The P–T path of eclogites in the St. Cyr klippe, Yukon, Canada: Permian metamorphism of a coherent high-pressure unit in an accreted terrane of the North American Cordillera
Bibliographic record
Abstract
The St. Cyr klippe, part of the Yukon–Tanana terrane in Yukon, Canada, preserves fresh and retrogressed eclogite hosted by quartzofeldspathic schists. Petrology, mineral chemistry and compositional zoning combined with isochemical phase equilibrium (pseudosection) modeling shows that eclogites followed a clockwise pressure–temperature path. An amphibolite facies, pre-eclogite stage (pre-Stage I) preceded early eclogite-facies conditions of about 16 kbar and 510 °C (Stage I) and the peak pressure (Stage II), which reached up to 20 kbar and 670 °C. The peak observed and modeled eclogite-facies assemblage is garnet, omphacite, Na-rich amphibole, phengite, quartz and rutile. Pseudosections were modeled for varying Fe 3+ contents, and Fe 3+ = 20 % of total Fe is found to best match the pyrope and grossular content observed in garnet. Retrogression back to amphibolite-facies conditions (Stage III) followed a clockwise path as temperature decreased during decompression without passing through the chlorite stability field. U-Pb SIMS (secondary ion mass spectrometry) dating and trace-element analysis of zircon shows that the protolith of the eclogites formed within the Yukon–Tanana terrane during early arc activity, between 364 and 380 Ma. The rocks were then subducted to mantle depths and metamorphosed to eclogite-facies conditions during the Late Permian, between 267 and 271 Ma. These medium-temperature eclogites are part of a coherent high-pressure (HP) terrane that was tectonically eroded from the Yukon-Tanana composite arc in a subduction zone environment.
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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 | 0.001 | 0.001 |
| 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".