Boundary‐Layer Melts Entrapped as Melt Inclusions? The Case of Phosphorus‐ and CO <sub>2</sub> ‐Rich Spinel‐Hosted Melt Inclusions from El Hierro, Canary Islands
Bibliographic record
Abstract
Melt inclusions provide unique information on the volatile budgets and compositional diversity of magmatic systems, but are susceptible to synentrapment and postentrapment compositional modifications. The possible formation of chemically anomalous boundary layers around growing crystals and their subsequent entrapment as melt inclusions have been demonstrated experimentally and theoretically, but are thought to be of negligible importance in natural melt-inclusion suites. Here we report on the major, trace, and volatile element compositions of spinel-hosted melt inclusions from El Hierro, Canary Islands, that show anomalous departures in FeOt–SiO2 space and high concentrations of P2O5, a slow diffuser in silicate melts, with respect to olivine-hosted melt inclusions, the matrix glass, and bulk rock from the same samples. These inclusions also display extremely high CO2 concentrations and high S/H2O and Cl/F ratios. With the rapid growth textures of spinels, these observations suggest that spinel-hosted melt inclusions represent boundary-layer melts, the compositions of which were controlled by synentrapment crystal growth and incomplete diffusive relaxation. Our results document a rare case of entrapment of boundary-layer melt in natural magmas, indicate that fast-grown spinel may be a poor melt-inclusion host target, and highlight a means to flag potential boundary-layer melts in melt-inclusion data sets.
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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 | 0.001 | 0.000 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.001 | 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".