Relationship of amphibole composition to host-rock geochemistry: the A-type gabbro-granite Wentworth pluton, Cobequid shear zone, eastern Canada
Bibliographic record
Abstract
The Wentworth pluton is the most alkaline of a series of Late Devonian metaluminous to mildly peralkaline plutons in the Cobequid shear zone. It includes numerous granitoid bodies of slightly differing composition, which may contain sodic, sodic-calcic or calcic amphiboles. This study examines the relative importance of host rock composition including volatiles, f O2, and temperature in controlling the type of amphibole present. Electron microprobe analyses and back-scattered electron images were used to characterize the amphiboles and whole-rock geochemical analyses were made from the host granites. Magmatic sodic amphiboles are arfvedsonite, ferrorichterite and katophorite. Ferrowinchite and riebeckite developed by subsolidus oxidation reactions with loss of fluorine. Sub-solidus changes in Fe-Ti oxides make reliable estimation of f O2 difficult. Regionally, sodic amphiboles are found only in the Wentworth pluton, suggesting the importance of peralkaline geochemistry and perhaps higher temperature as a result of voluminous gabbro in the pluton. However, the presence of sodic or calcic amphibole in granite with >73% SiO2 in the Wentworth pluton shows no systematic difference with either host-rock geochemistry or distance from the gabbroic heat source, except that rocks with sodic amphibole have high Li, suggesting abundance of free water.
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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 | 0.002 | 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".