EM - Escola de Minas
URI permanente desta comunidadehttp://www.hml.repositorio.ufop.br/handle/123456789/6
Notícias
A Escola de Minas de Ouro Preto foi fundada pelo cientista Claude Henri Gorceix e inaugurada em 12 de outubro de 1876.
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Resultados da Pesquisa
Item Microstructures, crystallographic fabric development and deformation mechanisms in natural hematite aggregates deformed under varied metamorphic conditions.(2012) Mendes, Mônica de Cássia Oliveira; Lagoeiro, Leonardo EvangelistaNaturally deformed hematite aggregates from 15 different iron ore mines located in Quadrilátero Ferrífero region, Brazil, were analyzed in order to verify the influence of increasing temperature and deformation intensity on their microstructural and textural aspects as well as the deformation mechanisms associated with the metamorphic conditions. The electron backscattered diffraction (EBSD) technique was applied in order to get qualitative and quantitative data concerning with microstructural parameters, crystallographic preferred orientation (CPO) and misorientation between hematite grains. The microstructures of these aggregates vary from randomly oriented hematite grains with approximately equant grains, to strongly oriented and elongated grains following the increase in deformational and metamorphic polarity toward east in the region. In the low deformation domain (western region) the deformation mechanisms are typically microfracturing and dissolution precipitation creep for magnetite rich aggregates. In the high-strain domain (eastern region), the deformation is accommodated by a combination of basal intracrystalline slip (c) () and grain boundary sliding, with rotation around hematite [c] axis. No evidences for recrystallization processes in these aggregates can be supported by our results, probably due to the superposition of subsequent processes.Item Crystallographic fabric development along a folded polycrystalline hematite.(2008) Morales, Luiz Fernando Grafulha; Lagoeiro, Leonardo Evangelista; Endo, IssamuDetailed analyses of microstructures and crystallographic preferred orientations (CPOs) of hematite rocks were conducted in samples of polycrystalline hematite around a tight fold in the Quadrilátero Ferrífero region, southeastern Brazil. Grain size is dominantly very fine in all samples (z15–30 mm), with a slight increase toward the hinge. Grain aspect ratio increases substantially toward the hinge, from an average of 2 in the limb to 9 in the hinge. Distribution patterns of [0001] axes and poles of planes {1010}, {1120} and {1014} suggest that intracrystalline slip operate on the basal plane along the direction. The distribution of the poles of prismatic planes parallel to the foliation of reference frame indicate that the all the symmetric -slip directions of hematite crystals were equally efficient during activation of basal intracrystalline slip. Increasing aspect ratio is accompanied by CPO intensification toward the hinge, where intensification was aided during deformation by bulk rotation of the hematitic plates and possibly by some grain boundary sliding. Such CPO intensification with the increase of aspect ratio toward the hinge is used to infer that the fold developed by flexural flow.