Glaciation-induced radionuclide mobility from the Kiggavik uranium deposits: natural analogues for geological disposal of nuclear waste
Notice bibliographique
Résumé
Safe and effective disposal of Used Nuclear Fuel (UNF) within a Deep Geological Repository (DGR) must isolate and contain UNF from the biosphere for ~1 Ma. This time period is long enough for several glacial cycles to elapse; it is therefore important to understand how glaciation-related processes such as erosion and subsurface fluid infiltration may impact a DGR. Studying the history of uranium (U) minerals from U deposits, which have been impacted by Pleistocene glaciation, provides a natural analogue to investigate the potential impacts of glaciation on a DGR over Ka-Ma timescales.               Uranium deposits in the Kiggavik region, Nunavut, Canada occur from surface to a depth of ~500m (comparable to depths of proposed DGRs) and have been impacted by multiple post-depositional fluid events and glacial cycles. Uranium minerals comprising uraninite, coffinite, brannerite, and U-Th-Zr silicates are hosted by illite (clay) and hematite altered metasedimentary and granitic rocks. Most U minerals (U1+U2) yield ~1.55-0.3 Ga U-Pb ages indicating they have remained in-situ since before the emergence of dinosaurs despite experiencing multiple fluid infiltration events.A smaller subset of U minerals (U3) shows stronger evidence of remobilization. U3 minerals are concentrated along redox fronts developed between geothite-bearing oxidized and bleached (clay-dominated) host rocks. These redox boundaries occur within ~5 cm of U1/U2 minerals, and are strongly associated with open fractures and porous veins. U3 minerals have 235U/207Pb ages of >0.6-65 Ma, providing minimum ages of complete recrystallization and potential large-scale radionuclide release.Uranium-thorium disequilibrium geochronology indicates widespread leaching of soluble decay-chain isotopes, corresponding to smaller-scale release of radionuclides. This has occurred sporadically between 34-494 Ka, with major episodes correlating with periods of rapid climate change during glaciation. Oxygen and hydrogen stable isotopic values of Illite associated with U3 indicate isotopic exchange with high-latitude meteoric fluids (i.e. snow/glacial melt).                 The history of U mobility in the Kiggavik region indicates oxidized glacial-derived fluids may infiltrate ≥500m into the subsurface along open fractures and mobilize radionuclides. This mobility occurs cumulatively over multiple glacial cycles and corresponds with ages of climate-induced perturbations to overlying ice sheets. Although longer distance transport from the system cannot be ruled out, the proximity of U3 to U1/U2 mineralization suggests overall transport distances are short (several cm), and geochronology indicates transport timescales are long (10’s-100’s Ka). Interactions with minerals present in both metasedimentary and granitic host rocks such as illite clay, U-oxides, and Ti-oxides have effectively restricted radionuclide mobility to rates millions of times slower than glacial movement over timescales comparable to human evolution.
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Prédiction distillée sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Apprise à partir de 10 348 étiquettes directes de Codex et de 10 348 étiquettes directes de Gemma. Le mode candidate est l'union des têtes enseignantes seuillées; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont ni des étiquettes humaines ni des étiquettes directes de modèles de pointe.
Scores Codex et Gemma par catégorie
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,001 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,001 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
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