The origin of Mn and Y annuli in garnet and the thermal dependence of P in garnet and Y in apatite in calc-pelite and pelite, Gagnon terrane, western Labrador
Bibliographic record
Abstract
X-ray compositional maps and zoning profiles for major and trace elements have been measured in garnet, apatite and epidote-group minerals from calc-pelitic and pelitic schists from western Labrador, by electron microprobe and by laser ablation ICP-MS. High Y abundance in apatite adjacent to resorbed garnet and a decreasing modal abundance of apatite with garnet growth indicate that apatite participates in major rock-forming mineral reactions. Phosphorus concentration in garnet porphyroblasts coexisting with apatite decreases smoothly from core to rim and depends moderately on metamorphic grade. Apatite coexisting with xenotime shows high-Y cores and the concentration of Y in apatite increases with metamorphic grade. Many of the analyzed garnet porphyroblasts exhibit Y annuli which provide information about different physicochemical processes operating during garnet growth. We describe criteria to fingerprint three of these processes in the analyzed garnets. (1) Yttrium annuli produced by garnet resorption and regrowth are characterized by an asymmetric shape with a steeper slope on the inner side of the annulus and by a decoupled variation between garnet-compatible and garnet-incompatible elements at the resorption margin. (2) Y annuli produced by breakdown of Y- and REE-rich trace phases such as xenotime, monazite, apatite and epidote-group minerals are indicated by REE peaks in LREE (monazite, allanite), MREE (epidote), or HREE (xenotime, zircon). (3) Y annuli associated with diffusion-controlled growth occur in garnet with oscillatory textural zoning defined by alternating inclusion-rich and inclusion-poor zones, with increases in concentrations of garnet-compatible elements such as Y and HREE correlating with inclusion-free zones. Mn annuli in some garnets were produced by sporadic local breakdown of Mn-rich epidote and in several cases indicate that thin-section scale equilibrium during annulus formation was not achieved, raising questions concerning the use of Mn concentration as a time marker in garnet growth modeling.
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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 | 0.000 |
| 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) | 0.000 | 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".