Polytype and morphological analyses of Gümbelite a fibrous Mg-rich illite
Kameda, Jun (The University of Tokyo. Department of Earth and Planetary Science)
Miyawaki, Ritsuro (The National Science Museum. Department of Geology)
Drits, Victor A. (Russian Academy of Science. Geological Institute)
Kogure, Toshihiro (The University of Tokyo. Department of Earth and Planetary Science)

Data:	2007
Resum:	Polytypism in gümbelite 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 2M is dominant but other polytypes belonging to subfamily A also exist, and that the fiber axis of gümbelite is parallel to <110> in 2M, <110> in 2M, 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 [2n60° and (2n+1)60°] 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 2M and 2M polytypes. Volume restriction in a confined vein space may also play a role.
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Llengua:	Anglès
Document:	Article ; recerca ; Versió publicada
Matèria:	EBSD ; HRTEM ; Illite ; Morphology ; Polytype ; Stacking disorder
Publicat a:	Clays and Clay Minerals, Vol. 55, Núm. 5 (2007) , p. 453-466, ISSN 1552-8367

DOI: 10.1346/CCMN.2007.0550501

14 p, 2.2 MB  Accés restringit a la UAB

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