Permian to Cretaceous polymetamorphic evolution of the Stewart River region, Yukon‐Tanana terrane, Yukon, Canada:<i>P–T</i>evolution linked with<i>in situ</i>SHRIMP monazite geochronology
Bibliographic record
Abstract
Abstract Textural relationships and the trace element chemistry of accessory minerals and garnet can provide the linkage betweenin situSHRIMP ages and quantitative pressure–temperature data that is required to decipher complex polymetamorphic and polydeformational histories. Application of these methods to lower amphibolite facies rocks of the Stewart River area, Yukon (Canada) yields robust new constraints on the tectonic evolution of central Yukon Tanana Terrane (YTT). A TIMS U/Pb titanite age of 365–350 Ma is interpreted to date low‐Pmetamorphism (M1) and D1 deformation associated with arc plutonism above an east‐dipping subduction zone. Monazite inclusions in garnet porphyroblasts record a transition from low to high pressure (∼9 kbar and 600 °C) atc. 239 Ma. These data help to establish ac. 260–240 Ma tectonometamorphic event (M2–D2) reflecting intra‐arc thickening during west‐dipping subduction of Slide Mountain Ocean. Another transition from low‐ to high‐P(M3–D3; 7.8 kbar and 595 °C), dated byc. 195–187 Ma monazite, is interpreted to reflect the change from regional contact metamorphism during arc plutonism to internal duplication of YTT during initial collision of YTT with the North American craton. The Mt Burnham (north‐eastern) region records a different history because of its proximity to later plutons and its late exhumation via extensional faulting. Monazite growth at 146 Ma dates ∼9 kbar metamorphism (M4), interpreted to reflect a previously unrecognized period of plutonism associated with auriferous quartz veins in the Klondike region. Monazite growth at 114–107 Ma reflects low‐P(<4.6 kbar) contact metamorphism (M5) accompanying regional plutonism and extension.
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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 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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".