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| Registros recuperados : 71 | |
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| 44. | | RIVA, R. D. D.; LIMA, D. C.; FERNANDES FILHO, E. I.; COSTA, L. M.; VIANA, J. H. M.; SILVA, C. H. C.; NUNES, D. F. Sistemas binários de esferas de vidro e fração de areia de um solo tropical: modelagem de densidade. In: CONGRESSO BRASILEIRO DE MECÂNICA DOS SOLOS E ENGENHARIA GEOTÉCNICA, 15.; CONGRESSO LUSO BRASILEIRO DE GEOTECNIA, 5.; SIMPÓSIO BRASILEIRO DE JOVENS GEOTÉCNICOS, 4.; SIMPÓSIO BRASILEIRO DE MECÂNICA DAS ROCHAS, 5., 2010, Gramado. Engenharia geotécnica para o desenvolvimento: inovação e sustentabilidade. Gramado: ABMS, 2010. 1 CD-ROM. COBRAMSEG 2010.| Biblioteca(s): Embrapa Milho e Sorgo. |
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| 45. | | MACHADO, M. L.; VIEIRA, T. G. C.; ALVES, H. M. R.; LACERDA, M. P. C.; ANDRADE, H.; FERNANDES FILHO, E. I. Sensoriamento remoto e sistema de informações geográficas para mapeamento de áreas de café na Zona da Mata de Minas Gerais. In: SIMPÓSIO DE PESQUISA DOS CAFÉS DO BRASIL, 3., 2003, Porto Seguro. Resumos... Brasília, DF: Embrapa Café, 2003.| Biblioteca(s): Embrapa Café. |
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| 46. | | CARVALHO JUNIOR, W. de; FERNANDES FILHO, E. I.; VIEIRA, C. A. O.; SCHAEFER, C. E. G. R.; CHAGAS, C. da S. Geomorphometric attributes applied to soil-landscapes supervised classification of mountainous tropical areas in Brazil: a case study. In: HARTEMINK, A. E.; McBRATNEY, A.; MENDONÇA-SANTOS, M. de L. (ed.). Digital soil mapping with limited data. Dordrecht: Springer, 2008. cap. 32, p. 357-365.| Biblioteca(s): Embrapa Solos. |
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| 48. | | CHAGAS, C. da S.; FERNANDES FILHO, E. I.; VIEIRA, C. A. O.; SCHAEFER, C. E. G. R.; CARVALHO JUNIOR, W. de. Atributos topográficos e dados do Landsat 7 no mapeamento digital de solos com uso de redes neurais. Pesquisa Agropecuária Brasileira, Brasília, DF, v. 45, n. 5, p. 497-50, maio 2010.| Biblioteca(s): Embrapa Solos; Embrapa Unidades Centrais. |
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| 60. | | MENDONÇA, B. A. F. do; FERNANDES FILHO, E. I.; SCHAEFER, C. E. G. R.; SIMAS, F. N. B.; VALE JUNIOR, J. F. do; LISBOA, B. de A. R.; MENDONÇA, J. G. F. de. Solos e ambientes do parque nacional do Viruá e entorno, Roraima: visão integrada da paisagem e serviço ambiental. Ciência Florestal, Santa Maria, RS, v. 23, n. 2, p. 427-442, abr./jun. 2013.| Biblioteca(s): Embrapa Florestas. |
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| Registros recuperados : 71 | |
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 | Acesso ao texto completo restrito à biblioteca da Embrapa Milho e Sorgo. Para informações adicionais entre em contato com cnpms.biblioteca@embrapa.br. |
Registro Completo
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Biblioteca(s): |
Embrapa Milho e Sorgo. |
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Data corrente: |
09/08/2006 |
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Data da última atualização: |
28/05/2018 |
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Tipo da produção científica: |
Artigo em Periódico Indexado |
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Autoria: |
VIANA, J. H. M.; COUCEIRO, P. R. C.; PEREIRA, M. C.; FABRIS, J. D.; FERNANDES FILHO, E. I.; SCHAEFER, C. E. G. R.; RECHENBERG, H. R.; ABRAHAO, W. A.; MANTOVANI, E. C. |
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Afiliação: |
JOAO HERBERT MOREIRA VIANA, CNPMS; EVANDRO CHARTUNI MANTOVANI, CNPMS. |
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Título: |
Occurrence of magnetite in the sand fraction of an Oxisol in the Brazilian savanna ecosystem, developed from a magnetite-free lithology. |
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Ano de publicação: |
2006 |
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Fonte/Imprenta: |
Australian Journal of Soil Research, Victoria, v. 44, n. 1, p. 71-83, 2006. |
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Idioma: |
Inglês |
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Conteúdo: |
It is relatively well established from many pedogenetic studies that, in deeply weathered Oxisols from Central Brazil, magnetite or maghemite are either inherited or transformed from magnetite of the mafic parent material. However, no similar pedogenetic pathways have been reported in the literature for other lithologies, such as limestone and pelitic rocks (shales and slates) of the Bambui Group in Brazil. In these sedimentary, non-mafic lithologies, magnetic minerals are not likely to occur. Despite that, magnetic nodules were identified in a representative Oxisol pedon developed on this pedodomain, under savanna (Cerrado). Magnetic and non-magnetic fractions of nodules were separated with a hand magnet. Chemical and mineralogical compositions of these nodules were determined by conventional chemical methods, powder X-ray diffractometry (XRD), and 298K Mossbauer spectroscopy. For the magnetic fraction, containing up to 84 dag/kg of Fe2O3 but also relatively rich in Al, Ti, Cr, and Si, Mossbauer measurements were also made at 4.2 K, without and with an externally applied magnetic field of 8 Tesla, and at 100 K. Mossbauer results and structural Rietveld refinement of the XRD data consistently suggest that the iron oxide mineralogy corresponds to approximately equivalent proportions of hematite and a partially oxidised magnetite, containing 3 dag/kg of iron as FeO. Laboratory tests were conducted in an attempt to produce magnetic material by heating this non-magnetic fraction. The sample was wrapped in filter paper and heated at 300 degrees C for 30 min, and the results were compared with the naturally occurring magnetic nodules. The saturation magnetisation value of the thermally treated sample was found to be sigma=7 J/T.kg, well below sigma=16 J/T.kg of the magnetic soil nodules. Mossbauer and XRD results indicate that the iron oxide mineralogy of this laboratory-produced magnetic sample also corresponds to a mixture of partially oxidised magnetite and hematite. Two other parts of the same non-magnetic, naturally hematite-rich precursor were mixed with charcoal, to act as reducing agent, and oven-heated at 450 degrees C and 600 degrees C, respectively, for 1 h, producing increasing reduction of the hematite to magnetite. These laboratory simulations support the model in which magnetite in these hematite-rich nodules was formed under the influence of seasonal burning regimes of the covering vegetation, followed by partial re-conversion of the magnetite particles to hematite under long-term atmospheric exposure to air. This model is consistent with a long-term, seasonal. re history, assumed for the genesis of the Cerrado ecosystem in the Central Brazil, although a wider validity for the entire Bambui Group area remains open. MenosIt is relatively well established from many pedogenetic studies that, in deeply weathered Oxisols from Central Brazil, magnetite or maghemite are either inherited or transformed from magnetite of the mafic parent material. However, no similar pedogenetic pathways have been reported in the literature for other lithologies, such as limestone and pelitic rocks (shales and slates) of the Bambui Group in Brazil. In these sedimentary, non-mafic lithologies, magnetic minerals are not likely to occur. Despite that, magnetic nodules were identified in a representative Oxisol pedon developed on this pedodomain, under savanna (Cerrado). Magnetic and non-magnetic fractions of nodules were separated with a hand magnet. Chemical and mineralogical compositions of these nodules were determined by conventional chemical methods, powder X-ray diffractometry (XRD), and 298K Mossbauer spectroscopy. For the magnetic fraction, containing up to 84 dag/kg of Fe2O3 but also relatively rich in Al, Ti, Cr, and Si, Mossbauer measurements were also made at 4.2 K, without and with an externally applied magnetic field of 8 Tesla, and at 100 K. Mossbauer results and structural Rietveld refinement of the XRD data consistently suggest that the iron oxide mineralogy corresponds to approximately equivalent proportions of hematite and a partially oxidised magnetite, containing 3 dag/kg of iron as FeO. Laboratory tests were conducted in an attempt to produce magnetic material by heating this non-magnetic fraction... Mostrar Tudo |
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Thesagro: |
Cerrado; Solo. |
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Categoria do assunto: |
-- |
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Marc: |
LEADER 03550naa a2200241 a 4500
001 1489543
005 2018-05-28
008 2006 bl uuuu u00u1 u #d
100 1 $aVIANA, J. H. M.
245 $aOccurrence of magnetite in the sand fraction of an Oxisol in the Brazilian savanna ecosystem, developed from a magnetite-free lithology.$h[electronic resource]
260 $c2006
520 $aIt is relatively well established from many pedogenetic studies that, in deeply weathered Oxisols from Central Brazil, magnetite or maghemite are either inherited or transformed from magnetite of the mafic parent material. However, no similar pedogenetic pathways have been reported in the literature for other lithologies, such as limestone and pelitic rocks (shales and slates) of the Bambui Group in Brazil. In these sedimentary, non-mafic lithologies, magnetic minerals are not likely to occur. Despite that, magnetic nodules were identified in a representative Oxisol pedon developed on this pedodomain, under savanna (Cerrado). Magnetic and non-magnetic fractions of nodules were separated with a hand magnet. Chemical and mineralogical compositions of these nodules were determined by conventional chemical methods, powder X-ray diffractometry (XRD), and 298K Mossbauer spectroscopy. For the magnetic fraction, containing up to 84 dag/kg of Fe2O3 but also relatively rich in Al, Ti, Cr, and Si, Mossbauer measurements were also made at 4.2 K, without and with an externally applied magnetic field of 8 Tesla, and at 100 K. Mossbauer results and structural Rietveld refinement of the XRD data consistently suggest that the iron oxide mineralogy corresponds to approximately equivalent proportions of hematite and a partially oxidised magnetite, containing 3 dag/kg of iron as FeO. Laboratory tests were conducted in an attempt to produce magnetic material by heating this non-magnetic fraction. The sample was wrapped in filter paper and heated at 300 degrees C for 30 min, and the results were compared with the naturally occurring magnetic nodules. The saturation magnetisation value of the thermally treated sample was found to be sigma=7 J/T.kg, well below sigma=16 J/T.kg of the magnetic soil nodules. Mossbauer and XRD results indicate that the iron oxide mineralogy of this laboratory-produced magnetic sample also corresponds to a mixture of partially oxidised magnetite and hematite. Two other parts of the same non-magnetic, naturally hematite-rich precursor were mixed with charcoal, to act as reducing agent, and oven-heated at 450 degrees C and 600 degrees C, respectively, for 1 h, producing increasing reduction of the hematite to magnetite. These laboratory simulations support the model in which magnetite in these hematite-rich nodules was formed under the influence of seasonal burning regimes of the covering vegetation, followed by partial re-conversion of the magnetite particles to hematite under long-term atmospheric exposure to air. This model is consistent with a long-term, seasonal. re history, assumed for the genesis of the Cerrado ecosystem in the Central Brazil, although a wider validity for the entire Bambui Group area remains open.
650 $aCerrado
650 $aSolo
700 1 $aCOUCEIRO, P. R. C.
700 1 $aPEREIRA, M. C.
700 1 $aFABRIS, J. D.
700 1 $aFERNANDES FILHO, E. I.
700 1 $aSCHAEFER, C. E. G. R.
700 1 $aRECHENBERG, H. R.
700 1 $aABRAHAO, W. A.
700 1 $aMANTOVANI, E. C.
773 $tAustralian Journal of Soil Research, Victoria$gv. 44, n. 1, p. 71-83, 2006.
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