Hydrological implications of 234U/238U disequilibria observed along pressure dissolution discontinuities in deep Mesozoic limestone formations of the Eastern Paris basin
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Bibliographic record
Abstract
Borehole core samples from the deep, low-permeability Mesozoic formations surrounding the target argilite layer of the Meuse/Haute-Marne experimental site of the French agency for nuclear waste management -ANDRAwere analyzed for their uranium isotopic abundance. This study attempts to decipher the history and the processes governing the mobility of uranium in such geological settings by means of precise measurements of the (U/U) activity ratio. Limestone zones characterized by pressure dissolution structures (stylolites or dissolution seams) display systematic (U/U) disequilibria: i) the material within the seams shows a deficit of U over U ((U/U) down to 0.80) and ii) the surrounding carbonate matrix is characterized by an activity ratio greater than unity (up to 1.05). These results highlight a discret, centimetric-scale uranium remobilization in the limestone formations along these sub-horizontal seams during the last 1-2 Ma and, consequently, active water/rock interaction processes since fractionation of U vs U necessary involves exchanges at the water/rock interface and migration via interstitial fluid. The nature and the modalities of the driving processes responsible for these disequilibria are not unequivocal, but different scenarios can be put forward to explain the U-remobilization observed: 1) late epidiagenetic processes associated to the presence of pressure dissolution structures, or 2) preferential fluid circulation along the stylolitic pathway. The major consequences in terms of the conceptual modeling of the hydrology behavior of the formations and, obviously, on the site performance assessment, are discussed. * Corresponding author. Now at CEREGE, Europole de l'Arbois, BP 80, 13 545 Aix-en-Provence Tel: +33 (0) 4 42 97 15 11 E-mail address: m106050@er.uqam.ca
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Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 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 it