Data/hora: 01/06/2024 08:48:54

Provedor de dados: | 42
País: | Brazil
Título: | Coexistence of halloysite and kaolinite: a study on the genesis of kaolin clays of Campo Alegre Basin, Santa Catarina State, Brazil
Autores: | Oliveira,Marisa T.G. de; Furtado,Sandra M.A.; Formoso,Milton L.L.; Eggleton,Richard A.; Dani,Norberto.
Data: | 2007-12-01
Ano: | 2007
Palavras-chave: | Kaolinite; Halloysite; Halloysite morphology; Kaolin; Weathering; Clay genesis.
Resumo: | Kaolin at Campo Alegre Basin, Santa Catarina State, Brazil was formed from alteration of volcanic acid rocks. Halloysite clays dominate the clay fraction of the matrix of the kaolin body, whereas a poorly crystalline kaolinite is abundant in veins. Some primary blocky structures have high amounts of illite, in one mine, but in general, only low contents of illite-smectite, illite, chlorite-vermiculite, vermiculite and quartz were identified in the clay fraction of the samples. Toward the top of the mines, hematite and lepidocrocite appear in horizontal red and ochre colored levels and the amount of kaolinite increases compared to halloysite. The vertical zoning of alteration levels, the changes in mineralogy, the positive correlation between depth and Cation Exchange Capacity of the clays, the preservation of different types of rock textures in the kaolin bodies, the dominant tube morphology of the halloysite clays indicate a supergene genesis for the deposits. Criteria to distinguish between supergene and hypogene kaolin are discussed. Transmission Electron Microscopy of the cross sections of halloysite tubes showed polygonal forms that are ascribed to be transitional between kaolinite and halloysite. It is proposed that some of the kaolinite of these deposits be inherited from the dehydration of halloysite tubes.
Tipo: | Info:eu-repo/semantics/article
Idioma: | Inglês
Identificador: | http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0001-37652007000400008
Editor: | Academia Brasileira de Ciências
Relação: | 10.1590/S0001-37652007000400008
Formato: | text/html
Fonte: | Anais da Academia Brasileira de Ciências  v.79 n.4 2007
Fonte: | info:eu-repo/semantics/openAccess