Abstract: Surface features on diamonds and water content of olivine from kimberlite as indicators of fluid systems in kimberlite magma
Notice bibliographique
Résumé
Volatiles in magmas play an important role in the eruption style and the geology of volcanic landforms, determine presence of fluid phase, the depths of volatile exsolution, and the rates of magma accent. In kimberlites the original proportions of the two main volatiles, H2O and CO2, are obscured by complex origin of the groundmass minerals. Volatiles affect diamond preservation and determine the character of surface features produced on diamond faces during dissolution in kimberlites. Experiments demonstrated that oxidation of diamonds in magmas with H2Oor CO2-rich fluids and in the absence of fluid produce distinctively different types of surface features. In addition, water fugacity of kimberlitic magma can be estimated using water content in phenocrystic olivine measured by FTIR spectroscopy. We apply these two independent methods to several kimberlites in order to constrain the behavior of volatiles and their effect on diamond population and the geology of kimberlites. The study uses diamond parcels, olivine concentrates, and kimberlite core from six EKATI Mine kimberlites, Northwest Territories, Canada. These kimberlites have similar emplacement ages, erosion level, and country rocks, but different geology, composition, and diamond populations. The surface features on diamonds studied under optical and scanning electron microscopes were compared to the diamond surfaces produced experimentally in the presence and absence of fluid. Concentration and occurrence of hydroxyl in kimberlitic olivine were measured using FTIR spectroscopy. We found that Leslie and Grizzly kimberlites filled with hypabyssal facies, with low grade and quality of diamonds, show very sharp dissolution forms on diamond surfaces. Such features indicate absence of a free fluid phase during the last stages of kimberlite emplacement. Panda, Beartooth, Misery, and Koala kimberlites filled with volcaniclastic kimberlite, with higher grade and quality of diamonds have diamond surfaces with well-developed trigon pits, rounded edges with striation, and hillocks. Such features suggest emplacement in an H2O-fluidrich environment. However, diamond populations of Panda and Beartooth are dominated by octahedral unresorbed stones and IR spectra of their olivines give higher concentration of water in olivines <600 ppm and the depth of fluid separation greater than 2GPa. On the contrary, Misery and Koala diamonds are mostly rounded with high degree of resorption. Their olivines contain <450 ppm of H2O and fluid separated at more shallow depths. Group 2 OH IR absorption bands are absent in FTIR spectra of olivine from kimberlites filled with hypabyssal facies and present in olivine from all volcaniclasticfilled kimberlites. This can provide a possible link to an early loss of magmatic fluid. The excellent agreement between the two independent datasets suggests that both are linked to the activity of water in the system. We further apply these results to explain the differences between the geology of these kimberlite pipes and their diamond populations.
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.
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 ».