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| Titel |
234U/238U Disequilibrium along stylolitic discontinuities in deep Mesozoic limestone formations of the Eastern Paris basin: evidence for discrete uranium mobility over the last 1–2 million years |
| VerfasserIn |
P. Deschamps, C. Hillaire-Marcel, J.-L. Michelot, R. Doucelance, B. Ghaleb, S. Buschaert |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1027-5606
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| Digitales Dokument |
URL |
| Erschienen |
In: Hydrology and Earth System Sciences ; 8, no. 1 ; Nr. 8, no. 1, S.35-46 |
| Datensatznummer |
250005383
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| Publikation (Nr.) |
 copernicus.org/hess-8-35-2004.pdf |
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| Zusammenfassung |
| The (234U/238) equilibrium state of borehole core samples
from the deep, low-permeability limestone formations surrounding the target argilite layer
of the Meuse/Haute-Marne experimental site of the French agency for nuclear waste
management -ANDRA- (Agence nationale pour la gestion des déchets radioactifs) was examined
to improve understanding of naturally occurring radionuclide behaviour in such geological
settings. Highly precise, accurate MC-ICP-MS measurements of the
(234U/238U) activity ratio show that limestone samples
characterised by pressure dissolution structures (stylolites or dissolution seams) display
systematic (234U/238U) disequilibria, while the pristine
carbonate samples remain in the secular equilibrium state. The systematic feature is
observed throughout the zones marked by pressure dissolution structures: (i) the material
within the seams shows a deficit of 234U over 238U
((234U/238U) down to 0.80) and (ii) the
surrounding carbonate matrix is characterised by an activity ratio greater than unity
(up to 1.05). These results highlight a centimetric-scale uranium remobilisation in the
limestone formations along these sub-horizontal seams. Although their nature and
modalities are not fully understood, the driving processes responsible for these
disequilibria were active during the last 1–2 Ma.
Keywords: uranium isotopes, multiple-collector ICP-MS, waste management, remobilisation,
migration |
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