Geology of the Cheechoo gold property, Eeyou Istchee Baie-James, Superior Province, northern Quebec
Notice bibliographique
Résumé
The Cheechoo property (Sirios Resources) is located at 15 km southeast of the Éléonore world-class gold mine (reserves and resources of 7.1 Moz Au). The property is mainly underlain by paragneissic wacke and migmatites belonging to the Opinaca Subprovince, local banded iron formations and mafic dykes of the La Grande Subprovince, and the Cheechoo intrusion. The Cheechoo intrusion is dated at 2612 Ma, which is penecontemporaneous with the 2618 Ma Vieux Comptoir suite and the 2620-2600 Ma leucogranitic dykes and veins that are injected within the supracrustal rocks of the La Grande Subprovince during amphibolite facies metamorphism. Locally, the Cheechoo intrusion shows a progressive transition and consanguineous relationships with quartz-feldspar pegmatite dykes. The later dykes are concentrated at the margins of the Cheechoo intrusion and spatially associated with part of the gold mineralization. These dykes have a high variation of mineral assemblages and miarolitic cavities suggesting crystallization near or at the magmatic-hydrothermal transition. The Cheechoo intrusion has variable textures from massive, porphyritic with feldspar phenocrysts to gneissic and sacharoidal with biotite porphyroblasts, suggesting a complex magmatic and metamorphic history. Lithogeochemical data indicates that the intrusion has granodioritic, trondhjemitic, metaluminous to peraluminous compositions, reduced nature (Fe2O3/FeO < 0.2) and REE patterns, similar to some leucogranites of the Opinaca Subprovince. The high Na2O content (> 6 wt %) of the Cheechoo intrusion can be attributed to an early-Au sodic metasomatic event. Detailed mapping of stripped outcrops indicate that gold-bearing zones are mainly hosted by the Cheechoo intrusion and to a lesser extent within surrounding metasedimentary rocks, pegmatite dykes and mafic schists. Gold mineralization is characterized by a network of sheeted quartz±(feldspar) veins with variable amounts of phlogopite, actinolite, diopside and scheelite that are related to calc-silicate and potassic alteration halos, mainly developed in vein selvages. High-grade gold veins and their selvages generally contain less than 5 % of disseminated sulphides (arsenopyrite, pyrrhotite ± pyrite) and have a coarse pegmatitic texture with local visible gold (similar to the Moni prospect). Crosscutting relationships between gold-bearing sets of veins indicates an early V1 veins network composed of quartz ± (feldspar, actinolite, scheelite, pyrite, pyrrhotite, arsenopyrite), followed by sheeted, extensional to en-echelon V2 veins network (60-70% of the veins) characterized by quartz ± (feldspar, phlogopite, pyrrhotite and arsenopyrite). The V2 veins are cut by V3 extensional veins, composed of quartz ± actinolite. Gold mineralization has a Bi-W-As ± (Te, Se, Pb) metallic signature in association with Mg-K enrichments associated with narrow alteration zones in vein selvages. In-situ delta-34S analyses of gold-associated sulphides are similar to those of typical Archean orogenic gold deposits and to values of sulphides from the Éléonore gold mine, thus suggesting fluid(s) of similar compositions. The age of the host Cheechoo intrusion, 2612 Ma, represents the maximum age of gold mineralization. The structural characteristics of the auriferous system are best explained by a model of syn-tectonic (late-D2) emplacement of the Cheechoo intrusion and related leucogranitic dykes and gold-bearing veins networks. The mineralogy of the auriferous veins, the hydrothermal alteration assemblages and the spatial association with the reduced intrusion, pegmatite dykes and mafic schists bare similarities with those of reduced intrusion-related gold systems. The Cheechoo property represents a new style of gold mineralization in the Eeyou Istchee Baie-James municipality.
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Scores du classifieur distillé par catégorie (deux têtes)
| 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 | 0,001 | 0,002 |
| Études des sciences et des technologies | 0,002 | 0,001 |
| Communication savante | 0,001 | 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 découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule source (Gemma direct ou Codex distillé), 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 ».