SHRIMP U-Pb ages and REE patterns for zircon from an anatectic Variscan two-mica granite from the Bemposta Migmatite Complex (Central Iberian Zone)
Bibliographic record
Abstract
ABSTRACT The Variscan Bemposta Migmatite Complex (BMC) in northern Portugal (Central Iberian Zone) is a NE–SW-trending high-grade metamorphic core complex comprising upper-amphibolite- to lower-granulite-facies metapelites and metagreywackes of Ediacaran-Cambrian age and subordinate Ordovician orthogneisses showing evidence of intense migmatization. The available petrological data indicate that these rocks attained peak metamorphic conditions at the end of the first Variscan contractional deformation event (D1), followed an isothermal decompression path during D2 crustal extension, and underwent subsequent retrogression during D3 shearing. The whole BMC complex hosts numerous concordant intrusive bodies (sheets several meters thick) of syn-D2 two-mica granites, genetically linked to the leucosomes, suggesting that the emplacement of these magmas was synchronous with core complex extension. U-Pb SHRIMP ages obtained from zircons from one of these syn-D2 tabular plutons (the Faia d'Água Alta granite) yielded a crystallization age of 324 ± 3 Ma, providing a good estimate for the age of the D2 anatectic event in the region.
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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 | 0.001 | 0.000 |
| 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".