Electron microprobe analyses of diffusion profiles in basaltic melt during anhydrite dissolution
Bibliographic record
Abstract
Electron microprobe analyses of diffusion profiles in basaltic melt during anhydrite dissolution. The experiments and analyses were performed by Raven Polk and form the basis for her M.Sc. thesis at McGill. Abstract from the thesis: "We measured the diffusion of sulfur released from anhydrite during dissolution into a basaltic melt to quantify the rates of sulfur contamination. The diffusion experiments were used to measure anhydrite saturation to provide insight into the interaction between mafic melts and evaporitic units during the emplacement of the Siberian Traps. Diffusion experiments were performed using a dike composition from the Central Atlantic Magmatic Province and a mixture of compressed anhydrite powder. Experimental conditions range from 1250-1450 °C at 1 GPa and durations ranging from 600 to 3600 seconds. Diffusion values vary from 5.1 x 10-12 m2/s to 3.0 x 10-11 m2/s and results were used to create an Arrhenius equation below for the diffusion of sulfur within a tholeiitic basalt:D=6.21 x 10^(-6) exp((-173.6±84.0)/RT). The sulfur peak position from wavelength-dispersive spectroscopy (WDS) indicates that the dominant sulfur species in the melt is sulfate; the fraction of sulfur as sulfate in the melt S6+/Stotal, is ~ 0.60. Anhydrite solubility, the sulfur concentration at anhydrite saturation (SCAS), was determined from the measured sulfur concentrations in the melt and extrapolated along the diffusion profile to the anhydrite/melt interface. The SCAS ranges from 0.69 wt.% at 1450 °C to 1.28 wt.% at 1250 °C. There is no strong dependence of the SCAS on temperature.These diffusivity measurements are applied to a model that attempts to predict the rates of volatile uptake within a basaltic magmatic system; this model provides insight into sulfur storage and transport. The modeling results provide estimations of the amount of sulfur that can be transported in the melt and possibly released into the atmosphere and can help to determine the extent of interaction between the evaporites and magma. Please note that after publication some of the analytical profiles were found to contain crystals.
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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 | 0.000 | 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".