Prograde, peak, and retrograde <i>P–T</i> paths from aluminium in orthopyroxene: High‐temperature contact metamorphism in the aureole of the Makhavinekh Lake Pluton, Nain Plutonic Suite, Labrador
Bibliographic record
Abstract
Abstract Static heating during intrusion of the Makhavinekh Lake Pluton (MLP) caused replacement of garnet in the adjacent country rocks (Tasiuyak Gneiss) by coronal assemblages of orthopyroxene + cordierite. Thermometry based on Al solubility in orthopyroxene, applied to relict garnet and neighbouring orthopyroxene, preserves a temperature gradient from 700 to 900 °C at distances between 5750 and 20 m from the intrusion, reaffirming the robustness of this thermometry technique. Intracrystalline and intergranular variations of Al zoning in orthopyroxene are well‐preserved, suggesting that little diffusional modification of Al growth zoning occurred. Maximum Al2O3 in orthopyroxene ranges from c. 2.0 wt% at 5750 m from the intrusion to a maximum of 4.3 wt% at the contact. Individual orthopyroxene grains show decreasing Al from core to rim in samples < 500 m from the intrusion, while those at greater distances show an increase from core to rim. These features are interpreted with the aid of numerical models for conductive heat flow in the aureole. Coronas in samples close to the intrusion grew at high temperatures and along T‐t paths dominated by cooling, so maximum Al content in orthopyroxene in these samples occurs in the cores of grains that grew during the earliest stages of garnet consumption. In contrast, the corona‐forming reactions in rocks further from the contact proceeded along prograde heating paths, so maximum Al content in orthopyroxene occurs in the rims of grains that grew during the final stages of garnet consumption. These results document the ability of Al‐in‐orthopyroxene thermometry to preserve a detailed record of thermal histories in contact‐metamorphic granulites; they suggest that similar intracrystalline and intergranular variations of Al zoning in orthopyroxene in regional granulites may also preserve portions of both the prograde and peak‐T evolution.
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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 | 0.000 | 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".