The Glacier Creek Cu-Zn VMS Deposit, Southeast Alaska: An Addition to the Alexander Triassic Metallogenic Belt
Notice bibliographique
Résumé
<p>The Glacier Creek volcanogenic massive sulfide (VMS) deposit, Alaska, is hosted within Late Triassic, oceanic back-arc or intraarc, rift-related bimodal volcanic rocks of the allochthonous Alexander terrane, known as the Alexander Triassic metallogenic belt. The Alexander Triassic metallogenic belt is host to the world-class Greens Creek Zn-Pb-Ag VMS deposit near Juneau in the south and the giant Windy Craggy Cu-Co VMS deposit in British Columbia, about 250 km to the north. The Glacier Creek deposit, located ~80 km southeast of Windy Craggy, consists of four tabular massive sulfide lenses within a bimodal mafic volcaniclastic and rhyolitic sequence. The mineralization-hosting stratigraphy is folded by a deposit-scale anticline and offset by a thrust fault near the axial surface of the fold. A resource of 8.13 Mt has been inferred from drilling, with grades of 1.41% Cu, 5.25% Zn, 0.15% Pb, 0.32 g/t Au, and 31.7 g/t Ag. Six main mineralization types are recognized, dominated by massive barite-sphalerite-pyrite, which is replaced at the base and center of the main lenses by massive and semimassive chalcopyrite-pyrite-quartz. The flanks and tops of the lenses are carbonate rich and consist of interbedded calcite-dolomite, barite and sulfide, resedimented massive barite-sulfide, and mineralized massive carbonate rocks. Tuffaceous hydrothermal sediment, with a distinct positive Eu anomaly, overlies the massive sulfide. Pyrrhotite and chalcopyrite in stringers constitute the main "feeder zone." Stringer-style sphalerite-pyrite mineralization occurs above and below the lenses. Fe-poor sphalerite is dominant throughout the lenses, whereas Fe-rich sphalerite occurs at the stratigraphic top and bottom of the lenses in pyrrhotite-rich zones. Galena, tennantite-tetrahedrite, and arsenopyrite are the most important trace minerals within massive barite-sphalerite-pyrite mineralization, which is generally enriched in Sb, Hg, and Tl. Mineralization-related gangue minerals include barite, quartz, barian muscovite, calcite, dolomite, albite, chlorite, hyalophane, and celsian. Four types of alteration are recognized in the dominantly basaltic host rocks: pervasive muscovite-rich alteration, quartz-pyrite alteration associated with sulfide stringers, stratabound carbonate-bearing alteration, and background epidote-bearing alteration. Mass balance calculations indicate gains of S, Fe, Si, and K with coincident losses of Ca, Na, and Mg in all of the alteration types. Trace elements, Tl, Sb, Hg, Ba, Zn, Cu, and As were added to the rocks, whereas Sr was lost. Short wavelength infrared (SWIR) spectroscopy shows an increase in the wavelength of the AlOH absorption feature toward mineralization at a scale of 30 to 50 m, coincident with a general decrease in the Na, K, and Al and increase in the Fe, Mg, and Ba content of muscovite. </p> <p>The Glacier Creek deposit is transitional in character between Greens Creek, which is more Zn, Pb, and precious metal rich, and the Windy Craggy deposit, which is more Cu and Co rich, reflecting differences in the basement rocks and depositional settings within the Alexander Triassic metallogenic belt. Mineral-chemical studies and sulfur isotope data suggest that the Glacier Creek deposit formed under initially oxidized and sulfate-rich conditions that evolved to more reduced conditions in the latest stages of mineralization. The abundant argillite and presence of hyalophane rather than barite in the immediate hanging wall of the deposit may be an indication of a deepening basin and development of local anoxia, similar to Greens Creek.</p>
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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 | 0,001 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,034 | 0,006 |
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; les deux têtes enseignantes s’accordent sur ce qui est montré ici.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».