In Situ Monazite Dating of Sediment-Hosted Stratiform Copper Mineralization in the Redstone Copper Belt, Northwest Territories, Canada: Cupriferous Fluid Flow Late in the Evolution of a Neoproterozoic Sedimentary Basin
Notice bibliographique
Résumé
Abstract The 300-km-long Redstone copper belt in the Mackenzie Mountains, Northwest Territories, Canada, is composed of a series of sediment-hosted stratiform copper (SSC) deposits hosted in Neoproterozoic fault-bounded intracontinental rift basins. Mineralization at Coates Lake, the largest of these deposits, is concentrated within microbial laminite layers in the transition zone between underlying continental red beds of the Redstone River Formation and overlying marine carbonates of the Coppercap Formation. Disseminated cupriferous sulfides (chalcopyrite, bornite, and chalcocite) form part of a late diagenetic mineral association with dolomite, K-feldspar, albite, quartz, monazite, apatite, and pyrite that partially replaced detrital and early diagenetic minerals, including calcite cements, sulfate, and earlier generations of pyrite. Bornite (± minor chalcopyrite), calcite, dolomite, quartz, K-feldspar, and albite were also deposited in rare bedding-parallel veins adjacent to the lowermost mineralized microbial laminite layer in the transition zone. The absolute timing of mineralization was constrained by in situ U-Th-Pb chemical dating of monazite from four samples hosting disseminated SSC-type mineralization. The monazite have rounded, Th-U-heavy rare earth element-rich, detrital cores surrounded by Th-U-poor, light rare earth element-S-Sr-rich rims. The rim stage of monazite growth is intergrown with and enveloped by cupriferous sulfide and is paragenetically constrained as being part of the disseminated SSC-type mineralizing event. Eleven detrital cores yielded dates between 1843 and 1025 Ma, older than the depositional age of transition zone strata previously constrained to be between 775 and 732 Ma. Ten monazite rims yielded dates between 661 and 607 Ma. A weighted average date of 635 ± 13 Ma provides a maximum estimate, and is our preferred interpretation, for the absolute age of all copper mineralization at the Coates Lake deposit. Mineralization formed approximately 100 m.y. after deposition of the host rocks, during the thermal sag phase of continental rifting. Stratigraphic reconstructions, coupled with estimates of sediment compaction, indicate that at 635 Ma the transition zone was buried by ~4 km of sediments and overlaid another ~1.7 km of sediments that formed the Redstone River and Thundercloud Formations. Mudstone and carbonate-rich units above the transition zone acted as low permeability caps that led to suprahydrostatic fluid pressures in the underlying sediments. The bedding-parallel veins indicate transient supralithostatic fluid pressures. Free convection of pore fluids began within the transition zone and underlying units once they became hydrologically isolated from overlying strata. Mineralization formed as oxidized saline pore fluids circulated through the red beds (± underlying basaltic flows and basal sedimentary detritus), stripping copper and carrying it up into the transition zone. The salinity of the pore fluids may have, at least in part, originated from cryogenic brines generated by the Sturtian (717–662 Ma) global glaciation event.
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 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 | 0,001 | 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) | 0,000 | 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 ».