A comparison of properties of clay minerals in isalteritic and in degraded facies.
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Data
2013
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Resumo
The mineralogical, geochemical and micromorphological features of an isalteritic
clay facies, which originated from weathering of an anorthosite, were compared to those of clay
facies derived from the degradation of a bauxite developed from the same rock. The isalteritic clay
was formed by the hydrolytic alteration of plagioclase, whereas the degraded clays were formed by
decomposition of gibbsite and neoformation of kaolinite. This resilification process resulted from the
reintroduction of silica via the oscillation of the phreatic level and/or the decomposition of organic
matter on the surface. The degradation process was gradual and yielded two different facies:
(a) degraded clays with almost total decomposition of gibbsite, and (b) degraded clays with gibbsite
nodules. Morphologically, the isalteritic clays differ from the degraded clays because they contain
larger hexagonal and pseudo-hexagonal crystals. The degraded clays have more irregular crystal
shapes, ranging from laths to anhedral shapes.
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Isalteritic clay facies, Degraded facies, Anorthosite, Bauxite deg
Citação
OLIVEIRA, F. S. de et al. A comparison of properties of clay minerals in isalteritic and in degraded facies. Clay Minerals, v. 48, p. 697-711, 2013. Disponível em: <https://www.cambridge.org/core/journals/clay-minerals/article/comparison-of-properties-of-clay-minerals-in-isalteritic-and-in-degraded-facies/31FF5043B56CC834E4983BD1CA462977#>. Acesso em: 20 de jun. 2017.