Temperature-induced structural transformations in fluorophlogopite studied by in situ high-temperature Raman spectroscopy
Pourquoi ce travail est dans la base
Une base qui oublie comment elle a trouvé un travail ne peut pas être vérifiée. Voici les voies qui ont admis celui-ci.
Notice bibliographique
Résumé
Phlogopite (nominally AKMMg3T(AlSi3)O10X(OH)2) is the magnesian trioctahedral endmember of the biotite solid-solution series. This phyllosilicate can accommodate substantial amounts of fluorine, usually up to 5 weight percent (wt%) and up to 8.7 wt% in extreme cases (Gianfagna et al., 2007), which substitutes for hydroxyl (OH) groups at the anionic site. Given that phlogopite is a commonly found hydrous silicate, acting as an important F reservoir in ultramafic and ultrapotassic upper mantle lithologies and an accessory mineral in various igneous and metamorphic rocks, it can contribute to the Earth’s volatile cycles. Therefore, the deeper understanding of the temperature-induced phlogopite breakdown into pyrope and forsterite (Trønnes, 2002) and the role of F in the crystal structure of fluorophlogopite during its structural collapse can provide valuable information in several Earth’s dynamic systems. For instance, in metasomatic processes in the peridotitic mantle wedge of subduction zones, mineral stability at upper mantle conditions, and complex volcanic systems. Additionally, the high-temperature atomic dynamics of complex hydrous silicates containing Fe2+, characterized by considerable structural anisotropy, as studied by Raman spectroscopy, can offer valuable information about the thermal activation of charge carriers (delocalized H+ and e-), thus about lithosphere conductivity anomalies (Bernardini et al., 2023). This study focuses on the temperature-induced changes in the local structure and atomic vibrations of Fe2+-containing fluorophlogopite. For this purpose, a fluorophlogopite sample from Cardiff, Ontario in Canada was subjected to in situ Raman spectroscopy in the temperature range of 300-1450 K. The exact chemical formula of this mineral specimen was determined by wavelength-dispersive electron microprobe analysis (EMPA) and it is A(K0.93Na0.06Ba0.01)M(Mg2.81Fe2+0.15Ti0.01Mn0.01)T(Si2.99Al0.99Ti0.02)O10X(F1.60OH0.40). We show that fluorophlogopite undergoes stepwise structural and chemical changes, which can be monitored by the evolution of the Raman-active phonon modes at ~93 cm-1 (interlayer vibrations), 195, 279, and 325 cm-1 (dominated by octahedral vibrations) as well as at 684 and 739 cm-1 (TO4-ring mode vibrations). Near 500-600 K an interlayer structural instability occurs, which most probably results in a rearrangement of the layer stacking sequence. This activates the mobility of K+ cations in the interlayer space in the temperature range between 600 and 1000 K. Two independent heating-cooling runs to 1100 and 1450 K indicate a partial loss of K+ above 1000 K, which was confirmed by subsequent WD-EMPA. Oxidation of MFe2+ takes place between 900 and 1300 K. A partial thermal decomposition of fluorophlogopite occurs above 1300 K, leading to the formation of a minor amount of nanosized forsterite within the phlogopite matrix, but the overall biotite structure type persists up to 1450 K.  ReferencesBernardini, G. Della Ventura, J. Schlüter, B. Mihailova, Geochem. 2023, 83, 125942. Gianfagna, F. Scoradri, S. Mazziotti-Tagliani, G. Ventruti, L. Ottolini, Am Mineral. 2007, 92, 1601. R.G. Trønnes, Mineral Petrol. 2002, 74, 129.
Récupéré en direct depuis OpenAlex et désinversé. Les résumés ne sont pas conservés dans cette base de données : les index inversés représentent 8,6 Go des 9,3 Go de texte de la base, et le serveur dispose de 13 Go libres.
Prédiction distillée sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Apprise à partir de 10 348 étiquettes directes de Codex et de 10 348 étiquettes directes de Gemma. Le mode candidate est l'union des têtes enseignantes seuillées; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont ni des étiquettes humaines ni des étiquettes directes de modèles de pointe.
Scores Codex et Gemma par catégorie
| 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 | 0,000 | 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 | 0,001 | 0,001 |
| 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 découle