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| Titel |
Combining micro-CT data and XRF spectra for advanced element analysis |
| VerfasserIn |
M. N. Boone, J. Dewanckele, V. Cnudde, G. Silversmit, K. Vandeputte, G. Ernst, L. Van Hoorebeke, L. Vincze, P. Jacobs |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250030316
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| Zusammenfassung |
| Micro-computed tomography (μCT) is a very powerful tool for analysing geo-materials.
However, this technique does not provide information about the elemental composition.
Different compounds of the material can be reconstructed and visualised based on
their attenuation coefficient, but cannot be identified. A combination of μCT data
with X-ray fluorescence (XRF) can provide this additional information. In XRF,
incident photons from the X-ray source are absorbed, ejecting an electron from
an inner shell of an atom. The resulting vacancies are filled in by electrons from
outer shells, emitting X-rays with an energy characteristic for the given atom. By
measuring this fluorescent spectrum, the chemical elements present in the material can
be determined. Based on the peak area of the XRF line, the concentration of the
corresponding element can be estimated. The combination of this technique with
μCT can be very valuable in the field of geo-sciences and other related research
domains.
In this study, two different applications of the combination of XRF and μCT will be
discussed. The first application obtains chemical information on the different compounds in
the inner part of a granite. This information cannot be measured directly with XRF, but can be
derived from the combined XRF spectra and μCT data. In the second application, the
chemical elements present in volcanic rock are analysed, providing information about their
origin.
For the first application, a Precambrian granite from China was scanned at the Centre for
X-ray Tomography of the Ghent University (UGCT) at high resolution (voxel size
less than 5 micrometer) and subsequently scanned with the Eagle III micro-XRF
scanner from the Ghent University X-ray Microspectroscopy and Imaging Group
(XMI). From the μCT-scan, a 3D volume was reconstructed, where the gray value of
a volume element (voxel) is proportional to the mass attenuation coefficient of
the concerned voxel. The μXRF imaging on the surface of the rock sample was
performed with a spatial resolution of 100 μm in vertical and horizontal direction.
Extraction of the elemental XRF line intensities for each pixel spectrum results
in 2D elemental images of the sample surface. Through segmentation of the 3D
volume, we were able to extend the information from this surface map to the whole
volume. With this extra information, the granite can be characterized in a more correct
way.
For the second application, a series of scoria and pumice, coming from the area west of
the Lac Pavin (lake in Auvergne, France), were scanned with the UGCT μCT-scanner. The
goal of this project is to distinguish different eruption facies, in particular the ‘red scoria’
layer, which is assumed to be the result of the most recent eruption in Western-Europe. Due
to the irregular form of the samples, measuring a surface map of the elements was almost
impossible. Therefore, only a global XRF-spectrum was taken with a Canberra X-PIPS
detector at the UGCT facility. Although this result does not allow an identification of
the different structures in the sample, knowledge of the abundance of chemical
elements in the fragments can help to identify and characterize different eruptions. |
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