated with the shoshonitic Gameleira monzonite. This association belongs to the Paleoproterozoic alkaline magmatism from Serrinha nucleus, northeast Brazil. The liquidus paragenesis is diopside, pargasite, apatite and mica. Reverse zoning was identified in the groundmass alkali feldspar and was related to the undercooling of lamprophyric magma during the emplacement, with high growth rate of pargasite/edenite inducing disequilibrium between feldspars and liquid. Chemical data indicate that the lamprophyres are basic rocks (SiO2 < 48 wt%), with alkaline character (Na2O + K2O &gt; 3 wt%) and potassic signature (K2O/Na2O ≈ 2). High contents of MgO and Cr are consistent with a...
Tipo: Info:eu-repo/semantics/article Palavras-chave: Potassic lamprophyres; Gameleira lamprophyres; São Francisco Craton; Mantle metasomatism; Petrology; Mineralogy.
Ano: 2012 URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0001-37652012000200010
Registros recuperados: 5
Primeira ... 1 ... Última
 

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