Radiation induced defects in quartz and applications to the Arrow uranium deposit in the Athabasca basin, Saskatchewan
Notice bibliographique
Résumé
This thesis presents the results of a combined electron paramagnetic resonance (EPR) and cathodoluminescence (CL) study of quartz from the Arrow uranium deposit and its surrounding areas in the southwest margin of the Athabasca basin, Saskatchewan. Detailed EPR analyses of quartz samples from both the basement and the overlying sandstones revealed the presence of a host of different paramagnetic defects (i.e., oxygen vacancy electron centers and silicon vacancy hole centers) previously observed in quartz from the eastern part of the Athabasca basin. The silicon vacancy hole centers were previously shown to have formed from bombardment of alpha particles emitted from the decay series of ^238U, ^235U and ^232Th. Characteristic spectral differences have been observed between quartz from different lithologies, such as the lack of the H'_3 centers in basement quartz. Thermal annealing and neutron irradiation experiments suggest that these spectral differences are linked with different diamagnetic precursors, which might be related to growth defects formed during crystallization.\n\nOf the four different types of drusy quartz (translucent, milky, pink and smoky) identified in the basement at the Arrow deposit, only the pink and smoky types contain significant concentrations of paramagnetic defects. Blue quartz in metasedimentary rocks from the basement is characterized by low concentrations of radiation induced defects, suggesting no pervasive uranium-bearing fluids in the basement. Quartz of high EPR intensities is restricted to ~7 m from mineralized areas, confirming the structurally controlled nature of uranium-bearing fluids. CL imaging and spectral analyses also confirmed the EPR results that the translucent and milky types of quartz contain only low levels of radiation induced defects. Smoky quartz with elevated radiation induced defects as revealed by EPR, on the other hand, is characterized by characteristic CL halos and patches associated with uranium-rich minerals and often features well-developed continuous rims, which cross-cut the growth zoning of quartz crystals and apparently suggests remobilization of uranium after quartz crystallization. Pink quartz with elevated radiation induced defects as revealed by EPR does not have the characteristic CL halos, patches or continuous rims, suggesting a homogeneous distribution of radiation induced defects in this type of quartz and pointing to their formation during crystallization from a uranium-bearing fluid. This result, combined with the common occurrence of pink quartz in veins and breccias associated with dravite alteration, suggests that this uranium-bearing fluid might represent the main mineralization event at the Arrow deposit.\n\nThe intensities and distribution of alpha-particles-induced defects in detrital quartz close to the sandstone-basement unconformity suggest that uranium-bearing fluids at the Arrow deposit are restricted to the areas immediately above the basement-hosted mineralization. This distribution, together with the low radiation induced defects in detrital quartz, suggests that the basinal fluid along the sandstone-basement unconformity at the Arrow deposit, if present, was low in uranium, which was mainly transported in basement fluids. The present results further support the suggestion that combined EPR and CL analyses of radiation induced defects in quartz is a powerful tool for the exploration of uranium deposits in the Athabasca basin.
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Comment cette classification a été obtenuedéplier
Prédiction machine sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Le volet Gemma est une étiquette directe du modèle pour chaque travail de la base, lue sur la notice réduite au titre. Le volet Codex est un classifieur appris des 10 348 étiquettes directes de Codex et calibré sur les taux pondérés de l'échantillon; les champs sans appui suffisant ne portent aucun appel Codex. Le mode candidate est l'union des deux volets; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont pas des étiquettes humaines.
Scores du classifieur distillé par catégorie (deux têtes)
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,001 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,002 | 0,004 |
| Études des sciences et des technologies | 0,002 | 0,001 |
| Communication savante | 0,001 | 0,000 |
| Science ouverte | 0,001 | 0,001 |
| Intégrité de la recherche | 0,001 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,002 | 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
machine, non validéePrédiction automatique; un appel candidat d’une seule source (Gemma direct ou Codex distillé), pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».