Orientational mapping of minerals in Pierre shale using X-ray diffraction tensor tomography

Shales have a complex mineralogy with structural features spanning several length scales, making them notoriously difficult to fully understand. Conventional attenuation-based X-ray computed tomography (CT) measures density differences, which, owing to the heterogeneity and sub-resolution features i...

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Bibliographic Details
Published in:IUCrJ 2021-09, Vol.8 (5), p.747-756
Main Authors: Murer, Fredrik K, Madathiparambil, Aldritt Scaria, Tekseth, Kim Robert, Michiel, Marco Di, Cerasi, Pierre, Chattopadhyay, Basab, Breiby, Dag W
Format: Article
Language:English
Subjects:
Attenuation
Chemical Sciences
Clay minerals
Clinochlore
Computed tomography
Crystal structure
Crystallites
Crystals
CT imaging
Diffraction
Heterogeneity
high-density inclusions
Inclusions
inorganic materials
Medical imaging
Mineralogy
Nondestructive testing
Orientation
orientation mapping
Pyrite
Research Papers
shales
Structure
Tensors
Tomography
X-ray diffraction
X-rays
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Summary:Shales have a complex mineralogy with structural features spanning several length scales, making them notoriously difficult to fully understand. Conventional attenuation-based X-ray computed tomography (CT) measures density differences, which, owing to the heterogeneity and sub-resolution features in shales, makes reliable interpretation of shale images a challenging task. CT based on X-ray diffraction (XRD-CT), rather than intensity attenuation, is becoming a well established technique for non-destructive 3D imaging, and is especially suited for heterogeneous and hierarchical materials. XRD patterns contain information about the mineral crystal structure, and crucially also crystallite orientation. Here, we report on the use of orientational imaging using XRD-CT to study crystallite-orientation distributions in a sample of Pierre shale. Diffraction-contrast CT data for a shale sample measured with its bedding-plane normal aligned parallel to a single tomographic axis perpendicular to the incoming X-ray beam are discussed, and the spatial density and orientation distribution of clay minerals in the sample are described. Finally, the scattering properties of highly attenuating inclusions in the shale bulk are studied, which are identified to contain pyrite and clinochlore. A path forward is then outlined for systematically improving the structural description of shales.
ISSN:2052-2525
2052-2525
DOI:10.1107/S205225252100587X