Please use this identifier to cite or link to this item: http://www.repositorio.ufop.br/jspui/handle/123456789/8217
Title: Particle morphological evolution during the conversion of I/S to Illite in lower cretaceous shales from Sergipe-Alagoas basin, Brazil.
Authors: Varajão, Angélica Fortes Drummond Chicarino
Meunier, Alain
Issue Date: 1995
Citation: VARAJÃO, A. F. D. C.; MEUNIER, A. Particle morphological evolution during the conversion of I/S to Illite in lower cretaceous shales from Sergipe-Alagoas basin, Brazil. Clays and Clay Minerals, v. 43, n.1, p. 14-28, 1995. Disponível em: <https://link.springer.com/article/10.1346/CCMN.1995.0430103>. Acesso em: 20 de jun. 2017.
Abstract: The illitic end of mixed-layer illite-smectite series (I/S) in shales from Lower Cretaceous Barra de Itifiba Formation, Sergipe-Alagoas basin, was examined with X-ray powder diffraction (XRD) and transmission electron microscopy (TEM). A mathematical decomposition of XRD patterns shows different I/S and illite populations. All the samples contain ordered (R = 1) I/S, poorly crystallized illite (PCI) and well crystallized illite (WCI). A randomly interstratified (R = 0) I/S was also identified in a fractured zone at 1020 m. The percentage of expandable layers in ordered I/S decrease progressively from 20% to 10%. TEM observations show a continuous change in morphology between two basic particle shapes: elongated (lath) and isometric. The size and morphology of particles change with increasing depth. The proportion of laths decreases while isometric particles become predominant. However, both particle types continuously grow and enrich the larger size fraction. The growth process is driven by a mass transfer from the dissolving small particles of predominantly I/S (R = 1) composition to the larger (more illitic) lath and isometric ones. The proportion of lath-shaped particles decreases with depth indicating that the more stable population upon increased burial is the isometric well crystallized illite (WCI) particles. Very large laths are observed in the fault zone where conditions may favor faster growth processes.
URI: http://www.repositorio.ufop.br/handle/123456789/8217
metadata.dc.identifier.uri2: https://link.springer.com/article/10.1346/CCMN.1995.0430103
metadata.dc.identifier.doi: https://doi.org/10.1346/CCMN.1995.0430103
ISSN: 1552-8367
Appears in Collections:DEGEO - Artigos publicados em periódicos

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