SULFUR K-EDGE XANES SPECTROSCOPY: CHEMICAL STATE AND CONTENT OF SULFUR IN SILICATE GLASSES
Bibliographic record
Abstract
The chemical state and local environment of sulfur in basaltic glasses from the eastern Galapagos rift and quenched laboratory experiments have been investigated by synchrotron-radiation S K-edge X-ray absorption near-edge structure (XANES) spectroscopy, using an energy-selective fl uorescence detector. We have also investigated sulfur in melts in the system 6NaAlSiO4–CaS– CaSO4 quenched from 1500°C and various reference compounds, using conventional fl uorescence yield and total-electron yield (TEY) recording modes. The S K-edge XANES spectrum of CaS dissolved in Na-aluminosilicate glass is dominated by a broad singlet edge-feature near 2475 eV, consistent with isolated SCan coordination polyhedra in the melt, whereas that of quenched end-member CaSO4-bearing melt is similar to XANES spectra of crystalline sulfates. The linear correlation between relative XANES area and wt% content of sulfur has been used to estimate the content of sulfur in samples of lazurite (5.6–6.3 wt% by EPMA), scapolite-group minerals (0.4 wt%) and the basaltic glasses (0.04–0.15 wt%). The S K-edge XANES spectra of basaltic glasses synthesized under reducing (WM and IQF solid oxygen-buffer) conditions are dominated by a single broad absorption peak at 2470–2482 eV in combination with a weak peak or shoulder at 2470–2471 eV, and are reproduced by mixing XANES spectra of FeS and alkaline-earth monosulfi des. The S K-edge XANES spectra for glasses from the eastern Galapagos rift are also dominated by S 2– , but one TEY spectrum shows possible thiosulfate and another, trace sulfate.
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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) | 0.001 | 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".