Evidence of pre-eruptive volatile-saturated magmas before the eruption of Agnano-Monte Spina (Phlegrean Fields, Southern Italy)
Notice bibliographique
Résumé
Assessing the pre-eruptive dynamic and volatile-saturation conditions of magmas of past eruptions at active volcanic systems is of paramount importance to understand the future behavior of volcanoes capable of high explosive events. Among all active volcanoes on the Earth, Campi Flegrei caldera (CFc) in southern Italy is a well monitored volcano considering the past highly explosive eruptions such as that of the Neapolitan Yellow Tuff (40 km3) occurred 15 ka ago. At the present, CFc has been undergoing through an unrest crisis consisting of a ~120 cm uplift of the central part of the caldera since 2005 (INGV, November 2023 bulletin), rising a debate relative to the origin of this crisis among scientists. The high volcanic risk is derived by the high degree of urbanization at CFc and the proximity to the city of Naples. For assessing the volcanic risk of CFc, scientists have selected the Agnano-Monte Spina (A-MS) eruption as a reference. The A-MS, in fact, represents the highest explosive event for the last 4.5 ka of CFc activity.We studied 100 clinopyroxenes from pumices of air fall deposit associated to the A-MS, and we studied the petrography of their hosted melt and fluid inclusions (MI and FI respectively). The major and minor element compositions of the selected clinopyroxene were characterized based on electron-microprobe analysis. In addition, the volatile contents of the bubble of MI and FI were studied by using Raman microspectroscopy.Two groups of clinopyroxene were identified based on mineral chemistry and petrography. On one hand, clinopyroxenes of one group show (1) a light green colour as hand specimen, (2) diopsidic composition (MgO=16-18 wt.%), and (3) resorbed margins. This group of clinopyroxenes was named as MgO-rich cpx. On the other hand, clinopyroxenes of the other group show (1) a showing a dark green colour as hand specimen, (2) salitic composition (MgO=12-14 wt.%), and (3) larger size grain relative to MgO-rich cpx. This group of clinopyroxenes was named as MgO-poor cpx. The most striking difference of these two groups of cpx are the types of MI and FI hosted in the crystals. Glassy MI are found exclusively hosted in the MgO-poor cpx. These glassy MI hosted in MgO-poor cpx show shrinkage bubbles (bubble-bearing MI). In contrast, MgO-rich cpx host MI and FI which were trapped heterogeneously together. Shrinkage bubbles of MI hosted in MgO-poor cpx did not show any Raman signals of volatile species, while FI and shrinkage bubbles of MI hosted in Mg-rich clinopyroxene showed CO2, carbonate, and H2S Raman signals.Based on our results and data of MI and cpx from the literature, we suggest that a magma mush of relatively less evolved composition associated to MgO-rich cpx was present at shallow depth (~3 km). A deeper and more evolved magma ascended from deeper the plumbing system and mixed with a volatile-saturated mush triggering the A-MS eruption. We further suggested that the shallow magma mush was saturated with a CO2-H2S-rich magmatic fluids, while the deeper and more evolved magma did not present evidence of volatile saturation.
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Comment cette classification a été obtenuedéplier
Prédiction machine sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Le volet Gemma est une étiquette directe du modèle pour chaque travail de la base, lue sur la notice réduite au titre. Le volet Codex est un classifieur appris des 10 348 étiquettes directes de Codex et calibré sur les taux pondérés de l'échantillon; les champs sans appui suffisant ne portent aucun appel Codex. Le mode candidate est l'union des deux volets; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont pas des étiquettes humaines.
Scores du classifieur distillé par catégorie (deux têtes)
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,001 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,001 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule source (Gemma direct ou Codex distillé), pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».