Bauxitisation of anorthosites from Central Brazil.

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dc.contributor.authorOliveira, Fábio Soares de
dc.contributor.authorVarajão, Angélica Fortes Drummond Chicarino
dc.contributor.authorVarajão, César Augusto Chicarino
dc.contributor.authorBoulangé, Bruno
dc.contributor.authorGomes, Newton Souza
dc.date.accessioned2012-07-11T14:22:27Z
dc.date.available2012-07-11T14:22:27Z
dc.date.issued2011
dc.description.abstractPetrological studies using X-ray diffraction (XRD), X-ray fluorescence (XRF), optical microscopy, scanning electron microscopy (SEM-EDS) and electron microprobe analyzer (WDS) showed the mineralogical, micromorphological and geochemical transformations due to the bauxitisation of anorthosite from the Barro Alto Stratiform Mafic–Ultramafic Complex (Central Brazil). The hydrolytic alteration of the anorthosite occurred in two different stages in accordance with the order of stability of the minerals to the weathering: firstly the bytownite and secondly the ferromagnesian minerals. The weathering solutions, benefited from the existing network of fractures, percolated the weakness zones of the minerals characterising the microsystem of contact in which cores of plagioclase and ferromagnesian minerals were formed. In the first stage, the plagioclases are altered directly to gibbsite, and at an early stage, during the change process, the gibbsite crystals surround the primary ferromagnesian minerals that are totally or partially preserved. The transformation is isalteritic and is responsible for formation of porous alteromorphs consisting of septa of coarse gibbsite and fine gibbsite. As the weathering process advances, the ferromagnesian minerals directly enter to goethite. The boxworks of gibbsite and goethite characterise a primary plasmic microsystem.pt_BR
dc.identifier.citationOLIVEIRA, F. S. de et al. Bauxitisation of anorthosites from Central Brazil. Geoderma, v. 167-168, p. 319-327, nov. 2011. Disponível em: <https://www.sciencedirect.com/science/article/pii/S0016706111002722>. Acesso em: 11 jul. 2012.pt_BR
dc.identifier.issn00167061
dc.identifier.urihttp://www.repositorio.ufop.br/handle/123456789/1072
dc.language.isoen_USpt_BR
dc.rights.licenseO periódico Geoderma concede permissão para depósito deste artigo no Repositório Institucional da UFOP. Número da licença: 3333721216360.
dc.subjectBarro Alto complexpt_BR
dc.subjectBauxitept_BR
dc.subjectAlitisationpt_BR
dc.subjectIsalteritic transformationpt_BR
dc.subjectAnorthositept_BR
dc.titleBauxitisation of anorthosites from Central Brazil.pt_BR
dc.typeArtigo publicado em periodicopt_BR
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