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TitleSynvolcanic Au-Cu ± Ag-Zn-Pb massive sulphides, veins and disseminations of the Westwood deposit, Abitibi greenstone belt, Quebec
AuthorYergeau, D; Mercier-Langevin, P; Dubé, B; Malo, M; Bernier, C; Savoie, A; Simard, P
SourceGeological Association of Canada-Mineralogical Association of Canada, Joint Annual Meeting, Programs with Abstracts vol. 36, 2013 p. 201
LinksOnline - En ligne
Alt SeriesEarth Sciences Sector, Contribution Series 20130548
MeetingGAC-MAC 2013; Joint annual meeting of Geological Association of Canada and Mineralogical Association of Canada; Winnipeg; CA; May 22-24, 2013
File formatpdf
AreaDoyon; Bousquet; LaRonde; Abitibi
Lat/Long WENS-78.5000 -78.0000 48.2500 48.0000
Subjectseconomic geology; mineralogy; mineral deposits; mineralization; mineral occurrences; gold; silver; copper; zinc; lead; sulphides; sulphide deposits; alteration; hydrothermal alteration; Doyon-Bousquet-LaRonde mining camp; Westwood Deposit; Abitibi Greenstone Belt; Bousquet Formation
ProgramTargeted Geoscience Initiative (TGI-4), Gold Ore Systems
AbstractThe Westwood deposit (3.715 Moz of gold) includes three distinctive mineralized corridors stacked from north to south: 1) Zone 2 Extension, 2) North Corridor and 3) Westwood Corridor. The Zone 2 Extension consists of cm- to dm-wide pyrite- and chalcopyrite-rich quartz veins and dissemination zones whereas the North Corridor consists of cm- to dm-wide quartz-pyrite-chalcopyrite ± sphalerite veins and disseminations as well as thin, semi-massive to massive sulphide veins. The envelopes of these two corridors are slightly discordant to the stratigraphy and main foliation. Finally, the Westwood Corridor consists of discontinuous stratabound polymetallic semi-massive to massive sulphide lenses, veins and disseminations. The Westwood mineralized corridors are part of the Doyon- Bousquet-LaRonde mining camp and are hosted in metavolcanic rocks of the Bousquet Formation (2699-2696 My), which forms a steeply south-dipping, east-trending homoclinal sequence facing south. The study area is metamorphosed to greenschist-amphibolite facies transition and deformation is heterogeneous with high strain corridors localized typically at lithological contacts and within synvolcanic alteration zones. The Warrenmac massive sulphide lens (Westwood Corridor) is characterized by pyrite-sphalerite-chalcopyrite ± galena-pyrrhotite and is overlain by a highly transposed stringer zone, which are both anomalous in Sn, Hg, As and Sb. Sericite, quartz, biotite, chlorite and Mn-garnet define the metamorphosed proximal alteration assemblage whereas an aluminous alteration assemblage (staurolite, andalusite, kyanite) is preferentially developed at depth (> 1.5 km). Mapping of the Warrenmac discovery outcrop revealed that volcaniclastic felsic rocks hosting the massive sulphide lens are intruded by lowpermeability mafic sills which acted as cap rocks for ascending hydrothermal fluids. Moreover, synvolcanic alterations discordant and strongly transposed into the main foliation combined with the presence of abundant sulphide fragments within felsic volcaniclastic breccias confirm the synvolcanic origin of mineralization. Zone 2 Extension and Doyon mine mineralization (~1.5 km west of Westwood) are interpreted to be genetically related to the synvolcanic Mooshla pluton whereas Westwood and North corridors have a VMS-type origin and are located on the same stratigraphic horizon as LaRonde Penna mine 20 North lens to the east. U/Pb dating suggest that the three mineralized corridors might have been formed in less than 2 My. The Westwood deposit therefore represents a unique opportunity to test the hypothesis of a continuum between vein-type mineralization associated with a synvolcanic intrusion and auriferous massive sulphide lenses, and thereby contribute to a better understanding of Archean auriferous magmatic-hydrothermal systems. Metallogenic continuums are well documented in younger geological environments such as telescoped porphyry-epithermal systems.