Vesiculation in rhyolite at low <scp>H</scp><sub>2</sub><scp>O</scp> contents: A thermodynamic model
Bibliographic record
Abstract
Abstract We present experimental data on the thermodynamics and kinetics of bubble nucleation and growth in weakly H 2 O‐oversaturated rhyolitic melts. The high‐temperature (900–1100°C) experiments involve heating of rhyolitic obsidian from Hrafntinnuhryggur, Krafla, Iceland to above their glass transition temperature ( Tg ∼ 690°C) at 0.1 MPa for times of 0.25–24 h. During experiments, the rhyolite cores increase in volume as H 2 O vapor‐filled bubbles nucleate and expand. The extent of vesiculation, as tracked by porosity, is mapped in temperature‐time ( T ‐ t ) space. At constant temperature and for a characteristic dwell time, the rhyolite cores achieve a maximum volume where the T ‐ t conditions reach thermochemical equilibrium. For each T‐t snapshot of vesiculation, we use 3‐D analysis of X‐ray computed tomographic (XCT) images of the quenched cores to obtain the bubble number density (BND) and bubble‐size distribution (BSD). BNDs for the experimental cores are insensitive to T and t , indicating a single nucleation event. All BSDs converge to a common distribution, independent of T , melt viscosity (η), or initial degree of saturation, suggesting a common growth process. We use these data to calibrate an empirical model for predicting the rates and amounts of vesiculation in rhyolitic melts as a function of η and thermochemical affinity ( A ): two computable parameters that are dependent on T , pressure and H 2 O content. The model reproduces the experimental data set and data from the literature to within experimental error, and has application to natural volcanic systems where bubble formation and growth are not diffusion limited (e.g., lavas, domes, ignimbrites, conduit infill).
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.001 |
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 teacher head, 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".