Ion microprobe and ID‐TIMS U–Pb dating on zircon grains from leg 173 amphibolites: evidence for Permian magmatism on the West Iberian margin
Bibliographic record
Abstract
Abstract In this paper, we report evidence for Permian magmatism at the ocean–continent transition zone of the West Iberian margin, by dating magmatic intrusion of amphibolite precursors drilled at site 1067 during ODP leg 173. The P–T conditions recorded by the amphibolites indicate that the latter was emplaced at the bottom of a 25‐km‐thick crust. Subhedral to rounded and colourless zircon grains were obtained from samples at the base of the cored section. ID‐TIMS dating on these zircon grains yielded a lower intercept age of 247 ± 5 Ma and a poorly defined upper intercept around 2 Ga. In situ dating of single zircons by ion‐microprobe (CAMECA IMS 1270) provided an age of 246 ± 5 Ma. This Permian age is interpreted as a minimum estimate for the emplacement of the gabbroic melts at the base of the Hercynian crust during the early stage of rifting between the Iberia–Newfoundland conjugate margins.
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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 | 0.000 | 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".