Clays and Clay Minerals, Vol. 55, No. 5, 453–466, 2007.
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Authors
Kameda, Jun
Miyawaki, Ritsuro
Drits, Victor A.
Kogure, Toshihiro
Issue Date
2007
Type
Article
Language
Keywords
Periodicals , Geology , EBSD , HRTEM , Illite , Morphology , Polytype , Stacking Disorder
Alternative Title
Polytype And Morphological Analyses Of Gu¨mbelite, a Fibrous Mg-rich Illite
Abstract
Polytypism in gu¨mbelite and its relationship to the fibrous or ribbon-like morphology exhibited by this Mg-rich illite were investigated by powder X-ray diffraction (XRD), electron back-scattered diffraction (EBSD) and transmission electron microscopy (TEM). Comparison between the XRD pattern from oriented fibers using a conventional powder diffractometer and a randomly oriented pattern using a Gandolfi camera suggested that 2M2 is dominant but other polytypes belonging to subfamily A also exist, and that the fiber axis of gu¨mbelite is parallel to <110> in 2M2, <110> in 2M1, and <100> in 1M. The EBSD analyses confirmed these crystallographic directions directly from individual crystals. Electron diffraction and high-resolution TEM showed that twinning and intergrowths of various polytypes including both subfamilies are common in a single crystal and that the two types of rotations [2n60º and (2n+1)60º] between adjacent layers are often randomly mixed at the monolayer level. The data suggest that high densities of twinning and intergrowths account for the origin of the fibrous morphology along <110> for 2M1 and 2M2 polytypes. Volume restriction in a confined vein space may also play a role.
Description
Clays and Clay Minerals, Vol. 55, No. 5, 453–466, 2007. Polytype And Morphological Analyses Of Gu¨mbelite, a Fibrous Mg-rich Illite. Jun Kameda; Ritsuro Miyawaki; Victor A. Drits; Toshihiro Kogure. DOI: 10.1346/CCMN.2007.0550501. Copyright © 2007, The Clay Minerals Society.
Citation
Clays and Clay Minerals, Vol. 55, No. 5, 453–466, 2007.
Publisher
The Clay Minerals Society
License
Copyright © 2006-2018, The Clay Minerals Society