Thermo-chronology of the Barlet metamorphic basement unit: evidence for a Stephanian thermal event linked to Sb mineralization in the Haut Allier, France
Bibliographic record
Abstract
A thermo-chronological analysis of the Barlet basement unit (French Massif Central) reveals a four-stage history. Peak metamorphism (650 °C and 7 kbar) was followed by retrograde growth of albite blasts and development of the main foliation at 600 °C, and chloritization of the ferromagnesian minerals. The third stage is a marked reversal of cooling, with recrossing of the biotite isograd and local reappearance of garnet at 450 °C. This thermal event, inferred to result from hot fluid infiltration, is also recognized in the adjacent basin of Langeac, where it gives rise to anomalous coal grades (recording 200 °C at 1 km). A Stephanian age for this event correlates with a regional thermal event recognized throughout the Variscan, where it has been linked to delamination of the continental crust. This work represents the first instance in the Massif Central that recognizes this event in the shallow basement itself. Final cooling is accompanied by extensive fluid-induced sericitization, starting immediately after the peak of the thermal event and continuing to temperatures inferred for Sb–As ore deposition. This continuum leads us to conclude that reheating-related silicate reactions and ore deposition are caused by the same fluid and related to the wider regional Variscan thermal event.
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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 | 0.002 | 0.001 |
| 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) | 0.001 | 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".