Major and trace element mapping of garnet: Unravelling the conditions, timing and rates of metamorphism of the Snowcap assemblage, west‐central Yukon
Bibliographic record
Abstract
Abstract Garnet crystallization has been simulated in the MnNCKFMASHT model system using a simple nucleation and growth scenario, calibrated with three‐dimensional garnet crystal size distribution data as well as garnet compositional data obtained by electron probe micro‐analysis and laser ablation inductively coupled plasma mass spectrometry. Results indicate wide‐spread Barrovian‐type metamorphism for garnet‐zone rocks from the Snowcap assemblage along a hairpin‐shaped pressure–temperature loop with garnet growth from ~515°C and 4 kbar to metamorphic peak conditions of ~600°C and 6 kbar. Lu–Hf garnet‐whole geochronology points to initial garnet growth at c . 192.2 ± 4.7 Ma. Sm–Nd garnet–whole‐rock geochronology applied to a sample with garnet rims enriched in Sm indicates that the metamorphic peak conditions have been attained at c . 172.9 ± 2.4 Ma. Older garnet growth at c . 245.3 ± 0.8 Ma during a low‐ P –high‐ T event has been preserved as garnet cores separated from the Jurassic garnet rims by a sharp microstructural and compositional discontinuity. These polyphase garnets are restricted to Mn‐rich metapelitic lithologies. Trace element zoning in the outermost ~50 μm thin segments of the Early Triassic garnet cores reflects a short garnet growth episode in the presence of melt at peak conditions of ~710°C and 2.5 kbar, supported by phase equilibrium and diffusion geospeedometry calculations. Diffusion simulations across the interface between the Early Triassic garnet core and the Jurassic garnet rim indicate that the Barrovian‐type metamorphism during the Jurassic lasted for 20–25 Myr, in line with the radiometric data.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| 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) | 0.002 | 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 teacher head, 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".