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TitreThe Cambro-Ordovician Cu-Au Ming VMS deposit, Baie Verte peninsula, Newfoundland: geological environment, ore zone architecture, and hydrothermal alteration
AuteurPilote, J -L; Piercey, S J; Mercier-Langevin, P; Pilgrim, L; Legrow, P
SourceL'Association géologique du Canada-L'Association minéralogique du Canada, Réunion annuelle conjointe, Recueil des résumés vol. 37, 2014 p. 225
LiensOnline - En ligne
Séries alt.Secteur des sciences de la Terre, Contribution externe 20130551
RéunionGAC-MAC 2014; Joint annual meeting of Geological Association of Canada and Mineralogical Association of Canada; Fredericton; CA; mai 21-23, 2014
Documentpublication en série
Lat/Long OENS-56.1397 -56.0217 49.9317 49.8658
Sujetsaltération; altération hydrothermale; analyses stratigraphiques; corrélations stratigraphiques; gîtes minéralogiques; gisements minéraux; minéralisation; cuivre; or; zinc; gîtes volcanogènes; sulfures; gîtes sulfureux; déformation; Groupe de Pacquet Harbour ; géologie économique; stratigraphie; Paléozoïque; Ordovicien; Cambrien
ProgrammeÉtude des gîtes de sulfures massifs volcaniques, Initiative géoscientifique ciblée (IGC-4)
Résumé(disponible en anglais seulement)
The producing Cu-Au Ming volcanogenic massive sulphide (VMS) deposit is part of the Cambro-Ordovician Baie Verte Belt, host to numerous past producing Cu and Cu-Au VMS deposits. The Ming deposit (reserves of 1.50 Mt at 1.62 wt% Cu, 2.40 g/t Au, 10.90 g/t Ag, and 0.49 wt% Zn and resources estimated at 3.65 Mt at 2.26 wt% Cu, 1.13 g/t Au, 6.78 g/t Ag, and 0.32 wt% Zn) contains four elongated Cu-Au-Zn±Ag massive to semi-massive sulphide lenses, all gently plunging northeast and separated 30 to 50 metres from each other along the same stratigraphic horizon. The lenses are hosted by intermediate to felsic volcanic and volcaniclastic rocks of the Early Ordovician (ca. 487 Ma) Pacquet Harbour Group, which is part of a regional mafic-dominated rock assemblage of boninitic to tholeiitic affinity. Preliminary field observations and lithogeochemical results indicate that the footwall is composed of at least three distinct intermediate to felsic calk-alkaline (e.g. Zr/Y>7) volcanic and volcaniclastic units. The immediate hanging wall is lithologically heterogeneous, varying from a highly silicified (SiO2>88 wt%) volcaniclastic rock to a magnetite-rich volcanogenic siltstone. Locally, the mafic-dominated subaqueous, syn-obduction ophiolite cover sequence is in structural contact with the massive-sulphide as a result of post-mineralization deformation. Three generations of mafic to intermediate sills and dykes are present in the deposit and have distinctive lithogeochemical signatures; they are interpreted to be genetically related to the mafic rocks of the ophiolitic cover sequence. The Ming deposit has distinct alteration mineral assemblages including sericite, chlorite, quartz, biotite, tremolite, Mn-Ca-rich garnet and calcite, green mica, epidote, magnetite, and pyrite. A Cu-rich zone consisting primarily of chalcopyrite, pyrrhotite, and pyrite with minor Bi- Te sulfosalts and sphalerite in a strongly chlorite-epidote altered felsic volcanic rock occurs 50 to 100 metres below the main sulphide lens, representing the high-temperature discharge zone of the Ming hydrothermal system. An overprint of metamorphic biotite is ubiquitous throughout the felsic footwall rocks and represents metamorphosed K-Fe-(Mg) alteration to upper greenschist facies. The relationship between the stratigraphy, spatial distribution and styles of alteration, and the mineralization strongly favor a syngenetic origin for the ore zones. Despite local chemical and mechanical remobilization of the massive sulphide in the westernmost zone (1807 zone) due to subsequent deformation events (i.e. Taconic, Salinic, and Acadian orogeneses), the sulphide bulk composition for all zones, including the precious metals, has not been changed by deformation and metamorphism, suggesting intrinsically enriched VMS ore-forming fluids.