Orogenic Greenstone-Hosted Quartz-Carbonate Gold Deposits of the Timmins-Porcupine Camp
Notice bibliographique
Résumé
Abstract The Timmins-Porcupine gold camp, with a total production of more than 2,125 tonnes (75 Moz) Au to date, represents the largest Archean orogenic greenstone-hosted gold camp worldwide in terms of total gold production. The gold deposits of the camp are distributed over 50 km of strike length along the Destor-Porcupine fault zone, including the giant Hollinger-McIntyre and Dome deposits. These two deposits are archetype examples of large Archean orogenic gold systems. The Dome mine, where the ore is centered on a folded unconformity between Tisdale volcanic rocks and Timiskaming sedimentary deposits, also illustrates the spatial relationship between large gold deposits and a regional unconformity. Gold-associated hydrothermal activity in the camp spanned a long period of time, as illustrated by early stage, barren to low-grade ankerite veins formed between ca. 2690 and 2674 Ma, i.e., prior to or very early in the development of the regional unconformity and sedimentation of the Timiskaming assemblage. Such early carbonatization may represent a key hydrothermal event in the formation of large orogenic gold deposits and illustrates the protracted nature of the large-scale CO2-rich metasomatism occurring before and during gold deposition. The bulk of the gold is, however, younger than the Three Nations Formation in the upper part of the Timiskaming assemblage (i.e., ≤2669 ± 1 Ma) and consists mainly of syn-main regional shortening deformation (D3) networks of steeply to moderately dipping fault-fill quartz-carbonate ± tourmaline ± pyrite veins and associated extensional, shallow to moderately dipping arrays of sheeted and sigmoidal veins hosted in highly carbonatized and sericitized rocks. Formation of the gold deposits of the Timmins-Porcupine camp can be related to several key factors. The Destor-Porcupine fault zone represents a first-order control on the location of the camp as this major fault zone allowed large scale CO2-rich hydrothermal fluid upflow. The fault zone also controlled the location of the Timiskaming clastic basin, which is thought to have been developed as a result of early-stage synorogenic extensional faulting. Several of the orogenic gold deposits of the camp are spatially associated with the regional unconformity separating folded submarine volcanic rocks of the Tisdale assemblage form the syn-orogenic sedimentary deposits of the Timiskaming assemblage. The current level of erosion is deep enough to expose the unconformity and to maximize the chance of discovery of the orogenic deposits or their footprint, but allowed for preservation of at least part of the gold deposits that are mainly hosted in the highly reactive Fe-rich Tisdale basalt. Additional key factors include the presence of komatiitic and/or basaltic komatiite flows, of competent intrusions that predate the main phase of shortening of the belt and the occurrence of bends in the trace of the Destor-Porcupine fault zone that may have facilitated focus to ore-forming fluid upflow. Furthermore, the camp is characterized by complex structural and rheological discontinuities, competency contrasts, and early stage folds with associated fracture and fault networks that provided highly favorable ground preparation conditions. The exceptional gold enrichment of the camp requires that the hydrothermal fluids originated from favorable source rocks, lending support to the concept of provinciality, which may best explain the exceptional gold fertility of the southern Abitibi greenstone belt.
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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 | 0,003 | 0,001 |
| 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 ».