Proof of Uranyl Deposition in Unconformity-Related Uranium Deposits, Athabasca Basin, Canada: Evidence from Synchrotron XAS and XPS Analyses of Hematite
Bibliographic record
Abstract
Abstract Except for the recently discovered stable U4+ chloride complex under reduced conditions at high temperatures, genetic models for the formation of uranium deposits had almost invariably invoked the pivotal roles of soluble U6+ species for the transport of uranium in fluids and their reduction to sparingly soluble U4+ as the deposition mechanism. However, the questions of when and how this reduction occurred in most uranium deposits, such as those in the Athabasca basin, Saskatchewan, Canada, are often not clear. The unconformity-related uranium deposits in the Athabasca basin are commonly accompanied by extensive and intensive alteration halos, including hematite-rich alteration or hematitization. Previous U L3-edge X-ray absorption near-edge structure (XANES) studies of uranium-bearing fluid inclusions and thermodynamic modeling demonstrated uranium transport as uranyl (UO22+) species in hypersaline fluids in the Athabasca basin. Electron microprobe analyses reveal that hematite inclusions in quartz overgrowths, as well as some disseminated hematite in clay mineral (illite-chlorite) matrices, in both orebodies and associated alteration halos from five uranium deposits (Arrow, Cigar Lake, Key Lake, McArthur River, and Phoenix) in the Athabasca basin contain elevated contents of uranium (up to 2.16 wt.% UO3). Synchrotron U L3-edge X-ray absorption spectroscopy (XAS) and U 4f X-ray photoelectron spectroscopy (XPS) analyses show that uranium in hematite occurs dominantly as the uranyl species, providing unambiguous evidence for direct uranyl deposition in the Athabasca basin. However, direct uranyl deposition with hematite during a single episode of hydrothermal alteration can account for only low-grade uranium mineralization. High-grade uranium deposits in the Athabasca basin required multiple episodes of hydrothermal alteration and/or other deposition mechanisms, such as those related to reduction.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.002 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".