Evaluating the Origin of Garnet, Cordierite, and Biotite in Granitic Rocks: a Case Study from the South Mountain Batholith, Nova Scotia
Bibliographic record
Abstract
Evaluating the origin of garnet, cordierite, and biotite in granites provides important insight into closed- and open-system magma evolution. We present field, textural, major- and trace-element mineral chemical, and Sr–Nd whole-rock isotopic data on garnet-, cordierite-, and biotite-rich zones from the peraluminous South Mountain Batholith. We infer that: (1) garnet-rich zones of decimeter to meter size with ≤30 vol. % large, subhedral garnet with abundant inclusions of detrital country-rock monazite represent partially assimilated metapelitic country rocks, where garnet is the incongruent product of biotite-dehydration melting; (2) cordierite-rich zones tens of meters to kilometers in dimension, with ≤5 vol. % large, subhedral to euhedral, zoned cordierite, formed by crystallization from relatively evolved magmas and subsequent crystal accumulation; (3) biotite-rich zones with large, subhedral to euhedral biotite with abundant euhedral apatite inclusions, making up ≤80 vol. % (centimeter-scale) or ≤25 vol. % (kilometer-scale) of the rocks, formed dominantly by fractional crystallization throughout the chemical evolution of the batholith. Our results suggest that for garnet and cordierite, a combination of textural and mineral chemical characterization is probably sufficient to determine their origin in granites. However, for biotite and other readily equilibrated minerals, evaluating both mineral and rock textures and major-element, trace-element, and isotopic compositions is essential.
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.002 | 0.002 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| 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".