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TitleGeochemical investigations of high-grade quartz-scheelite veins of the Cantung Mine, Northwest Territories
DownloadFree download (whole publication) (zip 1728917 KB)
AuthorYuvan, J; Shelton, K; Falck, H
SourceMineral and energy resource assessment of the Greater Nahanni Ecosystem under consideration for the expansion of the Nahanni National Park Reserve, Northwest Territories; by Wright, D F (ed.); Lemkow, D (ed.); Harris, J R (ed.); Geological Survey of Canada, Open File 5344, 2007 p. 177-190; 1 DVD, https://doi.org/10.4095/224553
Year2007
Documentopen file
Lang.English
MediaDVD
RelatedThis publication is contained in Wright, D F; Lemkow, D; Harris, J R; (2007). Mineral and energy resource assessment of the Greater Nahanni Ecosystem under consideration for the expansion of the Nahanni National Park Reserve, Northwest Territories, Geological Survey of Canada, Open File 5344
ProvinceNorthwest Territories
NTS95E/13; 95L/04; 105H/16; 105I/01
AreaNahanni National Park; Nahanni River; Tungsten
Lat/Long WENS-128.5000 -127.5000 62.2500 61.7500
Subjectsgeochemistry; economic geology; bedrock geology; mineralization; mineral occurrences; geochemical surveys; geochemical analyses; quartz; scheelite; veins; vein deposits; hydrothermal deposits; hydrothermal systems; skarn deposits; hydrothermal alteration; alteration; trace element geochemistry; oxygen isotopes; fluid inclusions; Greater Nahanni Ecosystem; Windermere Supergroup; Cantung Mine; sedimentary exhalative deposits; Cambrian
Illustrationssketch maps; rose diagrams; tables; photographs; plots; photomicrographs
Viewing
Location
 
Natural Resources Canada Library - Ottawa (Earth Sciences)
 
Natural Resources Canada library - Calgary (Earth Sciences)
 
Geological Survey of Canada (Atlantic)
 
Natural Resources Canada library - Vancouver (Earth Sciences)
 
Natural Resources Canada library - Québec (Earth Sciences)
 
ProgramMineral and Energy Resource Assessment (MERA)
Released2007 11 19
AbstractHigh-grade quartz-scheelite veins (up to 3.7 wt.% WO3) in the open pit orebody of the Cantung mine, Tungsten, Northwest Territories occur 300 m vertically above a Cambrian limestone-Cretaceous monzogranite contact along which the E-Zone, a world-class tungsten skarn orebody, is developed. The trend of an 80 m wide vein swarm is roughly parallel to the strike and dip of a near-vertical aplite dyke along the edge of the open pit. Adjacent to these quartz-scheelite veins, dark green alteration selvedges overprint earlier light green skarn alteration. This overprint implies that the high-grade quartz-scheelite veins are not part of the early skarn-forming event but represent a distinct, later event.

Oxygen isotope data from vein-hosted quartz-scheelite pairs yield equilibrium depositional temperatures of 430 to 595°C. These temperatures indicate that the high-grade quartz-scheelite veins are related to a deep magmatic hydrothermal system and are likely a distal expression of a protracted skarn-forming event, perhaps related to aplite dyke emplacement. Quartz-scheelite veins did not form in a shallower, cooler, hydrothermal system during uplift.

Primary ore fluids in quartz-scheelite veins from the open pit orebody, in skarn-related quartz veins from the E-Zone orebody, and in aplite dykes are grossly similar H2O-CO2-NaCl ± CH4 fluids. However, two distinct end-member fluids have been documented: aplite-related fluids and skarn-related fluids (in quartz veins from the E-Zone orebody). Fluids in high-grade quartz-scheelite veins contain components of both end-member fluids. High-grade quartz-scheelite veins from the open pit orebody share a common structural attitude with aplite dykes. Fluids in veins from the open pit orebody contain an aplite-related fluid end-member even when occurring up to 70 m from the nearest exposed aplite dyke. Thus, quartz-scheelite veins and aplite dykes in the open pit orebody probably have a genetic relationship in addition to their structural relationship.

The authors envision a conceptual model for the Cantung hydrothermal system in which ore-grade tungsten deposits formed where fluids emerged from the granite and encountered rocks favourable for skarn development (e.g. cleaner 'ore limestone' versus cherty 'swiss cheese limestone'). Due to the folded geometry of the sedimentary sequence, in other areas along the granite contact, the fluids emerging from the granite encountered strata less favourable to skarn development (i.e. argillite). Where these less favourable units were breached by fracture systems, potential skarn-forming fluids (and aplite dykes) gained access to host rocks more conducive to ore development vertically distal to the granite contact. The presence of magmatic ore fluids distal to intrusions is intriguing and has significant implications for mineral resource assessment in the region.
GEOSCAN ID224553