Geochemical and textural indicators of syn-eruptive degassing during recent rhyolitic eruptions
Bibliographic record
Abstract
Silicic volcanoes are capable of producing dangerous explosive eruptions and the effusion of lava and domes.Observations from recent rhyolitic eruptions demonstrated how the transition between these two end-member behaviours is markedly complex.Fractures, commonly preserved as tuffisite veins, are transient permeable pathways that allow for the punctuated but efficient escape of volatiles.They are considered key enablers of degassing but their interactions with deeper, gas-rich reservoirs and influence on melt chemistry are not fully understood.Preserved 210 Pb-226 Ra isotope disequilibria, volatile trace element heterogeneity, and complex vein and breccia textures in volcanic bombs have been previously associated with gas fluxing within the conduit.In this thesis I utilise both textural and chemical heterogeneity preserved in samples from the first observed rhyolite eruptions, Chaitén (2008) and Cordón Caulle (2011Caulle ( -2012)), to assess how degassing processes are preserved from the dm to nm scale.210 Pb- 226 Ra isotope and trace element analyses were conducted on 'mini-bulk' samples of tuffisite veins and their respective hosts to understand gas flow through fractures, from deeper reservoirs.The lack of 210 Pb-226 Ra disequilibria preserved in veins constrains the upper limit for the volume of magma that can be degassed by a tuffisite vein during its lifetime.Whilst trace element enrichments and depletions in veins record preferential gas fluxing (e.g.Li, Cu, Pb, Tl, Bi), results are limiting because tuffisites and breccias, which preserve the fracturing process, are comprised of clasts that have each undergone differing degrees of degassing.To further constrain gas fluxing and clasts' individual histories, electron microprobe and laser ablation ICP-MS analyses were undertaken across mm to µm-scale textures in samples from Cordón Caulle.Chemical and textural heterogeneity are strongly linked, depletions of metals VI
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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 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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".