Using delayed nucleation in melt inclusions to constrain final growth durations of magmatic crystals: An introduction and example using the May 18, 1980, White Pumice of Mt. St. Helens
Bibliographic record
Abstract
Abstract Knowledge of the timing and duration of magmatic events provides important constraints on the evolution of igneous rocks and on volcanic eruption mechanisms. A new method is proposed to constrain the time duration between the saturation of a suite of melt inclusions trapped in a crystal with daughter minerals and the quenching of the melt inclusions to conditions where crystals cannot form. Classical nucleation theory predicts that crystal nucleation delay and subsequent growth are functions of the initial melt volume. This suggests that the crystallinity (defined in this work as the presence or absence of crystals) in a suite of melt inclusions of differing volumes can be used to constrain the time interval between the saturation of the melt inclusions and their quenching. As an example to demonstrate the applicability of this technique, a set of 402 melt inclusions found in 5 plagioclase crystals erupted in the Mt. St. Helens White Pumice of May 18, 1980, was studied using a petrographic microscope and a scanning electron microscope. An ellipse was fit to each melt inclusion, its axes measured, and the presence or absence of crystals within the inclusions noted. The volume of each melt inclusion was estimated by approximating the size of the inclusion as an ellipsoid of revolution using the measured ellipse axes with rotation about the major axis. These measurements were used to calculate the probability of melt inclusion crystallization as a function of melt inclusion size and fit to the classical nucleation theory model for delayed nucleation in small volumes. This fit yielded the product of the time-averaged nucleation rate, ⟨J⟩, and the time duration, Δt, or ⟨J⟩Δt. This information is combined with previous experimental studies on plagioclase nucleation rates, ⟨J⟩, and crystal habits to calculate that melt inclusions most probably became supersaturated (which may have occurred soon after trapping) only days to months before the May 18 eruption. This time estimate is consistent with the observed seismic and gas emission records prior to the eruption and with diffusion modeling of Fe-Mg zoning in orthopyroxene crystals from Mt. St. Helens eruptions in the 1980s.
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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 | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 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".