Isotope Geochemistry of the Northeast Zone, Mount Polley Alkalic Cu-Au-Ag Porphyry Deposit, British Columbia: A Case for Carbonate Assimilation
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
<p id="p-3">Mount Polley is a Late Triassic (~205 Ma) alkalic porphyry Cu-Au-Ag deposit (226.3 thousand tonnes (t) Cu, 21.5 t Au, and 65.1 t Ag), hosted by silica-undersaturated to silica-saturated monzonitic intrusions of the Mount Polley Complex, located in British Columbia, Canada. The Northeast ore zone at Mount Polley is hosted by magmatic-hydrothermal breccia. Copper and precious metals occur in sulfide minerals primarily as coarse- to fine-grained breccia cement. Local wall rocks include equigranular to porphyritic diorite, monzodiorite, and monzonite. </p> <p id="p-4">Alteration, breccia cement, and veins of the Northeast ore zone formed in five paragenetic stages: prebreccia (stage 1), brecciation and main-stage mineralization (stage 2), late-stage mineralization (stage 3), unmineralized postbreccia dikes and veins (stage 4), and epithermal-style veins (stage 5). Intense pervasive K and Fe metasomatism calcite and calc-silicate alteration occurred prior to brecciation caused by the intrusion of megacrystic K-feldspar-phyric monzonite. Stage 2 fluids were silica undersaturated, high temperature (>350C), CO<sub>2</sub> enriched, and of near-neutral to alkaline pH. Potassic, sodic, and calc-potassic assemblages precipitated with mineralization during stage 2 with moderate temperatures at the deposit periphery and in stages 3 and 4. Evidence for more acidic and lower-temperature conditions is preserved in stage 5 veins. </p> <p id="p-5">The <i>&#948;</i><sup>34</sup>S<sub>sulfide</sub> isotope compositions of stages 2 and 3 chalcopyrite, pyrite, and bornite range from &#8722;7.1 to +1.4. Sulfur isotope compositions of anhydrite and gypsum are mostly between 6.2 and 9.8. These values, together with the presence of hematite, are consistent with deposition from an oxidized, sulfate-dominant, high-temperature magmatic-hydrothermal fluid. Limited sulfur isotope geothermometry indicates that Cu sulfides precipitated at temperatures from ~480 to ~250C. </p> <p id="p-6">Hydrothermal calcite occurs in all paragenetic stages at Mount Polley. Calcite <i>&#948;</i><sup>13</sup>C values range from &#8722;0.2 to &#8722;10.5, and <i>&#948;</i><sup>18</sup>O values from 4.0 to 20.9. The enriched C-O isotope values are not consistent with simple precipitation from an entirely magmatic source of hydrothermal fluid. Interaction of the fluid and/or magma with limestone is considered a likely process to explain the C and O isotope signature. </p> <p id="p-7">Lead isotope data suggest mixing of mantle and crustal sources during mineralization. Main-stage chalcopyrite and pyrite as well as late-stage galena have <sup>206/204</sup>Pb values of 18.77 to 18.92, <sup>207/204</sup>Pb of 15.56 to 15.59, and <sup>208/204</sup>Pb of 38.22 to 38.32. Strontium isotope data (0.703310.70371) provide evidence of a strongly depleted mantle source of Sr with minor crustal input. Epsilon Nd values for main-stage apatite range between 5.9 and 6.5, also indicating a depleted mantle source. Stage 5 carbonate <sup>206/204</sup>Pb values of 18.96 to 19.04, <sup>207/204</sup>Pb of 15.57 to 15.59, and <sup>208/204</sup>Pb of 38.26 to 38.36 suggest superposition of an epithermal system onto the Northeast ore zone, potentially as late as ~100 m.y. after breccia formation. </p> <p id="p-8">The data presented are consistent with the hypothesis that the silica-undersaturated alkalic Mount Polley Complex formed due to carbonate assimilation prior to mineralization. This process can explain the <em>&#948;</em><sup>13</sup>C-<em>&#948;</em><sup>18</sup>O isotope data, calcite precipitation concurrent with Cu-Au mineralization, and silica undersaturation of the magma. The CO<sub>2</sub> released during assimilation of carbonate also could have promoted magmatic-hydrothermal brecciation. Silica-undersaturated alkalic porphyry systems may preferentially form in arc terranes built on a carbonate-bearing substrate.</p>
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 | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,004 | 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