| Titre | The role of enigmatic deep crustal and upper mantle structures on Au and magmatic Ni-Cu-PGE-Cr mineralization in the Superior Province |
| Télécharger | Téléchargement (publication entière) |
| |
| Licence | Veuillez noter que la Licence du gouvernement
ouvert - Canada remplace toutes les licences antérieures. |
| Auteur | Harris, L B; Adiban, P; Gloaguen, E |
| Source | Targeted Geoscience Initiative 5: grant program final reports (2018-2020); par Targeted Geoscience Initiative Coordination Office; Commission géologique du Canada, Dossier public 8755, 2021 p. 85-128, https://doi.org/10.4095/328984  Accès ouvert |
| Année | 2021 |
| Éditeur | Ressources naturelles Canada |
| Document | dossier public |
| Lang. | anglais |
| DOI | https://doi.org/10.4095/328984 |
| Media | en ligne; numérique |
| Référence reliée | Cette publication est contenue dans Targeted
Geoscience Initiative 5: grant program final reports (2018-2020) |
| Formats | pdf |
| Province | Ontario; Québec; Terre-Neuve-et-Labrador |
| SNRC | 22; 23; 24; 25; 31; 32; 33; 34; 35; 41; 42; 43; 44; 52; 53; 54; 62; 63; 64 |
| Région | Labrador |
| Lat/Long OENS | -100.0000 -64.0000 62.0000 45.0000 |
| Sujets | prospection minière; potentiel minier; gisements minéraux; or; nickel; cuivre; chrome; gîtes magmatiques; gisements porphyriques; molybdène; uranium; thorium; genèse des minerais; minéralisation;
contrôles des minerais; géologie du socle; caractéristiques structurales; failles; failles transversales; failles, extension; zones de cisaillement; fractures; structures circulaires; linéaments; lithologie; roches métamorphiques; granulites; roches
mafiques; roches ultramafiques; roches intrusives; kimberlites; structure de la croûte; lithosphère; craton; manteau terrestre; levés géophysiques; levés aéromagnétiques; levés aéromagnétiques; levés gravimétriques, sol; interprétations
magnétotelluriques; interpretations de résistivité; interprétations de la pesanteur; méthodes radar; interpretations structurelles; tendances structurelles; interprétations tectoniques; analyses statistiques; antécédents tectoniques; intrusions;
formation de failles; marges plaques; raccourcissement de la croûte; soulèvement de la croûte; décollement; magmatisme; fluage; métamorphisme; déformation; formation de fissures; décrochement horizontal; modèles; métallogénie; Archéen; Province de
Superior ; Zone de Kapuskasing Structural ; éléments du groupe de platine; Traitement des données; l'apprentissage machine; Intelligence artificielle; Géomorphologie; géologie économique; géologie structurale; géophysique; géologie extraterrestre;
Sciences et technologie; Nature et environnement; Précambrien; Protérozoïque |
| Illustrations | cartes géolscientiques généralisées; cartes de localisation; diagrammes; organigrammes; diagrammes 3D; profils; images 3D; tableaux; modèles; images satellitaires; modèles 3D |
| Programme | Initiative géoscientifique ciblée (IGC-5) Gestion de la connaissance de IGC |
| Diffusé | 2021 10 27 |
| Résumé | (disponible en anglais seulement)
Aeromagnetic and ground gravity data for the Canadian Superior Province, filtered to extract long wavelength components and converted to pseudo-gravity,
highlight deep, N-S trending regional-scale, rectilinear faults and margins to discrete, competent mafic or felsic granulite blocks (i.e. at high angles to most regional mapped structures and sub-province boundaries) with little to no surface
expression that are spatially associated with lode ('orogenic') Au and Ni-Cu-PGE-Cr occurrences. Statistical and machine learning analysis of the Red Lake-Stormy Lake region in the W Superior Province confirms visual inspection for a greater
correlation between Au deposits and these deep N-S structures than with mapped surface to upper crustal, generally E-W trending, faults and shear zones. Porphyry Au, Ni, Mo and U-Th showings are also located above these deep transverse
faults.
Several well defined concentric circular to elliptical structures identified in the Oxford Stull and Island Lake domains along the S boundary of the N Superior proto-craton, intersected by N- to NNW striking extensional fractures and/or
faults that transect the W Superior Province, again with little to no direct surface or upper crustal expression, are spatially associated with magmatic Ni-Cu-PGE-Cr and related mineralization and Au occurrences. The McFaulds Lake greenstone belt,
aka. 'Ring of Fire', constitutes only a small, crescent-shaped belt within one of these concentric features above which 2736-2733 Ma mafic-ultramafic intrusions bodies were intruded. The Big Trout Lake igneous complex that hosts Cr-Pt-Pd-Rh
mineralization west of the Ring of Fire lies within a smaller concentrically ringed feature at depth and, near the Ontario-Manitoba border, the Lingman Lake Au deposit, numerous Au occurrences and minor Ni showings, are similarly located on
concentric structures. Preliminary magnetotelluric (MT) interpretations suggest that these concentric structures appear to also have an expression in the subcontinental lithospheric mantle (SCLM) and that lithospheric mantle resistivity features
trend N-S as well as E-W. With diameters between ca. 90 km to 185 km, elliptical structures are similar in size and internal geometry to coronae on Venus which geomorphological, radar, and gravity interpretations suggest formed above mantle
upwellings. Emplacement of mafic-ultramafic bodies hosting Ni-Cr-PGE mineralization along these ringlike structures at their intersection with coeval deep transverse, ca. N-S faults (viz. phi structures), along with their location along the margin to
the N Superior proto-craton, are consistent with secondary mantle upwellings portrayed in numerical models of a mantle plume beneath a craton with a deep lithospheric keel within a regional N-S compressional regime. Early, regional ca. N-S faults in
the W Superior were reactivated as dilatational antithetic (secondary Riedel/R') sinistral shears during dextral transpression and as extensional fractures and/or normal faults during N-S shortening. The Kapuskasing structural zone or uplift likely
represents Proterozoic reactivation of a similar deep transverse structure.
Preservation of discrete faults in the deep crust beneath zones of distributed Neoarchean dextral transcurrent to transpressional shear zones in the present-day upper
crust suggests a 'millefeuille' lithospheric strength profile, with competent SCLM, mid- to deep, and upper crustal layers. Mechanically strong deep crustal felsic and mafic granulite layers are attributed to dehydration and melt extraction.
Intra-crustal decoupling along a ductile décollement in the W Superior led to the preservation of early-formed deep structures that acted as conduits for magma transport into the overlying crust and focussed hydrothermal fluid flow during regional
deformation. Increase in the thickness of semi-brittle layers in the lower crust during regional metamorphism would result in an increase in fracturing and faulting in the lower crust, facilitating hydrothermal and carbonic fluid flow in pathways
linking SCLM to the upper crust, a factor explaining the late timing for most orogenic Au.
Results provide an important new dataset for regional prospectively mapping, especially with machine learning, and exploration targeting for Au and
Ni-Cr-Cu-PGE mineralization. Results also furnish evidence for parautochthonous development of the S Superior Province during plume-related rifting and cannot be explained by conventional subduction and arc-accretion models. |
| Sommaire | (Résumé en langage clair et simple, non publié)
L'Initiative des géosciences ciblées (IGC) est un programme fédéral collaboratif. Ce programme fournit à l'industrie ce qui est requis pour la
prochaine génération des connaissances géoscientifiques et des techniques novatrices. Le résultat est l'identification des dépôts de minéraux en profondeur. Ce compendium est le résultat des récipiendaires des subventions d'IGC 2018-2020. |
| GEOSCAN ID | 328984 |
|
|