Generation of High-Ni Sulfide and Alloy Phases During Serpentinization of Dunite in the Dumont Sill, Quebec
Notice bibliographique
Résumé
The Dumont sill in the Abitibi region of Quebec is a zoned intrusive body which is differentiated into a lower ultramafic zone, composed of peridotite and dunite, overlain by a mafic zone, with clinopyroxenite, gabbro, and quartz gabbro subzones. Although the dunite contains several layers enriched in primary Ni sulfide minerals, which add considerable value to the deposit, 47% of the resource consists of awaruite- and heazlewoodite-bearing serpentinized dunites which formerly contained Ni only in silicate minerals. Serpentinization occurred isochemically with respect to major components, apart from the addition of H2O and minor loss of CaO. Serpentinization occurred under conditions of very low water-rock ratio, resulting in buffering of fluid to extremely low activities of silica and H2O and allowing the widespread replacement of primary pentlandite by awaruite and heazlewoodite due to accompanying reductions in f O2 and f S2. In layers containing primary accumulations of magmatic sulfide, serpentinization has resulted in the remobilization of nickel from olivine to enrich cumulus sulfides. In layers lacking primary sulfide accumulations, serpentinization was accompanied by the formation of awaruite by reduction of Ni originally hosted by olivine. Early stages of serpentinization were marked by the generation of large volumes of Fe-rich serpentine containing abundant ferric iron as well as lesser amounts of brucite rich in ferrous iron. Later stages of serpentinization caused the replacement of early iron-rich serpentine and brucite by more magnesian serpentine and brucite and the formation of abundant magnetite. Assemblages that are completely serpentinized contain lower nickel in silicates, higher nickel tenor sulfides, and more modal awaruite compared to those that are weakly and partially serpentinized, which are characterized by higher nickel in silicates and lower Ni tenor sulfides. Although awaruite first appears early in the serpentinization process, the highest modal abundances of economically extractable heazlewoodite, awaruite, and Ni-rich pentlandite are observed in rocks that have been completely transformed to the Mg serpentine facies. Regardless of the final opaque mineral host for Ni, the key to removal of Ni from silicate minerals and its sequestration in phases amenable to beneficiation is the early formation of awaruite; otherwise, Ni partitions readily into serpentine and remains inaccessible to mineral extraction. Exploration for similar deposits should be focused on dunite adcumulates formed from unfractionated komatiites, which have undergone complete serpentinization under conditions of diffusion-controlled low water-rock ratio, as evidenced by the absence of wholesale deformation or veining.
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Comment cette classification a été obtenuedéplier
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 | 0,000 | 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 tête enseignante, 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 ».