Garnet crystallization mechanisms and localized polymetamorphism in the southwestern Meguma Terrane, Nova Scotia, Canada
Bibliographic record
Abstract
Abstract We present data on the pressure and temperature ( P–T ) conditions experienced by metamorphic rocks of the Meguma Terrane, Nova Scotia, Canada, also utilizing three‐dimensional microstructural data on one sample to better constrain the mechanisms that controlled garnet crystallization. Inverse and forward thermodynamic modelling place peak P–T conditions in the southwestern Meguma Terrane at ~650°C and 4.5 kbar. Interpretation of these results with petrographic observations and previous P–T constraints across the terrane suggests that amphibolite facies metamorphism occurred during the Devonian Neoacadian orogeny (406–388 Ma). Integration of quantitative 3D textural data with an estimated metamorphic heating rate of <5°C/Myr is consistent with amphibolite facies metamorphism resulting from tectonic loading during the Neoacadian orogeny, though the exact nature of the orogeny is still not well understood. Further, the intrusion of granitic plutons into the Meguma metasediments at 373 Ma likely locally drove metamorphic recrystallization (polymetamorphism). The 3D size, shape, and location of garnet crystals in one sample reveal that the rate‐limiting step for garnet crystallization was likely the diffusion of aluminium through the intergranular matrix at length scales less than the mean nearest neighbour distance between garnet crystals. Nucleation was aided by epitaxial overgrowth onto a muscovite substrate, though it appears there may have been a decoupling between minerals providing a substrate and those providing nutrients during garnet growth.
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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) | 0.000 | 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) | 0.016 | 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".