Les brèches associées aux gisements d'uranium de type discordance du bassin Athabasca (Saskatchewan, Canada)
Bibliographic record
Abstract
Unconformity-type uranium deposits in the Athabasca Basin (Canada) are commonly hosted and surrounded by breccia bodies in quartzose sandstones. In order to understand the mechanisms of breccia formation and the ir significance for the genesis of uranium deposits, the breccias associated with U mineralizations of the Shea Creek prospect and Sue C open pit, and with the Y-REEU mineralization of the Maw Zone were studied. Structural mapping and 3D modeling evidence the control of breccia geometries by reverse faults that are graphite-rich in the basement. The study of mineral paragenesis and calculations of U-Pb chemical ages at Shea Creek reveal 3 breccia phases with sudoite-dravite, Fe-chlorite and hematite-siderite cements. These breccias developed over more than 1 Ga respectively during 3 stages of tectonic reactivations and/or basin uplift main! y between 1.52 and 1.25 Ga during the main event of primary uranium deposition and at about 900 and 350 Ma during phases of uranium remobilization. The breccias coeval with the genesis of the primary mineralization developed in 3 stages characterized by fractal analysis of fragment shapes expressing their degree ofmaturity. The first stage of breccia formation has been triggered by a reactivation of graphite-rich reverse faults inducing localized tectonic fracturing in the core offaults and widespread hydraulic fracturing in early silicified zones. The second stage corresponds to quartz dissolution due to the vertical circulation of a basement t1uid undersaturated relative to silica in fractured sandstones. Calculated minimum t1uid/rock ratios are very high with values of3,000 at the Maw Zone and 38,000 in the Sue « zones à boules» ret1ecting the decrease of dissolution intensity with the increase of distance to the unconformity. The minimum volume of basement t1uids that have circulated through the breccias is about 1 km3 ? Mass balance calculations show an input of U, V, Mg, B, Al, K, Bi, Ni, Co, Mo, As, S, W, Zn, Y and REE, in accordance with the new formation of illite, Mg-rich sudoite and dravite and with the polymetallic sandstone-hosted mineralization.The third stage is expressed by gravity-driven collapse phenomenons resulting from the cavities created by quartz dissolution. In « zones à boules » developed in the core of faults, it is the tectonic contraction that progressively closed the open spaces formed by quartz dissolution. Volume Joss values reach 90 % in zones of intense dissolution close to the unconformity. In steeply dipping fault zones, collapse propagated up to more than 250 rn above the unconformity as observed at the Maw Zone, like in a karst. Uranium deposition induced by mixing of the reducing basement fluid undersaturated relative to quartz (> 250°C) with diagenetic oxidizing basin fluids (< 240°C) occurred during about severa! million years, simultaneously with quartz dissolution providing the space needed to form the massive mineralizations.
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.003 | 0.003 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.002 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.003 | 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".