地質学雑誌
Online ISSN : 1349-9963
Print ISSN : 0016-7630
ISSN-L : 0016-7630
Observations of three-dimensional microstructures of symplectite minerals in the Horoman Peridotite Complex using a high-resolution X-ray CT system at Spring-8
Tomoaki MorishitaAkira TsuchiyamaTsukasa NakanoKentaro Uesugi
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2003 年 109 巻 2 号 p. III-IV

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X-ray computerized tomography (CT) has become a powerful tool for completely non-destructive examination of the interiors of geological objects. An X-ray CT image is a map of the spatial distribution of values related to the linear attenuation coefficient (LAC), which depends on mass density, chemical composition and incident X-ray energy (Nakano et al., 2000). In this report we show the application of this method to a symplectite consisting of irregular fine-grained orthopyroxene, clinopyroxene and spinel from the Horoman peridotite, Japan. The symplectite in the Horoman peridotites is interpreted to be of pyropic garnet origin. Textural characteristics of symplectite from the Horoman complex will therefore provide opportunities to investigate the phase transition from garnet to spinel lherzolite. We imaged symplectites using a highresolution X-ray CT system at SPring-8 (Uesugi et al., 2001) with a monochromatic X-ray beam of 15 keV (Fig.1). Brighter regions on the CT images correspond to higher values of LAC. Three-dimensional structures of the symplectites were obtained from 1018 slices of the CT images with 1000 × 1000 matrix (Figs.2, 3). The voxel size is 0.5 μm × 0.5 μm × 0.5 μm, and the effective spatial resolution is about 1 μm. Clusters of orthopyroxene, clinopyroxene and spinel in the symplectites were clearly identified using the contrast in the CT images, which coincided with the theoretical LAC values of these minerals (Fig.1).
Acknowledgements: The authors thank to Greg Yaxley to improve the English of the manuscript. Constructive review by Susumu Ikeda improved the manuscript.

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© The Geological Society of Japan
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