Structurally Controlled Vein Barite Mineralization in the Maritimes Basin of Eastern Canada: Geologic Setting, Stable Isotopes, and Fluid Inclusions
Notice bibliographique
Résumé
The Brookfield barite deposit occurs in the Carboniferous Maritimes basin of eastern Canada, an area known for ca. 300 Ma Mississippi Valley-type (MVT) Zn-Pb-Ba mineralization, including the past-producing Walton barite and Gays River Zn-Pb deposits. In contrast to most of MVT mineralization in the Maritimes Basin that is hosted by Visean carbonate rocks of the Windsor Group, the Brookfield deposit is hosted by red terrestrial clastics of the underlying Tournaisian Horton Group. The barite mineralization occurs as ≤25-m-wide fault fill with both coarse-textured, pristine barite and mylonitic-textured barite situated close to the Cobequid-Chedabucto fault system, separating the Meguma and Avalon terranes. The breccia vein mineralization has a simple mineralogy and consists of barite with up to 1.3 wt percent Sr, minor siderite, and trace amounts of late-stage quartz and calcite. The host rocks close to the barite mineralization are intensely altered, with quartz and kaolinite replacing muscovite and complete removal of diagenetic hematite. A Grant-type iso-con plot indicates mass loss (C A = 0.82*C O ) during wall-rock alteration with REE profiles maintained but relative chondrite-normalized abundances reduced. Although an Fe-Mn zone occurs a few 100 m along strike, no such mineralization occurs in the barite deposit. Fluid inclusion studies indicate that vein fluids were saline brines (20–30 wt % NaCl + CaCl 2 equiv) that co-existed with an immiscible N 2 -CO 2 -CH 4 gas. Laser Raman analysis of the most common gas-rich inclusions indicates a uniform fluid chemistry with 66 mol percent N 2 and 34 mol percent CO 2 and is consistent with compositions inferred from thermometric measurements. Homogenization temperatures for primary, aqueous fluid inclusion asemblages in quartz intergrown with barite indicate minimum trapping temperatures of 210°C. Conditions at the time of entrapment, based on intersection of aqueous and gaseous isochores, are estimated at ~775 bars and 250°C. Stable isotope data for vein minerals (barite, siderite, quartz) are uniform in nature and indicate δ 18 O fluid = +12 per mil at 250°C for siderite and +9.8 per mil for quartz, δ 13 C fluid = −4 to −6 per mil from siderite, and δ 34 S fluid = +12 per mil from barite. Fluid inclusion extracts indicate δD values of −47 to −71 per mil. Collectively, these isotopic compositions are consistent with a basinal-type fluid derived from modified meteoric water with sulfur derived from Carboniferous evaporites and carbon of mainly marine limestone origin (i.e., Carboniferous Windsor Group) with a minor biogenic component from the Horton Group. Mineralization at Brookfield resulted from focusing of heated, overpressured brines of modified basinal origin into an active fault zone environment. The association of the barite mineralization with intensely altered wall rock represents a rare example of such alteration in the MVT metallogenic domain of the Maritimes Basin. However, similar alteration associated with Ba-Fe-Mn mineralization along the Cobequid-Chedabucto fault system raises the possibility that the Brookfield deposit may instead be part of another mineralizing event that was distinct from the 300 Ma MVT deposits.
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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) | 0,005 | 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 ».